The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 336 — 21 December 2020
Editor: João Alveswww.starformation.news

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Cover image caption
The young cluster Trumpler 14 is one of the youngest massive star clusters in the Milky Way. With an age of about 4 Myr, amass of the order of 104 M , the cluster contains about 10 O-type and hundreds of B-type stars. The peculiarly shaped black
spot North of the center is not an image artifact but a dense globule’s silhouette. Trumpler 14 lies at a distance of about 2.8
kpc in the Carina Star-Forming Region. Credit: NASA, ESA, and J. Maíz Apellániz
Note from the Editor
The Star Formation Newsletter is now on the web at www.starformation.news. This PDF file contains the monthly Abstracts
and links to the different Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to the SFN is as simple
as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site. We extract the title, authors, and the abstract’s
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Abstracts
Resolving the outer ring of HD 38206 using ALMA and constraining limits on planets

1. in the system

Mark Booth, Michael Schulz, Alexander V. Krivov, Sebastián Marino, Tim D. Pearce, Ralf Launhardt HD
38206 is an A0V star in the Columba association, hosting a debris disc first discovered by IRAS. Further observations by Spitzer
and Herschel showed that the disc has two components, likely analogous to the asteroid and Kuiper belts of the Solar System.
The young age of this star makes it a prime target for direct imaging planet searches. Possible planets in the system can beconstrained using the debris disc. Here we present the first ALMA observations of the system’s Kuiper belt and fit them using
a forward modelling MCMC approach. We detect an extended disc of dust peaking at around 180 au with a width of 140 au.
The disc is close to edge on and shows tentative signs of an asymmetry best fit by an eccentricity of 0.25+0.10−0.09 . We use thefitted parameters to determine limits on the masses of planets interior to the cold belt. We determine that a minimum of four
planets are required, each with a minimum mass of 0.64 MJ , in order to clear the gap between the asteroid and Kuiper beltsof the system. If we make the assumption that the outermost planet is responsible for the stirring of the disc, the location of
its inner edge and the eccentricity of the disc, then we can more tightly predict its eccentricity, mass and semimajor axis to be
+0.20
+12
ep = 0.34−0.13, mp = 0.7+0.5−0.3 MJ and ap = 76−13 au.

2. The Age of the Carina Young Association and Potential Membership of HD 95086

Mark Booth, Carlos del Burgo, Valeri V. Hambaryan Carina is a nearby young stellar association. So far, only a small
number of stars have been clearly identified as members of this association. In this paper we reanalyse the membership of theassociation in light of Gaia DR2 data, in particular finding that HD 95086 is a potential member (probability of 71This star isnoteworthy as one of the few stars that hosts both a detected debris disc and a directly imaged planet. It has previously only
been considered as a potential member of the Lower Centaurus Crux (LCC) - part of the Scorpius-Centaurus association. We
also reanalyse the age of the Carina association. Using a Bayesian inference code applied to infer a solution from stellar evolution
models for the most probable (>99infer an age for the association of 13.3+1.1−0.6 Myr, much younger than previous studies. Whilst
we have revised HD 95086’s association membership from LCC to Carina, the fact that we also find Carina to have a younger
age, similar to that of LCC, means that the estimates of HD 95086b’s mass remain unchanged. However, the younger age ofCarina does mean that the companion to another Carina member, HD 44627 (or AB Pic), has a mass that is more clearly inthe planet rather than brown dwarf range.

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Dynamical stellar masses of pre-main sequence stars in Lupus and Taurus obtained with

3. ALMA surveys in comparison with stellar evolutionary models

Teresa A. M. Braun, Hsi-Wei Yen, Patrick M. Koch, Carlo F. Manara, Anna Miotello, Leonardo Testi We
analysed archival molecular line data of pre-main sequence (PMS) stars in the Lupus and Taurus star-forming regions obtainedwith ALMA surveys with an integration time of a few minutes per source. We stacked the data of 13 CO and C18 O (J =2-1 & 3-2) and CN (N = 3-2, J = 7/2-5/2) lines to enhance the signal-to-noise ratios, and measured the stellar masses of 45
out of 67 PMS stars from the Keplerian rotation in their circumstellar disks. The measured dynamical stellar masses werecompared to the stellar masses estimated from the spectroscopic measurements with seven different stellar evolutionary models.
We found that the magnetic model of Feiden (2016) provides the best estimate of the stellar masses in the mass range of
0.6 M ≤ M? ≤ 1.3 M with a deviation of <0.7σ from the dynamical masses, while all the other models underestimate thestellar masses in this mass range by 20% to 40%. In the mass range of < 0.6 M , the stellar masses estimated with the magnetic
model of Feiden (2016) have a larger deviation (> 2σ) from the dynamical masses, and other, non-magnetic stellar evolutionarymodels of Siess et al. (2000), Baraffe et al. (2015) and Feiden (2016) show better agreements with the dynamical masses withthe deviations of 1.4σ to 1.6σ. Our results show the mass dependence of the accuracy of these stellar evolutionary models.

H2 mass-velocity relationship from 3D numerical simulations of jet-driven molecular

4. outflows

Adriano Cerqueira, Bertrand Lefloch, Alejandro Esquivel, Pedro Rivera-Ortiz, Claudio Codella, Cecilia Ceccarelli, Linda Podio Previous numerical studies have shown that in protostellar outflows, the mass-velocity distribution m(v)can be well described by a broken power law ∝ v −γ . On the other hand, recent observations of a sample of outflows showthat the CO intensity-velocity distribution, closely related to m(v), follows an exponential law ∝ exp(−v/v0 ). In the present
work, we revisit the physical origin of the mass-velocity relationship m(v) in jet-driven protostellar outflows. We investigate
the respective contributions of the different regions of the outflow, from the swept-up ambient gas to the jet. We performed 3D
numerical simulations of a protostellar jet propagating into a molecular cloud using the hydrodynamical code Yguazu-a. The
code takes into account atomic and ionic species and was modified to include the H2 gas. We find that by excluding the jet
contribution, m(v) is satisfyingly fitted with a single exponential law, with v0 well in the range of observational values. The
jet contribution results in additional components in the mass-velocity relationship. This empirical mass-velocity relationship isfound to be valid locally in the outflow. The exponent v0 is almost constant in time and for a given level of mixing between theambient medium and the jet material. In general, v0 displays only a weak spatial dependence. A simple modeling of the L1157
outflow successfully reproduces the various components of the observed CO intensity-velocity relationship. Our simulations
indicate that these components trace the outflow cavity of swept-up gas and the material entrained along the jet, respectively.
The CO intensity-velocity exponential law is naturally explained by the jet-driven outflow model. The entrained material plays
an important role in shaping the mass-velocity profile.

5. The GRAVITY Young Stellar Object survey IV. The CO overtone emission in 51 Oph

at sub-au scales

GRAVITY Collaboration, M. Koutoulaki et al. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO
ro-vibrational emission at 2.3 micron, most likely originating in the innermost regions of a circumstellar disc. We aim to obtain
the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseousdisc. We used the second-generation VLTI/GRAVITY to spatially resolve the continuum and the CO overtone emission. We
obtained data over 12 baselines with the auxiliary telescopes and derive visibilities, and the differential and closure phases
as a function of wavelength. We used a simple LTE ring model of the CO emission to reproduce the spectrum and CO line
displacements. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of
10.58+-2.65 Rsun.The K-band continuum emission from the disc is inclined by 63+-1 deg, with a position angle of 116+-1 deg,
and 4+-0.8 mas (0.5+-0.1 au) across. The visibilities increase within the CO line emission, indicating that the CO is emitted
within the dust-sublimation radius.By modelling the CO bandhead spectrum, we derive that the CO is emitted from a hot(T=1900-2800 K) and dense (NCO=(0.9-9)×102 1 cm− 2) gas. The analysis of the CO line displacement with respect to thecontinuum allows us to infer that the CO is emitted from a region 0.10+-0.02 au across, well within the dust-sublimation radius.
The inclination and position angle of the CO line emitting region is consistent with that of the dusty disc. Our spatially resolved
interferometric observations confirm the CO ro-vibrational emission within the dust-free region of the inner disc. Conventional
disc models exclude the presence of CO in the dust-depleted regions of Herbig AeBe stars. Ad hoc models of the innermost discregions, that can compute the properties of the dust-free inner disc, are therefore required.

3

6. The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
Paulo C. Cortes, Valentin J. M. Le Gouellec, Charles L. H. Hull, Josep M. Girart, Fabien Louvet, Edward
B. Fomalont, Seiji Kameno, George A. Moellenbrock, Hiroshi Nagai, Kouichiro Nakanishi, Eric Villard We
present the first linear-polarization mosaicked observations performed by the Atacama Large Millimeter/submillimeter Array(ALMA). We mapped the Orion-KLeinmann-Low (Orion-KL) nebula using super-sampled mosaics at 3.1 and 1.3 mm as part of
the ALMA Extension and Optimization of Capabilities (EOC) program. We derive the magnetic field morphology in the planeof the sky by assuming that dust grains are aligned with respect to the ambient magnetic field. At the center of the nebula,
we find a quasi-radial magnetic field pattern that is aligned with the explosive CO outflow up to a radius of approximately 12
arc-seconds ( 5000 au), beyond which the pattern smoothly transitions into a quasi-hourglass shape resembling the morphology
seen in larger-scale observations by the James-Clerk-Maxwell Telescope (JCMT). We estimate an average magnetic field strength
hBi = 9.4 mG and a total magnetic energy of 2 × 104 5 ergs, which is three orders of magnitude less than the energy in the
explosive CO outflow. We conclude that the field has been overwhelmed by the outflow and that a shock is propagating fromthe center of the nebula, where the shock front is seen in the magnetic field lines at a distance of ∼ 5000 au from the explosion
center.

7. The SEDIGISM survey: Molecular clouds in the inner Galaxy

SEDIGISM Collaboration, A. Duarte-Cabral et al. We use the 13CO(2-1) emission from the SEDIGISM high-resolution
spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales,
using the SCIMES algorithm. This work compiles a cloud catalogue with a total of 10663 molecular clouds, 10300 of which wewere able to assign distances and compute physical properties. We study some of the global properties of clouds using a sciencesample, consisting of 6664 well resolved sources and for which the distance estimates are reliable. In particular, we compare thescaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and withouthigh-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability toform massive stars, although we find combined trends of increasing mass, size, surface density and velocity dispersion for the
sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample(i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental
effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different tothat of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-massstar-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least
dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least
populated areas. However, we suspect that part of these trends may be affected by some observational biases, and thus require
further follow up work in order to be confirmed.

8. Temperature Structure of the Pipe Nebula Studied by the Intensity Anomaly of the

OH 18 cm

Yuji Ebisawa, Nami Sakai, Karl M. Menten, Yoko Oya, Satoshi Yamamoto We present observations of the four
hyperfine structure components of the OH 18 cm transition (1612, 1665, 1667 and 1720 MHz) toward a filamentary dark cloud,the Pipe nebula, with the Green Bank Telescope. A statistical equilibrium analysis is applied to the spectra,and the kinetic
temperature of a diffuse molecular gas surrounding dense cores is determined accurately; the derived temperature ranges from40 K to 75 K. From this result, we assess the heating effect on the filamentarystructure of the nebula’s "stem" region due
to UV photons from a nearby star θ-Ophiuchi and a possible filament-filament collision in the interface of the "stem" and"bowl" regions. In the stem region, the gas kinetic temperature is found to be almost independent of the apparent distancefrom θ-Ophiuchi: the UV-heating effect by the star is not visible. On the other hand, the gas kinetic temperature is raised, ashigh as ∼75 K, at the interface of the two filamentary structures. This result provides us with an additional support to thefilament-filament collision scenario in the Pipe nebula.
26

9.

Al Enrichment in the Surface of Protostellar Disks Due to Protostellar Cosmic Rays

Brandt A. L. Gaches, Stefanie Walch, Stella S. R. Walch, Carsten Münker The radioactive decay of aluminum26 (26 Al) is an important heating source in early planet formation. Since its discovery, there have been several mechanisms
proposed to introduce 26 Al into protoplanetary disks, primarily through contamination by external sources. We propose a local
mechanism to enrich protostellar disks with 26 Al through irradiation of the protostellar disk surface by cosmic rays accelerated
in the protostellar accretion shock. We calculate the 26 Al enrichment, [26 Al/27 Al], at the surface of the protostellar disk in the
inner AU throughout the evolution of low-mass stars, from M-dwarfs to proto-Suns. Assuming constant mass accretion rates,ṁ, we find that irradiation by MeV cosmic rays can provide significant enrichment on the disk surface if the cosmic rays are
not completely coupled to the gas in the accretion flow. Importantly, we find that low accretion rates, ṁ < 10−7 M yr−1 ,are able to produce canonical amounts of 26 Al, [26 Al/27 Al] ≈ 5 × 10−5 . These accretion rates are experienced at the transition
from Class I- to Class II-type protostars, when it is assumed that calcium-aluminum-rich inclusions condense in the inner disk.

4

We conclude that irradiation of the inner disk surface by cosmic ray protons accelerated in accretion shocks at the protostellar
surface may be an important mechanism to produce 26 Al. Our models show protostellar cosmic rays may be a viable model toexplain the enrichment of 26 Al found in the Solar System.

Chamaeleon DANCe. Revisiting the stellar populations of Chamaeleon I and Chamaeleon
10. II with Gaia-DR2 data

P. A. B. Galli, H. Bouy, J. Olivares, N. Miret-Roig, L. M. Sarro, D. Barrado, A. Berihuete, E. Bertin, J.
C. Cuillandre Context: Chamaeleon is the southernmost low-mass star-forming complex within 200 pc from the Sun. Its
stellar population has been extensively studied in the past, but the current census of the stellar content is not complete yet anddeserves further investigation. Aims: We take advantage of the second data release of the Gaia space mission to expand thecensus of stars in Chamaeleon and to revisit the properties of the stellar populations associated to the Chamaeleon I (Cha I)
and Chamaeleon II (Cha II) dark clouds. Methods: We perform a membership analysis of the sources in the Gaia catalogue
over a field of 100 deg2 encompassing the Chamaeleon clouds, and use this new census of cluster members to investigate the
6D structure of the complex. Results: We identify 188 and 41 high-probability members of the stellar populations in Cha I and
Cha II, respectively, including 19 and 7 new members. Our sample covers the magnitude range from G = 6 to G = 20 mag in
Cha I, and from G = 12 to G = 18 mag in Cha II. We confirm that the northern and southern subgroups of Cha I are located at+1.0
different distances (191.4+0.8−0.8 pc and 186.7−1.0 pc), but they exhibit the same space motion within the reported uncertainties.
+1.0
Cha II is located at a distance of 197.5−0.9 pc and exhibits a space motion that is consistent with Cha I within the admittedly
large uncertainties on the spatial velocities of the stars that come from radial velocity data. The median age of the stars derived
from the Hertzsprung-Russell diagram (HRD) and stellar models is about 1-2 Myr, suggesting that they are somewhat younger
than previously thought. We do not detect significant age differences between the Chamaeleon subgroups, but we show that
Cha II exhibits a higher fraction of disc-bearing stars compared to Cha I.

ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) V: Sample,

11. overview, and demography of disk molecular emission

Antonio Garufi, Linda Podio, Claudio Codella, Davide Fedele, Eleonora Bianchi, Cecile Favre, Francesca Bacciotti, Cecilia Ceccarelli, Seyma Mercimek, Kazi Rygl, Richard Teague, Leonardo Testi We present an overview of
the ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT), a campaign devoted to the characterization of themolecular emission from partly embedded, young stars. The project aims at better understanding the gaseous products thatare delivered to planets by means of high-resolution maps of assorted lines probing disks at the time of the planet formation(less than 1 Myr). Nine different molecules are surveyed by our observations of six Class I/flat-spectrum sources. A series ofaccompanying articles analyze specific targets and molecules. Here we describe the sample and provide a general overview of
the results, focusing on the spatial distribution, column densities, and abundance ratios of H2 CO, CS, and CN. The results ofthis work are a first step toward the characterization of the disk chemical evolution that need to be complemented by further
observations of less exceptional disks and customized thermo-chemical modeling.

12.

The Geometry and Dynamical Role of Stellar Wind Bubbles in Photoionised HII Regions
Sam Geen, Rebekka Bieri, Joakim Rosdahl, Alex de Koter Winds from young massive stars contribute a large amountof energy to their host molecular clouds. This has consequences for the dynamics and observable structure of star-forming
clouds. In this paper, we present radiative magnetohydrodynamic simulations of turbulent molecular clouds that form individual stars of 30, 60 and 120 solar masses emitting winds and ultraviolet radiation following realistic stellar evolution tracks. We
find that winds contribute to the total radial momentum carried by the expanding nebula around the star at 10% of the levelof photoionisation feedback, and have only a small effect on the radial expansion of the nebula. Radiation pressure is largely
negligible in the systems studied here. The 3D geometry and evolution of wind bubbles is highly aspherical and chaotic, characterised by fast-moving "chimneys" and thermally-driven "plumes". These plumes can sometimes become disconnected fromthe stellar source due to dense gas flows in the cloud. Our results compare favourably with the findings of relevant simulations,analytic models and observations in the literature while demonstrating the need for full 3D simulations including stellar winds.
However, more targeted simulations are needed to better understand results from observational studies.

5

3D dynamics of the Orion cloud complex – Discovery of coherent radial gas motions at

13. the 100-pc scale

Josefa E. Großschedl, João Alves, Stefan Meingast, Gabor Herbst-Kiss We present the first study of the 3D dynamics
of the gas in the entire southern Orion cloud complex. We used the parallaxes and proper motions of YSOs from Gaia DR2 as aproxy for gas distance and proper motion, and the gas radial velocities from archival CO data, to compute the space motions of
the different star-forming clouds in the complex, including subregions in Orion A, Orion B, and two outlying cometary clouds.
From the analysis of the clouds’ orbits in space and time, we find that they were closest about 6 Myr ago and are moving
radially away from roughly the same region in space. This coherent 100-pc scale radial motion supports a scenario where theentire complex is reacting to a major feedback event, which we name the Orion-BB (big blast) event. This event, which wetentatively associate with the recently discovered Orion X stellar population, shaped the distribution and kinematics of the gas
we observe today, although it is unlikely to have been the sole major feedback event in the region. We argue that the dynamics
of most of the YSOs carry the memory of the feedback-driven star formation history in Orion and that the majority of theyoung stars in this complex are a product of large-scale triggering, which can raise the star formation rate by at least an orderof magnitude, as for the head of Orion A (the Integral Shape Filament). Our results imply that a feedback, compression, andtriggering process lies at the genesis of the Orion Nebula Cluster and NGC2023/2024 in Orion B, thus confirming broadly theclassical feedback-driven scenario proposed in Elmegreen & Lada (1977). The space motions of the well-known young compact
clusters, σ Orionis and NGC 1977, are consistent with this scenario. A momentum estimate suggests that the energy of a few
to several supernovae is needed to power the coherent 3D gas motion we measure in this paper.

Simulating Star Clusters Across Cosmic Time: II. Escape Fraction of Ionizing Photons

14. from Molecular Clouds

Chong-Chong He, Massimo Ricotti, Sam Geen We calculate the hydrogen and helium-ionizing radiation escaping starforming molecular clouds, as a function of the star cluster mass and compactness, using a set of high-resolution radiationmagneto-hydrodynamic simulations of star formation in self-gravitating, turbulent molecular clouds. In these simulations,presented in He, Ricotti and Geen (2019), the formation of individual massive stars are well resolved, and their UV radiation
feedback and lifetime on the main sequence are modeled self-consistently. We find that the escape fraction of ionizing radiation
MC
from molecular clouds, hfesc
i, decreases with increasing mass of the star cluster and with decreasing compactness. MolecularMC
clouds with densities typically found in the local Universe have negligible hfesc
i, ranging between 0.5% to 5%. Ten timesMCdenser molecular clouds have hfesc i ≈ 10% − 20%, while 100× denser clouds, which produce globular cluster progenitors, have
MC
MC
hfesc
i ≈ 20% − 60%. We find that hfesc
i increases with decreasing gas metallicity, even when ignoring dust extinction, due
to stronger radiation feedback. However, the total number of escaping ionizing photons decreases with decreasing metallicity
because the star formation efficiency is reduced. We conclude that the sources of reionization at z > 6 must have been very
compact star clusters forming in molecular clouds about 100× denser than in today’s Universe, which leads to a significant
production of old globular clusters progenitors.

Water maser variability in a high-mass YSO outburst – VERA and ALMA observations

15. of S255 NIRS 3

Tomoya Hirota, Riccardo Cesaroni, Luca Moscadelli, Koichiro Sugiyama, Ross A. Burns, Jungha Kim, Kazuyoshi
Sunada, Yoshinori Yonekura We carried out observations of the 22 GHz H2O masers in a high-mass protostar S255 NIRS 3
by using VERA. We measured the proper motions of the 22 GHz H2O masers associated with a bipolar outflow. The expansion
velocity of the blueshifted bow shock traced by the 22 GHz H2O masers was 28 km s-1 corresponding to a dynamical timescaleof 60 years. The direction of the maser outflow is slightly tilted compared with the radio jet, which could suggest a more recent
ejection episode during the accretion burst event. The total flux density of the 22 GHz H2O masers has gradually increased
from early 2017 and has become almost constant in 2018. For the first time, we reveal extended H2O maser emission at 22 GHz
in a star forming region, which is partly resolved out by VERA and even by the most extended VLA configurations. We findthat the flux variation of such an extended component is similar to that of the unresolved maser emission. We also conducted
observations of the submillimeter continuum and the 321 GHz H2O masers with ALMA at Band 7. The continuum emission
does not show significant variations compared with the previous observations performed 5 months before. We mapped the 321
GHz H2O masers in S255 NIRS 3 providing the fourth example, for this maser, of the spatial distribution in a high-mass starforming region. The lower ratio of the 22 GHz/321 GHz maser luminosity in the blueshifted bow shock suggests a temperature(>1000 K), higher than for the other maser features in this region. We conclude that the bow shock structure traced by the
22 GHz H2O maser features is unlikely to be originating at the interface between the radio jet powered by the recent accretion
outburst and the surrounding medium. The brightening of the 22 GHz H2O masers could be due to radiative excitation byphotons form the infrared outburst escaping along the cavity created by the newly ejected material.

6Rotating filament in Orion B: Do cores inherit their angular momentum from their

16. parent filament?

Cheng-Han Hsieh, Héctor G. Arce, Diego Mardones, Shuo Kong, Adele Plunkett Angular momentum is one of themost important physical quantities that govern star formation. The initial angular momentum of a core may be responsible for
its fragmentation and can have an influence on the size of the protoplanetary disk. To understand how cores obtain their initial
angular momentum, it is important to study the angular momentum of filaments where they form. While theoretical studies
on filament rotation have been explored, there exist very few observational measurements of the specific angular momentum
in star-forming filaments. We present high-resolution N2D+ ALMA observations of the LBS 23 (HH24-HH26) region in Orion
B, which provide one of the most reliable measurements of the specific angular momentum in a star-forming filament. We findthe total specific angular momentum (4 × 1020 cm2 s−1 ), the dependence of the specific angular momentum with radius (j(r)∝ r1.83 ), and the ratio of rotational energy to gravitational energy (βrot ∼ 0.04) comparable to those observed in rotating coreswith sizes similar to our filament width (∼ 0.04 pc) in other star-forming regions. Our filament angular momentum profile
is consistent with rotation acquired from ambient turbulence and with simulations that show cores and their host filaments
develop simultaneously due to the multi-scale growth of nonlinear perturbation generated by turbulence.

17. A search for radio jets from massive young stellar objects. Association of radio jetswith H2O and CH3OH masers

U. Kavak, A. Sanchez-Monge, A. Lopez-Sepulcre, R. Cesaroni, F. F. S. van der Tak, L. Moscadelli, M. T.
Beltran, P. Schilke Recent theoretical and observational studies debate the similarities between the formation process ofhigh-mass (>8 Msun) and low-mass stars. The formation of low-mass star formation is directly associated with the presenceof disks and jets. According to this scenario, radio jets are expected to be common in high-mass star-forming regions. We aim
to increase the number of known radio jets in high-mass star forming regions by searching for radio jet candidates at radio
continuum wavelengths. We have used the Karl G. Jansky Very Large Array (VLA) to observe 18 high-mass star-forming
regions in the C band (6 cm, 1.0 arcsec resolution) and K band (1.3 cm, 0.3 arcsec resolution). We have searched for radio
jet candidates by studying the association of radio continuum sources with shock activity signposts. We have identified 7 as
the most probable radio jets. The radio luminosity of the radio jet candidates is correlated with the bolometric luminosity andthe outflow momentum rate. About 7-36% of the radio jet candidates are associated with non-thermal emission. The radio
jet candidates associated with 6.7 GHz CH3OH maser emission are preferentially thermal winds and jets, while a considerable
fraction of radio jet candidates associated with H2O masers show non-thermal emission, likely due to strong shocks. Our sample
of 18 regions is divided in 8 less evolved, infrared-dark regions and 10 more evolved, infrared-bright regions. We have foundthat ∼ 71% of the identified radio jet candidates are located in the more evolved regions. Similarly, 25most probable radio jets,
while up to 50one of these radio jet candidates. This suggests that the detection of radio jets in high-mass star forming regions
is larger in slightly more evolved regions.

Interactions of a shock with a molecular cloud at various stages of its evolution due to

18. thermal instability and gravity

M. M. Kupilas, C. J. Wareing, J. M. Pittard, S. A. E. G. Falle Using the adaptive mesh refinement code MG, weperform hydrodynamic simulations of the interaction of a shock with a molecular cloud evolving due to thermal instability andgravity. To explore the relative importance of these processes, three case studies are presented. The first follows the formationof a molecular cloud out of an initially quiescent atomic medium due to the effects of thermal instability and gravity. The secondcase introduces a shock whilst the cloud is still in the warm atomic phase, and the third scenario introduces a shock once themolecular cloud has formed. The shocks accelerate the global collapse of the clouds with both experiencing local gravitational
collapse prior to this. When the cloud is still atomic, the evolution is shock dominated and structures form due to dynamical
instabilities within a radiatively cooled shell. While the transmitted shock can potentially trigger the thermal instability, this isprevented as material is shocked multiple times on the order of a cloud crushing time-scale. When the cloud is molecular, thepost-shock flow is directed via the pre-existing structure through low-density regions in the inter-clump medium. The clumps
are accelerated and deformed as the flow induces clump-clump collisions and mergers that collapse under gravity. For a limited
period, both shocked cases show a mixture of Kolmogorov and Burgers turbulence-like velocity and logarithmic density power
spectra, and strongly varying density spectra. The clouds presented in this work provide realistic conditions that will be usedin future feedback studies.

719. Viscous Heating and Boundary Layer Accretion in the Disk of Outbursting Star FU

OrionisAaron Labdon, Stefan Kraus, Claire L Davies, Alexander Kreplin, John D Monnier, Jean-Baptiste Le Bouquin,
Narsireddy Anugu, Theo Brummelaar, Benjamin Setterholm, Tyler Gardener, Jacob Ennis, Cyprien Lanthermann, Gail Schaefer, Anna Laws Context. FU Orionis is the archetypal FUor star, a subclass of young stellar object(YSO) that undergo rapid brightening events, often gaining 4-6 magnitudes on timescales of days. This brightening is often
associated with a massive increase in accretion; one of the most ubiquitous processes in astrophysics from planets and stars tosuper-massive black holes. We present multi-band interferometric observations of the FU Ori circumstellar environment, including the first J-band interferometric observations of a YSO. Aims. We investigate the morphology and temperature gradientof the inner-most regions of the accretion disk around FU Orionis. We aim to characterise the heating mechanisms of the disk
and comment on potential outburst triggering processes. Methods. Recent upgrades to the MIRC-X instrument at the CHARA
array allowed the first dual-band J and H observations of YSOs.Using baselines up to 331 m, we present high angular resolution
data of a YSO covering the near-infrared bands J, H, and K. The unprecedented spectral range of the data allows us to apply
temperature gradient models to the innermost regions of FU Ori. Results. We spatially resolve the innermost astronomical
unit of the disk and determine the exponent of the temperature gradient of the inner disk to T = r−0.74±0.02 . This agrees withtheoretical work that predicts T = r−0.75 for actively accreting, steady state disks, a value only obtainable through viscousheating within the disk. We find a disk which extends down to the stellar surface at 0.015 ± 0.007 au where the temperature isfound to be 5800 ± 700 K indicating boundary layer accretion. We find a disk inclined at 32 ± 4◦ with a minor-axis position
angle of 34 ± 11◦ .

20. Chemically tracing the water snowline in protoplanetary disks with HCO+

M. Leemker, M. L. R. van ’t Hoff, L. Trapman, M. L. van Gelder, M. R. Hogerheijde, D. Ruíz-Rodríguez,
E. F. van Dishoeck [Abridged] Planet formation is expected to be enhanced around snowlines in protoplanetary disks, inparticular around the water snowline. However, the close proximity of the water snowline to the host star and water in the
Earth’s atmosphere makes a direct detection of the water snowline in protoplanetary disks challenging. Following earlier workon protostellar envelopes, the aim of this research is to investigate the validity of HCO+ and H13 CO+ , as tracers of the water
snowline in protoplanetary disks, as HCO+ is destroyed by gas-phase water. Two small chemical networks are used to predict
the HCO+ abundance in a typical Herbig Ae disk. Subsequently, the corresponding emission profiles are modelled for H13 CO+and HCO+ J = 2 − 1, which provides the best balance between brightness and optical depth effects of the continuum emission.
The HCO+ abundance jumps by two orders of magnitude just outside the water snowline at 4.5 AU. We find that the emissionof H13 CO+ and HCO+ is ring-shaped due to three effects: destruction of HCO+ by gas-phase water, continuum optical depth,
and molecular excitation effects. The presence of gas-phase water causes an additional drop of only ∼13in the center of the disk,for H13 CO+ and HCO+ , respectively. For the much more luminous outbursting source V883Ori, our models predict that theeffect of dust and excitation are not limiting if the snowline is located outside ∼40 AU. Our analysis of ALMA observations of
HCO+ J = 3 − 2 is consistent with the water snowline located around 100 AU. The HCO+ abundance drops steeply around thewater snowline, but dust and excitation can conceal the drop in HCO+ emission due to the water snowline. Therefore, locating
the water snowline with HCO+ in Herbig disks is very difficult, but it is possible for outbursting sources like V883Ori.

Inferring (Sub)millimeter Dust Opacities and Temperature Structure in Edge-on Pro-

21. tostellar Disks From Resolved Multi-Wavelength Continuum Observations: The Caseof the HH 212 Disk
Zhe-Yu Daniel Lin, Chin-Fei Lee, Zhi-Yun Li, John Tobin, Neal Turner (Sub)millimeter dust opacities are requiredfor converting the observable dust continuum emission to the mass, but their values have long been uncertain, especially indisks around young stellar objects. We propose a method to constrain the opacity κν in edge-on disks from a characteristic
optical depth τ0,ν , the density ρ0 and radius R0 at the disk outer edge through κν = τ0,ν /(ρ0 R0 ) where τ0,ν is inferred from theshape of the observed flux along the major axis, ρ0 from gravitational stability considerations, and R0 from direct imaging. We
applied the 1D semi-analytical model to the embedded, Class 0, HH 212 disk, which has high-resolution data in ALMA Band9, 7, 6, and 3 and VLA Ka band (λ=0.43, 0.85, 1.3, 2.9, and 9.1 mm). The modeling of the HH 212 disk is extended to 2D
through RADMC-3D radiative transfer calculations. We find a dust opacity of κν ≈ 1.9 × 10−2 , 1.3 × 10−2 , and 4.9 × 10−3 cm2
per gram of gas and dust for ALMA Bands 7, 6, and 3, respectively with uncertainties dependent on the adopted stellar mass.
The inferred opacities lend support to the widely used prescription κλ = 2.3 × 10−2 (1.3mm/λ) cm2 g−1 advocated by Beckwith
et al. (1990). We inferred a temperature of 45K at the disk outer edge which increases radially inward. It is well above thesublimation temperatures of ices such as CO and N2 , which supports the notion that the disk chemistry cannot be completely
inherited from the protostellar envelope.

822. ALMA View of the Infalling Envelope around a Massive Protostar in S255IR SMA1
Sheng-Yuan Liu, Yu-Nung Su, Igor Zinchenko, Kuo-Song Wang, Dominique M. -A. Meyer, Yuan Wang, I-Ta
Hsieh The massive young stellar object S255IR NIRS3 embedded in the star forming core SMA1 has been recently observedwith a luminosity burst, which is conjectured as a disc-mediated variable accretion event. In this context, it is imperative
to characterize the gas properties around the massive young stellar object. With this in mind, we carried out high angularresolution observations with the Atacama Large Millimeter and submillimeter Array and imaged the 900 µm dust continuum
and the CH3 CN J=19−18 K=0−10 transitions of S255IR SMA1. The integrated CH3 CN emission exhibits an elongated feature
with an extent of 1800 au in the northwest-southeast direction at a position angle of 165 degree, which is nearly perpendicular
to the bipolar outflow. We confirm the presence of dense (a few ×109 cm−3 ) and hot (∼ 400 K) gas immediately surrounding
the central protostar. The CH3 CN emission features a velocity gradient along the elongated ridge and by modelling the gas
kinematics based on features in the position-velocity diagram, we infer that the gas is best described by a flattened rotating
infalling envelope (or pseudo-disc). A mass infall rate of a few × 10−4 solar-mass per year is derived. If there exists a putative
Keplerian disc directly involved in the mass accretion onto the star and jet/outflow launching, it is likely smaller than 125 au andunresolved by our observations. We show qualitative resemblances between the gas properties (such as density and kinematics)
in 255IR SMA1 inferred from our observations and those in a numerical simulation particularly tailored for studying the burst
mode of massive star formation.

23. Discovery of a mid-infrared protostellar outburst of exceptional amplitude

P. W. Lucas, J. Elias, S. Points, Z. Guo, L. C. Smith, B. Stecklum, E. Vorobyov, C. Morris, J. Borissova,
R. Kurtev, C. Contreras Pena, N. Medina, D. Minniti, V. D. Ivanov, R. K. Saito We report the discovery of a
mid-infrared outburst in a Young Stellar Object (YSO) with an amplitude close to 8 mag at λ≈4.6 µm. WISEA J142238.82611553.7 is one of 23 highly variable WISE sources discovered in a search of Infrared Dark Clouds (IRDCs). It lies within
the small IRDC G313.671-0.309 (d≈2.6 kpc), seen by the Herschel/HiGal survey as a compact, massive cloud core that may
have been measurably warmed by the event. Pre-outburst data from Spitzer in 2004 suggest that it is a class I YSO, a viewsupported by observation of weak 2.12 µm H2 emission in an otherwise featureless red continuum spectrum taken in 2019 (6mag below the peak in Ks ). Spitzer, WISE and VVV data indicate that the outburst began by 2006 and has a duration >13
yr, with a fairly flat peak from 2010–2014. The outburst luminosity of a few ×102 Lsun is consistent with an accretion rate
Mdot ≈ 10−4 Msun/yr, comparable to a classical FU Orionis event. The 4.6 µm peak in 2010 implies T = 800-1000 K anda disc radial location R≈4.5 au for the emitting region. The colour evolution suggests subsequent progression outward. The
apparent absence of the hotter matter expected in thermal instability or MRI models may be due to complete obscuration of theinnermost disc, e.g. by an edge-on disc view. Alternatively, disc fragmentation/infalling fragment models might more naturally
explain a mid-infrared peak, though this is not yet clear.

24. Extended stellar systems in the solar neighborhood – V. Discovery of coronae of nearby

star clusters

Stefan Meingast, João Alves, Alena Rottensteiner In this paper, we present a novel view on the morphology and the
dynamical state of 10 prominent, nearby (≤ 500 pc), and young (∼30-300 Myr) open star clusters with Gaia DR2: α Per,
Blanco 1, IC 2602, IC 2391, Messier 39, NGC 2451A, NGC 2516, NGC 2547, Platais 9, and the Pleiades. We introduce a
pioneering member identification method that is informed by cluster bulk velocities and deconvolves the spatial distribution
with a mixture of Gaussians. Our approach enables inferring the clusters’ true spatial distribution by effectively filtering fieldstar contaminants while at the same time mitigating the impact of positional errors along the line of sight. This first applicationof the method reveals the existence of vast stellar coronae, extending for & 100 pc and surrounding the, by comparison tiny
and compact, cluster cores. The coronae and cores form intertwined, co-eval, and co-moving extended cluster populations, eachencompassing tens of thousands of cubic parsec and stretching across tens of degrees on the sky. Our analysis shows that thecoronae are gravitationally unbound but largely comprise the bulk of the populations’ stellar mass. Most systems are in ahighly dynamic state, showing evidence of expansion and sometimes simultaneous contraction along different spatial axes. The
velocity field of the extended populations for the cluster cores appears asymmetric but is aligned along a spatial axis uniqueto each cluster. The overall spatial distribution and the kinematic signature of the populations are largely consistent with thedifferential rotation pattern of the Milky Way. This finding underlines the important role of global Galactic dynamics to thefate of stellar systems. Our results highlight the complexity of the Milky Way’s open cluster population and call for a newperspective on the characterization and dynamical state of open clusters.

High-Resolution Mid-Infrared Spectroscopy of GV Tau N: Surface Accretion and De-

25. tection of Ammonia in a Young Protoplanetary Disk

Joan R. Najita, John S. Carr, Sean D. Brittain, John H. Lacy, Matthew J. Richter, Greg W. Doppmann Physicalprocesses that redistribute or remove angular momentum from protoplanetary disks can drive mass accretion onto the star andaffect the outcome of planet formation. Despite ubiquitous evidence that protoplanetary disks are engaged in accretion, the9process(es) responsible remain unclear. Here we present evidence for redshifted molecular absorption in the spectrum of a ClassI source that indicates rapid inflow at the disk surface. High resolution mid-infrared spectroscopy of GV Tau N reveals a richabsorption spectrum of individual lines of C2H2, HCN, NH3, and water. From the properties of the molecular absorption, we
can infer that it carries a significant accretion rate ( 1e-8 to 1e-7 Msun/yr), comparable to the stellar accretion rates of active T
Tauri stars. Thus we may be observing disk accretion in action. The results may provide observational evidence for supersonic"surface accretion flows," which have been found in MHD simulations of magnetized disks. The observed spectra also represent
the first detection of ammonia in the planet formation region of a protoplanetary disk. With ammonia only comparable inabundance to HCN, it cannot be a major missing reservoir of nitrogen. If, as expected, the dominant nitrogen reservoir in inner
disks is instead N2, its high volatility would make it difficult to incorporate into forming planets, which may help to explain the
low nitrogen content of the bulk Earth.

26. Observations of magnetic fields surrounding LkHα 101 taken by the BISTRO survey

with JCMT-POL-2

BISTRO Collaboration, Nguyen Bich Ngoc et al. We report the first high spatial resolution measurement of magnetic
fields surrounding LkHα 101, a part of the Auriga-California molecular cloud. The observations were taken with the POL-2
polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations(BISTRO) survey. Observed polarization of thermal dust emission at 850 µm is found to be mostly associated with the
red-shifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of theDavis-Chandrasekhar-Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic
fields in the plane of the sky, yielding a similar result of BPOS ∼ 115 µG. The mass-to-magnetic-flux ratio in critical value units,
λ ∼ 0.3, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkHα 101 regionis sub-critical and the magnetic field is strong enough to prevent gravitational collapse. The inferred δB/B0 ∼ 0.3 implies thatthe large scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction withtotal emission intensity can be fitted by a power-law with an index of α = 0.82 ± 0.03, which lies in the range previously reported
for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkHα101) in the region. The magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative
torques are potential of explaining such a decreasing trend.

Deciphering the 3-D Orion Nebula-II: A low-ionization region of multiple velocity com-

27. ponents southwest of Theta1OriC confounds interpretation of low velocity resolution

studies of temperature, density, and abundance
C. R. O’Dell, N. P. Abel, G. J. Ferland We establish that there are two velocity systems along lines-of-sight that contribute to the emission-line spectrum of the the brightest parts of the Orion Nebula. These overlie the Orion-S embedded
molecular cloud southwest of the dominant ionizing star (Theta1OriC). Examination of 10x10" samples of high spectral resolution emission-line spectra of this region reveals it to be of low ionization, with velocities and ionization different from thecentral part of the Nebula. These properties jeopardize earlier determinations of abundance and physical conditions since they
indicate that this region is much more complex than has been assumed in analyzing earlier spectroscopic studies and argue foruse of very high spectral resolution or known simple regions in future studies.

28. Ring formation by coagulation of dust aggregates in early phase of disk evolution arounda protostar

Satoshi Ohashi, Hiroshi Kobayashi, Riouhei Nakatani, Satoshi Okuzumi, Hidekazu Tanaka, Koji Murakawa,
Yichen Zhang, Hauyu Baobab Liu, Nami Sakai Ring structures are observed by (sub-)millimeter dust continuum emission
in various circumstellar disks from early stages of Class 0 and I to late stage of Class II young stellar objects (YSOs). In thispaper, we study one of the possible scenarios of such ring formation in early stage, which is coagulation of dust aggregates.
The dust grains grow in an inside-out manner because the growth timescale is roughly proportional to the orbital period. The
boundary of the dust evolution can be regarded as the growth front, where the growth time is comparable to the disk age.
With radiative transfer calculations based on the dust coagulation model, we find that the growth front can be observed as aring structure because dust surface density is sharply changed at this position. Furthermore, we confirm that the observed ring
positions in the YSOs with an age of . 1 Myr are consistent with the growth front. The growth front could be important tocreate the ring structure in particular for early stage of the disk evolution such as Class 0 and I sources.

Substructures in the Disk-Forming Region of the Class 0 Low-Mass Protostellar Source

29. IRAS 16293-2422 Source A on a 10 au Scale

Yoko Oya, Satoshi Yamamoto We have observed the Class 0 protostellar source IRAS 16293-2422 A in the C17O and H2CS
lines as well as the 1.3 mm dust continuum with the Atacama Large Millimeter/submillimeter Array at an angular resolution10

of 0."1 (14 au). The continuum emission of the binary component, Source A, reveals the substructure consisting of 5 intensity
peaks within 100 au from the protostar. The C17O emission mainly traces the circummultiple structure on a 300 au scalecentered at the intensity centroid of the continuum, while it is very weak within the radius of 50 au from the centroid. The
H2CS emission, in contrast, traces the rotating disk structure around one of the continuum peaks (A1). Thus, it seems that therotation centroid of the circummultiple structure is slightly different from that of the disk around A1. We derive the rotation
temperature by using the multiple lines of H2CS. As approaching to the protostar A1, the rotation temperature steeply rises up
to 300 K or higher at the radius of 50 au from the protostar. It is likely due to a local accretion shock and/or the preferential
protostellar heating of the transition zone from the circummultiple structure to the disk around A1. This position corresponds
to the place where the organic molecular lines are reported to be enhanced. Since the rise of the rotation temperature of H2CS
most likely represents the rise of the gas and dust temperatures, it would be related to the chemical characteristics of thisprototypical hot corino.

30. JCMT POL-2 and BISTRO Survey observations of magnetic fields in the L1689 molec-

ular cloud

Kate Pattle, Shih-Ping Lai, James Di Francesco, Sarah Sadavoy, Derek Ward-Thompson, Doug Johnstone,
Thiem Hoang, Doris Arzoumanian, Pierre Bastien, Tyler L. Bourke, Simon Coudé, Yasuo Doi, Chakali Eswaraiah, Lapo Fanciullo, Ray S. Furuya, Jihye Hwang, Charles L. H. Hull, Jihyun Kang, Kee-Tae Kim, Florian Kirchschlager, Jungmi Kwon, Woojin Kwon, Chang Won Lee, Tie Liu, Matt Redman, Archana Soam, MehrnooshTahani, Motohide Tamura, Xindi Tang We present 850µm polarization observations of the L1689 molecular cloud, partof the nearby Ophiuchus molecular cloud complex, taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope(JCMT). We observe three regions of L1689: the clump L1689N which houses the IRAS 16293-2422 protostellar system, thestarless clump SMM-16, and the starless core L1689B. We use the Davis-Chandrasekhar-Fermi method to estimate plane-of-sky
field strengths of 366 ± 55 µG in L1689N, 284 ± 34 µG in SMM-16, and 72 ± 33 µG in L1689B, for our fiducial value of dust
opacity. These values indicate that all three regions are likely to be magnetically trans-critical with sub-Alfvénic turbulence.
In all three regions, the inferred mean magnetic field direction is approximately perpendicular to the local filament direction
identified in Herschel Space Telescope observations. The core-scale field morphologies for L1689N and L1689B are consistent
with the cloud-scale field morphology measured by the P lanck Space Observatory, suggesting that material can flow freely fromlarge to small scales for these sources. Based on these magnetic field measurements, we posit that accretion from the cloud
onto L1689N and L1689B may be magnetically regulated. However, in SMM-16, the clump-scale field is nearly perpendicular
to the field seen on cloud scales by P lanck, suggesting that it may be unable to efficiently accrete further material from its
surroundings.

31. Growing and Trapping Pebbles with Fragile Collisions of Particles in Protoplanetary

Disks

Paola Pinilla, Christian T. Lenz, Sebastian M. Stammler [abridged] Recent laboratory experiments indicate that
destructive collisions of icy dust particles occur with much lower velocities than previously thought. When these new velocities
are considered from laboratory experiments in dust evolution models, a growth to pebble sizes in protoplanetary disks (PPDs) isdifficult. This may contradict (sub-)mm observations and challenge the formation of planetesimals and planets. We investigate
the conditions that are required in dust evolution models for growing and trapping pebbles in PPDs when the fragmentation
speed is 1ms−1 in the entire disk. We distinguish the parameters controlling the effects of turbulent velocities, vertical stirring,radial diffusion, and gas viscous evolution, always assuming that particles cannot diffuse faster (radially or vertically) than
the gas. To form pebbles and produce effective particle trapping, the parameter that controls the particle turbulent velocities
must be small (δt . 10−4 ). In these cases, the vertical settling can limit the formation of pebbles, which also prevents particle
trapping. Therefore the parameter that sets the vertical settling of the grains must be δz < 10−3 . Our results suggest thatdifferent combinations of the particle and gas diffusion parameters can lead to a large diversity of millimeter fluxes and dust-diskradii. When pebble formation occurs and trapping is efficient, gaps and rings have higher contrast at mm-emission than in the
NIR. In the case of inefficient trapping, structures are also formed at the two wavelengths, producing deeper and wider gaps in
the NIR. Our results highlight the importance of obtaining observational constraints of gas and particle diffusion parameters
and the properties of gaps at short and long wavelengths to better understand basic features of PPDs and the origin of thestructures that are observed in these objects.

likelihood of
32. Observational constraints on the26

26

Al in planet-forming environments

Megan Reiter Recent work suggests that Al may determine the water budget in terrestrial exoplanets as its radioactive
decay dehydrates planetesimals leading to rockier compositions. Here I consider the observed distribution of 26 Al in the Galaxy
and typical star-forming environments to estimate the likelihood of 26 Al enrichment during planet formation. I do not assume
Solar-System-specific constraints as I am interested in enrichment for exoplanets generally. Observations indicate that highmass stars dominate the production of 26 Al with nearly equal contributions from their winds and supernovae. 26 Al abundances11are comparable to those in the early Solar System in the high-mass star-forming regions where most stars (and thereby mostplanets) form. These high abundances appear to be maintained for a few Myr, much longer than the 0.7 Myr half-life. Observed
bulk 26 Al velocities are an order of magnitude slower than expected from winds and supernovae. These observations are at odds
with typical model assumptions that 26 Al is provided instantaneously by high velocity mass loss from supernovae and winds.
Regular replenishment of 26 Al especially when coupled with the small age differences that are common in high-mass star-forming
complexes, may significantly increase the number of star/planet-forming systems exposed to 26 Al. Exposure does not imply
enrichment, but the order of magnitude slower velocity of 26 Al may alter the fraction that is incorporated into planet-forming
material. Together, this suggests that the conditions for rocky planet formation are not rare, nor are they ubiquitous, as small
regions like Taurus that lack high-mass stars to produce 26 Al may be less likely to form rocky planets. I conclude with suggested
directions for future studies.

33. Kinematic Analysis of a Protostellar Multiple System: Measuring the Protostar Masses

and Assessing Gravitational Instability in the Disks of L1448 IRS3B and L1448 IRS3A

Nickalas K. Reynolds, John J. Tobin, Patrick D. Sheehan, Sarah I. Sadavoy, Kaitlin M. Kratter, Zhi-Yun Li,
Claire J. Chandler, Dominique M. Segura-Cox, Leslie W. Looney, Michael M. Dunham We present new Atacama
Large Millimeter/submillimeter Array (ALMA) observations towards a compact (230 au separation) triple protostar system,
L1448 IRS3B, at 879µ with 0.11 × 0.05 arcsec resolution. Spiral arm structure within the circum-multiple disk is well resolved
in dust continuum toward IRS3B, and we detect the known wide (2300 au) companion, IRS3A, also resolving possible spiral
substructure. Using dense gas tracers, C17O, H13CO+, and H13CN, we resolve the Keplerian rotation for both the circumtriple disk in IRS3B and the disk around IRS3A. Furthermore, we use the molecular line kinematic data and radiative transfer
modeling of the molecular line emission to confirm that the disks are in Keplerian rotation with fitted masses of 1.19+0.13−0.07
for IRS3B-ab, 1.51+0.06−0.07 Msun for IRS3A, and place an upper limit on the central protostar mass for the tertiary IRS3B-c of
0.2 Msun. We measure the mass of the fragmenting disk of IRS3B to be 0.29 Msun from the dust continuum emission of
the circum-multiple disk and estimate the mass of the clump surrounding IRS3B-c to be 0.07 Msun. We also find that thedisk around IRS3A has a mass of 0.04 Msun. By analyzing the Toomre Q parameter, we find the IRS3A circumstellar disk isgravitationally stable (Q>5), while the IRS3B disk is consistent with a gravitationally unstable disk (Q<1) between the radii
200-500 au. This coincides with the location of the spiral arms and the tertiary companion IRS3B-c, supporting the hypothesisthat IRS3B-c was formed in situ via fragmentation of a gravitationally unstable disk.

34. Accretion and outflow activity in proto-brown dwarfs

B. Riaz, J. Bally We present a near-infrared study of accretion and outflow activity in 6 Class 0/I proto-brown dwarfs (protoBDs) using VLT/SINFONI spectroscopy and spectro-imaging observations. The spectra show emission in several [FeII] and H2lines associated with jet/outflow activity, and in the accretion diagnostics of Paβ and Brγ lines. The peak velocities of the [FeII]lines (>100 km s−1 ) are higher than the H2 lines. The Class 0 proto-BDs show strong emission in the H2 lines but the [FeII]lines are undetected, while the Class I objects show emission in both [FeII] and H2 lines, suggesting an evolutionary trend in
the jets from a molecular to an ionic composition. Extended emission with knots is seen in the [FeII] and H2 spectro-images for
3 proto-BDs, while the rest show compact morphologies with a peak on-source. The accretion rates for the proto-BDs span therange of (2×10−6 – 2×10−8 ) Msun yr−1 , while the mass loss rates are in the range of (4×10−8 – 5×10−9 ) Msun yr−1 . These
rates are within the range measured for low-mass protostars and higher than Class II brown dwarfs. We find a similar range
in the jet efficiency for proto-BDs as measured in protostars. We have performed a study of the Brackett decrement from theBr7-Br19 lines detected in the proto-BDs. The upper Brackett lines of Br13-Br19 are only detected in the earlier stage systems.
The ratios of the different Brackett lines with respect to the Brγ line intensity are consistent with the ratios expected from CaseB recombination.

Survey of ortho-H2 D+ in high-mass star-forming regions
35. G. Sabatini, S. Bovino, A. Giannetti, F. Wyrowski, M. A. Órdenes, R. Pascale, T. Pillai, M. Wienen, T.

Csengeri, K. M. Menten (Abridged) We present a large sample of o-H2 D+ observations in high-mass star-forming regions
and discuss possible empirical correlations with relevant physical quantities to assess its role as a chronometer of star-forming
regions through different evolutionary stages. APEX observations of the ground-state transition of o-H2 D+ were analysed ina sample of massive clumps selected from ATLASGAL at different evolutionary stages. Column densities and beam-averaged
abundances of o-H2 D+ with respect to H2 , X(o-H2 D+ ), were obtained by modelling the spectra under the assumption of
local thermodynamic equilibrium. We detect 16 sources in o-H2 D+ and find clear correlations between X(o-H2 D+ ) and theclump bolometric luminosity and the dust temperature, while only a mild correlation is found with the CO-depletion factor.
In addition, we see a clear correlation with the luminosity-to-mass ratio, which is known to trace the evolution of the starformation process. This would indicate that the deuterated forms of H+
3 are more abundant in the early stages of the starformation process and that deuteration is influenced by the time evolution of the clumps. In this respect, our findings would
suggest that the X(o-H2 D+ ) abundance is mainly affected by the thermal changes rather than density changes in the gas. We

12have employed these findings together with observations of H13 CO+ , DCO+ , and C17 O to provide an estimate of the cosmic-ray
ionisation rate in a sub-sample of eight clumps based on recent analytical work. Our study presents the largest sample ofo-H2 D+ in star-forming regions to date. The results confirm that the deuteration process is strongly affected by temperatureand suggests that o-H2 D+ can be considered a reliable chemical clock during the star formation processes, as proved by its
strong temporal dependence.

36. The TW Hya Rosetta Stone Project II: Spatially resolved emission of formaldehyde

hints at low-temperature gas-phase formation

Jeroen Terwisscha van Scheltinga, Michiel R. Hogerheijde, L. Ilsedore Cleeves, Ryan A. Loomis, Catherine
Walsh, Karin I. Öberg, Edwin A. Bergin, Jennifer B. Bergner, Geoffrey A. Blake, Jenny K. Calahan, Paolo
Cazzoletti, Ewine F. van Dishoeck, Viviana V. Guzmán, Jane Huang, Mihkel Kama, Chunhua Qi, Richard
Teague, David J. Wilner Formaldehyde (H2 CO) is an important precursor to organics like methanol (CH3 OH). It is importantto understand the conditions that produce H2 CO and prebiotic molecules during star and planet formation. H2 CO possesses
both gas-phase and solid-state formation pathways, involving either UV-produced radical precursors or CO ice and cold (. 20
K) dust grains. To understand which pathway dominates, gaseous H2 CO’s ortho-to-para ratio (OPR) has been used as aprobe, with a value of 3 indicating "warm" conditions and < 3 linked to cold formation in the solid-state. We present spatiallyresolved ALMA observations of multiple ortho- and para-H2 CO transitions in the TW Hya protoplanetary disk to test H2 COformation theories during planet formation. We find disk-averaged rotational temperatures and column densities of 33 ± 2 K,
(1.1 ± 0.1) × 1012 cm−2 and 25 ± 2 K, (4.4 ± 0.3) × 1011 cm−2 for ortho- and para-H2 CO, respectively, and an OPR of 2.49 ± 0.23.
A radially resolved analysis shows that the observed H2 CO emits mostly at rotational temperatures of 30-40 K, corresponding
to a layer with z/R ≥ 0.25. The OPR is consistent with 3 within 60 au, the extent of the pebble disk, and decreases beyond 60
au to 2.0 ± 0.5. The latter corresponds to a spin temperature of 12 K, well below the rotational temperature. The combinationof relatively uniform emitting conditions, a radial gradient in the OPR, and recent laboratory experiments and theory on OPR
ratios after sublimation, lead us to speculate that gas-phase formation is responsible for the observed H2 CO across the TW Hya
disk.

37. The SEDIGISM survey: first data release and overview of the Galactic structure

SEDIGISM Collaboration, F. Schuller et al. The SEDIGISM (Structure, Excitation and Dynamics of the Inner Galactic
Interstellar Medium) survey used the APEX telescope to map 84 deg2 of the Galactic plane between l = -60 deg and l = +31
deg in several molecular transitions, including 13CO(2-1) and C18O(2-1), thus probing the moderately dense (∼ 103 cm− 3)component of the interstellar medium. With an angular resolution of 30” and a typical 1-sigma sensitivity of 0.8-1.0 K at 0.25
km/s velocity resolution, it gives access to a wide range of structures, from individual star-forming clumps to giant molecular
clouds and complexes. The coverage includes a good fraction of the first and fourth Galactic quadrants, allowing us to constrain
the large scale distribution of cold molecular gas in the inner Galaxy. In this paper we provide an updated overview of the fullsurvey and the data reduction procedures used. We also assess the quality of these data and describe the data products thatare being made publicly available as part of this first data release (DR1). We present integrated maps and position-velocity
maps of the molecular gas and use these to investigate the correlation between the molecular gas and the large scale structuralfeatures of the Milky Way such as the spiral arms, Galactic bar and Galactic centre. We find that approximately 60 per centof the molecular gas is associated with the spiral arms and these appear as strong intensity peaks in the derived Galactocentric
distribution. We also find strong peaks in intensity at specific longitudes that correspond to the Galactic centre and well known
star forming complexes, revealing that the 13CO emission is concentrated in a small number of complexes rather than evenly
distributed along spiral arms.

38. From parallel to perpendicular – On the orientation of magnetic fields in molecular

cloudsD. Seifried, S. Walch, M. Weis, S. Reissl, J. D. Soler, R. S. Klessen, P. R. Joshi We present synthetic dust polarization
maps of simulated molecular clouds (MCs) with the goal to systematically explore the origin of the relative orientation of themagnetic field (B) with respect to the MC sub-structures identified in density (n; 3D) and column density (N ; 2D). The
polarization maps are generated with the radiative transfer code POLARIS, including self-consistently calculated efficiencies
for radiative torque alignment. The MCs are formed in two sets of 3D MHD simulations: in (i) colliding flows (CF), and (ii)the SILCC-Zoom simulations. In 3D, for the CF simulations with an initial field strength below ∼5 µG, B is oriented parallelor randomly with respect to the n-structures. For CF runs with stronger initial fields and all SILCC-Zoom simulations, whichhave an initial field strength of 3 µG, a flip from parallel to perpendicular orientation occurs at high densities of ntrans ' 102 103 cm−3 . We suggest that this flip happens if the MC’s mass-to-flux ratio, µ, is close to or below the critical value of 1. This
corresponds to a field strength around 3 - 5 µG. In 2D, we use the Projected Rayleigh Statistics (PRS) to study the orientationof B. If present, the flip in orientation occurs at Ntrans ' 1021−21.5 cm−2 , similar to the observed transition value from sub- tosupercritical magnetic fields in the ISM. However, projection effects can reduce the power of the PRS method: Depending on13

the MC or LOS, the projected maps of the SILCC-Zoom simulations do not always show the flip, although expected from the
3D morphology. Such projection effects can explain the variety of recently observed field configurations, in particular within asingle MC. Finally, we do not find a correlation between the observed orientation of B and the N -PDF.

39. Atlas of CO-Line Shells and Cavities around Galactic Supernova Remnants with FUGIN
Yoshiaki Sofue, Mikito Kohno, Tomofumi Umemoto A morphological search for molecular shells and cavities was
performed around 63 Galactic supernova remnants (SNR) at 10◦ ≤ l ≤ 50◦ , |b| ≤ 1◦ using the FUGIN (FOREST
Unbiased Galactic Imaging survey with the Nobeyama 45-m telescope) CO line data at high angular (2000 ) and velocity(1.3 km s−1 ) resolutions. The results are presented as supplementary data for general purpose for investigations of
the interaction between SNRs and interstellar matter in the form of an atlas of CO-line maps superposed on radio
continuum maps at 20 cm along with a list of their kinematic distances determined from CO-line radial velocities.
(Full atlas including all figures is available in this URL: https://nro-fugin.github.io/2020-apjs-CO-Shell-Atlas-SNRFUGIN-IX.pdf)
40. An ALMA view of the Galactic super star cluster RCW38 at 270-AU resolution
Kazufumi Torii, Kazuki Tokuda, Kengo Tachihara, Toshikazu Onishi, Yasuo Fukui We report millimeter andsubmillimeter continuum and molecular line observations of the Galactic super star cluster RCW 38, obtained fromthe Atacama Large Millimeter/Submillimeter Array with a minimum angular resolution of 000 .17 × 000 .15 (' 289 AU ×
255 AU). The C18 O image reveal many massive condensations embedded within filamentary structures extending
along the northwest-southeast direction in the center of cluster. The condensations have sizes of 0.01-0.02 pc, H2column densities of 1023 -1024 cm−2 , and H2 masses of 10-130 M . In addition, the 233-GHz continuum image reveals
two dense, small millimeter-sources with radii of 460 and 200 AU (Source A and Source B). Source A is embedded
within the most massive C18 O condensation, whereas no counterpart is seen for Source B. The masses of Source A
and Source B are estimated as 13 and 3 M at the optically-thin limit, respectively. The C18 O emission shows avelocity gradient of 2 km s−1 at the central 2000 AU of Source A, which could be interpreted as a Keplerian rotation
with a central mass of a few M or infall motion of gas. Further, the ALMA 12 CO data reveal that Source A andSource B are associated with molecular outflows exhibiting maximum velocities of ∼30-70 km s−1 . The outflows haveshort dynamical timescales of <1000 yr and high mass outflow rates of ∼ 10−4 -10−3 M yr−1 . These observationalsignatures suggest an early evolutionary phase of the massive star formation in Source A and Source B.

41. SEDIGISM-ATLASGAL: Dense Gas Fraction and Star Formation Efficiency Across the

Galactic Disk
J. S. Urquhart, C. Figura, J. R. Cross, M. R. A. Wells, T. J. T. Moore, D. J. Eden, S. E. Ragan, A. R. Pettitt,
A. Duarte-Cabral, D. Colombo, F. Schuller, T. Csengeri, M. Mattern, H. Beuther, K. M. Menten, F. Wyrowski,
L. D. Anderson, P. J. Barnes, M. T. Beltrán, S. J. Billington, L. Bronfman, A. Giannetti, J. Kainulainen, J.
Kauffmann, M. -Y. Lee, S. Leurini, S. -N. X. Medina, F. M. Montenegro-Montes, M. Riener, A. J. Rigby, A.
Sánchez-Monge, P. Schilke, E. Schisano, A. Traficante, M. Wienen By combining two surveys covering a large

fraction of the molecular material in the Galactic disk we investigate the role the spiral arms play in the star formation
process. We have matched clumps identified by ATLASGAL with their parental GMCs as identified by SEDIGISM,
and use these giant molecular cloud (GMC) masses, the bolometric luminosities,
and integrated clump masses obtainedP
in a concurrent paper to estimate P
the dense gas fractions (DGFgmc =Mclump /Mgmc ) and the instantaneous star
forming efficiencies (i.e., SFEgmc = Lclump /Mgmc ). We find that the molecular material associated with ATLASGAL
clumps is concentrated in the spiral arms (∼60searched for variations in the values of these physical parameters withrespect to their proximity to the spiral arms, but find no evidence for any enhancement that might be attributable tothe spiral arms. The combined results from a number of similar studies based on different surveys indicate that, whilespiral-arm location plays a role in cloud formation and HI to H2 conversion, the subsequent star formation processes
appear to depend more on local environment effects. This leads us to conclude that the enhanced star formation
activity seen towards the spiral arms is the result of source crowding rather than the consequence of a any physicalprocess.

14

42.

The asymmetric inner disk of the Herbig Ae star HD 163296 in the eyes of VLTI/MATISSE:
evidence for a vortex?
MATISSE Collaboration, J. Varga et al. Context. The inner few au region of planet-forming disks is a complex

environment. High angular resolution observations have a key role in understanding the disk structure and the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of
the inner disk of the young intermediate-mass star HD 163296, from VLTI/MATISSE observations. Methods. We
use geometric models to fit the data. Our models include a smoothed ring, a flat disk with inner cavity, and a 2D
Gaussian. The models can account for disk inclination and for azimuthal asymmetries as well. We also perform
numerical hydro-dynamical simulations of the inner edge of the disk. Results. Our modeling reveals a significant
brightness asymmetry in the L-band disk emission. The brightness maximum of the asymmetry is located at theNW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio in theazimuthal variation is 3.5 ± 0.2. Comparing our result on the location of the asymmetry with other interferometricmeasurements, we confirm that the morphology of the r < 0.3 au disk region is time-variable. We propose that thisasymmetric structure, located in or near the inner rim of the dusty disk, orbits the star. For the physical origin of theasymmetry, we tested a hypothesis where a vortex is created by Rossby wave instability, and we find that a uniquelarge scale vortex may be compatible
with our data. The half-light radius of the L-band emitting region is 0.33 ± 0.01◦
au, the inclination is 52◦ +5
,
and
the
position angle is 143◦ ± 3◦ . Our models predict that a non-negligible fraction of◦−7
the L-band disk emission originates inside the dust sublimation radius for µm-sized grains. Refractory grains or large(& 10 µm-sized) grains could be the origin for this emission.

43.

On the pumping of the CS(v = 0) masers in W51 e2eD. J. van der Walt, A. Ginsburg, C. Goddi We present the results of numerically solving the rate equations forthe first 31 rotational states of CS in the ground vibrational state to determine the conditions under which the
J=1-0, J=2-1 and J=3-2 transitions are inverted to produce maser emission. The essence of our results is that theCS(v = 0) masers are collisionally pumped and that, depending on the spectral energy distribution, dust emission can
suppress the masers. Apart from the J=1-0 and J=2-1 masers the calculations also show that the J=3-2 transition
can be inverted to produce maser emission. It is found that beaming is necessary to explain the observed brightness
temperatures of the recently discovered CS masers in W51 e2e. The model calculations suggest that a CS abundanceof a few times 10−5 and CS(v = 0) column densities of the order 1016 cm−2 are required for these masers. The rarityof the CS masers in high mass star forming regions might be the result of a required high CS abundance as well as
due to attenuation of the maser emission inside as well as outside of the hot core.

44.

Constraining the magnetic field properties of Bok globule B335 using SOFIA/HAWC+
Niko Zielinski, Sebastian Wolf, Robert Brunngräber Thanks to their well-defined shape and mostly isolated loca-

tions, Bok globules are suitable objects for studying the physics of low-mass star formation. To study the magnetic
field of the prototypical Bok globule B335, we obtained a spatially resolved polarization map with SOFIA/HAWC+ at
a wavelength of 214 µm. For the first time, these observations reveal that polarization holes in Bok globules, that is,the decrease in polarization degree towards their dense centers, also occur in the far-infrared wavelength regime. The
observed polarization pattern is uniform with a mean polarization angle of 48◦ ±26◦ and a magnetic field strength of∼ 142 µG. Moreover, we use complementary polarimetic data for B335 obtained at near-infrared to millimeter wavelengths to analyze and constrain the magnetic field across different scales. By applying the 3D Monte-Carlo radiativetransfer code POLARIS (Reissl et al. 2016), we developed a model for the density and magnetic field structure aswell as for the dust properties of this globule. We conclude that the column density towards the center of B335 is too
low to cause the observed polarization hole in B335 via dichroic absorption (Brauer et al. 2016). Furthermore, we
conclude that the effect of self-scattering has no significant impact on the observed polarization. Adopting dust-grainalignment via the radiative torque mechanism, a combination of the interstellar radiation field and the central star asradiation sources is consistent with the decrease in polarization degree at the outer regions of B335 (≈ 104 au from thecore). However, the model fails to explain the low polarization degree within the inner 5000 au.

15

45.

Search for associations containing young stars (SACY) VIII. An updated census ofspectroscopic binary systems showing hints of non-universal multiplicity among theseassociations
S. Zúñiga-Fernández, A. Bayo, P. Elliott, C. Zamora, G. Corvalán, X. Haubois, J. M. Corral-Santana, J.
Olofsson, N. Huélamo, M. F. Sterzik, C. A. O. Torres, G. R. Quast, C. H. F. Melo We seek to update thespectroscopy binary fraction of the SACY (Search for Associations Containing Young stars) sample taking in consideration all possible biases in our identification of binary candidates, such as activity and rotation. Using high-resolution
spectroscopic observations we have produced ∼1300 cross-correlation functions (CCFs) to disentangle the previously
mentioned sources of contamination. The radial velocity values obtained were cross-matched with the literature andwere used to revise and update the spectroscopic binary (SB) fraction in each of the SACY association. In order tobetter describe the CCF profile, we calculated a set of high-order cross-correlation features to determine the originof the variations in radial velocities. We identified 68 SB candidates from our sample of 410 objects. Our results
hint that the youngest associations have a higher SB fraction. Specifically, we found sensitivity-corrected SB fractions
+15
+16
+9
of 22−11% for  Cha , 31−14% for TW Hya and 32−8
% for β Pictoris, in contrast with the five oldest (∼ 35 − 125Myr) associations we have sampled which are ∼ 10% or lower. This result seems independent of the methodology
used to asses membership to the associations. The new CCF analysis, radial velocity estimates and SB candidates
are particularly relevant for membership revision of targets in young stellar associations. These targets would be ideal
candidates for follow-up campaigns using high-resolution techniques in order to confirm binarity, resolve the orbits,
and ideally calculate dynamical masses. Additionally, if the results on SB fraction in the youngest associations are
confirmed, it could hint of non-universal multiplicity among SACY associations.

16