The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 353 — 31 May 2022
Editor: João Alveswww.starformation.news

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Cover image caption
The environment of star cluster RCW 38 in all (seen left-up of center). The cluster, with an age of about 1 Myr, is completely
invisible at optical wavelengths. This NIR image shows the cluster embedded in its complex birthplace of in exquisite detail.
This star forming region lies about 1700 pc from Earth in the direction of Vela. The image covers about 10 arcmin on the side,or about 5×5 pc at the distance of the cluster. Credit: ESO HAWK-I camera with the GRAAL adaptive optics system and K.
Muzic
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. Do not remove the LATEX formatting
when submitting to the arXiv. If you do, your abstract will not look great either at the arXiv or the SFN.

Abstracts
1. Interstellar detection and chemical modeling of iso-propanol and its normal isomerA. Belloche, R. T. Garrod, O. Zingsheim, H. S. P. Müller, K. M. Menten F The detection of a branched alkyl
molecule in the high-mass star forming protocluster Sgr B2(N) permitted by the advent of ALMA revealed a new dimension ofinterstellar chemistry. Astrochemical simulations subsequently predicted that beyond a certain degree of molecular complexity,
branched molecules could even dominate over their straight-chain isomers. More generally, we aim at probing further thepresence in the ISM of complex organic molecules with the capacity to exhibit both a normal and iso form, via the attachmentof a functional group to either a primary or secondary carbon atom. We used the imaging spectral line survey survey ReMoCA
performed with ALMA and the results of a recent spectroscopic study of propanol to search for the iso and normal isomersof this molecule in the hot molecular core Sgr B2(N2). We expanded the network of the astrochemical model MAGICKAL to
explore the formation routes of propanol. We report the first interstellar detection of iso-propanol toward a position of Sgr
B2(N2) that shows narrow linewidths. We also report the first secure detection of normal-propanol in a hot core. i-Propanol
is found to be nearly as abundant as n-propanol, with an abundance ratio of 0.6 similar to the ratio of 0.4 that we obtained
previously for i- and n-propyl cyanide in Sgr B2(N2). The results are in good agreement with the outcomes of our astrochemical
models, which indicate that OH-radical addition to propylene in dust-grain ice mantles, driven by water photodissociation, canproduce appropriate quantities of n- and i-propanol. The n-to-i ratio in Sgr B2(N2) may be a direct inheritance of the branchingratio of this reaction process. The detection of n- and i-propanol and their ratio indicate that the modest preference toward thenormal form of propyl cyanide determined previously may be a more general feature among similarly sized interstellar molecules.
[abridged]

Bias and Young Massive Cluster Characterisation I. 2D Perspective Ef2. Observational
fects
Anne S. M. Buckner, Kong You Liow, Clare L. Dobbs, Tim Naylor, Steven Rieder F Understanding the formation and evolution of high mass star clusters requires comparisons between theoretical and observational data to be made.
Unfortunately, while the full phase space of simulated regions is available, often only partial 2D spatial and kinematic data
is available for observed regions. This raises the question as to whether cluster parameters determined from 2D data alone
are reliable and representative of clusters real parameters and the impact of line-of-sight orientation. In this paper we deriveparameters for a simulated cluster formed from a cloud-cloud collision with the full 6D phase space, and compare them withthose derived from three different 2D line-of-sight orientations for the cluster. We show the same qualitative conclusions can bereached when viewing clusters in 2D versus 3D, but that drawing quantitative conclusions when viewing in 2D is likely to beinaccurate. The greatest divergence occurs in the perceived kinematics of the cluster, which in some orientations appears to be
expanding when the cluster is actually contracting. Increases in the cluster density compounds pre-existing perspective issues,
reducing the relative accuracy and consistency of properties derived from different orientations. This is particularly problematic2

for determination of the number, and membership, of subclusters present in the cluster. We find the fraction of subclusters
correctly identified in 2D decreases as the cluster evolves, reaching less than 3.4the evolutionary end point for our cluster.

the Giant HII Regions of the Milky Way with SOFIA: IV. Sgr D, W42, and
3. Surveying
a Reassessment of the Giant HII Region Census
James M. De Buizer, Wanggi Lim, Nicole Karnath, James T. Radomski, Lars Bonne F This is the fourth paper
exploring the infrared properties of giant HII regions with the FORCAST instrument on the Stratospheric Observatory For
Infrared Astronomy (SOFIA). Our survey utilizes the census of 56 Milky Way giant HII regions identified by Conti & Crowther(2004), and in this paper we present the 20 and 37 micron imaging data we have obtained from SOFIA for sources Sgr D and
W42. Based upon the SOFIA data and other multi-wavelength data, we derive and discuss the detailed physical properties of
the individual compact sources and sub-regions as well as the large scale properties of Sgr D and W42. However, improved
measurements have revealed much closer distances to both regions than previously believed, and consequently both sources
are not powerful enough to be considered giant HII regions any longer. Motivated by this, we revisit the census of giant HII
regions, performing a search through the last two decades of literature to update each source with the most recent and/or mostaccurate distance measurements. Based on these new distance estimates, we determine that 14 sources in total (25reliable andcloser distances that they are not powerful enough to be considered giant HII regions. We briefly discuss the observational
and physical characteristics specific to Sgr D and W42 and show that they have properties distinct from the giant HII regions
previously studied as a part of this survey.

Dust coagulation during the early stages of star formation: molecular cloud collapse

4. and first hydrostatic core evolution

Matthew R. Bate F Planet formation in protoplanetary discs requires dust grains to coagulate from the sub-micron sizes
that are found in the interstellar medium into much larger objects. For the first time, we study the growth of dust grains during
the earliest phases of star formation using three-dimensional hydrodynamical simulations. We begin with a typical interstellar
dust grain size distribution and study dust growth during the collapse of a molecular cloud core and the evolution of the firsthydrostatic core, prior to the formation of the stellar core. We examine how the dust size distribution evolves both spatiallyand temporarily. We find that the envelope maintains its initial population of small dust grains with little growth during thesephases, except that in the inner few hundreds of au the smallest grains are depleted. However, once the first hydrostatic core
forms rapid dust growth to sizes in excess of 100 µm occurs within the core (before stellar core formation). Progressively
larger grains are produced at smaller distances from the centre of the core. In rapidly-rotating molecular cloud cores, the ‘firsthydrostatic core’ that forms is better described as a pre-stellar disc that may be gravitationally unstable. In such cases, grain
growth is more rapid in the spiral density waves leading to the larger grains being preferentially found in the spiral waves eventhough there is no migration of grains relative to the gas. Thus, the grain size distribution can vary substantially in the firstcore/pre-stellar disc even at these very early times.

5. Discovery of a 500 au Protobinary in the Massive Prestellar Core G11.92-0.61 MM2

C. J. Cyganowski, J. D. Ilee, C. L. Brogan, T. R. Hunter, S. Zhang, T. J. Harries, T. J. Haworth F We present
high-resolution (< 160 au) Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm observations of the high-mass
prestellar core candidate G11.92-0.61 MM2, which reveal that this source is in fact a protobinary system with a projected
separation of 505 au. The binary components, MM2E and MM2W, are compact (radii < 140 au) sources within the partially
optically thick dust emission with alpha0.9cm−1.3mm =2.47-2.94. The 1.3 mm brightness temperatures, Tb =68.4/64.6 K for
MM2E/MM2W, imply internal heating and minimum luminosities L∗ > 24.7 Lsun for MM2E and L∗ > 12.6 Lsun for MM2W.
The compact sources are connected by a "bridge" of lower-surface-brightness dust emission and lie within more extended
emission that may correspond to a circumbinary disk. The circumprotostellar gas mass, estimated from 0.2" resolution VLA
0.9 cm observations assuming optically thin emission, is 6.8+/-0.9 Msun. No line emission is detected towards MM2E andMM2W in our high-resolution 1.3 mm ALMA observations. The only line detected is 13CO J=2-1, in absorption against the
1.3 mm continuum, which likely traces a layer of cooler molecular material surrounding the protostars. We also report thediscovery of a highly asymmetric bipolar molecular outflow that appears to be driven by MM2E and/or MM2W in new deep,
0.5" resolution (1680 au) ALMA 0.82 mm observations. This outflow, traced by low-excitation CH3OH emission, indicatesongoing accretion onto the protobinary system. Overall, the super-Alfvenic models of Mignon-Risse et al. (2021) agree wellwith the observed properties of the MM2E/MM2W protobinary, suggesting that this system may be forming in an environment
with a weak magnetic field.

36. The Role of Magnetic Fields in Triggered Star Formation of RCW 120

Zhiwei Chen, Ramotholo Sefako, Yang Yang, Zhibo Jiang, Shuling Yu, Jia Yin F We report on the near-IR
polarimetric observations of RCW 120 with the 1.4 m IRSF telescope. The starlight polarization of the background stars reveal
for the first time the magnetic field of RCW 120. The global magnetic field of RCW 120 is along the direction of 20◦ , parallel tothe galactic plane. The field strength on the plane of the sky is 100 ± 26 µG. The magnetic field around the eastern shell shows
evidence of compression by the HII region. The external pressure (turbulent pressure + magnetic pressure) and the gas densityof the ambient cloud are minimum along the direction where RCW 120 breaks out, which explains the observed elongation of
RCW 120. The dynamical age of RCW 120, depending on the magnetic field strength, is ∼ 1.6 Myr for field strength of 100 µG,
older than the hydrodynamic estimates. In direction perpendicular to the magnetic field, the density contrast of the westernshell is greatly reduced by the strong magnetic field. The strong magnetic field in general reduces the efficiency of triggered starformation, in comparison with the hydrodynamic estimates. Triggered star formation via the "collect and collapse" mechanism
could occur in the direction along the magnetic field. Core formation efficiency (CFE) is found to be higher in the southern andeastern shells of RCW 120 than in the infrared dark cloud receiving little influence from the HII region, suggesting increase in
the CFE related to triggering from ionization feedback.

rates in hierarchical triple systems with discs
7. Accretion
Simone Ceppi, Nicolás Cuello, Giuseppe Lodato, Cathie Clarke, Claudia Toci, Daniel J. Price F Young multiple
systems accrete most of their final mass in the first few Myr of their lifetime, during the protostellar and protoplanetary phases.
Previous studies showed that in binary systems the majority of the accreted mass falls onto the lighter star, thus evolving tomass equalisation. However, young stellar systems often comprise more than two stars, which are expected to be in hierarchicalconfigurations. Despite its astrophysical relevance, differential accretion in hierarchical systems remains to be understood. In
this work, we investigate whether the accretion trends expected in binaries are valid for higher order multiples. We performed aset of 3D Smoothed Particle Hydrodynamics simulations of binaries and of hierarchical triples (HTs) embedded in an accretion
disc, with the code Phantom. We identify for the first time accretion trends in HTs and their deviations compared to binaries.
These deviations, due to the interaction of the small binary with the infalling material from the circum-triple disc, can be
described with a semi-analytical prescription. Generally, the smaller binary of a HT accretes more mass than a single star of
the same mass as the smaller binary. We found that in a HT, if the small binary is heavier than the third body, the standard
differential accretion scenario (whereby the secondary accretes more of the mass) is hampered. Reciprocally, if the small binary
is lighter than the third body, the standard differential accretion scenario is enhanced. The peculiar differential accretionmechanism we find in HTs is expected to affect their mass ratio distribution.

8. A giant planet shaping the disk around the very low mass star CIDA 1

P. Curone, A. F. Izquierdo, L. Testi, G. Lodato, S. Facchini, A. Natta, P. Pinilla, N. T. Kurtovic, C. Toci,
M. Benisty, M. Tazzari, F. Borsa, M. Lombardi, C. F. Manara, E. Sanchis, L. Ricci F (Abridged) Exoplanetary
research has provided us with exciting discoveries of planets around very low mass (VLM) stars (e.g., TRAPPIST-1 and Proxima
Centauri). However, current theoretical models strive to explain planet formation in these conditions and do not predict thedevelopment of giant planets. Recent high-resolution observations from ALMA of the disk around CIDA 1, a VLM star in
Taurus, show substructures hinting at the presence of a massive planet. We aim to reproduce the dust ring of CIDA 1, observedin the dust continuum emission in ALMA Band 7 (0.9 mm) and Band 4 (2.1 mm), along with its 12 CO (J=3-2) and 13 CO (J=3-2)
channel maps, assuming the structures are shaped by the interaction of the disk with a massive planet. We seek to retrieve themass and position of the putative planet. We model the protoplanetary disk with a set of hydrodynamical simulations, varying
the mass and locations of the embedded planet. We compute the dust and gas emission using radiative transfer simulations,and, finally, we obtain the synthetic observations treating the images as the actual ALMA observations. Our models indicatethat a planet with a minimum mass of ∼ 1.4 MJup orbiting at a distance of ∼ 9 − 10 au can explain the morphology and locationof the observed dust ring at Band 7 and Band 4. We can reproduce the low spectral index (∼ 2) observed where the dust ringis detected. Our synthetic images reproduce the morphology of the 12 CO and 13 CO observed channel maps where the cloudabsorption allowed a detection. Applying an empirical relation between planet mass and gap width in the dust, we predict a
maximum planet mass of ∼ 4 − 8 MJup . Our results suggest the presence of a massive planet orbiting CIDA 1, thus challenging
our understanding of planet formation around VLM stars.

pressure gradients with the stability of molecular clouds in galactic outflows
9. Linking
K. M. Dasyra, G. F. Paraschos, T. Bisbas, F. Combes, J. A. Fernandez-Ontiveros F The jets launched by actively
accreting black holes are capable of launching several of the massive (million or billion solar mass) molecular outflows observedin galaxies. These outflows could suppress or enhance star formation in galaxies. To investigate the stability of clouds capable
to form stars in outflows, we modeled CO and HCO+ ALMA data of the galaxy IC5063, in which black-hole jets impact
molecular clouds. Using a radiative transfer code that self-consistently performs astrochemical and thermal balance calculations
based on the available gas heating sources, we found that mechanical heating and cosmic ray (CR) heating are fully capable4

of individually reproducing the data. In our best-fit model, CRs provide about 1/3rd of the dense gas heating at the radio
lobes, emphasizing the role of this often neglected mechanism in heating the gas and potentially generating outflows. The gas
temperature and density indicate that the jet passage leads to an increase of about 1 order of magnitude in the internal pressure
Pi of molecular clouds (with Pi/k from 8*105 up to 7*106 K cm−3 ), irrespective of the excitation mechanism. From the fluxesof [S II] and [N II] lines in VLT MUSE data, the external pressure Pe of molecular clouds increases in several regions enoughto exceed Pi. This result leads us to conclude that we are observing the expansion of an ionized overpressurized cocoon thatcompresses molecular clouds and that could lead to their collapse. Some jet-impacted clouds, nonetheless, near pathways thatthe jet cleared have increased Pi and decreased Pe. They are likely to undergo evaporation of their outer layers. Part of theevaporated layers could mass load the outflow thanks to ram pressure from co-spatial ionized gas flows. The observed pressurechanges thus suggest that both star formation enhancement and suppression could simultaneously occur.

Clumpy accretion in pre-main-sequence stars as a source of perturbations in circum-

10. stellar disks

Tatiana V. Demidova, Vladimir P. Grinin F The development of perturbations in the circumstellar disks of pre-mainsequence stars caused by clumpy accretion was investigated. Here we perform 3D hydrodynamical smoothed particle hydrodynamics simulations of disks perturbed by a recent clump accretion event. These simulations are further explored by radiativetransfer calculations to quantify the observational appearance of such disks. It was shown that the density waves in the disks
were formed at the fall of the clump. After several revolutions they can transform into spirals and ring structures. Their
images in millimeter wavelengths are very similar to those observed with Atacama Large Millimeter/submillimeter Array insome protoplanetary disks. We assume that clumpy accretion may be the source of such structures.

11. The Great Planetary Heist: Theft and capture in star-forming regions

Emma C. Daffern-Powell, Richard J. Parker, Sascha P. Quanz F Gravitational interactions in star-forming regions
are capable of disrupting and destroying planetary systems, as well as creating new ones. In particular, a planet can be stolen,
where it is directly exchanged between passing stars during an interaction; or captured, where a planet is first ejected from its
birth system and is free-floating for a period of time, before being captured by a passing star. We perform sets of direct N-bodysimulations of young, substructured star-forming regions, and follow their evolution for 10 Myr in order to determine how many
planets are stolen and captured, and their respective orbital properties. We show that in high density star-forming regions,stolen and captured planets have distinct properties. The semimajor axis distribution of captured planets is significantly skewed
to wider orbits compared to the semimajor axis distribution of stolen planets and planets that are still orbiting their parent
star (preserved planets). However, the eccentricity and inclination distributions of captured and stolen planets are similar, but
in turn very different to the inclination and eccentricity distributions of preserved planets. In low-density star-forming regions
these differences are not as distinct but could still, in principle, be used to determine whether observed exoplanets have likely
formed in situ or have been stolen or captured. We find that the initial degree of spatial and kinematic substructure in astar-forming region is as important a factor as the stellar density in determining whether a planetary system will be altered,disrupted, captured or stolen.

12. The young stars in the Galactic Center

Sebastiano von Fellenberg, Stefan Gillessen, Julia Stadler, Michi Bauböck, Reinhard Genzel, Tim de Zeeuw,
Oliver Pfuhl, Pau Amaro Seoane, Antonia Drescher, Frank Eisenhauer, Maryam Habibi, Thomas Ott, Felix
Widmann, Alice Young F We present a large ∼ 30” × 30” spectroscopic survey of the Galactic Center using the SINFONIIFU at the VLT. Combining observations of the last two decades we compile spectra of over 2800 stars. Using the Bracket-γ
absorption lines we identify 195 young stars, extending the list of known young stars by 79. In order to explore the angularmomentum distribution of the young stars, we introduce an isotropic cluster prior. This prior reproduces an isotropic cluster ina mathematically exact way, which we test through numerical simulations. We calculate the posterior angular momentum spaceas function of projected separation from Sgr A*. We find that the observed young star distribution is substantially different
from an isotropic cluster. We identify the previously reported feature of the clockwise disk and find that its angular momentum
changes as function of separation from the black hole, and thus confirm a warp of the clockwise disk (p ∼ 99.2%). At large
separations, we discover three prominent overdensities of angular momentum. One overdensity has been reported previously,
the counter-clockwise disk. The other two are new. Determining the likely members of these structures, we find that as many as
75% of stars can be associated with one of these features. Stars belonging to the warped clockwise-disk show a top heavy K-band
luminosity function, while stars belonging to the larger separation features do not. Our observations are in good agreementwith the predictions of simulations of in-situ star formation, and argue for common formation of these structures.

513. Curved jet motion. I. Orbiting and precessing jets
Christian Fendt, Melis Yardimci F Astrophysical jets are often observed as bent or curved structures. We also know thatthe different jet sources may be binary in nature, which may lead to a regular, periodic motion of the jet nozzle, an orbital
motion or precession. Here, we present the results of 2D (M)HD simulations in order to investigate how a precessing or orbiting
jet nozzle affects the propagation of a high-speed jet. We have performed a parameter study of systems with different precession
angles, orbital periods or separations, and different magnetic field strengths. We find that these kinds of nozzles lead to curved
jet propagation which is determined by the main parameters that define the jet nozzle. We find C-shaped jets from orbiting
nozzles and S-shaped jets from precessing nozzles. Over long time and long distances, the initially curved jet motion bores
a broad channel into the ambient gas that is filled with high-speed jet material which lateral motion is damped, however. A
strong (longitudinal) magnetic field can damp the jet curvature that is enforced by either precession of orbital motion of thejet sources. We have investigated the force balance across the jet and ambient medium and found that the lateral magnetic
pressure and gas pressure gradients are almost balanced, but that a lack of gas pressure on the concave side of the curvature isleading to the lateral motion. Magnetic tension does not play a significant role. Our results are obtained in code units, but weprovide scaling relations such that our results may be applied to young stars, micro-quasars, symbiotic stars or AGN.

Interplay between Young Stars and Molecular Clouds in the Ophiuchus Star-forming

14. Complex

Aashish Gupta, Wen-Ping Chen F We present spatial and kinematic correlation between the young stellar populationand the cloud clumps in the Ophiuchus star-forming region. The stellar sample consists of known young objects at various
evolutionary stages, taken from the literature, some of which are diagnosed with Gaia EDR3 parallax and proper-motion
measurements. The molecular gas is traced by the 850 µm Submillimetre Common-User Bolometer Array-2 image, reaching∼2.3 mJy beam−1 , the deepest so far for the region, stacked from the James Clerk Maxwell Telescope/Transient programaiming to detect submillimeter outburst events. Our analysis indicates that the more evolved sources, namely the class II and
III young stars, are located further away from clouds than class I and flat-spectrum sources that have ample circumstellar
matter and are closely associated with natal clouds. Particularly the class II and III population is found to exhibit a structured
spatial distribution indicative of passage of shock fronts from the nearby Sco-Cen OB association thereby compressing clouds
to trigger star formation, with the latest starbirth episode occurring now in the densest cloud filaments. The young stars at all
evolutionary stages share similar kinematics. This suggests that the stellar patterns trace the relics of parental cloud filamentsthat now have been dispersed.

shells around young clusters – S 171/Be 59
15. Expanding
G. F. Gahm, M. J. C. Wilhelm, C. M. Persson, A. A. Djupvik, S. F. Portegies Zwart F Some HII regions thatsurround young stellar clusters are bordered by molecular shells that appear to expand at a rate inconsistent with our current
model simulations. In this study we focus on the dynamics of Sharpless 171 (including NGC 7822), which surrounds the cluster
Berkeley 59. We aim to compare the velocity pattern over the molecular shell with the mean radial velocity of the cluster for
estimates of the expansion velocities of different shell structures, and to match the observed properties with model simulations.
Optical spectra of 27 stars located in Berkeley 59 were collected at the Nordic Optical Telescope, and a number of molecular
structures scattered over the entire region were mapped in 13 CO(1-0) at Onsala Space Observatory. We obtained radial velocities
and MK classes for the cluster’s stars. At least four of the O stars are found to be spectroscopic binaries, in addition to one
triplet system. From these data we obtain the mean radial velocity of the cluster. From the 13 CO spectra we identify threeshell structures, expanding relative to the cluster at moderate velocity (4 km/s), high velocity (12 km/s), and in between.
The high-velocity cloudlets extend over a larger radius and are less massive than the low-velocity cloudlets. We performed amodel simulation to understand the evolution of this complex. Our simulation of the Sharpless 171 complex and Berkeley 59
cluster demonstrates that the individual components can be explained as a shell driven by stellar winds from the massive cluster
members. However, our relatively simple model produces a single component. Modelling of the propagation of shell fragments
through a uniform interstellar medium demonstrates that dense cloudlets detached from the shell are decelerated less efficiently
than the shell itself. They can reach greater distances and retain higher velocities than the shell.

Capture Model for Asymmetric Molecular Emission Lines Observed in TMC16. Cloudlet
1A with ALMA
Tomoyuki Hanawa, Nami Sakai, Satoshi Yamamoto F TMC-1A is a protostellar source harboring a young protostar,
IRAS 04365+2353, and shows a highly asymmetric features of a few 100 au scale in the molecular emission lines. Blue-shifted
emission is much stronger in the CS (J = 5-4) line than red-shifted one. The asymmetry can be explained if the gas accretion is
episodic and takes the form of cloudlet capture, given the cloudlet approached toward us. The gravity of the protostar transforms
the cloudlet into a stream and changes its velocity along the flow. The emission from the cloudlet should be blue-shifted before
the periastron, while it should be red-shifted after the periastron. If a major part of cloudlet has not reached the periastron, theformer should be dominant. We perform hydrodynamical simulations to examine the validity of the scenario. Our numerical6

simulations can reproduce the observed asymmetry if the orbit of the cloudlet is inclined to the disk plane. The inclination
can explain the slow infall velocity observed in the C18 O (J=2-1) line emission. Such episodic accretion may occur in various
protostellar cores since actual clouds could have inhomogeneous density distribution. We also discuss the implication of thecloudlet capture on observations of related objects.

in Nearby Young Stellar Associations Found Via Virtual Reality
17. Disks
Susan Higashio, Marc J. Kuchner, Steven M. Silverberg, Matthew A. Brandt, Thomas G. Grubb, Jonathan
Gagné, John H. Debes, Joshua Schlieder, John P. Wisniewski, Stewart Slocum, Alissa S. Bans, Shambo Bhattacharjee, Joseph R. Biggs, Milton K. D. Bosch, Tadeas Cernohous, Katharina Doll, Hugo A. Durantini Luca,
Alexandru Enachioaie, Phillip Griffith Sr., Joshua Hamilton, Jonathan Holden, Michiharu Hyogo, Dawoon
Jung, Lily Lau, Fernanda Piñiero Art Piipuu, Lisa Stiller, Disk Detective Collaboration F The Disk Detective
citizen science project recently released a new catalog of disk candidates found by visual inspection of images from NASA’s
Wide-Field Infrared Survey Explorer (WISE) mission and other surveys. We applied this new catalog of well-vetted disk candidates to search for new members of nearby young stellar associations (YSAs) using a novel technique based on Gaia data
and virtual reality (VR). We examined AB Doradus, Argus, β Pictoris, Carina, Columba, Octans-Near, Tucana-Horologium,
and TW Hya by displaying them in VR together with other nearby stars, color-coded to show infrared excesses found via Disk
Detective. Using this method allows us to find new association members in mass regimes where isochrones are degenerate. We
propose ten new YSA members with infrared excesses: three of AB Doradus (HD 44775, HD 40540 and HD 44510), one of βPictoris (HD 198472), two of Octans-Near (HD 157165 and BD+35 2953), and four disk-hosting members of a combined population of Carina, Columba and Tucana-Horologium: CPD-57 937, HD 274311, HD 41992, and WISEA J092521.90-673224.8. This
last object (J0925) appears to be an extreme debris disk with a fractional infrared luminosity of 3.7 × 10−2 . We also propose
two new members of AB Doradus that do not show infrared excesses: TYC 6518-1857-1 and CPD-25 1292. We find HD 15115
appears to be a member of Tucana-Horologium rather than β Pictoris. We advocate for membership in Columba-Carina of HD
30447, CPD-35 525, and HD 35841. Finally, we propose that three M dwarfs, previously considered members of Tuc-Hor are
better considered a separate association, tentatively called “Smethells 165”.

18. Unveiling the outer dust disc of TW Hya with deep ALMA observations

John D. Ilee, Catherine Walsh, Jeff Jennings, Richard A. Booth, Giovanni P. Rosotti, Richard Teague, Takashi
Tsukagoshi, Hideko Nomura F The radial extent of millimetre dust in protoplanetary discs is often far smaller than thatof their gas, mostly due to processes such as dust growth and radial drift. However, it has been suggested that current
millimetre continuum observations of discs do not trace their full extent due to limited sensitivity. In this Letter, we present
deep (19 µJy beam−1 ) moderate resolution (0.37") ALMA observations at 1 mm of the nearest protoplanetary disc, TW Hya.
Using the visibility analysis tool ‘frank’, we reveal a structured millimetre intensity distribution out to 100 au, well beyond
previous estimates of 60-70 au. Our analysis suggests the presence of a new millimetre continuum gap at 82 au, coincident withsimilar features seen in optical/near-infrared scattered light and millimetre molecular line observations. Examination of the
fit residuals confirms the presence of the previously reported au-scale continuum excess at 52 au (P.A. = 242.5 degrees). Our
results demonstrate the utility of combining deep, moderate resolution observations with super-resolution analysis techniques
to probe the faintest regions of protoplanetary discs.

Growth after the streaming instability: The radial distance dependence of the planetary

19. growthHyerin Jang, Beibei Liu, Anders Johansen F Streaming instability is hypothesized to be triggered at particular protoplanetary disk locations where the volume density of the solid particles is enriched comparable to that of the gas. A ring ofplanetesimals thus forms when this condition is fulfilled locally. These planetesimals collide with each other and accrete inward
drifting pebbles from the outer disk to further increase masses. We investigate the growth of the planetesimals that form ina ring-belt at various disk radii. Their initial mass distributions are calculated based on the formula summarized from thestreaming instability simulations. We simulate the subsequent dynamical evolution of the planetesimals with a protoplanetary
disk model based either on the minimum mass solar nebula (MMSN) or on the Toomre stability criterion. For the MMSN
model, both pebble accretion and planetesimal accretion are efficient at a close-in orbit of 0.3 AU, resulting in the emergence ofseveral super-Earth mass planets after 1 Myr. For comparison, only the most massive planetesimals undergo substantial mass
growth when they are born at r=3 AU, while the planetesimals at r=30 AU experience little or no growth. On the other hand,in the denser Toomre disk, the most massive forming planets can reach Earth mass at t=1 Myr and reach a mass between thatof Neptune and that of Saturn within 3 Myr at 30 AU and 100 AU. Both the pebble and planetesimal accretion rate decrease
with disk radial distance. Nevertheless, planetesimal accretion is less pronounced than pebble accretion at more distant disk
regions. Taken together, the planets acquire higher masses when the disk has a higher gas density, a higher pebble flux, and/or
a lower Stokes number of pebbles.

7Effect of Molecular Cloud Properties on the Kinematics of Stars Formed in the
20. TheTrifid Region
Michael A. Kuhn, Lynne A. Hillenbrand, Eric D. Feigelson, Ian Fowler, Konstantin V. Getman, Patrick S.
Broos, Matthew S. Povich, Mariusz Gromadzki F The dynamical states of molecular clouds may affect the propertiesof the stars they form. In the vicinity of the Trifid Nebula (d = 1180 ± 25 pc), the main star cluster (Trifid Main) lies within
an expanding section of the molecular cloud; however, 0.3 deg to the north (Trifid North), the cloud’s velocity structure ismore tranquil. We acquired a Chandra X-ray observation to identify pre-main-sequence stars in Trifid North, complementing
a previous observation of Trifid Main. In Trifid North, we identified 51 candidate pre-main-sequence stars, of which 13 arehigh-confidence Trifid members based on Gaia EDR3 parallaxes and proper motions. We also re-analyzed membership of Trifid
Main and separated out multiple background stellar associations. Trifid North represents a stellar population 10in a separate
part of the cloud. The 1D stellar velocity dispersion in Trifid North (0.6 ± 0.2 km/s) is three times lower than in Trifid Main
(1.9 ± 0.2 km/s). Furthermore, in Trifid Main, proper motions indicate that the portion of the star cluster superimposed on
the optical nebula is expanding. Expansion of the HII region around the O-star HD 164492A, and the resulting gas expulsion,can explain both the motions of the stars and gas in Trifid Main. Contrary to previous studies, we find no evidence that acloud-cloud collision triggered star formation in the region.

21. Fevering Interstellar Ices Have More CH3OD

Beatrice M. Kulterer, Maria N. Drozdovskaya, Stefano Antonellini, Catherine Walsh, Tom J. Millar F Monodeuterated methanol is thought to form during the prestellar core stage of star formation. Observed variations in the CH2DOH/
CH3OD ratio suggest that its formation is strongly dependent on the surrounding cloud conditions. Thus, it is a potential tracerof the physical conditions before the onset of star formation. A single-point physical model representative of a typical prestellar
core is coupled to chemical models to investigate potential formation pathways towards deuterated methanol at the prestellar
stage. Simple addition reactions of H and D are not able to reproduce observed abundances. The implementation of anexperimentally verified abstraction scheme leads to the efficient formation of methyl-deuterated methanol, but lacks sufficient
formation of hydroxy-deuterated methanol. CH3OD is most likely formed at a later evolutionarymstage, potentially from H-D
exchange reactions in warm ices between HDO (and D2O) and CH3OH. The CH2DOH/CH3OD ratio is not an appropriate
tracer of the physical conditions during the prestellar stage, but might be better suited as a tracer of ice heating.

A census of young stellar objects in two line-of-sight star forming regions toward IRAS

22. 22147+5948 in the outer Galaxy

Agata Karska, Maciej Koprowski, Aleksandra Solarz, Ryszard Szczerba, Marta Sewiło, Natasza Siódmiak,Davide Elia, Marcin Gawroński, Konrad Grzesiak, Bosco H. K. Yung, William J. Fischer, Lars E. Kristensen
F (abridged) Star formation in the outer Galaxy, i.e., outside of the Solar circle, has been lightly studied in part due to low
CO brightness of molecular clouds linked with the negative metallicity gradient. Recent infrared surveys provide an overview
of dust emission in large sections of the Galaxy, but suffer from cloud confusion and poor spatial resolution at far-infrared
wavelengths. We aim to develop a methodology to identify and classify young stellar objects (YSOs) in star-forming regions in
the outer Galaxy, and use it to solve a long-standing confusion with the distance and evolutionary status of IRAS 22147+5948.
We use Support Vector Machine learning algorithm to complement standard color-color and color-magnitude diagrams in search
for YSOs in the IRAS 22147 region using publicly available data from the ‘Spitzer Mapping of the Outer Galaxy’ survey. The
agglomerative hierarchical clustering algorithm is used to identify clusters, along with the Robitaille et al. (2017) code to
calculate physical properties of individual YSOs. We identify 13 Class I and 13 Class II YSO candidates using the color-color
diagrams, and additional 2 and 21 sources, respectively, using the machine learning techniques. Spectral energy distributions of
23 sources are modelled with a star and a passive disk, corresponding to Class II objects. Models of 3 sources include envelopes
typical for Class I objects. The objects are grouped in 2 clusters located at the distance of 2.2 kpc, and 5 clusters at 5.6
kpc. The spatial extent of CO, radio continuum, and dust emission confirms the origin of YSOs in two distinct star-forming
regions along a similar line-of-sight. The outer Galaxy might serve as a unique laboratory of star formation across environmentson condition that complementary methods and ancillary data are used to properly account for cloud confusion and distanceuncertainties.

23. Modelling Star Cluster Formation: Mergers

Jeremy Karam, Alison Sills F Star cluster formation in giant molecular clouds involves the local collapse of the cloud into
small gas-rich subclusters, which can then subsequently collide and merge to build up the final star cluster(s). In this paper, we
simulate collisions between these subclusters, using coupled smooth particle hydrodynamics for the gas and N-body dynamics
for the stars. We are guided by previous radiation hydrodynamics simulations of molecular cloud collapse which provide theglobal properties of the colliding clusters, such as their stellar and gas masses, and their initial positions and velocities. The
subclusters in the original simulation were treated as sink particles which immediately merged into a single entity after thecollision. We show that the more detailed treatment provides a more complex picture. At collisional velocities above 10 km/s,

8the stellar components of the cluster do not form a monolithic cluster within 3 Myr, although the gas may do so. At lower
velocities, the clusters do eventually merge but over timescales that may be longer than the time for a subsequent collision. The
structure of the resultant cluster is not well-fit by any standard density distribution, and the clusters are not in equilibrium
but continue to expand over our simulation time. We conclude that the simple sink particle treatment of subcluster mergers inlarge-scale giant molecular cloud simulations provides an upper limit on the final cluster properties.

interactions of supernova remnants with atomic and molecular clouds – the
24. Shocking
interplay between shocks, thermal instability and gravity in the large cloud regime
M. M. Kupilas, J. M. Pittard, C. J. Wareing, S. A. E. G. Falle F Using the adaptive mesh refinement code MG, weperform 3D hydrodynamic simulations of a supernova-cloud interaction in the "large cloud regime". The cloud is initially atomic
and evolving due to the thermal instability (TI) and gravity. We study interactions in a "pre-TI" and "post-TI" stage when coldand dense clumps are present, and compare these results to idealised shock-cloud scenarios in the "small cloud regime", and a
scenario without shocks. On aggregate, the supernova disruption is significantly weaker than that from an idealised shock due
to the supernova impact being instantaneous, and not continuous. In both supernova-cloud interactions, we observe two shocks
impact the cloud, followed by the development of a weak 10 km s−1 upstream flow on the cloud interface, and a global ambientpressure drop. When the cloud is still atomic, it expands due to this drop. Additionally, the TI is triggered at the front of thecloud, causing the formation of a cap-like structure with clumps embedded inside. The upstream flow converges in this region,
resulting in a lobe-like cloud morphology. When the cloud is molecular, the transmitted shock disrupts the inter-clump materialand causes the clumps’ outer envelopes to expand slightly and form tail-like morphologies. These effects are less pronounced
than those in our shock-cloud scenarios, and more pronounced that those in our un-shocked scenario. After 3.5 Myrs, the effects
from the supernova decay and the cloud returns to an almost indistinguishable state from an un-shocked cloud, in spite of the
global ambient pressure drop. In neither supernova-cloud scenario do we see any local gravitational collapse.

25. The Morphology of the HD 163296 jet as a window on its planetary system

A. Kirwan, A. Murphy, P. C Schneider, E. T. Whelan, C. Dougados, J. Eislöffel F HD163296 is a Herbig Ae star
which drives a bipolar knotty jet with a total length of 6000au. Strong evidence exists that the disk of HD163296 harbors
planets. Studies have shown that the presence of companions around jet-driving stars could affect the morphology of the jets.
This includes a ‘wiggling’ of the jet axis and a periodicity in the positions of the jet knots. In this study we investigate themorphology (including the jet width and axis position) and proper motions of the HD163296 jets, and use our results to better
understand the whole system.This study is based on optical integral-field spectroscopy observations obtained with VLT/MUSE
in 2017. Using spectro-images and position velocity diagrams extracted from the MUSE data cube, we investigated the number
and positions of the jet knots. A comparison was made to X-Shooter data collected in 2012 and the knot proper motions were
estimated. The jet width and jet axis position with distance from the star were studied from the extracted spectro-images.
We observe the merging of knots and identify two previously undetected knots. Measurements of the jet axis position reveal asimilar pattern of deviation in all forbidden emission lines along the first 20 arc seconds of the jets. This result is interpreted
as being due to asymmetric shocks and not due to a wiggling of the jet axis. The number of new knots detected and theirpositions challenge the 16-year knot ejection periodicity proposed in prior studies, arguing for a more complicated jet systemthan was previously assumed. We use the non-detection of a jet axis wiggling to rule out companions with a mass >0.1 M andorbits between 1 au and 35 au. Any object inferred at these distances using other methods must be a brown dwarf or planet,otherwise it would have impacted the jet axis position. Both the precession and orbital motion scenarios are considered.

Gas Formation via Collision-induced Magnetic Reconnection in a Disk Galaxy
26. Densewith a BiSymmetric Spiral Magnetic Field
Shuo Kong F Recently, a collision-induced magnetic reconnection (CMR) mechanism was proposed to explain a dense filament
formation in the Orion A giant molecular cloud. A natural question is that whether CMR works elsewhere in the Galaxy. As
an initial attempt to answer the question, this paper investigates the triggering of CMR and the production of dense gas in aflat-rotating disk with a modified BiSymmetric Spiral (BSS) magnetic field. Cloud-cloud collisions at field reversals in the disk
are modeled with the Athena++ code. Under the condition that is representative of the warm neutral medium, the cloud-cloud
collision successfully triggers CMR at different disk radii. However, dense gas formation is hindered by the dominating thermalpressure, unless a moderately stronger initial field & 5µG is present. The strong-field model, having a larger Lundquist number
SL and lower plasma β, activates the plasmoid instability in the collision midplane, which is otherwise suppressed by the disk
rotation. We speculate that CMR can be common if more clouds collide along field reversals. However, to witness the CMR
process in numerical simulations, we need to significantly resolve the collision midplane with a spatial dynamic range & 106 . If
Milky Way spiral arms indeed coincide with field reversals in BSS, it is possible that CMR creates or maintains dense gas in
the arms. High-resolution, high-sensitivity Zeeman/Faraday-Rotation observations are crucial for finding CMR candidates thathave helical fields.

927. Multi-scale decomposition of astronomical maps – a constrained diffusion method

Guang-Xing Li F We propose a new, efficient multi-scale method to decompose a map (or signal in general) into components
maps that contain structures of different sizes. In the widely-used wave transform, artifacts containing negative values arisearound regions with sharp transitions due to the application of band-limited filters. In our approach, the decomposition isachieved by solving a modified, non-linear version of the diffusion equation. This is inspired by the anisotropic diffusion
methods, which establish the link between image filtering and partial differential equations. In our case, the artifact issue isaddressed where the positivity of the decomposed images is guaranteed. Our new method is particularly suitable for signals
which contain localized, non-linear features, as typical of astronomical observations. It can be used to study the multi-scale
structures of astronomical maps quantitatively and should be useful in observation-related tasks such as background removal.
We thus propose a new measure called the "scale spectrum", which describes how the image values distribute among different
components in the scale space, to describe maps. The method allows for input arrays of an arbitrary number of dimensions, anda python3 implementation of the algorithms is included in the Appendix and available at https://gxli.github.io/ConstrainedDiffusion-Decomposition/.

28. Gas temperature structure across transition disk cavities

M. Leemker, A. S. Booth, E. F. van Dishoeck, A. F. Pérez-Sánchez, J. Szulágyi, A. D. Bosman, S. Bruderer,
S. Facchini, M. R. Hogerheijde, T. Paneque-Carreño, J. A. Sturm F [Abridged] Most disks observed at high angularresolution show substructures. Knowledge about the gas surface density and temperature is essential to understand these. The
aim of this work is to constrain the gas temperature and surface density in two transition disks: LkCa15 and HD 169142. We
use new ALMA observations of the 13 CO J = 6 − 5 transition together with archival J = 2 − 1 data of 12 CO, 13 CO and C18 O
to observationally constrain the gas temperature and surface density. Furthermore, we use the thermochemical code DALI tomodel the temperature and density structure of a typical transition disk. The 6 − 5/2 − 1 line ratio in LkCa15 constrains the gas
temperature in the emitting layers inside the dust cavity to be up to 65 K, warmer than in the outer disk at 20-30 K. For the
HD 169142, the peak brightness temperature constrains the gas in the dust cavity of HD 169142 to be 170 K, whereas that in
the outer disk is only 100 K. Models also show that a more luminous central star, a lower abundance of PAHs and the absenceof a dusty inner disk increase the temperature of the emitting layers and hence the line ratio in the gas cavity. The gas column
density in the LkCa15 dust cavity drops by a factor >2 compared to the outer disk, with an additional drop of an order ofmagnitude inside the gas cavity at 10 AU. In the case of HD 169142, the gas column density drops by a factor of 200−500 inside
the gas cavity, which could be due to a massive companion of several MJ . The broad dust-depleted gas region from 10-68 AU
for LkCa15 may imply several lower mass planets. This work demonstrates that knowledge of the gas temperature is important
to determine the gas surface density and thus whether planets, and if so what kind of planets, are the most likely carving thedust cavities.

CO Line Emission Surfaces and Vertical Structure in Mid-Inclination Protoplanetary

29. DisksCharles J. Law, Sage Crystian, Richard Teague, Karin I. Öberg, Evan A. Rich, Sean M. Andrews, Jaehan Bae,
Kevin Flaherty, Viviana V. Guzmán, Jane Huang, John D. Ilee, Joel H. Kastner, Ryan A. Loomis, Feng Long,
Laura M. Pérez, Sebastián Pérez, Chunhua Qi, Giovanni P. Rosotti, Dary Ruíz-Rodríguez, Takashi Tsukagoshi,
David J. Wilner F High spatial resolution CO observations of mid-inclination (30-75 degrees) protoplanetary disks offer an
opportunity to study the vertical distribution of CO emission and temperature. The asymmetry of line emission relative to thedisk major axis allows for a direct mapping of the emission height above the midplane, and for optically-thick, spatially-resolved
emission in LTE, the intensity is a measure of the local gas temperature. Our analysis of ALMA archival data yields COemission surfaces, dynamically-constrained stellar host masses, and disk atmosphere gas temperatures for the disks around:HD 142666, MY Lup, V4046 Sgr, HD 100546, GW Lup, WaOph 6, DoAr 25, Sz 91, CI Tau, and DM Tau. These sources
span a wide range in stellar masses (0.50-2.10 M ), ages (∼‘0 0.3-23 Myr), and CO gas radial emission extents (≈200-1000 au).
This sample nearly triples the number of disks with mapped emission surfaces and confirms the wide diversity in line emittingheights (z/r ≈ 0.1 to &0.5) hinted at in previous studies. We compute radial and vertical CO gas temperature distributions foreach disk. A few disks show local temperature dips or enhancements, some of which correspond to dust substructures or the
proposed locations of embedded planets. Several emission surfaces also show vertical substructures, which all align with ringsand gaps in the millimeter dust. Combining our sample with literature sources, we find that CO line emitting heights weakly
decline with stellar mass and gas temperature, which, despite large scatter, is consistent with simple scaling relations. We also
observe a correlation between CO emission height and disk size, which is due to the flared structure of disks. Overall, COemission surfaces trace ≈2-5× gas pressure scale heights (Hg ) and could potentially be calibrated as empirical tracers of Hg .

10

Density Exponent Analysis: Gravity-driven steepening of the density profiles of star-

30. forming regions

Guang-Xing Li, Ji-Xuan Zhou F The evolution of molecular interstellar clouds is a complex, multi-scale process. The powerlaw density exponent describes the steepness of density profiles, and it has been used to characterize the density structures of
the clouds yet its usage is usually limited to spherically symmetric systems. Importing the Level-Set Method, we develop a newformalism that generates robust maps of a generalized density exponent kρ at every location for complex density distributions.
By applying it to high fidelity, high dynamical range map of the Perseus molecular cloud constructed using data from the Herscheland Planck satellites, we find that the density exponent exhibits a surprisingly wide range of variation (−3.5 . kρ . −0.5).
Regions at later stages of gravitational collapse are associated with steeper density profiles. Inside a region, gas located in
the vicinities of dense structures has very steep density profiles with kρ ≈ −3, which forms because of depletion. This density
exponent analysis reveals diverse density structures, forming a coherent picture that gravitational collapse leads to a continued
steepening of the density profile. We expect our method to be effective in studying other power-law-like density structures,
including granular materials and the Large-Scale Structure of the Universe.

31. Discovery of a coherent, wave-like velocity pattern for the Radcliffe Wave

Guang-Xing Li, Bing-Qiu Chen F Recently studies discovered that part of the Gould Belt belongs to a 2.7 kpc-longcoherent, thin wave consisting of a chain of clouds, where a damped undulation pattern has been identified from the spatial
arrangement of the clouds. We use the proper motions of Young Stellar Objects (YSOs) anchored inside the clouds to study
the kinematic structure of the Radcliffe Wave in terms of vz , and identify a damped, wave-like pattern from the vz space, which
we call "velocity undulation". We propose a new formalism based on the Ensemble Empirical Mode Decomposition (EEMD)
to determine the amplitude, period, and phase of the undulation pattern, and find that the spatial and the velocity undulation
share an almost identical spatial frequency of about 1.5 kpc, and both are damped when measured from one side to the other.
Measured for the first cycle, they exhibit a phase difference of around 2π/3. The structure is oscillating around the midplaneof the Milky Way disk with an amplitude of ∼ 130 ± 20 pc. The vertical extent of the Radcliffe Wave exceeds the thicknessof the molecular disk, suggesting that the undulation of the undulation signature might originate from a perturbation, e.g. thepassage of a dwarf galaxy.

investigation of selected cloud compositions in exoplanetary atmospheres
32. Polarimetric
Moritz Lietzow, Sebastian Wolf F We investigated the impact of selected cloud condensates in exoplanetary atmosphereson the polarization of scattered stellar radiation. We considered a selection of 25 cloud condensates that are expected to bepresent in extrasolar planetary atmospheres. Using the three-dimensional Monte Carlo radiative transfer code POLARIS andassuming Mie scattering theory, we calculated and studied the net polarization of scattered radiation as a function of planetaryphase angle at optical to near-infrared wavelengths. In addition to the well-known characteristics in the state of polarization,such as the rainbow determined by the real part of the refractive index, the behavior of the underlying imaginary part of
the refractive index causes an increase or decrease in the degree of polarization and a change of sign in the polarization at acharacteristic wavelength. In contrast to Al2 O3 and MgFeSiO4 , clouds composed of SiO, MnS, Na2 S, or ZnS produce a rapidly
decreasing degree of polarization with increasing wavelength in the context of an exoplanetary atmosphere. Furthermore, thesign of the polarization changes at a wavelength of about 0.5 µm to 0.6 µm, depending on the specific cloud condensate. The
resulting net polarization is mainly positive for cloud compositions with large imaginary parts of the refractive index, such as
Fe, FeS, and FeO. In addition, for Fe and FeS clouds, the maximum degree of polarization at long wavelengths is shifted tolarger phase angles than for FeO. We found that most of these cloud condensates are distinguishable from each other due totheir unique wavelength-dependent complex refractive index. In particular, an increase or decrease of the net polarization as afunction of wavelength and a change of sign in the polarization at specific wavelengths are important features for characterizing
cloud compositions in exoplanetary atmospheres.

observation towards the young massive star cluster NGC 6618 in the M17
33. Gamma-ray
regionBing Liu, Rui-zhi Yang, Zhiwei Chen F Young massive clusters have been established as a new population of gamma-ray
sources and potential cosmic ray (CR) accelerators. In this paper, we report the detection of gamma-ray emissions near the
young star cluster NGC 6618, which is one of the youngest star clusters in our Galaxy. The detected gamma-ray emissions canbe divided into two components. One component is point-like and reveals harder spectrum, while the other is extended andwith softer spectrum. Such spectral features are significantly different from other young massive clusters and may be due tothe propagation effects of CRs accelerated in NGC 6618.

1134. Trends in Silicates in the β Pictoris Disk
Cicero X. Lu, Christine H. Chen, B. A. Sargent, Dan M. Watson, Carey M. Lisse, Joel D. Green, Michael
L. Sitko, Tushar Mittal, V. Lebouteiller, G. C. Sloan, Isabel Rebollido, Dean C. Hines, Julien H. Girard,
Michael W. Werner, Karl R. Stapelfeldt, Winston Wu, Kadin Worthen F While beta Pic is known to host silicatesin ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question.
We re-analyze the beta Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new IRTF/SpeX
spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy forstellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18 micron forsterite emission
feature and recover a 23 micron forsterite emission feature with a substantially larger line-to-continuum ratio than previously
reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which
are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies’
composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains
become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, theFe/Mg ratio decreases. Applying these trends to beta Pic’s planetary architecture, we find that the dust population exterior tothe orbits of beta Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3-5 micron dust excess due
to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals
are more Fe-rich and collisionally-processed closer to the star but more Fe-poor and primordial farther from the star.

observations of CH3 OH, c-C3 H2 and HNCO towards L1544: Dissecting the
35. Multi-line
core structure with chemical differentiation
Yuxin Lin, Silvia Spezzano, Olli Sipilä, Anton Vasyunin, Paola Caselli F Pre-stellar cores are the basic unit for theformation of stars and stellar systems. The anatomy of the physical and chemical structures of pre-stellar cores is critical forunderstanding the star formation process. L1544 is a prototypical pre-stellar core, which shows significant chemical differentiation surrounding the dust peak. We aim to constrain the physical conditions at the different molecular emission peaks. This
study allows us to compare the abundance profiles predicted from chemical models together with the classical density structureof Bonnor-Ebert (BE) sphere. We conducted multi-transition pointed observations of CH3 OH, c-C3 H2 and HNCO with the
IRAM 30m telescope, towards the dust peak and the respective molecular peaks of L1544. With non-LTE radiative transfer
calculations and a 1-dimensional model, we revisit the physical structure of L1544, and benchmark with the abundance profiles
from current chemical models. We find that the HNCO, c-C3 H2 and CH3 OH lines in L1544 are tracing progressively higher
density gas, from ∼104 to several times 105 cm−3 . Particularly, we find that to produce the observed intensities and ratios of
the CH3 OH lines, a local gas density enhancement upon the BE sphere is required. This suggests that the physical structure ofan early-stage core may not necessarily follow a smooth decrease of gas density profile locally, but can be intercepted by clumpy
substructures surrounding the gravitational center. Multiple transitions of molecular lines from different molecular species canprovide a tomographic view of the density structure of pre-stellar cores. The local gas density enhancement deviating fromthe BE sphere may reflect the impact of accretion flows that appear asymmetric and are enhanced at the meeting point oflarge-scale cloud structures.

disk of FU Orionis viewed with MATISSE/VLTI: first interferometric observations
36. Thein L and M bands
F. Lykou, P. Ábrahám, L. Chen, J. Varga, Á. Kóspál, A. Matter, M. Siwak, Zs. M. Szabó, Z. Zhu, H. B. Liu,
B. Lopez, F. Allouche, J. -C. Augereau, P. Berio, P. Cruzalèbes, C. Dominik, Th. Henning, K. -H. Hofmann,
M. Hogerheijde, W. J. Jaffe, E. Kokoulina, S. Lagarde, A. Meilland, F. Millour, E. Pantin, R. Petrov, S.
Robbe-Dubois, D. Schertl, M. Scheuck, R. van Boekel, L. B. F. M. Waters, G. Weigelt, S. Wolf F The diskof FU Orionis is marginally resolved with MATISSE, suggesting that the region emitting in the thermal infrared is rather
compact. An upper limit of ∼ 1.3 ± 0.1 mas (in L) can be given for the diameter of the disk region probed in the L band,corresponding to 0.5 au at the adopted Gaia EDR3 distance. This represents the hot, gaseous region of the accretion disk.
The N -band data indicate that the dusty passive disk is silicate-rich. Only the innermost region of said dusty disk is found toemit strongly in the N band, and it is resolved at an angular size of ∼ 5 mas, which translates to a diameter of about 2 au.
The observations therefore place stringent constraints for the outer radius of the inner accretion disk. Dust radiative transfer
simulations with RADMC-3D provide adequate fits to the spectral energy distribution from the optical to the submillimeter andto the interferometric observables when opting for an accretion rate Ṁ ∼ 2 × 10−5 M yr−1 and assuming M∗ = 0.6 M . Most
importantly, the hot inner accretion disk’s outer radius can be fixed at 0.3 au. The outer radius of the dusty disk is placed at
100 au, based on constraints from scattered-light images in the literature. The dust mass contained in the disk is 2.4 × 10−4 M ,and for a typical gas-to-dust ratio of 100, the total mass in the disk is approximately 0.02 M . We did not find any evidence
for a nearby companion in the current interferometric data, and we tentatively explored the case of disk misalignment. For thelatter, our modeling results suggest that the disk orientation is similar to that found in previous imaging studies by ALMA.
Should there be an asymmetry in the very compact, inner accretion disk, this might be resolved at even smaller spatial scales12(≤ 1 mas).

Herbig-Haro objects in the Orion Nebula through deep high-spectral res37. Photoionizedolution spectroscopy III: HH514
J. E. Méndez-Delgado, C. Esteban, J. García-Rojas, W. J. Henney, . F We analyze the physical conditions andchemical composition of the photoionized Herbig-Haro object HH 514, which emerges from the proplyd 170-337 in the coreof the Orion Nebula. We use high-spectral resolution spectroscopy from UVES at the Very Large Telescope and IFU-spectrafrom MEGARA at the Gran Telescopio de Canarias. We observe two components of HH 514, the jet base and a knot, with
ne = (2.3 ± 0.1) × 105 cm−3 and ne = (7 ± 1) × 104 cm−3 , respectively, both with Te ≈ 9000 K. We show that the chemicalcomposition of HH 514 is consistent with that of the Orion Nebula, except for Fe, Ni and S, which show higher abundances.
The enhanced abundances of Fe and Ni observed in HH objects compared with the general interstellar medium is usuallyinterpreted as destruction of dust grains. The observed sulphur overabundance (more than two times solar) is challenging to
explain since the proplyd photoevaporation flow from the same disk shows normal sulphur abundance. If the aforementioned
S-overabundance is due to dust destruction, the formation of sulfides and/or other S-bearing dust reservoirs may be linked toplanet formation processes in protoplanetary disks, which filter large sulfide dust grains during the accretion of matter fromthe disk to the central star. We also show that published kinematics of molecular emission close to the central star are notconsistent with either a disk perpendicular to the optical jet, nor with an outflow that is aligned with it.

38. NIR spectroscopic survey of protostellar jets in the star forming region IC 1396N

Fabrizio Massi, Rosario López, Maria T. Beltrán, Robert Estalella, Josep M. Girart F Abridged. The bright-rimmed
cloud IC1396N hosts CO, H2 , and Herbig-Haro outflows powered by millimetre compact sources. We aim to characterise thekinematics and physical conditions of the H2 emission features spread over IC1396N, which appear as chains of knots with ajet-like morphology, tracing different H2 outflows, and to obtain further information about (and an identification of) the driving
sources. Low-resolution, long-slit near-infrared spectra were acquired with NICS at the TNG, using grisms KB (R 1200),
HK and JH (R 500). Several slit pointings and PA were used throughout IC1396N to sample a number of the H2 knots
previously detected in deep H2 2.12 µm images. The knots exhibit rich ro-vibrational spectra of H2 , consistent with shockexcited excitation, from which radial velocities and relevant physical conditions of the IC1396N H2 outflows were derived. Thesealso allowed estimating extinction ranges towards several features. [FeII] emission was only detected towards a few knots, which
also display unusually large H2 1-0 S(3)/S(1) flux ratios. The obtained radial velocities confirm that most of the outflows areclose to the plane of the sky. Nearby knots in the same chain often display different radial velocities, both blue-shifted andred-shifted, which we interpret as due to ubiquitous jet precession in the driving sources or the development of oblique shocks.
One of the chains (strand A) appears as a set of features trailing a leading bow-shock structure consistent with the results of
3-D magneto-hydrodynamical models. Either side of the leading bow-shock (A15) exhibits a different radial velocity, whose
possible explanations are discussed in the paper. Our data cannot confirm whether strands A and B have both been originatedby the intermediate mass young stellar object BIMA 2.

39. The SEDIGISM survey: Molecular cloud morphology. II. Integrated source properties

K. R. Neralwar, D. Colombo, A. Duarte-Cabral, J. S. Urquhart, M. Mattern, F. Wyrowski, K. M. Menten, P.
Barnes, A. Sanchez-Monge, A. J. Rigby, P. Mazumdar, D. Eden, T. Csengeri, C. L. Dobbs, V. S. Veena, S.
Neupane, T. Henning, F. Schuller, S. Leurini, M. Wienen, A. Y. Yang, S. E. Ragan, S. Medina, Q. NguyenLuong F The Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium (SEDIGISM) survey has produced
high (spatial and spectral) resolution 13 CO (2-1) maps of the Milky Way. It has allowed us to investigate the molecular interstellar
medium in the inner Galaxy at an unprecedented level of detail and characterise it into molecular clouds. In a previous paper,
we have classified the SEDIGISM clouds into four morphologies. However, how the properties of the clouds vary for these fourmorphologies is not well understood. Here, we use the morphological classification of SEDIGISM clouds to find connections
between the cloud morphologies, their integrated properties, and their location on scaling relation diagrams. We observe thatring-like clouds show the most peculiar properties, having, on average, higher masses, sizes, aspect ratios and velocity dispersions
compared to other morphologies. We speculate that this is related to the physical mechanisms that regulate their formation andevolution, for example, turbulence from stellar feedback can often results in the creation of bubble-like structures. We also see atrend of morphology with virial parameter whereby ring-like, elongated, clumpy and concentrated clouds have virial parameters
in a decreasing order. Our findings provide a foundation for a better understanding of the molecular cloud behaviour based on
their measurable properties.

1340. An Interferometric View of H-MM1. I. Direct Observation of NH3 Depletion
Jaime E. Pineda, Jorma Harju, Paola Caselli, Olli Sipilä, Mika Juvela, Charlotte Vastel, Erik Rosolowsky,
Andreas Burkert, Rachel K. Friesen, Yancy Shirley, María José Maureira, Spandan Choudhury, Dominique
M. Segura-Cox, Rolf Güsten, Anna Punanova, Luca Bizzocchi, Alyssa A. Goodman F Spectral lines of ammonia,
NH3 , are useful probes of the physical conditions in dense molecular cloud cores. In addition to advantages in spectroscopy,
ammonia has also been suggested to be resistant to freezing onto grain surfaces, which should make it a superior tool forstudying the interior parts of cold, dense cores. Here we present high-resolution NH3 observations with the Very Large Array(VLA) and Green Bank Telescope (GBT) towards a prestellar core. These observations show an outer region with a fractional
NH3 abundance of X(NH3 ) = (1.975±0.005)×10−8 (±10% systematic), but it also reveals that after all, the X(NH3 ) starts todecrease above a H2 column density of ≈ 2.6×1022 cm−2 . We derive a density model for the core and find that the break-point in
the fractional abundance occurs at the density n(H2 ) ∼ 2 × 105 cm−3 , and beyond this point the fractional abundance decreases
with increasing density, following the power law n−1.1 . This power-law behavior is well reproduced by chemical models where
adsorption onto grains dominates the removal of ammonia and related species from the gas at high densities. We suggest thatthe break-point density changes from core to core depending on the temperature and the grain properties, but that the depletion
power law is anyway likely to be close to n−1 owing to the dominance of accretion in the central parts of starless cores.

From Bubbles and Filaments to Cores and Disks: Gas Gathering and Growth of Struc-

41. ture Leading to the Formation of Stellar Systems

Jaime E. Pineda, Doris Arzoumanian, Philippe André, Rachel K. Friesen, Annie Zavagno, Seamus D. Clarke,
Tsuyoshi Inoue, Che-Yu Chen, Yueh-Ning Lee, Juan D. Soler, Michael Kuffmeier F The study of the developmentof structures on multiple scales in the cold interstellar medium has experienced rapid expansion in the past decade, on boththe observational and the theoretical front. Spectral line studies at (sub-)millimeter wavelengths over a wide range of physicalscales have provided unique probes of the kinematics of dense gas in star-forming regions, and have been complemented byextensive, high dynamic range dust continuum surveys of the column density structure of molecular cloud complexes, while
dust polarization maps have highlighted the role of magnetic fields. This has been accompanied by increasingly sophisticatednumerical simulations including new physics (e.g., supernova driving, cosmic rays, non-ideal magneto-hydrodynamics, radiationpressure) and new techniques such as zoom-in simulations allowing multi-scale studies. Taken together, these new data have emphasized the anisotropic growth of dense structures on all scales, from giant ISM bubbles driven by stellar feedback on ∼50–100
pc scales through parsec-scale molecular filaments down to < 0.1 pc dense cores and < 1000 au protostellar disks. Combining
observations and theory, we present a coherent picture for the formation and evolution of these structures and synthesize acomprehensive physical scenario for the initial conditions and early stages of star and disk formation.

42. Magnetic fields and outflows in the large Bok globule CB 54
Kate Pattle, Shih-Ping Lai, Sarah Sadavoy, Simon Coudé, Sebastian Wolf, Ray Furuya, Woojin Kwon, Chang
Won Lee, Niko Zielinski F We have observed the large Bok globule CB 54 in 850µm polarised light using the POL-2
polarimeter on the James Clerk Maxwell Telescope (JCMT). We find that the magnetic field in the periphery of the globule
shows significant, ordered deviation from the mean field direction in the globule centre. This deviation appears to correspondwith the extended but relatively weak 12 CO outflow emanating from the Class 0 sources at the centre of the globule. Energetics
analysis suggests that if the outflow is reshaping the magnetic field in the globule’s periphery, then we can place an upper
limit of < 27 µG on the magnetic field strength in the globule’s periphery. Comparison with archival Planck and CARMA
measurements shows that the field in the centre of the globule is consistent over several orders of magnitude in size scale, andoriented parallel to the density structure in the region in projection. We thus hypothesise that while non-thermal motions in theregion may be sub-Alfvénic, the magnetic field is subdominant to gravity over a wide range of size scales. Our results suggestthat even a relatively weak outflow may be able to significantly reshape magnetic fields in star-forming regions on scales > 0.1
pc.

The KOSMA-τ PDR Model – I. Recent updates to the numerical model of photo-

43. dissociated regions

M. Röllig, V. Ossenkopf-Okada F Numerical models of Photodissociation Regions (PDRs) are an essential tool to quantitatively understand observations of massive star forming regions through simulations. Few mature PDR models are available
and the Cologne KOSMA-τ PDR model is the only sophisticated model that uses a spherical cloud geometry thereby allowing
us to simulate clumpy PDRs. We present the current status of the code as reference for modelers and for observers thatplan to apply KOSMA-τ to interpret their data. For the numerical solution of the chemical problem we present a superior
Newton-Raphson stepping algorithm and discuss strategies to numerically stabilize the problem and speed up the iterations.
The chemistry in KOSMA-τ is upgraded to include the full surface chemistry in an up-to-date formulation and we discuss anovel computation of branching ratios in chemical desorption reactions. The high dust temperature in PDRs leads to a selective
freeze-out of oxygen-bearing ice species due to their higher condensation temperatures and we study changes in the ice mantle

14

structures depending on the PDR parameters, in particular the impinging UV field. Selective freeze-out can produce enhanced
C abundances and higher gas temperatures resulting in a fine-structure line emission of atomic carbon [C] enhanced by up to
50how recent ALMA observations of HCO+ emission in the Orion Bar with high spatial resolution on the scale of individual
clumps can be interpreted in the context of non-stationary, clumpy PDR ensembles. Additionally, we introduce WL-PDR, asimple plane-parallel PDR model written in Mathematica to act as numerical testing environment of PDR modeling aspects.

44. Resolving the collimation zone of an intermediate-mass protostar

Adriana R. Rodríguez-Kamenetzky, Carlos Carrasco-González, Luis Felipe Rodríguez Jorge, Tom P. Ray, Alberto Sanna, Luca Moscadelli, Melvin Hoare, Roberto Galván-Madrid, Hsien Shang, Susana Lizano, Jochen
Eislöffel, Jeremy Lim, José M. Torrelles, Paul Ho, Anton Feeney-Johansson F We report new VLA and e-MERLIN
high resolution and sensitivity images of the Triple Radio continuum Source in the Serpens star forming region. These observations allowed us to perform a deep multi-frequency, multi-epoch study by exploring the innermost regions (< 100 au) of
an intermediate-mass YSO for the first time, with a physical resolution of 15 au. The kinematic analysis of knots recently
ejected by the protostar indicates that the jet is undergoing episodic variations in velocity. In addition, our multi-frequency
images reveal striking characteristics, e.g., a highly collimated ionized stream that would be launched at a radial distance of
0.4 au from the protostar, and a narrow ( 28 au wide) ionized cavity that would be excited by the interaction of a wide-angle
component with the surrounding toroid of infalling material. In light of these results, we propose the scenario in which botha highly-collimated jet and a wide-angle wind coexist to be the most plausible to explain our observations, either launched by
the X-wind or X- plus Disk-wind mechanism.

ejection and time variability in protostellar outflows: Cep E. SOLIS XVI
45. Mass
A. de A. Schutzer, P. R. Rivera-Ortiz, B. Lefloch, A. Gusdorf, C. Favre, D. Segura-Cox, A. Lopez-Sepulcre,
R. Neri, J. Ospina-Zamudio, M. De Simone, C. Codella, S. Viti, L. Podio, J. Pineda, R. O’Donoghue, C.
Ceccarelli, P. Caselli, F. Alves, R. Bachiller, N. Balucani, E. Bianchi, L. Bizzocchi, S. Bottinelli, E. Caux, A.
Chacón-Tanarro, F. Dulieu, J. Enrique-Romero, F. Fontani, S. Feng, J. Holdship, I. Jiménez-Serra, A. Jaber
Al-Edhari, C. Kahane, V. Lattanzi, Y. Oya, A. Punanova, A. Rimola, N. Sakai, S. Spezzano, I. R. Sims, V.
Taquet, L. Testi, P. Theulé, P. Ugliengo, C. Vastel, A. I. Vasyunin, F. Vazart, S. Yamamoto, A. Witzel F
Protostellar jets are an important agent of star formation feedback, tightly connected with the mass-accretion process. The
history of jet formation and mass-ejection provides constraints on the mass accretion history and the nature of the driving
source. We want to characterize the time-variability of the mass-ejection phenomena at work in the Class 0 protostellar phase,in order to better understand the dynamics of the outflowing gas and bring more constraints on the origin of the jet chemicalcomposition and the mass-accretion history. We have observed the emission of the CO 2-1 and SO NJ =5 4-4 3 rotationaltransitions with NOEMA, towards the intermediate-mass Class 0 protostellar system Cep E. The CO high-velocity jet emission
reveals a central component associated with high-velocity molecular knots, also detected in SO, surrounded by a collimatedlayer of entrained gas. The gas layer appears to accelerate along the main axis over a length scale delta0 ∼700 au, while its
diameter gradually increases up to several 1000au at 2000au from the protostar. The jet is fragmented into 18 knots of mass10−3 Msun, unevenly distributed between the northern and southern lobes, with velocity variations up to 15 km/s close to theprotostar, well below the jet terminal velocities. The knot interval distribution is approximately bimodal with a scale of ∼50-80
yr close to the protostar and ∼150-200 yr at larger distances >12". The mass-loss rates derived from knot masses are overall
steady, with values of 2.7x10−5 Msun/yr (8.9x10−6 Msun/yr) in the northern (southern) lobe. The interaction of the ambient
protostellar material with high-velocity knots drives the formation of a molecular layer around the jet, which accounts for thehigher mass-loss rate in the north. The jet dynamics are well accounted for by a simple precession model with a period of
2000yr and a mass-ejection period of 55yr.

46. The Radcliffe Wave as the gas spine of the Orion Arm
Cameren Swiggum, João Alves, Elena D’Onghia, Robert A. Benjamin, Lekshmi Thulasidharan, Catherine
Zucker, Eloisa Poggio, Ronald Drimmel, John S. Gallagher III, Alyssa Goodman F The Radcliffe Wave is a ∼ 3
kpc long coherent gas structure containing most of the star-forming complexes near the Sun. In this Letter we aim to finda Galactic context for the Radcliffe Wave by looking into a possible relationship between the gas structure and the Orion(Local) Arm. We use catalogs of massive stars and young open clusters based on Gaia EDR3 astrometry, in conjunction withkiloparsec-scale 3D dust maps, to investigate the Galactic XY spatial distributions of gas and young stars. We find a quasiparallel offset between the luminous blue stars and the Radcliffe Wave, in that massive stars and clusters are found essentiallyinside and downstream from the Radcliffe Wave. We examine this offset in the context of color gradients observed in the spiralarms of external galaxies, where the interplay between density wave theory, spiral shocks, and triggered star formation has
been used to interpret this particular arrangement of gas/dust and OB stars, and outline other potential explanations as well.
We hypothesize that the Radcliffe Wave constitutes the gas reservoir of the Orion (Local) Arm, and presents itself as a prime
laboratory to study the interface between Galactic structure, the formation of molecular clouds in the Milky Way, and star15

formation.

47. The importance of X-ray frequency in driving photoevaporative winds

Andrew D. Sellek, Cathie J. Clarke, Barbara Ercolano F Photoevaporative winds are a promising mechanism fordispersing protoplanetary discs, but so far theoretical models have been unable to agree on the relative roles that the Xray, Extreme Ultraviolet or Far Ultraviolet play in driving the winds. This has been attributed to a variety of methodologicaldifferences between studies, including their approach to radiative transfer and thermal balance, the choice of irradiating spectrum
employed, and the processes available to cool the gas. We use the mocassin radiative transfer code to simulate wind heating fora variety of spectra on a static density grid taken from simulations of an EUV-driven wind. We explore the impact of choosing
a single representative X-ray frequency on their ability to drive a wind by measuring the maximum heated column as a functionof photon energy. We demonstrate that for reasonable luminosities and spectra, the most effective energies are at a few 100 eV,
firmly in the softer regions of the X-ray spectrum, while X-rays with energies ∼ 1000 eV interact too weakly with disc gas toprovide sufficient heating to drive a wind. We develop a simple model to explain these findings. We argue that further increases
in the cooling above our models - for example due to molecular rovibrational lines - may further restrict the heating to thesofter energies but are unlikely to prevent X-ray heated winds from launching entirely; increasing the X-ray luminosity has the
opposite effect. The various results of photoevaporative wind models should therefore be understood in terms of the choice of
irradiating spectrum.

48. Calibrated Gas Accretion and Orbital Migration of Protoplanets in 1D Disc Models

Oliver Schib, Christoph Mordasini, Ravit Helled F We aim to develop a simple prescription for migration and accretionin 1D disc models, calibrated with results of 3D hydrodynamic simulations. Our focus lies on non-self-gravitating discs, but
we also discuss to what degree our prescription could be applied when the discs are self-gravitating. We study migration using
torque densities. Our model for the torque density is based on existing fitting formulas, which we subsequently modify to prevent
premature gap-opening. At higher planetary masses, we also apply torque densities from hydrodynamic simulations directly
to our 1D model. These torque densities allow modelling the orbital evolution of an initially low-mass planet that undergoes
runaway-accretion to become a massive planet. The two-way exchange of angular momentum between disc and planet isincluded. This leads to a self-consistent treatment of gap formation that only relies on directly accessible disc parameters. We
present a formula for Bondi- and Hill- gas accretion in the disc-limited regime. This formula is self-consistent in the sensethat mass is removed from the disc in the location from where it is accreted. We find that the resulting evolution in massand semi-major axis in the 1D framework is in good agreement with those from 3D hydrodynamical simulations for a rangeof parameters. Our prescription is valuable for simultaneously modelling migration and accretion in 1D-models. We conclude
that it is appropriate and beneficial to apply torque densities from hydrodynamic simulations in 1D models, at least in theparameter space we study here. More work is needed to in order to determine whether our approach is also applicable in aneven wider parameter space and in situations with more complex disc thermodynamics, or when the disc is self-gravitating.

49. The Detection of Deuterated Water in the Large Magellanic Cloud with ALMA

Marta Sewiło, Agata Karska, Lars E. Kristensen, Steven B. Charnley, C. -H. Rosie Chen, Joana M. Oliveira,Martin Cordiner, Jennifer Wiseman, Álvaro Sánchez-Monge, Jacco Th. van Loon, Remy Indebetouw, Peter
Schilke, Emmanuel Garcia-Berrios F We report the first detection of deuterated water (HDO) toward an extragalactic
hot core. The HDO 211 -212 line has been detected toward hot cores N105-2A and 2B in the N105 star-forming region in the
low-metallicity Large Magellanic Cloud (LMC) dwarf galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA).
We have compared the HDO line luminosity (LHDO ) measured toward the LMC hot cores to those observed toward a sample
of seventeen Galactic hot cores covering three orders of magnitude in LHDO , four orders of magnitude in bolometric luminosity(Lbol ), and a wide range of Galactocentric distances (thus metallicities). The observed values of LHDO for the LMC hot cores
fit very well into the LHDO trends with Lbol and metallicity observed toward the Galactic hot cores. We have found that
LHDO seems to be largely dependent on the source luminosity, but metallicity also plays a role. We provide a rough estimateof the H2 O column density and abundance ranges toward the LMC hot cores by assuming that HDO/H2 O toward the LMC
hot cores is the same as that observed in the Milky Way; the estimated ranges are systematically lower than Galactic values.
The spatial distribution and velocity structure of the HDO emission in N105-2A is consistent with HDO being the product of
the low-temperature dust grain chemistry. Our results are in agreement with the astrochemical model predictions that HDO isabundant regardless of the extragalactic environment and should be detectable with ALMA in external galaxies.

16

ALMA study of the massive molecular clump N159W-North in the Large Magellanic
50. AnCloud: A possible gas flow penetrating one of the most massive protocluster systems
in the Local Group
Kazuki Tokuda, Taisei Minami, Yasuo Fukui, Tsuyoshi Inoue, Takeru Nishioka, Kisetsu Tsuge, Sarolta Zahorecz,
Hidetoshi Sano, Ayu Konishi, C. -H. Rosie Chen, Marta Sewiło, Suzanne C. Madden, Omnarayani Nayak,
Kazuya Saigo, Atsushi Nishimura, Kei E. I. Tanaka, Tsuyoshi Sawada, Remy Indebetouw, Kengo Tachihara,
Akiko Kawamura, Toshikazu Onishi F Massive dense clumps in the Large Magellanic Cloud can be an important laboratory
to explore the formation of populous clusters. We report multiscale ALMA observations of the N159W-North clump, which is
the most CO-intense region in the galaxy. High-resolution CO isotope and 1.3 mm continuum observations with an angularresolution of ∼0."25(∼0.07 pc) revealed more than five protostellar sources with CO outflows within the main ridge clump. Oneof the thermal continuum sources, MMS-2, shows especially massive/dense nature whose total H2 mass and peak column density
are ∼104 M and ∼1024 cm−2 , respectively, and harbors massive (∼100 M ) starless core candidates identified as its internal
substructures. The main ridge containing this source can be categorized as one of the most massive protocluster systems in
the Local Group. The CO high-resolution observations found several distinct filamentary clouds extending southward from thestar-forming spots. The CO (1-0) data set with a larger field of view reveals a conical-shaped, ∼30 pc long complex extending
toward the northern direction. These features indicate that a large-scale gas compression event may have produced the massive
star-forming complex. Based on the striking similarity between the N159W-North complex and the previously reported othertwo high-mass star-forming clouds in the nearby regions, we propose a ”teardrops inflow model” that explains the synchronized,
extreme star formation across >50 pc, including one of the most massive protocluster clumps in the Local Group.

51. Dancing with the stars: Stirring up extraordinary turbulence in Galactic center clouds

Konstantinos Tassis, Vasiliki Pavlidou F Molecular clouds in the central molecular zone (CMZ) have been observed tofeature turbulent line widths that are significantly higher, and scale with cloud size more steeply, than in the rest of the MilkyWay. In the same Galactic region, the stellar density is also much higher than in the rest of the Milky Way, and the verticalstellar velocity dispersion is large, meaning that even young stars are likely to cross the entire vertical extent of the CMZ within
their lifetimes. Here, we investigate whether interactions of CMZ molecular clouds with crossing stars can account for the
extraordinary properties of observed turbulence in this part of the Galaxy. We calculated the rate of energy deposition by stars
crossing CMZ clouds due to (a) stellar winds and (b) dynamical friction, and compared it to the rate of turbulence decay. We
calculated the predicted scaling of turbulence line width with cloud size in each case. We find that energy deposition by stellar
winds of crossing massive stars can account for both the level and the scaling of CMZ cloud turbulence with cloud size. We
also find that the mechanism stops being effective at a Galactocentric distance comparable to the CMZ extent. On the other
hand, we find that dynamical friction by crossing stars does not constitute a significant driver of turbulence for CMZ clouds.

52. Three-dimensional extinction maps: Inverting inter-calibrated extinction catalogues

J. L. Vergely, R. Lallement, N. L. J. Cox F 3D maps of the extinction density in the Galaxy can be built through theinversion of catalogues of distance-extinction pairs for individual target stars. The spatial resolution of the maps that can beachieved increases with the spatial density of the targets, and subsequently with the combination of catalogues. However, thisrequires their careful inter-calibration. Our aim is to develop methods of inter-calibration of two different catalogues. We used as
reference a spectrophotometric catalogue. A principal component analysis was performed in G,GB,GR,J,H,K multi-colour space
for the second catalog. The subspace constituted by the two first components was split into cells in which we estimated deviations
from the reference. The deviations were computed using all targets from the reference located at a short spatial distance of eachsecondary target. Corrections and filtering were deduced for each cell in the multi-colour space. We applied the technique totwo different datasets: on the one hand, the spectrophotometric catalogue, and, on the other hand, a catalogue of extinctions
based on photometry of Gaia eDR3 and 2MASS. After calibration, the dispersion of the extinction among neighbouring points
in the second catalogue is reduced, regardless of whether reference targets are present locally. Weak structures are then more
apparent. The extinction of high Galactic latitude targets is more tightly correlated with the dust emission, a property acquired
from the first catalogue. A hierarchical inversion technique was applied to the two merged inter-calibrated catalogues to produce
3D extinction density maps corresponding to different volumes and maximum spatial resolution. The maximum resolution is
10pc for a 3000x3000x800pc3 volume around the Sun, and the maximum size of the maps is 10x10x0.8 kpc3 for a resolution of
50pc. Maps can be downloaded or used by means of on-line tools.

Cyanopolyyne line survey towards high-mass star-forming regions with TMRT

53. Y. X. Wang, J. S. Zhang, Y. T. Yan, J. J. Qiu, J. L. Chen, J. Y. Zhao, Y. P. Zou, X. C. Wu, X. L. He, Y. B.
Gong, J. H. Cai F We carried out a cyanopolyyne line survey towards a large sample of HMSFRs using the Shanghai Tian Ma
65m Radio Telescope (TMRT). Our sample consisted of 123 targets taken from the TMRT C band line survey. It included threekinds of sources, namely those with detection of the 6.7 GHz CH3OH maser alone, with detection of the radio recombination line
(RRL) alone, and with detection of both (hereafter referred to as Maser-only, RRL-only, and Maser-RRL sources, respectively).

17

We detected HC3N in 38 sources, HC5N in 11 sources, and HC7N in G24.790+0.084, with the highest detection rate being
found for Maser-RRL sources and a very low detection rate found for RRL-only sources. Their column densities were derived
using the rotational temperature measured from the NH3 lines. And we constructed and fitted the far-infrared (FIR) spectralenergy distributions. Based on these, we derive their dust temperatures, H2 column densities, and abundances of cyanopolyynes
relative to H2. The detection rate, the column density, and the relative abundance of HC3N increase from Maser-only to MaserRRL sources and decrease from Maser-RRL to RRL-only sources. This trend is consistent with the proposed evolutionary trendof HC3N under the assumption that our Maser-only, Maser-RRL, and RRL-only sources correspond to massive young stellar
objects, ultra-compact HII regions, and normal classical HII regions, respectively. Furthermore, a statistical analysis of theintegrated line intensity and column density of HC3N and shock-tracing molecules (SiO, H2CO) enabled us to find positive
correlations between them. This suggests that HC3N may be another tracer of shocks, and should therefore be the subject offurther observations and corresponding chemical simulations. Our results indirectly support the idea that the neutral–neutral
reaction between C2H2 and CN is the dominant formation pathway of HC3N.

54. The initial conditions for young massive cluster formation in the Galactic Centre: convergence of large-scale gas flows

Bethan A. Williams, Daniel L. Walker, Steven N. Longmore, A. T. Barnes, Cara Battersby, Guido Garay, Adam
Ginsburg, Laura Gomez, Jonathan D. Henshaw, Luis C. Ho, J. M. Diederik Kruijssen, Xing Lu, Elisabeth A.
C. Mills, Maya A. Petkova, Qizhou Zhang F Young massive clusters (YMCs) are compact (.1 pc), high-mass (>104
M ) stellar systems of significant scientific interest. Due to their rarity and rapid formation, we have very few examples of
YMC progenitor gas clouds before star formation has begun. As a result, the initial conditions required for YMC formation are
uncertain. We present high-resolution (0.1300 , ∼1000 au) ALMA observations and Mopra single-dish data, showing that Galactic
Centre dust ridge ‘Cloud d’ (G0.412+0.052, mass∼ 7.6 × 104 M , radius∼ 3.2 pc) has the potential to become an Arches-like
YMC (104 M , r∼1 pc), but is not yet forming stars. This would mean it is the youngest known pre-star forming massive
cluster and therefore could be an ideal laboratory for studying the initial conditions of YMC formation. We find 96 sources inthe dust continuum, with masses .3 M and radii of ∼103 au. The source masses and separations are more consistent withthermal rather than turbulent fragmentation. It is not possible to unambiguously determine the dynamical state of most of thesources, as the uncertainty on virial parameter estimates is large. We find evidence for large-scale (∼1 pc) converging gas flows,which could cause the cloud to grow rapidly, gaining 104 M within 105 yr. The highest density gas is found at the convergent
point of the large-scale flows. We expect this cloud to form many high-mass stars, but find no high-mass starless cores. If thesources represent the initial conditions for star formation, the resulting IMF will be bottom-heavy.

55. Hydrogen Emission from Accretion and Outflow in T Tauri Stars

Tom J. G. Wilson, S. Matt, T. J. Harries, G. J. Herczeg F Radiative transfer modelling offers a powerful tool forunderstanding the enigmatic hydrogen emission lines from T Tauri stars. This work compares optical and near-IR spectroscopyof 29 T Tauri stars with our grid of synthetic line profiles. The archival spectra, obtained with VLT’s X-Shooter, provide
simultaneous coverage of many optical and infrared hydrogen lines. The observations exhibit similar morphologies of line
profiles seen in other studies. We used the radiative transfer code TORUS to create synthetic Hα, Paβ, Paγ, and Brγ emission
lines for a fiducial T Tauri model that included axisymmetric magnetospheric accretion and a polar stellar wind. The distributionof Reipurth types and line widths for the synthetic Hα lines is similar to the observed results. However, the modelled infraredlines are narrower than the observations by ≈ 80 kms−1 , and our models predict a significantly higher proportion (≈ 90 percent) of inverse P-Cygni profiles. Furthermore, our radiative transfer models suggest that the frequency of P-Cygni profiles
depends on the ratio of the mass loss to mass accretion rates and blue-shifted sub-continuum absorption was predicted formass loss rates as low as 10−12 M yr−1 . We explore the effect of rotation, turbulence, and the contributions from red-shifted
absorption in an attempt to explain the discrepancy in widths. Our findings show that, singularly, none of these effects issufficient to explain the observed disparity. However, a combination of rotation, turbulence, and non-axisymmetric accretion
may improve the fit of the models to the observed data.

The Mass-Size Relation Of Structures In Molecular Clouds
56. Revisiting
Yuchen Xing, Keping Qiu F We revisit the mass-size relation of molecular cloud structures based on the column density
map of the Cygnus-X molecular cloud complex. We extract 135 column density peaks in Cygnus-X and analyze the column
density distributions around these peaks. The averaged column density profiles, N (R), around all the peaks can be well fittedwith broken power-laws, which are described by an inner power-law index n, outer power-law index m, and the radius RTP andcolumn density NTP at the transition point. We then explore the M − R relation with different samples of cloud structuresby varying the N (R) parameters and the column density threshold, N0 , which determines the boundary of a cloud structure.
We find that only when N0 has a wide range of values, the M − R relation may largely probe the density distribution, and thefitted power-law index of the M − R relation is related to the power-law index of N (R). On the contrary, with a constant N0 ,the M − R relation has no direct connection with the density distribution; in this case, the fitted power-law index of the M − R18relation is equal to 2 (when N0 ≥ NTP and n has a narrow range of values), larger than 2 (when N0 ≥ NTP and n has a wide
range of values), or slightly less than 2 (when N0 < NTP ).

57. Herschel investigation of cores and filamentary structures in the Perseus molecular cloud
Chang Zhang, Guo-Yin Zhang, Jin-Zeng Li, Xue-Mei Li F Cores and filamentary structures are the prime birthplacesof stars, and play key roles in the process of star formation. Latest advances in the methods of multi-scale source and filament
extraction, and in making high-resolution column density map from Herschel multi-wavelength observations enable us to detect
the filamentary network structures in highly complex molecular cloud environments. The statistics for physical parameters showsthat core mass strongly correlates with core dust temperature, and M/L strongly correlates with M/T , which is in line withthe prediction of the blackbody radiation, and can be used to trace evolutionary sequence from unbound starless cores torobust prestellar cores. Crest column densities of the filamentary structures are clearly related with mass per unit length(Mline ), but are uncorrelated by three orders ranging from ∼ 1020 to ∼ 1022 cm−2 with widths. Full width at half maximum(FWHM) have a median value of 0.15 pc, which is consistent with the 0.1 pc typical inner width of the filamentary structures
reported by previous research. We find ∼70% of robust prestellar cores (135/199) embedded in supercritical filaments with
Mline > 16 M /pc, which implies that the gravitationally bound cores come from fragmentation of supercritical filaments. And
on the basis of observational evidences that probability distribution function (PDF) with power-law distribution in the Perseus
south is flatter than north, YSO number is significantly less than that in the north, and dust temperature difference. We inferthat south region is more gravitationally bound than north region.

the secular evolution of proto-planetary disc dust sizes – A comparison be58. Modelling
tween the viscous and magnetic wind caseFrancesco Zagaria, Giovanni P. Rosotti, Cathie J. Clarke, Benoît Tabone F For many years proto-planetary discs
have been thought to evolve viscously: angular momentum redistribution leads to accretion and outward disc spreading. Recently, the hypothesis that accretion is due, instead, to angular momentum removal by magnetic winds gained new popularity:
no disc spreading is expected in this case. In this paper, we run several one-dimensional gas and dust simulations to makepredictions on the time-evolution of disc sizes in the dust and to assess whether they can be used to understand how discs
evolve. We show that viscous and magnetic wind models have very different dust disc radii. In particular, MHD wind models
are compact and their sizes either remain constant or decrease with time. On the contrary, discs become larger with time in
the viscous case (when α & 10−3 ). Although current observations lack enough sensitivity to discriminate between these two
scenarios, higher-sensitivity surveys could be fruitful to this goal on a 1 to 10 Myr age range. When compared with the available
ALMA Band 7 data, both viscous and magnetic wind models are compatible with the observationally-inferred dust radii in
Lupus, Chamaeleon I and Upper Sco. Furthermore, in the drift-dominated regime, the size-luminosity correlation is reproducedin Lupus, both in Band 7 and 3, while in Upper Sco a different slope than in the data is predicted. Sub-structures (potentially
undetected) can explain several outliers with large observed sizes. Higher-angular-resolution observations will be helpful to test
our predictions in the case of more compact discs, expected in both frameworks, particularly at the age of Upper Sco.

59. The Ages of Optically Bright Sub-Clusters in the Serpens Star-Forming Region
Xingyu Zhou, Gregory J. Herczeg, Yao Liu, Min Fang, Michael Kuhn F The Serpens Molecular Cloud is one of themost active star-forming regions within 500 pc, with over one thousand of YSOs at different evolutionary stages. The ages of themember stars inform us about the star formation history of the cloud. In this paper, we develop a spectral energy distribution(SED) fitting method for nearby evolved (diskless) young stars from members of the Pleiades to estimate their ages, with atemperature scale adopted from APOGEE spectra. When compared with literature temperatures of selected YSOs in Orion,
the SED fits to cool (<5000 K) stars have temperatures that differ by an average of < 50 K and have a scatter of 210 K for
both disk-hosting and diskless stars. We then apply this method to YSOs in the Serpens Molecular Cloud to estimate ages of
optical members previously identified from Gaia DR2 astrometry data. The optical members in Serpens are concentrated indifferent subgroups with ages from 4 Myr to 22 Myr; the youngest clusters, W40 and Serpens South, are dusty regions thatlack enough optical members to be included in this analysis. These ages establish that the Serpens Molecular Cloud has been
forming stars for much longer than has been inferred from infrared surveys.

variability of the multiple T Tauri system VW Cha
60. Accretion
Gabriella Zsidi, Eleonora Fiorellino, Ágnes Kóspál, Péter Ábrahám, Attila Bódi, Gaitee Hussain, Carlo F.
Manara, András Pál F Classical T Tauri stars are low-mass objects, which are still accreting material from the surrounding
circumstellar disk. The accretion process is essential in the formation of Sun-like stars and in setting the properties of the disk at
the time when planet formation occurs. We constructed a complex dataset in order to examine the accretion process of VW Cha,
a classical T Tauri multiple system with the aim of studying the physical origin of the photometric and spectroscopic variabilityof the system. The TESS Space Telescope observed VW Cha between 2019 April 22 and June 19, and we complemented these19data with contemporaneous ground-based IC JHK band photometric measurements. In addition, we obtained high-resolution
optical spectra with the VLT/ESPRESSO and the 2.2 m/FEROS instruments. Analyzing these data, we found that the TESS
light curve shows photometric variations on timescales from minutes to weeks with a peak-to-peak amplitude of ∼0.8 mag.
The near-infrared light curves follow the shape of the optical measurements, however, the peak-to-peak amplitudes are slightly
increasing towards the longer wavelengths. We took spectra in both fainter and brighter photometric states of the system,
allowing us to examine the origin of a photometric brightening event. Our results show that this brightening event can be
explained by increased accretion. In addition, our spectroscopic data also suggest that the primary component of VW Cha is aspectroscopic binary, as it was proposed in earlier works.

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