240 — 9 December 2012 Editor: Bo Reipurth (Reipurth@Ifa.Hawaii.Edu)

Home , KH 15D, Maarten Schmidt

THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar/planetary evolution and molecular clouds

No. 240 — 9 December 2012 Editor: Bo Reipurth ([email protected])

1 List of Contents

The Star Formation Newsletter Editorial ...... 3 Interview ...... 4 Editor: Bo Reipurth [email protected] My Favorite Object ...... 6

Technical Editor: Eli Bressert Perspective ...... 10 [email protected] Abstracts of Newly Accepted Papers ...... 13 Technical Assistant: Hsi-Wei Yen Abstracts of Newly Accepted Major Reviews . 50 [email protected] Dissertation Abstracts ...... 52

Editorial Board New Jobs ...... 54 New and Upcoming Meetings ...... 57 Joao Alves Alan Boss New Books ...... 59 Jerome Bouvier Short Announcements ...... 61 Lee Hartmann Thomas Henning Paul Ho Jes Jorgensen Charles J. Lada Cover Picture Thijs Kouwenhoven Michael R. Meyer The L1630, or Orion-B, cloud is located just above Luis Felipe Rodr´ıguez the Orion Belt stars. The northern part, seen here, Ewine van Dishoeck hosts the two bright reflection nebula NGC 2068 Hans Zinnecker and 2071, as well as a rich population of young low- mass stars. At a distance of only about 400 pc, the The Star Formation Newsletter is a vehicle for L1630 cloud permits detailed studies of individual fast distribution of information of interest for as- objects. Prominent in the dense and highly struc- tronomers working on star and planet formation tured cloud in the southern part of the image is the and molecular clouds. You can submit material HH 24 complex, harboring half a dozen outflows, as for the following sections: Abstracts of recently well as numerous other Herbig-Haro objects. Near accepted papers (only for papers sent to refereed the center of the image one sees the bright compact journals), Abstracts of recently accepted major re- reflection nebula known as McNeil’s Nebula, illu- views (not standard conference contributions), Dis- minated by the FUor event in V1647 Ori that took sertation Abstracts (presenting abstracts of new place in late 2003. Ph.D dissertations), Meetings (announcing meetings broadly of interest to the star and planet for- Image courtesy Ignacio de la Cueva Torregrosa mation and early solar system community), New Jobs (advertising jobs specifically aimed towards persons within the areas of the Newsletter), and Short Announcements (where you can inform or re- quest information from the community). Addition- Submitting your abstracts ally, the Newsletter brings short overview articles on objects of special interest, physical processes or Latex macros for submitting abstracts theoretical results, the early solar system, as well and dissertation abstracts (by e-mail to as occasional interviews. [email protected]) are appended to each Call for Abstracts. You can also Newsletter Archive submit via the Newsletter web inter- www.ifa.hawaii.edu/users/reipurth/newsletter.htm face at http://www2.ifa.hawaii.edu/star- formation/index.cfm

2 Editorial

This issue is no. 240, and with it we can celebrate 20 years of publication of the Star Formation Newsletter. Twenty years ago the world looked different, as we were only at the beginning of the information age and, especially for young people, it may be difficult to understand that information was not so easy to get hold of as it is today. At that time many institutes still printed preprints and mailed them to other institutes. The process of publishing a paper was much slower, and people actually went to the library and (gasp) read the journals as they came in. It was in that environment that the Star Formation Newsletter was launched as the first electronic newsletter in astronomy. This soon led to more such newsletters being circulated, most of which unfortunately had short lives, although some still exist. The Star Formation Newsletter thus filled a clear need for rapid dissemination of abstracts of new papers, as well as other information of interest to the star formation community, like dissertation abstracts, announcement of meetings and new jobs, and the occasional book review. Today, twenty years later, the need for the Star Formation Newsletter is not so obvious. We are now connected to the internet 24 hours a day, and in a sense we have the opposite problem of trying to keep the avalanche of information at bay. The limiting factor today is to find only the information that we need, and to find time to digest that information. Electronic preprint servers, especially arXiv, now offer a daily dosis of new papers with the latest results, and this has changed the way we work. It has also been a great democratic force, since to get the latest news it no longer matters if a researcher or student is working in USA or Uganda. With this in mind I therefore felt that it was time to close the Star Formation Newsletter. However, whenever I mentioned this to colleagues, I was always met with a ’Please don’t do that’. A lot of people have responsibilities that do not allow them time to browse around for potentially interesting information, and instead they take time once a month to look at the Newsletter to review the state of the field. Since the option of just continuing the Newsletter in its present form was not really meaningful, and after some soul-searching, I decided to upgrade the Newsletter, taking advantage of the developments in technology over the past twenty years. Hence you now see here an issue of the Newsletter that has color pictures, and hyperlinked URLs after the abstracts. And I have also introduced interviews as well as small articles (My Favorite Object and Perspective), which give an expert’s view on a given object or subject. These were inspired by the fact that in recent years the growth in subscribers to the Newsletter has been almost exclusively among students and postdocs. This is because, with about 1300 subscribers, almost everybody in the star formation community gets the Newsletter, and the only growth is among the new generation of researchers. It has always been a puzzle to me that I only receive about 50% of the abstracts of relevant papers. Given that we all publish to be read, it seems logical that after spending many months to prepare research results for publication one should also spend 5 minutes to circulate an abstract to potential readers. I therefore urge readers to submit their abstracts in the spirit of a shared community. If we all do this, we all can benefit from a near-complete monthly compilation. The Newsletter is a creation of the star formation community for the star formation community. With a new Technical Editor, Eli Bressert, and a new Technical Assistant, Hsi-Wei Yen, we have started along two paths for the Newsletter. Eli is working on software that will automatically extract abstracts from the journals as papers appear in electronic form. This will take some time, and meanwhile Hsi-Wei is helping me to extract missing abstracts from astro-ph. Until the software is in place, please continue to submit your abstracts. The focus of the Newsletter will remain towards Galactic star formation; abstracts on extragalactic star formation will only be brought if they deal with studies in the Magellanic Clouds and the very nearest Local Group galaxies. We will no longer bring abstracts on the more tenuous interstellar medium, except when directly relevant to star formation. We are now seeing a lot more studies of planet formation, making this one of the most vibrant areas at the moment and reflecting the changes that our field has undergone in the past twenty years. Bo Reipurth

3 with an approximation that seemed adequate, and it did the job and allowed me to calculate all the way through to Richard B. Larson a pre-main sequence star on the Hayashi track. After this in conversation with Hans Zinnecker work was published my treatment of the accretion shock was controversial, but eventually more detailed treatments showed that it had not introduced a serious error. Q: What do you think were the key findings of this work? A: Looking back, I think that the most important result of that work might have been the very first one that I found when I got my first collapse code working. I had written a simple code to calculate isothermal collapse, and the first successful run with it showed the runaway growth of a sharp central peak in density that appeared to be approaching a singularity. This result was not what anyone had expected, and it was also to prove controversial, but I eventually convinced myself that it was at least qualita- tively correct and found a similarity solution showing this behavior. At about the same time, Michael Penston found Q: Your 1968 dissertation was entitled “Dynamics of a similar results and independently derived the same simi- Collapsing Protostar”, and it was a pioneering study. What larity solution. This ‘Larson-Penston solution’, as it has led you to do a thesis on that topic, and what was the in- been called, was perhaps the most enduring result of that fluence of your thesis advisor, Guido Münch? early work, and it has been shown to have much greater A: As an undergraduate at the University of Toronto I generality. This basic qualitative result led to a change first became interested in astronomy, like many students, in thinking about star formation by showing that star for philosophical reasons: I wanted to know the answers to formation begins with the runaway formation of a near- the big questions about the universe, and I realized that I singularity in density, and then continues as an accretion would have to learn some astronomy to answer them. As process. Once you adopt the view that star formation is a graduate student at Caltech I was fascinated by galaxies largely an accretion process, you can calculate many things and wanted to understand how they formed. My first idea about it by studying how the accretion process works. for a thesis project was to calculate how a spherical galaxy Q: You were among the first to suggest that most, if not forms, using a simple treatment of star formation. When all, stars are born in small multiple systems. How do you I discussed this idea with Maarten Schmidt, he seemed see that subject today, and how important is it to our un- dubious about it as a thesis project and suggested that I derstanding of star formation? talk with Guido Münch, who knew more about interstellar matter and star formation. Guido was also skeptical A: Binary and multiple systems are clearly the normal way about my grandiose ideas, and he said “before you try that nature makes stars, and most single stars are prob- to understand how a galaxy forms, why don’t you try to ably escapers from such systems. From a general point understand how one star forms?” I quickly realized that of view this is completely unsurprising because nature is Guido was right and that this would be a better thesis complex, and star-forming clouds in particular are highly topic, although still challenging. But I decided to give it a complex and have structure and motions on all scales. try because I had already read nearly everything that had This has major implications for our understanding of star been written about star formation (which was not so much and planet formation because it means that most stars in those days), and I had also gained some experience in form in close proximity to other stars, and therefore that calculating stellar structure working with Pierre Demar- interactions will almost certainly play an important role que in Toronto. So I plunged into the project, not having in their formation. Our Sun and Solar System may not be any idea how far I would get with it. Guido again provided typical, and indeed recent studies have found an enormous crucial advice at a later stage when I realized that I would diversity in extra-solar planetary systems. The fact that have to deal with an accretion shock at the surface of the star-forming clouds quickly become highly structured on stellar core, and I proposed to include a treatment of ra- all scales, probably because of both turbulence and self- diative transfer in the vicinity of the shock. Guido said gravity, means that their dynamics must necessarily be “no, don’t waste your time with that, try using a simple highly chaotic. To me this is a lesson that we as theo- approximation”, and this gave me the idea that I should rists have to respect the diversity and complexity and un- try to find a simple approximation that would allow me to predictability of nature and be very cautious in applying continue my protostar calculation. I eventually came up simple theoretical models.

4 Q: Thirty years ago you suggested the existence of scaling properties and origin of the stellar Initial Mass Function. relations for molecular clouds linking velocity dispersion What is your current view of this subject? and density with size. What is your current view of these A: I have been interested in the stellar IMF from the be- “Larson relations”? ginning of my career because I was always surrounded by A: There are real trends like the ones I discussed, but it people who wanted me to explain the IMF. So I made a has to be kept in mind that they are only broad correla- number of attempts over the years based on various ideas, tions with a lot of scatter, and that different studies can and I have tried to keep up with the observational status find different results. These relations have been endlessly of the subject. The main thing I have learned after all debated and I think they have often been overinterpreted. these years is that when looked at in any detail, this sub- What is clear is that the internal motions in molecular ject is a can of worms. In general terms, we know that clouds are very complex and that they are at least in part for massive stars the IMF looks something like a power hierarchically structured like turbulence. But these facts law, perhaps not too different from that originally pro- are not diagnostic of any particular origin for these mo- posed by Salpeter, and that at the low end the IMF shows tions, or of any particular mechanism for sustaining them. a turnover below one solar mass. Whether any feature of Even the basic energy source is still debated, sometimes the IMF is universal has been debated inconclusively for heatedly. Probably all of the suggested mechanisms con- decades, and the subject has a long history of claims that tribute at some level. The main implication of all this didn’t stand the test of time. On the observational side, for star formation is that the initial conditions for it are it is clear that sample definition is of critical importance, likely to be characterized by chaotic supersonic motions on but in the end arbitrary choices always have to be made a range of scales, and therefore that idealized models may about what to include in the sample. Theorists then have not be relevant. But once gravity takes over, as it must to be careful to theorize about what the observers actually eventually if stars are to form, gravitational dynamics be- observed if they want their work to be relevant. Observers comes increasingly dominant and develops characteristics have learned from hard experience to pay careful attention of its own that become independent of the initial condi- to sample selection, but theory isn’t there yet. Concern- tions. For example, the properties of binary and multiple ing the physics behind the IMF, I have found appealing systems, and perhaps even planetary systems, may depend the idea that the low-mass turnover is determined by fun- more on the universal properties of gravitational dynamics damental atomic physics through the thermal properties than on the initial state of star forming clouds. of star-forming clouds. It seems clear that the thermal Q: Ten years ago you wrote an influential paper on “The physics is indeed important, but other effects can also be Role of Tidal Interactions in Star Formation”. What were important, and we don’t yet have a full understanding of your key points? the origin of the IMF and can’t yet make the predictions that observers would like us to make, for example how A: I had earlier suggested that gravitational torques in the IMF might vary in different circumstances. What’s disks are likely to play an important role in star forma- needed is big simulations that include as much of the rel- tion, and in the paper you mention I suggested that tidal evant physics as possible, but this is difficult work. interactions between stars and disks in a system of forming stars could also be important for redistributing angular Q: Computational star formation has made amazing strides momentum and thus helping to solve the angular momen- since you began your work almost 50 years ago. What do tum problem. Recent detailed simulations of star forma- you see as the main challenges today, and where do you tion do indeed show strong gravitational interactions be- think this field is heading? tween stars and disks, sometimes to the extent that disks A: See above for some of the challenges. I don’t want are completely disrupted. What seems clear is that gravity to predict where this field is heading, but continuing ad- must often be an important player in the dynamics of disks vances in hardware and software will surely continue to and in the redistribution of angular momentum. Mag- make bigger and better calculations possible. I hope that netic and thermal pressure forces can be equally impor- enterprising young people will continue to push ahead with tant, and many interesting phenomena probably involve a such calculations. But it will require a large effort and complex interplay of forces. But non-radial gravitational expertise in a range of areas of astrophysics and compu- forces alone can already go a long way toward solving the tation, and big projects will have to be organized. I hope classical ‘angular momentum problem’, in which case this I live to see many more advances, but I wouldn’t attempt problem can be seen as being at least in part just an arti- to predict what they will be. It will be an adventure to fact of oversimplified models. This is another case of the find out. complexity of nature not being fully appreciated in early Q: What are you planning to do in your retirement? work. A: Less astronomy and more of everything else. Q: You have also been interested for a long time in the

5 could cause such bizarre behavior. Another Wesleyan student, Catrina Hamilton, took up the work as part of her My Favorite Object Physics Ph.D. thesis. We learned that the star showed KH 15D: little, if any, change in spectral class when in eclipse and The Gift that Keeps on Giving that the duration and depth of the eclipses continued to grow, from ∼3 mag and 16 days in 1996 to ∼3.5 mag and William Herbst 20 days by 2002. Low resolution spectra revealed the star at maximum brightness as a K7 dwarf or sub-giant with strong Li I absorption and weak Hα emission – an ordinary weak-line T Tauri star. The only dramatic spectral change during eclipse was an increase in equivalent width of the Hα emission from 2 A˚ to 30-50 A,˚ and a strengthening of the [OI] and [SII] lines coming from a weak jet. The star was evidently a low mass (∼0.5 M⊙), pre-main sequence member of NGC 2264 that was still weakly accreting and being eclipsed on a 48.37 d period by something much larger than a companion star, and possibly growing by the year! The only interpretation that made any sense to us was that the eclipsing object was part of the circumstellar disk that must still be present to account for the accretion and jet activity. In 1995, during a time domain study of the young cluster Its uniqueness and potential importance to star and planet NGC 2264 with a small telescope on the campus of Wes- formation gained KH 15D some visibility at conferences leyan University, my student Kristin Kearns and I discov- and with the press. A New York Times article was re- ered a variable star with unique and puzzling behavior. It portedly the spur for some work by astronomers outside was strictly periodic on a 48.37 d cycle, much longer than our little group at Wesleyan. Various theories were pro- the rotation period of a typical T Tauri star, and had posed, including the formation of an anti-cyclonic vortex an amplitude of several magnitudes, much larger than is of grains in a circumstellar disk that could remain stable normally seen for young stars. It appeared to be under- for many rotations and possibly function as the eclips- going regular eclipses, but in the middle of each eclipse ing body (Barge & Viton 2003). Agol et al. (2004) pro- it would briefly return to near full brightness or, in one posed that the star was surrounded by a warped disk or- case, above full brightness and then quickly fade back to biting as a solid body and that the periodic passage of the minimum light. We described the behavior in a couple warp across our line of sight was responsible for the eclipse of paragraphs buried in a paper on the rotation proper- behavior. The landscape changed dramatically, however, ties of the cluster stars (Kerans & Herbst 1998). Later with the predictions (independently and roughly simulta- investigations Winn et al. 2003, Johnson & Winn 2004, neously) by Chiang & Murray-Clay (2004) and Winn et Maffei, Ciprini & Tosti 2005) would show that the star, al. (2004) that KH 15D was a binary system. This was which had first been noticed as a variable by Badalian & quickly confirmed by a Keck/HIRES radial velocity study Erastova (1970) and given the variable star designation (Johnson et al. 2004). The 48.37 d period was recognized V582 Mon, appeared generally brighter and significantly as the orbital period of the binary, which was believed to less variable during the 1960’s through early1980’s, with consist of two rather similar stars in a fairly eccentric (e ∼ no evidence of eclipse behavior. An unfortunate gap in the 0.6) orbit. While in this version of the story it is the stars historic record from 1982 to 1995, caused by the phase-out that orbit, not a feature in a circumstellar disk around a of photographic plate-based surveys, makes it uncertain as single star, it is still nonetheless the disk that is responsi- to exactly when the deep eclipse phase began. ble for the eclipses. More precisely, we should say that the As we continued to monitor the star at Van Vleck Ob- occulting body is an inner, dynamically-independent ring, servatory during the subsequent seasons its behavior be- within the accretion disk. The main difference is that in came ever more intriguing. The duration of the eclipse the binary model, the occulting feature is at much larger phase continued to grow and the brightness turnaround distances from the star(s), roughly 1-5 AU, rather than near mid-eclipse became smaller and smaller. Few stars near 0.1 AU, as implied by a 48.37 d period. In the binary have light curves that evolve in such steady, secular fash- model, there is also a natural mechanism to explain the ion and none had ever shown the particular characteristics steady, secular evolution of the light curve over years and of this enigmatic object. The first phase of intense work on decades, namely precession of the warped circumbinary the star began, aimed at unraveling the mystery of what disk.

6 some future time and the eclipses would begin again. How long that might take – years, decades, centuries – was any- body’s guess in 2006. With a basic model in hand, the next phase of study focused on exploiting this very lucky geometry to learn as much as possible about the stars, their magnetospheres, the inner jet, and the circumbinary ring. Numerous studies were launched, employing high resolution spectroscopy at Keck/HIRES, VLT/UVES, Magellan/MIKE and other facilities as well as continual ground-based photometric monitoring, and episodic observations from space employing HST, Spitzer and Chandra. The photometric data revealed that the rotation period of the visible component of the system was 9.6 d, slow for a star of this mass and age (Hamilton et al. (2005). A Chandra study showed that the system is also a weaker than expected X-ray source, possibly because of its slower rotation (Herbst & Moran 2006). It is possible that the star’s rotation has become pseudo-synchronized with the orbital period, as tidal the- Figure 1: Schematic diagram from Winn et al. (2006) ory in a binary system such as this would predict (Hut showing how the light curve of KH 15D is produced at 1981). The awesome complexity of the magnetosphere and one epoch in the mid-2000’s by a binary system in which a inner jet-launching regions were probed by what we called razor sharp occulting edge divides the orbits into occulted “natural coronagraphy” – the technique of using the ra- and non-occulted parts. Even when the photospheres of zor sharp and highly opaque edge of the occulting ring to both stars are fully occulted we do see light from the sys- progressively eliminate or reveal during each cycle vari- tem reaching us by scattering. One possibility, that the ous parts of the stellar surface and extended atmospheres. scattering arises in a halo around each star, is shown in Results from these studies are presented in several papers, this ﬁgure, although other possibilities exist. including Mundt et al. (2010) and Hamilton et al. (2012). Among other things they show that the jet is launched This early phase of study culminated in a comprehensive not by one of the stars alone but by the combined action phenomenological model produced by Winn et al. (2006) of both stars, possibly during periastron passage. We also that accounted for all of the photometric and radial veloc- found evidence for enhanced accretion – “pulsed accre- ity data available at the time. In Fig. 1, we reproduce a tion” – that occurs during or just after periastron passage diagram from that paper illustrating how the light curve is as predicted by some theories. Finally, there is spectro- understood at one epoch. The secular variation with time scopic evidence for gas streams crossing the largely evacu- comes from the slow march of the occulting edge across ated inner hole of the CB ring, feeding the accretion onto the projected orbits, driven by precession of the disk. Ex- one or both of the stars, again as some models, e.g. de actly how to envision this model in 3d remained a bit elu- Val-Borro et al. (2011), predict. sive, since the width of the opaque part of the occulting Studies of the ring itself have also been illuminating. The screen was unknown and its location within the circumbi- light and color curves can be used to infer the transparency nary ring (i.e. at the inner edge, outer edge, or in the mid- of the ring edge as a function of wavelength. Remark- dle) was also unknown. Dynamical arguments by Chiang ably, each eclipse is well modeled by a razor sharp edge & Murray-Clay (2004) suggested that the occulting ring’s with no transparency whatsoever at optical or even near- center was near 3 AU and that it had a width of 1-2 AU. IR wavelengths (Herbst et al. 2010). Furthermore, we The precession time scale in their model is around 1000 could ﬁnd no evidence of a concentration of gas towards yrs. To precess as a single unit the disk must be warped the ring plane in an analysis of the Na I feature (Lawler and there must be communication between the various an- et al. 2010). Grain size estimates from polarization and nuli of the ring through either pressure forces from associ- scattering properties indicate that substantial growth has ated gas or the self-gravity of ring particles. This model of occurred (Agol et al. 2004, Herbst et al. 2008). Without the system, an eccentric binary situated within a warped, such growth it would indeed be hard to understand how precessing ring, leads to the prediction that, eventually, the ring solids could have settled within the gaseous disk the star causing the eclipse behavior in 2006 would itself to form such a sharp-edged structure. A picture emerges be fully occulted, while the other star should reappear at of a physically thin ring of solids spanning the terrestrial

7 planet formation zone around a close binary. It has long non-occulted star (see Fig. 1) is fully visible. The one data been thought (Goldreich & Ward 1973; Chiang & Youdin point lying above that level was obtained in 1995, on our 2010) that such structures are a likely first stage in the for- third night of observation of the system, and represented mation of km-sized planetesimals. It is interesting that, so (until recently) the only detection in the modern data set far, there is no indication of this ring in any other observed of the other star. Most likely, both stars were visible at the characteristic of KH 15D. If we were viewing this system time of this observation. It is interesting that, even when from almost any other direction in space or almost any both stellar photospheres are fully occulted, the system other time we would not know that this ring was present. continues to vary on the orbital period of 48.37 d, and If it is a first step in planetesimal formation and if plan- by a substantial amount. The amount of scattered light ets are a common feature of all stars, even binaries, then reaching us is highly modulated by the orbit. The details such rings may also be expected to be common. What we of the scattering remain uncertain. One possibility is that have come to recognize about KH 15D is that its unusual each star has a scattered light halo, as depicted in Fig. 1. properties arise only because we see it at a very fortunate Other possibilities are that forward scattering from the time from a very fortunate location. It must, in fact, be ring edge (Silvia & Agol 2008) or back scattering from the a very common sort of object and, therefore, of general far side of the ring (Herbst et al. 2008) are important. importance to star and planet formation studies. A third phase of studies of this system began about a year ago when continued photometric monitoring with the SMARTS 1.3m/ANDICAM indicated that it was bright- ening again. Coincidentally, a GeminiN/GNIRS spectrum revealed that the spectral class of the system was now K1, rather than K7. The change in effective temperature was confirmed by the V-I color, which was bluer at maximum brightness by about 0.3 mag than it had been in the mid-2000’s. These facts suggested that the expected appearance of the previously fully occulted star was coming sooner rather than later. In March 2012 we were able to obtain a Keck/HIRES spectrum of the system which confirmed that result (Capelo et al. 2012). Referring to Fig. 1, we now can locate the left hand, or “trailing” edge of the occulting ring. The width of the screen turns out to be only slightly larger than the full extent of the orbits. The system spent only two years in full occultation at all phases, even near apastron. The full light curve of the Figure 2: The light curve of KH 15D phased with the system from 1995 until present (Fig. 3) reveals the situ- orbital period of 48.37d. Each year of observation is coded ation. Deep eclipses have begun again, now with star B by a different color, moving across the optical spectrum as the eclipsed object. True to its form, though, KH 15D from red, for the earliest data in 1995, to violet and finally continues to surprise us. Our expectation was that star black for the most recent data plotted here, which were B would be brighter than star A. The evidence is that its obtained in 2010. This figure covers the period of evolution spectral class, K1, indicates a hotter star than the K7 type during which the occulting screen progressively covered assigned to star A, and the fact that the system bright- more and more of the orbits. During the last two seasons, ness was inferred to be more than 0.75 mag brighter in I 2011 and 2012, the system brightened again, as shown during the 1960’s when both stars were visible. But the in Fig. 3 because the trailing edge of the screen now has most recent data indicate the opposite ... that star B is begun to reveal the orbit of the second star. about 0.5 mag fainter than star A. The steady progression of the occulting edge across the What does the future hold for this system? We have an binary continued throughout the first decade of the new amazing light curve from Spitzer/IRAC obtained during millenium and by 2010 both stars were fully occulted at the YSOVAR2 project led by John Stauffer that will allow all orbital phases. Since neither stellar photosphere was us to place better constraints on the grain size distribution, ever seen directly, the KH 15D system brightness never got since there is some evidence of transparency at 3.6 and above 17th magnitude. The phased light curves from 1995 4.5 µm. We have a marginal detection of KH 15D at sub- until 2010 are shown in Fig. 2. Each year has a different millimeter wavelengths obtained with the SMA and hope color code following the optical spectrum from red for the to confirm it one day with ALMA. It would be very in- earliest data to blue for the most recent. The flat portion teresting to know what the evolutionary state of the outer at around I = 14.5 mag corresponds to phases when the

8 leagues who have accompanied and guided me on this jour- ney of discovery particularly Catrina Hamilton, Reinhard 14 Mundt, Josh Winn, Chris Johns-Krull, Sandy Leggett and John Johnson. It has been a great pleasure to work with 15 all of them. The title of this essay is courtesy of Josh 16 Winn. References:

I (mag) 17 Agol, E., Barth, A. J., Wolf, S. & Charbonneau, D. 2004, ApJ, 600, 781 18 Alexander, R., 2012, ApJ, 757, L29 Badalian, H. S., & Erastova, L. K. 1970, Astronomicheskij Tsirkul- KH 15D yar, 591, 4 19 Barge, P., & Viton, M. 2003, ApJ, 593, L117 Capelo, H. L., Herbst, W., Leggett, S. K., Hamilton, C. M., & John- 1995 2000 2005 2010 son, J. A. 2012, ApJ, 757, L18 Year Chiang, E. & Murray-Clay, R. 2004, ApJ, 607, 913 Chiang, E. & Youdin, A. 2010, Ann. Rev. of Earth and Planetary Sciences, 38, 493 Figure 3: The light curve of KH 15D from Capelo et al. de Val-Borro, M., Gahm, G. F., Stempels, H. C. & Peplinski, A. (2012) including the most recent data showing its return 2011, MNRAS, 413, 2679 to a brighter state near apastron passage. The bluer color, Doyle, L. R. et al. 2011, Science 333, 1602 Goldreich, P. & Ward, W. R. 1973, ApJ, 183, 1051 earlier spectral class and radial velocity confirm that we Hamilton, C. M., Herbst, W., Shih, C. & Ferro, A. J. 2001, ApJ, are now seeing the other star in the system, the one to the 554, L201 left in Fig. 1. Unexpectedly it appears to be hotter but Hamilton, C. M., Herbst, W., Vrba, F. J., Ibraghimov, M. A., Mundt, R., Bailer-Jones, C. A. L., Filippenko, A. V., Li, W., Bejar, less luminous than its companion. Relative masses have V. J. S., Abraham, P., Kun, M., Moor, A., Benko, J., Csizmadia, S., not yet been determined. DePoy, D., Pogge, R. W., & Marshall, J. L.2005, AJ, 130, 1896 Hamilton, C. M., Johns-Krull, C. M., Mundt, R., Herbst, W., & Winn, J. N. 2012, ApJ, 751, 147 disk is like. The system is now a double-lined eclipsing Herbst, W. et al. 2002, PASP, 114, 1167 spectroscopic binary, albeit an unusual one in which the Herbst, W & Moran, E. 2006, ApJ, 630, 400 Herbst, W., Hamilton, C. M., LeDuc, K., Winn, J. N., Johns-Krull, eclipses come from a circumbinary disk, not the companion C. M., Mundt, R. & Ibrahimov, M. 2008, Nature 452, 194 star. Nonetheless it can be utilized just like an ordinary Herbst, W., LeDuc, K., Hamilton, C. M., Winn, J. N., Ibrahimov, SB2 to determine very accurate values of the fundamental M., Mundt, R., & Johns-Krull, C. M. 2010, AJ, 140, 2025 parameters of the stars including mass, radius, luminos- Hut, P. 1981, A&A, 99, 126 Johnson, J. A. & Winn, J. N., 2004, AJ, 127, 2344 ity and effective temperature. An updated version of the Johnson, J. A., Marcy, G. W., Hamilton, C. M., Herbst, W. & Johns- approach utilized by Winn et al. (2006) should constrain Krull, C. M., 2004, AJ, 128, 1265 these quantities, providing a nice challenge to models of Johnson, J. A., Winn, J. N., Rampazzi, F. Barbieri, C., Mito, H., Tarusawa, K., Tsvetkov, M., Borisova, A. & Meusinger, H. 2005, AJ, stellar evolution. 129, 1978 In the early days of studying this object I was often chas- Kearns, K. E., & Herbst, W. 1998, AJ, 116, 261 tised (in good-natured fashion, of course) by my colleagues Lawler, S. M., Herbst, W., Redfield, S., Hamilton, C. M., Johns- Krull, C. M., Winn, J. N., Johnson, J. A. & Mundt, R. 2010, ApJ, for devoting so much research time to a “peculiar” object. 711, 1297 Among other things, I was told that the system could have Maffei, P., Ciprini, S. & Tosti, G. 2005, MNRAS, 367, 1059 little impact on planet formation theories because it was Mundt, R., Hamilton, C. M., Herbst, W., Johns-Krull, C. M., & Winn, J. N. 2010, ApJ, 708, L5 a binary system and planet formation would be inhibited. Mundt, R., Hamilton, C. M., Herbst, W., Johns-Krull, C. M., & With the recent discoveries of planets in both circumbi- Winn, J. N. 2010, ApJ, 708, L5 nary (Doyle et al. 2011; Welsh et al. 2011; Orosz et Orosz, J. A., Welsh, W. F., Carter, J. A. et al. 2012a, ApJ, 758, 87 al. 2012a,b) and circumstellar (α Cen B) orbits around Orosz, J. A., Welsh, W. F., Carter, J. A. et al. 2012b, Science 337, 1511 binary stars we now know that this is not true. It has Silvia, D. W. & Agol, E. 2008, ApJ, 681, 1377 even been argued (Alexander 2012) that planet formation Welsh, W. F., Orosz, J. A., Carter, J. A. et al. 2012, Nature 481, may be enhanced in some circumbinary disks. Tatooine- 475 like systems may be quite common in our galaxy, and KH Winn, J. N., Garnavich, P. M., Stanek, K. Z., & Sasselov, D. D. 2003, ApJL, 593, L121 15D, because of its fortunate alignment in space, may be Winn, J. N., Holman, M. J., Johnson, J. A., Stanek, K. Z. & Gar- a critical object for extending our understanding of planet navich, P. M. 2004, ApJ, 603, L45 formation in binaries and elsewhere. Winn, J. N., Hamilton, C. M., Herbst, W., Hoffman, J. L., Holman, M. J., Johnson, J. A. & Kucher, M. J. 2006, ApJ 644, 510 I want to finish by acknowledging my many esteemed col-

9 Krumholz, & Hunt 2010; Bolatto et al. 2011), and there is no obvious reason that the Toomre Q value should be Perspective sensitive to metallicity. This is strong evidence that there Star Formation in Atomic must be some other factor determining where stars do and and Molecular Gas do not form. The observed relationship between H2 and star formation Mark Krumholz led to a number of theoretical models to calculate under what conditions the H i to H2 transition occurs, and to use this as a marker for where star formation will occur (Robertson & Kravtsov 2008; Krumholz, McKee, & Tum- linson 2008, 2009a, 2009b; Gnedin, Tassis, & Kravtsov 2009; McKee & Krumholz 2010). In these models, metallicity matters because H2 forms predominantly via a grain- catalyzed reaction, and because grains provide extinction that shields H2 molecules from the photodissociating interstellar radiation field (ISRF). Therefore lowering the metallicity (and thus the dust abundance) makes it harder to form H2. To first order, the models predict that the H i-H2 transition should occur at critical column density ′ −1 ′ In the nearby universe, the relationship between star for- ∼ 10/Z M⊙ pc , where Z is the metallicity normalized mation and molecular gas is obvious, since star-forming to Solar. These models very successfully reproduce the ob- regions are invariably located within in molecular clouds. served H i to H2 transition (e.g. Lee et al. 2012) and the However, correlation does not prove causation, and the associated jump in the star formation rate, and as illus- question of why star formation is correlated with the molec- trated in Figure 1, they correctly predicted its metallicity- ular phase of the interstellar medium (ISM) turns out to dependence before it was observationally measured (Bo- be a subtle one. To begin answering it, we must first take latto et al. 2011). a step back to a more basic one: why do some parts of However, these models are still partly phenomenological, the interstellar medium form stars, while other parts do because they simply assume that stars form only in H2; not? Until roughly five years ago, the answer would have they do not answer the question why this should be so. seemed straightforward: stars form wherever galactic disks Schaye (2004) proposed the earliest version of an answer. are gravitationally unstable (e.g. Quirk 1972), as indicated He argued that the onset of gravitational instability in ∼ by a Toomre (1964) Q parameter less than 1. This idea galactic disks is caused by the appearance of a cold atomic was supported by Hα imaging that appeared to indicate phase in the ISM, which in turn is dictated primarily by sharp edges to the star-formation in nearby galactic disks the gas surface density. This inverts the direction of causa- ∼ ≫ around the radii where Q changed from 1 to 1 (Mar- tion from the classical model: a temperature drop causes tin & Kennicutt 2001). In this view, the transition from instability and thus star formation, rather than instabil- i H to H2 is neither sufficient nor necessary for star forma- ity causing the formation of dense clouds that then be- tion. Instead, molecular clouds, as gravitationally bound come cold. While the metallicity-dependence predicted objects, are simply the markers of where the ISM is gravi- by Schaye’s model turns out to be too weak to match the tationally unstable, and the same gravitational instability observations shown in Figure 1 and similar data, the un- that forms molecular clouds also produces stars. derlying idea that what triggers star formation is a loss of However, this simple picture has encountered serious ob- thermal pressure support is a powerful one. servational difficulties in the past few years. First, GALEX Krumholz, Leroy, & McKee (2011; hereafter KLM), picked showed that star formation in many galactic disks does up on this idea by considering simple spherical clouds and ≫ not in fact cease where Q 1 (Boissier et al. 2007). Sec- calculating their equilibrium temperature and chemical ond, the THINGS survey found no significant correlation state (H i- versus H -dominated, C+ versus CO-dominated) ∼ 2 between star formation and the value of Q on 1 kpc as a function of the clouds’ volume density and visual ex- scales (Leroy et al. 2008). On the other hand, there is tinction. From the temperature T and density n, they also a threshold gas column density at which the ISM transi- 3/2 calculate the clouds’ Bonnor-Ebert mass, MBE ∝ T /n. tions from predominantly atomic to predominantly molec- They find that, over a very wide range of cloud parame- ular, and star formation does diminish greatly outside ters, there is an excellent correlation between the presence that molecular-dominated region (Bigiel et al. 2008, 2010; of large quantities of H2 and low values of MBE. KLM ar- Wyder et al. 2009). Moreover, the value of the thresh- gue that this is the reason that star formation occurs in old is sensitive to the metallicity of the gas (Fumagalli,

10 obtain similar results for other low-metallicity dwarfs. Glover & Clark (2012a, hereafter GC12a) investigate a similar question using turbulent hydrodynamic simulations including time-dependent chemistry and optically-thin line cooling. In their simulations, they investigate the role of different chemical and cooling processes by turning them on and off. Due to the computational cost they are un- able to explore a wide parameter space as KLM do, but their approach has the significant advantage that they can directly measure the rate of star formation in the simulations, rather than relying on a conjectured relationship between MBE and star formation. Their numerical results reinforce the picture described above. They find that the star formation rate in their simulations is essentially un- changed by whether or not they include the chemical tran- + sitions from H i to H2 or C to CO, and the concomitant change in available line cooling channels. However, if they do not include dust shielding and simply assume that the gas is optically thin to the interstellar radiation field (i.e. if they set τ = 0 in the cooling term above), they find that Figure 4: Observed relationship between the gas mass star formation is almost entirely suppressed. The under- Σ (including both H i and H ) and star formation rate gas 2 lying reason is that photoelectric heating keeps the gas Σ per unit area in the Small Magellanic Cloud. The SFR warm, preventing the development of cold, dense, gravi- grayscale shows the fraction of 12 pc-sized pixels in the tationally unstable structures. Figure 2 shows a sample SMC that fall into a given box on the Σ − Σ plane. gas SFR result from their simulations. The solid black line labelled cZ =0.2 is the prediction of Krumholz, McKee, & Tumlinson (2009b) for the SMC’s The realization that the relationship between H2 and star metallicity. The dashed black line cZ = 1 is the corre- formation is not causal, however, opens up an interest- sponding prediction for Solar metallicity, and provides a ing possibility, again calculated analytically by Krumholz good fit to the roughly solar metallicity galaxies sampled (2012) and numerically by Glover & Clark (2012b). The by Bigiel et al. (2008). Courtesy A. Bolatto and the AAS. models of KLM and GC12a show that the equilibrium chemical and thermal states of interstellar gas are strongly molecular gas. correlated, such that only gas where the equilibrium chemical state is H2-dominated are also cold enough to form The physical origin of the temperature-H2 correlation is stars. However, the time required to reach thermal equi- easy to understand. The chemical state of the gas is con- librium is ∼ 3 orders of magnitude shorter than the time trolled by the balance between H formation on dust grains 2 required to reach chemical equilibrium – formation of H2 and photodissociation by the interstellar radiation field. via grain catalysis is simply a very slow process! In the 2 ′ The formation rate per unit volume scales as n Z , while Milky Way today this does not matter much, because both ′ −τ the dissociation rate scales as nZ Ue , where U is the processes are relatively fast compared to typical dynam- strength of the ISRF and τ is the dust optical depth. Sim- ical times in galaxies or even inside molecular clouds. It ilarly, the temperature is controlled by a balance between matters little if gas cools before coming to chemical equi- line cooling and heating via the grain photoelectric effect. librium, if both processes take less time than is required 2 ′ The cooling rate scales as n Z , and the heating rate as for the gas to undergo gravitational collapse. nZ′Ue−τ , exactly as the formation and photodissociation rates. Given the nearly identical functional forms, it is not However, both cooling and H2 formation rates are propor- tional to the metallicity, and thus the timescales for both surprising that gas that becomes molecular should also be ′−1 cold, and vice-versa. Moreover, it turns out that what processes vary as Z . Since dynamical times do not matters most is shielding and not cooling, so it makes scale with metallicity, this means that, at sufficiently low little difference for star formation whether the carbon is metallicity, one enters a regime where dynamical times are predominantly in the form of C+ or CO. Thus one pre- smaller than chemical equilibration times, but still longer dicts that, in gas where the chemical composition is such than cooling times. By comparing equilibrium chemi- that the hydrogen is mostly H but the carbon is mostly cal models to time-dependent simulations, Krumholz & 2 ′ ∼ C+, star formation should occur. Bolatto et al. (2011) find Gnedin (2011) find that this regime begins at Z 0.01. this to be the case in the SMC, and Schruba et al. (2012) At such low metallicities, initially atomic clouds can cool

11 3.0 3.0

2.5 2.5 log Z' log Z' log Z' log Z' log Z' log Z' log Z' log Z' log Z'

-= -= -= -= -= -= -= -= 2.0 = 2.0

0 0.5 1.5 2.5 3.5 1 2 3 4 D K @ H2

1.5 1.5 f log T

1.0 1.0

0 0.5 1 1.5 2 2.5 = = - = - 0.5 = - = - = -0.5 log Z' log Z' log Z' log Z' log Z' log Z' log 0.0 0.0 -5 -4 -3 -2 -1 0 1 2

log ttff

Figure 6: Time evolution of gas temperature (black lines, left axis) and H2 mass fraction (blue dashed lines, right −3 axis) for a cloud with density 30 cm , extinction AV =2 mag, initial temperature T = 1000 K, and initial composition pure H i. Lines are labelled by the metallicity Z′, from Solar to 10−4 Solar. Times are measured in free- fall times, with the gray vertical lines indicating 1 and 10 free-fall times. Taken from Krumholz (2012).

this observationally will be somewhat tricky. At very low metallicities, CO ceases to be a reliable tracer of molecular gas (Wolfire, Hollenbach, & McKee 2010; Glover & Mac Figure 5: Distribution of gas density and temperature in Low 2011), and thus it is difficult to determine if H2 is three simulations by GC12a. The top panel is a simulation present or not. However, using dust observations together with full chemistry, but where dust shielding is ignored. with high resolution 21 cm maps it is possible to estimate The middle panel is a simulation where shielding is in- the masses in the molecular and atomic phases (Bolatto cluded, but the gas is atomic and no chemical reactions et al. 2011), and thereby to check the predictions of these that convert either H or C to molecular form are allowed. models. ALMA observations of the dust combined with The bottom panel is a simulation with full chemistry and VLA 21 cm maps of very low-metallicity dwarfs seem the shielding. Notice the absence of dense, cold gas in the top most promising route for a future observational test. panel, and its presence in the two bottom ones. Courtesy Bigiel, F., et al. 2008, AJ, 136, 2846 S. Glover. —. 2010, AJ, 140, 1194 Boissier, S., et al. 2007, ApJS, 173, 524 Bolatto, A. D., et al. 2011, ApJ, 741, 12 and proceed to star formation before the bulk of their mass Fumagalli, M., Krumholz, M. R., & Hunt, L. K. 2010, ApJ, 722, 919 can convert to molecular form. Figure 3 shows an exam- Gnedin, N. Y., Tassis, K., & Kravtsov, A. V. 2009, ApJ, 697, 55 Glover, S. C. O., & Clark, P. C. 2012a, MNRAS, 421, 9 ple calculation of the thermal and chemical evolution of —. 2012b, MNRAS, 326, 377 a cloud from Krumholz (2012). The important point to Glover, S. C. O., & Mac Low, M. M. 2011, MNRAS, 412, 337 take from the figure is that, for the cloud shown, the time Krumholz, M. R. 2012, ApJ, 759, 9 required for the gas to cool to near its equilibrium temper- Krumholz, M. R., & Gnedin, N. Y. 2011, ApJ, 729, 36 Krumholz, M. R.., Leroy, A. K., & McKee, C. F. 2011, ApJ, 731, 25 ature is no more than a free-fall time even at metallicities Krumholz, M. R., McKee, C. F., Tumlinson, J. 2008, ApJ, 689, 865 ′ as low as log Z = −4. On the other hand, for metallicities —. 2009a, ApJ, 693, 216 ′ below log Z =0.5 it does not reach 50% H2 composition —. 2009b, ApJ, 699, 850 until more than 1 free-fall time, and for metallicities below Lee, M.-Y., et al. 2012, ApJ, 748, 75 ′ Leroy, A. K., et al. 2008, AJ, 136, 2782 log Z = −1.5 it requires more than 10 free-fall times to Martin, C. L., & Kennicutt, R. C. 2001, ApJ, 555, 301 become H2-dominated. It seems likely that such a cloud McKee, C. F., & Krumholz, M. R. 2010, ApJ, 709, 308 would form stars and disperse by star formation feedback Quirk, W. J. 1972, ApJ, 176, L9 before converting a significant fraction of its mass to H . Robertson, B. E., & Kravtsov, A. V. 2008, ApJ, 680, 1083 2 Schaye, J. 2004, ApJ, 609, 667 The implication of this result is that, in very low metal- Schruba, A., et al. 2012, AJ, 143, 138 licity galaxies, star formation should be associated with Toomre, A. 1964, ApJ, 139, 12127 Wolfire, M. G., Hollenbach, D., McKee, C. F. 2010, ApJ, 716, 1191 cold atomic clouds rather than molecular ones. Checking Wyder, T. K., et al. 2009, ApJ, 696, 1834

12 Abstracts of recently accepted papers

Protostars, multiplicity, and disk evolution in the Corona Australis region: A Herschel Gould Belt Study Aurora Sicilia Aguilar1, Thomas Henning2, Hendrik Linz2, Philippe André3, Amy Stutz2, Carlos Eiroa1 and Glenn J. White4,5 1 Departamento de F´ısica Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain 2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany 3 Laboratoire AIM, CEA/DSM–CNRS–UniversitéParis Diderot, IRFU/Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France 4 RAL Space, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK 5 Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK E-mail contact: aurora.sicilia at uam.es The CrA region and the Coronet cluster form a nearby (138 pc), young (1-2 Myr) star-forming region hosting a moderate population of YSO. We present Herschel PACS photometry at 100 and 160 µm, obtained as part of the Herschel Gould Belt Survey. The Herschel maps reveal the cluster members with high sensitivity and high dynamic range. Many of the cluster members are detected, including some embedded, very low-mass objects, several protostars, and substantial emission from the surrounding cloud. The Herschel data provide sufficient spatial resolution to detect small-scale details, such as bright filaments around the IRS5 protostar complex and a bubble-shaped rim associated with the Class I object IRS2. The disks around the Class II objects display a wide range of mid- and far-IR excesses consistent with different disk structures. We have modeled the disks using the RADMC radiative transfer code, finding an interesting mixture of objects for a young and presumably coeval cluster. Some of them are consistent with flared, massive, relatively primordial disks (SCrA, TCrA). Others display significant evidence for inside–out evolution, consistent with the presence of inner holes/gaps (G-85, G-87). Finally, we find disks with a dramatic small dust depletion (G-1, HBC677) that, in some cases, could be related to truncation or to the presence of large gaps in a flared disk (CrA-159). The derived masses for the disks around the low-mass stars are found to be below the typical values in Taurus, in agreement with previous Spitzer observations. Given the high degree of multiplicity and interactions observed among the protostars in the region, the diversity of disks may be a consequence of the early star formation history, which should also be taken into account when studying the disk properties in similar sparsely populated clusters. Accepted by A&A http://arxiv.org/pdf/1211.6945

A high-resolution spectropolarimetric survey of Herbig Ae/Be stars - I. Observations and measurements E. Alecian1,2, G.A. Wade2, C. Catala1, J.H. Grunhut2,3, J.D. Landstreet4,5, S. Bagnulo5, T. B¨ohm6,7, C.P. Folsom5, S. Marsden8,9, I. Waite9 1 LESIA-Observatoire de Paris, CNRS, UPMC Univ., Univ. Paris-Diderot, 5 place Jules Janssen, F-92195 Meudon Principal Cedex, France 2 Dept. of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston K7K 7B4, Canada 3 Department of Physics, Queen’s University, Kingston, Canada 4 Dept. of Physics & Astronomy, University of Western Ontario, London N6A 3K7, Canada 5 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK 6 Universit´ede Toulouse; UPS-OMP; IRAP; Toulouse, France 7 CNRS; IRAP; 14, avenue Edouard Belin, F-31400 Toulouse, France

13 8 Centre for Astronomy, School of Engineering and Physical Sciences, James Cook University, Townsville, 4811, Australia 9 Faculty of Sciences, University of Southern Queensland, Toowoomba, 4350, Australia E-mail contact: evelyne.alecian at obspm.fr This is the first in a series of papers in which we describe and report the analysis of a large survey of Herbig Ae/Be stars in circular spectropolarimetry. Using the ESPaDOnS and Narval high-resolution spectropolarimeters at the Canada-France-Hawaii and Bernard Lyot Telescopes, respectively, we have acquired 132 circularly-polarised spectra of 70 Herbig Ae/Be stars and Herbig candidates. The large majority of these spectra are characterised by a resolving power of about 65,000, and a spectral coverage from about 3700 ang to 1 micron. The peak SNR per CCD pixel ranges from below 100 (for the faintest targets) to over 1000 (for the brightest). The observations were acquired with the primary aim of searching for magnetic fields in these objects. However, our spectra are suitable for a variety of other important measurements, including rotational properties, variability, binarity, chemical abundances, circumstellar environment conditions and structure, etc. In this first paper, we describe the sample selection, the observations and their reduction, and the measurements that will comprise the basis of much of our following analysis. We describe the determination of fundamental parameters for each target. We detail the Least-Squares Deconvolution that we have applied to each of our spectra, including the selection, editing and tuning of the LSD line masks. We describe the fitting of the LSD Stokes I profiles using a multi-component model that yields the rotationally-broadened photospheric profile (providing the projected rotational velocity and radial velocity for each observation) as well as circumstellar emission and absorption components. Finally, we diagnose the longitudinal Zeeman effect via the measured circular polarisation, and report the longitudinal magnetic field and Stokes V Zeeman signature detection probability. As an appendix, we provide a detailed review of each star observed. Accepted for publication in MNRAS http://arxiv.org/pdf/1211.2907

A high-resolution spectropolarimetric survey of Herbig Ae/Be stars - II. Rotation E. Alecian1,2, G.A. Wade2, C. Catala1, J.H. Grunhut2,3, J.D. Landstreet4,5, T. Böhm6,7, C.P. Folsom5, S. Marsden8,9 1 LESIA-Observatoire de Paris, CNRS, UPMC Univ., Univ. Paris-Diderot, 5 place Jules Janssen, F-92195 Meudon Principal Cedex, France 2 Dept. of Physics, Royal Military College of Canada, PO Box 17000, Stn Forces, Kingston K7K 7B4, Canada 3 Department of Physics, Queen’s University, Kingston, Canada 4 Dept. of Physics & Astronomy, University of Western Ontario, London N6A 3K7, Canada 5 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland, UK 6 Universitéde Toulouse; UPS-OMP; IRAP; Toulouse, France 7 CNRS; IRAP; 14, avenue Edouard Belin, F-31400 Toulouse, France 8 Centre for Astronomy, School of Engineering and Physical Sciences, James Cook University, Townsville, 4811, Australia 9 Faculty of Sciences, University of Southern Queensland, Toowoomba, 4350, Australia E-mail contact: evelyne.alecian at obspm.fr We report the analysis of the rotational properties of our sample of Herbig Ae/Be (HAeBe) and related stars for which we have obtained high-resolution spectropolarimetric observations. Using the projected rotational velocities measured at the surface of the stars, we have calculated the angular momentum of the sample and plotted it as a function of age. We have then compared the angular momentum and the v sin i distributions of the magnetic to the non-magnetic HAeBe stars. Finally we have predicted the v sin i of the non-magnetic, non-binary (”normal”) stars in our sample when they reach the ZAMS, and compared them to various catalogues of the v sin i of main-sequence stars. First, we observe that magnetic HAeBe stars are much slower rotators than normal stars, indicating that they have been more efficiently braked than the normal stars. In fact, the magnetic stars have already lost most of their angular momentum, despite their young ages (lower than 1 Myr for some of them). Secondly, our analysis suggests that the low mass (1.5 < M < 5 M⊙) normal HAeBe stars evolve with constant angular momentum towards the ZAMS, while the high-mass normal HAeBe stars (M > 5 M⊙) are losing angular momentum. We propose that winds, which are expected to be stronger in massive stars, are at the origin of this phenomenon.

14 Accepted by MNRAS http://arxiv.org/pdf/1211.2911

Spectroscopy of brown dwarf candidates in IC 348 and the determination of its substellar IMF down to planetary masses C. Alves de Oliveira1, E. Moraux2, J. Bouvier2, G. Duchene2,3, H. Bouy4, T. Maschberger2, and P. Hudelot5 1 European Space Astronomy Centre (ESA), P.O. Box 78, 28691 Villanueva de la Cañada, Madrid, Spain 2 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR5274, Grenoble, 38041, France 3 Astronomy Department, University of California, Berkeley, CA 947203411, USA 4 Centro de Astrobiologa (INTA-CSIC); LAEFF, P.O. Box 78, 28691 Villanueva de la Cañada, Spain 5 Institut d’Astrophysique de Paris, UMR 7095 CNRS, UniversitéPierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France E-mail contact: calves at sciops.esa.int Context. Brown dwarfs represent a sizable fraction of the stellar content of our Galaxy and populate the transition between the stellar and planetary mass regime. There is however no agreement on the processes responsible for their formation. Aims. We have conducted a large survey of the young, nearby cluster IC 348, to uncover its low-mass brown dwarf population and study the cluster properties in the substellar regime. Methods. Deep optical and near-IR images taken with MegaCam and WIRCam at the Canada-France-Hawaii Telescope (CFHT) were used to select photometric candidate members. A spectroscopic follow-up of a large fraction of the candidates was conducted to assess their youth and membership. Results. We confirmed spectroscopically 16 new members of the IC 348 cluster, including 13 brown dwarfs, contributing significantly to the substellar census of the cluster, where only 30 brown dwarfs were previously known. Five of the new members have a L0 spectral type, the latest-type objects found to date in this cluster. At 3 Myr, evolutionary models estimate these brown dwarfs to have a mass of ∼13 Jupiter masses. Combining the new members with previous census of the cluster, we constructed the IMF complete down to 13 Jupiter masses. Conclusions. The IMF of IC 348 is well fitted by a log-normal function, and we do not see evidence for variations of the mass function down to planetary masses when compared to other young clusters. Accepted by A&A http://arxiv.org/pdf/1211.4029

The mid-infrared extinction law in the darkest cores of the Pipe Nebula J. Ascenso1, C. J. Lada2, J. Alves3, C. G. Román-Zúñiga4, and M. Lombardi5 1 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Munchen, Germany 2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 3 University of Vienna, Turkenschanzstrasse 17, 1180 Vienna, Austria 4 Instituto de Astronom´ıa, Unidad Académica de Ensenada, Universidad Autónoma de México. Ensenada 22860 México 5 University of Milan, Department of Physics, via Celoria 16, 20133 Milan, Italy Context. The properties of dust grains, in particular their size distribution, are expected to differ from the interstellar medium to the high-density regions within molecular clouds. Aims. We measure the mid-infrared extinction law produced by dense material in molecular cloud cores. Since the extinction at these wavelengths is caused by dust, the extinction law in cores should depart from that found in low- density environments if the dust grains have different properties. Methods. We use the unbiased LINES method to measure the slope of the reddening vectors in color-color diagrams. We derive the mid-infrared extinction law toward the dense cores B59 and FeSt 1-457 in the Pipe Nebula over a range of visual extinction between 10 and 50 magnitudes, using a combination of Spitzer/IRAC, and ESO NTT/VLT data.

15 Results. The mid-infrared extinction law in both cores departs significantly from a power-law between 3.6 and 8 micron, suggesting that these cores contain dust with a considerable fraction of large dust grains. We find no evidence for a dependence of the extinction law with column density up to 50 magnitudes of visual extinction in these cores, and no evidence for a variation between our result and those for other clouds at lower column densities reported elsewhere in the literature. This suggests that either large grains are present even in low column density regions, or that the existing dust models need to be revised at mid-infrared wavelengths. We find a small but significant difference in the extinction law of the two cores, that we tentatively associate with the onset of star formation in B59. Accepted to A&A http://arxiv.org/pdf/1211.6556

Bayesian inference of T Tauri star properties using multi-wavelength survey photometry Geert Barentsen1,2, Jorick S. Vink1, Janet E. Drew2, and Stuart E. Sale3 1 Armagh Observatory, College Hill, Armagh BT61 9DG, U.K. 2 Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB, U.K. 3 Rudolf Peierls Centre for Theoretical Physics, Keble Road, Oxford OX1 3NP, U.K. E-mail contact: geert at barentsen.be There are many pertinent open issues in the area of star and planet formation. Large statistical samples of young stars across star-forming regions are needed to trigger a breakthrough in our understanding, but most optical studies are based on a wide variety of spectrographs and analysis methods, which introduces large biases. Here we show how graphical Bayesian networks can be employed to construct a hierarchical probabilistic model which allows pre-main sequence ages, masses, accretion rates, and extinctions to be estimated using two widely available photometric survey databases (IPHAS r/i/Hα and 2MASS J-band magnitudes.) Because our approach does not rely on spectroscopy, it can easily be applied to homogeneously study the large number of clusters for which Gaia will yield membership lists. We explain how the analysis is carried out using the Markov Chain Monte Carlo (MCMC) method and provide Python source code. We then demonstrate its use on 587 known low-mass members of the star-forming region NGC 2264 (Cone Nebula), arriving at a median age of 3.0 Myr, an accretion fraction of 20±2% and a median accretion rate of 10−8.4 −1 M⊙ yr . The Bayesian analysis formulated in this work delivers results which are in agreement with spectroscopic studies already in the literature, but achieves this with great efficiency by depending only on photometry. It is a significant step forward from previous photometric studies, because the probabilistic approach ensures that nuisance parameters, such as extinction and distance, are fully included in the analysis with a clear picture on any degeneracies. Accepted by MNRAS http://arxiv.org/pdf/1211.6108

The Magnetic Topology of the Weak-Lined T Tauri Star V410 - A Simultaneous Tem- perature and Magnetic Field Inversion T. A. Carroll1, K. G. Strassmeier1, J. B. Rice2, and A. Küenstler1 1 Leibniz-Institute for Astrophysics Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany 2 Department of Physics, Brandon University, Brandon, Manitoba R7A 6A9, Canada E-mail contact: tcarroll at aip.de We present a detailed temperature and magnetic investigation of the T Tauri star V410 Tau by means of a simultaneous Doppler- and Zeeman-Doppler Imaging. Moreover we introduce a new line profile reconstruction method based on a singular value decomposition (SVD) to extract the weak polarized line profiles. One of the key features of the line profile reconstruction is that the SVD line profiles are amenable to radiative transfer modeling within our Zeeman- Doppler Imaging code iMap. The code also utilizes a new iterative regularization scheme which is independent of any additional surface constraints. To provide more stability a vital part of our inversion strategy is the inversion of both Stokes I and Stokes V profiles to simultaneously reconstruct the temperature and magnetic field surface distribution of V410 Tau. A new image-shear analysis is also implemented to allow the search for image and line profile distortions induced by a differential rotation of the star. The magnetic field structure we obtain for V410 Tau shows a good

16 spatial correlation with the surface temperature and is dominated by a strong field within the cool polar spot. The Zeeman-Doppler maps exhibit a large-scale organization of both polarities around the polar cap in the form of a twisted bipolar structure. The magnetic field reaches a value of almost 2 kG within the polar region but smaller fields are also present down to lower latitudes. The pronounced non-axisymmetric field structure and the non-detection of a differential rotation for V410 Tau supports the idea of an underlying α2-type dynamo, which is predicted for weak-lined T Tauri stars. Accepted by A&A http://arxiv.org/pdf/1211.2720

A close-up view of a bipolar jet: Sub-arcsecond near-IR imaging of the high-mass protostar IRAS 20126+4104 R. Cesaroni1, F. Massi1, C. Arcidiacono1,2, M.T. Beltrán1, D. McCarthy3, C. Kulesa3, K. Boutsia4, D. Paris4, F. Quirós-Pacheco1 and M. Xompero1 1 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy 2 INAF, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna, Italy 3 Steward Observatory, The University of Arizona, 933 N. Cherry Ave., Tucson, AZ-85721, USA 4 INAF, Osservatorio Astronomico di Roma, via Frascati 33, I-00040, Monteporzio, Italy E-mail contact: cesa at arcetri.astro.it

The formation of OB-type stars up to (at least) 140 M⊙ can be explained via disk-mediated accretion and in fact growing observational evidence of disk-jet systems is found in high-mass star-forming regions. With the present observations we wish to investigate at sub-arcsecond resolution the jet structure close to the well studied high-mass protostar IRAS 20126+4104, which is known to be surrounded by a Keplerian disk. Adaptive optics imaging of the 2.2 µm continuum and H2 and Brγ line emission have been performed with the Large Binocular Telescope, attaining an angular resolution of ∼90 mas and an astrometric precision of ∼100 mas. While our results are consistent with previous K-band images by other authors, the improved (by a factor ∼3) resolution allows us to identify a number of previously unseen features, such as bow shocks spread all over the jet structure. Also, we conﬁrm the existence of a bipolar nebulosity within 1′′ from the protostar, prove that the emission from the brightest, SE lobe is mostly due to the H2 line, and resolve its structure. Comparison with other tracers such as masers, thermal molecular line emission, and free-free continuum emission proves that the bipolar nebulosity is indeed tracing the root of the bipolar jet powered by the deeply embedded protostar at the center of the Keplerian disk. Accepted by Astronomy and Astrophysics http://www.arcetri.astro.it/science/starform/preprints/cesa_23.pdf

The Herschel DIGIT Survey of Weak-line T Tauri Stars: implications for disk evolution and dissipation Lucas A. Cieza1, Johan Olofsson2, Paul M. Harvey3, Neal J. Evans II3, Joan Najita4, Thomas Henning2, Bruno Mer´ın5, Armin Liebhart6, Manuel Gudel6, Jean-Charles Augereau7, and Christophe Pinte7 1 Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822. USA 2 Max Planck Institute für Astronomie, Königstuhl 17, Heidelberg, Germany 3 Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA 4 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 86719, USA 5 Herschel Science Centre, European Space Astronomy Centre, ESA, P.O. Box 78, 28691 Villanueva de la Cañada, Madrid, Spain 6 Department of Astronomy, Univ. of Vienna, Türkenschanzstr. 17, A-1180 Vienna, Austria 7 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, BP 53, 38041 Grenoble cedex 9, France E-mail contact: lcieza at ifa.hawaii.edu As part of the ”Dust, Ice, and Gas In Time (DIGIT)” Herschel Open Time Key Program, we present Herschel photometry (at 70, 160, 250, 350 and 500 micron) of 31 Weak-Line T Tauri star (WTTS) candidates in order to investigate the evolutionary status of their circumstellar disks. Thirteen stars in our sample had circumstellar disks

17 previously known from infrared observations at shorter wavelengths, while eighteen of them had no previous evidence for a disk. We detect a total of 15 disks as all previously known disks are detected at one or more Herschel wavelengths and two additional disks are identified for the first time. The spectral energy distributions (SEDs) of our targets seem to trace the dissipation of the primordial disk and the transition to the debris disk regime. Seven of the 15 disks appear to be optically thick primordial disks, including two objects with SEDs indistinguishable from those of typical Classical T Tauri stars, four objects that have significant deficit of excess emission at all IR wavelengths, and one ”pre-transitional” object with a known gap in the disk. Despite their previous WTTS classification, we find that the seven targets in our sample with optically thick disks show evidence for accretion. The remaining eight disks have weaker IR excesses similar to those of optically thin debris disks. Six of them are warm and show significant 24 micron Spitzer excesses, while the last two are newly identified cold debris-like disks with photospheric 24 micron fluxes, but significant excess emission at longer wavelengths. The Herschel photometry also places strong constraints on the −3 −4 non-detections, where systems with F70/F70⋆ > 5 – 15 and Ldisk/L⋆ > 10 to 10 can be ruled out. We present preliminary models for both the optically thick and optically thin disks and discuss our results in the context of the evolution and dissipation of circumstellar disks. Accepted by ApJ http://arxiv.org/pdf/1211.4510

SiO collimated outflows driven by high-mass YSOs in G24.78+0.08 C. Codella1,2, M.T. Beltrán1, R. Cesaroni1, L. Moscadelli1, R. Neri3, M. Vasta1, Q. Zhang4 1 INAF, Osservatorio Astrofisico di Arcetri, Firenze, Italy 2 UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), France 3 IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA E-mail contact: codella at arcetri.astro.it Context: The region G24.78+0.08, which is associated with a cluster of high-mass young stellar objects in different evolutionary stages, is one of the best laboratories to investigate massive star-formation. Aims: We aim to image the molecular outflows towards G24.78+0.08 at high-angular resolution using SiO emission, which is considered the classical tracer of protostellar jets. In this way we study the mass loss process in which we previously detected a hypercompact ionised region, as well as rotation and infall signatures. Methods: We performed SiO observations with the VLA interferometer in the J = 1–0 v=0 transition and with the SMA array in the 5–4 transition. A complementary IRAM 30-m single-dish survey in the (2–1), (3–2), (5–4), and (6–5) SiO lines was also carried out. Results: Two collimated SiO high-velocity (up to 25 km s−1 w.r.t. the systemic velocity) outflows driven by the A2 and C millimeter continuum massive cores have been imaged. On the other hand, we detected no SiO outflow driven by the young stellar objects in more evolved evolutionary phases that are associated with ultracompact (B) or hypercompact (A1) Hii regions. The A2 outflow has also been traced using H2S. The LVG analysis of the SiO emission reveals high-density gas (103–104 cm−3), with well constrained SiO column densities (0.5–1 1015 cm−2). The driving source of the A2 outflow is associated with typical hot core tracers such as CH3OCHO (methyl formate), C2H3CN 13 (vinyl cyanide), HCC CN (cyanoacetilene), and (CH3)2CO (acetone). 4 Conclusions: The driving source of the main SiO outflow in G24 has an estimated luminosity of a few 10 L⊙ (typical of a late O-type star) and is embedded in the 1.3 mm continuum core A2, which in turn is located at the centre of a hot core that rotates on a plane perpendicular to the outflow main axis. The present SiO images support a scenario similar to the low-mass case for massive star formation, where jets that are clearly traced by SiO emission, create outflows of swept-up ambient gas usually traced by CO. Accepted by A&A http://arxiv.org/pdf/1212.0473

A Search for Giant Planet Companions to T Tauri Stars Christopher J. Crockett1,3, Naved I. Mahmud3,4, L. Prato2,3, Christopher M. Johns-Krull3,4, Daniel T. Jaﬀe5, Patrick M. Hartigan4, Charles A. Beichman6,7 1 U.S. Naval Observatory, 10391 W. Naval Observatory Road, Flagstaﬀ, AZ 86001, USA

18 2 Lowell Observatory, 1400 W Mars Hill Road, Flagstaff, AZ 86001, USA 3 Visiting Astronomer at the Infrared Telescope Facility 4 Department of Physics and Astronomy, Rice University, MS-108, 6100 Main Street, Houston, TX 77005, USA 5 Department of Astronomy, University of Texas, R.L. Moore Hall, Austin, TX 78712, USA 6 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 7 NASA Exoplanet Science Institute (NExScI), California Institute of Technology, 770 S. Wilson Ave, Pasadena, CA 91125, USA E-mail contact: ccrockett at nofs.navy.mil We present results from an ongoing multiwavelength radial velocity (RV) survey of the Taurus-Auriga star forming region as part of our effort to identify pre–main sequence giant planet hosts. These 1-3 Myr old T Tauri stars present significant challenges to traditional RV surveys. The presence of strong magnetic fields gives rise to large, cool star spots. These spots introduce significant RV jitter which can mimic the velocity modulation from a planet-mass companion. To distinguish between spot-induced and planet-induced RV modulation, we conduct observations at ∼6700 A˚ and ∼2.3 µm and measure the wavelength dependence (if any) in the RV amplitude. CSHELL observations of the known exoplanet host Gl 86 demonstrate our ability to detect not only hot Jupiters in the near infrared but also secular trends from more distant companions. Observations of nine very young stars reveal a typical reduction in RV amplitude at the longer wavelengths by a factor of ∼2–3. While we can not confirm the presence of planets in this sample, three targets show different periodicities in the two wavelength regions. This suggests different physical mechanisms underlying the optical and K band variability. Accepted to ApJ http://arxiv.org/pdf/1211.1389

The Young Open Clusters King 12, NGC 7788, and NGC 7790: Pre-Main Sequence Stars and Extended Stellar Haloss T. J. Davidge1 1 Dominion Astrophysical Observatory, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC Canada V9E 2E7 The stellar contents of the open clusters King 12, NGC 7788, and NGC 7790 are investigated using MegaCam images. Comparisons with isochrones yield an age < 20 Myr for King 12, 20–40 Myr for NGC 7788, and 60 – 80 Myr for NGC 7790 based on the properties of stars near the main sequence turn-oﬀ (MSTO) in each cluster. The reddening of NGC 7788 is much larger than previously estimated. The luminosity functions (LFs) of King 12 and NGC 7788 show breaks that are attributed to the onset of pre-main sequence (PMS) objects, and comparisons with models of PMS evolution yield ages that are consistent with those measured from stars near the MSTO. In contrast, the r’ LF of main sequence stars in NGC 7790 is matched to r’ = 20 by a model that is based on the solar neighborhood mass function. The structural properties of all three clusters are investigated by examining the two-point angular correlation function of blue main sequence stars. King 12 and NGC 7788 are each surrounded by a stellar halo that extends out to 5 arcmin (∼ 3.4 parsecs) radius. It is suggested that these halos form in response to large-scale mass ejection early in the evolution of the clusters, as predicted by models. In contrast, blue main sequence stars in NGC 7790 are traced out to a radius of ∼ 7.5′, with no evidence of a halo. It is suggested that all three clusters may have originated in the same star-forming complex, but not in the same giant molecular cloud. Accepted by Astrophysical Journal http://arxiv.org/pdf/1211.6398

New Brown Dwarf Disks in Upper Scorpius Observed with WISE P. Dawson1, A. Scholz1, T.P. Ray1, K.A. Marsh2, K. Wood3, A. Natta1,4, D. Padgett5 and M.E. Ressler6 1 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland 2 School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK 3 School of Physics and Astronomy, University of St. Andrews, North Haugh, St.Andrews KY16 9SS, UK 4 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 5 Goddard Space Flight Center, Greenbelt, MD 20771, USA

19 6 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA E-mail contact: pdawson at cp.dias.ie We present a census of the disk population for UKIDSS selected brown dwarfs in the 5-10 Myr old Upper Scorpius OB association. For 116 objects originally identiﬁed in UKIDSS, the majority of them not studied in previous publications, we obtain photometry from the WISE database. The resulting colour-magnitude and colour-colour plots clearly show two separate populations of objects, interpreted as brown dwarfs with disks (class II) and without disks (class III). We identify 27 class II brown dwarfs, 14 of them not previously known. This disk fraction (27 out of 116 or 23%) among brown dwarfs was found to be similar to results for K/M stars in Upper Scorpius, suggesting that the lifetimes of disks are independent of the mass of the central object for low-mass stars and brown dwarfs. 5 out of 27 disks (19%) lack excess at 3.4 and 4.6 µm and are potential transition disks (i.e. are in transition from class II to class III). The transition disk fraction is comparable to low-mass stars. We estimate that the timescale for a typical transition from class II to class III is less than 0.4 Myr for brown dwarfs. These results suggest that the evolution of brown dwarf disks mirrors the behaviour of disks around low-mass stars, with disk lifetimes on the order of 5-10 Myr and a disk clearing timescale signiﬁcantly shorter than 1 Myr. Accepted by MNRAS http://arxiv.org/pdf/1211.4484

CFBDSIR2149-0403: a 4-7 Jupiter-mass free-floating planet in the young moving group AB Doradus ? P. Delorme 1, J. Gagné 2, L. Malo 2, C. Reylé 3 , E. Artigau 2, L. Albert 2, T. Forveille 1, X. Delfosse 1, F. Allard 4, D. Homeier 4 1UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno- ble, F-38041, France. 2Département de physique and Observatoire du Mont Mégantic, Universitéde Montréal, C.P. 6128, Succursale Centre- Ville, Montréal, QC H3C 3J7, Canada 3 Universitéde Franche Comté, Institut UTINAM CNRS 6213, Observatoire des Sciences de l’Univers THETA de Franche-Comté, Observatoire de Besan¸con, BP 1615, 25010 Besan¸con Cedex, France 4C.R.A.L. (UMR 5574 CNRS), Ecole Normale Supérieure, 69364 Lyon Cedex 07, France E-mail contact: philippe.delorme at obs.ujf-grenoble.fr Using the CFBDSIR wide field survey for brown dwarfs, we identified CFBDSIRJ214947.2-040308.9, a late T dwarf with atypically red J − KS colour. We obtained an X-Shooter spectra, with signal detectable from 0.8 µm to 2.3 µm, which confirmed a T7 spectral type with an enhanced Ks-band flux indicative of a potentially low-gravity, young, object. The comparison of our near infrared spectrum with atmosphere models, for solar metallicity, shows that CFBDSIRJ214947.2-040308.9 is probably a 650-750K, log g=3.75-4.0 substellar object. Using evolution models, this translates into a planetary mass object, with an age in the 20-200 Myr range. An independent Bayesian analysis from proper motion measurements results in a 87% probability that this free-floating planet is a member of the 50-120 Myr old AB Doradus moving group, which strengthens the spectroscopic youth diagnosis. By combining our atmospheric characterisation with the age and metallicity constraints arising from the probable membership to the AB Doradus moving group, we find that CFBDSIRJ214947.2-040308.9 is probably a 4-7 Jupiter masses free-floating planet with an effective temperature of ∼700K and a logg of ∼4.0, typical of the late T-type exoplanets that are targeted by direct imaging. We stress that this object could be used as a benchmark for understanding the physics of the similar T-type exoplanets that will be discovered by the upcoming high contrast imagers. Accepted by A&A (548:A26) http://arxiv.org/pdf/1210.0305

Multi-wavelength study of triggered star formation around mid-infrared bubble N14 L. K. Dewangan1,2 and D. K. Ojha1 1 Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India 2 Centro de Astrof´ısica da Universidade do Porto, Rua das Estrelas, 4150-762 s/n Porto, Portugal

20 E-mail contact: Lokesh.Dewangan at astro.up.pt We present multi-wavelength analysis around mid-infrared (MIR) bubble N14 to probe the signature of triggered star formation as well as the formation of new massive star(s) and/or cluster(s) on the borders of the bubble by the expansion of the H ii region. Spitzer-IRAC ratio maps reveal that the bubble is traced by the polycyclic aromatic hydrocarbon (PAH) emission following an almost circular morphology except in the south-west direction towards the low molecular density environment. The observational signatures of the collected molecular and cold dust material have been found around the bubble. We have detected 418 young stellar objects (YSOs) in the selected region around the bubble N14. Interestingly, the detected YSO clusters are associated with the collected molecular and cold dust material on the borders of the bubble. One of the clusters is found with deeply embedded intermediate mass and massive Class I YSOs associated with one of the dense dust clumps in the east of the bubble N14. We do not ﬁnd a good agreement between the dynamical age of the H ii region and the fragmentation time of the accumulated molecular materials to explain possible “collect-and-collapse” process around the bubble N14. Therefore, we suggest the possibility of triggered star formation by compression of the pre-existing dense clumps by the shock wave and/or small scale Jeans gravitational instabilities in the collected materials. We have also investigated 5 young massive embedded protostars (8 to 10 M⊙) and 15 intermediate mass (3 to 7 M⊙) Class I YSOs which are associated with the dust and molecular fragmented clumps at the borders of the bubble. We conclude that the expansion of the H ii region is also leading to the formation of these intermediate and massive Class I YSOs around the bubble N14. Accepted by the MNRAS http://arxiv.org/pdf/1211.4079

Tracing High-Energy Radiation from T Tauri Stars Using Mid-Infrared Neon Emission from Disks C. Espaillat1,2, L. Ingleby3, E. Furlan4,5, M. McClure3, A. Spatzier6, J. Nieusma3, N. Calvet3, E. Bergin3, L. Hartmann3, J. M. Miller3 and J. Muzerolle7 1 Sagan Fellow 2 Harvard-Smithonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA, 02138, USA 3 Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109, USA 4 National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ, 85719, USA 5 Visitor at the Infrared Processing and Analysis Center, Caltech, 770 S. Wilson Ave., Pasadena, CA, 91125, USA 6 Oberlin College, Wright Laboratory of Physics, 110 N. Professor St., Oberlin, OH, 44074, USA 7 Space Telescope Institute, 3700 San Martin Drive, Baltimore, MD, 21218, USA E-mail contact: cespaillat at cfa.harvard.edu High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playing a crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS using high-resolution mid-infrared (MIR) Spitzer IRS Neon forbidden line detections in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We report three new detections of [Ne III] from CS Cha, SZ Cha, and T 54, doubling the known number of [Ne III] detections from TTS. Using [Ne III]-to-[Ne II] ratios in conjunction with X-ray emission measurements, we probe high-energy radiation from TTS. The majority of previously inferred [Ne III]/[Ne II] ratios based on [Ne III] line upper limits are significantly less than 1, pointing to the dominance of either X-ray radiation or soft Extreme-Ultraviolet (EUV) radiation in producing these lines. Here we report the first observational evidence for hard EUV dominated Ne forbidden line production in a T Tauri disk: [Ne III]/[Ne II]∼1 in SZ Cha. Our results provide a unique insight into the EUV emission from TTS, by suggesting that EUV radiation may dominate the creation of Ne forbidden lines, albeit in a minority of cases. Accepted by ApJ http://arxiv.org/pdf/1211.2335

The Star Formation Rate of Turbulent Magnetized Clouds: Comparing Theory, Simu- lations, and Observations Christoph Federrath1 and Ralf S. Klessen2

21 1 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia 2 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany E-mail contact: christoph.federrath at monash.edu The role of turbulence and magnetic fields is studied for star formation in molecular clouds. We derive and compare six theoretical models for the star formation rate (SFR)—the Krumholz & McKee (KM), Padoan & Nordlund (PN), and Hennebelle & Chabrier (HC) models, and three multi-freefall versions of these, suggested by HC—all based on integrals over the log-normal distribution of turbulent gas. We extend all theories to include magnetic fields, and show that the SFR depends on four basic parameters: (1) virial parameter αvir; (2) sonic Mach number M; (3) turbulent forcing 2 2 parameter b, which is a measure for the fraction of energy driven in compressive modes; and (4) plasma β =2MA/M with the Alfvén Mach number MA. We compare all six theories with MHD simulations, covering cloud masses of 6 300 to 4 × 10 M⊙ and Mach numbers M = 3–50 and MA = 1–∞, with solenoidal (b = 1/3), mixed (b = 0.4) and compressive turbulent (b = 1) forcings. We find that the SFR increases by a factor of four between M = 5 and 50 for compressive turbulent forcing and αvir ∼ 1. Comparing forcing parameters, we see that the SFR is more than 10× higher with compressive than solenoidal forcing for M = 10 simulations. The SFR and fragmentation are both reduced by a factor of two in strongly magnetized, trans-Alfvénic turbulence compared to hydrodynamic turbulence. All simulations are fit simultaneously by the multi-freefall KM and multi-freefall PN theories within a factor of two over two orders of magnitude in SFR. The simulated SFRs cover the range and correlation of SFR column density with gas column density observed in Galactic clouds, and agree well for star formation efficiencies SFE = 1%–10% and local efficiencies ǫ = 0.3–0.7 due to feedback. We conclude that the SFR is primarily controlled by interstellar turbulence, with a secondary effect coming from magnetic fields. Accepted by ApJ http://arxiv.org/pdf/1209.2856

On the Star Formation Efficiency of Turbulent Magnetized Clouds Christoph Federrath1 and Ralf S. Klessen2 1 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia 2 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany E-mail contact: christoph.federrath at monash.edu We study the star formation efficiency (SFE) in simulations and observations of turbulent, magnetized, molecular clouds. We find that the volumetric and column density probability distributions (PDFs) of our simulations with solenoidal, mixed, and compressive forcing of turbulence, sonic Mach numbers of 3–50, and magnetic fields in the super- to the trans-Alfvénic regime, all develop power-law tails of flattening slope with increasing SFE. The high- density tails of the PDFs are consistent with equivalent radial density profiles, ρ ∝ r−κ with κ ∼ 1.5–2.5, in agreement with observations. Studying velocity–size scalings, we find that all the simulations are consistent with the observed v ∝ ℓ1/2 scaling of supersonic turbulence, and seem to approach Kolmogorov turbulence with v ∝ ℓ1/3 below the sonic scale. The velocity–size scaling is, however, largely independent of the SFE. In contrast, the density–size and column density–size scalings are highly sensitive to star formation. We find that the power-law slope α of the density power α 2 −α spectrum, P3D(ρ, k) ∝ k , or equivalently the ∆-variance spectrum of column density, σ∆(Σ,ℓ) ∝ ℓ , switches sign from α < 0 for SFE ∼ 0 to α > 0 when star formation proceeds (SFE > 0). We provide a relation to compute the SFE from a measurement of α. Studying the literature, we find values ranging from α = −1.6 to +1.6 in observations covering scales from the large-scale atomic medium, over cold molecular clouds, down to dense star-forming cores. From those α values, we infer SFEs and find good agreement with independent measurements based on young stellar object (YSO) counts, where available. Our SFE–α relation provides an independent estimate of the SFE based on the column density map of a cloud alone, without requiring a priori knowledge of star-formation activity or YSO counts. Accepted by ApJ http://arxiv.org/pdf/1211.6433

22 AKARI/IRC 18 Micron Survey of Warm Debris Disks Hideaki Fujiwara1, Daisuke Ishihara2, Takashi Onaka3, Satoshi Takita4, Hirokazu Kataza4, Takuya Yamashita5, Misato Fukagawa6, Takafumi Ootsubo7, Takanori Hirao8, Keigo Enya4, Jonathan P. Marshall9, Glenn J. White10,11, Takao Nakagawa4, and Hiroshi Murakami4 1 Subaru Telescope, National Astronomical Observatory of Japan, 650 North Aohoku Place, Hilo, HI 96720, USA 2 Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan 3 Department of Astronomy, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 4 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan 5 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan 6 Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan 7 Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan 8 Research Institute of Science and Technology for Society, Japan Science and Technology Agency, Ks Gobancho Bldg, 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan 9 Departmento F´ısica Te´orica, Facultad de Ciencias, Universidad Aut´onoma de Madrid, Cantoblanco, 28049 Madrid, Spain 10 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK 11 Space Science & Technology Department, The Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK E-mail contact: hideaki at naoj.org

Context. Little is known about the properties of the warm (Tdust >∼ 150 K) debris disk material located close to the central star, which has a more direct link to the formation of terrestrial planets than the low temperature debris dust that has been detected to date. Aims. To discover new warm debris disk candidates that show large 18 micron excess and estimate the fraction of stars with excess based on the AKARI/IRC Mid-Infrared All-Sky Survey data. Methods. We have searched for point sources detected in the AKARI/IRC All-Sky Survey, which show a positional match with A-M dwarf stars in the Tycho-2 Spectral Type Catalogue and exhibit excess emission at 18 micron compared to that expected from the Ks magnitude in the 2MASS catalogue. Results. We find 24 warm debris candidates including 8 new candidates among A-K stars. The apparent debris disk frequency is estimated to be 2.8 ± 0.6%. We also find that A stars and solar-type FGK stars have different characteristics of the inner component of the identified debris disk candidates — while debris disks around A stars are cooler and consistent with steady-state evolutionary model of debris disks, those around FGK stars tend to be warmer and cannot be explained by the steady-state model. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1211.6365

Herschel far-infrared observations of the Carina Nebula complex II: The embedded young stellar and protostellar population B. Gaczkowski1, T. Preibisch1, T. Ratzka1, V. Roccatagliata1, H. Ohlendorf1 and H. Zinnecker2,3 1 Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany 2 Deutsches SOFIA Institut, Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany 3 NASA-Ames Research Center, MS 211-3, Moffett Field, CA 94035, USA E-mail contact: preibisch at usm.uni-muenchen.de Context: The Carina Nebula represents one of the largest and most active star forming regions known in our Galaxy. It contains numerous very massive (M ≥ 40 M⊙) stars that strongly affect the surrounding clouds by their ionizing radiation and stellar winds. Aims: Our recently obtained Herschel PACS & SPIRE far-infrared maps cover the full area (≈ 8.7 deg2) of the Carina Nebula complex and reveal the population of deeply embedded young stellar objects, most of which are not yet visible in the mid- or near-infrared. Methods: We study the properties of the 642 objects that are independently detected as point-like sources in at least

23 two of the five Herschel bands. For those objects that can be identified with apparently single Spitzer counterparts, we use radiative transfer models to derive information about the basic stellar and circumstellar parameters. Results: We find that about 75% of the Herschel-detected YSOs are Class 0 protostars. The luminosities of the Herschel-detected YSOs with SED fits are restricted to values of ≤ 5400 L⊙, their masses (estimated from the radiative transfer modeling) range from ≈ 1 M⊙ to ≈ 10 M⊙. Taking the observational limits into account and extrapolating the observed number of Herschel-detected protostars over the stellar initial mass function suggest that the star formation rate of the CNC is ∼ 0.017 M⊙/year. The spatial distribution of the Herschel YSO candidates is highly inhomogeneous and does not follow the distribution of cloud mass. Rather, most Herschel YSO candidates are found at the irradiated edges of clouds and pillars. The far-infrared fluxes of the famous object η Car are about a factor of two lower than expected from observations with the Infrared Space Observatory obtained 15 years ago; this difference may be a consequence of dynamical changes in the circumstellar dust in the Homunculus Nebula around η Car. Conclusions: The currently ongoing star formation process forms only low-mass and intermediate-mass stars, but no massive (M ≥ 20 M⊙) stars. The characteristic spatial configuration of the YSOs provides support to the picture that the formation of this latest stellar generation was triggered by the advancing ionization fronts. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1211.2995 High-quality preprints can be obtained from http://www.usm.uni-muenchen.de/people/preibisch/publications.html

Two massive stars possibly ejected from NGC 3603 via a three-body encounter V. V. Gvaramadze1,2, A. Y. Kniazev3,4,1, A.-N. Chene5,6, and O. Schnurr7 1 Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskij Pr. 13, Moscow 119992, Russia 2 Isaac Newton Institute of Chile, Moscow Branch, Universitetskij Pr. 13, Moscow 119992, Russia 3 South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa 4 Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa 5 Departamento de F´ısica y Astronom´ıa, Universidad de Valparaso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, Chile 6 Departamento de Astronom´ıa, Universidad de Concepción, Casilla 160-C, Chile 7 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany E-mail contact: vgvaram at mx.iki.rssi.ru We report the discovery of a bow-shock-producing star in the vicinity of the young massive star cluster NGC 3603 using archival data of the Spitzer Space Telescope. Follow-up optical spectroscopy of this star with Gemini-South led to its classification as O6 V. The orientation of the bow shock and the distance to the star (based on its spectral type) suggest that the star was expelled from the cluster, while the young age of the cluster (∼2 Myr) implies that the ejection was caused by a dynamical few-body encounter in the cluster’s core. The relative position on the sky of the O6 V star and a recently discovered O2 If*/WN6 star (located on the opposite side of NGC 3603) allows us to propose that both objects were ejected from the cluster via the same dynamical event – a three-body encounter between a single (O6 V) star and a massive binary (now the O2 If*/WN6 star). If our proposal is correct, then one can ”weigh” the O2 If*/WN6 star using the conservation of the linear momentum. Given a mass of the O6 V star of 30 M⊙, we found that at the moment of ejection the mass of the O2 If*/WN6 star was 175 M⊙. Moreover, the observed X-ray luminosity of the O2 If*/WN6 star (typical of a single star) suggests that the components of this originally binary system have merged (e.g., because of encounter hardening). Accepted by MNRAS Letters http://arxiv.org/pdf/1211.5926

Chemical and Physical Conditions in Molecular Cloud Core DC 000.4-19.5 (SL42) in Corona Australis E. Hardegree-Ullman1, J. Harju2,3, M. Juvela3, O. Sipil¨a3, D. C. B. Whittet1 and S. Hotzel4,5

24 1 New York Center for Astrobiology and Department of Physics, Applied Physics, and Astronomy, Rensselaer Poly- technic Institute, 110 Eighth Street, Troy, NY 12180, USA 2 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, 21500, Piikkiö, Finland 3 Department of Physics, PO Box 64, 00014 University of Helsinki, Finland 4 Observatory, 00014 University of Helsinki, Finland 5 GRS mbH, 50667 Cologne, Germany E-mail contact: hardee at rpi.edu Chemical reactions in starless molecular clouds are heavily dependent on interactions between gas phase material and solid phase dust and ices. We have observed the abundance and distribution of molecular gases in the cold, starless core DC 000.4-19.5 (SL42) in Corona Australis using data from the Swedish-ESO Submillimeter Telescope (SEST). 18 + We present column density maps determined from measurements of C O (J = 2 − 1, 1 − 0) and N2H (J = 1 − 0) emission features. Herschel data of the same region allow a direct comparison to the dust component of the cloud core and provide evidence for gas phase depletion of CO at the highest extinctions. The dust color temperature in the core calculated from Herschel maps ranges from roughly 10.7 to 14.0 K. This range agrees with the previous determinations from Infrared Space Observatory (ISO) and Planck observations. The column density profile of the core can be fitted with a Plummer-like density distribution approaching n(r) ∼ r−2 at large distances. The core structure deviates clearly from a critical Bonnor-Ebert sphere. Instead, the core appears to be gravitationally bound and to lack thermal and turbulent support against the pressure of the surrounding low-density material: it may therefore be in the process of slow contraction. We test two chemical models and find that a steady-state depletion model (Keto and Caselli 2008, 18 18 2010) agrees with the observed C O column density profile and the observed N(C O) vs. AV relationship. Accepted by The Astrophysical Journal

Ammonia in the hot core W51-IRS2: 12 new maser lines and a maser component with a velocity drift C. Henkel1,2, T. L. Wilson3, H. Asiri2, R. Mauersberger4 1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany 2 Astronomy Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, Saudi Arabia 3 Naval Research Laboratory, Code 7210, Washington, DC 20375, USA 4 Joint ALMA Observatory, Avda. Alonso de Córdova 3107, Vitacura, Santiago de Chile, Chile E-mail contact: chenkel at mpifr-bonn.mpg.de

With the 100-m telescope at Effelsberg, 19 ammonia (NH3) maser lines have been detected toward the prominent massive star forming region W51-IRS2. Twelve of these inversion lines, the (J, K) = (6,2), (5,3), (7,4), (8,5), (7,6), (8,6), (7,7), (9,7), (10,7), (9,9), (10,9), and (12,12) transitions, are classified as masers for the first time in outer space. The (7,7) line is the rst metastable (J = K) para-NH3 maser ever reported. All detected masers are related to highly excited inversion doublets. The (5,4) maser originates from an inversion doublet ∼340 K above the ground state, while the (12,12) transition, at ∼1450 K, is the most highly excited NH3 maser line so far known. Strong variability is seen not only in ortho- but also in para-NH3 transitions. Bright narrow emission features are observed, for the first −1 time, in (mostly) ortho-ammonia transitions, at VLSR ∼ 45 km s , well separated from the quasi-thermal emission near 60 km s−1. These features were absent ∼25 years ago and show a velocity drift of about +0.2 km s−1 yr−1. The component is likely related to the SiO maser source in W51-IRS2 and a possible scenario explaining the velocity drift is outlined. The 57 km s−1 component of the (9,6) maser line is found to be strongly linearly polarized. Maser emission in the (J, K) to (J +1,K) inversion doublets is strictly forbidden by selection rules for electric dipole transitions in the ground vibrational state. However, such pairs (and even triplets with (J +2,K)) are common toward W51-IRS2. Similarities in line widths and velocities indicate that such groups of maser lines arise from the same regions, which can be explained by pumping through vibrational excitation. The large number of NH3 maser lines in W51-IRS2 is most likely related to the exceptionally high kinetic temperature and NH3 column density of this young massive star forming region. Accepted for publication in Astronomy & Astrophysics http://arxiv.org/pdf/1211.2484

25 Protostellar Feedback and Final Mass of the Second-Generation Primordial Stars Takashi Hosokawa1,2, Naoki Yoshida1,3, Kazuyuki Omukai4 and Harold W. Yorke2 1 Department of Physics, University of Tokyo, Japan 2 Jet Propulsion Laboratory, California Institute of Technology, USA 3 Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Japan 4 Department of Physics, Kyoto University, Japan E-mail contact: takashi.hosokawa at phys.s.u-tokyo.ac.jp The first stars in the universe ionized the ambient primordial gas through various feedback processes. “Second- generation” primordial stars potentially form from this disturbed gas after its recombination. In this Letter, we study the late formation stage of such second-generation stars, where a large amount of gas accretes onto the protostar and the final stellar mass is determined when the accretion terminates. We directly compute the complex interplay between the accretion flow and stellar ultraviolet (UV) radiation, performing radiation-hydrodynamic simulations coupled with stellar evolution calculations. Because of more efficient H2 and HD cooling in the pre-stellar stage, the accretion rates onto the star are ten times lower than in the case of the formation of the first stars. The lower accretion rates and envelope density result in the occurrence of an expanding bipolar HII region at a lower protostellar mass M∗ ≃ 10 M⊙, which blows out the circumstellar material, thereby quenching the mass supply from the envelope to the accretion disk. At the same time the disk loses mass due to photoevaporation by the growing star. In our fiducial case the stellar UV feedback terminates mass accretion onto the star at M∗ ≃ 17 M⊙. Although the derived masses of the second-generation primordial stars are systematically lower than those of the first generation, the difference is within a factor of only a few. Our results suggest a new scenario, whereby the majority of the primordial stars are born as massive stars with tens of solar masses, regardless of their generations. Accepted by ApJ Letters (760:L37) http://adsabs.harvard.edu/abs/2012ApJ...760L..37H http://arxiv.org/pdf/1210.3035

CO bandhead emission of massive young stellar objects: determining disc properties J. D. Ilee1, H. E. Wheelwright2, R. D. Oudmaijer1, W. J. de Wit3, L. T. Maud1, M. G. Hoare1, S. L. Lumsden1, T. J. T. Moore4, J. S. Urquhart2 and J. C. Mottram5 1 School of Physics and Astronomy, EC Stoner Building, University of Leeds, Leeds, LS2 9JT, UK 2 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121, Bonn, Germany 3 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile 4 Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD 5 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, the Netherlands E-mail contact: pyjdi at leeds.ac.uk Massive stars play an important role in many areas of astrophysics, but numerous details regarding their formation remain unclear. In this paper we present and analyse high resolution (R ∼ 30,000) near-infrared 2.3 micron spectra of 20 massive young stellar objects from the RMS database, in the largest such study of CO first overtone bandhead emission to date. We fit the emission under the assumption it originates from a circumstellar disc in Keplerian rotation. We explore three approaches to modelling the physical conditions within the disc - a disc heated mainly via irradiation from the central star, a disc heated mainly via viscosity, and a disc in which the temperature and density are described analytically. We find that the models described by heating mechanisms are inappropriate because they do not provide good fits to the CO emission spectra. We therefore restrict our analysis to the analytic model, and obtain good fits to all objects that possess sufficiently strong CO emission, suggesting circumstellar discs are the source of this emission. On average, the temperature and density structure of the discs correspond to geometrically thin discs, spread across a wide range of inclinations. Essentially all the discs are located within the dust sublimation radius, providing strong evidence that the CO emission originates close to the central protostar, on astronomical unit scales. In addition, we show that the objects in our sample appear no different to the general population of MYSOs in the RMS database, based on their near- and mid-infrared colours. The combination of observations of a large sample of MYSOs with CO bandhead emission and our detailed modelling provide compelling evidence of the presence of small scale gaseous discs

26 around such objects, supporting the scenario in which massive stars form via disc accretion. Accepted by MNRAS http://arxiv.org/pdf/1212.0554

The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591 K. G. Johnston1, D. S. Shepherd2, T. P. Robitaille1 and K. Wood3 1 Max Planck Institute for Astronomy, Konigstuhl 17, D-69117 Heidelberg, Germany 2 National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, New Mexico 87801, USA 3 School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK E-mail contact: johnston at mpia.de Context. While it is currently unclear from a theoretical standpoint which forces and processes dominate the formation of high-mass stars, and hence determine the mode in which they form, much of the recent observational evidence suggests that massive stars are born in a similar manner to their low-mass counterparts. 5 Aims. This paper aims to investigate the hypothesis that the embedded luminous star AFGL 2591-VLA 3 (2.3 x 10 L⊙ at 3.33 kpc) is forming according to a scaled-up version of a low-mass star formation scenario. Methods. We present multi-configuration Very Large Array 3.6 cm and 7 mm, as well as Combined Array for Research in Millimeter Astronomy C18O and 3 mm continuum observations to investigate the morphology and kinematics of the ionized gas, dust, and molecular gas around AFGL 2591. We also compare our results to ancillary Gemini North near-IR images, and model the near-IR to sub-mm Spectral Energy distribution (SED) and Two Micron All Sky Survey (2MASS) image profiles of AFGL 2591 using a Monte-Carlo dust continuum radiative transfer code. Results. The observed 3.6 cm images uncover for the first time that the central powering source AFGL 2591-VLA 3 has a compact core plus collimated jet morphology, extending 4000 AU eastward from the central source with an opening angle of < 10◦ at this radius. However, at 7 mm VLA 3 does not show a jet morphology, but instead compact (< 500 AU) emission, some of which (< 0.57 mJy of 2.9 mJy) is estimated to be from dust emission. The spectral index of AFGL 2591-VLA 3 between 3.6 cm and 7 mm was found to be between 0.4 and 0.5, similar to that of an ionized wind. If the 3.6 cm emission is modelled as an ionized jet, the jet has almost enough momentum to drive the larger-scale flow. However, assuming a shock efficiency of 10%, the momentum rate of the jet is not sufficient to ionize itself via only shocks, and thus a significant portion of the emission is instead likely created in a photoionized wind. The C18O emission uncovers dense entrained material in the outflow(s) from these young stars. The main features of the SED and 2MASS images of AFGL 2591-VLA 3 are also reproduced by our model dust geometry of a rotationally flattened envelope with and without a disk. Conclusions. The above results are consistent with a picture of massive star formation similar to that seen for low-mass protostars. However, within its envelope, AFGL 2591-VLA 3 contains at least four other young stars, constituting a small cluster. Therefore it appears that AFGL 2591-VLA 3 may be able to source its accreting material from a shared gas reservoir while still exhibiting the phenomena expected during the formation of low-mass stars. Accepted by A&A http://www.mpia.de/homes/johnston/Johnston2012.pdf

High-dynamic-range extinction mapping of infrared dark clouds: Dependence of density variance with sonic Mach number in molecular clouds Jouni Kainulainen1 and Jonathan C. Tan2,3 1 MPIA Heidelberg, Germany 2 Dept. of Astronomy, University of Florida, Gainesville, USA 3 Dept. of Physics, University of Florida, Gainesville, USA E-mail contact: jtkainul at mpia.de Measuring the mass distribution of infrared dark clouds (IRDCs) over the wide dynamic range of their column densities is a fundamental obstacle in determining the initial conditions of high-mass star formation and star cluster formation. We present a new technique to derive high-dynamic-range, arcsecond-scale resolution column density data for IRDCs

27 and demonstrate the potential of such data in measuring the density variance - sonic Mach number relation in molecular clouds. We combine near-infrared data from the UKIDSS/Galactic Plane Survey with mid-infrared data from the Spitzer/GLIMPSE survey to derive dust extinction maps for a sample of ten IRDCs. We then examine the linewidths of the IRDCs using 13CO line emission data from the FCRAO/Galactic Ring Survey and derive a column density - sonic Mach number relation for them. For comparison, we also examine the relation in a sample of nearby molecular clouds. The presented column density mapping technique provides a very capable, temperature independent tool for mapping IRDCs over the column density range equivalent to AV ≃ 1 − 100 mag at a resolution of 2”. Using the data provided by the technique, we present the first direct measurement of the relationship between the column density dispersion, σN/hNi, and sonic Mach number, Ms, in molecular clouds. We detect correlation between the variables with about 3-σ confidence. We derive the relation σN/hNi ≈ (0.047 ± 0.016)Ms, which is suggestive of the +0.37 correlation coefficient between the volume density and sonic Mach number, σρ/hρi ≈ (0.20−0.22)Ms, in which the quoted uncertainties indicate the 3-σ range. When coupled with the results of recent numerical works, the existence of the correlation supports the picture of weak correlation between the magnetic field strength and density in molecular clouds (i.e., B ∝ ρ0.5). While our results remain suggestive because of the small number of clouds in our demonstration sample, the analysis can be improved by extending the study to a larger number of clouds. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1210.8130

Mean Motion Resonances in Exoplanet Systems: Investigation into Nodding Behavior Jacob A. Ketchum1, Fred C. Adams1,2 and Anthony M. Bloch3 1 Physics Department, University of Michigan, Ann Arbor, MI 48109, USA 2 Astronomy Department, University of Michigan, Ann Arbor, MI 48109, USA 3 Department of Mathematics, University of Michigan, Ann Arbor, MI 48109, USA E-mail contact: fca at umich.edu Motivated by the large number of extrasolar planetary systems that are near mean motion resonances, this paper explores a related type of dynamical behavior known as “nodding”. Here, the resonance angle of a planetary system executes libration (oscillatory motion) for several cycles, circulates for one or more cycles, and then enters once again into libration. This type of complicated dynamics can aﬀect our interpretation of observed planetary systems that are in or near mean motion resonance. This work shows that planetary systems in (near) mean motion resonance can exhibit nodding behavior, and outlines the portion of parameter space where it occurs. This problem is addressed using both full numerical integrations of the planetary systems and via model equations obtained through expansions of the disturbing function. In the latter approach, we identify the relevant terms that allow for nodding. The two approaches are in agreement, and show that nodding often occurs when a small body is in an external mean motion resonance with a larger planet. As a result, the nodding phenomenon can be important for interpreting observations of transit timing variations, where the existence of smaller bodies is inferred through their eﬀects on larger, observed transiting planets. For example, in actively nodding planetary systems, both the amplitude and frequency of the transit timing variations depend on the observational time window. Accepted by The Astrophysical Journal http://arxiv.org/pdf/1211.3078

On the effects of optically thick gas (disks) around massive stars Rolf Kuiper1 and Harold W. Yorke1 1 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA E-mail contact: Rolf.Kuiper at jpl.nasa.gov Numerical simulations have shown that the often cited radiation pressure barrier to accretion onto massive stars can be circumvented, when the radiation field is highly anisotropic in the presence of a circumstellar accretion disk with high optical depth. Here, these studies of the so-called flashlight effect are expanded by including the opacity of the innermost dust-free but potentially optically thick gas regions around forming massive stars. In addition to frequency-

28 dependent opacities for the dust grains, we use temperature- and density-dependent Planck- and Rosseland mean opacities for the gas. The simulations show that the innermost dust-free parts of the accretion disks are optically thick to the stellar radiation over a substantial fraction of the solid angle above and below the disk’s midplane. The temperature in the shielded disk region decreases faster with radius than in a comparison simulation with a lower constant gas opacity, and the dust sublimation front is shifted to smaller radii. The shielding by the dust-free gas in the inner disk thus contributes to an enhanced flashlight effect, which ultimately results in a smaller opening angle of the radiation pressure driven outflow and in a much longer timescale of sustained feeding of the circumstellar disk by the molecular cloud core. We conclude that it is necessary to properly account for the opacity of the inner dust-free disk regions around forming massive stars in order to correctly assess the effectiveness of the flashlight effect, the opening angle of radiation pressure driven outflows, and the lifetime and morphological evolution of the accretion disk. Accepted by ApJ http://arxiv.org/pdf/1211.6432

Filamentary Star Formation: Observing the Evolution toward Flattened Envelopes Katherine Lee1, Leslie Looney1, Doug Johnstone2,3, John Tobin4 1 Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green St, Urbana, IL 61801, USA 2 Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada 3 NRC-Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada 4 Hubble Fellow, National Radio Astronomy Observatory, Charlottesville, VA 22903, USA E-mail contact: ijlee9 at illinois.edu Filamentary structures are ubiquitous from large-scale molecular clouds (few parsecs) to small-scale circumstellar envelopes around Class 0 sources (∼1000 AU to ∼0.1 pc). In particular, recent observations with the Herschel Space Observatory emphasize the importance of large-scale filaments (few parsecs) and star formation. The small-scale flattened envelopes around Class 0 sources are reminiscent of the large-scale filaments. We propose an observationally derived scenario for filamentary star formation that describes the evolution of filaments as part of the process for formation of cores and circumstellar envelopes. If such a scenario is correct, small-scale filamentary structures (0.1 pc in length) with higher densities embedded in starless cores should exist, although to date almost all the interferometers have failed to observe such structures. We perform synthetic observations of filaments at the prestellar stage by modeling the known Class 0 flattened envelope in L1157 using both the Combined Array for Research in Millimeter- wave Astronomy (CARMA) and the Atacama Large Millimeter/Submillimeter Array (ALMA). We show that with reasonable estimates for the column density through the flattened envelope, the CARMA D-array at 3mm wavelengths is not able to detect such filamentary structure, so previous studies would not have detected them. However, the substructures may be detected with CARMA D+E array at 3 mm and CARMA E array at 1 mm as a result of more appropriate resolution and sensitivity. ALMA is also capable of detecting the substructures and showing the structures in detail compared to the CARMA results with its unprecedented sensitivity. Such detection will confirm the new proposed paradigm of non-spherical star formation. Accepted by ApJ http://arxiv.org/pdf/1211.0670

The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation Beomdu Lim1, Moo-Young Chun2, Hwankyung Sung1, Byeong-Gon Park2, Jae-Joon Lee2, Sangmo T. Sohn3, Hyeonoh Hur1, and Michael S. Bessell4 1 Department of Astronomy and Space Science, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747, Korea 2 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yusung-gu, Daejeon, Korea 3 Space Telescope Science Institute, Baltimore, MD 21218, USA 4 Research School of Astronomy and Astrophysics, Australian National University, MSO, Cotter Road, Weston, ACT 2611, Australia E-mail contact: bdlim1210 at sju.ac.kr

29 Westerlund 1 is the most important starburst cluster in the Galaxy due to its massive star content. We have performed BVIc and JKs photometry to investigate the initial mass function (IMF). By comparing the observed color with the spectral type - intrinsic color relation, we obtain the mean interstellar reddening of =4.19±0.23 and =1.70 ± 0.21. Due to the heavy extinction toward the cluster, the zero-age main sequence ﬁtting method based on optical photometry proved to be inappropriate for the distance determination, while the near-infrared photometry gave a reliable distance to the cluster – 3.8 kpc from the empirical relation. Using the recent theoretical stellar evolution models with rotation, the age of the cluster is estimated to be 5.0±1.0 Myr. We derived the IMF in the massive part and obtained a fairly shallow slope of Γ = −0.8 ± 0.1. The integration of the IMF gave a total mass for the cluster in excess of 5.0 × 104 solar mass. The IMF shows a clear radial variation indicating the presence of mass segregation. We also discuss the possible star formation history of Westerlund 1 from the presence of red supergiants and relatively low-luminosity yellow hypergiants. Accepted by the Astronomical Journal http://arxiv.org/pdf/1211.5832

A Comparison of Approaches in Fitting Continuum SEDs Yao Liu1, 2, 3, David Madlener3, Sebastian Wolf3, Hongchi Wang1 1 Purple Mountain Observatory, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008, China 2 Graduate School of the Chinese Academy of Sciences, Beijing 100080, China 3 Institut für Theoretische Physik und Astrophysik, Universität zu Kiel, Leibnizstr. 15, 24118 Kiel, Germany E-mail contact: yliu at pmo.ac.cn We present a detailed comparison of two approaches, the use of a pre-calculated database and simulated annealing (SA), for fitting the continuum spectral energy distribution (SED) of astrophysical objects whose appearance is dominated by surrounding dust. While pre-calculated databases are commonly used to model SED data, only few studies to date employed SA due to its unclear accuracy and convergence time for this specific problem. From a methodological point of view, different approaches lead to different fitting quality, demand on computational resources and calculation time. We compare the fitting quality and computational costs of these two approaches for the task of SED fitting to provide a guide to the practitioner to find a compromise between desired accuracy and available resources. To reduce uncertainties inherent to real datasets, we introduce a reference model resembling a typical circumstellar system with 10 free parameters. We derive the SED of the reference model with our code MC3D at 78 logarithmically distributed wavelengths in the range [0.3 µm, 1.3 mm] and use this setup to simulate SEDs for the database and SA. Our result shows directly the applicability of SA in the field of SED modeling, since the algorithm regularly finds better solutions to the optimization problem than a pre-calculated database. As both methods have advantages and shortcomings, a hybrid approach is preferable. While the database provides an approximate fit and overall probability distributions for all parameters deduced using Bayesian analysis, SA can be used to improve upon the results returned by the model grid. Accepted by Research in Astronomy and Astrophysics http://arxiv.org/pdf/1211.4309

ALMA and VLA observations of the outflows in IRAS 16293-2422 Laurent Loinard1,2, Luis A. Zapata1, Luis F. Rodriguez1, Gerardo Pech1, Claire J. Chandler3, Crystal L. Brogan4, David J. Wilner5, Paul T. P. Ho5,6, Bérengère Parise2, Lee W. Hartmann7, Zhaohuan Zhu8, Satoko Takahashi6, and Alfonso Trejo6 1 Centro de Radiostronom´ıay Astrof´ısica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán, México 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 3 National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA 4 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA 5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 6 Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan

30 7 Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109, USA 8 Department of Astrophysical Sciences, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544, USA We present ALMA and VLA observations of the molecular and ionized gas at 0.1′′–0.3′′ resolution in the Class 0 protostellar system IRAS 16293-2422. These data clarify the origins of the protostellar outflows from the deeply embedded sources in this complex region. Source A2 is confirmed to be at the origin of the well known large scale northeast–south-west flow. The most recent VLA observations reveal a new ejection from that protostar, demonstrating that it drives an episodic jet. The central compact part of the other known large scale flow in the system, oriented roughly east-west, is well delineated by the CO (6-5) emission imaged with ALMA and is confirmed to be driven from within component A. Finally, a one-sided blueshifted bubble-like outflow structure is detected here for the first time from source B to the north-west of the system. Its very short dynamical timescale (∼ 200 yr), low velocity, and moderate collimation support the idea that source B is the youngest object in the system, and possibly one of the youngest protostars known. Accepted by MNRAS http://arxiv.org/pdf/1211.4744

Herschel CHESS discovery of the fossil cloud that gave birth to the Trapezium and Orion KL Ana López-Sepulcre1, Mihkel Kama2, Cecilia Ceccarelli1, Carsten Dominik2,3, Emmanuel Caux4,5, Asunción Fuente6 and Tomás Alonso-Albi6 1 UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno- ble, F-38041, France 2 Astronomical Institute Anton Pannekoek, University of Amsterdam, Amsterdam, The Netherlands 3 Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands 4 Universitéde Toulouse, UPS-OMP, IRAP, Toulouse, France 5 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France 6 Observatorio Astronómico Nacional, P.O. Box 112, 28803 Alcaláde Henares, Madrid, Spain E-mail contact: ana.sepulcre at obs.ujf-grenoble.fr Context: The Orion A molecular complex is a nearby (420 pc), very well studied stellar nursery that is believed to contain examples of triggered star formation. Aims: As part of the Herschel Guaranteed Time Key Programme CHESS, we present the discovery of a diffuse gas component in the foreground of the intermediate-mass protostar OMC-2 FIR 4, located in the Orion A region. Methods: Making use of the full HIFI spectrum of OMC-2 FIR 4 obtained in CHESS, we detected several ground-state + + + lines from OH , H2O , HF, and CH , all of them seen in absorption against the dust continuum emission of the protostar’s envelope. We derived column densities for each species, as well as an upper limit to the column density of + the undetected H3O . In order to model and characterise the foreground cloud, we used the Meudon PDR code to run a homogeneous grid of models that spans a reasonable range of densities, visual extinctions, cosmic ray ionisation rates and far-ultraviolet (FUV) radiation fields, and studied the implications of adopting the Orion Nebula extinction properties instead of the standard interstellar medium ones. Results: The detected absorption lines peak at a velocity of 9 km s−1, which is blue-shifted by 2 km s−1 with respect −1 to the systemic velocity of OMC-2 FIR 4 (VLSR = 11.4 km s ). The results of our modelling indicate that the −3 foreground cloud is composed of predominantly neutral diffuse gas (nH = 100 cm ) and is heavily irradiated by an external source of FUV that most likely arises from the nearby Trapezium OB association. The cloud is 6 pc thick and bears many similarities with the so-called C+ interface between Orion-KL and the Trapezium cluster, 2 pc south of OMC-2 FIR 4. Conclusions: We conclude that the foreground cloud we detected is an extension of the C+ interface seen in the direction of Orion KL, and interpret it to be the remains of the parental cloud of OMC-1, which extends from OMC-1 up to OMC-2. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1211.5772

31 Millimeter Emission Structure in the first ALMA Image of the AU Mic Debris Disk Meredith A. MacGregor1, David J. Wilner1, Katherine A. Rosenfeld1, Sean M. Andrews1, Brenda Matthews2, A. Meredith Hughes3, Mark Booth2,4, Eugene Chiang3, James R. Graham3,5, Paul Kalas3,6, Grant Kennedy7, and Bruce Sibthorpe8 1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 2 Herzberg Institute of Astrophysics, 5072 West Saanich Road, Victoria, BC V9E 2E7, Canada 3 Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720, USA 4 Deptarment of Physics & Astronomy, University of Victoria, 3800 Finnerty Rd., Victoria, BC, V8P 5C2, Canada 5 Dunlap Institute for Astronomy & Astrophysics, University of Toronto, Toronto, ON, Canada 6 SETI Institute, 189 Bernardo Ave., Mountain View, CA 94043, USA 7 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 8 SRON Netherlands Institute for Space Research, NL-9747 AD Groningen, The Netherlands We present 1.3 millimeter ALMA Cycle 0 observations of the edge-on debris disk around the nearby, ∼10 Myr-old, M-type star AU Mic. These observations obtain 0.6′′ (6 AU) resolution and reveal two distinct emission components: (1) the previously known dust belt that extends to a radius of 40 AU, and (2) a newly recognized central peak that remains unresolved. The cold dust belt of mass about 1 lunar mass is resolved in the radial direction with a rising emission profile that peaks sharply at the location of the outer edge of the ”birth ring” of planetesimals hypothesized to explain the midplane scattered light gradients. No significant asymmetries are discerned in the structure or position of this dust belt. The central peak identified in the ALMA image is 6 times brighter than the stellar photosphere, which indicates an additional emission process in the inner regions of the system. Emission from a stellar corona or activity may contribute, but the observations show no signs of temporal variations characteristic of radio-wave flares. We suggest that this central component may be dominated by dust emission from an inner planetesimal belt of mass about 0.01 lunar mass, consistent with a lack of emission shortward of 25 microns and a location <3 AU from the star. Future millimeter observations can test this assertion, as an inner dust belt should be readily separated from the central star at higher angular resolution. Accepted by ApJ Letters http://arxiv.org/pdf/1211.5148

Subaru Imaging of Asymmetric Features in a Transitional Disk in Upper Scorpius S. Mayama1,2, J. Hashimoto3, T. Muto4, T. Tsukagoshi5, N. Kusakabe3, M. Kuzuhara3,6, Y. Takahashi3,7, T. Kudo8, R. Dong9, M. Fukagawa10, M. Takami11, M. Momose5, J. P. Wisniewski27, K. Follette15, L. Abe12, E. Akiyama3, W. Brandner13, T. Brandt9, J. Carson14, S. Egner8, M. Feldt13, M. Goto29, C. A. Grady16,17,18, O. Guyon8, Y. Hayano2,8, M. Hayashi2,3, S. Hayashi2,8, T. Henning13, K. W. Hodapp19,M. Ishii8, M. Iye2,3, M. Janson9, R. Kandori3, J. Kwon2, G. R. Knapp9, T. Matsuo20, M. W. McElwain18, S. Miyama21, J.-I. Morino3, A. Moro-Martin9,22, T. Nishimura8, T.-S. Pyo8, E. Serabyn23, H. Suto3,R. Suzuki3, N. Takato2,8, H. Terada8, C. Thalmann24, D. Tomono8, E. L. Turner9,25, M. Watanabe26, T. Yamada28, H. Takami2,8, T. Usuda2,8, M. Tamura2,3 1 The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193, Japan 2 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan 3 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan 4 Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-8677, Japan 5 College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan 6 Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan 7 Department of Astronomy, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan 8 Subaru Telescope, 650 North A’ohoku Place, Hilo, HI 96720, USA 9 Department of Astrophysical Sciences, Princeton University, NJ08544, USA 10 Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1, Machikaneyama, Toyonaka, Osaka 560-0043, Japan

32 11 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan 12 Laboratoire Hippolyte Fizeau, UMR6525, Universite de Nice Sophia-Antipolis, 28, avenue Valrose, 06108 Nice Cedex 02, France 13 Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany 14 Department of Physics and Astronomy, College of Charleston, 58 Coming St., Charleston, SC 29424, USA. 15 Department of Astronomy and Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Rm. N204, Tucson, AZ 85721-0065, USA 16 Goddard Center for Astrobiology, NASA’s Goddard Space Flight Center, Greenbelt, MD 20771, USA 17 Eureka Scientific, 2452 Delmer, Suite 100, Oakland CA 96002, USA 18 ExoPlanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 USA 19 Institute for Astronomy, University of Hawaii, 640 North A’ohoku Place, Hilo, HI 96720, USA 20 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan 21 Office of the President, Hiroshima University, 1-3-2 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8511, JAPAN 22 Departamento de Astrofisica, CAB (INTA-CSIC), Instituto Nacional de Técnica Aeroespacial, Torrejón de Ardoz, 28850, Madrid, Spain 23 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA 24 Astronomical Institute ”Anton Pannekoek”, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands 25 Institute for the Physics and Mathematics of the Universe, The University of Tokyo, Kashiwa 227-8568, Japan 26 Department of Cosmosciences, Hokkaido University, Sapporo 060-0810, Japan 27 H L Dodge Department of Physics & Astronomy, University of Oklahoma, 440 W Brooks St. Norman, OK 73019, USA 28 Astronomical Institute, Tohoku University, Aoba, Sendai 980-8578, Japan 29 Universitäts-Sternwarte München Scheinerstr. 1, D-81679 Munich, Germany E-mail contact: mayama satoshi at soken.ac.jp We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our H-band data, which clearly exhibits a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths. We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor axis, semiminor axis, and position angle of the disk as 63 AU, 62 AU, and -14 ◦, respectively. angle of -14 ◦. The disk is asymmetric, with one dip located at position angles of ∼85◦. Our observed disk size agrees well with a previous study of dust and CO emission at submm wavelength with SMA. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Our observations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edge of the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility that the inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within the disk. Accepted by ApJL (760:L26) http://iopscience.iop.org/2041-8205/760/2/L26/ http://arxiv.org/pdf/1211.3284

A Double-Jet System in the G31.41+0.31 Hot Molecular Core Luca Moscadelli1, Jing Li Jing2, Riccardo Cesaroni1, Alberto Sanna3, Ye Xu2 and Qizhou Zhang4 1 INAF-Osservatorio Astroﬁsico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 2 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China 3 Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA E-mail contact: mosca at arcetri.astro.it

Many aspects of massive star (∼>10 M⊙) formation are still unclear. In particular, the outﬂow properties at close distance (100–1000 AU) from a “Massive Young Stellar Object” (MYSO) are not yet well established. This work

33 presents a detailed study of the gas kinematics towards the “Hot Molecular Core” (HMC) G31.41+0.31. To study the HMC 3-D kinematics at milli-arcsecond angular resolution, we have performed multi-epoch VLBI observations of the H2O 22 GHz and CH3OH 6.7 GHz masers, and single-epoch VLBI of the OH 1.6 GHz masers. Water masers present a symmetric spatial distribution with respect to the HMC center, where two nearby (0.2′′ apart), compact, VLA sources (labeled “A” and “B”) are previously detected. The spatial distribution of a first group of water masers, named “J1”, is well fit with an elliptical profile, and the maser proper motions mainly diverge from the ellipse center, with average speed of 36 km s−1. These findings strongly suggest that the “J1” water maser group traces the heads of a young 3 −1 −1 (dynamical time of 1.310 yr), powerful (momentum rate of ≃ 0.2 M⊙ yr km s ), collimated (semi-opening angle ≃ 10◦) jet emerging from a MYSO located close (within ≈0.15′′) to the VLA source “B”. Most of the water features not belonging to “J1” present an elongated (≈2′′ in size), NE–SW oriented (PA≈70◦), S-shape distribution, which we denote with the label “J2”. The elongated distribution of the “J2” group and the direction of motion, approximately parallel to the direction of elongation, of most “J2” water masers suggests the presence of another collimated outflow, emitted from a MYSO placed near the VLA source “A”. The proper motions of the CH3OH 6.7 GHz masers, mostly diverging from the HMC center, also witness the expansion of the HMC gas driven by the “J1” and “J2” jets. The ◦ ◦ orientation (PA≈70 ) of the “J2” jet agrees well with that (PA = 68 ) of the well-defined VLSR gradient across the HMC revealed by previous interferometric, thermal line observations. Furthermore, the “J2” jet is powerful enough −1 −1 to sustain the large momentum rate, 0.3 M⊙ yr km s , estimated from the interferometric, molecular line data in the assumption that the VLSR gradient represents a collimated outflow. These two facts lead us to favour the interpretation of the VLSR gradient across the G31.41+0.31 HMC in terms of a compact and collimated outflow. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1211.2667

Dynamics of Core Accretion Andrew F. Nelson1 and Maximilian Ruﬀert2 1 XCP-2 MS T087, Los Alamos National Laboratory, Los Alamos NM, 87545, USA 2 School of Mathematics and Maxwell Institute, University of Edinburgh, Edinburgh Scotland EH9 3JZ E-mail contact: andy.nelson at lanl.gov

We perform 3-dimensional hydrodynamic simulations of gas flowing around a planetary core of mass Mpl=10M⊕ embedded in a near Keplerian background flow, using a modified shearing box approximation. We assume an ideal gas behavior following an equation of state with a fixed ratio of the specific heats, γ =1.42, consistent with the conditions of a moderate temperature background disk with solar composition. No radiative heating or cooling is included in the models. We employ a nested grid hydrodynamic code implementing the ‘Piecewise Parabolic Method’ with as many as six fixed nested grids, providing spatial resolution on the finest grid comparable to the present day diameters of Neptune and Uranus. We find that a strongly dynamically active flow develops such that no static envelope can form. The activity is not sensitive to plausible variations in the rotation curve of the underlying disk. It is sensitive to the thermodynamic treatment of the gas, as modeled by prescribed equations of state (either ‘locally isothermal’ or ‘locally isentropic’) and the temperature of the background disk material. The activity is also sensitive to the shape and depth of the core’s gravitational potential, through its mass and gravitational softening coefficient. Each of these factors influence the magnitude and character of hydrodynamic feedback of the small scale flow on the background, and we conclude that accurate modeling of such feedback is critical to a complete understanding of the core accretion process. The varying flow pattern gives rise to large, irregular eruptions of matter from the region around the core which return matter to the background flow: mass in the envelope at one time may not be found in the envelope at any later time. No net mass accretion into the envelope is observed over the course of the simulation and none is expected, due to our neglect of cooling. Except in cases of very rapid cooling however, as defined by locally isothermal or isentropic treatments, any cooling that does affect the envelope material will have limited consequences for the dynamics, since the flow quickly carries cooled material out of the core’s environment entirely. The angular momentum of material in the envelope, relative to the core, varies both in magnitude and in sign on time scales of days to months near the core and on time scales a few years at distances comparable to the Hill radius. The dynamical activity contrasts with the largely static behavior typically assumed within the framework of the core accretion model for Jovian planet formation.

34 We show that material entering the dynamically active environment may suﬀer intense heating and cooling events the durations of which are as short as a few hours to a few days. Shorter durations are not observable in our work due to the limits of our resolution. Peak temperatures in these events range from T ∼ 1000 K to as high as T ∼ 3 − 4000 K, with densities ρ ∼ 10−9 − 10−8 g/cm3. These time scales, densities and temperatures span a range consistent with those required for chondrule formation in the nebular shock model. We therefore propose that dynamical activity in the Jovian planet formation environment could be responsible for the production of chondrules and other annealed silicates in the solar nebula. Accepted by MNRAS http://arxiv.org/pdf/1211.5423

Ortho–H2 and the age of prestellar cores Laurent Pagani1, Pierre Lesaffre2, Mohammad Jorfi3, Pascal Honvault4,5, Tomas González-Lezana6 and Alexandre Faust7 1 LERMA, UMR8112 du CNRS, Observatoire de Paris, 61, Av. de l’Observatoire, 75014 Paris, France 2 LERMA, UMR8112 du CNRS, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France 3 Institut de Chimie des Milieux et des Matériaux de Poitiers, UMR CNRS 6503, Universitéde Poitiers, 86022 Poitiers Cedex, France 4 Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 du CNRS, Universitéde Bourgogne, 21078 Dijon Cedex, France 5 UFR Sciences et Techniques, Universitéde Franche-Comté, 25030 Besan¸con cedex, France 6 Instituto de F´ısica Fundamental, CSIC, Serrano 123, 28006 Madrid, Spain 7 Institut de Planétologie et d’Astrophysique de Grenoble, UMR 5274 du CNRS, UniversitéJoseph Fourier, B.P. 53, 38041 Grenoble Cedex 09, France E-mail contact: laurent.pagani at obspm.fr Prestellar cores form from the contraction of cold gas and dust material in dark clouds before they collapse to form protostars. Several concurrent theories exist to describe this contraction which are currently difficult to discriminate. One major difference is the time scale involved to form the prestellar cores: some theories advocate nearly free-fall speed via e.g. rapid turbulence decay while others can accommodate much longer periods to let the gas accumulate via e.g. ambipolar diffusion. To discriminate between these theories, measuring the age of prestellar cores could greatly help. However, no reliable clock currently exists. We present a simple chemical clock based on the regulation of the deuteration by the abundance of ortho–H2 that slowly decays away from the ortho–para statistical ratio of 3 down to or less than 0.001. We use a chemical network fully coupled to a hydrodynamical model which follows the contraction of a cloud, starting from uniform density, and reaches a density profile typical of a prestellar core. We + + compute the N2D /N2H ratio along the density profile. The disappearance of ortho–H2 is tied to the duration of + + the contraction and the N2D /N2H ratio increases in the wake of the ortho–H2 abundance decrease. By adjusting the time of contraction, we obtain different deuteration profiles that we can compare to the observations. Our model can test fast contractions (from 104 to 106 cm−3 in ∼0.5 My) and slow contraction (from 104 to 106 cm−3 in ∼5 My). We have tested the sensitivity of the models to various initial conditions. The slow contraction deuteration profile is approximately insensitive to these variations while the fast contraction deuteration profile shows significant variations. We found that in all cases, the deuteration profile remains clearly distinguishable whether it comes from + + the fast collapse or the slow collapse. We also study the para–D2H /ortho–H2D ratio and find that its variation is not monotonic and therefore not discriminant between models. Applying this model to L183 (= L134N), we find + + that the N2D /N2H ratio would be larger than unity for evolutionary timescales of a few megayears independently of other parameters such as, e.g., cosmic ray ionization rate or grain size (within reasonable ranges). A good fit to the observations is obtained for fast contraction only (≤ 0.7 My from the beginning of the contraction and ≤ 4 My from the birth of the molecular cloud based on the necessity to keep a high ortho–H2 abundance when the contraction starts – ortho–H2/para–H2 ≥ 0.2 – to match the observations). This chemical clock therefore rules out slow contraction in L183 and steady state chemical models, as steady state is clearly not reached here. This clock should be applied to other cores to help discriminate between slow and fast contraction theories over a large sample of cases. Accepted by A&A For preprints, please, contact 1st author

35 Early stages of cluster formation: fragmentation of massive dense cores down to 1000 AU Aina Palau1, Asunción Fuente2, Josep M. Girart1, Robert Estalella3, Paul T. P. Ho4,5, Alvaro´ Sánchez- Monge6, Francesco Fontani6, Gemma Busquet7, Benoˆıt Commercon8, Patrick Hennebelle8, Jérémie Boissier9,10, Qizhou Zhang4, Riccardo Cesaroni6, Luis A. Zapata11 1 Institut de Ciències de l’Espai, Campus UAB Facultat de Ciències, Torre C5 parell 2, 08193 Bellaterra, Catalunya, Spain 2 Observatorio Astronómico Nacional, P.O. Box 112, 28803 Alcalàde Henares, Madrid, Spain 3 Departament d’Astronomia i Meteorologia (IEEC-UB), Institut de Ciències del Cosmos, Universitat de Barcelona, Mart Franquès, 1, 08028 Barcelona, Spain 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 5 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan 6 Osservatorio Astrofisico di Arcetri, INAF, Lago E. Fermi 5, 50125, Firenze, Italy 7 INAF-Istituto di Astrofisica e Planetologia Spaziali, Areadi Recerca di Tor Vergata, Via Fosso Cavaliere 100, 00133, Roma, Italy 8 Laboratoire de Radioastronomie, UMR CNRS 8112, Ecole´ Normale Supérieure et Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05, France 9 Istituto di Radioastronomia, INAF, Via Gobetti 101, Bologna, Italy 10 ESO, Karl Schwarzschild St. 2, 85748 Garching Muenchen, Germany 11 Centro de Radioastronom´ıay Astrofsica, Universidad Nacional Autónoma de Mxico, P.O. Box 3-72, 58090, Morelia, Michoacán, Mexico E-mail contact: palau at ieec.uab.es In order to study the fragmentation of massive dense cores, which constitute the cluster cradles, we observed with the PdBI in the most extended configuration the continuum at 1.3 mm and the CO(2-1) emission of four massive ′′ cores. We detect dust condensations down to ∼0.3 M⊙ and separate millimeter sources down to 0.4 or ∼1000 AU, comparable to the sensitivities and separations reached in optical/infrared studies of clusters. The CO(2-1) high angular resolution images reveal high-velocity knots usually aligned with previously known outflow directions. This, in combination with additional cores from the literature observed at similar mass sensitivity and spatial resolution, allowed us to build a sample of 18 protoclusters with luminosities spanning 3 orders of magnitude. Among the 18 regions, ∼30% show no signs of fragmentation, while 50% split up into ∼4 millimeter sources. We compiled a list of properties for the 18 massive dense cores, such as bolometric luminosity, total mass, and mean density, and found no correlation of any of these parameters with the fragmentation level. In order to investigate the combined effects of magnetic field, radiative feedback and turbulence in the fragmentation process, we compared our observations to radiation magneto-hydrodynamic simulations, and found that the low-fragmented regions are well reproduced in the magnetized core case, while the highly-fragmented regions are consistent with cores where turbulence dominates over the magnetic field. Overall, our study suggests that the fragmentation in massive dense cores could be determined by the initial magnetic field/turbulence balance in each particular core. Accepted by ApJ http://arxiv.org/pdf/1211.2666

Herschel view of the Taurus B211/3 filament and striations: Evidence of filamentary growth? P. Palmeirim1, Ph. André1, J. Kirk2, D. Ward-Thompson3, D. Arzoumanian1, V. Könyves1,4, P. Didelon1, N. Schneider1,5, M. Benedettini6, S. Bontemps5, J. Di Francesco7,8, D. Elia6, M. Griffin2,M. Hennemann1, T. Hill1, P. G. Martin9, A. Men’shchikov1, S. Molinari6, F. Motte1, Q. Nguyen Luong9, D. Nutter2, N. Peretto1, S. Pezzuto6, A. Roy9, K. L. J. Rygl6, L. Spinoglio6 and G. L. White10,11 1 Laboratoire AIM, CEA/DSM–CNRS–UniversitéParis Diderot, IRFU/Service d’Astrophysique, C.E.A. Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France 2 School of Physics & Astronomy, Cardiff University, Cardiff, UK 3 Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, UK 4 Institut d’Astrophysique Spatiale, UMR 8617, CNRS/UniversitéParis-Sud 11, 91405 Orsay, France

36 5 Universitéde Bordeaux, Laboratoire d’Astrophysique de Bordeaux, CNRS/INSU, UMR 5804, BP 89, 33271 Floirac Cedex, France 6 INAF - IAPS, via Fosso del Cavaliere 100, I-00133 Roma, Italy 7 National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria BC, V9E 2E7, Canada 8 Department of Physics and Astronomy, University of Victoria, PO Box 355, STN CSC, Victoria BC, V8W 3P6, Canada 9 Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON, M5S 3H8, Canada 10 Space Science and Technology Department, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK 11 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK E-mail contact: pedro.palmeirim at cea.fr We present first results from the Herschel Gould Belt survey for the B211/L1495 region in the Taurus molecular cloud. Thanks to their high sensitivity and dynamic range, the Herschel images reveal the structure of the dense, star-forming filament B211 with unprecedented detail, along with the presence of striations perpendicular to the filament and generally oriented along the magnetic field direction as traced by optical polarization vectors. Based on the column density and dust temperature maps derived from the Herschel data, we find that the radial density profile of the B211 filament approaches power-law behavior, ρ ∝ r−2.0±0.4, at large radii and that the temperature profile exhibits a marked drop at small radii. The observed density and temperature profiles of the B211 filament are in good agreement with a theoretical model of a cylindrical filament undergoing gravitational contraction with a polytropic equation of state: P ∝ ργ and T ∝ ργ−1, with γ=0.97±0.01<1 (i.e., not strictly isothermal). The morphology of the column density map, where some of the perpendicular striations are apparently connected to the B211 filament, further suggests that the material may be accreting along the striations onto the main filament. The typical velocities expected for the infalling material in this picture are ∼ 0.5–1 km/s, which are consistent with the existing kinematical constraints from previous CO observations. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1211.6360

Local-Density Driven Clustered Star Formation Genevieve Parmentier1 and Susanne Pfalzner2 1 Zentrum für Astronomie, Heidelberg Universität, Germany 2 Max-Planck Institut für Radioastronomie, Bonn, Germany E-mail contact: gparm at ari.uni-heidelberg.de

A positive power-law trend between the local surface densities of molecular gas, Σgas, and young stellar objects, Σ⋆, in molecular clouds of the Solar Neighbourhood has recently been identified by Gutermuth et al. How it relates to the properties of embedded clusters, in particular to the recently established radius-density relation, has so far not been investigated. In this paper, we model the development of the stellar component of molecular clumps as a function of time and initial local volume density so as to provide a coherent framework able to explain both the molecular- cloud and embedded-cluster relations quoted above. To do so, we associate the observed volume density gradient of molecular clumps to a density-dependent free-fall time. The molecular clump star formation history is obtained by applying a constant SFE per free-fall time, ǫff . For volume density profiles typical of observed molecular clumps (i.e. power-law slope ≃ −1.7), our model gives a 2 star-gas surface-density relation Σ⋆ ∝ Σgas, in very good agreement with the Gutermuth et al relation. Taking the 4 case of a molecular clump of mass M0 ≃ 10 Msun and radius R ≃ 6pc experiencing star formation during 2 Myr, we derive what SFE per free-fall time matches best the normalizations of the observed and predicted (Σ⋆,Σgas) relations. We find ǫff ≃ 0.1. We show that the observed growth of embedded clusters, embodied by their radius-density relation, corresponds to a surface density threshold being applied to developing star-forming regions. The consequences of our model in terms of cluster survivability after residual star-forming gas expulsion are that due to the locally high SFE in the inner part of star-forming regions, global SFE as low as 10% can lead to the formation of bound gas-free star clusters.

37 Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1211.1383

Warm water deuterium fractionation in IRAS 16293-2422 – The high-resolution ALMA and SMA view Magnus V. Persson1,2, Jes K. Jørgensen2,1 and Ewine F. van Dishoeck3,4 1 Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350, Copenhagen K, Denmark 2 Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark 3 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands 4 Max-Planck Institute für extraterrestrische Physik (MPE), Giessenbachstrasse, 85748 Garching, Germany E-mail contact: magnusp at nbi.dk Measuring the water deuterium fractionation in the inner warm regions of low-mass protostars has so far been ham- pered by poor angular resolution obtainable with single-dish ground- and space-based telescopes. Observations of water isotopologues using (sub)millimeter wavelength interferometers have the potential to shed light on this matter. 18 Observations toward IRAS 16293-2422 of the 53,2 − 44,1 transition of H2 O at 692.07914 GHz from Atacama Large 18 Millimeter/submillimeter Array (ALMA) as well as the 31,3 − 22,0 of H2 O at 203.40752 GHz and the 31,2 − 22,1 18 transition of HDO at 225.89672 GHz from the Submillimeter Array (SMA) are presented. The 692 GHz H2 O line is seen toward both components of the binary protostar. Toward one of the components, “source B”, the line is seen in absorption toward the continuum, slightly red-shifted from the systemic velocity, whereas emission is seen off-source 18 at the systemic velocity. Toward the other component, “source A”, the two HDO and H2 O lines are detected as 18 well with the SMA. From the H2 O transitions the excitation temperature is estimated at 124 ± 12 K. The calculated −4 HDO/H2O ratio is (9.2 ± 2.6) × 10 – significantly lower than previous estimates in the warm gas close to the source. It is also lower by a factor of ∼5 than the ratio deduced in the outer envelope. Our observations reveal the physical and chemical structure of water vapor close to the protostars on solar-system scales. The red-shifted absorption detected toward source B is indicative of infall. The excitation temperature is consistent with the picture of water ice evaporation close to the protostar. The low HDO/H2O ratio deduced here suggests that the differences between the inner regions of the protostars and the Earth’s oceans and comets are smaller than previously thought. Accepted by Astronomy & Astrophysics Letters http://arxiv.org/pdf/1211.6605

Constraining mass ratio and extinction in the FU Orionis binary system with infrared integral field spectroscopy Laurent Pueyo1, Lynne Hillenbrand2, Gautam Vasisht3, Ben R. Oppenheimer4, John D. Monnier5, Sasha Hinkley2, Justin Crepp7, Lewis C. Roberts Jr3, Douglas Brenner4, Neil Zimmerman4, Ian Parry8, Charles Beichman6, Richard Dekany2, Mike Shao3, Rick Burruss3, Eric Cady3, Jenny Roberts2, and Remi Soummer1 1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 2 Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA 3 Jet propulsion Laboratory, California Institute of technology, 4800 Oak Grove Drive, Pasadena, CA 91109 , USA 4 American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA 5 Department of Astronomy, University of Michigan, 941 Dennison Building, 500 Church Street, Ann Arbor, MI 48109-1090, USA 6 NASA Exoplanet Science Institute, 770 S. Wilson Avenue, Pasadena, CA 91225, USA 7 Department of Physics, 225 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA 8 University of Cambridge, Institute of Astronomy, Madingley Rd, Cambridge, CB3 0HA, UK We report low resolution near infrared spectroscopic observations of the eruptive star FU Orionis using the Integral Field Spectrograph Project 1640 installed at the Palomar Hale telescope. This work focuses on elucidating the nature of the faint source, located 0.5′′ south of FU Ori, and identified in 2003 as FU Ori S. We first use our observations

38 in conjunction with published data to demonstrate that the two stars are indeed physically associated and form a true binary pair. We then proceed to extract J and H band spectro-photometry using the damped LOCI algorithm, a reduction method tailored for high contrast science with IFS. This is the ﬁrst communication reporting the high accuracy of this technique, pioneered by the Project 1640 team, on a faint astronomical source. We use our low resolution near infrared spectrum in conjunction with 10.2 micron interferometric data to constrain the infrared excess of FU Ori S. We then focus on estimating the bulk physical properties of FU Ori S. Our models lead to estimates of an object heavily reddened, AV = 8-12, with an eﬀective temperature of ∼ 4000–6500 K . Finally we put these results in the context of the FU Ori N-S system and argue that our analysis provides evidence that FU Ori S might be the more massive component of this binary system. Accepted by ApJ (757:A57) http://arxiv.org/pdf/1211.6741

The Co-ordinated Radio and Infrared Survey for High-Mass Star Formation - II. Source Catalogue C. R. Purcell1,2,3, M. G. Hoare1, W. D. Cotton4, S. L. Lumsden1, J. S. Urquhart1,5,6, C. Chandler7, E. B. Churchwell8, P. Diamond2, 5, S. M. Dougherty9, R. P. Fender10, G. Fuller2, S. T. Garrington2, T. M. Gledhill11, P. F. Goldsmith12, L. Hindson5,11, J. M. Jackson13, S. E. Kurtz14, J. Mart´ı15, T. J. T. Moore16, L. G. Mundy17, T. W. B. Muxlow2, R. D. Oudmaijer1, J. D. Pandian18, J. M. Paredes19, D. S. Shepherd7,20, S. Smethurst2, R. E. Spencer2, M. A. Thompson11, G. Umana21 and A. A. Zijlstra2 1 School of Physics & Astronomy, E.C. Stoner Building, University of Leeds, Leeds LS2 9JT, UK 2 Jodrell Bank Centre for Astrophysics, The Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Rd, Manchester, M13 9PL, UK 3 Sydney Institute for Astronomy (SiFA), School of Physics, The University of Sydney, NSW 2006, Australia 4 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA 5 CSIRO Astronomy and Space Science, PO BOX 76, Epping, NSW 1710, Australia 6 Max-Planck-Institut fu¨rRadioastronomie, Auf dem Hu¨gel 69, D-53121 Bonn, Germany 7 National Radio Astronomy Observatory, Array Operations Center, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387, USA 8 The University of Wisconsin, Department of Astronomy, 475 North Charter Street Madison, WI 53706, USA 9 National Research Council of Canada, Herzberg Institute for Astrophysics, Dominion Radio Astrophysical Observa- tory, PO Box 248, Penticton, British Columbia V2A 6J9, Canada 10 School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK 11 Science and Technology Research Institute, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK 12 Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, USA 13 Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA 14 Centro de Radioastronom´ıay Astrof´ısica, Universidad Nacional Autónoma de México - Morelia, Apartado Postal 3-72, C.P. 58090 Morelia, Michoacan, Mexico 15 Departamento de F´ısica, EPSJ, Universidad de Jaén, Campus Las Lagunillas s/n, Edif. A3, 23071 Jaén, Spain 16 Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birken- head CH41 1LD, UK 17 Department of Astronomy, University of Maryland College Park, MD 20742-2421, USA 18 Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, Hawaii 96822-1839, USA 19 Departament d’Astronomia i Meteorologia and Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (UB/IEEC), Mart´ıFranqu`s1, 08028 Barcelona, Spain 20 Square Kilometer Array - South Africa, 3rd floor, The Park, Park Rd, Pinelands, Cape Town, 7405 Western Cape, South Africa 21 INAF Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy E-mail contact: C.R.Purcell at leeds.ac.uk The CORNISH project is the highest resolution radio continuum survey of the Galactic plane to date. It is the 5 GHz radio continuum part of a series of multi-wavelength surveys that focus on the northern GLIMPSE region (10◦

39 and BnA configurations have yielded a 1.5′′ resolution Stokes I map with a root-mean-squared noise level better than 0.4mJybeam−1. Here we describe the data-processing methods and data characteristics, and present a new, uniform catalogue of compact radio-emission. This includes an implementation of automatic deconvolution that provides much more reliable imaging than standard CLEANing. A rigorous investigation of the noise characteristics and reliability of source detection has been carried out. We show that the survey is optimised to detect emission on size scales up to 14′′ and for unresolved sources the catalogue is more than 90 percent complete at a flux density of 3.9 mJy. We have detected 3,062 sources above a 7σ detection limit and present their ensemble properties. The catalogue is highly reliable away from regions containing poorly-sampled extended emission, which comprise less than two percent of the survey area. Imaging problems have been mitigated by down-weighting the shortest spacings and potential artefacts flagged via a rigorous manual inspection with reference to the Spitzer infrared data. We present images of the most common source types found: H II regions, planetary nebulae and radio-galaxies. The CORNISH data and catalogue are available online at http://cornish.leeds.ac.uk. Accepted by ApJ. Sup. http://arxiv.org/pdf/1211.7116

13CO Cores in the Taurus Molecular Cloud Lei Qian1, Di Li1,2,3 and Paul Goldsmith4 1 National Astronomical Observatories, CAS, Beijing, 100012, China 2 Space Science Institute, Boulder, CO, USA 3 Department of Astronomy, California Institute of Technology, CA, USA 4 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA E-mail contact: lqian at nao.cas.cn Young stars form in molecular cores, which are dense condensations within molecular clouds. We have searched for molecular cores traced by 13COJ=1 → 0 emission in the Taurus molecular cloud and studied their properties. Our data set has a spatial dynamic range (the ratio of linear map size to the pixel size) of about 1000 and spectrally resolved velocity information, which together allow a systematic examination of the distribution and dynamic state 13 of CO cores in a large contiguous region. We use empirical fit to the CO and CO2 ice to correct for depletion of gas-phase CO. The 13CO core mass function (13CO CMF) can be fitted better with a log-normal function than with a power-law function. We also extract cores and calculate the 13CO CMF based on the integrated intensity of 13CO and the CMF from Two Micron All Sky Survey. We demonstrate that core blending exists, i.e., combined structures that are incoherent in velocity but continuous in column density. The core velocity dispersion (CVD), which is the variance of the core velocity difference δv, exhibits a power-law behavior as a function of the apparent separation L: CVD (km s−1) v ∝ L(pc)0.7. This is similar to Larson’s law for the velocity dispersion of the gas. The peak velocities of 13CO cores do not deviate from the centroid velocities of the ambient 12CO gas by more than half of the line width. The low velocity dispersion among cores, the close similarity between CVD and Larson’s law, and the small separation between core centroid velocities and the ambient gas all suggest that molecular cores condense out of the diffuse gas without additional energy from star formation or significant impact from converging flows. Accepted by Astrophysical Journal http://arxiv.org/pdf/1206.2115v3

Proper Motions of Young Stellar Outﬂows in the Mid-Infrared with Spitzer (IRAC). I. The NGC 1333 region A. C. Raga1, A. Noriega-Crespo2, S. J. Carey3, H. G. Arce4 1 Instituto de Ciencias Nucleares, UNAM, Ap. 70-543, 04510 D.F., Mexico 2 Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA 3 Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA 4 Department of Astronomy, Yale University, New Haven, CT 06520, USA Draft version November 5, 2012 E-mail contact: raga at nucleares.unam.mx We use two 4.5 micron Spitzer (IRAC) maps of the NGC 1333 region taken over a ∼ 7 yr interval to determine

40 proper motions of its associated outflows. This is a first, successful attempt at obtaining proper motions of stellar outflow from Spitzer observations. For the outflow formed by the Herbig-Haro objects HH7, 8 and 10, we find proper motions of ∼ 9–13 km s−1, which are consistent with previously determined optical proper motions of these objects. We determine proper motions for a total of 8 outflows, ranging from ∼ 10 to 100 km s−1. The derived proper motions show that out of these 8 outflows, 3 have tangential velocities ≤ to 20 km s−1. This result shows that a large fraction of the observed outflows have low intrinsic velocities, and that the low proper motions are not merely a projection effect. Accepted by the Astronomical Journal http://arxiv.org/pdf/1211.0273

Mini-Oort clouds: Compact isotropic planetesimal clouds from planet-planet scattering Sean N. Raymond1,2 and Philip J. Armitage3,4 1 CNRS, UMR 5804, Laboratoire d’Astrophysique de Bordeaux, 2 rue de l’Observatoire, BP 89, F-33271 Floirac Cedex, France 2 Universit´ede Bordeaux, Observatoire Aquitain des Sciences de l’Univers, 2 rue de l’Observatoire, BP 89, F-33271 Floirac Cedex, France 3 JILA, University of Colorado & NIST, 440 UCB, Boulder CO 80309-0440, USA 4 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, USA E-mail contact: rayray.sean at gmail.com Starting from planetary systems with three giant planets and an outer disk of planetesimals, we use dynamical simulations to show how dynamical instabilities can transform planetesimal disks into 100-1000 AU-scale isotropic clouds. The instabilities involve a phase of planet-planet scattering that concludes with the ejection of one or more planets and the inward-scattering of the surviving gas giant(s) to remove them from direct dynamical contact with the planetesimals. ”Mini-Oort clouds” are thus formed from scattered planetesimals whose orbits are frozen by the abrupt disappearance of the perturbing giant planet. Although the planetesimal orbits are virtually isotropic, the surviving giant planets tend to have modest inclinations (typically ∼10 degrees) with respect to the initial orbital plane. The collisional lifetimes of mini-Oort clouds are long (10 Myr to >10 Gyr) and there is a window of ∼100 Myr or longer during which they produce spherical clouds of potentially observable dust at 70 microns. If the formation channel for hot Jupiters commonly involves planetary close encounters, we predict a correlation between this subset of extrasolar planetary systems and mini-Oort clouds. Accepted to MNRAS Letters http://arxiv.org/pdf/1211.2809

New Young Star Candidates in BRC 27 and BRC 34 L. M. Rebull1, C. H. Johnson2, J. C. Gibbs3, M. Linahan4, D. Sartore5, R. Laher1, M. Legassie1,6, J. D. Armstrong7, L. E. Allen8, P. McGehee9 D. L. Padgett10 S. Aryal3, K. S. Badura5, T. S. Canakapalli3, S. Carlson2, M. Clark2, N. Ezyk4, J. Fagan4, N. Killingstad2, S. Koop2, T. McCanna2, M. M. Nishida3, T. R. Nuthmann3, A. O’Bryan2, A. Pullinger4, A. Rameswaram4, T. Ravelomanantsoa2, H. Sprow4, C. M. Tilley5 1 Spitzer Science Center/Caltech, M/S 220-6, 1200 E. California Blvd., Pasadena, CA 91125, USA 2 Breck School, 123 Ottawa Ave. N., Golden Valley, MN 55422 USA 3 Glencoe High School, 2700 NW Glencoe Rd., Hillsboro, OR 97124 USA 4 Carmel Catholic High School, One Carmel Parkway, Mundelein, IL 60060, USA 5 Pine Ridge High School, 926 Howland Blvd., Deltona, FL 32738 USA 6 Raytheon Mission Operations and Services, 299 N. Euclid Ave, Pasadena, CA, 91101 USA 7 Las Cumbres Observatory Global Telescope (LCOGT) & University of Hawaii, HI, USA 8 NOAO, Tucson, AZ, USA 9 IPAC, M/S 220-6, 1200 E. California Blvd., Pasadena, CA 91125, USA 10 NASA’s Goddard Space Flight Center, 8800 Greenbelt Rd., Greenbelt, MD, 20771, USA E-mail contact: [email protected]

41 We used archival Spitzer Space Telescope mid-infrared data to search for young stellar objects (YSOs) in the immediate vicinity of two bright-rimmed clouds, BRC 27 (part of CMa R1) and BRC 34 (part of the IC 1396 complex). These regions both appear to be actively forming young stars, perhaps triggered by the proximate OB stars. In BRC 27, we find clear infrared excesses around 22 of the 26 YSOs or YSO candidates identified in the literature, and identify 16 new YSO candidates that appear to have IR excesses. In BRC 34, the one literature-identified YSO has an IR excess, and we suggest 13 new YSO candidates in this region, including a new Class I object. Considering the entire ensemble, both BRCs are likely of comparable ages, within the uncertainties of small number statistics and without spectroscopy to confirm or refute the YSO candidates. Similarly, no clear conclusions can yet be drawn about any possible age gradients that may be present across the BRCs. Accepted by Astron. J. http://web.ipac.caltech.edu/~rebull/papers/brc1.pdf

A Search for Herbig-Haro Objects in NGC 7023 and Barnard 175 Travis Rector1 and Heidi Schwieker2 1 University of Alaska Anchorage, Dept. of Physics and Astronomy, Anchorage, AK 99508 USA 2 National Optical Astronomy Observatory, Tucson, AZ 85719, USA E-mail contact: rector at uaa.alaska.edu Wide-field optical imaging was obtained of the cluster and reflection nebula NGC 7023 and the Bok globule B175. We report the discovery of four new Herbig-Haro (HH) objects in NGC 7023, the first HH objects to be found in this region. They were first detected by their Hα and [S II] emission but are also visible at 3.6 and 4.5 µm in archival Spitzer observations of this field. These HH objects are part of at least two distinct outflows. Both outflows are aligned with embedded “Class I” YSOs in a tight group on the western edge of the nebula. One of the outflows may have a projected distance of 0.75pc, which is a notable length for an embedded source. No new HH objects were discovered in B175. However, we reclassify the knot HH450X, in B175, as a background galaxy. The discovery that HH 450X is not a shock front weakens the argument that HH 450 and SNR G110.3+11.3 are co-located and interacting. Accepted by AJ http://arxiv.org/pdf/1211.7190

Formation of the Widest Binaries from Dynamical Unfolding of Triple Systems Bo Reipurth1 and Seppo Mikkola2 1 Institute for Astronomy, Univ. of Hawaii at Manoa, 640 N. Aohoku Place, HI 96720, USA 2 Tuorla Observatory, University of Turku, Väisäläntie 20, Piikkiö, Finland E-mail contact: reipurth at ifa.hawaii.edu The formation of very wide binaries, such as the α Cen system with Proxima (also known as α Centauri C) separated from α Centauri (which itself is a close binary A/B) by 15000 AU, challenges current theories of star formation, because their separation can exceed the typical size of a collapsing cloud core. Various hypotheses have been proposed to overcome this problem, including the suggestion that ultra-wide binaries result from the dissolution of a star cluster – when a cluster star gravitationally captures another, distant, cluster star. Recent observations have shown that very wide binaries are frequently members of triple systems and that close binaries often have a distant third companion. Here we report Nbody simulations of the dynamical evolution of newborn triple systems still embedded in their nascent cloud cores that match observations of very wide systems. We find that although the triple systems are born very compact – and therefore initially are more protected against disruption by passing stars – they can develop extreme hierarchical architectures on timescales of millions of years as one component is dynamically scattered into a very distant orbit. The energy of ejection comes from shrinking the orbits of the other two stars, often making them look from a distance like a single star. Such loosely bound triple systems will therefore appear to be very wide binaries. Accepted by Nature (Dec 13, 2012 issue) http://arxiv.org/pdf/1212.1246

42 ALMA observations of rho-Oph 102: grain growth and molecular gas in the disk around a young Brown Dwarf L. Ricci, L. Testi, A. Natta, A. Scholz, and I. de Gregorio-Monsalvo 1 Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA 2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany 3 INAF-Osservatorio Astroﬁsico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy 4 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland 5 Joint ALMA Observatory (JAO)/ESO, Alonso de Cordova 3107. Vitacura 763 0335. Santiago de Chile E-mail contact: lricci at astro.caltech.edu We present ALMA continuum and spectral line observations of the young Brown Dwarf rho-Oph 102 at about 0.89 mm and 3.2 mm. We detect dust emission from the disk at these wavelengths and derive an upper limit on the radius of the dusty disk of ∼ 40 AU. The derived variation of the dust opacity with frequency in the mm provides evidence for the presence of mm-sized grains in the disk outer regions. This result demonstrates that mm-grains are found even in the low density environments of Brown Dwarf disks and challenges our current understanding of dust evolution in disks. The CO map at 345 GHz clearly reveals molecular gas emission at the location of the Brown Dwarf, indicating a gas-rich disk as typically found for disks surrounding young pre-Main Sequence stars. We derive a disk mass of ∼ 0.3–1% of the mass of the central Brown Dwarf, similar to the typical values found for disks around more massive young stars. Accepted by ApJ Letters http://arxiv.org/pdf/1211.6743

Circum-planetary discs as bottlenecks for gas accretion onto giant planets Guillaume Rivier1,2, Aurélien Crida1, Alessandro Morbidelli1, Yann Brouet1,3 1 Laboratoire Lagrange, UMR7293, Universitéde Nice Sophia-antipolis/CNRS/Observatoire de la Côte d’Azur, B.P. 4229, 06304 Nice Cedex 4, France 2 Formation Supaéro, Institut Supérieur de l’Aéronautique et de l’Espace, 10 av. Edouard Belin, B.P. 94235, 31400 Toulouse Cedex 4, France 3 Laboratoire LERMA/Observatoire de Paris, 61 avenue de l’Observatoire, 75014, Paris, France With hundreds of exoplanets detected, it is necessary to revisit giant planets accretion models to explain their mass distribution. In particular, formation of sub-jovian planets remains unclear, given the short timescale for the runaway accretion of massive atmospheres. However, gas needs to pass through a circum-planetary disc. If the latter has a low viscosity (as expected if planets form in ”dead zones”), it might act as a bottleneck for gas accretion. We investigate what the minimum accretion rate is for a planet under the limit assumption that the circum-planetary disc is totally inviscid, and the transport of angular momentum occurs solely because of the gravitational perturbations from the star. To estimate the accretion rate, we present a steady-state model of an inviscid circum-planetary disc, with vertical gas inflow and external torque from the star. Hydrodynamical simulations of a circum-planetary disc were conducted in 2D, in a planetocentric frame, with the star as an external perturber in order to measure the torque exerted by the star on the disc. The disc shows a two-armed spiral wave caused by stellar tides, propagating all the way in from the outer edge of the disc towards the planet. The stellar torque is small and corresponds to a doubling time for a Jupiter mass planet of the order of 5 Myrs. Given the limit assumptions, this is clearly a lower bound of the real accretion rate. This result shows that gas accretion onto a giant planet can be regulated by circum-planetary discs. This suggests that the diversity of masses of extra-solar planets may be the result of different viscosities in these discs. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1211.1820

Tracing large-scale structures in circumstellar disks with ALMA Jan Philipp Ruge1, Sebastian Wolf1, Ana L. Uribe2,3 and Hubert H. Klahr2 1 Universität zu Kiel, Institut für Theoretische und Astrophysik, Leibnitzstr. 15, 24098 Kiel, Germany 2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

43 3 University of Chicago, The Department of Astronomy and Astrophysics, 5640 S. Ellis Ave, Chicago, IL 60637, USA E-mail contact: ruge at astrophysik.uni-kiel.de Context. Planets are supposed to form in circumstellar disks. The additional gravitational potential of a planet perturbs the disk and leads to characteristic structures, i.e. spiral waves and gaps, in the disk’s density profile. Aims. We perform a large-scale parameter study of the observability of these planet-induced structures in circumstellar disks in the (sub)mm wavelength range for the Atacama Large (Sub)Millimeter Array (ALMA). Methods. On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disk-planet models, we calculated the disk temperature structure and (sub)mm images of these systems. These were used to derive simulated ALMA images. Because appropriate objects are frequent in the Taurus-Auriga region, we focused on a distance of 140 pc and a declination of ≈ 20◦. The explored range of star-disk-planet configurations consists of six hydrodynamical simulations (including magnetic fields and different planet masses), nine disk sizes with outer radii ranging from 9 AU −7 −2 to 225AU, 15 total disk masses in the range between 2.67 · 10 M⊙ and 4.10 · 10 M⊙, six different central stars, and two different grain size distributions, resulting in 10 000 disk models. Results. On almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disk structures induced by planet-disk interaction or by the influence of magnetic fields on the wavelength range between 0.4 and 2.0 mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, within the range of typical masses of protoplanetary disks (0.1 M⊙ −−0.001M⊙) the disk mass has a minor impact on the · −6 Mp observability. It is possible to resolve disks down to 2.67 10 M⊙ and trace gaps induced by a planet with M⋆ =0.001 −4 in disks with 2.67 · 10 M⊙ with a signal-to-noise ratio greater than three. The central star has a major impact on the observability of gaps, as well as on the considered maximum grainsize of the dust in the disk. In general, it is more likely to trace planet-induced gaps in our magnetohydrodynamical disk models, because gaps are wider in the presence of magnetic fields. We also find that zonal flows resulting from magneto-rotational instability (MRI) create gap-like structures in the disk’s re-emission radiation, which are observable with ALMA. Conclusions. Through the unprecedented resolution and sensitivity of ALMA in the (sub)mm wavelength range, the expected detailed observations of planet-disk interaction and global disk structures will deepen our understanding of the planet formation and disk evolution process. Accepted by A&A

Initial phases of massive star formation in high infrared extinction clouds. II. Infall and onset of star formation K. L. J. Rygl1,2, F. Wyrowski2, F. Schuller3,2, K. M. Menten2 1 Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere 100, 00133 Roma, Italy 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 3 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile E-mail contact: kazi.rygl at inaf.it The onset of massive star formation is not well understood because of observational and theoretical difficulties. To find the dense and cold clumps where massive star formation can take place, we compiled a sample of high infrared extinction clouds. We observed the clumps in these high extinction clouds in the 1.2 mm continuum emission and ammonia with the goals of deriving the masses, densities, temperatures, and kinematic distances. We try to understand the star- formation stages of the high extinction clumps by studying their infall and outflow properties, the presence of a young stellar object (YSO), and the level of the CO depletion. Are the physical parameters, density, mass, temperature, and column density correlated with the star-forming properties? Does the cloud morphology, quantified through the column density contrast between the clump and the clouds, have an impact on the evolution of star formation occurring inside it? Star-formation properties, such as infall, outflow, CO depletion, and the presence of YSOs, were derived from a molecular line survey performed with the IRAM 30m and the APEX 12m telescopes. We find that the HCO+(1–0) transition is the most sensitive for detecting infalling motions. SiO, an outflow tracer, was mostly detected toward sources with infall, indicating that infall is accompanied by collimated outflows. We calculated infall velocities from the line profiles and found them to be of the order of 0.3–7 km s−1. The presence of YSOs within a clump depends mostly on the clump column density; no indication of YSOs were found below 4 × 1022 cm−2. Star formation is on the verge of beginning in clouds that have a low column density contrast; the infall is not yet present in the majority of the clumps. The first signs of ongoing star formation are broadly observed in clouds where the column

44 density contrast between the clump and the cloud is higher than two; most clumps show infall and outﬂow. Finally, we ﬁnd the most evolved clumps in clouds that have a column density contrast higher than three; in many clumps, the infall has already halted, and toward most clumps we found indications of YSOs. Hence, the cloud morphology, based on the column density contrast between the cloud and the clumps, seems to have a direct connection with the evolutionary stage of the objects forming inside. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1210.2063

Recent star formation in the Lupus clouds as seen by Herschel K. L. J. Rygl1, M. Benedettini1, E. Schisano1, D. Elia1, S. Molinari1, S. Pezzuto1, Ph. André2, J. P. Bernard3, G. J. White4,5, D. Polychroni6,1, S. Bontemps7,2, N. L. J. Cox8, J. Di Francesco9,10, A. Facchini1, C. Fallscheer9,10, A. M. di Giorgio1, M. Hennemann2, T. Hill2, V. Könyves2, V. Minier2, F. Motte2, Q. Nguyen-Luong11, N. Peretto2, M. Pestalozzi1, S. Sadavoy9,10, N. Schneider7,2, L. Spinoglio1, L. Testi12,13, D. Ward-Thompson14 1 Istituto di Astrofisica e Planetologia Spaziali, via del Fosso del Cavaliere 100, 00133 Roma, Italy 2 Laboratoire AIM Paris-Saclay, CEA/IRFU CNRS/INSU UniversitéParis Diderot, 91191 Gif-sur-Yvette, France 3 CESR, Observatoire Midi-Pyrnes (CNRS-UPS), Universitéde Toulouse, BP 44346, 31028 Toulouse, France 4 Rutherford Appleton LIbrary, Chilton, Didcot, OX11 0NL, UK 5 Department of Physics and Astronomy, Open University, Milton Keynes, UK 6 University of Athens, Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis, 15784 Zografos, Athens, Greece 7 CNRS/INSU, Laboratoire d’Astrophysique de Bordeaux UMR 5904, BP 89, 33271 Floirac, France 8 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium 9 Department of Physics and Astronomy, University of Victoria, PO Box 355, STN CSC, Victoria BC Canada, V8W 3P6 10 National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria BC Canada, V9E 2E7 11 Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto, 60 St. George Street, Toronto ON Canada, M5S 3H8 12 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 87548 Garching bei München, Germany 13 INAF-Osservatorio Astrofisico di Arcetri, Large E. Fermi 5, 50125 Firenze, Italy 14 Jeremiah Horrocks Institute, University of Central Lancashire, PR1 2HE, UK E-mail contact: kazi.rygl at inaf.it We present a study of the star formation histories of the Lupus I, III, and IV clouds using the Herschel 70–500 µm maps obtained by the Herschel Gould Belt Survey Key Project. By combining the new Herschel data with the existing Spitzer catalog we obtained an unprecedented census of prestellar sources and young stellar objects in the Lupus clouds, which allowed us to study the overall star formation rate (SFR) and efficiency (SFE). The high SFE of Lupus III, its decreasing SFR, and its large number of pre-main sequence stars with respect to proto- and prestellar sources, suggest that Lupus III is the most evolved cloud, and after having experienced a major star formation event in the past, is now approaching the end of its current star-forming cycle. Lupus I is currently undergoing a large star formation event, apparent by the increasing SFR, the large number of prestellar objects with respect to more evolved objects, and the high percentage of material at high extinction (e.g., above AV ≈ 8mag). Also LupusIV has an increasing SFR; however, the relative number of prestellar sources is much lower, suggesting that its star formation has not yet reached its peak. Accepted by Astronomy and Astrophysics Letters http://arxiv.org/pdf/1211.5232

The Initial Mass Function and the Surface Density Proﬁle of NGC 6231 Hwankyung Sung1, Hugues Sana2, and M. S. Bessell3 1 Department of Astronomy and Space Science, Sejong University, 98, Kunja-dong, Kwangjin-gu, Seoul 143-747, Korea 2 Astronomical Institute ’Anton Pannekeok’, Amsterdam University, Science Park 904, 1098 XH, Amsterdam, The

45 Netherlands 3 Research School of Astronomy and Astrophysics, Australian National University, MSO, Cotter Road, Weston, ACT 2611, Australia E-mail contact: sungh at sejong.ac.kr We have performed new wide-field photometry of the young open cluster NGC 6231 to study the shape of the initial mass function (IMF) and mass segregation. We also investigated the reddening law toward NGC 6231 from optical to mid-infrared color excess ratios, and found that the total-to-selective extinction ratio is RV = 3.2, which is very close to the normal value. But many early-type stars in the cluster center show large color excess ratios. We derived the surface density profiles of four member groups, and found that they reach the surface density of field stars at about 10′, regardless of stellar mass. The IMF of NGC 6231 is derived for the mass range 0.8 – 45 M⊙. The slope of the IMF of NGC 6231 (Γ = −1.1 ± 0.1) is slightly shallower than the canonical value, but the difference is marginal. In addition, the mass function varies systematically, and is a strong function of radius - it is very shallow at the center, and very steep at the outer ring suggesting the cluster is mass segregated. We confirm the mass segregation for the massive stars (m >∼ 8 M⊙) by a minimum spanning tree analysis. Using a Monte Carlo method, we estimate the total mass 3 of NGC 6231 to be about 2.6(±0.6) × 10 M⊙. We constrain the age of NGC 6231 by comparison with evolutionary isochrones. The age of the low-mass stars ranges from 1 to 7 Myr with a slight peak at 3 Myr. However the age of the high mass stars depends on the adopted models and is 3.5 ± 0.5 Myr from the non- or moderately-rotating models of Brott et al. as well as the non-rotating models of Ekström et al. But the age is 4.0 – 7.0 Myr if the rotating models of Ekström et al. are adopted. This latter age is in excellent agreement with the time scale of ejection of the high mass runaway star HD 153919 from NGC 6231, albeit the younger age cannot be entirely excluded. Accepted by the Astronomical Journal http://arxiv.org/pdf/1211.4278

Hierarchical Fragmentation of the Orion Molecular Filaments Satoko Takahashi1, Paul T. P. Ho1,2, Paula S. Teixeira3,4, Luis A. Zapata5 and Yu-Nung Su1 1 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-131, Taipei, Taiwan 2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street Cambridge, MA 02138, USA 3 Universitaet Wien, Institut fuer Astrophysik, Tuerkenschanzstrasse 17, 1180, Wien, Austria 4 Laboratório Associado Instituto D. Luiz-SIM, Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal 5 Centro de Radioastronom´ıay Astrof´ısica, Universidad Nacional Autónoma de México, Morelia, Michoacán 58090, México E-mail contact: satoko t at asiaa.sinica.edu.tw We present a high angular resolution map of 850 µm continuum emission of the Orion Molecular Cloud-3 (OMC 3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximate ′ ′ area of 6 .5×2 .0 (0.88×0.27 pc). We detect 12 spatially resolved continuum sources, each with an H2 mass between 0.3–5.7 M⊙ and a projected source size between 1400–8200 AU. All the detected sources are on the filamentary main 6 −3 ridge (nH2 ≥10 cm ), and analysis based on the Jeans theorem suggests that they are most likely gravitationally unstable. Comparison of multi-wavelength data sets indicates that of the continuum sources, 6/12 (50 %) are associated with molecular outflows, 8/12 (67 %) are associated with infrared sources, and 3/12 (25 %) are associated with ionized jets. The evolutionary status of these sources ranges from prestellar cores to protostar phase, confirming that OMC-3 is an active region with ongoing embedded star-formation. We detect quasi-periodical separations between the OMC- 3 sources of ≈17′′/0.035 pc. This spatial distribution is part of a large hierarchical structure, that also includes fragmentation scales of GMC (≈35 pc), large-scale clumps (≈1.3 pc), and small-scale clumps (≈0.3 pc), suggesting that hierarchical fragmentation operates within the Orion A molecular cloud. The fragmentation spacings are roughly consistent with the thermal fragmentation length in large-scale clumps, while for small-scale cores it is smaller than the local fragmentation length. These smaller spacings observed with the SMA can be explained by either a helical magnetic field, cloud rotation, or/and global filament collapse. Finally, possible evidence for sequential fragmentation is suggested in the northern part of the OMC-3 filament. Accepted by Astrophysical Journal http://arxiv.org/pdf/1211.6842

46 A 0.2 solar mass protostar with a Keplerian disk in the very young L1527 IRS system John J. Tobin1, Lee Hartmann2, Hsin-Fang Chiang3,4, David J. Wilner5, Leslie W. Looney3, Laurent Loinard6,7, Nuria Calvet2 and Paola D’Alessio6 1 Hubble Fellow, National Radio Astronomy Observatory, Charlottesville, VA 2 University of Michigan 3 University of Illinois 4 Institute for Astronomy, University of Hawaii at Manoa 5 Harvard-Smithsonian Center for Astrophysics 6 Centro de Radioastronomia y Astrofisica, UNAM 7 Max-Planck-Institut fur Radioastronomie E-mail contact: jtobin at nrao.edu In their earliest stages, protostars accrete mass from their surrounding envelopes through circumstellar disks. Until now, the smallest observed protostar/envelope mass ratio was ∼2.1. The protostar L1527 IRS is thought to be in the earliest stages of star formation. Its envelope contains ∼1 solar mass of material within a ∼0.05 pc radius, and earlier observations suggested the presence of an edge-on disk. Here we report observations of dust continuum emission and 13 CO (J = 2 → 1) line emission from the disk around L1527, from which we determine a protostellar mass of M∗ = 0.19 ± 0.04 solar masses and a protostar/envelope mass ratio of ∼0.2. We conclude that most of the luminosity is generated through the accretion process, with an accretion rate of ∼6.6× 10−7 solar masses yr−1. If it has been accreting at that rate through much of its life, its age is ∼300,000 yr, though theory suggests larger accretion rates earlier, so it may be younger. The presence of a rotationally–supported disk is confirmed and significantly more mass may be added to its planet-forming region as well as the protostar itself. Accepted by Nature (Dec 5, 2012 issue) http://www.cv.nrao.edu/~jtobin/L1527-nature.pdf

Tearing the Veil: interaction of the Orion Nebula with its neutral environment Paul P. van der Werf1,2, W. M. Goss3, C. R. O’Dell4 1 Leiden Observatory, Leiden University, P.O. Box 9513, NL 2300 RA Leiden, The Netherlands 2 SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, United Kingdom 3 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801, USA 4 Department of Physics and Astronomy, Vanderbilt University, Box 1807-B, Nashville, TN 37235, USA E-mail contact: pvdwerf at strw.leidenuniv.nl We present HI 21cm observations of the Orion Nebula, obtained with the Karl G. Jansky Very Large Array, at an angular resolution of 7.2′′×5.7′′ and a velocity resolution of 0.77 km s−1. Our data reveal HI absorption towards the radio continuum of the HII region, and HI emission arising from the Orion Bar photon-dominated region (PDR) and from the Orion-KL outflow. In the Orion Bar PDR, the HI signal peaks in the same layer as the H2 near-infrared vibrational line emission, in agreement with models of the photodissociation of H2. The gas temperature in this region is approximately 540 K, and the HI abundance in the interclump gas in the PDR is 5–10% of the available hydrogen nuclei. Most of the gas in this region therefore remains molecular. Mechanical feedback on the Veil manifests itself through the interaction of ionized flow systems in the Orion Nebula, in particular the Herbig-Haro object HH202, with the Veil. These interactions give rise to prominent blueward velocity shifts of the gas in the Veil. The unambiguous evidence for interaction of this flow system with the Veil shows that the distance between the Veil and the Trapezium stars needs to be revised downwards to about 0.4 pc. The depth of the ionized cavity is about 0.7 pc, which is much smaller than the depth and the lateral extent of the Veil. Our results reaffirm the blister model for the M42 HII region, while also revealing its relation to the neutral environment on a larger scale. Accepted for publication in the Astrophysical Journal http://arxiv.org/pdf/1211.0470

47 Distance and Kinematics of the TW Hydrae Association from Parallaxes Alycia J. Weinberger1, Guillem Anglada-Escudé2, Alan P. Boss3 1 Department of Terrestrial Magnetism, Carnegie Institution of Washington 5241 Broad Branch Road NW, Washing- ton, DC 20015, USA 2 Universität Göttingen, Institut für Astrophysik Friedrich-Hund-Platz 1, 37077 Göttingen, Germany 3 Department of Terrestrial Magnetism, Carnegie Institution of Washington 5241 Broad Branch Road NW, Washing- ton, DC 20015, USA E-mail contact: weinberger at dtm.ciw.edu From common proper motion and signatures of youth, researchers have identified about 30 members of a putative TW Hydrae Association. Only four of these had parallactic distances from Hipparcos. We have measured parallaxes and proper motions for 14 primary members. We combine these with literature values of radial velocities to show that the Galactic space motions of the stars, with the exception of TWA 9 and 22, are parallel and do not indicate convergence at a common formation point sometime in the last few million years. The space motions of TWA 9 and 22 do not agree with the others and indicate that they are not TWA members. The median parallax is 18 mas or 56 pc. We further analyze the stars’ absolute magnitudes on pre-main sequence evolutionary tracks and find a range of ages with a median of 10.1 Myr and no correlation between age and Galactic location. The TWA stars may have formed from an extended and filamentary molecular cloud but are not necessarily precisely coeval. Accepted by ApJ http://arxiv.org/pdf/1211.2233

Massive Star Formation, Outflows, and Anomalous H2 Emission in Mol 121 (IRAS 20188+3928) Grace Wolf-Chase1,2, Kim Arvidsson1, Michael Smutko3 and Reid Sherman2 1 Astronomy Department, Adler Planetarium, 1300 S. Lake Shore Dr., Chicago, IL 60605, USA 2 Department of Astronomy & Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, USA 3 CIERA and Department of Physics & Astronomy, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208, USA E-mail contact: gwolfchase at adlerplanetarium.org We have discovered 12 new molecular hydrogen emission-line objects (MHOs) in the vicinity of the candidate massive young stellar object Mol 121, in addition to five that were previously known. H2 2.12-µm/H2 2.25-µm flux ratios indicate another region dominated by fluorescence from a photo-dissociation region (PDR), and one region that displays an anomalously low H2 2.12-µm/H2 2.25-µm flux ratio (<1) and coincides with a previously reported deeply embedded source (DES). Continuum observations at 3 mm reveal five dense cores; the brightest core is coincident with the DES. The next brightest cores are both associated with cm continuum emission. One of these is coincident with the IRAS source; the other lies at the centroid of a compact outflow defined by bipolar MHOs. The brighter of these bipolar MHOs exhibits [Fe II] emission and both MHOs are associated with CH3OH maser emission observed at 95 GHz and 44 GHz. Masses and column densities of all five cores are consistent with theoretical predictions for massive star formation. Although it is impossible to associate all MHOs with driving sources in this region, it is evident that there are several outflows along different position angles, and some unambiguous associations can be made. We discuss implications of observed H2 2.12-µm/H2 2.25-µm and [Fe II] 1.64-µm/H2 2.12-µm flux ratios and compare the estimated total H2 luminosity with the bolometric luminosity of the region. We conclude that the outflows are driven by massive young stellar objects embedded in cores that are likely to be in different evolutionary stages. Accepted by The Astrophysical Journal http://arxiv.org/pdf/1211.3440

48 CO J =2 − 1 and CO J =3 − 2 observations toward the high-mass protostellar candidate IRAS 20188+3928 Jin-Long Xu1,2 and Jun-Jie Wang1,2 1 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China 2 NAOC-TU Joint Center for Astrophysics, Lhasa 850000, China E-mail contact: xujl at bao.ac.cn We have carried out 12CO J = 2 − 1 and 12CO J = 3 − 2 observations toward the high-mass protostellar candidate IRAS 20188+3928. Compared with previous observations, the 12CO J = 2 − 1 and 12CO J = 3 − 2 lines both have asymmetric profiles with an absorption dip. The velocity of the absorption dip is 1.0 km s−1. The spectral shape may be caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12CO J = 2 − 1 line present an obvious bipolar component, further verifying that this region has an outflow motion. This region is also associated with an HII region, an IRAS source, and an H2O maser. The H2O maser has the velocity of 1.1 km −1 s . Compared with the components of the outflow, we find that the H2O maser is not associated with the outflow. Using the large velocity gradient model, we concluded that possible averaged gas densities of the blueshifted lobe and redshifted lobe are 1.0 × 105 cm−3 and 2.0 × 104 cm−3, while kinetic temperatures are 26.9 K and 52.9 K, respectively. Additionally, the outflow has a higher integrated intensity ratio (ICO J=3−2/ICO J=2−1). Accepted by Research in Astronomy and Astrophysics http://arxiv.org/pdf/1211.3834

A mapping study of L1174 with 13CO J = 2 − 1 and 12CO J = 3 − 2: star formation triggered by a Herbig Ae/Be star Jing-Hua Yuan1, Yuefang Wu2, Jin Zeng Li1, Wentao Yu2, Martin Miller3 1 National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, China 2 Department of Astronomy, Peking University, 100871 Beijing, China 3 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Cologne, Germany E-mail contact: ywu at pku.edu.cn We have carried out a comprehensive study of the molecular conditions and star-forming activities in dark cloud L1174 with multi-wavelength data. Mapping observations of L1174 in 13CO J =2 − 1 and 12CO J =3 − 2 were performed using the KOSMA 3-meter telescope. Six molecular cores with masses ranging from 5 to 31 M⊙ and sizes ranging from 0.17 to 0.39 pc are resolved. Large area ahead of a Herbig Be star, HD 200775, is in expanding and core 1 is with collapse signature. Large line widths of 13CO J = 2 − 1 indicate the ubiquity of turbulent motions in this region. Spectra of 12CO J =3 − 2 prevalently show conspicuously asymmetric double-peaked profiles. In a large area, red-skewed profiles are detected and suggestive of a scenario of global expansion. There is a large cavity around the Herbig Be star HD 200775, the brightest star in L1174. The gas around the cavity has been severely compressed by the stellar winds from HD 200775. Feedbacks from HD 200775 may have helped form the molecular cores around the cavity. Seventeen 2MASS potential young stellar objects were identified according to their 2MASS colour indices. The spatial distribution of the these 2MASS sources indicates that some of them have a triggered origin. All these suggest that feedbacks from a Herbig Ae/Be star may also have the potential to trigger star forming activities. Accepted for publication in MNRAS http://arxiv.org/pdf/1211.1430

Orbital and Mass Ratio Evolution of Protobinaries Driven by Magnetic Braking Bo Zhao and Zhi-Yun Li1 1 Dept. of Astronomy, University of Virginia, 530 McCormick Rd., Charlottesville, VA 22904, USA E-mail contact: bz6g at virginia.edu The majority of stars reside in multiple systems, especially binaries. The formation and early evolution of binaries is a

49 longstanding problem in star formation that is not yet fully understood. In particular, how the magnetic field observed in star-forming cores shapes the binary characteristics remains relatively unexplored. We demonstrate numerically, using an MHD version of the ENZO AMR hydro code, that a magnetic field of the observed strength can drastically change two of the basic quantities that characterize a binary system: the orbital separation and mass ratio of the two components. Our calculations focus on the protostellar mass accretion phase, after a pair of stellar “seeds” have already formed. We find that, in dense cores magnetized to a realistic level, the angular momentum of the material accreted by the protobinary is greatly reduced by magnetic braking. Accretion of strongly braked material shrinks the protobinary separation by a large factor compared to the non-magnetic case. The magnetic braking also changes the evolution of the mass ratio of unequal-mass protobinaries by producing material of low specific angular momentum that accretes preferentially onto the more massive primary star rather than the secondary. This is in contrast with the preferential mass accretion onto the secondary previously found numerically for protobinaries accreting from an unmagnetized envelope, which tends to drive the mass ratio towards unity. In addition, the magnetic field greatly modifies the morphology and dynamics of the protobinary accretion flow. It suppresses the traditional circumstellar and circumbinary disks that feed the protobinary in the non-magnetic case; the binary is fed instead by a fast collapsing pseudodisk whose rotation is strongly braked. The magnetic braking-driven inward migration of binaries from their birth locations may be constrained by high-resolution observations of the orbital distribution of deeply embedded protobinaries, especially with ALMA and JVLA. Accepted by ApJ http://arxiv.org/pdf/1210.2308

Abstracts of recently accepted major reviews

Our Astrochemical Heritage Paola Caselli1 & Cecilia Ceccarelli2 1 School of Physics and Astronomy, Univ. of Leeds, Leeds LS2 9JT, UK 2 Institut de Planétologie et d’Astrophysique de Grenoble, Grenoble, F-38041, France E-mail contact: [email protected] Our Sun and planetary system were born about 4.5 billion years ago. How did this happen and what is our heritage from these early times? This review tries to address these questions from an astrochemical point of view. On the one hand, we have some crucial information from meteorites, comets and other small bodies of the Solar System. On the other hand, we have the results of studies on the formation process of Sun-like stars in our Galaxy. These results tell us that Sun-like stars form in dense regions of molecular clouds and that three major steps are involved before the planet formation period. They are represented by the pre-stellar core, protostellar envelope and protoplanetary disk phases. Simultaneously with the evolution from one phase to the other, the chemical composition gains increasing complexity. In this review, we first present the information on the chemical composition of meteorites, comets and other small bodies of the Solar System, which is potentially linked to the first phases of the Solar System’s formation. Then we describe the observed chemical composition in the pre-stellar core, protostellar envelope and protoplanetary disk phases, including the processes that lead to them. Finally, we draw together pieces from the different objects and phases to understand whether and how much we inherited chemically from the time of the Sun’s birth. Accepted by The Astronomy and Astrophysics Review http://arxiv.org/pdf/1210.6368

50 The Dawn of Chemistry Daniele Galli & Francesco Palla INAF-Osservatorio Astrofisico di Arcetri Largo E. Fermi 5, 50125 Firenze, Italy E-mail contact: [email protected] Within the precise cosmological framework provided by the Lambda-Cold Dark Matter model and standard Big Bang nucleosynthesis, the chemical evolution of the pregalactic gas can now be followed with accuracy limited only by the uncertainties on the reaction rates. Starting during the recombination era, the formation of the first molecules and molecular ions containing hydrogen, deuterium, helium, and lithium was severely hindered by the low density of the expanding universe, the intensity of the cosmic radiation field, and the absence of solid catalyzers. Molecular hydrogen and deuterated hydrogen, the most abundant species formed in the gas phase prior to structure formation, played a fundamental role in the cooling of the gas clouds that gave birth to the first stellar generation, contributing to determine the scale of fragmentation. Primordial molecules also interacted with the photons of the cosmic background via resonant scattering, absorption and emission. In this review we examine the current status of the chemistry of the early universe and discuss the most relevant reactions for which uncertainties still exist from theory or laboratory experiments. The prospects for detecting spectral distortions or spatial anisotropies due to the first atoms and molecules are also addressed. Accepted by Annual Review Astron. Astrophys. http://arxiv.org/pdf/1211.3319

Evolution of Star Formation and Gas Nick Z. Scoville1 1 Caltech, Pasadena, CA 91125, USA E-mail contact: nzs at radio.caltech.edu In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to develop a physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material is drawn from early work in the ﬁeld since much of the work was done two decades ago and this background is not generally available in the present literature. I also attempt to synthesise our well-developed understanding of star formation in low-redshift galaxies with constraints from theory and observations at high redshift to develop an intuitive model for the evolution of galaxy mass and luminosity functions in the early Universe. The overall goal of this contribution is to provide students with background helpful for analysis of far-infrared (FIR) observations from Herschel and millimetre/submillimetre (mm/submm) imaging with ALMA (the Atacama Large Millimetre/submillimetre Array). These two instruments will revolutionise our understanding of the interstellar medium (ISM) and associated star formation and galaxy evolution, both locally and in the distant Universe. To facilitate interpreting the FIR spectra of Galactic star-forming regions and high-redshift sources, I develop a model for the dust heating and radiative transfer in order to elucidate the observed infrared (IR) emissions. I do this because I am not aware of a similar coherent discussion in the literature. Accepted by Cambridge University Press, Proceedings of the XXIII Canary Islands Winter School of Astrophysics ”Secular Evolution of Galaxies” http://arxiv.org/pdf/1210.6990

51 Dissertation Abstracts

Instabilities in supersonic cloud–cloud collisions Andrew McLeod

Thesis work conducted at: Cardiﬀ University, United Kingdom Current address: Astrophysics Group, University of Exeter, Stocker Road, EXETER, EX4 4QL, United Kingdom Electronic mail: [email protected] Ph.D dissertation directed by: Prof Anthony Whitworth Ph.D degree awarded: October 2012

We study the effects of the supersonic collision of molecular clouds using smoothed particle hydrodynamics (SPH) simulations. We review the observational evidence for cloud–cloud collision and previous computational work. We describe the SPH method, the algorithms used in the SPH code SEREN (Hubber 2011), and how we have extended the parallelization of SEREN. We review the non-linear thin shell instability (NTSI) and gravitational instability in a shock-compressed layer. We present the results of two sets of SPH simulations. In the first set of simulations we collide supersonic flows of gas without self-gravity. We impose a range of velocity perturbations, including monochromatic perturbations, white noise perturbations and both subsonic and supersonic turbulence. The colliding flows create a dense shock-compressed layer which is unstable to the NTSI. We examine the effect of the differing initial perturbations on the NTSI, and calculate rates of growth of both bending modes and breathing modes as a function of time and wavenumber. We compare our results to the time-independent result predicted by Vishniac (1994) for a one-dimensional monochromatic perturbation, and examine how this result can be extended to two-dimensional perturbations and non-monochromatic perturbations. In our second set of simulations we model the head-on supersonic collision of two identical uniform-density spheres. We include self-gravity, allowing the dense layer to become gravitationally unstable and produce stars. We explore the effect of increasing collision velocity, and show that the NTSI is present only at higher collision velocities. At the highest collision velocities the NTSI severely disrupts the layer, and the collision does not produce stars. Although the global properties of the collision, such as the thickness of the layer, the size of the star-forming region and the time of first star formation, depend on the collision velocity, most individual properties of the stars do not. Thesis available online at: http://orca.cf.ac.uk/38842/

52 A comprehensive study of the young star cluster HD 97950 in NGC 3606 Xiaoying Pang

Heidelberg University Key Lab for Astrophysics, Mbox 336 Room 301, Building 10, Shanghai Normal University, 100 Guilin Road, Shanghai 200234 Electronic mail: xiaoying0759 at gmail.com Ph.D dissertation directed by: Prof. Dr. Eva Grebel Ph.D degree awarded: May 2012

I study the young massive star cluster HD 97950 located in the Galactic giant H ii region NGC3603. My goals are (1) to estimate the survival probability of the cluster, (2) to investigate the origin of its mass segregation, and (3) to investigate the interplay between the cluster and the surrounding interstellar medium (ISM). All the studies are done with data of the Hubble Space Telescope. I determine the cluster velocity dispersion from the stars’ relative proper motions, and calculate the virial mass of the cluster. The cluster star formation efficiency is estimated to be about 50%, which suggests that the HD 97950 cluster will most likely survive as a bound cluster to gas expulsion. I apply the Λ minimum spanning tree technique to measure the mass segregation down to 30M⊙. The high-mass stars are more segregated than low-mass stars, implying that the mass segregation in HD 97950 is mostly of dynamical origin. To improve the age determination for the cluster stars that are severely reddened by the surrounding dusty ISM, I compute a pixel-to-pixel distribution of the gas reddening, E(B − V )g, associated with the cluster. The radial profiles of E(B − V )g show significant spatial variations around HD 97950. Using UBVRI photometry, I estimate the stellar reddening of cluster stars. After correcting for foreground reddening, the total to selective extinction ratio in the cluster is RV =3.49 ± 0.79. The extinction curve in the UBV RI filters in the cluster is greyer than the average Galactic extinction laws, but close to the extinction law for starburst galaxies. This indicates that stellar feedback from massive stars changes the dust properties in the HD97950 cluster in a similar way as in starburst galaxies. http://archiv.ub.uni-heidelberg.de/volltextserver/volltexte/2012/13399/

53 New Jobs

Planetary Collisional Modeling

Arizona State University’s School of Earth and Space Exploration (SESE) is recruiting a Postgraduate Researcher in planetary collisional modeling, with an emphasis on early solar system bodies (e.g. planetary embryos, asteroids, comets, satellites, KBOs, ice giants). An earned PhD in Planetary Sciences, Astrophysics, Geophysics, Computer Modeling, or a related field is required. The successful applicant will have a demonstrated capability of using computer models to tackle large-scale problems in astrophysics, geophysics, granular physics or fluid dynamics, and will have some familiarity with the theory of hydrocodes, and a demonstrated ability to mine/reduce/visualize large quantities of 3D simulation data and analyze and clearly present the results. An academic track record in planet formation and evolution is desired but not required. The position is intended to bring a talented scholar to the forefront of this exciting and expanding arena of research, working closely with Prof. Erik Asphaug and his colleagues and students. The successful applicant will lead at least one first-author paper per year, so a record of research publication is required. The position includes funding for travel to one domestic and one international conference per year, and dedicated access to the world-class computational facilities at ASU. Applications are due by January 31, 2013 and reference letters by February 7, 2013 via email to [email protected]. A full description of the application process is available at http://sese.asu.edu/opportunities. The appointment will start on or after March 1, 2013, and the position will remain open until filled. Salaries are competitive, and commensurate with research experience. Students finishing their PhDs by July 2013 are encouraged to apply, as are applicants with postgraduate experience looking for a new position. The initial appointment will be for 2 years. ASU is an equal opportunity/affirmative action employer that actively seeks diversity among applicants and promotes a diverse workforce.

Florida Theoretical Astrophysics Postdoctoral Fellowship(s)

The University of Florida (UF) Department of Astronomy invites applications for one or more postdoctoral fellowship positions in the Theoretical Astrophysics Group, with at least one appointment expected in the fields of star and/or planet formation. The anticipated start date is in Fall 2013. Successful candidate(s) will be expected to carry out original research in theoretical astrophysics, independently and/or in collaboration with UF faculty in the Astronomy and/or Physics departments. They will have access to the UF High Performance Computing Center, as well as observational facilities. UF also has active observational and instrumentation groups. Candidates are encouraged to propose theoretical research that relates to existing research programs and/or facilities at UF, including exoplanets, solar system studies, star and galaxy formation, and stellar populations. Further information, including a list of faculty and their research interests, is available at www.astro.ufl.edu. The appointment is renewable annually for up to 3 years based on satisfactory performance, needs of the Departments and College, and available funding. A Ph.D. in a relevant field by the starting date is required. Application materials (CV, publications list, statement of research interests and plans (max 5 pages), and three letters of reference) should be emailed to [email protected]fl.edu. Application materials should be received by January 1, 2013 to ensure full consideration. For more information about the position, please contact Profs. Eric Ford, Anthony Gonzalez or Jonathan Tan. The University of Florida is an Equal Opportunity Institution. Included Benefits: Successful candidates will be eligible for benefits, including health care plans.

54 Postdoctoral Fellowship in Star and Planet Formation

The School of Physics and Astronomy at the University of Leeds invites applications for a postdoctoral fellowship in star and planet formation. The applicant is expected to work with Prof. Paola Caselli (and a team funded by the European Research Council) to study star and planet formation, from the earliest phases of pre-stellar cores to the formation of protoplanetary disks. The overall aim of the project is to merge theoretical astrochemical, magneto-hydrodynamical and radiative transfer models, and constrain them by detailed observations. Researchers with experience in star and planet formation theory and/or observations are encouraged to apply. Leeds has a very active research group in star and planet formation, also including Profs. Falle, Hartquist, Hoare, Oudmaijer and Drs. Lumsden and Pittard. Leeds has recently invested in a High Performance Computing (HPC) cluster (475 quad-core - i.e. 1900 cores - 2.8 GHz Intel Nehalem CPUs with 6 GB RAM per CPU). The University’s membership in the White Rose Grid and its status in a National Grid Node ensure continued cost eﬀective and high quality support. The investment in infrastructure has also made it possible for Leeds to host one of the UKMHD clusters recently funded under the STFC HPC initiative, which will make around another 2000 cores available. Salaries and duration of appointments (2+1 years, up to a maximum of 5 years) will be commensurate with experience. Applications should consist of a CV, a brief description of past/current research and a list of publications. The application, as well as three letters of reference (sent directly by the referees), should be sent electronically to [email protected]. Review of applications will begin on February 15th, 2013 and will continue until the position is ﬁlled. For more information, please send an email to Prof. P. Caselli ([email protected]).

Postdoctoral Position in Magnetism of Young Solar-type Stars

A 17-month post-doctoral position is available at IRAP (Institut de Recherche en Astrophysique et Planétologie, Toulouse University & CNRS, Toulouse, France), in the field of magnetism and activity of young solar-type stars. The position is supported by ANR (Agence Nationale de la Recherche). The successful candidate will investigate the surface magnetism of cool open cluster stars and weak-line T Tauri stars, using time-series collected with the ESPaDOnS and NARVAL stellar spectropolarimeters. The candidate will be involved at all stages of this ongoing survey, from the preparation of future proposals to the acquisition, analysis and interpretation of data sets. The derived magnetic properties will be employed to study the evolution of dynamo processes and the related spindown of cool active stars, prior to the main sequence. The successful candidate will be in constant interaction with the teams of Toulouse (IRAP), Grenoble (IPAG), Saclay (CEA) and Montpellier (LUPM) involved in the observational and theoretical aspects of this project. The ideal candidate is experienced in high-resolution spectroscopy and/or spectropolarimetry and has a background or experience in high-level modeling of spectroscopic data, including multi-line analysis and tomographic imaging. The candidates, of any nationality, should have obtained by the starting date a Ph.D. in astronomy or a related field, with specialization in one of the areas of study listed above. The start date of the appointment is flexible, but should be no later than March 2013. Candidates should submit a curriculum vitae, a summary of current and future research interests, a list of publications and two letters of recommendation to Pascal Petit ([email protected]) before 2012 December 19. Further information on the project can be found on the TOUPIES webpage: http://ipag.osug.fr/Anr_Toupies/spip.php?rubrique2

Postdoc Position in Star Formation at CEA Saclay

We invite applications to ﬁll two postdoctoral research positions in the Astrophysical Group (SAp) at CEA/Saclay in the context of the MAGMIST project, a ﬁve-year founded program of the European Research Council (ERC). It is

55 centered on a detailed investigation of the star formation process from galactic to molecular core scales using mainly three dimensional numerical simulations, analytical modeling and confrontation with observations. The successful candidates should have an experience in at least one of the following topics: large numerical simulations, fluid dynamics, star formation or interstellar medium. The project offers competitive salaries and money for traveling. All positions are for four years and include full benefit. The CEA/Saclay group has extensive expertize in heavy computation and easy access to local and national computing facilities and hosts both observers and theorists. Required application materials include a CV, a bibliography, a statement of research interests and three letters of recommendation and should be send by regular mail or email to : Dr Patrick Hennebelle SAp - CEA/Saclay 91191 Gif-sur-Yvette France

Moving ... ??

If you move or your e-mail address changes, please send the editor your new address. If the Newsletter bounces back from an address for three consecutive months, the address is deleted from the mailing list.

56 Meetings of Possible Interest

Exoplanets in Multi-body Systems in the Kepler Era 9 - 16 February 2013 Aspen, CO, USA http://www.astro.ufl.edu/~eford/meetings/aspen2013/ Characterising Exoplanets: Detection, Formation, Interiors, Atmospheres and Habitability 11 - 12 March 2013 The Royal Society, London, UK http://royalsociety.org/events/2013/exoplanets/ 43nd Saas-Fee Course: Star Formation in Galaxy Evolution: Connecting Numerical Models to Reality 11 - 16 March 2013 Villars-sur-Ollon, Switzerland http://lastro.epfl.ch/conferences/sf2013 Infrared and Submillimeter Probes of Gas in Galaxies: From the Milky Way to the Distant Universe 17 - 20 March 2013 Pasadena, CA USA http://conference.ipac.caltech.edu/gasconf/ From Stars to Life - Connecting our Understanding of Star Formation, Planet Formation, Astrochem- istry and Astrobiology 3 - 6 April 2013 Gainesville, Florida, USA http://conference.astro.ufl.edu/STARSTOLIFE/ StarBench: A Workshop for the Benchmarking of Star Formation Codes 8 - 11 April 2013 University of Exeter, UK http://www.astro.ex.ac.uk/people/haworth/workshop_bench/index.html Transformational Science with ALMA: From Dust to Rocks to Planets - Formation and Evolution of Planetary Systems 8 - 12 April 2013 Hilton Waikoloa Village, The Big Island of Hawaii, USA http://www.cv.nrao.edu/rocks/index.html International Young Astronomer School on Exploiting the Herschel and Planck data 15 - 19 April 2013 Meudon, France http://ufe.obspm.fr/rubrique344.html Habitable Worlds Across Time and Space 29 April - 2 May 2013 Space Telescope Science Institute, Baltimore, USA http://www.stsci.edu/institute/conference/habitable-worlds Ice and Planet Formation 15 - 17 May 2013 Lund Observatory, Sweden http://www.astro.lu.se/~anders/IPF2013/ IAU Symposium 297: The Diﬀuse Interstellar Bands 20 - 24 May 2013 Noordwijkerhout, The Netherlands http://iau297.nl/ Brown Dwarfs come of Age 20 - 24 May 2013 Fuerteventura, Canary Islands, Spain no web site yet The Origins of Stellar Clustering - from Fragmenting Clouds to the Build-up of Galaxies 26 May 2013 - 16 June 2013 Aspen, Colorado, USA http://www.mpa-garching.mpg.de/~diederik/aspen2013

57 IAU Symposium 299: Exploring the Formation and Evolution of Planetary Systems 2 - 7 June 2013 Victoria, BC, Canada http://www.iaus299.org Massive Stars: From alpha to Omega 10 - 14 June 2013 Rhodes, Greece http://a2omega.astro.noa.gr Lin-Shu Symposium: Celebrating the 50th Anniversary of the Density-Wave Theory 24 - 28 June 2013 Beijing, China no web site yet Protostars and Planets VI 15 - 20 July 2013 Heidelberg, Germany http://www.ppvi.org Dust Growth in Star & Planet Formation 2013 22 - 25 July 2013 MPIA, Heidelberg, Germany no web site yet 2013 Sagan Summer Workshop: Imaging Planets and Disks 29 July - 2 August 2013 Pasadena, CA, USA http://nexsci.caltech.edu/workshop/2013/ IAUS 302 - Magnetic Fields Throughout Stellar Evolution 26 - 30 August 2013 Biarritz, France http://iaus302.sciencesconf.org Meteoroids 2013. An International Conference on Minor Bodies in the Solar System 26 - 30 August 2013 Dep. of Physics, A.M. University, Poznan, Poland http://www.astro.amu.edu.pl/Meteoroids2013/index.php Exoplanets and Brown Dwarfs 2 - 5 September 2013 de Havilland, University of Hertfordshire, Hatﬁeld, Nr. London, UK no web site yet The Life Cycle of Dust in the Universe: Observations, Theory, and Laboratory Experiments 18 - 22 November 2013 Taipei, Taiwan http://events.asiaa.sinica.edu.tw/meeting/20131118/ The 18th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun 9 - 13 June 2014 Flagstaﬀ, Arizona, USA http://www2.lowell.edu/workshops/coolstars18/ Living Together: Planets, Stellar Binaries and Stars with Planets 8 - 12 September 2014 Litomysl Castle, Litomysl, Czech Republic no web site yet Towards Other Earths II. The Star-Planet Connection 15 - 19 September 2014 Portugal http://www.astro.up.pt/toe2014

Other meetings: http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

58 New Books

The Formation and Early Evolution of Stars Norbert S. Schulz

This is the second, revised edition of the book “From Dust to Stars” (presented in SFNL #154) that appeared in 2005. The major and rapid progress in our field has required significant updates to the text. Three chapters, on multiplicity in young stellar objects, on massive star formation, and on exoplanets and planet formation, have been added, resulting in this new, expanded book. References are given to the key literature throughout the text, and a reference list at the end of the book contains more than 1300 entries, the majority of which date to the past 10 years. Although not written specifically as a text book for a course on star formation, this comprehensive and easily accessible text will appeal to both undergraduate and graduate students, as well as researchers who wish to get an overview of the current state of star formation studies. The following lists the chapters and subsections of the book: 1 About the Book 2 Historical Background 2.1 And There Was Light? 2.2 The Quest to Understand the Formation of Stars 2.3 Observing Stellar Formation 3 Studies of Interstellar Matter 3.1 The Interstellar Medium 3.2 Interstellar Gas 3.3 Column Densities in the ISM 3.4 Interstellar Dust 3.5 The ISM in other Galaxies 4 Molecular Clouds and Cores 4.1 Global Cloud Properties 4.2 Clud Dynamics 4.3 Dynamic Properties of Cores

59 5. Concepts of Stellar Collapse 5.1 Classical Collapse Concepts 5.2 Stability Considerations 5.3 Collapse of Rotating and Magnetized Clouds 5.4 Cores, Disks and Outﬂows: the Full Solution? 6 Evolution of Young Stellar Objects 6.1 Protostellar Evolution 6.2 Evolution in the HR-Diagram 6.3 PMS Classiﬁcations 7 Multiplicity in Star Formation 7.1 Observational Account 7.2 PMS Properties of Binaries 7.3 Formation of Binaries 7.4 Mass Transfer in Compact Binaries 8 Accretion Phenomena and Magnetic Activity in YSOs 8.1 Accretion Disks 8.2 Stellar Rotation in YSOs 8.3 Magnetic Activity in PMS Stars 9 Massive Star Formation 9.1 Properties of Young Massive Stars 9.2 Distribution of Massive Stars 9.3 Observations of Eary Stages 9.4 Formation Concepts 9.5 Multiplicity 9.6 The First Stars 10 High-energy Signatures in YSOs 10.1 The X-ray Account of YSOs 10.2 X-rays from Protostars 10.3 X-ray Spectra of PMS Stars 10.4 γ-Radiation from YSOSs 11 Star-Forming Regions 11.1 Embedded Stellar Clusters 11.2 Well-studied Star-forming Regions 11.3 Formation on Large Scales 12 Proto-solar Systems and the Sun 12.1 Protoplanetary Disks 12.2 The Making of the Sun 13 Protoplanets and Exoplanets 13.1 The Search for Exoplanets 13.2 The Search for Protoplanets 13.3 Planet Formation Appendix A Gas Dynamics Appendix B Magnetic Fields and Plasmas Appendix C Radiative Interactions with Matter Appendix D Spectroscopy

Springer 2012, ISBN 978-3-642-23925-0 515 pages, hardcover US$119.00 Available from http://www.springer.com/astronomy/book/978-3-642-23925-0

60 Short Announcements

American Chemical Society (ACS) Creates New Astrochemistry Subdivision

At the national ACS meeting in Philadelphia, the ACS-PHYS division established a new Astrochemistry Subdivision. Astrochemistry is the study of the abundances and chemical reactions of atoms, molecules, and ions and how they interact with radiation in both gas and condensed phases in Solar Systems and in the Interstellar Medium. The new Subdivision provides an interdisciplinary ”home” for individuals interested in this growing research area. We would like to invite you and the undergraduate students, graduate students, and postdoctoral fellows in your group to join the ACS Astrochemistry Subdivision to connect to an exciting research endeavor and to further promote the Astrochemistry Subdivision at (international) meetings, in your university, and in your department. Additional information on joining the Subdivision may be found at: http://www.chem.hawaii.edu/Bil301/ACSAstrochemistry.html An inaugural Astrochemistry Symposium will be held at the Fall ACS National Meeting in Indianapolis, IN, September 8-12, 2013. Please also email us ([email protected], [email protected],[email protected]) suggestions for forthcoming ACS Astrochemistry Symposia and nominations for officers for the Astrochemistry subdivision. We would also like to thank those of you who supported the establishment of the Astrochemistry Subdivision! We hope that the new Subdivision will effectively serve this thriving scientific community. Best regards, Ralf Kaiser (Chair), Arthur Suits (Chair-Elect), Martin Head-Gordon (Vice-Chair)

50 Years of Brown Dwarfs: from Theoretical Prediction to Astrophysical Studies

Talks and posters of this Ringberg conference (Oct. 2012) are now online: http://www.mpia.de/homes/joergens/ringberg2012_proc.html

The talks and posters presented at this international conference at Ringberg Castle on Oct 21-24, 2012 summarize the historical aspects concerning the 50th anniversary of the theoretical prediction of brown dwarfs (S. Kumar) and of first brown dwarf discoveries (e.g., B. Oppenheimer, R. Rebolo, G. Basri). Furthermore, various aspects of brown dwarf research were presented, including the physics of brown dwarfs (I. Baraffe) and the properties of young (e.g., M. Zapatero-Osorio, K. Luhman) and ultracool L, T, and Y dwarfs (M. Cushing). A focus of the workshop was the exploration of the origin of brown dwarfs in context with brown dwarf binaries. Presentations on observational binary studies (RV and direct imaging, e.g., B. Biller, C. Blake, and T. Dupuy) met with theories in the field of brown dwarf formation (e.g., S. Basu, M. Bate, P. Clark, S. Inutsuka) in a very fruitful atmosphere. Most of the talks and posters are now online. SOC: Viki Joergens, Thomas Henning, Isabelle Baraffe, Gibor Basri, Wolfgang Brandner, Adam Burgasser, Cathie Clarke, Ralf Klessen, Keivan Stassun