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

No. 325 — 15 January 2020 Editor: Bo Reipurth ([email protected]) List of Contents

The Star Formation Newsletter Perspective ...... 3 Abstracts of Newly Accepted Papers ...... 9 Editor: Bo Reipurth [email protected] Abstracts of Newly Accepted Major Reviews .. 30

Associate Editor: Anna McLeod Dissertation Abstracts ...... 31 [email protected] New Jobs ...... 32 Technical Editor: Hsi-Wei Yen Meetings ...... 35 [email protected] Summary of Upcoming Meetings ...... 36

Editorial Board

Joao Alves Alan Boss Jerome Bouvier Lee Hartmann Cover Picture Thomas Henning Paul Ho The L1622 cloud in Orion is a fine case of a bright- Jes Jorgensen rimmed cometary cloud. It is located just outside of Charles J. Lada Barnard’s Loop, and points towards the OB in Thijs Kouwenhoven the Orion Cluster. The bright nebulous star Michael R. Meyer near the center of the image is the young multiple Ralph Pudritz system HBC 515. Luis Felipe Rodríguez Subaru 8m image by Bo Reipurth Ewine van Dishoeck Processing by Robert Gendler. Hans Zinnecker

The Star Formation Newsletter is a vehicle for fast distribution of information of interest for as- tronomers working on star and planet formation and molecular clouds. You can submit material Submitting your abstracts for the following sections: Abstracts of recently accepted papers (only for papers sent to refereed Latex macros for submitting abstracts journals), Abstracts of recently accepted major re- and dissertation abstracts (by e-mail to views (not standard conference contributions), Dis- [email protected]) are appended to sertation Abstracts (presenting abstracts of new each Call for Abstracts. You can also Ph.D dissertations), Meetings (announcing meet- submit via the Newsletter web inter- ings broadly of interest to the star and planet for- face at http://www2.ifa.hawaii.edu/star- mation and early community), New formation/index.cfm Jobs (advertising jobs specifically aimed towards persons within the areas of the Newsletter), and Short Announcements (where you can inform or re- quest information from the community). Addition- 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 Perspective Protostellar accretion and its impact on the pre- evolution Emanuele Tognelli

1 Introduction Figure 1: HR diagram for young PMS stars extracted from The detailed computation of what happens to a star at the the literature compared to a set of standard evolutionary beginning of its life, the phases that lead to the formation models and isochrones from the PISA database (Tognelli of a star (protostellar evolution) and the subsequent pre- et al. 2011, 2018). main sequence evolution (PMS) has been a hard task for many . Starting from the pioneering work by Larson (1969), which analysed the protostellar evolution from the 2 Pre-main sequence stars data gravitational collapse of the parental cloud to the PMS phase, recently such an evolution has been revised thanks From the observational point of view, there are a lot of to the improvements in both the input physics and com- data for young PMS stars (ages ∼ 1 Myr) for solar or putational power. A particularly interesting result is that slightly sub-solar . Among these objects, some even if the first collapsing phases are difficult to follow, the of them show a still detectable accretion disc, or protoplan- simulations predict the formation of a hydrostatic core: etary disc, and very low accretion rates (see e.g. Hartmann the characteristics of such a hydrostatic core (2nd Larson & Kenyon 1996, Muzerolle et al. 2000, Calvet et al. 2005, core) such as its , radius, temperature and density, Muzerolle et al. 2005a,b, Bae et al. 2013, Ingleby et al. appear to be very robust. 2014). Such residual accretion discs show clear footprints of a previous accretion phase. The ideal approach would be to follow the whole proto- stellar and then in hydrodynamical simu- It is interesting to note that once placed into a colour- lation, to treat simultaneously and in detail the structure magnitude or HR diagram, young PMS stars are located and evolution of both the protostar and the surrounding in a region corresponding to bright and extended (hence material that falls on it. However, such an approach is at cold) objects. As an example, Figure 1 shows a sample of the moment extremely difficult and not feasible. To over- young PMS stars available in the literature. come this problem, some simplifications can be adopted. Such stars are fully formed, in the sense that the mea- A common approach consists in starting the protostel- sured accretion rates are extremely small, thus, they have lar evolution after the formation of the 2nd Larson core, already reached their final mass. Consequently, they can when the central protostar is assumed to be hydrostatic. be considered as stars that are evolving as constant mass The matter surrounding the star can be treated both as a structures. Moreover, given the large and radii, spherical structure that radially falls on the star (spherical 2 the thermal or -Helmholtz time (τKH ∝ GM /LR) accretion, e.g. Stahler et al. 1980) or a disc like struc- are relatively small (of the order of 103-104 yr), thus it can ture that provides accreting matter via accretion streams be assumed that they have lost memory (or they will) of (disc accretion, e.g. Hartmann et al. 1997). In this short what happened during their protostellar phase. review, I will present some of the main characteristics of accreting models in these two geometries (spherical or disc The location in the colour-magnitude (CM) or Hertzprung- accretion) and some related problems, focusing on the for- Russell (HR) diagram of such objects poses a first con- straint on the models. Stellar models must reproduce the mation of low-mass (M < 1 M⊙) solar metallicity stars. More details can be found in the review by Larson (2003) position of these stars. In particular, young stellar mod- and Hartmann et al. (2016). els (ages of the order of ∼ 1 Myr) must be located in the region of bright, cold and extended objects.

3 3 Cloud collapse and protostellar ac- cretion

Stars form in a region (cloud) that contracts and gives birth to denser cores that eventually form the protostar and then the star. In this process, the mass of a protostar progressively increases as the matter in the cloud falls onto a central denser object. The cloud collapse is a complex hydrodynamical problem, a challenging task in the stellar formation field. Depending on the characteristics of the cloud and on the configuration assumed in the compu- tations (chemical composition, magnetic fields, rotation, geometry...) the collapse occurs faster or slower, but the general evolution can be summarised as outlined below (for more details see Larson 1969, 1972 and the review by Larson 2003):

• Isothermal collapse: during the first collapse, the cloud does not warm up as it contracts. This is true until a central density of about 10−13 g cm−3 is reached. When this occurs, the matter in the inner Figure 2: Comparison between standard isochrones (thin region of the cloud is dense enough to partially trap solid lines) and the loci of the end of protostellar accreting radiation. sequence for two different initial temperatures of the cloud • Formation of the first Larson core: the energy is par- (10 K thick solid and 20 K thick dashed line). Circles mark tially trapped inside the denser region of the cloud the position of 0.25, 0.5, 1, 1.5, 2, 3, and 5 M⊙ models. preventing a further collapse of this region. A first Figure adapted from Larson (1972). temporarily hydrostatic core forms (with a mass of about 0.01 M⊙ and a radius of several AU). Outside of it the matter is still falling on the core. There is the computations. Larson (1969) remarked the fact that a transition region (shock front) close to the surface at some stage the cloud gives birth to a hydrostatic central of the core where the matter settles and passes from object (2nd Larson core) that can be considered the first supersonic to subsonic. protostellar core. The characteristics of this model (i.e. mass, radius, density and central temperature) appeared • Second collapse: the hydrostatic core contracts be- to be not much sensitive to the adopted initial conditions cause it can partially radiate energy at the surface. of the cloud or to the adopted input physics (Masunaga & So, although its mass is increasing due to accretion Inutsuka 2000, Machida et al. 2008, Tomida et al. 2013, of mass, its radius shrinks. The contraction of the Vaytet et al. 2013). Reasonable intervals for the mass, ra- core leads to a temperature rise, until T ∼ 2000 K dius and temperature of such a core are the following: the is reached, and molecular hydrogen dissociates. The mass ranges from 1 - 20 MJ, the radius from 0.5 - 10 R⊙ contraction energy does not warm the core but it is and the central temperature from 2-6×104 K. In Larson used to dissociate H2. The density and pressure of (1969, 1972), the author followed the subsequent evolu- the core increase. tion until the star reaches the Hayashi track, finding that low mass stars (M < 1 M⊙) attain, after the protostellar Formation of the 2nd Larson core: • after the total accretion, characteristics similar to that of standard evo- dissociation of H2 and the increase of density and lution along the Hayashi track. In contrast, as the mass pressure, the central core assumes a hydrostatic con- increases (M > 2 M⊙), stars skip the Hayashi line, ending figuration with a mass ∼ 0.001 M⊙ (=1 MJ, the protostellar phase closer and closer to the MS posi- mass) and a radius of 1 R⊙, while mass is still falling tion. Figure 2 shows an HR diagram with the sequence radially on the core. From this moment on the cen- that identifies the end of the protostellar accretion (when tral objects maintains its hydrostatic configuration the star becomes visible) compared to standard isochrones. as its mass increases. Interestingly, the end of the protostellar evolution is very close to the position of the 1 Myr standard isochrone. The stages briefly listed above are quite general (for solar metallicity stars) and almost independent of the details of It is worth to remark that the results of such an initial

4 protostellar evolution cannot be easily checked with obser- mainly concerns the geometry of the accreting protostar- vations, as the protostellar evolution in these first phases envelope system: occurs within the cloud and the central core cannot be directly observed. • Spherical accretion (see e.g. Stahler et al. 1980, Stahler 1988, Stahler & Palla 1991, 1992, 1993). The star is supposed to be deeply embedded into 4 Protostellar accretion in hydro- the parental cloud and the matter falls on it almost radially. The whole stellar surface is subjected to static stellar evolution codes the accretion and as such in this case the energy radiated from the star can be reabsorbed by the en- The hydrodynamical evolution of accreting stars is still velope. The whole protostellar accretion occurs as a a challenging task from the computational point of view. radial infall, from a cloud that has mass enough to For only a few cases has it been possible to follow a portion generate the star, at a fixed value of the accretion of the evolution for PMS stars. However, for what con- rate. cerns the central protostar, it is not necessary to employ a hydrodynamical code, as the protostar itself is hydrostatic • Disc accretion (Hartmann et al. 1997, Siess et al. if the accretion phase after the formation of the 2nd Lar- 1997). The matter falls from a boundary layer of son core is considered. In this approximation, the central a disc and reaches the star via accretion streams. object can be described using a mono dimensional hydro- Most of the stellar surface is not subjected by the static stellar evolutionary code (e.g. Siess et al. 1997, accretion and the star is free to radiate its energy, Stahler et al. 1980). most of which is lost in space. The disc structure is assumed to be totally decoupled from the that of the The problem resides in the characteristics of the envelope central star and it is not treated in the stellar evo- surrounding the protostar, which does not satisfy the hy- lution code (nor its evolution neither its structure). drostatic conditions. It is important to remember that the The parameters that define the accretion (accretion structure of the envelope of matter surrounding the star rate, disk lifetime, accretion energy) consequently provides the characteristics of the accretion flow. In more are considered as external free parameters which can detail, it gives information about the following quantities: be taken from detailed accretion disc evolution codes (e.g. Vorobyov & Basu 2010, Baraffe et al. 2012). • The accretion rate. The accretion rate (m˙ ) defines the rate at which the star changes its mass in time. The spherical accretion scenario is likely to describe the The value of m˙ can vary of order of magnitude dur- first stages of the formation of the protostar when the star ing the accretion phase, passing from m<˙ 10−6- −7 is still embedded within the cloud that retains an approx- 10 M⊙/yr (quiescent accretion) to rapid and in- imate spherical geometry. However, observations suggest tense episodes of accretion of matter (bursts, m˙ ∼ −4 −3 that at some stage of protostellar evolution, the cloud col- 10 -10 M⊙/yr, e.g. FU Ori stars, Hartmann & lapses to a disc, and it is during the disc accretion that Kenyon 1996). the star gains most of its final mass. So, both scenar- • The energy in the accreted matter. The matter that ios are interesting and describe a part of the protostellar falls on the star before reaching the stellar surface accretion. has a kinetic energy. However, when it settles on the The most important difference between spherical and disc stellar surface, the kinetic energy is equal to zero. accretion, which deeply affects the protostellar evolution, So, energy conservation states that the kinetic en- is the amount of energy retained in the accreted matter. ergy has been converted into another form of en- Indeed, while in the simplified spherical accretion it is pos- ergy. Depending on the characteristic of the accre- sible to estimate the amount of energy retained by the tion flow, such an energy can be thermal energy (the accreted matter, in disc accretion this quantity is defined accreted matter is hot), or the energy can be radi- by a free parameter (αacc). The impact of this on the ated (photons) before the matter reaches the stellar evolution is discussed in the next sections. surface (at the shock front), or part of the energy can be retained by the matter and part radiated. The fraction of energy accreted can also depend on the 5 Spherical and disc protostellar ac- accretion rate (e.g. Baraffe et al. 2012). cretion The difficulty in treating simultaneously the protostar and the envelope evolution requires some simplification, which The spherical accretion scenario applies to a star that is deeply embedded in a cloud of gas. In this case, the evo-

5 −6 −3 10 to 10 M⊙/yr), adopting a spherical protostellar accretion code similar to that used by Stahler and Palla. They showed that increasing m˙ , the birthline moves to- wards larger and radii, thus still in full agree- ment with the observations. It is also interesting to note that spherical accretion mod- els produce low-mass stars (on the birthline) in a region that corresponds to the top of the Hayashi track of stan- dard stellar models (see Figure 3). So, differences be- tween standard and spherical accreting models in low-mass stars are negligible, and consequently standard evolution- ary tracks/isochrones can be safely used to infer the char- acteristic of young stellar populations (at least for ages above 1 Myr). However, as anticipated, it is commonly accepted that stars do not accrete spherically during their whole pro- tostellar phase. They gain most of their mass from an accretion disc, thus motivating the detailed study of pro- Figure 3: Comparison between standard tracks (solid tostellar accretion in this geometry. lines) and the birthline (dotted line) obtained by Palla Differently from the spherical accretion, in the disc geome- & Stahler (1993). Dots represents T Tauri and Herbig try, most of the star is free to radiate its energy into space Ae/Be stars. Figure adapted from Palla & Stahler (1993). and the accretion streams cover only a very limited part of the stellar surface (few percent, see e.g. Hartmann et al. 1997). All the parameters that defines the accretion lution of the star and of the envelope have to be treated (i.e. accretion rate, energy inside the accreted matter) are simultaneously. This allows to have a consistent evalua- treated as external parameters. tion of the amount of thermal energy that the accretion flows brings inside the star. Qualitatively, the energy emit- In the disc accretion geometry, it is possible to follow also ted from the stellar surface is not free to escape into space an analytic approach to analyse the main characteristics since it has to cross the matter around the star, thus such of the protostellar accretion on a forming star. Following an energy is partially reabsorbed by the matter in the en- the formalism developed by Hartmann et al. (1997), it velope, and it eventually reaches the star. The effect of is possible to write a simple equation for the temporal this process is that the star has a kind of external energy evolution of the accreting star radius as follows, source that warms up the stellar surface. The injection R˙ 7 R 1 GM 2 m˙ into the star of thermal energy from the accreted mass = βD − Lph + αacc − (1) forces the star to expand or at least to compensate for the R 3 GM 2   7 R M  radius decrease caused by injection of mass. where M and R are the and radius, βD ex- The impact of spherical accretion on the formation of PMS presses the luminosity due to the deuterium burning (D- stars has been largely analysed in the pioneering work by burning), Lph is the luminosity at the stellar surface, m˙ Stahler and Palla, and recently also by Hosokawa and col- is the mass accretion rate and αacc represents the frac- laborators. One of the main result of such a spherical tion of the accretion energy actually deposed into the star accretion scenario is that stars during the accretion phase (thermal energy in the accreted matter). remain bright and extended. Using a mild and constant −5 Equation (1) contains three terms: the first and the second accretion rate of 10 M⊙/yr, Palla & Stahler (1993), are the normal terms that defines the evolution of the star showed that it is possible to produce an accreting sequence with a surface radiative loss (L ) plus D-burning energy in a region of the HR diagram that corresponds to the ph generation β , while the last term is that responsible for upper envelope of the locus where young PMS stars are D the accretion, being proportional to m˙ . This term contains located (see Figure 3). The authors defined this sequence also the dependency on the thermal energy carried into the as the birthline, which is the locus of stars with differ- star by the accretion (α ). Such a parameter has to be ent where the stars become visible when accretion acc specified as an external free parameter that moves in the ends. range [0, 1] (or in case of thin disc [0, 1/2], see e.g. Siess et More recently, Hosokawa et al. (2009) computed a set of al. 1997). From the same equation, it is also evident that birthlines for different values of the accretion rate (from αacc =1/7 ≡ αacc,cr defines a critical value, meaning that

6 for αacc < αacc,cr the third term is negative, and would contribute to a radius decrease, while for αacc > αacc,cr the last term produces a radius expansion. It is common to refer to the case αacc ∼ 0 (or αacc ≪ αacc,cr) as the cold disc accretion and αacc > αacc,cr as the hot disc accretion. Looking at eq. (1) it is clear that a radius expansion re- quires a positive value of the right side of equation, which can be obtained both having 1) an efficient deuterium burning (large βD) or 2) an efficient accretion energy trans- port into the protostar (αacc < αacc,cr). These two cases are discussed separately in the next two sections.

6 D-burning during protostellar ac- cretion

First, it is convenient to analyse if it is possible to pro- duce an extended protostar using only the D-burning. To do this, let’s assume αacc = 0. From eq. (1), to produce a radius increase, D-burning has to supply the star with energy to counterbalance the radiative loss at the stellar surface plus the gravitational energy decrease caused by the mass ingestion. If this condition is not satisfied, the Figure 4: Effect of deuterium abundance XD on the pro- protostar contracts and the resulting model at the end tostellar evolution. Grey filled lines are standard PMS of the protostellar phase has a radius much smaller than tracks. The region covered by young PMS is shown as that expected in standard (or spherical accretion) cases. a shaded area. Top panel: models for an initial mass The dependency of the radius on deuterium abundance Mseed = 10 MJ. Bottom panel: models for Mseed =2 MJ. (XD) has been evaluated by Kunitomo et al. (2017); they checked the impact assuming one value for the 2nd Lar- to reproduce the observed young PMS stars. son core mass, namely Mseed =0.01 M⊙(=10 MJ). Such a value of Mseed corresponds to the upper border of its vari- ability range, and it would be better to check also what happens if a smaller initial mass is adopted. Figure 4 7 Accretion energy shows a comparison between birthlines obtained assuming different values of XD, for two values of Mseed, namely There is another natural way to obtain a radius expan- Mseed = 10 MJ (top panel) and 2 MJ (bottom panel). sion in protostars, which is assuming that the ingested For clarity, the figure also shows the region (shaded area) matter retains part of its internal energy. This means to where young PMS stars are located. To place the birth- assume a value of αacc > αacc,cr. Hartmann et al. (1997) line in the shaded area, large values of XD are required. showed that non-cold accretion models (αacc> αacc,cr) can In the case of Mseed = 10 MJ, it is enough to adopt attain a radius expansion large enough to reproduce ob- −5 XD =4 × 10 , which is about two times larger than the served stars. Moreover, they showed that such models are current deuterium abundance measured in the interstellar capable of reproducing the characteristics of the spherical medium (XD,ISM, Linsky et al. 2006). The situation is birthline obtained by Stahler (1988). Recently, Kunitomo even worse if Mseed =2 MJ; in this case it is necessary to et al. (2017) analysed in more details the impact of αacc on adopt a deuterium abundance about 10 times larger than the formation of a 1 M⊙ model. Figure 5 shows the birth- XD,ISM. This simple analysis seems to indicate that to line obtained using several values of αacc in two different produce stars with large radii at the end of the protostel- configuration: in one case the accretion energy is redis- lar accretion, a fine tuning of XD is needed; such a value tributed in the whole star (assumed to be fully convec- depends on the initial seed mass and on the final mass, tive), in the other case, the star is distributed only in the thus it would be different from stars to stars even if these convective envelope. This second case is particularly inter- stars formed from the same parental cloud with the same esting, because hot accretion models (i.e. αacc> αacc,cr) chemical composition. In conclusion, deuterium alone is develops a radiative core and convection is present only in unlikely to be responsible for the radius increase required a surface region that, during the star evolution, reduces in

7 observed in young clusters. Indeed, cold accretion models, which are fully convective during the whole protostellar evolution, attains a central temperature during the pro- tostellar phase much larger than that required to ignite lithium burning (about 2.5 × 106 K). The result is that lithium is completely depleted in the whole star before the end of protostellar accretion. On the other hand, lithium is preserved if hot accretion models are used. This seems to be another indication that stars accrete a significant fraction of their mass in a hot accretion scenario. References:

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8 Abstracts of recently accepted papers

On the mass segregation of cores and stars Hayley L. Alcock1 and Richard J. Parker1 1 Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK E-mail contact: R.Parker at sheffield.ac.uk Observations of pre- and proto-stellar cores in young star-forming regions show them to be mass segregated, i.e. the most massive cores are centrally concentrated, whereas pre-main sequence stars in the same star-forming regions (and older regions) are not. We test whether this apparent contradiction can be explained by the massive cores fragmenting into stars of much lower mass, thereby washing out any signature of mass segregation in pre-main sequence stars. Whilst our fragmentation model can reproduce the stellar initial mass function, we find that the resultant distribution of pre-main sequence stars is mass segregated to an even higher degree than that of the cores, because massive cores still produce massive stars if the number of fragments is reasonably low (between one and five). We therefore suggest that the reason cores are observed to be mass segregated and stars are not is likely due to dynamical evolution of the stars, which can move significant distances in star-forming regions after their formation. Accepted by MNRAS https://arxiv.org/pdf/1909.07982

Exploring the formation pathways of formamide near young O-type stars V. Allen1,2,3, F.F.S. van der Tak2,3, A. López-Sepulcre4,5, Á. Sánchez-Monge6, V.M. Rivilla7, and R. Cesaroni7 1 NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA; 2 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, the Netherlands; 3 SRON, Landleven 12, 9747 AD Groningen, the Netherlands; 4 CNRS, IPAG, Univ. Grenoble Alpes, F-38000 Grenoble, France; 5 IRAM, 300 rue de la Piscine, 38406 Saint-Martin d’ Hères, France; 6 I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany; 7 INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Florence, Italy E-mail contact: veronica.a.allen at nasa.gov

Context. As a building block for amino acids, formamide (NH2CHO) is an important molecule in astrobiology and astrochemistry, but its formation path in the interstellar medium is not understood well. Aims. We aim to find empirical evidence to support the chemical relationships of formamide to HNCO and H2CO. Methods. We examine high angular resolution (∼0′′. 2) Atacama Large Millimeter/submillimeter Array (ALMA) maps of six sources in three high-mass star-forming regions and compare the spatial extent, integrated emission peak position, and velocity structure of HNCO and H2CO line emission with that of NH2CHO by using moment maps. Through spectral modeling, we compare the abundances of these three species. Results. In these sources, the emission peak separation and velocity dispersion of formamide emission is most often similar to HNCO emission, while the velocity structure is generally just as similar to H2CO and HNCO (within errors). From the spectral modeling, we see that the abundances between all three of our focus species are correlated, and the relationship between NH2CHO and HNCO reproduces the previously demonstrated abundance relationship. Conclusions. In this first interferometric study, which compares two potential parent species to NH2CHO, we find that all moment maps for HNCO are more similar to NH2CHO than H2CO in one of our six sources (G24 A1). For the other five sources, the relationship between NH2CHO, HNCO, and H2CO is unclear as the different moment maps for each source are not consistently more similar to one species as opposed to the other. Accepted by A&A http://arxiv.org/pdf/1912.11883

9 Are Inner Disc Misalignments Common? ALMA Reveals an Isotropic Outer Disc In- clination Distribution for Young Dipper Stars M. Ansdell1,2,3, E. Gaidos4, C. Hedges5, M. Tazzari6, A.L. Kraus7 et al. 1 Center for Integrative Planetary Science, University of California at Berkeley, Berkeley, CA 94720, USA; 2 De- partment of Astronomy, University of California at Berkeley, Berkeley, CA 94720, USA; 3 Flatiron Institute, Simons Foundation, 162 Fifth Ave, New York, NY 10010, USA; 4 Department of Sciences, University of Hawai’i at Ma¯noa, Honolulu, HI, USA; 5 NASA Ames Research Center, Moffett Blvd, Mountain View, CA 94035, USA; 6 Insti- tute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA, Cambridge, UK; 7 Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA E-mail contact: mansdell at flatironinstitute.org Dippers are a common class of young variable star exhibiting -long dimmings with depths of up to several tens of percent. A standard explanation is that dippers host nearly edge-on (70◦) protoplanetary discs that allow close-in (<1 au) dust lifted slightly out of the midplane to partially occult the star. The identification of a face-on dipper disc and growing evidence of inner disc misalignments brings this scenario into question. Thus we uniformly (re)derive the inclinations of 24 dipper discs resolved with (sub-)mm interferometry from ALMA. We find that dipper disc inclinations are consistent with an isotropic distribution over 0◦–75◦, above which the occurrence rate declines (likely an observational selection effect due to optically thick disc midplanes blocking their host stars). These findings indicate that the dipper phenomenon is unrelated to the outer (>10 au) disc resolved by ALMA and that inner disc misalignments may be common during the protoplanetary phase. More than one mechanism may contribute to the dipper phenomenon, including accretion-driven warps and "broken" discs caused by inclined (sub-)stellar or planetary companions. Accepted by MNRAS http://arxiv.org/pdf/1912.01610

The Orion Protostellar Explosion and Runaway Stars Revisited: Stellar Masses, Disk Retention, and an Outflow from BN John Bally1, Adam Ginsburg2, Jan Forbrich3, and Jaime Vargas-González3 1 Center for Astrophysics and Space Astronomy, Astrophysical and Planetary Sciences Department, University of Colorado, UCB 389 Boulder, Colorado 80309, USA; 2 Department of Astronomy, University of Florida, Bryant Space Science Center, Stadium Road, Gainesville, FL 32611; 3 Centre for Astrophysics Research, School of Physics, Astron- omy and Mathematics, Hertfordshire University, College Lane, Hatfield, AL10 9AB, UK E-mail contact: [email protected] The proper motions of the three stars ejected from Orion’s OMC1 cloud core are combined with the requirement that their center of mass is gravitationally bound to OMC1 to show that radio source I (Src I) is likely to have a mass around 15 M⊙ consistent with recent measurements. Src I, the star with the smallest , is suspected to be either an AU-scale binary or a protostellar merger remnant produced by a dynamic interaction ∼550 years ago. Near-infrared 2.2 µm images spanning ∼21 years confirm the ∼55 km/s motion of ‘source x’ (Src x) away from the site of stellar ejection and point of origin of the explosive OMC1 protostellar outflow. The radial velocities and masses of the Becklin-Neugebauer (BN) object and Src I constrain the of Src x to be VLSR = −28 ± 10 km/s. Several high proper-motion radio sources near BN, including Zapata 11 ([ZRK2004] 11) and a diffuse source near IRc 23, may trace a slow bipolar outflow from BN. The massive disk around Src I is likely the surviving portion of a disk that existed prior to the stellar ejection. Though highly perturbed, shocked, and re-oriented by the N-body interaction, enough time has elapsed to allow the disk to relax with its spin axis roughly orthogonal to the proper motion. Accepted by The Astrophysical Journal http://arxiv.org/pdf/2001.00899

10 ALMA observations reveal no preferred outflow–filament and outflow–magnetic field orientations T. Baug1, Ke Wang1, Tie Liu2, Mengyao Tang3, Qizhou Zhang4, Di Li5,6, Eswaraiah Chakali5,7, Sheng- Yuan Liu8, Anandmayee Tej9, Paul F. Goldsmith10, Leonardo Bronfman11, Sheng-Li Qin3, Viktor L. Toth12, Pak-Shing Li13 and Kee-Tae Kim14 1 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, China; 2 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China; 3 Department of Astronomy, Yunnan University, Kunming, 650091, China; 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 5 CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China; 6 University of Chinese Academy of Sciences, Beijing 100049, China; 7 National Astronomical Observatories, Chinese Academy of Science, A20 Datun Road, Chaoyang District, Beijing 100012, China; 8 Academia Sinica, Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 9 Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547, Kerala, India; 10 Jet Propulsion Laboratory, National Aeronautics and Space Administration, United States; 11 Depar- tamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile; 12 Eövös Loránd University, Department of Astronomy, Pázmány Péter sétány 1/A, H-1117, Budapest, Hungary; 13 University of California, Berkeley, United States; 14 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea E-mail contact: tapas.polo at gmail.com We present a statistical study on the orientation of outflows with respect to large-scale filaments and the magnetic fields. Although filaments are widely observed toward Galactic star-forming regions, the exact role of filaments in star formation is unclear. Studies toward low-mass star-forming regions revealed both preferred and random orientation of outflows respective to the filament long-axes, while outflows in massive star-forming regions mostly oriented perpendicular to the host filaments, and parallel to the magnetic fields at similar physical scales. Here, we explore outflows in a sample of 11 protoclusters in HII regions, a more evolved stage compared to IRDCs, using ALMA CO (3–2) line observations. We identify a total of 105 outflow lobes in these protoclusters. Among the 11 targets, 7 are embedded within -scale filamentary structures detected in 13CO line and 870 µm continuum emissions. The angles between outflow axes and corresponding filaments (γFil) do not show any hint of preferred orientations (i.e., orthogonal or parallel as inferred in numerical models) with respect to the position angle of the filaments. Identified outflow lobes are also not correlated with the magnetic fields and Galactic plane position angles. Outflows associated with filaments aligned along the large-scale magnetic fields are also randomly orientated. Our study presents the first statistical results of outflow orientation respective to large-scale filaments and magnetic fields in evolved massive star-forming regions. The random distribution suggests a lack of alignment of outflows with filaments, which may be a result of the evolutionary stage of the clusters. Accepted by The Astrophysical Journal https://arxiv.org/pdf/1912.13240

The Young Survey: Detection of a wide orbit planetary mass companion to a solar-type Sco-Cen member A.J. Bohn1, M.A. Kenworthy1, C. Ginski2, C.F. Manara3, M.J. Pecaut4 et al. 1 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 Sterrenkundig Instituut Anton Pannekoek, Science Park 904, 1098 XH Amsterdam, The Netherlands; 3 European Southern Observatory, Karl- Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 4 Rockhurst University, Department of Physics, 1100 Rockhurst Road, Kansas City, MO 64110, USA E-mail contact: bohn at strw.leidenuniv.nl The Young Suns Exoplanet Survey (YSES) consists of a homogeneous sample of 70 young, solar-mass stars located in the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an average age of 15±3 Myr. We report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211-6456207) that is located at a distance of 94.6±0.3 pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with VLT/X-SHOOTER constrain the mass of the star to 1.00±0.02 M⊙ and an age of 16.7±1.4 Myr. The companion

11 TYC 8998-760-1 b is detected at a projected separation of 1′′. 71, which implies a projected physical separation of 162 au. Photometric measurements ranging from Y to M band provide a mass estimate of 14±3 Mjup by comparison to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q = 0.013 ± 0.003 with respect to the primary. We rule out additional companions to TYC 8998-760-1 that are more massive than 12 Mjup and farther than 12 au away from the host. Future polarimetric and spectroscopic observations of this system with ground and space based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of the circumstellar environment around this ‘young ’. Accepted by MNRAS http://arxiv.org/pdf/1912.04284

USco1621 B and USco1556 B: Two wide companions at the deuterium-burning mass limit in Upper Scorpius Patricia Chinchilla1,2, Víctor J.S. Béjar1,2, Nicolas Lodieu1,2, Bartosz Gauza3,4, Maria Rosa Zapatero Osorio5 et al. 1 Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain; 2 Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain; 3 Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 4 Janusz Gil Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland; 5 Centro de Astrobiología (CSIC-INTA), Ctra. de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain E-mail contact: pcg at iac.es Our aim is to identify analogues of planets, as companions at wide separations of very young stars. To identify these objects, we cross correlated the Visible and Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) and the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Clusters Survey (UKIDSS GCS) catalogues to search for common proper motion companions to 1195 already known members of Upper Scorpius (USco; age ∼5–10 Myr, distance ∼145 pc). We present the discovery and spectroscopic characterisation of two very wide substellar companions of two early-M stars in Upper Scorpius: USco1621 B and USco1556 B. We obtained optical and near-infrared low-resolution spectroscopy of the candidates to characterise their spectral energy distribution and confirm their membership to the association. We also acquired adaptive optics images of the primaries and secondaries to search for signs of binarity and close companions. We determined a spectral type of M8.5 in the optical for both companions, along with L0 and L0.5 in the near-infrared for USco1621 B and USco1556 B, respectively. The spectra of the two companions show evident markers of youth. The comparison with theoretical evolutionary models gives estimated masses of 0.015±0.002 and 0.014±0.002 M⊙, with temperatures of 2270±90 and 2240±100 K, respectively. The physical separations between the components of both systems are 2880±20 and 3500±40 AU for USco1621 and USco1556 systems, respectively. We did not find any additional close companion in the adaptive optics images. The probability that the two secondaries are physically bound to their respective primaries, and not chance alignments of USco members, is 86%, and the probability that none of them are physically related is 1.0%. Accepted by A&A http://arxiv.org/pdf/1912.04150

Seeds of Life in Space (SOLIS) V. Methanol and acetaldehyde in the protostellar jet- driven shocks -B0 and B1 C. Codella1,2, C. Ceccarelli2,1, E. Bianchi2, N. Balucani3,2,1, L. Podio1, P. Caselli4, S. Feng5,6,7, B. Lefloch2, A. López-Sepulcre2,8, R. Neri8, S. Spezzano4 and M. De Simone2 1 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France; 3 Dipartimento di Chimica, Biologia e Biotecnologie, Via Elce di Sotto 8, 06123 Perugia, Italy; 4 Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany; 5 National Astronomical Observatory of China, Datun Road 20, Chaoyang, Beijing, 100012, P. R. China; 6 CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, P. R. China; 7 National Astronomical Observatory of Japan, 2 Chome-21-1 Osawa, Mitaka-shi, Tokyo-to 181-0015,

12 Japan; 8 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406, Saint-Martin d’Hères, France E-mail contact: codella at arcetri.astro.it Context: It is nowadays clear that a rich organic chemistry takes place in protostellar regions. However, the processes responsible for it, i.e. the dominant formation routes to interstellar complex organic molecules, are still source of debate. Two paradigms have been evoked: the formation of these molecules on the interstellar dust mantles or/and their formation in the gas-phase from simpler species previously synthetised on the dust mantles. Aims: In the past, observations of protostellar shocks have been able to set constraints on the formation route of formamide (NH2CHO), exploiting its observed spatial distribution and comparison with astrochemical model predic- tions. In this work, we follow the same strategy to study the case of acetaldehyde (CH3CHO). Methods: To this end, we used the data obtained with the IRAM NOEMA interferometer in the framework of the Large Program SOLIS to image the B0 and B1 shocks along the L1157 blueshifted outflow methanol (CH3OH) and acetaldehyde line emission. Results: We imaged six CH3OH and eight CH3CHO lines which cover upper level energies up to ∼ 30 K. Both species trace the B0 molecular cavity as well as the northern B1 portion, i.e. the regions where the youngest shocks (∼ 1000 yr) occurred. The CH3OH and CH3CHO emission peaks towards the B1b clump, where we measured the following column densities and relative abundances: 1.3 × 1016 cm−2 and 6.5 × 10−6 (methanol), and 7 × 1013 cm−2 and 3.5 −8 × 10 (acetaldehyde). We carried out a non-LTE LVG analysis of the observed CH3OH line: the average kinetic 5 −3 temperature and density of the emitting gas are Tkin ∼ 90 K and nH2 ∼ 4 × 10 cm , respectively. The CH3OH and CH3CHO abundance ratio towards B1b is 190, varying by less than a factor 3 throughout the whole B0–B1 structure. Conclusions: The comparison of astrochemical model predictions with the observed methanol and acetaldehyde spa- tial distribution does not allow to distinguish whether acetaldehyde is formed on the grain mantles or rather on the gas-phase, as its gas-phase formation, dominated by the reaction of ethyl radical (CH3CH2) with atomic oxygen, is very fast. Observations of acetaldehyde in younger shocks, e.g. ∼ 102 yr old, or/and of the ethyl radical, whose frequencies are not presently available, are necessary to settle the issue. Accepted by A&A http://arxiv.org/pdf/2001.00217

Catastrophic events in protoplanetary disks and their observational manifestations Tatiana V. Demidova1 and Vladimir P. Grinin2 1 Crimean Astrophysical Observatory, Nauchny, Crimea, Russia; 2 Pulkovo Observatory of the Russian Academy of Sciences, St. Petersburg, Russia E-mail contact: proxima1 at list.ru Observations of protoplanetary disks with high angular resolution using an ALMA interferometer showed that ring- shaped structures are often visible in their images, indicating strong disturbances in the disks. The mechanisms of their formation are vividly discussed in the literature. This article shows that the formation of such structures can be the result of destructive collisions of large bodies (planetesimals and planetary embryos) accompanied by the formation of a large number of dust particles, and the subsequent evolution of a cloud of dust formed in this way. Accepted by Astrophysical Journal Letters https://arxiv.org/pdf/1912.12328

Astrochemical Bistability: Autocatalysis in Oxygen Chemistry Gwenaelle Dufour1,2,3 and Steven Charnley1 1 Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; 2 De- partment of Physics, Catholic University of America, Washington, DC 20064, USA; 3 Leiden Observatory, Leiden University, Leiden, The Netherlands E-mail contact: gwenaelle.c.dufour at nasa.gov The origin of bistable solutions in the kinetic equations describing the chemistry of dense interstellar clouds is explained

13 as being due to the autocatalysis and feedback of oxygen nuclei from the oxygen dimer (O2). We identify four autocatalytic processes that can operate in dense molecular clouds, driven respectively by reactions of H+, He+, C+ + and S with O2. We show that these processes can produce the bistable solutions found in previous studies, as well as the dependence on various model parameters such as the helium ionization rate, the sulfur depletion and the + H3 electron recombination rate. We also show that ion-grain neutralizations are unlikely to affect the occurrence of bistability in dense clouds. It is pointed out that many chemical models of astronomical sources should have the potential to show bistable solutions. Accepted by ApJ https://doi.org/10.3847/1538-4357/ab4e9c

Thermal instability revisited Samuel Falle1, Christopher Wareing2 and J.M. Pittard2 1 School of Mathematics, University of Leeds, Leeds, LS2 9JT, UK; 2 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK E-mail contact: S.A.E.G.Falle at leeds.ac.uk Field’s linear analysis of thermal instability is repeated using methods related to Whitham’s theory of wave hierarchies, which brings out the physically relevant parameters in a much clearer way than in the original analysis. It is also used for the stability of non-equilibrium states and we show that for gas cooling behind a shock, the usual analysis is only quantitatively valid for shocks that are just able to trigger a transition to the cold phase. A magnetic field can readily be included and we show that this does not change the stability criteria. By considering steady shock solutions, we show that almost all plausible initial conditions lead to a magnetically dominated state on the unstable part of the equilibrium curve. These results are used to analyse numerical calculations of perturbed steady shock solutions and of shocks interacting with a warm cloud. Accepted by MNRAS https://arxiv.org/pdf/2001.01092

Mirror, mirror on the outflow cavity wall. Near-infrared CO overtone disc emission of the high-mass YSO IRAS 11101-5829 R. Fedriani1,2, A. Caratti o Garatti1,2, M. Koutoulaki1,2, R. Garcia-Lopez1,2 A. Natta1 R. Cesaroni3 R. Oudmaijer4 D. Coffey2,1 T. Ray1 B. Stecklum5 1 Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2, Ireland; 2 University College Dublin, School of Physics, Belfield, Dublin 4, Ireland; 3 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy 4 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK 5 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany E-mail contact: fedriani at cp.dias.ie Aims: The inner regions of high-mass protostars are often invisible in the near-infrared, obscured by thick envelopes and discs. We aim to investigate the inner gaseous disc of IRAS 11101-5829 through scattered light from the outflow cavity walls. Methods: We observed the immediate environment of the high-mass young stellar object IRAS 11101-5829 and the closest knots of its jet, HH135-136, with the integral field unit VLT/SINFONI. We also retrieved archival data from the high-resolution long-slit spectrograph VLT/X-shooter. We analysed imaging and spectroscopic observations to discern the nature of the near-infrared CO emission. Results: We detect the first three bandheads of the υ = 2 − 0 CO vibrational emission for the first time in this object. It is coincident with continuum and Brγ emission and extends up to ∼ 10000 au to the north-east and ∼ 10000 au to the south-west. The line profiles have been modelled as a Keplerian rotating disc assuming a single ring in local thermodynamic equilibrium. The model output gives a temperature of ∼ 3000 K, a CO column density 22 −2 −1 of ∼ 1 × 10 cm , and a projected Keplerian velocity vK sin idisc ∼ 25kms , which is consistent with previous modelling in other high-mass protostars. In particular, the low value of vK sin idisc suggests that the disc is observed

14 almost face-on, whereas the well-constrained geometry of the jet imposes that the disc must be close to edge-on. This apparent discrepancy is interpreted as the CO seen reflected i! n the mirror of the outflow cavity wall. Conclusions: From both jet geometry and disc modelling, we conclude that all the CO emission is seen through reflection by the cavity walls and not directly. This result implies that in the case of highly embedded objects, as for many high-mass protostars, line profile modelling alone might be deceptive and the observed emission could affect the derived physical and geometrical properties; in particular the inclination of the system can be incorrectly interpreted. Accepted by Astronomy & Astrophysics https://arxiv.org/pdf/2001.00369.pdf

First Resolved Dust Continuum Measurements of Individual Giant Molecular Clouds in the Andromeda Jan Forbrich1,2, Charles J. Lada2, Sébastien Viaene3,1 and Glen Petitpas2 1 Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK; 2 Center for Astrophysics | Harvard & Smithsonian, 60 Garden St, MS 72, Cambridge, MA 02138, USA; 3 Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281, 9000, Gent, Belgium E-mail contact: j.forbrich at herts.ac.uk In our local Galactic neighborhood, molecular clouds are best studied using a combination of dust measurements, to determine robust masses, sizes and internal structures of the clouds, and molecular-line observations to determine cloud kinematics and chemistry. We present here the first results of a program designed to extend such studies to nearby beyond the Magellanic Clouds. Utilizing the wideband upgrade of the Submillimeter Array (SMA) at 230 GHz we have obtained the first continuum detections of the thermal dust emission on sub-GMC scales (∼ 15 pc) within the Andromeda galaxy (M 31). These include the first resolved continuum detections of dust emission from individual GMCs beyond the Magellanic Clouds. Utilizing a powerful capability of the SMA, we simultaneously recorded CO(2-1) emission with identical (u, v) coverage, and calibration, enabling the first measurements of the CO conversion factor, α CO(2−1), toward individual GMCs across an external galaxy. Our direct measurement ′ −1 2 −1 yields an average CO–to–dust mass conversion factor of αCO−dust = 0.042 ± 0.018 M⊙ (K km s pc ) for the J =2 − 1 transition. This value does not appear to vary with galactocentric radius. Assuming a constant gas-to-dust −1 2 −1 ratio of 136, the resulting αCO = 5.7 ± 2.4 M⊙ (K km s pc ) for the 2-1 transition is in excellent agreement with that of Milky Way GMCs, given the uncertainties. Finally, using the same analysis techniques, we compare our results with observations of the local Orion molecular clouds, placed at the distance of M 31 and simulated to appear as they would if observed by the SMA. Accepted by ApJ https://arxiv.org/pdf/2001.02914

When H II Regions are Complicated: Considering Perturbations from Winds, Radiation Pressure, and Other Effects Sam Geen1,2, Eric Pellegrini1, Rebekka Bieri3 and Ralf Klessen1,4 1 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 2 Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands; 3 Max-Planck-Institute for Astrophysics, Karl-Schwartzschild-Strasse 1, Garching, Germany; 4 Universität Heidelberg, Interdisziplinäres Zentrum fur Wissenschaftliches Rechnen, INF 205, 69120, Heidelberg, Germany E-mail contact: s.t.geen at uva.nl We explore to what extent simple algebraic models can be used to describe HII regions when winds, radiation pressure, gravity and photon breakout are included. We a) develop algebraic models to describe the expansion of photoionised HII regions under the influence of gravity and accretion in power-law density fields with ρ ∝ r−w, b) determine when terms describing winds, radiation pressure, gravity and photon breakout become significant enough to affect the dynamics of the HII region where w = 2, and c) solve these expressions for a set of physically-motivated conditions.

15 We find that photoionisation feedback from massive stars is the principal mode of feedback on molecular cloud scales, driving accelerating outflows from molecular clouds in cases where the peaked density structure around young massive stars is considered at radii between ∼0.1 and 10-100 pc. Under a large range of conditions the effect of winds and radiation on the dynamics of HII regions is around 10% of the contribution from photoionisation. The effect of winds and radiation pressure are most important at high densities, either close to the star or in very dense clouds such as those in the Central Molecular Zone of the Milky Way. Out to ∼0.1 pc they are the principal drivers of the HII region. Lower make the relative effect of photoionisation even stronger as the ionised gas temperature is higher. Accepted by MNRAS https://arxiv.org/pdf/1906.05649

A HARPS RV search for planets around young nearby stars A. Grandjean1, A.-M. Lagrange1, M. Keppler2, N. Meunier1, L. Mignon1 et al. 1 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany E-mail contact: Antoine.Grandjean1 at univ-grenoble-alpes.fr Young nearby stars are good candidates in the search for planets with both radial velocity (RV) and direct imaging techniques. This, in turn, allows for the computation of the giant planet occurrence rates at all separations. The RV search around young stars is a challenge as they are generally faster rotators than older stars of similar spectral types and they exhibit signatures of magnetic activity (spots) or pulsation in their RV time series. Specific analyses are necessary to characterize, and possibly correct for, this activity. Our aim is to search for planets around young nearby stars and to estimate the giant planet (GP) occurrence rates for periods up to 1000 days. We used the HARPS spectrograph on the 3.6m telescope at La Silla Observatory to observe 89 A–M young (<600 Myr) stars. We used our SAFIR (Spectroscopic data via Analysis of the Fourier Interspectrum Radial velocities ) software to compute the RV and other spectroscopic observables. Then, we computed the companion occurrence rates on this sample. We confirm the binary nature of HD177171, HD181321 and HD186704. We report the detection of a close low mass stellar companion for HIP36985. No planetary companion was detected. We obtain upper limits on the GP (<13 MJup) and +3 BD (13–80 MJup) occurrence rates based on 83 young stars for periods less than 1000 days, which are set, 2−2% and +3 1−1%. Accepted by A&A http://arxiv.org/pdf/1912.02741

Tracing shock type with chemical diagnostics: an application to L1157 T.A. James1, S. Viti1, J. Holdship1, and I. Jimenez-Serra2 1 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK; 2 Centro de Astrobiologia (CSIC, INTA), Ctra. de Ajalvir, km. 4, Torrejón de Ardoz, 28850 Madrid, Spain E-mail contact: tjames at star.ucl.ac.uk Aims. The physical structure of a shock wave may take a form unique to its shock type, implying that the chemistry of each shock type is unique as well. We aim to investigate the different chemistries of J-type and C-type shocks in order to identify unique molecular tracers of both shock types. We apply these diagnostics to the protostellar outflow L1157 to establish whether the B2 clump could host shocks exhibiting type-specific behaviour. Of particular interest is the L1157-B2 clump, which has been shown to exhibit bright emission in S-bearing species and HNCO. Methods. We simulate, using a parameterised approach, a planar, steady-state J-type shock wave using UCLCHEM. We compute a grid of models using both C-type and J-type shock models to determine the chemical abundance of shock-tracing species as a function of distance through the shock and apply it to the L1157 outflow. We focus on known shock-tracing molecules such as H2O, HCN, and CH3OH. Results. We find that a range of molecules including H2O and HCN have unique behaviour specific to a J-type shock, but that such differences in behaviour are only evident at low vs and low nH. We find that CH3OH is enhanced by shocks and is a reliable probe of the pre-shock gas density. However, we find no difference between its gas-phase

16 abundance in C-type and J-type shocks. Finally, from our application to L1157, we find that the fractional abundances within the B2 region are consistent with both C-type and J-type shock emission. Accepted by A&A http://arxiv.org/pdf/1912.03721

Mass constraints for 15 protoplanetary disks from HD 1–0 M. Kama1,2, L. Trapman3, D. Fedele4, S. Bruderer5, M.R. Hogerheijde2,6 et al. 1 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 2 Tartu Observatory, Observatooriumi 1, Tõravere 61602, Tartu, Estonia; 3 Leiden Observatory, Leiden University, Niels Bohrweg 2, NL- 2333 CA Leiden, The Netherlands; 4 INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 5 Max-Planck-institute für extraterrestrische Physic, Giessenbachstraße, D-85748 Garching bei München, Germany; 6 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1090 GE Amsterdam, The Netherlands E-mail contact: mkama at ast.cam.ac.uk Hydrogen deuteride (HD) rotational line emission can provide reliable protoplanetary disk gas mass measurements, but it is difficult to observe and detections have been limited to three T-Tauri disks. No new data have been available since the Herschel Space Observatory mission ended in 2013. We set out to obtain new disk gas mass constraints by analysing upper limits on HD 1–0 emission in Herschel/PACS archival data from the DIGIT key programme. With a focus on the Herbig Ae/Be disks, whose stars are more luminous than T Tauris, we determine upper limits for HD in data previously analysed for its line detections. Their significance is studied with a grid of models run with the DALI physical-chemical code, customised to include deuterium chemistry. Nearly all the disks are constrained to Mgas ≤ 0.1 M⊙, ruling out global gravitational instability. A strong constraint is obtained for the HD 163296 disk mass, Mgas ≤ 0.067 M⊙, implying ∆g/d ≤ 100. This HD-based mass limit is towards the low end of CO-based mass estimates for the disk, highlighting the large uncertainty in using only CO and suggesting that gas-phase CO depletion in HD 163296 is at most a factor of a few. The Mgas limits for HD 163296 and HD 100546, both bright disks with massive candidate protoplanetary systems, suggest disk-to-planet mass conversion efficiencies of Mp/(Mgas + Mp) ≈ 10 to 40% for present-day values. Near-future observations with SOFIA/HIRMES will be able to detect HD in the brightest Herbig Ae/Be disks within 150 pc with ≈10h integration time. Accepted by A&A http://arxiv.org/pdf/1912.11883

Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model and Core Formation of FeSt 1-457 Ryo Kandori1, Kohji Tomisaka2, Masao Saito2, Motohide Tamura1,2,3, Tomoaki Matsumoto4, Ryo Tazaki5, Tetsuya Nagata6, Nobuhiko Kusakabe1, Yasushi Nakajima7, Jungmi Kwon3, Takahiro Nagayama8 and Ken’ichi Tatematsu2 1 Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 4 Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160; 5 Astronomical Institute, Graduate School of Science Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai 980-8578, Japan; 6 Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; 7 Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601, Japan; 8 Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan E-mail contact: r.kandori at nao.ac.jp Observational data for the hourglass-like magnetic field toward the starless dense core FeSt 1-457 were compared with a flux freezing magnetic field model (Myers et al. 2018). Fitting of the observed plane-of-sky magnetic field using the flux freezing model gave a residual angle dispersion comparable with the results based on a simple three-dimensional parabolic model. The best-fit parameters for the flux freezing model were a line-of-sight magnetic inclination angle ◦ ◦ of γmag = 35 ± 15 and a core center to ambient (background) density contrast of ρc/ρbkg = 75. The initial density

17 −3 for core formation (ρ0) was estimated to be ρc/75 = 4670 cm , which is about one order of magnitude higher than the expected density (∼ 300 cm−3) for the inter-clump medium of the Pipe Nebula. FeSt 1-457 is likely to have been formed from the accumulation of relatively dense gas, and the relatively dense background column density of AV ≃ 5 mag supports this scenario. The initial radius (core formation radius) R0 and the initial magnetic field strength B0 were obtained to be 0.15 pc (1.64R) and 10.8−14.6 µG, respectively. We found that the initial density ρ0 is consistent with the mean density of the nearly critical magnetized filament with magnetic field strength B0 and radius R0. The relatively dense initial condition for core formation can be naturally understood if the origin of the core is the fragmentation of magnetized filaments. Accepted by ApJ https://arxiv.org/pdf/1912.02935

Distortion of Magnetic Fields in the Dense Core CB81 (L1774, Pipe 42) in the Pipe Nebula Ryo Kandori1, Motohide Tamura1,2,3, Masao Saito3, Kohji Tomisaka3, Tomoaki Matsumoto4, Ryo Tazaki5, Tetsuya Nagata6, Nobuhiko Kusakabe1, Yasushi Nakajima7, Jungmi Kwon2, Takahiro Nagayama8 and Ken’ichi Tatematsu3 1 Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 3 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160; 5 Astronomical Institute, Graduate School of Science, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai 980-8578, Japan; 6 Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; 7 Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601, Japan; 8 Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan E-mail contact: r.kandori at nao.ac.jp The detailed magnetic field structure of the starless dense core CB81 (L1774, Pipe 42) in the Pipe Nebula was determined based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains in the core. The magnetic fields pervading CB81 were mapped using 147 stars and axisymmetrically distorted hourglass-like fields were identified. On the basis of simple 2D and 3D magnetic field modeling, the magnetic inclination angles in the plane-of-sky and line-of-sight directions were determined to be 4◦ ± 8◦ and 20◦ ± 20◦, respectively. The total magnetic field strength of CB81 was found to be 7.2 ± 2.3 µG. Taking into account the effects of thermal/turbulent pressure and magnetic fields, the critical mass of CB81 was calculated to be Mcr =4.03 ± 0.40 M⊙, which is close to the observed core mass of Mcore =3.37 ± 0.51 M⊙. We thus conclude that CB81 is in a condition close to the critical state. In addition, a spatial offset of 92′′ was found between the center of magnetic field geometry and the dust extinction distribution; this offset structure could not have been produced by self-gravity. The data also indicate a linear relationship between polarization and extinction up to AV ∼ 30 mag going toward the core center. This result confirms that near-infrared polarization can accurately trace the overall magnetic field structure of the core. Accepted by Astrophysical Journal https://arxiv.org/pdf/1912.10029

ALMA and NACO observations towards the young exoring transit system J1407 (V1400 Cen) Matthew Kenworthy1, Pamela Klaassen2, Michiel Min3, Nienke van der Marel4,5, Alexander Bohn1, Mihkel Kama6, Amaury Triaud7, Antonio Hales8,9, Jacqueline Monkiewicz10, Erin Scott11 and Eric Mamajek12,13 1 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands; 2 UK Astronomy Technol- ogy Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK; 3 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands; 4 Herzberg Astronomy & Astrophysics Pro- grams, National Research Council of Canada Herzberg, 5071 West Saanich Rd, Victoria, BC, V9E 2E7, Canada; 5

18 Department of Physics & Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada; 6 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 OHA, UK; 7 School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; 8 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475.; 9 Atacama Large Millimeter/Submillimeter Array, Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago; 10 School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA; 11 Chinese Academy of Sciences, 52 Sanlihe Road, Xicheng District, 100864 Beijing, China; 12 Jet Propulsion Laboratory, California Institute of Technology, M/S 321-100, 4800 Oak Grove Drive, Pasadena, CA 91109, USA; 13 Department of Physics & Astronomy, University of Rochester, Rochester, NY 14627, USA E-mail contact: kenworthy at strw.leidenuniv.nl Our aim was to directly detect the thermal emission of the putative exoring system responsible for the complex deep transits observed in the light curve for the young Sco-Cen star 1SWASP J140747.93-394542.6 (V1400 Cen, hereafter J1407), confirming it as the occulter seen in May 2007, and to determine its orbital parameters with respect to the star. We used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the field centred on J1407 in the 340 GHz (Band 7) continuum in order to determine the flux and astrometric location of the ring system relative to the star. We used the VLT/NACO camera to observe the J1407 system in March 2019 and to search for the central planetary mass object at thermal infrared wavelengths. We detect no point source at the expected location of J1407, and derive an upper limit 3σ level of 57.6 µJy. There is a point source detected at an angular separation consistent with the expected location for a free-floating ring system that occulted J1407 in May 2007, with a flux of 89 µJy consistent with optically thin dust surrounding a massive substellar companion. At 3.8 microns with the NACO camera, we detect the star J1407 but no other additional point sources within 1.3 arcseconds of the star, with a lower bound on the sensitivity of 6MJup at the location of the ALMA source, and down to 4MJup in the sky background limit. The ALMA upper limit at the location of J1407 implies that a hypothesised bound ring system is composed of dust smaller than 1 mm in size, implying a young ring structure. The detected ALMA source has multiple interpretations, including: (i) it is an unbound substellar object surrounded by warm dust in Sco-Cen with an upper mass limit of 6MJup, or (ii) it is a background galaxy. Accepted by Astronomy and Astrophysics https://arxiv.org/pdf/1912.03314

V346 Nor: the post-outburst life of a peculiar young eruptive star Á. Kóspál1,2, Zs. M. Szabó1,3, P. Ábrahám1, S. Kraus4, M. Takami5, P. W. Lucas6, C. Contreras Peña4 and A. Udalski7 1 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege M. út 15-17, 1121 Bu- dapest, Hungary; 2 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 3 Eötvös Loránd University, Department of Astronomy, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary; 4 School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK; 5 Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.; 6 Centre for Astrophysics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK; 7 Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland E-mail contact: kospal at konkoly.hu FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased accretion is often accompanied by collimated jets and energetic, large-scale molecular outflows. The extra heating during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar material, affecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010 due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradual re-brightening of V346 Nor, with its Ks-band brightness only 1.5 mag below the outburst brightness level. Our VLT/XSHOOTER spectroscopic observations display several strong forbidden emission lines towards the source from various metals and molecular hydrogen, suggesting the launch of a new jet. Our N-band spectrum obtained with VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar medium has changed in the post-outburst period compared to peak brightness.

19 Accepted by Astrophysical Journal https://arxiv.org/pdf/1912.03753.pdf

Ring Morphology with Dust Coagulation in Protoplanetary Disks J.T. Laune1, Hui Li1, Shengtai Li1, Ya-Ping Li1, Levi G. Walls2 et al. 1 Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; 2 School of Physics and Astronomy, University of Minnesota, 116 Church Street, Minneapolis, MN 55455, USA E-mail contact: jl3929 at cornell.edu Tidal interactions between the embedded planets and their surrounding protoplanetary disks are often postulated to produce the observed complex dust substructures, including rings, gaps, and asymmetries. In this Letter, we explore the consequences of dust coagulation on the dust dynamics and ring morphology. Coagulation of dust grains leads to dust size growth which, under typical disk conditions, produces faster radial drifts, potentially threatening the dust ring formation. Utilizing 2D hydrodynamical simulations of protoplanetary disks which include a full treatment of dust coagulation, we find that if the planet does not open a gap quickly enough, the formation of an inner ring is impeded due to dust coagulation and subsequent radial drift. Furthermore, we find that a “buildup” of sub-mm sized grains often appears in the dust emission at the outer edge of the dust disk. Accepted by ApJL http://arxiv.org/pdf/1912.11178

Surveying the Giant HII Regions of the Milky Way with SOFIA: II. M17 Wanggi Lim1, James M. De Buizer1 and James T. Radomski1 1 SOFIA-USRA, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035, USA E-mail contact: wlim at usra.edu We present our second set of results from our mid-infrared imaging survey of Milky Way Giant HII regions. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy to obtain 20 and 37 µm images of the central ∼10′×10′ area of M17. We investigate the small- and large-scale properties of M 17 using our data in conjunction with previous multi-wavelength observations. The spectral energy distributions of individual compact sources were constructed with Spitzer-IRAC, SOFIA-FORCAST, and Herschel-PACS photometry data and fitted with massive young stellar object (MYSO) models. Seven sources were found to match the criteria for being MYSO candidates, four of which are identified here for the first time, and the stellar mass of the most massive object, UC 1, is determined to be 64 M⊙. We resolve the extended mid-infrared emission from the KW Object, and suggest that the angle of this extended emission is influenced by outflow. IRS 5 is shown to decrease in brightness as a function of wavelength from the mid- to far-infrared, and has several other indicators that point to it being an intermediate mass Class II object and not a MYSO. We find that the large-scale appearance of emission in M17 at 20 µm is significantly affected by contamination from the [SIII] emission line from the ionized gas of the Giant HII region. Finally, a number of potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M 17 is likely younger than the northern bar. Accepted by ApJ https://arxiv.org/pdf/1912.02855

The Column Density Structure of Orion A Depicted by N-PDF Yuehui Ma1,2, Hongchi Wang1, Chong Li1,2 and Ji Yang1 1 Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210033, China; 2 University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, China E-mail contact: mayh at pmo.ac.cn

20 We have conducted a large-field simultaneous survey of 12CO, 13CO, and C18O J =1−0 emission toward the Orion A giant molecular cloud (GMC) with a sky coverage of ∼ 4.4 deg2 using the PMO-13.7 m millimeter-wavelength telescope. We use the probability distribution function of the column density (N-PDF) to investigate the distribution of molecular 13 hydrogen in the Orion A GMC. The H2 column density, derived from the CO emission, of the GMC is dominated by log-normal distribution in the range from ∼4×1021 to ∼1.5×1023 cm−2 with excesses both at the low-density and high-density ends. The excess of the low-density end is possibly caused by an extended and low-temperature (∼10 K) component with velocities in the range of 5−8 km s−1. Compared with the northern sub-regions, the southern 22 −2 sub-regions of the Orion A GMC contain less gas with column density in NH2 > 1.25 × 10 cm . The dispersions of the N-PDFs of the sub-regions are found to correlate with the evolutionary stages of the clouds across the Orion A GMC. The structure hierarchy of Orion A GMC is explored with the DENDROGRAM algorithm, and it is found that the GMC is composed of two branches. All structures except one in the tree have virial parameters less than 2, indicating self-gravity is important on the spatial scales from ∼0.3 to ∼4 pc. Although power-laws and departures from log-normal distributions are found at the high-density end of N-PDFs of active star-forming regions, the N-PDFs of structures in the Orion A GMC are predominantly log-normal on scales from R∼0.4 to 4 pc. Accepted by Research in Astronomy and Astrophysics http://arxiv.org/pdf/1912.06984

Spectral library of age-benchmark low-mass stars and brown dwarfs E. Manjavacas1,2, N. Lodieu3,4, V.J.S. Béjar3,4, M.R. Zapatero-Osorio5, S. Boudreault6, M. Bonnefoy7 1 W.M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela, HI 96743, USA; 2 Department of Astronomy/Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ, 85721, USA; 3 Instituto de Astrofísica de Canarias, C/ Vía Láctea, s/n, E38205, La Laguna (Tenerife), Spain; 4 Dpt. de Astrofísica, Univ. de La Laguna, Avda. Astrofísico Francisco Sánchez s/n, 38206, La Laguna (Tenerife), Spain; 5 Centro de Astrobiología (CSIC-INTA), Crta. Ajalvir km 4, E-28850 Torrejón de Ardoz, Madrid, Spain; 6 Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany; 7 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France E-mail contact: emanjavacas at keck.hawaii.edu In the past years, some extremely red brown dwarfs were found. They were believed to have low , but many of their spectral characteristics were similar to those of high surface gravity brown dwarfs, showing that youth (or low surface gravity) spectral characteristics are poorly understood. We aim to test surface gravity indicators in late-M and early-L spectra using data obtained with the X-shooter spectrograph at the . We selected a benchmark sample of brown dwarfs members of ChamaeleonI (∼2 Myr), Upper Scorpius (5–10 Myr), Pleiades (132±27 Myr), and Praesepe (590–790 Myr) with well-constrained ages, and similar metallicities. We provided a consistent spectral classification of the sample in the optical and in the near-infrared. We measured the equivalent widths of their alkali lines, finding that they have a moderate correlation with age, especially for objects with spectral types M8 and later. We used spectral indices defined in the literature to estimate surface gravity, finding that their gravity assignment is accurate for 75% of our sample. We investigated the correlation between red colours and age, finding that after ∼10 Myr, the colour does not change significantly for our sample with spectral types M6.0– L3.0. In this case, red colours might be associated with circumstellar disks, ring structures, extinction, or viewing angle. Finally, we calculated the bolometric luminosity, and J and K bolometric corrections for our sample. We found that six objects are overluminous compared to other members of the same association. Those objects are also flagged as binary candidates by the survey. Accepted by MNRAS http://arxiv.org/pdf/1912.02806

Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639 Mateusz Olech1, Marian Szymczak1, Pawel Wolak1, Eric Gérard2 and Anna Bartkiewicz1 1 Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka

21 5, 87-100 Torun, Poland; 2 GEPI, UMR 8111, CNRS and Observatoire de Paris, 5 Place J.Janssen, 92195 Meudon Cedex, France E-mail contact: olech at astro.umk.pl Periodic flares of maser emission are thought to be induced either by variations of the seed photon flux in young binary systems or the pump rate regulated by stellar and accretion luminosities. We seek to study the variability of four maser transitions of three different species in G107.298+5.639 to constrain the dominant mechanism of periodic flares. Light curves of the 6.7 GHz methanol and 22.2 GHz water vapour maser were obtained with the Torun 32m radio telescope over 39 and 34 cycles, respectively. The target was also monitored at the 1.6 GHz hydroxyl transitions with the NanŊay radio telescope over 13 cycles. All these maser lines were imaged using VLBI arrays. The study confirms alternating flares of the methanol and water masers with a period of 34.4d and reveals the synchronised behaviour of the methanol and hydroxyl masers in this source. The observed spatial distribution of the methanol maser cloudlets and the measured time delays of the flares of individual features imply a ring-like structure of radius 240au and thickness 30au. Internal proper motions indicate that the velocity of methanol cloudlets is dominated by a disc-wind component of about 5km/s. The methanol emission detected during only one VLBI observation is located in a region about 550au from a central star, which also exhibits OH maser flares. The erratic appearance of methanol features can be related to a powering object of relatively low luminosity which, during some variability cycles, can excite molecules only in the nearest part of the disc. A careful analysis of the maser and infrared light curves reveal a strong correlation between the 6.7 GHz line and the infrared flux densities supporting a radiative pumping of the maser. The synchronised behaviour of the hydroxyl and methanol transitions indicates a common pumping mechanism for the periodic flares of G107.298+5.639. Accepted by Astronomy and Astrophysics https://arxiv.org/pdf/2001.01625

Large scale star formation in Auriga region A.K. Pandey1, Saurabh Sharma1, N. Kobayashi2,3, Y. Sarugaku3 and K. Ogura4 1 Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263 002, India; 2 Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 Kiso Observatory, School of Science, University of Tokyo, Mitake-mura, Kiso-gun, Nagano 397-0101, Japan; 4 Kokugakuin University, Higashi, Shibuya-ku, Tokyo 150-8440, Japan E-mail contact: pandey at aries.res.in New observations in the VI bands along with archival data from the 2MASS and WISE surveys have been used to generate a catalog of young stellar objects (YSOs) covering an area of about 6◦ × 6◦ in the Auriga region centered at l ∼ 173◦ and b ∼ 1◦.5. The nature of the identified YSOs and their spatial distribution are used to study the star formation in the region. The distribution of YSOs along with that of the ionized and molecular gas reveals two ring-like structures stretching over an area of a few degrees each in extent. We name these structures as Auriga Bubbles 1 and 2. The center of the Bubbles appears to be above the Galactic mid-plane. The majority of Class i YSOs are associated with the Bubbles, whereas the relatively older population, i.e., Class ii objects are rather randomly distributed. Using the minimum spanning tree analysis, we found 26 probable sub-clusters having 5 or more members. The sub-clusters are between ∼0.5 pc – ∼3 pc in size and are somewhat elongated. The star formation efficiency in most of the sub-cluster region varies between 5% – 20% indicating that the sub-clusters could be bound regions. The radii of these sub-clusters also support it. Accepted by MNRAS http://arxiv.org/pdf/1912.11789

Probing the early phases of high mass star formation with 6.7 GHz methanol masers Sonu Tabitha Paulson1, Jagadheep D. Pandian1 1 Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram 695547, Kerala, India

22 E-mail contact: sonutabitha.15 at res.iist.ac.in Methanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here a study of the spectral energy distributions of 320 6.7 GHz methanol masers chosen from the MMB catalogue, which fall in the Hi-GAL range (|l|≤ 60◦, |b|≤ 1◦). The spectral energy distributions are constructed from 870–70 µm using data from the ATLASGAL and Hi-GAL surveys. The emission from cold dust is modelled by a single grey body component fit. We estimate the clump properties such as mass, FIR luminosity and column density using the best fit parameters of the SED fits. Considering the Kauffman criteria for massive star formation, we find that all but a few maser hosts have the potential to harbour at least one high mass star. The physical properties of the methanol maser hosts are also discussed. The evolutionary stages of 6.7 GHz maser sources, explored using the mass luminosity diagram, suggests that they are predominantly associated with high mass stars with the majority being in the accretion phase. However, we observe a small number of sources that could possibly be related to intermediate or low-mass stars. Accepted by MNRAS http://arxiv.org/pdf/1912.06973

Formation of moon systems around giant planets: Capture and ablation of planetesimals as foundation for a pebble accretion scenario T. Ronnet1 and A. Johansen1 1 Department of Astronomy and Theoretical Physics, Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden E-mail contact: thomas.ronnet at astro.lu.se The four major satellites of Jupiter, known as the Galilean moons, and Saturn’s most massive satellite, Titan, are believed to have formed in a predominantly gaseous circum-planetary disk, during the last stages of formation of their parent planet. Pebbles from the protoplanetary disk are blocked from flowing into the by the positive pressure gradient at the outer edge of the planetary gap, so the gas drag assisted capture of planetesimals should be the main contributor to the delivery of solids onto circum-planetary disks. However, a consistent framework for the subsequent accretion of the moons remains to be built. Here we use numerical integrations to show that most planetesimals being captured within a circum-planetary disk are strongly ablated due to the frictional heating they experience, thus supplying the disk with small dust grains, whereas only a small fraction ‘survives’ their capture. We then construct a simple model of a circum-planetary disk supplied by ablation, where the flux of solids through the disk is at equilibrium with the ablation supply rate, and investigate the formation of moons in such disks. We show that the growth of satellites is driven mainly by accretion of the pebbles that coagulate from the ablated material. The pebble- accreting protosatellites rapidly migrate inward and pile up in resonant chains at the inner edge of the circum-planetary disk. We propose that dynamical instabilities in these resonant chains are at the origin of the different architectures of Jupiter’s and Saturn’s moon systems. The assembly of moon systems through pebble accretion can therefore be seen as a down-scaled manifestation of the same process that forms systems of super- and terrestrial-mass planets around solar-type stars and M-dwarfs. Accepted by A&A http://arxiv.org/pdf/1912.04765

The molecular outflow from R Mon Goran Sandell1, W. Vacca2, L. Bouscasse3 and R. Güsten3 1 University of Hawaii, Institute for Astronomy - Hilo, 640 N. Aohoku Place, Hilo, HI 96720, USA; 2 SOFIA Science Center, NASA Ames Research Center, USRA, MS 232-12, Building N232, PO Box 1, Moffett Field, CA 94035-0001, USA; 3 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany E-mail contact: gsandell at hawaii.edu We have mapped the young Herbig Be star R Mon in CO(3–2) and 13CO(3–2) with APEX in Chile and analyzed unpublished Herschel images. We find that R Mon is embedded in a small cloud with a gas temperature of ∼ 20 K

23 and a total mass of ∼ 70 M⊙. We confirm that R Mon drives a bipolar molecular outflow, which is blue-shifted north of R Mon. The blue-shifted outflow has excavated the molecular cloud north of R Mon, creating the reflection nebula NGC 2261 and filling it with high-velocity gas. At “high’ velocities the orientation of the outflow is approximately n-s, which agrees with the optical jet, suggesting that the accretion disk is e-w. The outflow velocities are modest, ± 9 km/s. The outflow is rather massive, ∼ 0.56 M⊙ in the blue-shifted outflow lobe. The outflow is completely optically thick in CO(3–2) towards R Mon, indicating that it’s envelope is ∼< 2,000 au. The mass of the accretion disk and surrounding envelope determined from an isothermal graybody fit is ∼ 0.34 M⊙. We estimate a mass loss rate −5 −1 −6 −1 of ∼ (1 - 3) × 10 M⊙ yr , corresponding to an accretion rate of (1 - 9) × 10 M⊙ yr . We find that R Mon has bolometric luminosity of < 1000 L⊙. R Mon is still in an active accretion phase, contributing to the observed luminosity. Hence R Mon cannot be a B0 star. It must be a late B star or even an early A star. Accepted by The Astrophysical Journal

Laboratory Experiments on the Motion of Dense Dust Clouds Niclas Schneider1 and Gerhard Wurm1 1 Faculty of Physics University of Duisburg-Essen Lotharstr. 1, 47057 Duisburg, Germany E-mail contact: niclas.schneider at uni-due.de In laboratory experiments, we study the motion of levitated, sedimenting clouds of sub-mm grains at low ambient pressure and at high solid-to-gas ratios ǫ. The experiments show a collective behavior of particles, i.e. grains in clouds settle faster than an isolated grain. In collective particle clouds, the sedimentation velocity linearly depends on ǫ and linearly depends on the particle closeness C. However, collective behavior only sets in at a critical value ǫcrit which linearly increases with the experiment Stokes number St. For St < 0.003 particles always behave collectively. For large Stokes numbers, large solid-to-gas ratios are needed to trigger collective behavior, e.g. ǫcrit =0.04 at St =0.01. Applied to protoplanetary disks, particles in dense environments will settle faster. In balance with upward gas motions (turbulent diffusion, convection) the thickness of the midplane particle layer will be smaller than calculated based on individual grains, especially for dust. For pebbles, large solid-to-gas ratios are needed to trigger instabilities based on back-reaction. Accepted by ApJL http://arxiv.org/pdf/1912.01714

The evolution of dust in discs influenced by external photoevaporation Andrew D. Sellek1, Richard A. Booth1 and Cathie J. Clarke1 1 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK E-mail contact: ads79 at cam.ac.uk Protoplanetary discs form and evolve in a wide variety of stellar environments and are accordingly exposed to a wide range of ambient far ultraviolet (FUV) field strengths. Strong FUV fields are known to drive vigorous gaseous flows from the outer disc. In this paper we conduct the first systematic exploration of the evolution of the solid component of discs subject to external photoevaporation. We find that the main effect of photoevaporation is to reduce the reservoir of dust at large radii and this leads to more efficient subsequent depletion of the disc dust due to radial drift. Efficient radial drift means that photoevaporation causes no significant increase of the dust to gas ratio in the disc. We show that the disc lifetime in both dust and gas is strongly dependent on the level of the FUV background and that the relationship between these two lifetimes just depends on the Shakura-Sunyaev α parameter, with the similar lifetimes observed for gas and dust in discs pointing to higher α values (∼ 10−2). On the other hand the distribution of observed discs in the plane of disc size versus flux at 850 µm is better reproduced by lower α (∼ 10−3). We find that photoevaporation does not assist rocky planet formation but need not inhibit mechanisms (such as pebble accretion at the water snow line) which can be effective sufficiently early in the disc’s lifetime (i.e. well within a Myr). Accepted by MNRAS https://arxiv.org/pdf/1912.06154

24 Characterising the i-band variability of YSOs over six orders of magnitude in timescale Darryl J. Sergison1, Tim Naylor1, S.P. Littlefair1,2, Cameron P.M. Bell1,3 and C.D.H. Williams1 1 School of Physics, University of Exeter, Exeter EX4 4QL; 2 Department of Physics & Astronomy, University of Sheffield, Sheffield S3 7RH; 3 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany E-mail contact: timn at astro.ex.ac.uk We present an i-band photometric study of over 800 young stellar objects in the OB association Cep OB3b, which samples timescales from 1 minute to ten years. Using structure functions we show that on all timescales (τ) there is a monotonic decrease in variability from Class I to Class II through the transition disc (TD) systems to Class III, i.e. the more evolved systems are less variable. The Class Is show an approximately power-law increase (τ 0.8) in variability from timescales of a few minutes to ten years. The Class II, TDs and Class III systems show a qualitatively different behaviour with most showing a power-law increase in variability up to a timescale corresponding to the rotational period of the star, with little additional variability beyond that timescale. However, about a third of the Class IIs show lower overall variability, but their variability is still increasing at 10 years. This behaviour can be explained if all Class IIs have two primary components to their variability. The first is an underlying roughly power-law variability spectrum, which evidence from the infrared suggests is driven by accretion rate changes. The second component is approximately sinusoidal and results from the rotation of the star. We suggest that the systems with dominant longer- timescale variability have a smaller rotational modulation either because they are seen at low inclinations or have more complex magnetic field geometries. We derive a new way of calculating structure functions for large simulated datasets (the “fast structure function”), based on fast Fourier transforms. Accepted by MNRAS http://arxiv.org/pdf/1912.01615

Effects of photoevaporation on protoplanetary disc ‘isochrones’ Alice Somigliana1, Claudia Toci2, Giuseppe Lodato1,2, Giovanni Rosotti3 and Carlo F. Manara4 1 Dipartimento di Fisica, Universitá degli Studi di Milano, Via Giovanni Celoria 16, I-20133 Milano, Italy; 2 INAF - Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milan, Italy; 3 Leiden Observatory, Leiden University, P.O. Box 9531, NL-2300 RA Leiden, the Netherlands; 4 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany E-mail contact: alice.somigliana at studenti.unimi.it Protoplanetary discs are the site of star and planet formation, and their evolution and consequent dispersal deeply affect the formation of planetary systems. In the standard scenario they evolve on timescales ∼Myr due to the viscous transport of angular momentum. The analytical self-similar solution for their evolution predicts also specific disc isochrones in the accretion rate – disc mass plane. However, photoevaporation by radiation emitted by the central star is likely to dominate the gas disc dispersal of the innermost region, introducing another (shorter) timescale for this process. In this paper, we include the effect of internal (X and EUV) photoevaporation on the disc evolution, finding numerical solutions for a population of protoplanetary discs. Our models naturally reproduce the expected quick dispersal of the inner region of discs when their accretion rates match the rate of photoevaporative mass loss, in line with previous studies. We find that photoevaporation preferentially removes the lightest discs in the sample. The net result is that, counter-intuitively, photoevaporation increases the average disc mass in the sample, by dispersing the lightest discs. At the same time, photoevaporation also reduces the mass accretion rate by cutting the supply of material from the outer to the inner disc. In a purely viscous framework, this would be interpreted as the result of a longer viscous evolution, leading to an overestimate of the disc age. Our results thus show that photoevaporation is a necessary ingredient to include when interpreting observations of large disc samples with measured mass accretion rates and disc masses. Photoevaporation leaves a characteristic imprint on the shape of the isochrone. Accurate data in the accretion rate – disc mass plane in the low disc mass region therefore give clues on the typical photoevaporation rate. Accepted by MNRAS http://arxiv.org/pdf/1912.05623

25 Mass Assembly of Stellar Systems and Their Evolution with the SMA (MASSES) Full Data Release Ian W. Stephens1, Tyler L. Bourke2,1, Michael M. Dunham3,1, Philip C. Myers1, Riwaj Pokhrel4, John J. Tobin5, Héctor G. Arce6, Sarah I. Sadavoy1, Eduard I. Vorobyov7,8, Jaime E. Pineda9, Stella S. R. Offner10, Katherine I. Lee1, Lars E. Kristensen11, Jes K. Jørgensen11, Mark A. Gurwell1 and Alyssa A. Goodman1 1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 2 SKA Organization, Jodrell Bank, Lower Withington, Macclesfield, Cheshire SK11 9FT, UK; 3 Department of Physics, State University of New York at Fredonia, 280 Central Ave, Fredonia, NY 14063, USA; 4 Department of Astronomy, University of Mas- sachusetts, Amherst, MA 01003, USA; 5 National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA; 6 Department of Astronomy, Yale University, New Haven, CT 06520, USA; 7 Research Institute of Physics, Southern Federal University, Stachki Ave. 194, Rostov-on-Don, 344090, Russia; 8 University of Vienna, Department of Astrophysics, Vienna, A-1180, Austria; 9 Max-Planck-Institut für extraterrestrische Physik, D-85748 Garching, Germany; 10 Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA; 11 Niels Bohr Institute and Center for Star and Planet Formation, Copenhagen University, DK-1350 Copenhagen K., Denmark E-mail contact: ian.stephens at cfa.harvard.edu We present and release the full dataset for the Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) survey. This survey used the Submillimeter Array (SMA) to image the 74 known protostars within the Perseus molecular cloud. The SMA was used in two array configurations to capture outflows for scales >30′′ (>9000 au) and to probe scales down to ∼1′′ (∼300au). The protostars were observed with the 1.3mm and 850 µm receivers simul- taneously to detect continuum at both wavelengths and molecular line emission from CO(2–1), 13CO(2–1), C18O(2–1), + + 13 + N2D (3–2), CO(3–2), HCO (4–3), and H CO (4–3). Some of the observations also used the SMA’s recently up- graded correlator, SWARM, whose broader bandwidth allowed for several more spectral lines to be observed (e.g., SO, + H2CO, DCO , DCN, CS, CN). Of the main continuum and spectral tracers observed, 84% of the images and cubes had emission detected. The median C18O(2–1) linewidth is ∼1.0kms−1, which is slightly higher than those measured with single-dish telescopes at scales of 3000–20,000au. Of the 74 targets, six are suggested to be first hydrostatic core candidates, and we suggest that L1451-mm is the best candidate. We question a previous continuum detection toward L1448 IRS2E. In the SVS 13 system, SVS 13A certainly appears to be the most evolved source, while SVS 13C appears to be hotter and more evolved than SVS 13B. The MASSES survey is the largest publicly available interferometric con- tinuum and spectral line protostellar survey to date, and is largely unbiased as it only targets protostars in Perseus. All visibility (uv) data and imaged data are publicly available at https://dataverse.harvard.edu/dataverse/full_MASSES/. Accepted by ApJS https://ui.adsabs.harvard.edu/pdf/2019ApJS..245...21S/abstract

Investigation of Chemical Differentiation among the NGC2264 Cluster-Forming Clumps Kotomi Taniguchi1,2, Adele Plunkett3, Eric Herbst1, Kazuhito Dobashi4, Tomomi Shimoikura5, Fumi- taka Nakamura6,7 and Masao Saito6,7 1 Departments of Astronomy and Chemistry, University of Virginia, Charlottesville, VA 22904, USA; 2 Department of Physics, Faculty of Science, Gakushuin University, 1-5-1, Mejiro, Toshima, Tokyo 171-8588, Japan; 3 National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA; 4 Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Nukuikitamachi, Koganei, Tokyo 184-8501, Japan; 5 Faculty of Social Informa- tion Studies, Otsuma Women’s University, Sanban-cho, Chiyoda, Tokyo 102-8357, Japan; 6 National Astronomical Observatory of Japan (NAOJ), Osawa, Mitaka, Tokyo 181-8588, Japan; 7 Department of Astronomical Science, School of Physical Science, SOKENDAI (The Graduate University for Advanced Studies), Osawa, Mitaka, Tokyo 181-8588, Japan E-mail contact: kotomi.taniguchi at gakushuin.ac.jp

We have carried out mapping observations of molecular emission lines of HC3N and CH3OH toward two massive cluster-forming clumps, NGC2264-C and NGC2264-D, using the Nobeyama 45-m radio telescope. We derive an I(HC3N)/I(CH3OH) integrated intensity ratio map, showing a higher value at clumps including 2MASS point sources

26 at the northern part of NGC2264-D. Possible interpretations of the I(HC3N)/I(CH3OH) ratio are discussed. We have + also observed molecular emission lines from CCS and N2H toward five positions in each clump. We investigate the + + N(N2H )/N(CCS) and N(N2H )/N(HC3N) column density ratios among the ten positions in order to test whether + they can be used as chemical evolutionary indicators in these clumps. The N(N2H )/N(CCS) ratio shows a very high + value toward a bright embedded IR source (IRS1), whereas the N(N2H )/N(HC3N) ratio at IRS1 is comparable with those at the other positions. These results suggest that UV radiation affects the chemistry around IRS1. We find + that there are positive correlations between these column density ratios and the excitation temperatures of N2H , which implies the chemical evolution of clumps. These chemical evolutionary indicators likely reflect the combination of evolution along the filamentary structure and evolution of each clump. Accepted by The Monthly Notices of the Royal Astronomical Society https://arxiv.org/pdf/1912.10766

Multi-scale dynamics in star-forming regions: the interplay between gravity and turbu- lence A. Traficante1,2, G.A. Fuller2, A. Duarte-Cabral3, D. Elia1, M.H. Heyer4, S. Molinari1, N. Peretto3, E. Schisano1 1 IAPS - INAF, via Fosso del Cavaliere, 100, I-00133 Roma, Italy; 2 Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK; 3 School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK; 4 Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA E-mail contact: alessio.traficante at iaps.inaf.it In this work we investigate the interplay between gravity and turbulence at different spatial scales and in different density regimes. We analyze a sample of 70 µm quiet clumps that are divided into three surface density bins and we compare the dynamics of each group with the dynamics of their respective filaments. The densest clumps form within the densest filaments on average, and they have the highest value of the velocity dispersion. The kinetic energy is transferred from the filaments down to the clumps most likely through a turbulent cascade, but we identify a critical value of the surface density, Σ ≈ 0.1 g cm2, above which the dynamics changes from being mostly turbulent-driven to mostly gravity-driven. The scenario we obtain from our data is a continuous interplay between turbulence and gravity, where the former creates structures at all scales and the latter takes the lead when the critical surface density threshold is reached. In the densest filaments this transition can occur at the parsec, or even larger scales, leading to a global collapse of the whole region and most likely to the formation of the massive objects. Accepted by MNRAS http://arxiv.org/pdf/1912.00031

Self-Induced Dust Traps Around Snow Lines in Protoplanetary Discs Arnaud Vericel1, Jean François Gonzalez1 1 Univ Lyon, Univ Claude Bernard Lyon 1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, France E-mail contact: arnaud.vericel at univ-lyon1.fr Dust particles need to grow efficiently from micrometre sizes to thousands of kilometres to form planets. With the growth of millimetre to meter sizes being hindered by a number of barriers, the recent discovery that dust evolution is able to create ‘self-induced’ dust traps shows promises. The condensation and sublimation of volatile species at certain locations, called snow lines, is also thought to be an important part of planet formation scenarios. Given that dust sticking properties change across a snow line, this raises the question: how do snow lines affect the self-induced dust trap formation mechanism? The question is particularly relevant with the multiple observations of the carbon monoxide (CO) snow line in protoplanetary discs, since its effect on dust growth and dynamics is yet to be understood. In this paper, we present the effects of snow lines in general on the formation of self-induced dust traps in a parameter study, then focus on the CO snow line. We find that for a range of parameters, a dust trap forms at the snow line where the dust accumulates and slowly grows, as found for the water snow line in previous work. We also find that,

27 depending on the grains sticking properties on either side of the CO snow line, it could either be a starting or braking point for dust growth and drift. This could provide clues to understand the link between dust distributions and snow lines in protoplanetary disc observations. Accepted by MNRAS http://arxiv.org/pdf/1912.02464

Observations of Orion Source I Disk and Outflow Interface Melvyn Wright1, Richard Plambeck1, Tomoya Hirota2, Adam Ginsburg3, Brett McGuire3 et al. 1 Radio Astronomy Lab, University of California, 501 Campbell Hall, Berkeley CA 94720-3441, USA; 2 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 3 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA E-mail contact: bmcguire at nrao.edu We imaged the continuum and molecular line emission from Orion Source I (SrcI) with up to 30 mas (12 AU) resolution at 43, 99, 223, and 340 GHz in an attempt to probe the structure and chemistry of the circumstellar disk and bipolar outflow associated with this high mass protostar. The continuum spectral index ranges from ∼2 along the midplane of the disk to ∼3 along the edges, consistent with dust that is optically thick in the midplane but becomes optically thin at the periphery. Salt (NaCl) emission is visible where the dust is optically thin; it provides a unique tracer of the velocity field within the disk. All other molecules that we have mapped — H2O, AlO, SiO, SiS, SO, and SO2 — appear to originate primarily in the bipolar outflow. The base of the outflow is corotating with the disk. SiS shows a filamentary structure that is most prominent along the edges of the outflow. The molecular distributions suggest that Si and Al released from dust grains in the disk react with oxygen derived from H2O to form SiO and AlO, and with SO and SO2 to form SiS. Accepted by ApJ http://arxiv.org/pdf/1912.08862

High-Resolution Near-Infrared Polarimetry and Sub-Millimeter Imaging of FS Tau A: Possible Streamers in Misaligned Circumbinary Disk System Yi Yang1,2, Eiji Akiyama3, Thayne Currie4, Ruobing Dong5, Jun Hashimoto1,2 et al. 1 Astrobiology Center, NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Institute for the Advancement of Higher Education, Hokkaido University, Kita 17, Nishi 8, Kita-ku, Sapporo, Hokkaido, 060-0817, Japan; 4 Subaru Telescope, NAOJ, NINS, 650 North A’ohoku Place, Hilo, HI 96720, USA; 5 Department of Physics & Astronomy, University of Victoria, Victoria BC V8P 1A1, Canada E-mail contact: yi.yang at nao.ac.jp We analyzed the young (2.8-Myr-old) binary system FS Tau A using near-infrared (H-band) high-contrast polarimetry data from Subaru/HiCIAO and sub-millimeter CO (J=2–1) line emission data from ALMA. Both the near-infrared and sub-millimeter observations reveal several clear structures extending to ∼240 AU from the stars. Based on these observations at different wavelengths, we report the following discoveries. One arm-like structure detected in the near- infrared band initially extends from the south of the binary with a subsequent turn to the northeast, corresponding to two bar-like structures detected in ALMA observations with an LSRK velocity of 1.19–5.64 km s−1. Another feature detected in the near-infrared band extends initially from the north of the binary, relating to an arm-like structure detected in ALMA observations with an LSRK velocity of 8.17–16.43 km s−1. From their shapes and velocities, we suggest that these structures can mostly be explained by two streamers that connect the outer circumbinary disk and the central binary components. These discoveries will be helpful for understanding the evolution of streamers and circumstellar disks in young binary systems. Accepted by ApJ http://arxiv.org/pdf/1912.11301

28 The widest Hα survey of accreting protoplanets around nearby transition disks A. Zurlo1,2, G. Cugno3, M. Montesinos4,5,6, S. Perez7, H. Canovas8 1 Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 2 Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 3 ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland; 4 Núcleo Milenio de Formación Planetaria (NPF), Chile; 5 Instituto de Física y Astronomía, Universidad de Valparaíso, Valparaíso, Chile; 6 Chinese Academy of Sciences South America Center for Astronomy, National Astronomical Observatories, CAS, Beijing, China; 7 Universidad de Santiago de Chile, Av. Libertador Bernardo O’Higgins 3363, Estacion Central, Santiago, Chile; 8 European Space Astronomy Centre (ESA/ESAC), Operations Department, Villanueva de la Cañada, Madrid, Spain E-mail contact: alice.zurlo at mail.udp.cl The mechanisms of planet formation are still under debate. We know little about how planets form, even if more than 4000 have been detected to date. Recent investigations target the cot of newly born planets: the protoplanetary disk. At the first stages of their life, exoplanets still accrete material from the gas-rich disk in which they are embedded. Transitional disks are indeed disks that show peculiarities, such as gaps, spiral arms, and rings, which can be connected to the presence of substellar companions. To investigate what is responsible for these features, we selected all the known transitional disks in the solar neighborhood (<200 pc) that are visible from the southern hemisphere. We conducted a survey of 11 transitional disks (TDs) with the SPHERE instrument at the VLT. This is the largest Hα survey that has been conducted so far to look for protoplanets. The observations were performed with the Halpha filter of ZIMPOL in order to target protoplanets that are still in the accretion stage. All the selected targets are very young stars, less than 20 Myr, and show low extinction in the visible. We reduced the ZIMPOL pupil stabilized data by applying the method of the angular spectral differential imaging (ASDI), which combines both techniques. The datacubes are composed of the Cnt_Hα and the narrow band filter Hα, which are taken simultaneously to permit the suppression of the speckle pattern. The principal component analysis (PCA) method was employed for the reduction of the data. For each dataset, we derived the 5σ contrast limit and converted it in upper limits on the accretion luminosity. We do not detect any new accreting substellar companions around the targeted transition disks down to an average contrast of 12 magnitudes at 0′′. 2 from the central star (continues in the manuscript). Accepted by A&A http://arxiv.org/pdf/1912.04911

29 Abstracts of recently accepted major reviews

The Dawn of Dust Astronomy Eberhard Grün1,2, Harald Krüger3, and Ralf Srama4 1 Max-Planck-Institut für Kernphysik, Heidelberg, Germany; 2 LASP, University of Colorado, Boulder, CO, USA; 3 Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany; 4 Institut für Raumfahrtsysteme Universität Stuttgart, Germany E-mail contact: harald.krueger at mps.mpg.de We review the development of dust science from the first ground-based astronomical observations of dust in space to compositional analysis of individual dust particles and their source objects. A multitude of observational techniques is available for the scientific study of space dust: from meteors and interplanetary dust particles collected in the upper atmosphere to dust analyzed in situ or returned to Earth. In situ dust detectors have been developed from simple dust impact detectors determining the dust hazard in Earth orbit to dust telescopes capable of providing compositional analysis and accurate trajectory determination of individual dust particles in space. The concept of Dust Astronomy has been developed, recognizing that dust particles, like photons, carry information from remote sites in space and time. From knowledge of the dust particles’ birthplace and their bulk properties, we learn about the remote environment out of which the particles were formed. Dust Observatory missions like Cassini, Stardust, and Rosetta study Saturn’s satellites and rings and the dust environments of comet Wild 2 and comet Churyumov- Gerasimenko, respectively. Supplemented by simulations of dusty processes in the laboratory we are beginning to understand the dusty environments in space. Accepted by ISSI book Cosmic Dust from the Laboratory to the Stars http://arxiv.org/pdf/1912.00707

The Role of Magnetic Fields in Protostellar Outflows and Star Formation Ralph E. Pudritz1 and Tom P. Ray2 1 Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada; 2 School of Cosmic Physics, Dublin Institute for Advanced Studies, Ireland The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire stellar mass spectrum. In this review, we describe the observational, theoretical, and computational advances on magnetized outflows, and their role in the formation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks by magnetized winds to efficiently extract and transport disk angular momentum was developed in early theoretical models and confirmed by a variety of numerical simulations. The recent high resolution ALMA observations of disks and outflows now confirm several key aspects of these ideas, e.g. that jets rotate and originate from large regions of their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI) turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk angular momentum. This has major consequences for star formation, as well as planet formation. Outflows also play an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being almost certainly fundamental to their production and focusing, magnetic fields in outflows in protostellar systems, and even in the disks, are notoriously difficult to measure. Most methods are indirect and lack precision, as for example, when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible - where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore what is known about magnetic fields from observations, and take a forward look to the time when facilities such as SPIRou and the SKA are in routine operation. Accepted by Frontiers in Astronomy and Space Sciences http://arxiv.org/pdf/1912.05605

30 Dissertation Abstracts

New Dimensions in the Observational Analysis of Molecular Clouds

Birgit Hasenberger Department for Astrophysics, University of Vienna Türkenschanzstraße 17, 1180 Vienna, Austria Electronic mail: birgit.hasenberger at univie.ac.at Ph.D dissertation directed by: João Alves Ph.D degree awarded: October 2019

Stars are formed in molecular clouds via a complex process that involves a variety of physical and chemical mecha- nisms. Characterising the influence of these mechanisms represents a crucial, yet challenging task for observational astronomers. This thesis explores new techniques that reveal the properties of molecular clouds and their population of dense cores by studying dust-emission observations towards a nearby (d ∼ 130 pc) molecular cloud, the Pipe nebula. Dust-emission observations provide information on the dust column density and the effective dust temperature. While the former is employed frequently to study the structure of molecular clouds, the latter is rarely used due to possible systematic effects in its derivation. However, this work demonstrates that the effective dust temperature can aid in locating regions of high volume density within the cloud and in identifying the mechanisms that dominate the thermodynamics of cores. In many cases, the process of observation reduces the number of spatial dimensions with respect to the physical object. For instance, molecular clouds and dense cores are inherently three-dimensional objects, while observations capture only two spatial dimensions. This fundamental difference in dimensionality represents an obstacle for the derivation of physical quantities from observational data. A novel technique to overcome this obstacle is presented in this thesis: The AVIATOR algorithm represents a new, robust method to estimate three-dimensional density distributions from their two-dimensional projections. To this end, the algorithm employs a set of intuitive assumptions about the line-of-sight density distribution. By reconstructing the three-dimensional density and temperature distribution of the Pipe nebula region with the AVI- ATOR algorithm, new insights on the physical properties of structures within the cloud are gained. The gravitational potential and acceleration arising from the density distribution provide a new way to assess the gravitational influence and energy budget of structures. In particular, the gravitational potential, in conjunction with the distribution of thermal energy, forms the basis of a scheme to define core boundaries in a physically motivated fashion. The resulting population of dense cores in the Pipe nebula exhibits properties markedly different from those reported in the liter- ature, including a high degree of gravitational binding and a comparably shallow high-mass slope of the core mass distribution. The methods introduced in this thesis enable a new view on molecular clouds and dense cores that exploits the information provided by dust-emission observations and considers the inherently three-dimensional structure of these objects. The core properties found here are in conflict with the literature, demonstrating the need for a thorough evaluation of techniques that are used frequently to define core boundaries and determine their energy budget. With the tools presented in this thesis, additional dimensions of the available observational data are utilised, leading towards a deeper understanding of the physical processes relevant at the early stages of star formation.

31 New Jobs

Postdoctoral Position in Star Formation & Observational Astrophysics Center for Astrophysics and Space Astronomy (CASA) Astrophysical and Planetary Sciences Department (APS) University of Colorado, Boulder Boulder, Colorado, USA Applications are invited for a two- postdoctoral position at the University of Colorado Boulder starting between May and August 2020, to work with Prof. John Bally on observations and theory of star-formation. The successful applicant will contribute to a research program using multi-wavelength imaging and spectroscopy from Apache Point Observatory, Subaru, ALMA, the JVLA, and other facilities. Familiarity with data reduction methods and tools is essential. Candidates familiar with numerical simulations such as N-body, SPH, or other codes used to investigate the physics of outflows, their interactions with the surrounding ISM, protostellar dynamic interactions and mergers among protostars will also be considered. Specific program goals are: [1] Complete the analysis and publication of existing data on the Orion OMC1 outflow, ejected stars, and environment. [2] Observe other Galactic explosive outflow candidates to constrain their event rates, properties, and impacts. [3] Continue near-IR monitoring of nearby star-forming galaxies to determine if N-body protostellar interactions are responsible for some extra-galactic IR transients detected by Spitzer. [4] Explore the use of 6.7 GHz (methanol) and 22 GHz (water) maser outbursts as alerts for protostellar mergers or major accretion- powered IR-transients. [5] Model circumstellar disk & envelope behavior in interactions using public-domain SPH and N-body codes. Who We Are: The Center for Astrophysics and Space Astronomy (CASA) is dedicated to advancing our understanding of the Universe in which we live through observations, theory, and the development of ground-based and space-borne instrumentation. Founded in 1985, CASA is an affiliated unit within the structure of the Astrophysical and Planetary Sciences (APS) Department at the University of Colorado, Boulder. What Your Key Responsibilities Will Be: The successful applicant will contribute to the research program by generat- ing new observing proposals, reducing and analyzing data, and writing-up results. Specific goals of this program are: (1) Measure the momentum and energy injection rates of various feedback mechanisms such as protostellar outflows, stellar winds, and radiation by measuring proper motions, radial velocities, and densities on multi- narrow-band visual and near-IR images and spectra. (2) Assist in the analysis of ALMA and other interferometer data tracing molecular gas in clouds and outflows from forming stars. (3) Assist in the preparation of new observing proposals. What We Offer: The appointment will be for an initial period of two years, with renewal for a third year contingent upon satisfactory progress and availability of funds. The position includes a competitive salary, research/travel funds, and access to CU’s computing resources and partnership in the Apache Point Observatory and Sloan Digital Sky Survey. Benefits: The University of Colorado offers excellent benefits, including medical, dental, retirement, paid time off, tuition benefit and ECO Pass. The University of Colorado Boulder is one of the largest employers in Boulder County and offers an inspiring higher education environment. Learn more about the University of Colorado Boulder. Be Adaptable. Be Imaginative. Be Boulder. What We Require: Applicants must have a PhD in astronomy or physics on arrival. What We Would Like You To Have: Experience with visual, infrared, and radio data reduction and analysis methods. Familiarity with numerical simulation of star-forming environments would be welcome. Special Instructions: To apply, please submit the following materials by April 15 , 2020:

32 • Resume/CV (including a list of publications) • Cover letter • Transcripts/Proof of Degree • Statement of research philosophy - Brief (up to 3 pages) research statement of your scientific interests and how you would specifically contribute to the research program described above. • Three letters of recommendation to be emailed as PDFs Application materials are accepted electronically via CU Boulder Jobs. Please send copies of application material via e-mail to [email protected]. Full consideration will be given to applications that are completed by April 15 , 2020. Posting Contact Information: https://jobs.colorado.edu/jobs/JobDetail/?jobId=23016 Posting Contact Name: Boulder Campus Human Resources Posting Contact Email: [email protected] The University of Colorado Boulder is committed to building a culturally diverse community of faculty, staff, and students dedicated to contributing to an inclusive campus environment. We are an Equal Opportunity employer, including veterans and individuals with disabilities.

ERC-funded postdoc position in star formation at Konkoly Observatory, Budapest

The “Structured Accretion Disks” ERC-funded research group invites applicants to a postdoc position at Konkoly Observatory (Budapest, Hungary) on the topic of structure, composition, and chemistry of circumstellar disks around young eruptive stars. The ERC Starting Grant is awarded to Dr Ágnes Kóspál, and its aim is to provide realistic initial conditions for the planet formation process. The position is for two years, available immediately, with a possibility of a shorter extension until 2022 June. Applicants must have a PhD in astrophysics (or related discipline).

Applicants with interest and experience in observational/computational astrophysics, radiative transfer, and the physics of the circumstellar matter are encouraged to apply. The successful applicant will be expected to carry out independent research for this project and collaborate with other members of the ERC group, Konkoly Obser- vatory, and its international partners. Konkoly Observatory has close connections to the Max Planck Institute for Astronomy (Heidelberg, Germany). The postdoc position comes with generous travel funds. The postdoc will have no teaching duties, although supervising students is possible. Konkoly Observatory is Hungary’s largest astronomical institute, located in a newly renovated building in a beautiful natural reserve area, half hour from the city center. The observatory has been dynamically expanding in recent years, including two ERC-funded projects and several international staff members. The observatory maintains telescopes at a Hungarian mountain station and astronomers regularly observe with international instrumentation as well.

Applications should be sent via e-mail to [email protected] in PDF format and must include a cover letter describing the applicant’s background and motivation for applying for the job, a CV, a list of publications, and names, addresses, phone numbers, and e-mail addresses of two or three reference persons. The Hungarian Academy of Sciences is an Equal Opportunity Employer. The postdoc will be a state employee and will have access to the Hungarian public health system. For further info about the research group or the observatory, see http://konkoly.hu/SACCRED and https://konkoly.hu/index_en.shtml.

Application Deadline: Friday, February 14, 2020

Contact: Dr. Ágnes Kóspál [email protected]

33 Multiple PhD positions in star/planet formation and exoplanet research

The University of Exeter is inviting applications for several fully funded PhD studentships to start in the fall of 2020. The Exeter Astrophysics group is one of the leading, and largest, groups in the UK for studying star formation and extra-solar planets.

(1) Breaking the stellar activity barrier to determining robust masses of small exoplanets. In this PhD Project, the student will use a variety of solar observations to develop models of intrinsic RV variations. They will identify and study velocity flows and small-scale magnetic features seen in spatially resolved observations of the Sun, notably from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI). This will allow them to develop models of intrinsic RV variations, which they will test against observations of the Sun seen as a distant, point-like star with the High-Accuracy Radial-velocity Planet Searcher in the Northern hemisphere (HARPS-N). The student will apply their models to other stars to determine robust planet masses by participating in the HARPS-N RV follow-up of TESS planet candidates. They will have opportunities to work with international collaborators in the United States and Europe. This project will be supervised by Dr. Raphaëlle Haywood, who is joining the University of Exeter in the summer of 2020. To apply, visit https://jobregister.aas.org/ad/1b442f2a

(2) Simulations of protoplanetary discs, dust coagulation, and planetesimal formation. The theme of this PhD project is simulating the beginnings of planet formation inside gas-rich protoplanetary discs. The student will (further) develop novel numerical techniques to model dust coagulation, the chemical evolution of protoplanetary disc materials, and the creation of planetesimals. The goal will be to predict the chemical compositions of the forming planetesimals and understand how these reflect the physical and chemical conditions in the protoplanetary nebula. Where possible, model predictions will be compared to observational constraints such as ALMA observations of gas and dust in young protoplanetary discs, or results from in-situ measurements of left-over planetesimals in our own solar system (e.g., comets, asteroids). This project will be supervised by Dr. Sebastiaan Krijt, who is joining the University of Exeter in the summer of 2020. To apply, visit https://jobregister.aas.org/ad/55a3060c

For a list of all the opportunities at the University of Exeter, visit http://emps.exeter.ac.uk/physics-astronomy/research/astrophysics/phd-opportunities/currentopportunities/

Abstract submission deadline

The deadline for submitting abstracts and other submissions is the first day of the month. Abstracts submitted after the deadline will appear in the fol- lowing month’s issue.

34 Meetings

Call for Review Proposal: Deadline April 1, 2020 Protostars & Planets VII (PP7) 1 - 7 April 2021, Kyoto, Japan

The Protostars & Planets series has served the community for more than three decades with state-of-the-art compi- lations of the current knowledge in the fields of star and planet formation. The previous volume PPVI was published in 2014. Since then, the field of Protostars & Planets has advanced significantly. The next Protostars & Planets conference will take place in Kyoto, Japan, April 1-7, 2021. For more details about the schedule and location, please visit the conference website: http://ppvii.org. A primary outcome of the conference will be a book of review articles as “Protostars and Planets VII”. This announce- ment is a call for proposals for review chapters in the book and associated talks. The organizers have defined rules in the submission of proposals, such as “one proposal per person” rule. Please refer to the website. Since the organizers would like to have sufficient time to evaluate the proposals, we ask you to submit proposals by April 1, 2020. The respective deadlines and dates are the following: Dec. 13, 2019 (this announcement): Call for review chapters and talk proposals Apr. 1, 2020 (15:00JST): Deadline for the submission of proposals Oct. 1, 2020: Decision on review chapters and talks Oct. 1, 2020: Start of registration Dec. 1, 2020: End of early registration Feb. 1, 2021: Submission of extended skeleton papers Mar. 1, 2021: Submission of the final review article Apr. 1, 2021: Start of PP7 meeting Scientific Advisory Committee (SAC): Joao Alves (Austria), Philippe Andre (France), Isabelle Baraffe (UK), John Carpenter (Chile), Paola Caselli (Ger- many), Wen-Ping Chen (Taiwan), Kees Dullemond (Germany), Tristan Guillot (France), Alyssa Goodman (USA), Lynne Hillenbrand (USA), Thomas Henning (Germany), Shigeru Ida (Japan), Doug Johnstone (Canada), Inga Kamp (Netherlands), Mark Krumholz (Australia), Jeong-Eun Lee (Korea), Victoria Meadows (USA), Michael Meyer (USA), Richard Nelson (UK), Toshikazu Onishi (Japan), Eve Ostriker (USA), Ilaria Pascucci (USA), Yasuhito Sekine (Japan), Shogo Tachibana (Japan), Mario Tafalla (Spain), Ewine van Dishoeck (Netherland), and Jonathan Williams (USA) PP7 Editors: Shu-ichiro Inutsuka (Nagoya University), Motohide Tamura (University of Tokyo), Yuri Aikawa (University of Tokyo), Takayuki Muto (Kogakuin University), and Kengo Tomida (Osaka University)

35 Summary of Upcoming Meetings

First Stars VI 1 - 6 March 2020 Concepcion, Chile http://www.astro.udec.cl/FirstStarsVI/ Interstellar Shocks School 22 - 27 March 2020, Les Houches, France https://www.sciencesconf.org/browse/conference/?confid=8899 Linking Dust, Ice, and Gas in Space 19 - 24 April 2020, Capri Islands, Italy http://www.frcongressi.it/ecla2020/ AIP Thinkshop on Protoplanetary Disk Chemodynamics 11 - 15 May 2020, Leibnitz Institute for Astrophysics Potsdam, Germany https://meetings.aip.de/event/1 Planet Formation: From Dust Coagulation to Final Orbital Assembly 1 - 26 June 2020, Munich, Germany http://www.munich-iapp.de/planetformation Cool Stars, Stellar Systems, and the Sun 21 21 - 26 June 2020, Toulouse, France https://coolstars21.github.io/ The Physics of Star Formation: From Stellar Cores to Galactic Scales; 29 June - 3 July 2020, Lyon, France http:/staratlyon.univ-lyon1.fr/en Illuminating the Dusty Universe: A Tribute to the Work of Bruce Draine 6 - 10 July 2020, Florence, Italy https://web.astro.princeton.edu/IlluminatingTheDusty Universe The Early Phase of Star Formation 12 - 17 July 2020, Ringberg, Germany http://www.mpia.de/homes/stein/EPoS/2020/2020.php Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann 17 - 20 August 2020, Malahide, Ireland https://www.dias.ie/cloudstodiscs/ Star Formation in Different Environments 2020 24 - 28 August 2020, Quy Nhon, Vietnam http://icisequynhon.com/conferences/sfde/ Planetary Science: The Young Solar System 6 - 12 September 2020, Quy Nhon, Vietnam http://www.icisequynhon.com/conferences/planetary_science/ Wheel of Star Formation: A conference dedicated to Prof. Jan Palouˇs 14 - 18 September 2020, Prague, Czech Republic https://janfest2020.asu.cas.cz Conditions and Impact of Star Formation - Across Times and Scales 28 September - 2 October 2020, Chile https://astro.uni-koeln.de/symposium-star-formation-2020.html

36 From Clouds to Planets II: The Astrochemical Link 28 September - 2 October 2020, Berlin, Germany https://events.mpe.mpg.de/event/12/ The Aftermath of a Revolution: Planet Formation Five Years after HL Tau 7 - 11 December 2020, Chile https://www.eso.org/sci/meetings/2020/hltau2020.html Protostars & Planets VII 1 - 7 April 2021, Kyoto, Japan http://www.ppvii.org

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