249 — 12 September 2013 Editor: Bo Reipurth ([email protected]) List of Contents

249 — 12 September 2013 Editor: Bo Reipurth (Reipurth@Ifa.Hawaii.Edu) List of Contents

THE STAR FORMATION NEWSLETTER An electronic publication dedicated to early stellar/planetary evolution and molecular clouds No. 249 — 12 September 2013 Editor: Bo Reipurth ([email protected]) List of Contents

The Star Formation Newsletter My Favorite Object ...... 3 Perspective ...... 10 Editor: Bo Reipurth [email protected] Abstracts of Newly Accepted Papers ...... 14

Technical Editor: Eli Bressert Dissertation Abstracts ...... 49 [email protected] New Jobs ...... 51 Technical Assistant: Hsi-Wei Yen Meetings ...... 52 [email protected] Other Meetings ...... 53

Editorial Board Short Announcements ...... 55

Joao Alves Alan Boss Jerome Bouvier Lee Hartmann Cover Picture Thomas Henning Paul Ho The front cover shows the Orion Nebula Cluster us- Jes Jorgensen ing images obtained with the VISTA infrared sur- Charles J. Lada vey telescope at the ESO Paranal Observatory in Thijs Kouwenhoven Chile. Three images, each with 10 minute expo- Michael R. Meyer sure, were taken through Z, J, and Ks ﬁlters and Ralph Pudritz combined. The ﬁeld is about one degree in width. Luis Felipe Rodr´ıguez Ewine van Dishoeck Image courtesy ESO/J. Emerson/VISTA. Acknowl- Hans Zinnecker edgment: Cambridge Astronomical Survey Unit.

The Star Formation Newsletter is a vehicle for fast distribution of information of interest for astronomers working on star and planet formation and molecular clouds. You can submit material for the following sections: Abstracts of recently Submitting your abstracts accepted papers (only for papers sent to refereed journals), Abstracts of recently accepted major re- Latex macros for submitting abstracts views (not standard conference contributions), Dis- and dissertation abstracts (by e-mail to sertation Abstracts (presenting abstracts of new [email protected]) are appended to Ph.D dissertations), Meetings (announcing meet- each Call for Abstracts. You can also ings broadly of interest to the star and planet for- submit via the Newsletter web inter- mation and early solar system community), New face at http://www2.ifa.hawaii.edu/star- Jobs (advertising jobs speciﬁcally aimed towards formation/index.cfm persons within the areas of the Newsletter), and Short Announcements (where you can inform or re- quest information from the community). Addition- ally, the Newsletter brings short overview articles on objects of special interest, physical processes or theoretical results, the early solar system, as well as occasional interviews. Newsletter Archive www.ifa.hawaii.edu/users/reipurth/newsletter.htm

2 My Favorite Object LL Ori Will Henney

Figure 1: The hyperbolic arcs of the LL objects are produced when a mildly supersonic flow of ionized gas (left) shocks against an obstacle. The obstacle (right) is most likely a supersonic outflow from the enclosed T Tauri star: The classical T Tauri star LL Orionis is the prototype possibly the flow from a proplyd ionization front (above), of the class of LL objects, which show spectacular arcs of or a stellar wind (below). circumstellar emission (see Figs. 1 and 2). The arc around LL Ori was first remarked upon by Gull & Sofia (1979), and six further similar objects were identified by (Bally tion of table) and shocked shells (lower section). & Reipurth 2001), who denoted them LL 1 to LL 7, with Convex Ionization Fronts When an ionization front wraps LL 1 corresponding to LL Ori. They have been intensely around a dense obstacle, then, so long as the confining studied via optical emission line imaging with HST (Bally pressure in the H II region is not too large, it will form et al. 2000; Bally et al. 2006), and more recently with an ionized photoevaporation flow with an approximately high-resolution spectroscopy (Henney et al. 2013). Like D-critical front (e.g., Dyson 1968). The electron den- many other LL objects, LL 1 also harbors a hypersonic sity ne, and therefore the optical emission line bright- jet, HH 888, whose knots are not point-symmetrical about ness, has a sharp peak at the ionization front on a scale the star, but rather show a C-shaped bent morphology, of ≈ (106 cm−3/n) AU (Henney et al. 2005b), superim- curving away from the core of the Orion Nebula. posed on a more gradual decline on a scale of roughly The vast majority of the LL objects detected to date (over 1/10 of the radius of curvature of the front (Bertoldi 1989). 20) are in the Orion Nebula, although a very similar ob- Even within a single nebula, such as Orion, the same ba- ject has recently been found in the Carina Nebula (Smith sic phenomenon explains structures ranging in size from et al. 2010). They provide a fascinating window into the tens of AU (the smallest proplyds) up to tens of thousands complex outflow phenomena (both jets and uncollimated of AU (large scale structures such as the Bright Bar and winds) associated with pre-main sequence stars in dense the champagne flow away from the main ionization front). clusters. At the same time, they can function as “test par- Numerical simulations show that such flows arise natu- ticles”, allowing the internal dynamics of the H II region rally during the evolution of an H II region inside a tur- to be probed. Figure 3 situates the LL objects within the bulent molecular cloud (Mellema et al. 2006; Gritschneder context of the Orion Nebula’s internal flows. et al. 2010; Arthur et al. 2011; Ercolano et al. 2012). It is the largest scale photoevaporation flows of this nature (Zuckerman 1973; O’Dell et al. 1993; Henney et al. 2005a; Taxonomy of bright arcs in H II regions Garc´ıa-D´ıaz et al. 2008) that are believed to provide the external wind that shocks to form the hyperbolic arcs seen Several different phenomena can give rise to sharply de- in the LL objects, whereas the smallest scale photoevap- fined, curved features inside H II regions, which sometimes oration flows from protoplanetary disks (Laques & Vidal leads to confusion in the literature over the classification 1979; O’Dell et al. 1993; Johnstone et al. 1998; Henney & of particular objects. In Table 1, I present a general tax- O’Dell 1999; Ricci et al. 2008) are one candidate for the onomy of such phenomena, which can be broadly divided internal wind (see Fig. 1). into two categories: convex ionization fronts (upper sec-

3 Figure 2: Left panel shows the location of LL Ori in the south-west of the Orion Nebula. The color image is a combination of HST WFPC2 observations (O’Dell & Wong 1996) in three filters: [N II] λ6584 (red), Hα λ6563 (green), and [O III] λ5007 (blue). With the brightness adjusted to bring out LL Ori and other features in the outer nebula, the inner regions of the nebula are saturated and appear white. In this saturated area I have superimposed a negative image of the same Hα mosaic, but with maximum brightness set at 15 times that of the color image. Right panel shows an expanded view of LL Ori itself, indicating the principal components. The hyperbolic bow shock is due to the wind-wind collision between a stellar outflow from the T Tau star and the champagne flow of ionized gas from the core of the Orion Nebula. The colored arrows superimposed on the jet knots show the radial velocity (red or blueshifted) and proper motions (Henney et al. 2013). Jet knot velocities range from 60 to 120 km s−1, whereas velocities in the wings of the bow are only ∼ 20 km s−1.

Shocked Shells Whenever a supersonic outflow impinges motions and small radial velocities. The second category on a quiescent or slow-moving medium, or two supersonic can be sub-divided into the classical proplyd bow shocks flows collide, then a double-shock structure will form (Si- (Bally et al. 1998; Garc´ıa-Arredondo et al. 2001; Smith mon & Axford 1966; Avedisova 1971; Dyson & de Vries et al. 2005; Robberto et al. 2005) and the hyperbolic LL 1972). If either of the shocks is strongly radiative, then it arcs (see Fig. 3 and Tab. 1). The principal difference be- will be visible as a bright emission arc. It turns out that, tween the two sub-groups is that in the proplyd case the for shock velocities of 20–60 km s−1 and densities higher outer bow shock is not directly observed since it is in the than a few hundred cm−3, the cooling length behind the fast stellar wind from the O star and is non-radiative. In- shock is very short, so that the shock can be considered stead, the observed emission arcs are due to the termina- isothermal for many purposes. tion shock in the mildly supersonic (M ≃ 3) flow from Such shocked shells can be divided into those driven by the proplyd ionization front. In the case of the hyperbolic non-steady jets, which show high proper motions in the LL arcs, on the other hand, which are generally found plane of the sky and highly blueshifted or redshifted ra- much farther out in the nebula, it is the outer bow shock dial velocities (e.g., Bally et al. 2006; Henney et al. 2007; that dominates the emission from the shell. This is the O’Dell & Henney 2008), and those due to the head-on reason that the LL arcs are much more open than the interaction of two winds or streams, which are approxi- arcs in front of the close-in proplyds, which tend to be mately in a steady state, showing no detectable proper more semi-circular in form. For a low Mach number ex-

4 Figure 3: Schematic diagram of wind-wind interactions in the Orion Nebula (a simpler version of this diagram first appeared in O’Dell et al. 2009). The observer is located towards the bottom of the page. Green/black indicates neutral/molecular gas (T = 50–1000 K, n = 104–106 cm−3); red indicates warm photoionized gas (T ≈ 104 K, n = 102–104 cm−3); blue indicates stellar wind material (T ≥ 106 K, n ∼ 1 cm−3). Arrows show supersonic and transonic gas flows, radiative bow shocks are shown by thick dark red lines, and non-radiative bow shocks by blue dot-dashed lines, while blue dotted lines show contact discontinuities. Note that the diagram is not to scale and that the ionization front and density structure are in reality far more irregular than is portrayed. Wind-wind bow shocks occur in two different regions of the nebula: an inner interaction zone (left-hand inset box) where the external bow shock is in the hypersonic O star wind (V ∼ 1000 km s−1) and outer interaction zones (right-hand inset box) where the external bow shock is in a mildly supersonic photoevaporated champagne flow (V ∼ 20 km s−1). The external bow shock is non-radiative in the inner interaction zone, but radiative in the outer interaction zones. The internal termination shock is radiative when the internal wind is a proplyd photoevaporation flow, and may be non-radiative or radiative otherwise, depending on the wind velocity and density.

5 Table 1: Varieties of arc-like emission features in H II regions. Phenomenon Hα image Physical Origin Observational Signatures Size, AU Elephant Both the clumpy structure of the Low proper motions and 100 to 30,000 trunks, surrounding molecular cloud and radial velocities. Sharp edge pillars, instabilities in the ionization front on inside of arc. Presence of globules, itself contribute to a rich variety of low ionization species such as bright rims, convex, D-critical ionization fronts, [O I], [S II] and [N II]. bars with associated ionized Ionization stratiﬁcation. photoevaporation ﬂows.

Proplyd Similar to above, but with a more Low proper motions and 20 to 500 crescents complicated internal structure, radial velocities. Suppression involving a photodissociated ﬂow of low-critical-density lines. from an embedded protoplanetary Larger linewidths disk. (> 50 km s−1) for high ionization lines such as [O III]. Central disk absorption. Herbig– Working surface produced by a High proper motions 1000 to 10,000 Haro bow hypersonic collimated jet from a perpendicular to arc, and high shocks protostar or T Tauri star. May be radial velocities due to interaction with ambient (50 –100 km s−1). Sharp edge nebular gas or due to internal on outside of arc. shocks in a variable-velocity jet.

Bent jets The jet beam may be deﬂected High proper motions parallel 3000 to 30,000 away from the center of the nebula to arc, and high radial due to ambient density gradients, velocities (≈ 100 km s−1). ram pressure from a side wind, or Knotty structure. the rocket eﬀect on a photoevaporating neutral core.

Proplyd Due to the interaction of the ionized Low proper motions and 500 to 2000 wind-wind photoevaporation ﬂow radial velocities. Usually high −1 bow shocks (30–40 km s ) from a proplyd ionization. Relatively closed crescent with the high-speed bow shape. Emission conﬁned (> 1000 km s−1) stellar wind from to ±45 ◦ from axis. an O star.

LL bow Due to the interaction of a Low proper motions and 1000 to 10,000 −1 shocks relatively low speed (≃ 20 km s ) moderate radial velocities −1 champagne ﬂow of ionized gas (≈ 15 km s ). Relatively within the nebula and an outﬂow broad shell. More open bow from a T Tauri star, which may also shape. Emission extends into be a proplyd. conical wings.

6 excitation. Such is the case for LL 2 (left panel of Fig. 4), where a narrow zone of [O III] emission is seen at the leading edge of the fast-moving jet knots.

The jet–bow shock relationship in LL objects

It has long been surmised that the hyperbolic bow shocks of the LL objects might be causally related to their collimated jets (e.g., Masciadri & Raga 2001). However, our detailed study of the LL 1 and LL 2 systems (Henney et al. 2013) casts serious doubts on the idea that the hyperbolic bow shocks might be due to jet interactions. First, the kinematic signature of the jets and the bow shocks do not match. If the bow shock were related to the jet, then one Figure 5: Predicted bow shock shell thickness (in arcsec) would expect the jet’s anti-symmetry (red on one side, as a function of the Mach number of the incident flow, blue on the other) to be reflected in the kinematics of the assuming a density and temperature in the equilibrium bow shock, but this is not observed. Instead, the bow shell of 3500 cm−3 and 8700 K, respectively. shock kinematics is very symmetrical in LL Ori, with blue shifts being seen on both sides of the axis. In LL 2 the bow shock does show a velocity gradient across the axis, ternal flow, there is a substantial opening angle (of order −1 −1 but it is opposite in sense to that seen in the jet. That the Mach angle: sin M ) between the outer bow shock is, the shell is more redshifted on the side where the jet and the momentum balance surface (e.g., Whitham 1974; is blueshifted. Second, a three-dimensional de-projection van Dyke 1982). Therfore, the observed LL shell is much of the HH 888 and HH 505 jet knot positions indicates more open than would be predicted by calculations in the that they nearly all lie “outside” their respective hyper- hypersonic limit, such as Cantóet al. (1996). bolic bow shocks and that the appearance of interaction is However, things are not so simple since many of the LL ob- largely a projection effect. Third, at least one LL object jects also harbor proplyds, as can be seen in the right panel (261-3018) has a jet that is aligned nearly parallel to the of Figure 4. In most cases, only the broad outer bow shock symmetry axis of the bow shock. shell is seen, but in some cases (e.g., 072-134 in the figure) On the other hand, what appears at first glance to be part a sharper inner shell associated with the proplyd termina- of the hyperbolic bow shock is sometimes indeed due to jet tion shock is also evident. interactions. This seems to be the case for the apparent Shock Emission versus Shell Emission In general, the lower bow shock wing in LL 2 (see left panel of Fig. 4), total emission from a photoionized shock will have con- which is not part of the stellar bow shock at all, but instead tributions both from the cooling zone directly behind the is more similar to the bent jets such as HH 878 shown in shock (which may be high-temperature and over-ionized), Table 1. The telltale sign in this case is the fact that the and also from a compressed shell of gas that has returned shocked shell is much sharper and thinner on the south- to approximate photoionization and thermal equilibrium ern side, indicative of a high Mach number shock. This (see Henney 2002 for discussion in the context of proplyd interpretation is confirmed by proper motion and radial bow shocks). In the case of LL 1, it is the equilibrium shell velocity studies (Henney et al. 2013): the true stellar bow that dominates the emission of recombination lines such shock stops about 3000 AU south of the central star. The as Hα, whereas for collisionally excited lines (particularly same may be true of LL 6 (bottom-most image in Table 1), [O III]), there is evidence for a significant shock contribu- where the western apparent wing of the stellar bow shock tion (Henney et al. 2013). Figure 5 shows the predicted is much thinner than the eastern one and may instead be thickness of the post-shock cooling zone and equilibrium a HH bow driven by the central star’s jet. Some of the shell as a function of Mach number, given the measured complicated morphologies that can arise when a stellar jet shell density. Comparison with the observed thickness in- breaks out into an H II region have been illustrated by nu- dicates a Mach number of 1.5–2 for the external wind. merical simulations (e.g., Raga & Reipurth 2004; Kajdic Note that the second solution at M ≈ 8 can be discarded & Raga 2007). since it is inconsistent with the observed kinematics. For LL objects at greater distances from the center of the nebula, photoionization equilibrium predicts very weak [O III] emission, so it is easier to see the direct effects of shock

7 (a) (b)

Figure 4: Other LL objects in Orion. (a) The T Tauri star IX Ori, located in the far west of the Orion Nebula, with its associated bow shock LL 2 and bipolar jets HH 505 (adapted from Fig. 11 of Henney et al. 2013). Regions of enhanced [O III] emission at the leading edge of jet knots are marked. (b) A grouping of five small stellar and/or proplyd bow shocks in the north west of the Orion Nebula. The objects are labeled with the coordinate-based designations (O’Dell & Wen 1994) of their central star. The color image shows the same WFPC2 filters as in Fig. 2 but with different intensity scalings. Negative grayscale insets show higher resolution ACS Hα+[N II] images (Bally et al. 2006) of the two faintest bow shocks.

Further work and open issues any proplyd emission is masked by the high luminosity of the central T Tauri star, but it may be that a different As is often the case, each discovery brings with it a host of mechanism provides the isotropic inner wind in these ob- new questions, and many mysteries remain about LL Ori, jects. It is suggestive that the most prominent LL objects its bow shock and jets, and the similar objects found in have relatively high luminosity central stars, Lbol ≃ 3– the Orion Nebula and beyond. Here are some ongoing 10 L⊙, as compared with the luminosity function of the projects and unresolved questions: Orion Nebula Cluster, which peaks in the range 0.1–1 L⊙, General catalog of stationary bow shocks in Orion A sys- (Da Rio et al. 2012). No such correlation is found (or ex- tematic effort is currently underway to catalog the sizes, pected) between stellar luminosity and photoevaporation shapes, and stagnation pressures of all known stellar and flow strength in the case of the proplyds. proplyd bow shocks in the Orion Nebula (currently num- Nature of the double shell objects? In LL Ori itself (Fig. 2) bering more than 50) using a uniform methodology. These and at least three other LL objects (LL 5, 072-134, see will be cross-correlated with the parameters of the en- Fig. 4, and 266-558, see Fig. 6), the nose of the bow shock closed T Tauri stars (luminosities, masses, and ages, e.g., shell shows internal structure, with its brightness peak- Da Rio et al. 2010) and compared with hydrodynamic ing at the inside edge. This is perhaps evidence that we models, so as to provide new insights into the LL Ori phe- are seeing two shells: one associated with the outer bow nomenon. shock and one with the inner termination shock. But if Do all LL objects contain proplyds? Although many of that were the case, it is a little surprising that we can the smaller LL arcs are associated with known proplyds, distinguish the emission from the two. In a steady state, most of the larger and brighter ones show no direct evi- the pressure in the two shells would be equal, and if they dence for a photoevaporating disk. This may be because were both in photoionization equilibrium then the temperature, density, and therefore line emissivity would also

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9 member of the class of planets known as ‘hot Jupiters’, 51 Pegasi b must have initially formed at large radial distance Perspective from its host star, and reached its present orbit by disk migration (Lin et al. 1996). Alternatively, it has been Solar System’s Disordered scattered inward during dynamical instability, and was Beginnings subsequently circularized by tides (Rasio & Ford 1996). by David Nesvorný Hydrodynamical simulations of pairs of planets show that disk migration of Jupiter and Saturn can roughly be divided into three stages (Masset & Snellgrove 2001). In the first stage, Jupiter forms, opens a gap, and migrates inward with gas. In the second stage, Saturn forms and migrates inwards as well, but faster than Jupiter because of its smaller mass, and eventually catches up with Jupiter. The two planets should have migrated outward during the final stage, because of an increased mass flow through the overlapping gaps of the two planets, and because the outer torques on Jupiter, which would otherwise dominate the overall evolution, were diminished by the presence of Sat- urn’s gap. This kind of early evolution of Jupiter and Saturn probably prevented formation of hot Jupiter in the Solar Sys- tem. It can help to explain the small mass of Mars and The circular, evenly-spaced orbits of planets were thought the asteroid belt, because much of solid material at 1.5-4 to be relics of an uneventful evolutionary history of the AU would have been removed by Jupiter’s excursion into Solar System. Each planet seemed to have been assem- the inner part of the Solar System (Walsh et al. 2011). bled very near its present orbit and maintained dynamical These results also suggest that Jupiter and Saturn emerg- harmony with its neighbors. This perspective has recently ing from the dispersing protoplanetary nebula should have changed and we now view the present Solar System as a had very different orbits from their present ones. result of complex dynamical evolution where radial migra- Specifically, the convergent radial migration during the tion of planets, instabilities, and planet-planet scattering second stage described above should have led to a two- played important parts. body resonance, where the orbital periods of the two plan- The first Solar System solids condensed 4.568 Gyr ago ets were in a ratio of small integers. The 3:2 resonance (pe- (Kleine et al. 2009). This is considered as time zero in the riod ratio 1.5) is strongly favored from the hydrodynamical Solar System history. Jupiter and Saturn have significant simulations (Masset & Snellgrove 2001). This is because gas envelopes and must have formed within the lifetime of the first strong resonance encountered by the converging the protoplanetary gas disk, most likely within 2-10 Myr orbits, 2:1 (period ratio 2), can easily be skipped for the of time zero (Williams & Cieza 2011). migration rates computed for standard disk parameters. As the growth of Jupiter was reaching completion, the Other resonances are either weak or unreachable. gravitational torques in the immediate neighborhood of This raises a question: If Jupiter and Saturn indeed had its orbit opened radial gap in the gas disk. Subsequently, resonant orbits toward the end of the lifetime of the gas as only little gas can flow through the gap, Jupiter found nebula, how is it possible that their orbital period ratio itself locked into the disk evolution. A viscous accretion is 2.49 today? A process known as planetesimal driven disk is expected to radially spread such that most mass migration (Fernandez & Ip 1984), or PDM for short, was is carried inward, and most angular momentum escapes thought to do the trick. The PDM arises when planets outward (Lynden-Bell & Pringle 1974). In the inner part have close encounters with asteroid- or comet-like bodies of the disk, where Jupiter formed, solitary planets are ex- commonly designated as planetesimals, and scatter them pected to be carried inward with the infalling gas. around. The credibility of these expectations were boosted by the This works as follows. In all likelihood, the formation discovery of the first planet around a main-sequence star of giant planets was not an ideally efficient process with other than the Sun, 51 Pegasi (Mayor & Queloz 1995). a significant fraction of solids left behind in dust, small Planet 51 Pegasi b is at least half as massive as Jupiter, debris, and an outer belt of icy planetesimals probably has the orbital period of 4.2 days, and receives extreme ir- extending all the way to the present location of the Kuiper radiation from its host star. Now recognized as a postcard

10 belt. mutual 2:1 resonance. The resonant passage kicks these If a planetesimal evolves from the disk into a Neptune- planets typically enough to lead to dynamical instability crossing orbit, it will have close encounters with Neptune, and transition, where Uranus and Neptune start having and will be scattered in or out. Neptune’s mass is too close encounters with Saturn (and sometimes with Jupiter small, however, to eject bodies from the Solar System. as well), are scattered out, stabilize in the outer planetes- Thus, a planetesimal scattered out will come back to Nep- imal disk, and end up slowly migrating by PDM to 20 tune, and will be, sooner or later, scattered in. It will and 30 AU, respectively. This theory is now known as the then perform a similar dance with Uranus and Saturn. Nice model after a city on the French Riviera where it was Jupiter, on the other hand, has the surface gravity that is conceived. sufficiently large to sling shot bodies all the way from the The dynamical transition in the Nice model has the po- Solar System. tential to explain many puzzling properties of the Solar So, overall, there will exist a flux of planetesimals from System. Perhaps its most important success is related beyond the orbit of Neptune to Jupiter, and out into in- to the Late Heavy Bombardment (LHB) of the Moon, terstellar space. The conservation of orbital energy and an epoch some 3.7-4.2 Gyr ago when most lunar basins momentum then dictates that Neptune, Uranus and Sat- formed. The Nice model can provide a natural explana- urn must move out, while Jupiter moves in. tion for the LHB, because changing planetary orbits lead to a release of numerous impactors from previously sta- The outward migration of Neptune is key to understand- ble reservoirs between Mars and Jupiter, and from being many observed properties of the Kuiper belt, such as yond Neptune. The total mass accreted by the Moon, its dynamical excitation, resonant orbits of Pluto and its impact flux profile, and other LHB signatures obtained numerous companions in the 3:2 resonance with Neptune by modeling the aftermath of planetary instability in the (Malhotra 1993), and identified correlations of orbits with Nice model are broadly consistent with available LHB con- physical size, color and binarity. straints (Gomes et al. 2005, Bottke et al. 2012). The PDM can also help to resolve the problem mentioned above, because the orbital spacing of Jupiter and Saturn is expected to increase as a result of PDM. Their period ratio could therefore plausibly increase from 1.5 to 2.49 as a result of PDM alone. The possibility that the outer Solar System passed through a dynamical instability was suggested by Thommes et al. (1999), and was then placed on firmer grounds by Tsiga- nis et al. (2005). In its original formulation, motivated by the inability of the existing models to form Uranus and Neptune beyond the orbit of Saturn, Uranus and Neptune were assumed to have formed between Jupiter and Saturn, from where the ice giants were scattered outward and sta- bilized by dynamical friction from an outer planetesimal disk. This scenario requires a very massive planetesimal disk, because the dynamical instability arising from such initial conditions tends to be violent. Put simply, the planetesimal disk acts as a glue, the more massive it is, the more sticky it is. Even though the formation of Uranus and Neptune is still Figure 1: Planetary orbits and disk particle positions in poorly understood, latter studies of dynamical instability the instability model, where the Solar System was assumed to have five giant planets initially. The panels show four typically place Uranus and Neptune outside the orbit of Saturn. The main advantage of this more natural setup is different times from a reference simulation. In this run, the giant planets were initially on nearly-circular, co-planar the inferred low and probably more plausible mass of the orbits with semi-major axes between 5.5 and 22.8 AU. The outer planetesimal disk, and a better ability of models to match the present planetary orbits. initial disk contained 20 Earth masses between 24 and 30 AU. (a) Just prior to the LHB, (b) During the LHB, (c) In Tsiganis et al., the instability is triggered when Jupiter Immediately after the onset of the LHB, and (d) 50 Myr and Saturn, migrating due to the PDM, encounter the later with nearly final planetary orbits.

11 The association with the LHB would imply that the onset Second, the smooth migration of Jupiter and Saturn due of planetary instability was delayed, and happened some to the PDM would trigger a specific type of resonances, 400 Myr after time zero. This would produce a spike of called apsidal resonances, which can easily channel the impacts on the Moon and terrestrial planets with the im- orbital momentum from Jupiter to the terrestrial planets. pactor flux increasing by an approximate factor of 10 from The undesired effect of this process, potentially leading the pre-LHB level (Morbidelli et al. 2012). This is clearly to crossing orbits and mutual collisions of the terrestrial a very different profile than the one expected from a purely planets, could be avoided only if Jupiter’s orbit was very PDM scenario, where the population of impactors in the nearly circular, and was dynamically excited later (hard to inner Solar System should monotonously decay with time. understand how), or if the region where apsidal resonances Additional difficulties for a purely PDM scenario arise due occur was crossed at a swift pace not expected from a slow to smooth, or nearly smooth evolution of Jupiter’s and process such as the PDM. Saturn’s orbits due to encounters with small planetesi- Planetary instability offers an elegant solution to these mals. First, the cumulative effect of such encounters is problems, because encounters of Jupiter with Uranus or to reduce the orbital eccentricity of Jupiter such that the Neptune can excite its orbital eccentricity to just the right orbit would end up being very nearly circular. Yet, the value, and because the kick produced by these encounters present eccentricity of Jupiter’s orbit is substantial (4.4% can change Jupiter’s semimajor axis in just the right way mean). to avoid the apsidal resonances with the terrestrial planets. The version of the Nice model featuring Jupiter’s encounters with one of the ice giants has become known as the ‘jumping-Jupiter’ model (Morbidelli et al. 2010). When I became interested in this topic a few years ago the dynamical processes discussed above had been previously studied using various approximations of early Solar System evolution. Typically, the concepts were illustrated in one or a few idealized cases that were often different when different constraints were considered. I thought it would be useful to investigate things more systematically by running a statistically large set of instability calculations, and by considering all available constraints at the same time. This work yielded an unexpected result. Over a period of two years, Alessandro Morbidelli and I performed and analyzed nearly 104 numerical integrations of planetary instability, starting from hundreds of different initial configurations of planets that were obtained from previous hydrodynamical and N-body calculations. For Figure 2: Orbit histories of the giant planets taken from the reasons explained above, the configurations with the simulations of Nesvorný& Morbidelli (2012). Five planets 3:2 Jupiter-Saturn resonance were given special attention. were started in the (3:2,4:3,2:1,3:2) resonant chain, and the Our integrations included the effects of the outer planetes- planetesimal disk mass was set to 20 Earth masses. Up- imal disk. We experimented with different disk masses, per panel: The semimajor axes (solid lines), and perihe- density profiles, instability triggers, etc. lion and aphelion distances (dashed lines) of each planet’s orbit. The horizontal dashed lines show the semimajor We considered cases with four, five and six initial planets, axes of planets in the present Solar System. The final where the additional planets were placed onto resonant orbits are a good match to those in the present Solar Sys- orbits between Saturn and the inner ice giant, or beyond tem. Lower panel: The orbital period ratio PSat/PJup. the orbit of the outer ice giant. As we describe below, The dashed line shows PSat/PJup = 2.49 corresponding including extra planets helps to boost the success rate of to the present orbits of Jupiter and Saturn. The shaded the instability simulations, because planets can readily be area approximately denotes the zone where the secular ejected into interstellar space during the instability. resonances with the terrestrial planets occur. These reso- Several criteria were defined to measure the overall success nances were not activated, and the terrestrial planets were of our simulations. First of all, the final planetary system left unharmed, because the period ratio ‘jumped’ over the must have four giant planets (criterion A) with orbits that shaded area as Jupiter and Saturn scattered off of the resemble the present ones (criterion B). Note that A means ejected ice giant. that one and two planets must be ejected in the five- and

12 six-planet planet cases, respectively, while all four plan- (estimated mass of lunar impactors, impact profile, etc.). ets need to survive in the four-planet case. As for B, we Unfortunately, however, these constraints are not specific claimed success if the final semimajor axis of each planet enough to uniquely require dynamical instability in the was within 20% to its present value, and if the final eccen- outer Solar System to explain them. A number of other tricities and inclinations were no larger than 0.11 and 2◦, options exist. respectively. These thresholds were obtained by doubling In addition, it is not clear whether the needed ∼400 Myr the current mean eccentricity of Saturn (eSat =0.054) and ◦ delay between time zero and the onset of the LHB can be mean inclination of Uranus (IUra =1.02 ). Additional cri- obtained with the five-planet models discussed above, be- teria were included to express constraints from the orbital cause with Neptune at ≃23 AU (Figure 2), the outer plan- eccentricity of Jupiter, and from the terrestrial planets etesimal disk would become excited by orbital resonances (Nesvorný2011, Nesvorný& Morbidelli 2012). with Neptune, and planetesimals could start leaking from We found that the dynamical evolution in the four planet it onto Neptune-crossing orbits. This process would trig- case was typically too violent if Jupiter and Saturn start in ger the instability earlier than needed. Possibly, Neptune the 3:2 resonance, leading to ejection of at least one ice gi- did not start at >20 AU, but radially migrated to >20 AU ant from the Solar System. Planet ejection can be avoided before the instability, perhaps by interacting with a cloud if the mass of the outer disk of planetesimals was large, of small debris produced by the collisional grinding in the but we found that a massive disk would lead to excessive outer disk. dynamical damping of Jupiter’s orbital eccentricity, and Speculations such as these will no doubt motivate future to smooth migration that violates constraints from the research. Much has yet to be learned. survival of the terrestrial planets, and the asteroid belt. Better results were obtained when the Solar System was assumed to have five giant planets initially and one ice giant, with mass comparable to that of Uranus or Neptune, was ejected into interstellar space by Jupiter (Figures 1, 2 and 3). The best results were obtained when the ejected planet was placed into the external 3:2 or 4:3 resonance with Saturn and the planetesimal disk mass was set to ≃20 Earth masses. The range of possible outcomes was rather broad in this case, indicating that the present Solar System is neither a typical nor expected result for a given initial state, and occurs, in the best cases, with only a ≃5% probability. Note, however, that our criteria applied pose very strict require- Figure 3: Artists impression of a planet ejected from the ments on the instability calculations. A low probability is early Solar System. Image courtesy of Southwest Research therefore expected, because planetary orbits evolve chaot- Institute. ically during the scattering phase. The case with six giant planets showed interesting dynamics but did not offer significant advantages relative to the five-planet case. References: Bottke, W. F. et al. 2012, Nature, 485, 78 These results must be subjected to further scrutiny. The Fernandez, J. A. & W.-H. Ip 1984, Icarus, 58, 109 low probability of matching various criteria can be seen Gomes, R. et al. 2005, Nature, 435, 466 as worrisome, especially because it is difficult to judge Kleine, T. et al. 2009, Geochimica et Cosmochimica Acta, 73, 5150 whether the probabilities are reasonable or not. After all, Lin, D. N. C. et al. 1996, Nature, 380, 606 Lynden-Bell, D., & Pringle, J. E. 1974, MNRAS, 168, 603 there is just one Solar System, and the statistics is not Malhotra, R. 1993, Nature, 365, 819 useful if the data are limited. For further progress we may Masset, F. & Snellgrove, M. 2001, MNRAS, 320 thus need to obtain insights from extra-solar planetary Mayor, M. & Queloz, D. 1995, Nature, 378, 355 systems similar to our own. This may take a while, how- Morbidelli, A. et al. 2010, AJ, 140, 1391 Morbidelli, A. et al. 2012, EPSL, 355, 144 ever, because exoplanets detected so far do not represent Nesvorný, D. 2011, ApJL, 742, 22 good analogs to the Solar System. Nesvorný, D. & Morbidelli, A. 2012, AJ, 144, 117 Rasio, F. A. & Ford, E. B. 1996, Science, 274, 954 Another important and thus far unresolved issue is related Thommes, E. W. et al. 1999. Nature, 402, 635 to the delayed version of the instability, and its relation- Tsiganis, K. et al. 2005, Nature, 435, 459 ship to the LHB. There is little doubt that the delayed in- Walsh, K. J. et al. 2011, Nature, 475, 206 stability can help to explain the existing LHB constraints Williams, J. P. & Cieza, L. A. 2011, ARAA, 49, 67

13 Abstracts of recently accepted papers

Sub-arcsecond high sensitivity measurements of the DG Tau jet with e-MERLIN Rachael E. Ainsworth1, Tom P. Ray1, Anna M.M. Scaife2, Jane S. Greaves3, and Rob J. Beswick4 1 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland 2 School of Physics & Astronomy, University of Southampton, Higheld, Southampton, SO17 1BJ 3 SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS 4 Jodrell Bank Center for Astrophysics, The University of Manchester, Oxford Rd, Manchester M13 9PL, UK E-mail contact: rainsworth@ at cp.dias.ie We present very high spatial resolution deep radio continuum observations at 5 GHz (6 cm) made with e-MERLIN of the young stars DG Tau A and B. Assuming it is launched very close (∼1 AU) from the star, our results suggest that the DG Tau A outflow initially starts as a poorly focused wind and undergoes significant collimation further along the jet (∼50 AU). We derive jet parameters for DG Tau A and find an initial jet opening angle of 86◦ within 2 AU of the −8 −1 source, a mass-loss rate of 1.5×10 M⊙ yr for the ionised component of the jet, and the total ejection/accretion ratio to range from 0.06–0.3. These results are in line with predictions from MHD jet-launching theories. Accepted by MNRAS Letters http://arxiv.org/pdf/1308.2522

Thermal Instability behind a Shock Wave in HI and Molecular Clouds Takuhiro Aota1, Tsuyoshi Inoue2 and Yuri Aikawa1 1 Department of Earth and Planetary Sciences, Kobe University, Japan 2 Department of Physics and Mathematics, Aoyama Gakuin University, Japan E-mail contact: 098s401s at stu.kobe-u.ac.jp We performed one-dimensional hydrodynamic simulations with detailed cooling, heating and chemical processes to examine the thermal stability of shocked gas in cold neutral medium (CNM) and molecular clouds. We find that both CNM and molecular clouds can be thermally unstable in the cooling layer behind the shock wave. The characteristic wavelength of the thermal instability ranges from 10−5 pc to 0.1 pc in the CNM, and from 10−7 pc to 0.1 pc in the molecular clouds. This coincides with the size of observed tiny scale structures in the CNM and molecular clouds, indicating that the thermal instability in the shocked gas could be a formation mechanism of these tiny structures in the interstellar medium. We have also calculated the e-folding number of the thermal instability to estimate the amplification of the density fluctuation in the shocked gas. Density perturbations in the CNM grow by a factor of exp(5)≃ 150, whereas the perturbations in the molecular clouds grow only by a factor of a few behind a high Mach number shock. The amplification factor is larger at lower densities and higher velocities. Formation of very small-scale structures by thermal instability in shocked gas is more effective in lower densities. Accepted by The Astrophysical Journal http://arxiv.org/pdf/1307.7869

Inclination eﬀects in T Tauri star spectra Immo Appenzeller1 and Claude Bertout2 1 Landessternwarte, K¨onigstuhl 12, D-69117 Heidelberg, Germany 2 Institut d’Astrophysique, 98bis Bd. Arago, 75014 Paris, France E-mail contact: iappenze at lsw.uni-heidelberg.de

14 Context. Because of the presence of rotation and accretion disks, classical T Tauri stars have symmetry planes that are normally inclined relative to the plane of the sky. The inclination angles affect the observed spectral properties of these objects. Aims. We study the influence of the inclination angles on classical T Tauri star spectra in an empirical manner. Methods. Published inclination angles, derived from the stellar photospheric rotation or from spatially resolved circumstellar disk observations, are compared with various observed spectral properties, and correlations are established and investigated. Results. Inclinations derived from the stellar rotation are found to be much less accurate than the published disk inclinations, and no significant correlations between spectral properties and inclinations based on rotation data could be detected. In contrast, significant correlations are found between the disk inclination angles and the apparent velocities observed for the forbidden emission lines and the wind absorption features of permitted lines. These data support the assumption of cone-like polar winds with opening angles smaller than ≈ 45◦. Other spectral features show weaker or no inclination dependence. Using these results, the true (deprojected) flow velocities of the polar winds are derived for the investigated sample of T Tauri stars. Deprojected wind-ejection velocities appear to differ by a factor of two −10 −7 among the stars in our sample, which spans a range of mass-loss rates from 10 M⊙/yr to 3 × 10 M⊙/yr. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1308.3095

A Trend Between Cold Debris Disk Temperature and Stellar Type: Implications for the Formation and Evolution of Wide-Orbit Planets Nicholas P. Ballering1, George H. Rieke1, Kate Y.L. Su1, Edward Montiel1,2 1 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA 2 Department of Physics & Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA E-mail contact: ballerin at email.arizona.edu Cold debris disks trace the limits of planet formation or migration in the outer regions of planetary systems, and thus have the potential to answer many of the outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess spectral energy distributions of 174 cold debris disks around 546 main-sequence stars observed by both Spitzer IRS and MIPS. We found a trend between the temperature of the inner edges of cold debris disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g. non-water ice lines) in setting the dimensions of cold debris disks. Also, we found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or it may result from planet formation that halts at an orbital radius limited by the eﬃciency of core accretion. Accepted by ApJ http://arxiv.org/pdf/1308.2223

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M) A. Belloche1, H. S. P. Müller1,2, K. M. Menten1, P. Schilke1,2 and C. Comito1 1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 2 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany E-mail contact: belloche at mpifr-bonn.mpg.de Context. The discovery of amino acids in meteorites fallen to Earth and the detection of glycine, the simplest of them, in samples returned from a comet to Earth strongly suggest that the chemistry of the interstellar medium is capable of producing such complex organic molecules and that they may be widespread in our Galaxy. Aims. Our goal is to investigate the degree of chemical complexity that can be reached in the interstellar medium, in particular in dense star-forming regions. Methods. We performed an unbiased, spectral line survey toward Sgr B2(N) and (M), two regions where high-mass stars are formed, with the IRAM 30 m telescope in the 3 mm atmospheric transmission window. Partial surveys at

15 2 and 1.3 mm were performed in parallel. The spectra were analyzed with a simple radiative transfer model that assumes local thermodynamic equilibrium but takes optical depth effects into account. Results. About 3675 and 945 spectral lines with a peak signal-to-noise ratio higher than 4 are detected at 3 mm toward Sgr B2(N) and (M), i.e. about 102 and 26 lines per GHz, respectively. This represents an increase by about a factor of two over previous surveys of Sgr B2. About 70% and 47% of the lines detected toward Sgr B2(N) and (M) are identified and assigned to 56 and 46 distinct molecules as well as to 66 and 54 less abundant isotopologues of these molecules, respectively. In addition, we report the detection of transitions from 59 and 24 catalog entries corresponding to vibrationally or torsionally excited states of some of these molecules, respectively, up to a vibration energy of 1400 cm−1 (2000 K). Excitation temperatures and column densities were derived for each species but should be used with caution. The rotation temperatures of the detected complex molecules typically range from ∼ 50 to 200 K. Among the detected molecules, aminoacetonitrile, n-propyl cyanide, and ethyl formate were reported for the first time in space based on this survey, as were five rare isotopologues of vinyl cyanide, cyanoacetylene, and hydrogen cyanide. We also report the detection of transitions from within twelve new vibrationally or torsionally excited states of known molecules. Absorption features produced by diffuse clouds along the line of sight are detected in transitions with low rotation quantum numbers of many simple molecules and are modeled with ∼ 30–40 velocity components with typical linewidths of ∼ 3–5 km s−1. Conclusions. Although the large number of unidentified lines may still allow future identification of new molecules, we expect most of these lines to belong to vibrationally or torsionally excited states or to rare isotopologues of known molecules for which spectroscopic predictions are currently missing. Significant progress in extending the inventory of complex organic molecules in Sgr B2(N) and deriving tighter constraints on their location, origin, and abundance is expected in the near future thanks to an ongoing spectral line survey at 3 mm with ALMA in its cycles 0 and 1. The present single-dish survey will serve as a solid basis for the line identification and analysis of such an interferometric survey. Accepted by A&A http://xxx.lanl.gov/pdf/1308.5062

Neutral and Ionized Hydrides in Star-forming Regions – Observations with Herschel/HIFI Arnold O. Benz1, Simon Bruderer2, Ewine F. van Dishoeck2,3, Pascal Stäuber1 and Susanne F. Wampfler1,4 1 Institute for Astronomy, ETH Zurich, 8093 Zürich, Switzerland 2 Max Planck Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany 3 Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands 1 Institute for Astronomy, ETH Zurich, 8093 Zürich, Switzerland 4 Centre for Star and Planet Formation, Univ. of Copenhagen, Øster Voldgade 5-7, DK-1350 København K, Denmark E-mail contact: benz at astro.phys.ethz.ch The cosmic abundance of hydrides depends critically on high-energy UV, X-ray, and particle irradiation. Here we study hydrides in star-forming regions where irradiation by the young stellar object can be substantial, and density and temperature can be much enhanced over interstellar values. Lines of OH, CH, NH, SH and their ions OH+, CH+, + + + + NH , SH , H2O , and H3O were observed in star-forming regions by the HIFI spectrometer onboard the Herschel Space Observatory. Molecular column densities are derived from observed ground-state lines, models, or rotational diagrams. We report here on two prototypical high-mass regions, AFGL 2591 and W3 IRS5, and compare them to chemical calculations making assumptions on the high-energy irradiation. A model assuming no ionizing protostellar emission is compared with (i) a model assuming strong protostellar X-ray emission and (ii) a two-dimensional (2D) model including emission in the far UV (FUV, 6 – 13.6 eV) irradiating the outflow walls that separate the outflowing gas and infalling envelope material. We confirm that the effect of FUV in two dimensional models with enlarged irradiated surfaces is clearly noticeable. A molecule that is very sensitive to FUV irradiation is CH+, enhanced in abundance by more than 5 orders of magnitude. The HIFI observations of CH+ lines agree with the two-dimensional FUV model by Bruderer et al. which computes abundances, non-LTE excitation and line radiative transfer.20 It is concluded that CH+ is a good FUV tracer in star-forming regions. The effect of potential X-ray irradiation is not excluded, but cannot be demonstrated by the present data. Accepted by Journal of Physical Chemistry http://pubs.acs.org/doi/pdf/10.1021/jp312813a

16 High-Temperature Processing of Solids Through Solar Nebular Bow Shocks: 3D Radi- ation Hydrodynamics Simulations with Particles A.C. Boley1,2, M.A. Morris3, and S.J. Desch4 1 Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL, 32611, USA 2 Sagan Fellow 3 Center for Meteorite Studies, Arizona State University, P.O. Box 876004, Tempe, AZ 88287-6004, USA 4 School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, Arizona 85287-1404, USA E-mail contact: aaron.boley at gmail.com A fundamental, unsolved problem in Solar System formation is explaining the melting and crystallization of chondrules found in chondritic meteorites. Theoretical models of chondrule melting in nebular shocks has been shown to be consistent with many aspects of thermal histories inferred for chondrules from laboratory experiments; but, the mechanism driving these shocks is unknown. Planetesimals and planetary embryos on eccentric orbits can produce bow shocks as they move supersonically through the disk gas, and are one possible source of chondrule-melting shocks. We investigate chondrule formation in bow shocks around planetoids through 3D radiation hydrodynamics simulations. A new radiation transport algorithm that combines elements of flux-limited diffusion and Monte Carlo methods is used to capture the complexity of radiative transport around bow shocks. An equation of state that includes the rotational, vibrational, and dissociation modes of H2 is also used. Solids are followed directly in the simulations and their thermal histories are recorded. Adiabatic expansion creates rapid cooling of the gas, and tail shocks behind the embryo can cause secondary heating events. Radiative transport is efficient, and bow shocks around planetoids can −8 have luminosities ∼few×10 L⊙. While barred and radial chondrule textures could be produced in the radiative shocks explored here, porphyritic chondrules may only be possible in the adiabatic limit. We present a series of predicted cooling curves that merit investigation in laboratory experiments to determine whether the solids produced by bow shocks are represented in the meteoritic record by chondrules or other solids. Accepted by ApJ http://arxiv.org/pdf/1308.2968

The VLTI/MIDI survey of massive young stellar objects - Sounding the inner regions around intermediate- and high-mass young stars using mid-infrared interferometry Paul A. Boley1,2, Hendrik Linz1, Roy van Boekel1, Thomas Henning1, Markus Feldt1, Lex Kaper3, Christoph Leinert1, AndréMüller4, Ilaria Pascucci5, Massimo Roberto6, Bringfried Stecklum7, L.B.F.M. Waters8,3 and Hans Zinnecker9 1 Max Planck Institute for Astronomy, Königstuhl 17, Heidelberg 69117, Germany 2 Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, Bonn 53121, Germany 3 Astronomical Institute Anton Pannekoek, Science Park 904, Amsterdam 1098 XE, The Netherlands 4 European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile 5 Lunar and Planetary Laboratory, University of Arizona, Tucson AZ 85721, United States 6 Space Telescope Science Institute, 3700 San Martin Dr., Baltimore MD 21212, United States 7 Thüringer Landessternwarte, Sternwarte 5, Tautenburg 07778, Germany 8 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, Utrecht 3584 CA, The Netherlands 9 SOFIA Science Center, NASA Ames Research Center, Mail Stop N232-12, Moffet Field CA 94035, United States E-mail contact: pboley at mpifr-bonn.mpg.de We aim to characterize the distribution and composition of circumstellar material around young massive stars, and to investigate exactly which physical structures in these objects are probed by long-baseline mid-infrared interferometric observations. We used the two-telescope interferometric instrument MIDI of the Very Large Telescope Interferometer of the European Southern Observatory to observe a sample of 24 intermediate- and high-mass young stellar objects in the N band (8–13 micron). We had successful fringe detections for 20 objects, and present spectrally-resolved correlated fluxes and visibility levels for projected baselines of up to 128 m. We fit the visibilities with geometric models to derive the sizes of the emitting regions, as well as the orientation and elongation of the circumstellar material. Fourteen objects in the sample show the 10 micron silicate feature in absorption in the total and correlated flux spectra. For

17 13 of these objects, we were able to fit the correlated flux spectra with a simple absorption model, allowing us to constrain the composition and absorptive properties of the circumstellar material. Nearly all of the massive young stellar objects observed show significant deviations from spherical symmetry at mid-infrared wavelengths. In general, the mid-infrared emission can trace both disks and outflows, and in many cases it may be difficult to disentangle these components on the basis of interferometric data alone, because of the sparse spatial frequency coverage normally provided by current long-baseline interferometers. For the majority of the objects in this sample, the absorption occurs on spatial scales larger than those probed by MIDI. Finally, the physical extent of the mid-infrared emission around these sources is correlated with the total luminosity, albeit with significant scatter. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1308.4282

Survival of molecular gas in cavities of transition disks (I. CO) Simon Bruderer1 1 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching, Germany E-mail contact: simonbruderer at gmail.com Context: Planet formation is closely related to the structure and dispersal of protoplanetary disks. A certain class of disks, called transition disks, exhibit cavities in dust images at scales of up to a few 10s of AU. The formation mechanism of the cavities is still unclear. The gas content of such cavities can be spatially resolved for the first time using the Atacama Large Millimeter/submillimeter Array (ALMA). Aims: To develop a new series of models to simulate the physical conditions and chemical abundances of the gas in cavities to address the question whether the gas is primarily atomic or molecular inside the dust free cavities exposed to intense UV radiation. Molecular/atomic line emission by carbon monoxide (CO), its isotopologues (13CO, C18O, C17O, and 13C18O) and related species ([C I], [C II], and [O I]) is predicted for comparison with ALMA and the Herschel Space Observatory. Method: We use a thermo-chemical model, which calculates the radiative transfer both in lines and the continuum, and solves for the chemical abundances and gas temperature. The model is based on our previous work, but includes several improvements. We study the dependence of CO abundances and lines on several parameters such as gas mass in the cavity, disk mass and luminosity of the star. Results: The gas can remain in molecular form down to very low amounts of gas in the cavity (∼1% ofMEarth). Shielding of the stellar radiation by a dusty inner disk (“pre-transition disk”) allows CO to survive down to lower gas masses in the cavity. The column densities of H2 and CO in the cavity scale almost linearly with the amount of gas in the cavity down to the mass where photodissociation becomes important. The main parameter for the CO emission from cavity is the gas mass. Other parameters such as the outer disk mass, bolometric luminosity, shape of the stellar spectrum or PAH abundance are less important. Since the CO pure rotational lines readily become optically thick, the CO isotopologues need to be observed in order to quantitatively determine the amount of gas in the cavity. Determining gas masses in the cavity from atomic lines ([C I], [C II], and [O I]) is challenging. Conclusions: A wide range of gas masses in the cavity of transition disks (∼ 4 orders of magnitude) can be probed using combined observations of CO isotopologue lines with ALMA. Measuring the gas mass in the cavity will ultimately help to distinguish between different cavity formation theories. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1308.2966

Towards Precise Ages and Masses of Free Floating Planetary Mass Brown Dwarfs J.I. Canty1, P.W. Lucas1, P.F. Roche2, and D.J. Pinﬁeld1 1 Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hateld, AL10 9AB, UK 2 Astrophysics Department, University of Oxford, 1 Keble Road, Oxford OX1 3RH, UK E-mail contact: j.canty2 at herts.ac.uk Measurement of the substellar initial mass function (IMF) in very young clusters is hampered by the possibility of the age spread of cluster members. This is particularly serious for candidate planetary mass objects (PMOs), which

18 have a very similar location to older and more massive brown dwarfs on the Hertzsprung-Russell Diagram (HRD). This degeneracy can be lifted by the measurement of gravity-sensitive spectral features. To this end we have obtained medium resolution (R∼5000) Near-infrared Integral Field Spectrometer (NIFS) K band spectra of a sample of late M- / early L-type dwarfs. The sample comprises old field dwarfs and very young brown dwarfs in the Taurus association and in the σ Orionis cluster. We demonstrate a positive correlation between the strengths of the 2.21 µm NaI doublet and the objects’ ages. We demonstrate a further correlation between these objects’ ages and the shape of their K band spectra. We have quantified this correlation in the form of a new index, the H2(K) index. This index appears to be more gravity-sensitive than the NaI doublet and has the advantage that it can be computed for spectra where gravity-sensitive spectral lines are unresolved, while it is also more sensitive to surface gravity at very young ages (<10 Myr) than the triangular H band peak. Both correlations differentiate young objects from field dwarfs, while the H2(K) index can distinguish, at least statistically, populations of ∼1 Myr objects from populations of ∼10 Myr objects. We applied the H2(K) index to NIFS data for one Orion nebula cluster (ONC) PMO and to previously published low resolution spectra for several other ONC PMOs where the 2.21 µm NaI doublet was unresolved and concluded that the average age of the PMOs is ∼1 Myr. Accepted by MNRAS http://arxiv.org/pdf/1308.1296

Diffraction-limited Visible Light Images of Orion Trapezium Cluster With the Magellan Adaptive Secondary AO System (MagAO) L.M. Close1, J.R. Males1, K. Morzinski1,4, D. Kopon1,5, K. Follette1, T.J. Rodigas1, P. Hinz1, Y.-L. Wu1, A. Puglisi2, S. Esposito2, A. Riccardi2, E. Pinna2, M. Xompero2, R. Briguglio2, A. Uomoto3, T. Hare3 1 Steward Observatory, University of Arizona, Tucson, AZ 85721, USA 2 INAF - Osservatorio Astrosico di Arcetri, I-50125, Firenze, Italy 3 Carnegie Observatories, 813 Santa Barbara Street, Pasadena, California, 91101 USA 4 NASA Sagan Fellow 5 MPiA, Germany E-mail contact: lclose at as.arizona.edu We utilized the new high-order (250-378 mode) Magellan Adaptive Optics system (MagAO) to obtain very high spatial resolution observations in ”visible light” with MagAO’s VisAO CCD camera. In the good-median seeing conditions of Magellan (0′′. 5–0′′. 7) we find MagAO delivers individual short exposure images as good as 19 mas optical resolution. Due to telescope vibrations, long exposure (60s) r’ (0.63 µm) images are slightly coarser at FWHM=23–29 mas (Strehl ∼28%) with bright (R<9 mag) guide stars. These are the highest resolution filled-aperture images published to date. Images of the young (∼1 Myr) Orion Trapezium θ1 Ori A, B, and C cluster members were obtained with VisAO. In particular, the 32 mas binary θ1 Ori C1/C2 was easily resolved in non-interferometric images for the first time. Relative positions of the bright trapezium binary stars were measured with ∼0.6–5 mas accuracy. We now are sensitive to relative proper motions of just ∼0.2 mas yr−1 (∼0.4 km s−1 at 414 pc) - this is a ∼2–10x improvement in orbital velocity accuracy compared to previous efforts. For the first time, we see clear motion of the barycenter of θ1 Ori B2/B3 about θ1 Ori B1. All five members of the θ1 Ori B system appear likely a gravitationally bound ”mini-cluster”, but we find that not all the orbits can be both circular and co-planar. The lowest mass member of the θ1 Ori B −1 system (B4; mass ∼0.2 M⊙) has a very clearly detected motion (at 4.1±1.3 km s ; correlation=99.9%) w.r.t B1 and will likely be ejected in the future. This ”ejection” process of the lowest mass member of a ”mini-cluster” could play a major role in the formation of low mass stars and brown dwarfs.(slightly abridged abstract) Accepted by ApJ http://arxiv.org/pdf/1308.4155

+ Broad N2H emission towards the protostellar shock L1157-B1 C. Codella1, S. Viti2, C. Ceccarelli3, B. Leﬂoch3, M. Benedettini4, G. Busquet4, P. Caselli5, F. Fontani1, A. G´omez-Ruiz1, L. Podio3 and M. Vasta1

19 1 INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy 2 Department of Physics and Astronomy, University College London, London, UK 3 UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno- ble, F-38041, France 4 INAF, Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133, Roma, Italy 5 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK E-mail contact: codella at arcetri.astro.it + We present the first detection of N2H towards a low-mass protostellar outflow, namely the L1157-B1 shock, at ∼ 0.1 pc from the protostellar cocoon. The detection was obtained with the IRAM 30-m antenna. We observed emission at 93 GHz due to the J = 1–0 hyperfine lines. The analysis of the emission coupled with the HIFI CHESS multiline + 5 −3 CO observations leads to the conclusion that the observed N2H (1–0) line originates from the dense (≥ 10 cm ) + gas associated with the large (20arcsec–25arcsec) cavities opened by the protostellar wind. We find a N2H column 12 −2 −9 + density of few 10 cm corresponding to an abundance of (2–8) × 10 . The N2H abundance can be matched by a model of quiescent gas evolved for more than 104 yr, i.e. for more than the shock kinematical age (≃ 2000 + yr). Modelling of C-shocks confirms that the abundance of N2H is not increased by the passage of the shock. In + 4 −3 summary, N2H is a fossil record of the pre-shock gas, formed when the density of the gas was around 10 cm , and then further compressed and accelerated by the shock. Accepted by ApJ http://arxiv.org/pdf/1308.6478

Haffner 16: A Young Moving Group in the Making T.J. Davidge1, Eleazar R. Carrasco2, Claudia Winge2, Peter Pessev2, Benoit Neichel2, Fabrice Vidal2, and Francois Rigaut3 1 Dominion Astrophysical Observatory, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC Canada V9E 2E7 2 Gemini Observatory/AURA, Southern Operations Center, Casilla 603, La Serena, Chile 3 Australian National University, Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611, Australia E-mail contact: tim.davidge at nrc.ca The photometric properties of main sequence (MS) and pre-main sequence (PMS) stars in the young cluster Haffner 16 are examined using images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric blurring by the Gemini Multi-Conjugate Adapative Optics System (GeMS). A rich population of PMS stars is identified, and comparisons with isochrones suggest an age < 10 Myr assuming a distance modulus of 13.5 (D = 5 kpc). When compared with the solar neighborhood, Haffner 16 is roughly a factor of two deficient in objects with sub-solar masses. PMS objects in the cluster are also more uniformly distributed on the sky than bright MS stars. It is suggested that Haffner 16 is dynamically evolved, and that it is shedding protostars with sub-solar masses. Young low mass clusters like Haffner 16 are one possible source of PMS stars in the field. The cluster will probably evolve on time scales of ∼ 100 – 1000 Myr into a diffuse moving group with a mass function that is very different from that which prevailed early in its life. Accepted by the Astronomical Society of the Pacific http://arxiv.org/pdf/1308.5432

Magnetospheric accretion on the fully-convective classical T Tauri star DN Tau J.-F. Donati1, S.G. Gregory2, S.H.P. Alencar3, G. Hussain4, J. Bouvier5, M.M. Jardine2, F. Ménard6,5, C. Dougados6,5, M.M. Romanova7, and the MaPP collaboration 1 UPS-Toulouse / CNRS-INSU, Institut de Recherche en Astrophysique et Planétologie (IRAP) UMR 5277, Toulouse, F31400 France 2 School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Scotland KY16 9SS, UK 3 Departamento de F´ısica – ICEx – UFMG, Av. Antônio Carlos, 6627, 30270-901 Belo Horizonte, MG, Brazil

20 4 ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany 5 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno- ble, F-38041, France 6 UMI-FCA, CNRS/INSU, France (UMI 3386), and Universidad de Chile, Santiago, Chile 7 Department of Astronomy, Cornell University, Ithaca, NY 14853-6801, USA E-mail contact: jean-francois.donati at irap.omp.eu We report here results of spectropolarimetric observations of the classical T Tauri star DN Tau carried out (at 2 epochs) with ESPaDOnS at the Canada-France-Hawaii Telescope within the ‘Magnetic Protostars and Planets’ programme. We infer that DN Tau, with a photospheric temperature of 3,950±50 K, a luminosity of 0.8±0.2 L⊙ and a rotation period of 6.32 d, is a ∼2 Myr-old fully-convective 0.65±0.05 M⊙ star with a radius of 1.9±0.2 R⊙, viewed at an inclination of 35±10◦. Clear circularly-polarized Zeeman signatures are detected in both photospheric and accretion-powered emission lines, probing longitudinal fields of up to 1.8 kG (in the He i D3 accretion proxy). Rotational modulation of Zeeman signatures, detected both in photospheric and accretion lines, is different between our 2 runs, providing further evidence that fields of cTTSs are generated by non-stationary dynamos. Using tomographic imaging, we reconstruct maps of the large-scale field, of the photospheric brightness and of the accretion-powered emission at the surface of DN Tau at both epochs. We find that the magnetic topology is mostly poloidal, and largely axisymmetric, with an octupolar component (of polar strength 0.6–0.8 kG) 1.5–2.0× larger than the dipolar component (of polar strength 0.3–0.5 kG). DN Tau features dominantly poleward accretion at both epochs. The large-scale dipole component of DN Tau is however too weak to disrupt the surrounding accretion disc further than 65–90% of the corotation radius (at which the disc Keplerian period matches the stellar rotation period), suggesting that DN Tau is already spinning up despite being fully convective. Accepted by MNRAS http://arxiv.org/pdf/1308.5143

CO outflows from high-mass Class 0 protostars in Cygnus-X A. Duarte-Cabral1,2, S. Bontemps1,2, F. Motte3, M. Hennemann3, N. Schneider1,2 and Ph. Andre3 1 Univ. Bordeaux, LAB, UMR 5804, F-33270, Floirac, France. 2 CNRS, LAB, UMR 5804, F-33270, Floirac, France 3 Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/Service d’Astrophysique, C.E. Saclay, Orme de merisiers, 91191 Gif-sur-Yvette, France E-mail contact: cabral at obs.u-bordeaux1.fr As natural consequences of the accretion process, outflows are one of the few (indirect) tracers of accretion. We used CO(2-1) PdBI observations towards 6 MDCs in Cygnus-X, containing 9 high-mass cores, to investigate what the accretion process and origin of the material feeding the precursors of high-mass stars are. We compared our sample to low-mass objects from the literature and developed simple evolutionary models to reproduce the observables. We find that 8/9 high-mass cores drive clear individual outflows as true equivalents of Class 0 protostars in the high-mass regime. The remaining core has only a tentative outflow detection. It could be amongst the first examples of a true individual high-mass prestellar core. We find that the momentum flux of high-mass objects has a linear relation to the envelope mass, as a scale-up of the relations found for low-mass protostars. This suggests a fundamental proportionality between accretion rates and mass reservoir, suggesting identical collapse timescales for all masses. We conclude that if the pre-collapse evolution is quasi-static, the fragmentation scale (which is similar for all masses) would limit the size of the initial mass reservoirs, leading to shorter free-fall times for higher mass stars. However, as we find identical collapse timescales for all masses, a significant turbulent/magnetic support is needed to slow down the collapse of the more massive envelopes in a quasi-static view. With this support still to be discovered, and with indications of large dynamics in pre-collapse gas for high-mass star formation, we propose that such an identical collapse timescale implies that the initial densities, which should set the duration of the collapse, should be similar for all masses. This suggests that the mass that incorporates massive stars has to have been accreted in a dynamical way from larger scales than those of low-mass stars.

21 Accepted by A&A http://arxiv.org/pdf/1308.6490

The curiously circular orbit of Kepler-16b Alex Dunhill1 and Richard Alexander1 1 Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK E-mail contact: alex.dunhill at leicester.ac.uk The recent discovery of a number of circumbinary planets lends a new tool to astrophysicists seeking to understand how and where planet formation takes place. Of the increasingly numerous circumbinary systems, Kepler-16 is arguably the most dynamically interesting: it consists of a planet on an almost perfectly circular orbit (e = 0.0069) around a moderately eccentric binary (e =0.16). We present high-resolution 3D smoothed-particle hydrodynamics simulations of a Kepler-16 analogue embedded in a circumbinary disc, and show that the planet’s eccentricity is damped by its interaction with the protoplanetary disc. We use this to place a lower limit on the gas surface density in the real disc −2 through which Kepler-16b migrated of Σmin ∼ 10 g cm . This suggests that Kepler-16b, and other circumbinary planets, formed and migrated in relatively massive discs. We argue that secular evolution of circumbinary discs requires that these planets likely formed early on in the lifetime of the disc and migrated inwards before the disc lost a signiﬁcant amount of its original mass. Accepted by MNRAS http://www.astro.le.ac.uk/users/acd23/K16.html

The Gould’s Belt Very Large Array Survey I: The Ophiuchus complex Sergio A. Dzib1, Laurent Loinard1,2, Amy J. Mioduszewski3, Luis F. Rodr´ıguez1,4, Gisela N. Ortiz- León1, Gerardo Pech1, Juana L. Rivera1, Rosa M. Torres5, Andrew F. Boden6, Lee Hartmann7, Neal J. Evans II8, Cesar Briceño9 and John Tobin10 1 Centro de Radiostronom´ıay Astrof´ısica, Universidad Nacional Autónoma de Mexico, Morelia 58089, Mexico 2 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 3 National Radio Astronomy Observatory, Domenici Science Operations Center, 1003 Lopezville Road, Socorro, NM 87801, USA 4 King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia 5 Paul Harris 9065, Las Condes, Santiago, Chile 6 Division of Physics, Math, and Astronomy, California Institute of Technology, 1200 E California Blvd., Pasadena, CA 91125, USA 7 Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48105, USA 8 Department of Astronomy, The University of Texas at Austin, 1 University Station, C1400, Austin, TX 78712, USA 9 Centro de Investigaciones de Astronom´ıa, Mérida, 5101-A, Venezuela 10 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA E-mail contact: s.dzib at crya.unam.mx We present large-scale (∼ 2000 square arcminutes), deep (∼ 20 µJy), high-resolution (∼ 1′′) radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array at λ = 4 and 6 cm. In total, 189 sources were detected, 56 of them associated with known young stellar sources, and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although we also detect 4 objects of A/F/B types and 2 brown dwarf candidates. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronas characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a Güdel-Benz relation, but with a different normalization than the most radio-active types of stars. Finally, we detect a ∼ 70 mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations

22 of this region. Accepted by The Astrophysical Journal

Radio Sources Embedded in the Dense Core B59, the “Mouthpiece” of the Pipe Nebula Sergio A. Dzib1, Luis F. Rodr´ıguez1,2, Anabella T. Araudo1 and Laurent Loinard1 1 Centro de Radioastronom´ıay Astrof´ısica, Universidad Nacional Autónoma de México, Campus Morelia 2 Astronomy Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia E-mail contact: s.dzib at crya.unam.mx We present Very Large Array continuum observations made at 8.3 GHz toward the dense core B59, in the Pipe Nebula. We detect six compact sources, of which five are associated with the five most luminous sources at 70 µm in the region, while the remaining one is probably a background source. We propose that the radio emission is free-free from the ionized outflows present in these protostars. We discuss the kinematical impact of these winds in the cloud. We also propose that these winds are optically thick in the radio but optically thin in the X-rays and that this characteristic can explain why X-rays from the magnetosphere are detected in three of them, while the radio emission is most probably dominated by the free-free emission from the external layers of the wind. Accepted by Revista Mexicana de Astronom´ıay Astrof´ısica http://arxiv.org/pdf/1308.2621

RCW36: characterizing the outcome of massive star formation Lucas Ellerbroek1, Arjan Bik2, Lex Kaper1, Koen Maaskant3,1, Mieke Paalvast1, Frank Tramper1, Hugues Sana1, Rens Waters4,1 and Zoltan Balog2 1 Astronomical Institute Anton Pannekoek, University of Amsterdam, P.O. Box 94249, 1090 GE Amsterdam, The Netherlands 2 Max-Planck-Institut für Astronomie, Königstuhl 17, Heidelberg, Germany 3 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands 4 SRON, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands E-mail contact: l.e.ellerbroek at uva.nl Massive stars play a dominant role in the process of clustered star formation, with their feedback into the molecular cloud through ionizing radiation, stellar winds and outflows. The formation process of massive stars is poorly constrained because of their scarcity, the short formation timescale and obscuration. By obtaining a census of the newly formed stellar population, the star formation history of the young cluster and the role of the massive stars within it can be unraveled. We aim to reconstruct the formation history of the young stellar population of the massive star-forming region RCW 36. We study several dozens of individual objects, both photometrically and spectroscopically, look for signs of multiple generations of young stars and investigate the role of the massive stars in this process. We obtain a census of the physical parameters and evolutionary status of the young stellar population. Using a combination of near-infrared photometry and spectroscopy we estimate ages and masses of individual objects. We identify the population of embedded young stellar objects (YSO) by their infrared colors and emission line spectra. RCW 36 harbors a stellar population of massive and intermediate-mass stars located around the center of the cluster. Class 0/I and II sources are found throughout the cluster. The central population has a median age of 1.1 ± 0.6 Myr. Of the stars which could be classified, the most massive ones are situated in the center of the cluster. The central cluster is surrounded by filamentary cloud structures; within these, some embedded and accreting YSOs are found. Our age determination is consistent with the filamentary structures having been shaped by the ionizing radiation and stellar winds of the central massive stars. The formation of a new generation of stars is ongoing, as demonstrated by the presence of embedded protostellar clumps, and two exposed jets. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1308.3238

23 DIGIT survey of far-infrared lines from protoplanetary disks I D. Fedele1, S. Bruderer1, E.F. van Dishoeck1,2, J. Carr3, G.J. Herczeg4, C. Salyk5, Neal J. Evans II6, J. Bouwman7, G. Meeus8, Th. Henning7, J. Green6, J.R. Najita5, M. Guedel9 1 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany 2 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands 3 Naval Research Laboratory, Code 7211, Washington, DC 20375, USA 4 Kavli Institute for Astronomy and Astrophysics, Yi He Yuan Lu 5, Beijing, 100871, P.R. China 5 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA 6 University of Texas at Austin, Department of Astronomy, 2515 Speedway, Stop C1400, Austin TX 78712-1205, USA 7 Max Planck Institute for Astronomy, Konigstuhl 17, 69117, Heidelberg, Germany 8 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, Spain 9 Universität Wien, Dr.-Karl-Lueger-Ring 1, 1010, Wien, Austria E-mail contact: fedele at mpe.mpg.de [abridged] We present far-infrared spectroscopic observations of PMS stars taken with Herschel/PACS as part of the DIGIT key project. The sample includes 22 Herbig AeBe and 8 T Tauri sources. Multiple atomic fine structure + and molecular lines are detected at the source position: [OI], [CII], CO, OH, H2O, CH . The most common feature is the [OI] 63 µm line detected in almost all of the sources followed by OH. In contrast with CO, OH is detected toward both Herbig AeBe groups (flared and non-flared sources). An isothermal LTE slab model fit to the OH lines 13 16 −2 indicates column densities of 10

The First Circumstellar Disk Imaged in Silhouette with Adaptive Optics: MagAO Imag- ing of Orion 218-354 Katherine B. Follette1, Laird M. Close1, Jared R. Males1,4, Derek Kopon2, Ya-Lin Wu1, Katie M. Morzinski1,4, Philip Hinz.1, Timothy J. Rodigas1, Alfio Puglisi3, Simone Esposito3, Armando Riccardi3, Enrico Pinna3, Marco Xompero3, Runa Briguglio3 1 Steward Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721, USA 2 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany 3 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Firenze, Italy 4 NASA Sagan Fellow E-mail contact: kfollette at as.arizona.edu We present high resolution adaptive optics (AO) corrected images of the silhouette disk Orion 218-354 taken with Magellan AO (MagAO) and its visible light camera, VisAO, in simultaneous differential imaging (SDI) mode at Hα. This is the first image of a circumstellar disk seen in silhouette with adaptive optics and is among the first visible light adaptive optics results in the literature. We derive the disk extent, geometry, intensity and extinction profiles and find, in contrast with previous work, that the disk is likely optically-thin at Hα. Our data provide an estimate of the column density in primitive, ISM-like grains as a function of radius in the disk. We estimate that only ∼10% of the total sub-mm derived disk mass lies in primitive, unprocessed grains. We use our data, Monte Carlo radiative transfer modeling and previous results from the literature to make the first self-consistent multiwavelength model of Orion 218-354. We find that we are able to reproduce the 1-1000 µm SED with a ∼2–540 AU disk of the size, geometry,

24 small vs. large grain proportion and radial mass proﬁle indicated by our data. This inner radius is a factor of ∼15 larger than the sublimation radius of the disk, suggesting that it is likely cleared in the very interior. Accepted by ApJL http://arxiv.org/pdf/1308.4147

The L 1157 protostellar outflow imaged with the SMA A. I. Gómez-Ruiz1,2, N. Hirano3, S. Leurini2 and S.-Y. Liu3 1 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 3 Academia Sinica,Institute of Astronomy & Astrophysics, P.O. Box 23–141, Taipei, 106, Taiwan, R.O.C. E-mail contact: ivangomezru at gmail.com The outflow driven by the class 0 low-mass protostar L1157-mm stands out for its peculiar chemical richness. However, its complex spatial/velocity structure makes difficult to interpret observations of different molecular tracers. The present work aims at mapping, at high spatial resolution, different molecular tracers that are important tools to study shocks and/or thermal-density structures in outflows. We use the Submillimeter Array to observe, at 1.4 mm, the blue-lobe of the L1157 outflow at high spatial resolution (∼ 3”). We detected SiO, H2CO, and CH3OH lines from several molecular clumps that constitute the outflow. All three molecules were detected along the wall of the inner cavity that is supposedly related with the later ejection event. On the other hand, no emission was detected towards positions related to an old ejection episode, likely due to space filtering from the interferometer. The H2CO and CH3OH emission is detected only at velocities close to the systemic velocity. The spatial distributions of the H2CO and CH3OH are similar. These emission lines trace the U-shaped structure seen in the mid-infrared image. In contrast, the SiO emission is detected in wider velocity range with a peak at ∼14 km s−1 blue-shifted from the systemic velocity. The SiO emission is brightest at the B1 position, which corresponds to the apex of the U-shaped structure. There are two compact SiO clumps along the faint arc-like feature to the east of the U-shaped structure. At the B1 position, there are two velocity components; one is a compact clump with a size of ∼1500 AU seen in the high-velocity and the other is an extended component with lower velocities. The kinematic structure at the B1 position is different from that expected in a single bow shock. It is likely that the high-velocity SiO clump at the B1 position is kinetically independent from the low-velocity gas. The line ratio between SiO (5–4) and SiO (2–1) suggests that the high velocity SiO clumps consist of high density gas of n∼105 - 106 cm−3, which is comparable to the density of the bullets in the extremely high velocity (EHV) jets. It is likely that the high-velocity SiO clumps in L1157 have the same origin as the EHV bullets. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1308.3091

The CN/C15N isotopic ratio towards dark clouds P. Hily-Blant1, G. Pineau des Forêts2, A. Faure1, R. Le Gal1, and M. Padovani3 1 UniversitéJoseph Fourier and CNRS, Institut de Planétologie et d’Astrophysique, Grenoble, France 2 UniversitéParis-Orsay and CNRS, Institut d’Astrophysique Spatiale, Orsay, France 3 LRA/CNRS, Observatoire de Paris & Ecole´ normale supérieure, Paris, France E-mail contact: pierre.hily-blant at obs.ujf-grenoble.fr Understanding the origin of the composition of solar system cosmomaterials is a central question, not only in the cosmochemistry and astrochemistry fields, and requires various approaches to be combined. Measurements of isotopic ratios in cometary materials provide strong constraints on the content of the protosolar nebula. Their relation with the composition of the parental dark clouds is, however, still very elusive. In this paper, we bring new constraints based on the isotopic composition of nitrogen in dark clouds, with the aim of understanding the chemical processes that are responsible for the observed isotopic ratios. We have observed and detected the fundamental rotational transition of C15N towards two starless dark clouds, L1544 and L1498. We were able to derive the column density ratio of C15N over 13CN towards the same clouds, and obtain the CN/C15N isotopic ratios, which were found to be 500 ± 75 for both L1544 and L1498. These values are therefore marginally consistent with the protosolar value of 441. Moreover,

25 this ratio is larger than the isotopic ratio of nitrogen measured in HCN. In addition, we present model calculations of the chemical fractionation of nitrogen in dark clouds, which make it possible to understand how CN can be deprived 15 + of N and HCN can simultaneously be enriched in heavy nitrogen. The non-fractionation of N2H , however, remains an open issue and we propose some chemical way of alleviating the discrepancy between model predictions and the observed ratios. Accepted by A&A http://arxiv.org/pdf/1308.4380

Herschel/PACS Survey of protoplanetary disks in Taurus/Auriga – Observations of [OI] and [CII], and far infrared continuum Christian D. Howard1,2, Göran Sandell1, William D. Vacca1, Gaspard Duchêne3,4, Geoffrey Mathews5,6, Jean-Charles Augereau4, David Barrado7,8, William R. F. Dent9, Carlos Eiroa10, Carol Grady11,12,13, Inga Kamp14, Gwendolyn Meeus10, Francois Ménard4,15, Christophe Pinte4, Linda Podio4, Pablo Riviere-Marichalar7, Aki Roberge11, Wing-Fai Thi4, Silvia Vicente14 and Jonathan P. Williams6 1 SOFIA-USRA, NASA Ames Research Center, MS 232-12, Building N232, Rm. 146, P. O. Box 1, Moffett Field, CA 94035-0001, USA 2 Google, 1600 Amphitheatre Parkway, Mountain View, CA 94043, USA 3 Astronomy Department, University of California, Berkeley, CA 94720-3411, USA 4 UJF-Grenoble 1 / CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, Grenoble, 38041, France 5 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands 6 Institute for Astronomy (IfA), University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822, USA 7 Centro de Astrobiolog´ıa−Depto. Astrof´ısica (CSIC/INTA), ESAC Campus, P.O. Box 78, 28691 Villanueva de la Cañada, Spain 8 Calar Alto Observatory, Centro Astronómico Hispano Alemán, C/Jesús Durbán Remón, E-04004 Almer´ıa, Spain 9 ALMA SCO, Alonso de Córdova 3107, Vitacura, Santiago, Chile 10 Dep. de F´ısica Teórica, Fac. de Ciencias, UAM Campus Cantoblanco, 28049 Madrid, Spain 11 Exoplanets & Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 667, Greenbelt, MD, 20771, USA 12 Eureka Scientific, 2452 Delmer, Suite 100, Oakland CA 96002, USA 13 Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 14 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands 15 UMI-FCA (UMI 3386: CNRS France, and U de Chile / PUC / U Conception), Santiago, Chile E-mail contact: gsandell at sofia.usra.edu The Herschel Space Observatory was used to observe ∼ 120 pre-main-sequence stars in Taurus as part of the GASPS Open Time Key project. PACS was used to measure the continuum as well as several gas tracers such as [OI] 63 µm, [OI] 145 µm, [CII] 158 µm, OH, H2O and CO. The strongest line seen is [OI] at 63 µm. We find a clear correlation between the strength of the [OI] 63 µm line and the 63 µm continuum for disk sources. In outflow sources, the line emission can be up to 20 times stronger than in disk sources, suggesting that the line emission is dominated by the outflow. The tight correlation seen for disk sources suggests that the emission arises from the inner disk (< 50 AU) and lower surface layers of the disk where the gas and dust are coupled. The [OI] 63 µm is fainter in transitional stars than in normal Class II disks. Simple SED models indicate that the dust responsible for the continuum emission is colder in these disks, leading to weaker line emission. [CII] 158 µm emission is only detected in strong outflow sources. The observed line ratios of [OI] 63 µm to [OI] 145 µm are in the regime where we are insensitive to the gas-to-dust ratio, neither can we discriminate between shock or PDR emission. We detect no Class III object in [OI] 63 µm and only three in continuum, at least one of which is a candidate debris disk. Accepted by Astrophysical Journal http://arxiv.org/pdf/1308.6019

26 Water Absorption from Gas Very Near the Massive Protostar AFGL 2136 IRS 1 Nick Indriolo1, D.A. Neufeld1, A. Seifahrt2, M.J. Richter3 1 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA 2 Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA 3 Department of Physics, University of California Davis, Davis, CA 95616, USA E-mail contact: indriolo at pha.jhu.edu

We present ground-based observations of the ν1 and ν3 fundamental bands of H2O toward the massive protostar AFGL 2136 IRS 1, identifying absorption features due to 47 diﬀerent ro-vibrational transitions between 2.468 µm and 2.561 9 µm. Analysis of these features indicates the absorption arises in warm (T = 506 ± 25 K), very dense (n(H2) > 5 × 10 cm−3) gas, suggesting an origin close to the central protostar. The total column density of warm water is estimated 19 −2 −4 to be N(H2O) = (1.02 ± 0.02) × 10 cm , giving a relative abundance of N(H2O)/N(H2) ∼ 10 . Our study represents the ﬁrst extensive use of water vapor absorption lines in the near infrared, and demonstrates the utility of such observations in deriving physical parameters. Accepted by ApJ http://arxiv.org/pdf/1308.2963

26Al in the Early Solar System: Not so Unusual After All M. Jura1, S. Xu1, and E.D. Young2 1 Department of Physics and Astronomy, University of California, Los Angeles CA 90095-1562, USA 2 Department of Earth and Space Sciences, University of California, Los Angeles CA 90095, USA E-mail contact: jura at astro.ucla.edu Recently acquired evidence shows that extrasolar asteroids exhibit over a factor of 100 variation in the iron to aluminum abundance ratio. This large range likely is a consequence of igneous diﬀerentiation that resulted from heating produced by radioactive decay of 26Al with an abundance comparable to that in the solar system’s protoplanetary disk at birth. If so, the conventional view that our solar system began with an unusually high amount of 26Al should be discarded. Accepted by ApJL http://arxiv.org/pdf/1308.6325

Uncertainties in water chemistry in disks: An application to TW Hya I. Kamp1, W.-F. Thi2, G. Meeus3, P. Woitke4, C. Pinte2, R. Meijerink1, M. Spaans1, I. Pascucci5, G. Aresu1, and W.R.F. Dent6 1 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands 2 UniversitéJoseph Fourier Grenoble-1, CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, Grenoble, F-38041, France 3 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, Spain 4 SUPA, School of Physics & Astronomy, University of St. Andrews, North Haugh, ST. Andrews, KY16 9SS, UK 5 Lunar and Planetary Laboratory, 1629 E. University Blvd., Tucson AZ 85271-0092, USA 6 ALMA SCO, Alonso de Cordova 3107, Vitacura, Santiago, Chile E-mail contact: kamp at astro.rug.nl Context. This paper discusses the sensitivity of water lines to chemical processes and radiative transfer for the protoplanetary disk around TW Hya. The study focuses on the Herschel spectral range in the context of new line detections with the PACS instrument from the Gas in Protoplanetary Systems project (GASPS). Aims. The paper presents an overview of the chemistry in the main water reservoirs in the disk around TW Hya. It discusses the limitations in the interpretation of observed water line fluxes. Results. We report new line detections of p-H2O (322-211) at 89.99 µm and CO J=18-17 at 144.78 µm for the disk around TW Hya. Disk modeling shows that the far-IR fine structure lines ([OI], [CII]) and molecular submm lines are very robust to uncertainties in the chemistry, while the water line fluxes can change by factors of a few. The

27 water lines are optically thick, sub-thermally excited and can couple to the background continuum radiation field. The low-excitation water lines are also sensitive to uncertainties in the collision rates, e.g. with neutral hydrogen. The gas temperature plays an important role for the [OI] fine structure line fluxes, the water line fluxes originating from the inner disk as well as the high excitation CO, CH+ and OH lines. Conclusions. Due to their sensitivity on chemical input data and radiative transfer, water lines have to be used cautiously for understanding details of the disk structure. Water lines covering a wide range of excitation energies provide access to the various gas phase water reservoirs (inside and outside the snow line) in protoplanetary disks and thus provide important information on where gas-phase water is potentially located. Experimental and/or theoretical collision rates for H2O with atomic hydrogen are needed to diminish uncertainties from water line radiative transfer. Accepted by A&A http://arxiv.org/pdf/1308.1772

Fluffy dust forms icy planetesimals by static compression Akimasa Kataoka1,2, Hidekazu Tanaka3, Satoshi Okuzumi4 and Koji Wada5 1 Department of Astronomical ScienceSchool of Physical Sciences, Graduate University for Advanced Studies (SOK- ENDAI), Mitaka, 181-8588, Tokyo, Japan 2 National Astronomical Observatory of Japan, Mitaka, 181-8588 Tokyo, Japan 3 Institute of Low Temperature Science, Hokkaido University, Kita, 060-0819 Sapporo, Japan 4 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, 152-8551 Tokyo, Japan 5 Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, 275-0016 Chiba, Japan E-mail contact: akimasa.kataoka at nao.ac.jp Context. Several barriers have been proposed in planetesimal formation theory: bouncing, fragmentation, and radial drift problems. Understanding the structure evolution of dust aggregates is a key in planetesimal formation. Dust grains become fluffy by coagulation in protoplanetary disks. However, once they are fluffy, they are not sufficiently compressed by collisional compression to form compact planetesimals. Aims. We aim to reveal the pathway of dust structure evolution from dust grains to compact planetesimals. Methods. Using the compressive strength formula, we analytically investigate how fluffy dust aggregates are compressed by static compression due to ram pressure of the disk gas and self-gravity of the aggregates in protoplanetary disks. Results. We reveal the pathway of the porosity evolution from dust grains via fluffy aggregates to form planetesimals, circumventing the barriers in planetesimal formation. The aggregates are compressed by the disk gas to a density of 10−3g/cm3 in coagulation, which is more compact than is the case with collisional compression. Then, they are compressed more by self-gravity to 10−1g/cm3 when the radius is 10 km. Although the gas compression decelerates the growth, the aggregates grow rapidly enough to avoid the radial drift barrier when the orbital radius is ≤ 6 AU in a typical disk. Conclusions. We propose a fluffy dust growth scenario from grains to planetesimals. It enables icy planetesimal formation in a wide range beyond the snowline in protoplanetary disks. This result proposes a concrete initial condition of planetesimals for the later stages of the planet formation. Accepted by A&A http://www.aanda.org/articles/aa/abs/2013/09/aa22151-13/aa22151-13.html

Low Virial Parameters in Molecular Clouds: Implications for High Mass Star Formation and Magnetic Fields Jens Kauﬀmann1, Thushara Pillai1, and Paul F. Goldsmith2 1 Astronomy Department, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, USA 2 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Blvd., Pasadena, CA 91109, USA E-mail contact: tpillai at astro.caltech.edu Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study of the star formation process. Only ”supercritical” cloud fragments are able to collapse and form stars. The virial parameter, α = Mvir/M, which compares the virial to the actual mass, provides one way to gauge stability against

28 collapse. Supercritical cloud fragments are characterized by α< 2, as indicated by a comprehensive stability analysis considering perturbations in pressure and density gradients. Past research has suggested that virial parameters α> 2 prevail in clouds. This would suggest that collapse towards star formation is a gradual and relatively slow process, and that magnetic fields are not needed to explain the observed cloud structure. Here, we review a range of very recent observational studies that derive virial parameters ≪ 2 and compile a catalogue of 1325 virial parameter estimates. Low values of α are in particular observed for regions of high mass star formation (HMSF). These observations may argue for a more rapid and violent evolution during collapse. This would enable “competitive accretio” in HMSF, constrain some models of “monolithic collapse”, and might explain the absence of high–mass starless cores. Alternatively, the data could point at the presence of significant magnetic fields ∼1 mG at high gas densities. We examine to what extent the derived observational properties might be biased by observational or theoretical uncertainties. For a wide range of reasonable parameters, our conclusions appear to be robust with respect to such biases. Accepted by ApJ http://arxiv.org/pdf/1308.5679

Accretion through the inner edges of protoplanetary disks by a giant solid state pump T. Kelling1 and G. Wurm1 1 Faculty of Physics, University of Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany E-mail contact: thorben.kelling at uni-due.de At the inner edge of a protoplanetary disk solids are illuminated by stellar light. This illumination heats the solids and creates temperature gradients along their surfaces. Interactions with ambient gas molecules lead to a radial net gas ﬂow. Every illuminated solid particle within the edge is an individual small gas pump transporting gas inward. −5 −1 In total the inner edge can provide local mass ﬂow rates as high as M˙ = 10 M⊙ yr . Accepted by ApJL http://arxiv.org/pdf/1308.0921

Orbits and Masses in the young triple system TWA 5 R. Köhler1, T. Ratzka2, M. G. Petr-Gotzens3 and S. Correia4 1 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany 2 Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, 81679 München, Germany 3 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany 4 Institute for Astronomy, University of Hawaii, 34 Ohia Ku Str., Pukalani, HI 96768, USA E-mail contact: koehler at mpia-hd.mpg.de We want to improve the orbital elements and determine individual masses of the components of the triple system TWA5. Five new relative astrometric positions in the H band were recorded with NACO at the VLT. We combine them with data from the literature and a NACO-measurement in the Ks band. We derive an improved fit for the orbit of TWA5Aa-b around each other. Furthermore, we use the third component TWA5B as astrometric reference to solve for the motion of Aa and Ab around their center of mass and compute their mass ratio. We find an orbital period of 6.03 ± 0.01years and a semi-major axis of 63.7 ± 0.2 mas (3.2 ± 0.1 AU). With the trigonometric distance of 50.1 ± 1.8 pc, this yields a system mass of 0.9 ± 0.1 M⊙, where the error is dominated by the error of the distance. The dynamical mass is in agreement with the system mass predicted by a number of theoretical models, albeit only if TWA5 is at the young end of the age range of the TW Hydrae association. We find a mass ratio +0.6 MAb/MAa =1.3−0.4, with the less luminous component Ab being more massive. This result is probably a consequence of the large uncertainties due to the limited orbital coverage of the observations. Accepted by Astronomy & Astrophysics http://www.mpia-hd.mpg.de/homes/koehler/Papers/index.html

29 LIDT-DD: A new self-consistent debris disc model including radiation pressure and coupling dynamical and collisional evolution Quentin Kral1, Philippe Thébault1 and Sébastien Charnoz2 1 LESIA-Observatoire de Paris, UPMC Univ. Paris 06, Univ. Paris-Diderot, France 2 Laboratoire AIM, UniversitéParis Diderot / CEA / CNRS, Institut Universitaire de France E-mail contact: quentin.kral at obspm.fr In most current debris disc models, the dynamical and the collisional evolutions are studied separately, with N- body and statistical codes, respectively, because of stringent computational constraints. In particular, incorporating collisional effects (especially destructive collisions) into an N-body scheme has proven a very arduous task because of the exponential increase of particles it would imply. We present here LIDT-DD, the first code able to mix both approaches in a fully self-consistent way. Our aim is for it to be generic enough so as to be applied to any astrophysical cases where we expect dynamics and collisions to be deeply interlocked with one another: planets in discs, violent massive breakups, destabilized planetesimal belts, bright exozodiacal discs, etc. The code takes its basic architecture from the LIDT3D algorithm developed by Charnoz et al.(2012) for protoplanetary discs, but has been strongly modified and updated in order to handle the very constraining specificities of debris discs physics: high-velocity fragmenting collisions, radiation-pressure affected orbits, absence of gas that never relaxes initial conditions, etc. It has a 3D Lagrangian-Eulerian structure, where grains of a given size at a given location in a disc are grouped into ”super-particles”, or ”tracers”, whose orbits are evolved with an N-body code and whose mutual collisions are individually tracked and treated using a particle-in-a-box prescription designed to handle fragmenting impacts. To cope with the wide range of possible dynamics for same-sized particles at any given location in the disc, and in order not to lose important dynamical information, tracers are sorted and regrouped into dynamical families depending on their orbits. A complex reassignment routine, looking for redundant tracers into each family and reassigning them where they are needed, prevents the number of tracers from diverging. The LIDT-DD code has been successfully tested on simplified cases for which robust results have been obtained in past studies: we retrieve the classical features of particle size distributions in unperturbed discs, as well as the outer radial density profiles in ∼ r−1.5 outside narrow collisionally active rings, and the depletion of small grains in ”dynamically cold” discs. The potential of the new code is illustrated with the test case of the violent breakup of a massive planetesimal within a debris disc. Preliminary results show that, for the first time, we are able to quantify the timescale over which the signature of such massive break-ups can be detected. In addition to the study of such violent transient events, the main potential future applications of the code are planet/disc interactions, and more generally any configurations where dynamics and collisions are expected to be intricately connected. Accepted by A&A http://arxiv.org/pdf/1308.6502

Radiatively driven Rayleigh-Taylor instabilities around a forming massive star system? NACO adaptive optics and VISIR study of G333.6-0.2 M.S.N. Kumar1 1 Centro de Astrofisica da Universidade do Porto, Portugal E-mail contact: nanda at astro.up.pt The formation of the highest mass stars are thought to be dominated by instabilities resulting from gravitation and radiation. Instabilities due to gravitation are commonly demonstrated by observations of fragmentation, but those due to effects of radiation are thus far not found. Here I report on the NACO adaptive optics and mid-infrared diffraction limited VISIR imaging data of an extemely luminous ultra-compact HII region G333.6-0.2. Two infrared sources, one bright in the near-infrared (appearing point-like) and another in the mid-infrared (resolved with an elliptical shape) are uncovered through this data, located at the heart of this region. These infrared sources appear to be embedded in the waist of a bipolar shaped nebula and UCHII region, the lobes of which are separated by a dark patch. Dense filamentary features with finger/hook morphology are found which appear connected to the two bright infrared sources and the sizes of these hook features are sharply limited to <5000 AU. The observed properties of this target and a large amount of previous data obtained from the literature are together compared with the results of various

30 numerical simulations of high mass star formation. This comparison favours the interpretation that the ﬁnger/hook like structures likely represent radiatively driven Rayleigh-Taylor instabilities arising in the outﬂow cavity of a forming high mass binary star system. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1307.0437

Near-infrared H2 and Continuum Survey of Extended Green Objects. II. Complete Census for the Northern Galactic Plane Hsu-Tai Lee1, Wei-Ting Liao2, Dirk Froebrich3, Jennifer Karr1, Georgios Ioannidis3, Yong-Hyun Lee4, Yu-Nung Su1, Sheng-Yuan Liu1, Hao-Yuan Duan5 and Michihiro Takami1 1 Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan 2 Department of Mechanical Engineering, National Taiwan University, Taiwan 3 Centre for Astrophysics and Planetary Science, University of Kent, Canterbury, CT2 7NH, U.K. 4 Department of Physics and Astronomy, Seoul National University, Seoul 151-742, Republic of Korea 5 Institute of Astronomy and Department of Physics, National Tsing-Hua University, Hsinchu 30013, Taiwan E-mail contact: htlee at illinois.edu We discuss 94 Extended Green Objects (EGOs) in the northern Galactic plane cataloged by Cyganowski et al, based on near-infrared narrowband H2 (2.122 µm) and continuum observations from the United Kingdom Infrared Telescope. This data set is three times larger than our previous study, and is unbiased by preselection. As discussed in the previous paper, the morphologies of the 4.5 µm emission generally resemble those of the near-infrared continuum, but are different from those of the H2 emission. Of our sample, only 28% of EGOs with H2 emission show similar morphologies between 4.5 µm and H2 emission. These results suggest that the 4.5 µm emission mainly comes from scattered continuum from the embedded young stellar object (YSO), and partially from H2 emission. About half of EGOs are associated with H2 outflows, if the H2 outflow incompleteness is considered. The H2 outflow detection rate for EGOs with K-band detections (61%) is significantly higher than for those without K-band detections (36%). This difference may be due to the fact that both H2 and K-band emissions are associated with outflows, i.e., H2 emission and K-band continuum are associated with shocks and outflow cavities, respectively. We also compared the correlation between the H2 outflows and Class I 44 GHz methanol masers from literature. The methanol masers can be located upstream or downstream of the H2 outflows and some bright H2 spots or outflows are not associated with methanol masers, suggesting that methanol masers and H2 emission trace different excitation conditions. Accepted by ApJS http://arxiv.org/pdf/1308.2167

Does Magnetic Field-Rotation Misalignment Solve the Magnetic Braking Catastrophe in Protostellar Disk Formation? Zhi-Yun Li1, Ruben Krasnopolsky2 and Hsien Shang2 1 University of Virginia, Astronomy Department, Charlottesville, USA 2 Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan 3 Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan E-mail contact: zl4h at virginia.edu Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. In the simplest case of a laminar (non-turbulent) core with the magnetic field aligned with the rotation axis, both analytic considerations and numerical simulations have shown that the formation of a large, 102 AU-scale, rotationally supported protostellar disk is suppressed by magnetic braking in the ideal MHD limit for a realistic level of core magnetization. This theoretical difficulty in forming protostellar disks is termed “magnetic braking catastrophe.” A possible resolution to this problem, proposed by Hennebelle and Ciardi (2009) and Joos et al. (2012), is that misalignment between the magnetic field and rotation axis may weaken the magnetic braking enough to enable disk formation. We evaluate this possibility quantitatively through numerical simulations. We confirm the basic result of Joos et al. (2012) that the misalignment is indeed conducive to disk formation. In relatively weakly magnetized cores with dimensionless mass-to-flux ratio

31 greater than about 4, it enabled the formation of rotationally supported disks that would otherwise be suppressed if the magnetic field and rotation axis are aligned. For more strongly magnetized cores, disk formation remains suppressed, however, even for the maximum tilt angle of 90 degrees. If dense cores are as strongly magnetized as indicated by OH Zeeman observations (with a mean dimensionless mass-to-flux ratio of about 2), it would be difficult for the misalignment alone to enable disk formation in the majority of them. We conclude that, while beneficial to disk formation, especially for the relatively weak field case, the misalignment does not completely solve the problem of catastrophic magnetic braking in general. Accepted by ApJ http://www.astro.virginia.edu/~zl4h/TiltPaper.pdf

Characterization of the Young Open Cluster G144.9+0.4 in the Camelopardalis OB1 Association Chien-Cheng Lin1, W.P. Chen1, and Neelam Panwar1 1 Graduate Institute of Astronomy, National Central University 300 Jhongda Rd, Jhongli 32001, Taiwan E-mail contact: cclin at astro.ncu.edu.tw Our star-count analysis of the 2MASS point sources resulted in an identification of the star cluster G144.9+0.4. The cluster was found, but not characterized, by Glushkova et al. (2010). We show that the cluster is physically associated with the Cam OB1 association at a distance of about 1 kpc and with an age of 1–2 Myr. Pre-main sequence stars are identified, on the basis of photometric and proper motion data. A total of 91 additional OB star candidates were found in the subgroup 1A and 1B, a significant increase from the currently known 43 OB stars. The OB members show an age spread that indicates a sustained star formation for at least the last 10–15 years. The young cluster G144.9+0.4 represents the latest episode of sequence star formation in this cloud complex. Accepted by ApJ http://arxiv.org/pdf/1308.6162

+ Gas-phase CO depletion and N2H abundances in starless cores N. Lippok1, R. Launhardt1, D. Semenov1, A.M. Stutz1, Z. Balog1, Th. Henning1, O. Krause1, H. Linz1, M. Nielbock1, Ya.N. Pavlyuchenkov2 , M. Schmalzl3, A. Schmiedeke4, and J.H. Bieging5 1 Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, D-69117 Heidelberg, Germany 2 Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya str. 48, Moscow 119017, Russia 3 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands 4 Universitat zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany 5 Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721, USA E-mail contact: lippok at mpia.de Seven isolated, nearby low-mass starless molecular cloud cores have been observed as part of the Herschel key program Earliest Phases of Star formation (EPoS). By applying a ray-tracing technique to the obtained continuum emission and complementary (sub)mm emission maps, we derive the physical structure (density, dust temperature) of these 12 13 18 + cloud cores. We present observations of the CO, CO, and C O (2–1) and N2H (1–0) transitions towards the same cores. Based on the density and temperature profiles, we apply time-dependent chemical and line-radiative transfer modeling and compare the modeled to the observed molecular emission profiles. CO is frozen onto the grains in the center of all cores in our sample. The level of CO depletion increases with hydrogen density and ranges from 46% up to more than 95% in the core centers in the core centers in the three cores with the highest hydrogen density. The average hydrogen density at which 50% of CO is frozen onto the grains is 1.1±0.4 × 105 cm−3. At about this + density, the cores typically have the highest relative abundance of N2H . The cores with higher central densities show + 5 depletion of N2H at levels of 13% to 55%. The chemical ages for the individual species are on average 2±1 × 10 yr 13 4 18 4 + for CO, 6±3 times 10 yr for C O, and 9±2 × 10 yr for N2H . Chemical modeling suggests that the UV-radiation at the outer boundaries of the cores is weaker than the nominal value; this could be caused by an unresolved outer cold envelope of small dust grains or a weaker than canonically assumed UV-component of the interstellar radiation field (ISRF) itself. We observationally confirm chemical models of CO-freezeout and nitrogen chemistry. We find clear

32 + correlations between the hydrogen density and CO depletion and the emergence of N2H . The chemical ages indicate a core lifetime of less than 1 Myr. Accepted by A&A http://arxiv.org/pdf/1308.2958

A Herschel PACS survey of the dust and gas in Upper Scorpius disks Geoffrey S. Mathews1, Christophe Pinte2, Gaspard Duchêne2,3, Jonathan P. Williams4, Francois Ménard2,5 1 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands 2 CRNS-INSU / UJF-Grenoble 1, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno- ble, F-38041, France 3 Astronomy Department, University of California, Berkeley CA 94720-3411 USA 4 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu HI 96826, USA 5 UMI-FCA (UMI 3386), CNRS/INSU France and Universidad de Chile, Santiago, Chile E-mail contact: gmathews at strw.leidenuniv.nl We present results of far-infrared photometric observations with Herschel PACS of a sample of Upper Scorpius stars, with a detection rate of previously known disk-bearing K and M stars at 70, 100, and 160 µm of 71%, 56%, and 50%, respectively. We fit power-law disk models to the spectral energy distributions of K & M stars with infrared excesses, and have found that while many disks extend in to the sublimation radius, the dust has settled to lower scale heights than in disks of the less evolved Taurus-Auriga population, and have much reduced dust masses. We also conducted Herschel PACS observations for far-infrared line emission and JCMT observations for millimeter CO lines. Among B and A stars, 0 of 5 debris disk hosts exhibit gas line emission, and among K and M stars, only 2 of 14 dusty disk hosts are detected. The OI 63 µm and CII 157 µm lines are detected toward [PZ99] J160421.7-213028 and [PBB2002] J161420.3-190648, which were found in millimeter photometry to host two of the most massive dust disks remaining in the region. Comparison of the OI line emission and 63 µm continuum to that of Taurus sources suggests the emission in the former source is dominated by the disk, while in the other there is a significant contribution from a jet. The low dust masses found by disk modeling and low number of gas line detections suggest that few stars in Upper Scorpius retain sufficient quantities of material for giant planet formation. By the age of Upper Scorpius, giant planet formation is essentially complete. Accepted by A&A http://arxiv.org/pdf/1308.6020

Curved walls: Grain growth, settling, and composition patterns in T Tauri disk dust sublimation fronts Melissa K. McClure1, Paola D’Alessio2, Nuria Calvet1, Catherine Espaillat3, Lee Hartmann1, Ben Sargent4, Dan M. Watson5, Laura Ingleby1 and Jesus Hernandez6 1 University of Michigan, USA 2 Universidad Nacional Autonoma de Mexico, Mexico 3 Harvard-Smithsonian CfA, USA 4 Rochester Institute of Technology, USA 5 University of Rochester, USA 6 CIDA, Canada E-mail contact: melisma at umich.edu The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best-ﬁts to the near- and mid-IR excesses are found for curved, 2-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe)=0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and

33 forsterite grains. As the mass accretion rates decrease from 10−8 to 10−10 Msol/yr, the maximum grain size in the lower layer decreases from 3 to 0.5 microns. We attribute this to a decrease in fragmentation and turbulent support for micron-sized grains with decreasing viscous heating. The atmosphere of these disks is depleted of dust with dust-gas mass ratios 1x10−4 of the ISM value, while the midplane is enhanced to 8 times the ISM value. For all accretion rates, the wall contributes at least half of the ﬂux in the optically thin 10 micron silicate feature. Finally, we ﬁnd evidence for an iron gradient in the disk, suggestive of that found in our solar system. Accepted by ApJ http://adsabs.harvard.edu/pdf/2013arXiv1308.3207M

DIGIT survey of far-infrared lines from protoplanetary discs: II. CO Gwendolyn Meeus1, Colette Salyk2, Simon Bruderer3,4, Davide Fedele3, Koen Maaskant4, Neal J. Evans II5, Ewine F. van Dishoeck3,4, Benjamin Montesinos6, Greg Herczeg7, Jeroen Bouwman8, Joel D. Green5, Carsten Dominik9, Thomas Henning8, Silvia Vicente10, and the DIGIT team 1 Universidad Autonoma de Madrid, Dpt. Fisica Teorica, Campus Cantoblanco, Spain 2 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA 3 Max Planck Institute für Extraterrestriche Physik, Giessenbachstrasse 1, 85748 Garching, Germany 4 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands 5 The University of Texas at Austin, Department of Astronomy, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA 6 Dept. of Astrophysics, CAB (CSIC-INTA), ESAC Campus, P.O. Box 78, 28691 Villanueva de la Cañada, Spain 7 Kavli Institute for Astronomy and Astrophysics, Yi He Yuan Lu 5, Beijing, 100871, P.R. China 8 Max Planck Institute for Astronomy, Königstuhl 17, 69117, Heidelberg, Germany 9 Anton Pannekoek, Amsterdam 10 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands E-mail contact: gwendolyn.meeus at uam.es CO is an important component of a protoplanetary disc as it is one of the most abundant gas phase species. Further- more, observations of the CO transitions can be used as a diagnostic of the gas, tracing conditions in both the inner and outer disc. We present Herschel/PACS spectroscopy of a sample of 22 Herbig Ae/Be (HAEBEs) and 8 T Tauri stars (TTS), covering the pure rotational CO transitions from J = 14–13 up to J = 49–48. CO is detected in only 5 HAEBEs, AB Aur, HD 36112, HD 97048, HD 100546 and IRS 48, and in 4 TTS, AS 205, S CrA, RU Lup, and DG Tau. The highest transition seen is J = 36–35, with Eup of 3669 K, detected in HD 100546 and DG Tau. We construct rotational diagrams for the discs with at least 3 CO detections to derive Trot, and find average temperatures of 270 K for the HAEBEs and 485 K for the TTS. HD 100546 requires an extra temperature component with Trot ∼ 900–1000 K, suggesting a range of temperatures in its disc atmosphere, consistent with thermo-chemical disc models. In HAEBEs, the objects with CO detections all have flared discs in which the gas and dust are thermally decoupled. We use a small model grid to analyse our observations and find that an increased amount of flaring means higher line flux, as it increases the mass in warm gas. CO is not detected in our flat discs as the emission is below the detection limit. We find that HAEBE sources with CO detections have high Luv and strong PAH emission, again connected to the heating of the gas. In TTS, the objects with CO detections are all sources with evidence for a disc wind or outflow. For both groups of objects, sources with CO detections generally have high UV luminosity (either stellar in HAEBEs or due to accretion in TTS), but this is not a sufficient condition for the detection of the far-IR CO lines. Accepted by A&A http://arxiv.org/pdf/1308.4160

Accretion variability of Herbig Ae/Be stars observed by X-Shooter. HD 31648 and HD 163296 I. Mendigutia1, S.D. Brittain1, C. Eiroa2, G. Meeus2, B. Montesinos3, A. Mora4, J. Muzerolle5, R.D. Oudmaijer6, and E. Rigliaco7 1 Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA

34 2 Departamento de F´ısica Teórica, Módulo 15, Facultad de Ciencias, Universidad Autónoma de Madrid, PO Box 28049, Cantoblanco, Madrid, Spain 3 Centro de Astrobiolog´ıa, Departamento de Astrof´ısica (CSIC-INTA), ESAC Campus, P.O. Box 78, 28691 Villanueva de la Cañada, Madrid, Spain 4 GAIA Science Operations Centre, ESA, European Space Astronomy Centre, PO Box 78, 28691, Villanueva de la Canada, Madrid, Spain 5 Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD, 21218, USA 6 School of Physics & Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK 7 Department of Planetary Science, Lunar and Planetary Lab, University of Arizona, 1629, E. University Blvd, 85719, Tucson, AZ, USA E-mail contact: imendig at clemson.edu This work presents X-Shooter/VLT spectra of the prototypical, isolated Herbig Ae stars HD 31648 (MWC 480) and HD 163296 over five epochs separated by timescales ranging from days to months. Each spectrum spans over a wide wavelength range covering from 310 to 2475 nm. We have monitored the continuum excess in the Balmer region of the spectra and the luminosity of twelve ultraviolet, optical and near infrared spectral lines that are commonly used as accretion tracers for T Tauri stars. The observed strengths of the Balmer excesses have been reproduced from a −7 −7 magnetospheric accretion shock model, providing a mean mass accretion rate of 1.11 × 10 and 4.50 × 10 M⊙ yr−1 for HD 31648 and HD 163296, respectively. Accretion rate variations are observed, being more pronounced for HD 31648 (up to 0.5 dex). However, from the comparison with previous results it is found that the accretion rate of HD 163296 has increased by more than 1 dex, on a timescale of ∼ 15 years. Averaged accretion luminosities derived from the Balmer excess are consistent with the ones inferred from the empirical calibrations with the emission line luminosities, indicating that those can be extrapolated to HAe stars. In spite of that, the accretion rate variations do not generally coincide with those estimated from the line luminosities, suggesting that the empirical calibrations are not useful to accurately quantify accretion rate variability. Accepted by ApJ http://arxiv.org/pdf/1308.3248

Reexamination of Induction Heating of Primitive Bodies in Protoplanetary Disks Raymond L. Menzel1 and Wayne G. Roberge1 1 New York Center for Astrobiology and Department of Physics, Applied Physics and Astronomy, Rensselaer Poly- technic Institute, 110 8th Street, Troy, NY 12180, USA E-mail contact: menzer at rpi.edu We reexamine the unipolar induction mechanism for heating asteroids originally proposed in a classic series of papers by Sonett and collaborators. As originally conceived, induction heating is caused by the ”motional electric field” which appears in the frame of an asteroid immersed in a fully-ionized, magnetized solar wind and drives currents through its interior. However we point out that classical induction heating contains a subtle conceptual error, in consequence of which the electric field inside the asteroid was calculated incorrectly. The problem is that the motional electric field used by Sonett et al. is the electric field in the freely streaming plasma far from the asteroid; in fact the motional field vanishes at the asteroid surface for realistic assumptions about the plasma density. In this paper we revisit and improve the induction heating scenario by: (1) correcting the conceptual error by self consistently calculating the electric field in and around the boundary layer at the asteroid-plasma interface; (2) considering weakly-ionized plasmas consistent with current ideas about protoplanetary disks; and (3) considering more realistic scenarios which do not require a fully ionized, powerful T Tauri wind in the disk midplane. We present exemplary solutions for two highly idealized flows which show that the interior electric field can either vanish or be comparable to the fields predicted by classical induction depending on the flow geometry. We term the heating driven by these flows ”electrodynamic heating”, calculate its upper limits, and compare them to heating produced by short-lived radionuclides. Accepted by ApJ http://arxiv.org/pdf/1308.4139

35 Growth and fragmentation of centimetre-sized dust aggregates: the dependence on aggregate size and porosity Farzana Meru1,2, Ralf J. Geretshauser2, Christoph Schaefer2, Roland Speith3 and Wilhelm Kley2 1 Institut für Astronomie, ETH Zürich, Wolfgang-Pauli-Strasse 27, 8093 Zürich, Switzerland 2 Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany 3 Physikalisches Institut, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany E-mail contact: farzana.meru at phys.ethz.ch

We carry out three-dimensional Smoothed Particle Hydrodynamics simulations of spherical homogeneous SiO2 dust aggregates to investigate how the mass and the porosity of the aggregates affects their ability to survive an impact at various different collision velocities (between 1 − 27.5 m/s). We explore how the threshold velocities for fragmentation vary with these parameters. Crucially, we find that the porosity plays a part of utmost importance in determining the outcome of collisions. In particular, we find that aggregates with filling factors ∼>37% are significantly weakened and that the velocity regime in which the aggregates grow is reduced or even non-existent (instead, the aggregates either rebound off each other or break apart). At filling factors less than ≈ 37% we find that more porous objects are weaker but not as weak as highly compact objects with filling factors ∼>37%. In addition we find that (for a given aggregate density) collisions between very different mass objects have higher threshold velocities than those between very similar mass objects. We find that fragmentation velocities are higher than the typical values of 1 m/s and that growth can even occur for velocities as high as 27.5 m/s. Therefore, while the growth of aggregates is more likely if collisions between different sized objects occurs or if the aggregates are porous with filling factor < 37%, it may also be hindered if the aggregates become too compact. Accepted by MNRAS http://arxiv.org/pdf/1308.0825

Waterfalls around protostars: Infall motions towards Class 0/I envelopes as probed by water J.C. Mottram1, E.F. van Dishoeck1,2, M. Schmalzl1, L.E. Kristensen3, R. Visser4, M.R. Hogerheijde1 and S. Bruderer2 1 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands 2 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany 3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 4 Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042, USA E-mail contact: mottram at strw.leidenuniv.nl Context. For stars to form, material must fall inwards from core scales through the envelope towards the central protostar. While theories of how this takes place have been around for some time, the velocity profile around protostars is poorly constrained. The combination of observations in multiple transitions of a tracer which is sensitive to kinematics and radiative transfer modelling of those lines has the potential to break this deadlock. Aims. Seven protostars observed with the Heterodyne Instrument for the Far-Infrared (HIFI) on board the Herschel Space Observatory as part of the “Water in star-forming regions with Herschel” (WISH) survey show infall signatures in water line observations. We aim to constrain the infall velocity and the radii over which infall is taking place within the protostellar envelopes of these sources. We will also use these data to constrain the chemistry of cold water. Methods. We use 1-D non-LTE RATRAN radiative transfer models of the observed water lines to constrain the infall velocity and chemistry in the protostellar envelopes of 6 Class 0 protostars and one Class I source. We assume a free-fall velocity profile and, having found the best fit, vary the radii over which infall takes place. Results. In the well-studied Class 0 protostar NGC1333-IRAS4A we find that infall takes place over the whole envelope to which our observations are sensitive (r∼>1000AU). For L1527, L1157, BHR71 and IRAS15398 infall takes place on core to envelope scales (i.e. ∼10000−3000AU). In Serpens-SMM4 and GSS30 the inverse P-Cygni profiles seen in the ground-state lines are more likely due to larger-scale motions or foreground clouds. Models including a simple consideration of the chemistry are consistent with the observations, while using step abundance profiles are not. The non-detection of excited water in the inner envelope in 6 out of 7 protostars is further evidence that water must be heavily depleted from the gas-phase at these radii.

36 Conclusions. Infall in four of the sources is supersonic and infall in all sources must take place at the outer edge of the envelope, which may be evidence that collapse is global or outside-in rather than inside-out. The mass infall −4 −1 rate in NGC1333-IRAS4A is large (∼>10 M⊙ yr ), higher than the mass outﬂow rate and expected mass accretion rates onto the star, suggesting that any ﬂattened disk-like structure on small scales will be gravitationally unstable, potentially leading to rotational fragmentation and/or episodic accretion. Accepted by Astronomy & Astrophysics http://adsabs.harvard.edu/pdf/2013arXiv1308.5119M

Deuterated molecules in Orion KL from Herschel/HIFI Justin L. Neill1, Nathan R. Crockett1, Edwin A. Bergin1, John C. Pearson2, and Li-Hong Xu3 1 Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109, USA 2 Jet Propulsion Laboratory, Caltech, Pasadena, CA 91109, USA 3 Department of Physics, Centre for Laser, Atomic, and Molecular Studies (CLAMS), University of New Brunswick, Saint John, New Brunswick, Canada E2L 4L5 E-mail contact: jneill at umich.edu We present a comprehensive study of the deuterated molecules detected in the fullband HIFI survey of the Orion KL region. Ammonia, formaldehyde, and methanol and their singly deuterated isotopologues are each detected through numerous transitions in this survey with a wide range in optical depths and excitation conditions. In conjunction with a recent study of the abundance of HDO and H2O in Orion KL, this study yields the best constraints on deuterium fractionation in an interstellar molecular cloud to date. As previous studies have found, both the Hot Core and Compact Ridge regions within Orion KL contain significant abundances of deuterated molecules, suggesting an origin in cold grain mantles. In the Hot Core, we find that ammonia is roughly a factor of 2 more fractionated than water. In the Compact Ridge, meanwhile, we find similar deuterium fractionation in water, formaldehyde, and methanol, with −3 D/H ratios of (2—8) × 10 . The [CH2DOH]/[CH3OD] ratio in the Compact Ridge is found to be 1.2 ± 0.3. The Hot Core generally has lower deuterium fractionation than the Compact Ridge, suggesting a slightly warmer origin, or a greater contribution from warm gas phase chemistry. Accepted by ApJ http://arxiv.org/pdf/1308.5203

New X-ray Selected Pre-Main Sequence Members of the Serpens Molecular Cloud Isa Oliveira1, Margriet van der Laan2 and Joanna M. Brown3 1 UT Austin, USA 2 Leiden Observatory, The Netherlands 3 CfA Harvard, USA E-mail contact: oliveira at astro.as.utexas.edu The study of young stars no longer surrounded by disks can greatly add to our understanding of how protoplanetary disks evolve and planets form. We have used VLT/FLAMES optical spectroscopy to confirm the youth and membership of 19 new young diskless stars in the Serpens Molecular Cloud, identified at X-ray wavelengths. Spectral types, effective temperatures and stellar luminosities were determined using the optical spectra and optical/near-IR photometry. Stellar masses and ages were derived based on PMS evolutionary tracks. The results yield remarkable similarities for age and mass distribution between the diskless and disk-bearing stellar populations in Serpens. We discuss the important implications these similarities may have on the standard picture of disk evolution. Accepted by The Astronomical Journal http://arxiv.org/pdf/1308.2967

Intrinsic Colors, Temperatures and Bolometric Corrections of Pre-main Sequence Stars Mark J. Pecaut1,2 and Eric E. Mamajek1 1 University of Rochester, 500 Wilson Blvd, Rochester, NY 14627, USA

37 2 Rockhurst University, 1100 Rockhurst Road, Kansas City, MO 64110, USA E-mail contact: mark.pecaut at rockhurst.edu We present an analysis of the intrinsic colors and temperatures of 5-30 Myr old pre-main sequence (pre-MS) stars using the F0 through M9 type members of nearby, negligibly reddened groups: η Cha cluster, TW Hydra Association, β Pic Moving Group, and Tucana-Horologium Association. To check the consistency of spectral types from the literature, we estimate new spectral types for 52 nearby pre-MS stars with spectral types F3 through M4 using optical spectra taken with the SMARTS 1.5-m telescope. Combining these new types with published spectral types, and photometry from the literature (Johnson-Cousins BV IC , 2MASS JHKS and WISE W 1, W 2, W 3, and W 4), we derive a new empirical spectral type-color sequence for 5-30 Myr old pre-MS stars. Colors for pre-MS stars match dwarf colors for some spectral types and colors, but for other spectral types and colors, deviations can exceed 0.3 mag. We estimate effective temperatures (Teff ) and bolometric corrections (BCs) for our pre-MS star sample through comparing their photometry to synthetic photometry generated using the BT-Settl grid of model atmosphere spectra. We derive a new Teff and BC scale for pre-MS stars, which should be a more appropriate match for T Tauri stars than often-adopted dwarf star scales. While our new Teff scale for pre-MS stars is within ≃100 K of dwarfs at a given spectral type for stars

Global collapse of molecular clouds as a formation mechanism for the most massive stars Nicolas Peretto1, Gary A. Fuller2, Ana Duarte-Cabral3, Adam Avison2, Patrick Hennebelle4, Jaime E. Pineda2, Philippe Andre4, Sylvain Bontemps2, Frederique Motte4, Nicola Schneider3 and Sergio Molinari5 1 School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK 2 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK 3 Universitéde Bordeaux, LAB, UMR5804, F-33270, Floirac, France 4 Laboratoire AIM, CEA/DSM-CNRS-UniverstéParis Diderot, IRFU/Service d’Astrophysique, C.E. Saclay, France 5 IFSI, INAF, Area di Recerca di Tor Vergata, Via Fosso Cavaliere 100, I-00133, Roma, Italy E-mail contact: nicolas.peretto at astro.cf.ac.uk The relative importance of primordial molecular cloud fragmentation versus large-scale accretion still remains to be assessed in the context of massive core/star formation. Studying the kinematics of the dense gas surrounding massive- star progenitors can tell us the extent to which large-scale flow of material impacts the growth in mass of star-forming cores. Here we present a comprehensive dataset of the 5500(±800) M⊙ infrared dark cloud SDC335.579-0.272 (hereafter SDC335) which exhibits a network of cold, dense, parsec-long filaments. Atacama Large Millimeter Array (ALMA) Cycle 0 observations reveal two massive star-forming cores, MM1 and MM2, sitting at the centre of SDC335 where the +770 filaments intersect. With a gas mass of 545(−385) M⊙ contained within a source diameter of 0.05 pc, MM1 is one of the most massive, compact protostellar cores ever observed in the Galaxy. As a whole, SDC335 could potentially form an OB cluster similar to the Trapezium cluster in Orion. ALMA and Mopra single-dish observations of the SDC335 dense gas furthermore reveal that the kinematics of this hub-filament system are consistent with a global collapse of the cloud. These molecular-line data point towards an infall velocity Vinf = 0.7(±0.2) km/s, and a total mass −3 −1 infall rate M˙ inf ≃ 2.5(±1.0) × 10 M⊙ yr towards the central pc-size region of SDC335. This infall rate brings 5 750(±300) M⊙ of gas to the centre of the cloud per free-fall time (tff = 3 × 10 yr). This is enough to double the +2.2 mass already present in the central pc-size region in 3.5−1.0 × tff . These values suggest that the global collapse of SDC335 over the past million year resulted in the formation of an early O-type star progenitor at the centre of the cloud’s gravitational potential well. Accepted by A&A

38 The expansion of massive young star clusters - observation meets theory Susanne Pfalzner1 and Thomas Kaczmarek1 1 Max-Planck-Institut für Radioastronomie, 53121 Bonn Germany E-mail contact: spfalzner at mpifr.de Most stars form as part of a star cluster. The most massive clusters in the Milky Way exist in two groups - loose and compact clusters - with significantly different sizes at the end of the star formation process. After their formation both types of clusters expand up to a factor 10-20 within the first 20 Myr. Gas expulsion at the end of the star formation process is usually regarded as only possible process that can lead to such an expansion. We investigate the effect of gas expulsion by a direct comparison between numerical models and observed clusters concentrating on 3 clusters with masses >10 M⊙. For these clusters the initial conditions before gas expulsion, the characteristic cluster development, its dependence on cluster mass, and the star formation efficiency (SFE) are investigated. We perform N-body simulations of the cluster expansion process after gas expulsion and compare the results with observations. We find that the expansion processes of the observed loose and compact massive clusters are driven by completely different physical processes. As expected the expansion of loose massive clusters is largely driven by the gas loss due to the low SFE of ∼30%. One new revelation is that all the observed massive clusters of this group seem to have a very similar size of 1-3 pc at the onset of expansion. It is demonstrated that compact clusters have a much higher effective SFE of 60-70% and are as a result much less affected by gas expulsion. Their expansion is mainly driven by stellar ejections caused by interactions between the cluster members. The reason why ejections are so efficient in driving cluster expansion is that they occur dominantly from the cluster centre and over an extended period of time. Thus during the first 10 Myr the internal dynamics of loose and compact clusters differ fundamentally. Accepted by A&A http://arxiv.org/pdf/1309.0315

Making giant planet cores: convergent migration and growth of planetary embryos in non-isothermal discs A. Pierens1,2, C. Cossou1,2, and S.N. Raymond1,2 1 Universitéde Bordeaux, Observatoire Aquitain des Sciences de l’Univers, BP89 33271 Floirac Cedex, France 2 Laboratoire d’Astrophysique de Bordeaux, BP89 33271 Floirac Cedex, France E-mail contact: arnaud.pierens at obs.u-bordeaux1.fr Earth-mass bodies are expected to undergo Type I migration directed either inward or outward depending on the thermodynamical state of the protoplanetary disc. Zones of convergent migration exist where the Type I torque cancels out. We study the evolution of multiple protoplanets of a few Earth masses embedded in a non-isothermal protoplanetary disc. The protoplanets are located in the vicinity of a convergence zone located at the transition between two different opacity regimes. Inside the convergence zone, Type I migration is directed outward and outside the zone migration is directed inward. We used a grid-based hydrodynamical code that includes radiative effects. We performed simulations varying the initial number of embryos and tested the effect of including stochastic forces to mimic the effects resulting from turbulence. We also performed N-body runs calibrated on hydrodynamical calculations to follow the evolution on Myr timescales. For a small number of initial embryos (N = 5–7) and in the absence of stochastic forcing, the population of protoplanets migrates convergently toward the zero-torque radius and forms a stable resonant chain that protects embryos from close encounters. In systems with a larger initial number of embryos, or in which stochastic forces were included, these resonant configurations are disrupted. This in turn leads to the growth of larger cores via a phase of giant impacts, after which the system settles to a new stable resonant configuration. Giant planets cores with masses of 10 M⊕ formed in about half of the simulations with initial protoplanet masses of mp = 3 M⊕ but in only 15% of simulations with mp = 1 M⊕. This suggests that if ∼2–3 M⊕ protoplanets can form in less than ∼1 Myr, convergent migration and giant collisions can grow giant planet cores at Type I migration convergence zones. Accepted by A&A http://arxiv.org/pdf/1308.2596

39 Evidence for past knot mergers in the HH34 jet A. C. Raga1 and A. Noriega-Crespo2 1 Instituto de Ciencias Nucleares, UNAM, Ap. 70-543, D.F., México 2 Spitzer Science Center, California Institute of Technology, CA 91125, USA E-mail contact: raga at nucleares.unam.mx Within ∼ 30′′ from the outflow source, the HH 34 jet has a chain of well aligned knots. The positions and proper motions of these knots can be used to determine dynamical timescales, and estimates of the ejection period (by taking differences between the dynamical timescales of the successive knots). Through this exercise, we find that larger estimated ejection periods are found for the knots further away from the outflow source (i.e., for the knots with larger dynamical timescales). We interpret this result in terms of a model in which the knots have a low amplitude (∼ 15-20%) random ejection velocity variability and a well defined period of ≈ 16 yr, leading to a few knot-merging events. Accepted by RMxAA http://www.nucleares.unam.mx/astroplasmas/images/stories/pdf/hh34-mergers.pdf

APEX/SABOCA observations of small-scale structure of infrared-dark clouds I. Early evolutionary stages of star-forming cores Sarah E. Ragan1, Thomas Henning1 and Henrik Beuther1 1 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany E-mail contact: ragan at mpia.de Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass star formation and are comprised of cold (∼20 K), dense (n > 104 cm−3) gas. The spectral energy distribution (SED) of IRDCs is dominated by the far-infrared and millimeter wavelength regime, and our initial Herschel study examined IRDCs at the peak of the SED with high angular resolution. Here we present a follow-up study using the SABOCA instrument on APEX which delivers 7.8′′ angular resolution at 350 µm, matching the resolution we achieved with Herschel/PACS, and allowing us to characterize substructure on ∼0.1 pc scales. Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies, and the filamentary clouds show significant hierarchical structure, while the clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of morphology, have about 14% of their total mass in small scale core- like structures which roughly follow a trend of constant volume density over all size scales. Out of the 89 protostellar cores we identified in this sample with Herschel, we recover 40 of the brightest and re-fit their SEDs and find their properties agree fairly well with our previous estimates (∼ 19K). We detect a new population of “cold cores” which have no 70 µm counterpart, but are 100 and 160 µm-bright, with colder temperatures (∼ 16 K). This latter population, along with SABOCA-only detections, are predominantly low-mass objects, but their evolutionary diagnostics are consistent with the earliest starless or prestellar phase of cores in IRDCs. Accepted by Astronomy & Astrophysics http://arxiv.org/pdf/1308.6157

Unified Models of Molecular Emission from Class 0 Protostellar Outflow Sources J.M.C. Rawlings1, M.P. Redman2, and P.B. Carolan2 1 University College London, Department of Physics and Astronomy, Gower Street, London WC1E 6BT, United Kingdom 2 Centre for Astronomy, School of Physics, National University of Ireland Galway, Galway, Ireland E-mail contact: jcr at star.ucl.ac.uk Low mass star-forming regions are more complex than the simple spherically symmetric approximation that is often assumed. We apply a more realistic infall/outflow physical model to molecular/continuum observations of three late Class 0 protostellar sources with the aims of (a) proving the applicability of a single physical model for all three sources, and (b) deriving physical parameters for the molecular gas component in each of the sources.

40 We have observed several molecular species in multiple rotational transitions. The observed line profiles were modelled in the context of a dynamical model which incorporates infall and bipolar outflows, using a three dimensional radiative transfer code. This results in constraints on the physical parameters and chemical abundances in each source. Self-consistent fits to each source are obtained. We constrain the characteristics of the molecular gas in the envelopes as well as in the molecular outflows. We find that the molecular gas abundances in the infalling envelope are reduced, presumably due to freeze-out, whilst the abundances in the molecular outflows are enhanced, presumably due to dynamical activity. Despite the fact that the line profiles show significant source-to-source variation, which primarily derives from variations in the outflow viewing angle, the physical parameters of the gas are found to be similar in each core. Accepted by MNRAS http://arxiv.org/pdf/1308.5111

Occultation of the T Tauri Star RW Aurigae A by its Tidally Disrupted Disk Joseph E. Rodriguez1,2, Joshua Pepper3,2, Keivan G. Stassun2,1, Robert J. Siverd2, Phillip Cargile2, Thomas G. Beatty4, B. Scott Gaudi4 1 Department of Physics, Fisk University, 1000 17th Avenue North, Nashville, TN 37208, USA 2 Department of Physics and Astronomy, Vanderbilt University, 6301 Stevenson Center, Nashville, TN 37235, USA 3 Department of Physics, Lehigh University, 16 Memorial Drive East, Bethlehem, PA 18015, USA 4 Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA E-mail contact: joseph.e.rodriguez at vanderbilt.edu RW Aur A is a classical T Tauri star, believed to have undergone a reconfiguration of its circumstellar environment as a consequence of a recent fly-by of its stellar companion, RW Aur B. This interaction stripped away part of the circumstellar disk of RW Aur A, leaving a tidally disrupted arm and a short truncated circumstellar disk. We present photometric observations of the RW Aur system from the Kilodegree Extremely Little Telescope (KELT) survey showing a long and deep dimming that occurred from September 2010 until March 2011. The dimming has a depth of ∼2 magnitudes, a duration of ∼180 days and was confirmed by archival observations from American Association of Variable Star Observers (AAVSO). We suggest that this event is the result of a portion of the tidally disrupted disk occulting RW Aur A, specifically a fragment of the tidally disrupted arm. The calculated transverse linear velocity of the occulter is in excellent agreement with the measured relative radial velocity of the tidally disrupted arm. Using simple kinematic and geometric arguments, we show that the occulter cannot be a feature of the RW Aur A circumstellar disk, and we consider and discount other hypotheses. We also place constraints on the thickness and semi-major axis of the portion of the arm that occulted the star. Accepted by AJ http://arxiv.org/pdf/1308.2017

The Structure of the Evolved Circumbinary Disk around V4046 Sgr Katherine A. Rosenfeld1, Sean M. Andrews1, David J. Wilner1, J.H. Kastner2, and M.K. McClure3 1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 2 Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA 3 Department of Astronomy, University of Michigan, 830 Dennison Bldg, 500 Church Street, Ann Arbor, MI 48109, USA E-mail contact: krosenfeld at cfa.harvard.edu We present sensitive, sub-arcsecond resolution Submillimeter Array observations of the protoplanetary disk around the nearby, pre-main sequence spectroscopic binary V4046 Sgr. We report for the ﬁrst time a large inner hole (r = 29 AU) spatially resolved in the 1.3 mm continuum emission and study the structure of this disk using radiative transfer calculations to model the spectral energy distribution (SED), continuum visibilities, and spectral line emission of CO and its main isotopologues. Our modeling scheme demonstrates that the majority of the dust mass is distributed in a narrow ring (centered at 37 AU with a FWHM of 16 AU) that is ∼5 times more compact than the gas disk. This structure implies that the dust-to-gas mass ratio has a strong spatial variation, ranging from a value much larger

41 than typical of the interstellar medium (ISM) at the ring to much smaller than that of the ISM at larger disk radii. We suggest that these basic structural features are potentially observational signatures of the accumulation of solids at a local gas pressure maximum. These models also require a substantial population of ∼micron-sized grains inside the central disk cavity. We suggest that this structure is likely the result of dynamical interactions with a low-mass companion, although photoevaporation may also play a secondary role. Accepted by ApJ http://arxiv.org/pdf/1308.4358

[Fe II] 1.64 µm Features of Jets and Outflows from Young Stellar Objects in the Carina Nebula Jong-Ho Shinn1, Tae-Soo Pyo2, Jae-Joon Lee1, Ho-Gyu Lee3, Hyun-Jeong Kim4, Bon-Chul Koo4, Hwankyung Sung5, Moo Young Chun1, A.-Ran Lyo1, Dae-Sik Moon1,6, Jaemann Kyeong1, Byeong- Gon Park1, Hyeonoh Hur5 and Yong-Hyun Lee4 1 Korea Astronomy and Space Science Institute, Korea 2 National Astronomical Observatory of Japan, Japan 3 the University of Tokyo, Japan 4 Seoul National University, Korea 5 Sejong University, Korea 6 University of Toronto, Canada E-mail contact: jhshinn at kasi.re.kr We present [Fe II] 1.64 µm imaging observations for jets and outflows from young stellar objects (YSOs) over the northern part (∼ 24′ × 45′) of the Carina Nebula, a massive star forming region. The observations were performed with IRIS2 of Anglo-Australian Telescope and the seeing was ∼ 1.5′′ ± 0.5′′. Eleven jet and outflow features are detected at eight different regions, and are named as Ionized Fe Objects (IFOs). One Herbig-Haro object candidate missed in Hubble Space Telescope Hα observations is newly identified as HHc-16, referring our [Fe II] images. IFOs have knotty or longish shapes, and the detection rate of IFOs against previously identified YSOs is 1.4 %, which should be treated as a lower limit. Four IFOs show an anti-correlated peak intensities in [Fe II] and Hα, where the ratio I([Fe II])/I(Hα) is higher for longish IFOs than for knotty IFOs. We estimate the outflow mass loss rate from the [Fe II] flux, using two different methods. The jet-driving objects are identified for three IFOs (IFO-2, -4, and -7), for which we study the relations between the outflow mass loss rate and the YSO physical parameters from the radiative transfer model fitting. The ratios of the outflow mass loss rate over the disk accretion rate are consistent for IFO-4 and -7 with the previously reported values (10−2 − 10+1), while it is higher for IFO-2. This excess may be from the underestimation of the disk accretion rate. The jet-driving objects are likely to be low- or intermediate-mass stars. Other YSO physical parameters, such as luminosity and age, show reasonable relations or trends. Accepted by Astrophysical Journal http://arxiv.org/pdf/1308.3003

The Bolocam Galactic Plane Survey. X. A Complete Spectroscopic Catalog of Dense Molecular Gas Observed toward 1.1 mm Dust Continuum Sources with 7.5◦ ≤ l ≤ 194◦ Yancy L. Shirley1,2, Timothy P. Ellsworth-Bowers3, Brian Svoboda1, Wayne M. Schlingman3, Adam Ginsburg3, Erik Rosolowsky4, Thomas Gerner5, Steven Mairs6, Cara Battersby3, Guy Stringfellow3, Miranda K. Dunham7, Jason Glenn3, and John Bally3 1 Steward Observatory, 933 N Cherry Ave., Tucson, AZ 85721 USA 2 Adjunct Astronomer, The National Radio Astronomy Observatory 3 CASA, University of Colorado, CB 389, Boulder, CO 80309, USA 4 Department of Physics, University of Alberta, 4-181 CCIS Edmonton AB T6G 2E1, Canada 5 Max-Planck-Institut f¨ur Astronomie (MPIA), Knigstuhl 17, 69117, Heidelberg, Germany 6 Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6, Canada 7 Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520, USA

42 E-mail contact: yshirley at as.arizona.edu The Bolocam Galactic Plane Survey (BGPS) is a 1.1 mm continuum survey of dense clumps of dust throughout the Galaxy covering 170 square degrees. We present spectroscopic observations using the Heinrich Hertz Submillimeter + + Telescope of the dense gas tracers, HCO and N2H 3–2, for all 6194 sources in the Bolocam Galactic Plane Survey v1.0.1 catalog between 7.5◦ ≤ l ≤ 194◦. This is the largest targeted spectroscopic survey of dense molecular gas in the + Milky Way to date. We find unique velocities for 3126 (50.5%) of the BGPS v1.0.1 sources observed. Strong N2H + 3–2 emission (Tmb > 0.5 K) without HCO 3–2 emission does not occur in this catalog. We characterize the properties of the dense molecular gas emission toward the entire sample. HCO+ is very sub-thermally populated and the 3–2 transitions are optically thick toward most BGPS clumps. The median observed line width is 3.3 km s−1 consistent with supersonic turbulence within BGPS clumps. We find strong correlations between dense molecular gas integrated intensities and 1.1 mm peak flux and the gas kinetic temperature derived from previously published NH3 observations. These intensity correlations are driven by the sensitivity of the 3–2 transitions to excitation conditions rather than by + variations in molecular column density or abundance. We identify a subset of 113 sources with stronger N2H than + + + HCO integrated intensity, but we find no correlations between the N2H / HCO ratio and 1.1 mm continuum flux density, gas kinetic temperature, or line width. Self-absorbed profiles are rare (1.3%). Accepted by ApJS http://arxiv.org/pdf/1308.4149

Dust in the diffuse interstellar medium: Extinction, emission, linear and circular polarisation R. Siebenmorgen1, N.V. Voshchinnikov2 and S. Bagnulo3 1 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching b. München, Germany 2 Sobolev Astronomical Institute, St. Petersburg University, Universitetskii prosp. 28, St. Petersburg, 198504 Russia 3 Armagh Observatory, College Hill, Armagh BT61 9DG, UK E-mail contact: Ralf.Siebenmorgen at eso.org We present a model for the diffuse interstellar dust that explains the observed wavelength-dependence of extinction, emission, linear and circular polarisation of light. The model is set-up with a small number of parameters. It consists of a mixture of amorphous carbon and silicate grains with sizes from the molecular domain of 0.5 up to about 500 nm. Dust grains with radii larger than 6 nm are spheroids. Spheroidal dust particles have a factor 1.5 – 3 larger absorption cross section in the far IR than spherical grains of the same volume. Mass estimates derived from submillimeter observations that ignore this effect are overestimated by the same amount. In the presence of a magnetic field, spheroids may be partly aligned and polarise light. We find that polarisation spectra help to determine the upper particle radius of the otherwise rather unconstrained dust size distribution. Stochastically heated small grains of graphite, silicates and polycyclic aromatic hydrocarbons (PAHs) are included. We tabulate parameters for PAH emission bands in various environments. They show a trend with the hardness of the radiation field that can be explained by the ionisation state or hydrogenation coverage of the molecules. For each dust component its relative weight is specified, so that absolute element abundances are not direct input parameters. The model is confronted with the average properties of the Milky Way, which seems to represent dust in the solar neighbourhood. It is then applied to specific sight lines towards four particular stars one of them is located in the reflection nebula NGC 2023. For these sight lines, we present ultra-high signal-to-noise linear and circular spectro-polarimetric observations obtained with FORS at the VLT. Using prolate rather than oblate grains gives a better fit to observed spectra; the axial ratio of the spheroids is typically two and aligned silicates are the dominant contributor to the polarisation. Accepted by A&A http://www.eso.org/~rsiebenm/FTP/RSiebenmorgenDust.pdf http://arxiv.org/pdf/1308.3148

Extensive [CI] Mapping toward the Orion-A Giant Molecular Cloud Yoshito Shimajiri1,2,3, Takeshi Sakai4,5, Takashi Tsukagoshi6, Yoshimi Kitamura7, Munetake Momose6, Masao Saito2,8, Tai Oshima1,2, Kotaro Kohno4,9 and Ryohei Kawabe1,2,8 1 Nobeyama Radio Observatory, 462-2 Nobeyama Minamimaki, Minamisaku District, Nagano Prefecture 384-1305,

43 Japan 2 National Astronomical Observatory of Japan, 2-21-1 Osawa Mitaka, Tokyo 181-0015, Japan 3 Laboratoire AIM, CEA/DSM-CNRS-Universitacutee Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay, F-91191 Gif-sur-Yvette, France 4 Institute of Astronomy, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan 5 Graduate School of Informatics and Engineering, The University of Electro-Communications, Chofu, Tokyo 182- 8585, Japan 6 Ibaraki University, 2-1-1 Bunkyo Mito, Ibaraki Prefecture 310-8512, Japan 7 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210, Japan 8 Joint ALMA Observatory, Alonso de Cordova 3107 Vitacura, Santiago 763 0355, Chile 9 Research Center for the Early Universe, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan E-mail contact: Yoshito.Shimajiri at cea.fr We have carried out wide-ﬁeld (0.17 degree2) and high-angular resolution (21.3arcsec sim 0.04 pc) observations in [CI] line toward the Orion-A giant molecular cloud with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope in the On-The-Fly (OTF) mode. Overall features of the [CI] emission are similar to those of the 12CO (J=1–0) emission in Shimajiri et al. (2011); the total intensity ratio of the [CI] to CO emission ranges from 0.05 to 0.2. The optical depth of the [CI] emission is found to be 0.1 – 0.75, suggesting optically thin emission. The column density of the [CI] emission is estimated to be (1.0 – 19) times 1017 cm−2. These results are consistent with the results of the previous [CI] observations with a low-angular resolution of 2.2arcmin (e.g. Ikeda et al. 1999). In the nearly edge-on PDRs and their candidates of the Orion Bar, DLSF, M 43 Shell, and Region D, the distributions of the [CI] emission coincide with those of the 12CO emission, inconsistent with the prediction by the plane-parallel PDR model (Hollenbach & Tielens 1999). In addition, the [CI] distribution in the Orion A cloud is found to be more similar to those of the 13CO (J=1–0), C18O (J=1–0), and H13CO+ (J=1–0) lines than that of the 12CO (J=1–0) line, suggesting that the [CI] emission is not limited to the cloud surface, but is tracing the dense, inner parts of the cloud. Accepted by ApJL http://arxiv.org/pdf/1308.1036

X-Shooter spectroscopy of young stellar objects. III. Photospheric and chromospheric properties of Class III objects B. Stelzer1, A. Frasca2, J.M. Alcala3, C.F. Manara4, K. Biazzo3,2, E. Covino3, E. Rigliaco5, L. Testi4, S. Covino6 and V. D’Elia7 1 INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy 2 INAF, Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy 3 INAF, Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy 4 European Southern Observatory, Karl-Schwarzschild-Str.2, 85748 Garching, Germany 5 Department of Planetary Science, Lunar and Planetary Lab, University of Arizona, 1629 E. University Blvd, 85719 Tucson, USA 6 INAF, Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy 7 INAF, Osservatorio Astronomico di Roma, Via di Frascati 33, 00040 Monte Porzio Catone, Italy E-mail contact: stelzer at astropa.inaf.it We have analyzed X-Shooter/VLT spectra of 24 Class III sources from three nearby star forming regions (σOrionis, Lupus III, TW Hya). We have determined the effective temperature, surface gravity, rotational velocity and radial velocity by comparison of the observed spectra to synthetic BT-Settl model spectra. We have investigated in detail the emission lines emerging from the stellar chromospheres and combined these data with archival X-ray data to allow for a comparison between chromospheric and coronal emissions. For some objects in the sample the atmospheric and kinematic parameters are here presented for the first time. Small differences in the surface gravity found between the stars can be attributed to differences in the average age of the three star forming regions. The strength of lithium absorption and radial velocities confirm the young age of all but one object in the sample (Sz 94). Both X-ray and Hα luminosity as measured in terms of the bolometric luminosity are independent on effective temperature for early-M

44 stars but decline towards the end of the spectral M sequence. For the saturated early-M stars the average emission level is almost one dex larger for X-rays with respect to Hα: log (Lx/Lbol)= −2.85±0.36 vs. log (LHα/Lbol)= −3.72±0.21. When all chromospheric emission lines (including the Balmer series up to H11, CaII HK, CaII infrared triplet and several He I lines) are summed up the coronal flux still dominates that of the chromosphere, typically by a factor 2 − 5. Flux-flux relations between activity diagnostics that probe different atmospheric layers (from the lower chromosphere up to the corona) separate our sample of active pre-main sequence stars from the bulk of field M dwarfs studied in the literature. Flux ratios between individual optical emission lines show a smooth dependence with effective temperature. The Balmer decrements can roughly be reproduced by a NLTE radiative transfer model devised for another young star of similar age. Future, more complete chromospheric model grids can be tested against this data set. Accepted by Astronomy & Astrophysics http://www.astropa.unipa.it/$\sim$stelzer/publications.html http://arxiv.org/pdf/1308.5563

A New Hα Emission-Line Survey in the Orion Nebula Cluster E. Szegedi-Elek1 M. Kun1, B. Reipurth2, A. Pál1, L.G. Balázs1, M. Willman2 1 Konkoly Observatory, H-1121 Budapest, Konkoly Thege út 15-17, Hungary 2 Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI 96720, USA E-mail contact: eelza at konkoly.hu We present results from an Hα emission-line survey in a one square degree area centered on the Orion Nebula Cluster, obtained with the Wide Field Grism Spectrograph-2 on the 2.2-meter telescope of the University of Hawaii. We identified 587 stars with Hα emission, 99 of which, located mainly in the outer regions of the observed area, have not appeared in previous Hα surveys. We determined the equivalent width (EW) of the line, and based on it classified 372 stars as classical T Tauri stars (CTTS) and 187 as weak line T Tauri stars (WTTS). Simultaneous r’, i’ photometry indicates a limiting magnitude of r’ ∼ 20 mag, but the sample is incomplete at r’ > 17 mag. The surface distribution of the Hα emission stars reveals a clustered and a dispersed population, the former consisting of younger and more massive young stars than the latter. Comparison of the derived EWs with those found in the literature indicates variability of the Hα line. We found that the typical amplitudes of the variability are not greater than a factor 2-3 in the most cases. We identified a subgroup of low-EW stars with infrared signatures indicative of optically thick accretion disks. We studied the correlations between the equivalent width and other properties of the stars. Based on literature data we examined several properties of our CTTS and WTTS subsamples and found significant differences in mid-infrared color indices, average rotational periods, and spectral energy distribution characteristics of the subsamples. Accepted by ApJS http://arxiv.org/pdf/1308.1812

Evidence for Infalling Gas of Low Angular Momentum towards the L1551 NE Keplerian Circumbinary Disk Shigehisa Takakuwa1, Masao Saito2, Jeremy Lim3 and Kazuya Saigo4 1 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan 2 Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago, Chile 3 Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong 4 ALMA Project Office, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan E-mail contact: takakuwa at asiaa.sinica.edu.tw We report follow-up observations of the Class I binary protostellar system L1551 NE in the C18O (3–2) line with the SMA in its compact and subcompact configurations. Our previous observations at a higher angular resolution in the extended configuration revealed a circumbinary disk exhibiting Keplerian motion. The combined data having more extensive spatial coverage (∼140–2000 AU) verify the presence of a Keplerian circumbinary disk, and reveals for −1 the first time a distinct low-velocity (∼<±0.5 km s from the systemic velocity) component that displays a velocity gradient along the minor axis of the circumbinary disk. Our simple model that reproduces the main features seen in the Position-Velocity diagrams comprises a circumbinary disk exhibiting Keplerian motion out to a radius of ∼300 AU,

45 beyond which the gas exhibits pure infall at a constant velocity of ∼0.6 km s−1. The latter is significantly smaller −1 than the expected free-fall velocity of ∼2.2 km s onto the L1551 NE protostellar mass of ∼0.8 M⊙ at ∼300 AU, suggesting that the infalling gas is decelerated as it moves into regions of high gas pressure in the circumbinary disk. The discontinuity in angular momenta between the outer infalling gas and inner Keplerian circumbinary disk implies an abrupt transition in the effectiveness at which magnetic braking is able to transfer angular momentum outwards, a result perhaps of the different plasma β’s and ionization fractions between the outer and inner regions of the circumbinary disk. Accepted by ApJ http://arxiv.org/pdf/1308.2054

G10.472+0.027: An Extreme water maser outﬂow associated with a Massive Protostel- lar Cluster A.M. Titmarsh1,2, S.P. Ellingsen1, S.L. Breen2, J.L. Caswell2, M.A. Voronkov2 1 School of Mathematics and Physics, University of Tasmania, Hobart, Tasmania, Australia 2 CSIRO Astronomy and Space Science, Australia Telescope National Facility, PO Box 76 Epping, NSW 1710, Australia E-mail contact: Simon.Ellingsen at utas.edu.au An Australia Telescope Compact Array search for 22 GHz water masers towards 6.7 GHz class II methanol masers detected in the Methanol Multibeam (MMB) survey has resulted in the detection of extremely high velocity emission from one of the sources. The water maser emission associated with this young stellar object covers a velocity span of nearly 300 km s−1. The highest velocity water maser emission is red-shifted from the systemic velocity by 250 km s−1, which is a new record for high-mass star formation regions. The maser is associated with a very young late O, or early B star, which may still be actively accreting matter (and driving the extreme outﬂow). If that is the case future observations of the kinematics of this water maser will provide a unique probe of accretion processes in the highest mass young stellar objects and test models of water maser formation. Accepted by ApJL http://arxiv.org/pdf/1308.4167

Constraints on the radial distribution of the dust properties in the CQ Tau protoplanetary disk F. Trotta1,2,3,4, L. Testi3,4,5, A. Natta3,6, A. Isella7 and L. Ricci7 1 Department of Physics and Astronomy, University of Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy 2 Dipartimento di Fisica e Astrofisica, Universitádegli Studi di Firenze, Largo E. Fermi 2, 50125 Firenze, Italy 3 INAF - Osservatorio astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 4 ESO, Karl Schwarzschild str. 2, D-85748 Garching bei Muenchen, Germany 5 Excellence Cluster Universe, Boltzmannstr. 2, D-85748, Garching, Germany 6 Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2, Ireland 7 Division of Physics, Mathematics and Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA E-mail contact: ltesti at eso.org Grain growth in protoplanetary disks is the first step towards the formation of the rocky cores of planets. Models predict that grains grow, migrate, and fragment in the disk and predict varying dust properties as a function of radius, age, and physical properties. High-angular resolution observations at more than one (sub-)mm wavelength are the essential tool for constraining grain growth and migration on the disk midplane. We developed a procedure to analyze self-consistently multi wavelength (sub-)mm continuum interferometric observations of protoplanetary disks to constrain the radial distribution of dust properties. We apply this technique to existing multi frequency continuum mm observations of the disk around CQ Tau, a A8 pre-main sequence star with a well-studied disk. We demonstrate that our models can be used to simultaneously constrain the disk and dust structure. In CQ Tau, the best-fitting model has a radial dependence of the maximum grain size, which decreases from a few cm in the inner disk (< 40 AU) to a few mm at 80 AU. Nevertheless, the currently available dataset does not allow us to exclude the possibility of a

46 uniform grain size distribution at a 3σ level. Accepted by Astronomy and Astrophysics http://arxiv.org/pdf/1308.5070

Dense molecular cocoons in the massive protocluster W3 IRS5: a test case for models of massive star formation K.-S. Wang1, T.L. Bourke2, M.R. Hogerheijde1, F.F.S. van der Tak3,4, A.O. Benz5, S.T. Megeath6, and T.L. Wilson7 1 UPS-Toulouse / CNRS-INSU, Institut de Recherche en Astrophysique et Planétologie (IRAP) UMR 5277, Toulouse, F31400 France 2 School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Scotland KY16 9SS, UK 3 Departamento de F´ısica – ICEx – UFMG, Av. Antônio Carlos, 6627, 30270-901 Belo Horizonte, MG, Brazil 4 ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany 5 UJF-Grenoble 1 / CNRS-INSU, Institut de Plantologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, F-38041, France 6 UMI-FCA, CNRS/INSU, France (UMI 3386), and Universidad de Chile, Santiago, Chile 7 Department of Astronomy, Cornell University, Ithaca, NY 14853-6801, USA E-mail contact: kswang at strw.leidenuniv.nl Context. Two competing models describe the formation of massive stars in objects like the Orion Trapezium. In the turbulent core accretion model, the resulting stellar masses are directly related to the mass distribution of the cloud condensations. In the competitive accretion model, the gravitational potential of the protocluster captures gas from the surrounding cloud for which the individual cluster members compete. Aims. With high resolution submillimeter observations of the structure, kinematics, and chemistry of the proto- Trapezium cluster W3 IRS5, we aim to determine which mode of star formation dominates. Methods. We present 354 GHz Submillimeter Array observations at resolutions of 1′′–3′′ (1800–5400 AU) of W3 IRS5. Results. The observations show five emission peaks (SMM1–5). SMM1 and SMM2 contain massive embedded stars 7 −3 (∼20 M⊙); SMM3–5 are starless or contain low-mass stars (<8 M⊙). The inferred densities are high, ≥ 10 cm , but the core masses are small, 0.2–0.6 M⊙. The detected molecular emission reveals four different chemical zones. Conclusions. The proto-Trapezium cluster W3 IRS5 is an ideal test case to discriminate between models of massive star formation. Either the massive stars accrete locally from their local cores; in this case the small core masses imply that W3 IRS5 is at the very end stages (1000 yr) of infall and accretion, or the stars are accreting from the global collapse of a massive, cluster forming core. We find that the observed masses, densities and line widths observed toward W3 IRS 5 and the surrounding cluster forming core are consistent with the competitive accretion of gas at −4 −1 rates of M˙ ∼ 10 M⊙ yr by the massive young forming stars. Accepted by A&A http://arxiv.org/pdf/1308.5151

3-D Radiation Transfer in Young Stellar Objects B.A. Whitney1, T.P. Robitaille2, J.E. Bjorkman3, R. Dong4, M.J. Wolﬀ5, K. Wood6 and J. Honor1 1 University of Wisconsin, USA 2 Max-Planck-Institute for Astronomy, Germany 3 University of Toledo, USA 4 Princeton University, USA 5 Space Science Institute, USA 6 University of St. Andrews, UK E-mail contact: bwhitney at astro.wisc.edu We have updated our publicly available dust radiative transfer code (HOCHUNK3D) to include new emission processes and various 3-D geometries appropriate for forming stars. The 3-D geometries include warps and spirals in disks, accretion hotspots on the central star, fractal clumping density enhancements, and misaligned inner disks. Additional

47 axisymmetric (2-D) features include gaps in disks and envelopes, ”puffed-up inner rims” in disks, multiple bipolar cavity walls, and iteration of disk vertical structure assuming hydrostatic equilibrium. We include the option for simple power-law envelope geometry, which combined with fractal clumping, and bipolar cavities, can be used to model evolved stars as well as protostars. We include non-thermal emission from PAHs and very small grains, and external illumination from the interstellar radiation field. The grid structure was modified to allow multiple dust species in each cell; based on this, a simple prescription is implemented to model dust stratification. We describe these features in detail, and show example calculations of each. Some of the more interesting results include the following: 1) Outflow cavities may be more clumpy than infalling envelopes. 2) PAH emission in high- mass stars may be a better indicator of evolutionary stage than the broadband SED slope; and related to this, 3) externally illuminated clumps and high-mass stars in optically thin clouds can masquerade as YSOs. 4) Our hydrostatic equilibrium models suggest that dust settling is likely ubiquitous in T Tauri disks, in agreement with previous observations. Accepted by Astrophysical Journal Supplements http://arxiv.org/pdf/1307.0561

Effect of Magnetic Misalignment on Protobinary Evolution Bo Zhao1, Zhi-Yun Li1, and Kaitlin M. Kratter2,3 1 University of Virginia, Astronomy Department, Charlottesville, VA, USA 2 JILA and CU/NIST, University of Colorado, Boulder, CO, 80309, USA 3 Hubble Fellow E-mail contact: bz6g at virginia.edu The majority of solar-type stars reside in multiple systems, especially binaries. They form in dense cores of molecular clouds that are observed to be significantly magnetized. Our previous study shows that magnetic braking can tighten the binary separation during the protostellar mass accretion phase by removing the angular momentum of the accreting material. Recent numerical calculations of single star formation have shown that misalignment between the magnetic field and rotation axis may weaken both magnetic braking and the associated magnetically driven outflows. These two effects allow for disk formation even in strongly magnetized cores. Here we investigate the effects of magnetic field misalignment on the properties of protobinaries. Somewhat surprisingly, the misaligned magnetic field is more efficient at tightening the binary orbit compared to the aligned field. The main reason is that the misalignment weakens the magnetically-driven outflow, which allows more material to accrete onto the binary. Even though the specific angular momentum of this inner material is higher than in the aligned case, it is insufficient to compensate for the additional mass. A corollary of this result is that a weaker field is required to achieve the same degree of inward migration when the field is tilted relative to the rotation axis. Large field misalignment also helps to produce rotationally-supported circumbinary disks even for relatively strong magnetic fields, by weakening the magnetically-dominated structure close to the binary. Our result may provide an explanation for the circumbinary disks detected in recent SMA and ALMA observations. Accepted by ApJ http://arxiv.org/pdf/1308.0830

48 Dissertation Abstracts

Modelling and observations of molecules in discs around young stars

John David Ilee

School of Physics & Astronomy, University of Leeds, UK School of Physics & Astronomy, University of St Andrews, UK Electronic mail: john.ilee at st-andrews.ac.uk Ph.D dissertation directed by: Ren´eOudmaijer, Thomas Hartquist & Paola Caselli Ph.D degree awarded: May 2013

This thesis contains a study of molecules within circumstellar discs around young stars. Firstly, the chemistry of a disc around a young, Class 0 protostar is modelled. Such discs are thought to be massive, and thus experience gravitational instabilities, which produce spiral density waves. These affect the chemistry in three ways; by desorbing molecules from dust grains, by providing extra energy for new reactions to take place, and by mixing the internal structure of the disc to provide a rich chemistry near the midplane. Secondly, high resolution near-infrared spectra of 20 massive young stellar objects are presented. The objects display CO first overtone bandhead emission, which is excited in the conditions expected within circumstellar discs. The emission is modelled using a simple analytic model of a Keplerian disc, and good fits are found to all spectra. On average, the discs correspond to being geometrically thin, spread across a wide range of inclinations. The discs are located within the dust sublimation radius, providing strong evidence that the CO emission originates in small gaseous discs, supporting the scenario in which massive stars form via disc accretion. Finally, medium resolution near-infrared spectra of 5 Herbig Ae & Be stars are presented. The spectra cover both CO bandhead and Br γ emission. Accretion rates are derived from the measuring the Br γ emission and through modelling the CO emission, however these accretion rates are found to be inconsistent. High resolution archival data of one of the targets is presented, and it is shown that this CO disc model is unable to fit the high resolution data. Therefore, it is concluded that to properly fit CO spectra, high resolution data are needed, and that previously published information determined from low resolution spectra should be treated with caution. http://www-star.st-and.ac.uk/~jdi3/docs/jdilee_thesis_web.pdf

49 The formation and feedback of high-mass stars

Tie Liu

Peking University, China Department of Astronomy, Peking University, 100871, Beijing, China Electronic mail: liutiepku at gmail.com Ph.D dissertation directed by: Yuefang Wu & Huawei Zhang Ph.D degree awarded: July 2013

High-mass stars play a major role in the evolution of the Galaxy. They are the principal sources of heavy elements and UV radiation in the Galaxy. However, the formation and evolution of high-mass stars are still unclear. Firstly, the initial condition for high-mass star formation is not clear; secondly, the mechanism of high-mass star formation is still under debate. The initial conditions of high-mass star formation are not well-known due to a lack of an appropriate large sample of prestellar cores. We have completed a 12CO/13CO/C18O line survey towards 674 Planck cold clumps with PMO 13.7 m telescope. We found that most of the Planck cold clumps are turbulent dominated and may represent the initial conditions of star formation. We have also discovered a large sample of dense cores in the Planck cold clumps in the mapping survey. Most of the dense cores are not associated with infrared sources and may be good candidates for prestellar cores. The CO abundance, CO depletion factor and CO-to-H2 conversion factor are strongly (anti-)correlated to other physical parameters (e.g. dust temperature, dust emissivity spectral index, column density, volume density and luminosity-to-mass ratio). To conclude, the gaseous CO abundance can be used as an evolutionary tracer for molecular clouds. Most of the high-mass star forming regions are located far away and have complex structures, which add the difficulties to detailed studies. Thus high spatial resolution observations with interferometers are critically needed. We have carried out a series of research using the data from the Submillimeter Array (SMA) to study the high-mass star forming regions. Our studies indicate that infall and outflow motions in high-mass star forming regions are very common. In JCMT 18354-0649S, we found collimated outflow and gas infall. In G9.62+0.19, we detected three dust cores. The middle core show rotating pattern and gas infall. The southern core is associated with an energetic and massive outflow. In G10.6-0.4 region, we found evidence for ”competitive accretion” model. Seven dust cores were detected in this region. The central one has the largest mass, while the offset ones have smaller mass. The gas infall in this region is dominated by the overall potential of the cluster. In G34.26+0.19, we found that at any spatial scale the infall velocity is constant, which indicates the infall is uniform. Through analyzing different high-mass star forming regions, we found that the infall velocity tightly correlates with the total dust/gas mass, which suggests that gravity plays the major role in gas accretion. We also have investigated the molecular environment of a sample of Herbig Ae/Be stars with 12CO/13CO lines as well as SED modeling. We found that Herbig Ae/Be star share similar properties with low-mass stars. The integrated intensity of CO emission correlates with the envelope mass. To study the feedback of massive stars, we have investigated the molecular environment of Wolf-Rayet (WR) stars. The evidence for interaction between the expanding bubbles and the surrounding molecular clouds as well as triggered star formation is revealed in several WR regions.

50 New Jobs

PhD Position at Leiden Observatory From Disks to Exoplanets: exploring the astrochemistry of planet formation Deadline: October 10, 2013

A 4-yr PhD position is available at Leiden Observatory. The research concerns the simulation of chemical processes in the planet-forming regions of protoplanetary disks and will explore the link between disk physical structure and chemistry and the eventual composition of (exo)planetary atmospheres. This research project will make use of state- of-the-art computational modelling, astrochemical methods, and laboratory data to simulate both the physics and chemistry of protoplanetary disks and the formation of gas-giant planets within these objects. The focus of this PhD research will be coupling chemical models of protoplanetary disks around young stars with evolutionary tracks of forming planets to identify physical and chemical parameters which influence the resulting planetary atmosphere composition. These simulations will be compared with astronomical observations of nearby protoplanetary disks with the Atacama Large Millimeter/Submillimeter Array and observations of molecules in the atmospheres of exoplanets and the Solar System gas giant planets. The research will be directed by Dr. C. Walsh and supervised by Prof. E. F. van Dishoeck. We are looking for an enthusiastic and motivated person with a background in astrophysics, astrochemistry, physical chemistry, or computational chemistry/physics. Applications should include a curriculum vitae (with a list of grades for exams), as well as a brief statement of research and programming experience. Applicants should arrange for two letters of reference to be uploaded to the website. Review of applications will start on October 10, 2013 and will continue until the position is filled. The starting date for the position is flexible, and can be anytime up to summer 2014. The position is open to students of all nationalities with the equivalent of a Masters degree in astronomy, physics, chemistry or mathematics. Web site for submission: http://jobs.strw.leidenuniv.nl/2013/dishoeckPhD/ Email address for inquiries: [email protected] [email protected] More information about Leiden Observatory can be found at: http://www.strw.leidenuniv.nl/ Information about the present astrochemistry program is available from: http://www.strw.leidenuniv.nl/ ewine http://www.strw.leidenuniv.nl/WISH http://www.laboratory-astrophysics.eu

51 Meetings

Exoplanets and Disks: Their Formation and Diversity II Kona, Hawaii, December 8-12, 2013

Purpose: Protoplanetary disks around young stars are the sites of planetary formation. Their detailed information has been obtained by recent high spatial resolution infrared and optical observations from both ground and space, and wide varieties of disk morphology and disk composition are uncovered. At longer wavelengths, ALMA has started its early science operation and will explore physical and chemical processing of gas and dust components in the disks. This diversity of disk properties is certainly the ”seeds” for the well known diversity of more than 800 exoplanets so far detected. Therefore, deep understanding of the link between the protoplanetary disks and exoplanets is becoming more and more important. New coronagraphs on the 8-m class telescopes such as Subaru/HiCIAO/AO188 (the SEEDS project) and Gemini/NICI are currently exploring these areas, and Subaru/SCExAO, Gemini/GPI, and VLT/SPHERE will come very soon. Besides observations, both theoretical simulations for planet formation and theories and laboratory experiments for dust formation/evolution also play crucial roles for the interpretation of the link. In addition to the above direct explorations of giant exoplanets and disks, more interests are now concentrating on detection of extrasolar terrestrial planets. In order to promote the discussion of the diversity of disks and exoplanets among related researchers, we would like to host an international workshop. This conference is the second one covering the similar topic held in 2009 (hosted by NAOJ). This is also recognized as the 5th of the Subaru International Conference Series. Researchers in the ﬁelds of protoplanetary/debris disks, exoplanets, dust, and related instrumentation are encouraged to attend. We expect more than 100 people attending. Main Topics: 1. Direct imaging of disks/exoplanets 2. Spectroscopy of disks/exoplanets 3. Various approaches toward earth-like planet detection 4. Theory for planet formation 5. Theory and simulation of exoplanet atmospheres 6. Dust formation and evolution in disks 7. Current/future instrumentation for direct observations Regular registration closes 30 September 2013 http://exoplanets.astron.s.u-tokyo.ac.jp/SubaruConf13/index.html

52 Meetings of Possible Interest

On the Origin of High-mass Stars 24 - 27 September 2013 Splinter Meeting E at the Annual Meeting of the Astronomische Gesellschaft, Tübingen, Germany http://www.astro.uni-bonn.de/~jpflamm/AG2013/AG-Splinter.html Evolution of Star Clusters: From Star Formation to Cosmic Ages 24 - 27 September 2013 Splinter Meeting E at the Annual Meeting of the Astronomische Gesellschaft, Tübingen, Germany http://www-astro.physik.tu-berlin.de/~harfst/AG2013_SplinterE/ Dust Radiative Transfer - Codes and Benchmarks 9 - 11 October 2013 http://ipag.osug.fr/RT13/index.php The Orion Nebula Cluster as a Paradigm for Star Formation 14 - 16 October 2013 STScI, Baltimore, USA http://www.stsci.edu/institute/conference/orion/ Physical Processes in the Interstellar Medium 21 - 25 October 2013 MPE, Garching, Germany http://www.ism-spp.de/conferences/ismsppcon2013/ 400 Years of Stellar Rotation 17 - 22 November 2013, Natal, Brazil http://www.dfte.ufrn.br/400rotation/ 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/ Exoplanets and Disks: Their Formation and Diversity II 8 - 12 December 2013, Kona, Hawaii, USA http://exoplanets.astron.s.u-tokyo.ac.jp/SubaruConf13/index.html An Olympian Symposium for Star Formation 26 - 30 May 2014 Paralia Katerinis, Mount Olympus, Greece http://zuserver2.star.ucl.ac.uk/$\sim$tb/ EPoS2014 The Early Phase of Star Formation 1 - 6 June 2014 Ringberg Castle, Tegernsee, Germany http://www.mpia-hd.mpg.de/homes/stein/EPoS/epos.php The Dance of Stars: Dense Stellar Systems from Infant to Old 2 - 6 June 2014 Bad Honnef, Germany http://www.astro.uni-bonn.de/$\sim$sambaran/DS2014/index.html 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/ Summer School on Protoplanetary Disks: Theory and Modeling meet Observations 16 - 20 June 2014 Groningen, The Netherlands http://www.diana-project.com/summer-school Characterizing Planetary Systems Across the HR Diagram 28 July - 1 August 2014 Inst. for Astronomy, Cambridge, USA http://www.ast.cam.ac.uk/meetings/2013/AcrossHR

53 Living Together: Planets, Stellar Binaries and Stars with Planets 8 - 12 September 2014 Litomysl Castle, Litomysl, Czech Republic http://astro.physics.muni.cz/kopal2014/ Planet Formation and Evolution 2014 10 - 12 September 2014 Kiel, Germany http://www1.astrophysik.uni-kiel.de/$\sim$2014/main/ 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/

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54 Short Announcements

Protostars and Planets VI Posters and Movies The posters from the Protostars and Planets VI conference are now available at: http://www.ppvi.org/posters/ All of the oral presentations were ﬁlmed during the conference, and they are now available at: http://www.mpia-hd.mpg.de/homes/ppvi/talks This allows you to attend or re-attend the conference from the comfort of your oﬃce or your living room!

Fizeau exchange visitors program - call for applications Dear colleagues! The Fizeau exchange visitors program in optical interferometry funds (travel and accommodation) visits of researchers to an institute of his/her choice (within the European Community) to perform collaborative work and training on one of the active topics of the European Interferometry Initiative. The visits will typically last for one month, and strengthen the network of astronomers engaged in technical, scientific and training work on optical/infrared interferometry. The program is open for all levels of astronomers (Ph.D. students to tenured staff). Applicants are strongly encouraged to seek also partial support from their home or host institutions. The deadline for applications is September 15. Fellowships can be awarded for missions starting in November 2013. Further informations and application forms can be found at www.european-interferometry.eu and vltischool.sciencesconf.org The program is funded by OPTICON/FP7. Please distribute this message also to potentially interested colleagues outside of your community! Looking forward to your applications, Josef Hron & Laszlo Mosoni (for the European Interferometry Initiative) Electronic mail: fi[email protected]