The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 352 — 30 April 2022
Editor: João Alveswww.starformation.news

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Cover image caption
The Cone Nebula in NGC2264. Discovered by William Herschel on December 26, 1785, the nebula lies about 830 parsecs from
Earth in Monoceros. The image is about, or below, 1 pc on the side. The very small scale structure of this cloud is mesmerizing.
Credit: Hubble Legacy Archive, NASA, ESA - Processing & Licence: Judy Schmidt
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.

Abstractsof the angular momentum during gravitational fragmentation of molecular
1. Evolution
clouds
G. Arroyo-Chávez, E. Vázquez-Semadeni F We investigate the origin of the observed scaling j ∼ R3/2 between thespecific angular momentum j and the radius R of molecular clouds (MCs) and their their substructures, and of the observed
near independence of β, the ratio of rotational to gravitational energy, from R. To this end, we measure the angular momentum(AM) of sets of particles in an SPH simulation of the formation, collapse and fragmentation of giant MCs. The sets of SPH
particles are defined either as “clumps” (connected particle sets), or as lagrangian sets that conform a connected clump only
at a certain time tdef. We find that: i) Clumps evolve along the observed jR relation at all times, ii) Lagrangian particle
sets evolve along the observed relation when the volume containing them also contains a large number of other “intruder”
particles. Otherwise, they evolve with j ∼ cst. iii) Tracking lagrangian sets to the future, we find that a subset of the
SPH particles participates in the collapse, while another disperses away. iv) Noting that, under AM conservation, β increases
during contraction, we suggest that its near independence of radius may arise from the competition between this increase andan increase in the AM exchange rate at higher rotational energy density gradient. v) We suggest that, if MCs are globallydominated by gravity, the observed jR relation arises because the observational selection of its dense structures amounts toselecting the fragments that have lost AM via Reynolds stresses from their neighbors.

2. Core formation via filament fragmentation and the impact of ambient pressure on it
S. Anathpindika, J. Di Francesco F Prestellar cores are generally spheroidal, some of which appear oblate while others
appear prolate. Very few of them appear circular in projection. Little, however, is understood about the processes or thephysical conditions under which prolate/oblate cores form. We find that an initially sub-critical filament experiencing relatively
low pressure (. 104 K cm−3 ) forms prolate cores (i.e., those with axial ratios in excess of unity) via gradual accumulationof gas in density crests. Meanwhile, a filament that is initially transcritical and experiences pressure similar to that in the
Solar neighbourhood (between few × 104 K cm−3 - few × 105 K cm−3 ) forms oblate cores (i.e., those with axial ratios lessthan unity) via Jeans like fragmentation. At higher pressure, however, fragments within the filament do not tend to survive
as they rebound soon after formation. We also argue that quasi-oscillatory features of velocity gradient observed along thefilament axis, and in the direction orthogonal to the axis, are integral to the filament evolution process and arise due to thegrowth of corrugations on its surface. The axial component of the velocity gradient, in particular, traces the gas-flow along thefilament length. We therefore posit that it could be used to constrain the filament-formation mechanism. The magnitude of therespective components of velocity gradients increases with increasing external pressure.

2

3. Infrared study of the star-forming region associated with the UC HII regions G45.07+0.13
and G45.12+0.13

Naira Azatyan, Elena Nikoghosyan, Hayk Harutyunian, Daniel Baghdasaryan, Derenik Andreasyan F UCHII
regions are an important phase in the formation and early evolution of massive stars and a key component of the interstellar
medium. The main objectives of this work are to study the young stellar objects (YSOs) associated with the G45.07+0.13(G45.07) and G45.12+0.13 (G45.12) UCHII regions, as well as the interstellar medium in which they are embedded. We determined the distribution of the hydrogen column density (N(H2)) and dust temperature (Td) in the molecular cloud using Herschelimages. We used infrared photometric data to identify and classify the YSOs. We also constructed a colour-magnitude diagramand K luminosity functions (KLFs) to compare the parameters of YSOs with the results of the radiative transfer models. We
found that N(H2) varies from about 3.0 to 5.5x1023 cm−2 within the G45.07 and G45.12 regions, respectively. The maximum Tdvalue is 35K in G45.12 and 42K in G45.07. Td reaches about 18-20K at distances of 2.6 and 3.7pc from IRAS19110+1045(G45.07) and IRAS19111+1048 (G45.12), respectively. The gas-dust mass value included in G45.12 is 3.4x105 Msun and1.7x105 Msun in G45.07. The UCHII regions are connected through a cold (Td=19K) bridge. The density distribution of
518 YSOs exhibits dense clusters around both IRAS sources. The parameters of YSOs in the IRAS clusters (124 objects) and
394 non-cluster objects surrounding them show some differences. About 75% of the YSOs belonging to the IRAS clusters havean evolutionary age greater than 106 years. Their slope alpha of the KLF agrees well with a Salpeter-type Initial Mass Function(IMF) (gamma=1.35) for a high mass range (O-F stars, beta=2) at 1Myr. The non-cluster objects are uniformly distributedin the molecular cloud, 80% of which are located to the right of the 0.1Myr isochrone. Based on the small age spread of thestellar objects, we suggest that the clusters originate from a single triggering shock.

4. Protostellar and Protoplanetary Disk Masses in the Serpens Region

Alexa R. Anderson, Jonathan P. Williams, Nienke van der Marel, Charles J. Law, Luca Ricci, John J. Tobin,
Simin Tong F We present the results from an Atacama Large Millimeter/Submillimeter Array (ALMA) 1.3 mm continuumand 12 CO (J = 2 − 1) line survey spread over 10 square degrees in the Serpens star-forming region of 320 young stellar
objects, 302 of which are likely members of Serpens (16 Class I, 35 Flat spectrum, 235 Class II, and 16 Class III). From thecontinuum data, we derive disk dust masses and show that they systematically decline from Class I to Flat spectrum to Class
II sources. Grouped by stellar evolutionary state, the disk mass distributions are similar to other young (< 3 Myr) regions,indicating that the large scale environment of a star-forming region does not strongly affect its overall disk dust mass properties.
These comparisons between populations reinforce previous conclusions that disks in the Ophiuchus star-forming region haveanomalously low masses at all evolutionary stages. Additionally, we find a single deeply embedded protostar that has not been
documented elsewhere in the literature and, from the CO line data, 15 protostellar outflows which we catalog here.

collision as origin of the G31.41+0.31 massive protocluster
5. Cloud-cloud
M. T. Beltrán, V. M. Rivilla, M. S. N. Kumar, R. Cesaroni, D. Galli F The G31.41+0.31 (G31) hot molecularcore (HMC) is a high-mass protocluster showing accelerated infall and rotational spin-up that is well studied at high-angularresolution. To complement the accurate view of the small scale in G31, we have traced the kinematics of the large-scale material
by carrying out N2 H+ (1–0) observations with the IRAM 30m telescope of an area of ∼6×6 arcmin2 around the HMC. The N2 H+
observations have revealed a large-scale (5 pc) hub-filament system (HFS) composed by at least four filamentary arms and a
NNE–SSW velocity gradient (∼0.4 km/s/pc) between the northern and southern filaments. The linewidth increases towards the
hub at the center of the HFS reaching values of 2.5–3 km s−1 in the central 1 pc. The origin of the large-scale velocity gradient islikely cloud-cloud collision. In this scenario, the filaments in G31 would have formed by compression resulting from the collisionand the rotation of the HMC observed at scales of 1000 au would have been induced by shear caused by the cloud-cloud collisionat scales of a few pc. We conclude that G31 represents a HFS in a compressed layer with an orthogonal orientation to the planeof the sky, and represents a benchmark for the filaments-to-clusters paradigm of star formation.

Simultaneous evidence of edge collapse and hub-filament configurations: A rare case

6. study of a Giant Molecular Filament G45.3+0.1

N. K. Bhadari, L. K. Dewangan, D. K. Ojha, L. E. Pirogov, A. K. Maity F We study multiwavelength and multiscaledata to investigate the kinematics of molecular gas associated with the star-forming complexes G045.49+00.04 (G45E) andG045.14+00.14 (G45W) in the Aquila constellation. An analysis of the FUGIN 13 CO(1-0) line data unveils the presence of agiant molecular filament (GMF G45.3+0.1; length ∼75 pc, mass ∼1.1×106 M ) having a coherent velocity structure at [53, 63]
km s−1 . The GMF G45.3+0.1 hosts G45E and G45W complexes at its opposite ends. We find large scale velocity oscillations
along GMF G45.3+0.1, which also reveals the linear velocity gradients of −0.064 and +0.032 km s−1 pc−1 at its edges. The
photometric analysis of point-like sources shows the clustering of young stellar object (YSO) candidate sources at the filament’s
edges where the presence of dense gas and HII regions are also spatially observed. The Herschel continuum maps along with
the CHIMPS 13 CO(3-2) line data unravel the presence of parsec scale hub-filament systems (HFSs) in both the sites, G45E
and G45W. Our study suggests that the global collapse of GMF G45.3+0.1 is end-dominated, with addition to the signature of3

global nonisotropic collapse (GNIC) at the edges. Overall, GMF G45.3+0.1 is the first observational sample of filament where
the edge collapse and the hub-filament configurations are simultaneously investigated. These observations open up the new
possibility of massive star formation, including the formation of HFSs.

look at the multiphase interstellar medium with synthetic observations of low7. First
frequency Faraday tomography
A. Bracco, E. Ntormousi, V. Jelić, M. Padovani, B. Šiljeg, A. Erceg, L. Turić, L. Ceraj, I. Šnidarić F Faraday
tomography of radio polarimetric data below 200 MHz from LOFAR are providing us with a new perspective on the diffuse
and magnetized interstellar medium (ISM). Of particular interest is the discovery of Faraday-rotated synchrotron polarization
associated with neutral gas, as traced by atomic hydrogen (HI) and dust. Here we present the first in-depth numerical study ofthese LOFAR results. We produce and analyze comprehensive synthetic observations of low-frequency synchrotron polarizationfrom MHD simulations of colliding super shells in the multiphase ISM. We define five distinct gas phases over more than fourorders of magnitude in gas temperature and density, ranging from hot, and warm, fully ionized gas to cold neutral medium.
We focus on the contribution of each gas phase to synthetic observations of both rotation measure and synchrotron polarized
intensity below 200 MHz. We also investigate the link between the latter and synthetic observations of optically thin HI gas.
We find that, not only the fully ionized gas but also the warm partially ionized and neutral phases strongly contribute to thetotal rotation measure and polarized intensity. However, the contribution of each phase to the observables strongly depends
on the choice of integration axis and the orientation of the mean magnetic field with respect to the shell-collision axis. Strong
correlation between HI synthetic data and synchrotron polarized intensity, reminiscent of LOFAR results, is obtained with linesof sight perpendicular to the mean magnetic field direction. Our study suggests that multiphase modelling of MHD processes
is needed in order to interpret observations of the radio sky at low frequency. This work is a first step toward understanding
the complexity of low-frequency synchrotron emission that will be soon revolutionized by large-scale surveys with LOFAR andthe SKA.

8. A Self-Consistent Model for Dust-Gas Coupling in Protoplanetary Disks

Konstantin Batygin, Alessandro Morbidelli F Various physical processes that ensue within protoplanetary disks – including vertical settling of icy/rocky grains, radial drift of solids, planetesimal formation, as well as planetary accretion itself– are facilitated by hydrodynamic interactions between H/He gas and high-Z dust. The Stokes number, which quantifies thestrength of dust-gas coupling, thus plays a central role in protoplanetary disk evolution, and its poor determination constitutes
an important source of uncertainty within the theory of planet formation. In this work, we present a simple model for dust-gas
coupling, and demonstrate that for a specified combination of the nebular accretion rate, Ṁ , and turbulence parameter, α,
the radial profile of the Stokes number can be calculated uniquely. Our model indicates that the Stokes number grows sublinearly with orbital radius, but increases dramatically across the water-ice line. For fiducial protoplanetary disk parametersof Ṁ = 10−8 M /year and α = 10−3 , our theory yields characteristic values of the Stokes number on the order of St ∼ 10−4
(corresponding to ∼mm-sized silicate dust) in the inner nebula and St ∼ 10−1 (corresponding to ∼few-cm-sized icy grains), in
the outer regions of the disk. Accordingly, solids are expected to settle into a thin sub-disk at large stellocentric distances, whileremaining vertically well-mixed inside the ice line.

Implications of Relatively High Levels of Initial 60 Fe in Iron Meteorites for the
9. Possible
Non-Carbonaceous – Carbonaceous Meteorite Dichotomy and Solar Nebula Formation
Alan P. Boss F Cook et al. (2021) found that iron meteorites have an initial abundance ratio of the short-lived isotope
60
Fe to the stable isotope 56 Fe of 60 Fe/56 Fe ∼ (6.4 ± 2.0) × 10−7 . This appears to require the injection of live 60 Fe from a
Type II supernova (SN II) into the presolar molecular cloud core, as the observed ratio is over a factor of ten times higher
than would be expected to be found in the ambient interstellar medium (ISM) as a result of galactic chemical evolution. The
supernova triggering and injection scenario offers a ready explanation for an elevated initial 60 Fe level, and in addition provides
a physical mechanism for explaining the non-carbonaceous – carbonaceous (NC-CC) dichotomy of meteorites. The NC-CC
scenario hypothesizes the solar nebula first accreted material that was enriched in supernova-derived nuclides, and then later
accreted material depleted in supernova-derived nuclides. While the NC-CC dichotomy refers to stable nuclides, not short-lived
isotopes like 60 Fe, the SN II triggering hypothesis provides an explanation for the otherwise unexplained change in nuclides
being accreted by the solar nebula. Three dimensional hydrodynamical models of SN II shock-triggered collapse show thatafter triggering collapse of the presolar cloud core, the shock front sweeps away the local ISM while accelerating the resulting
protostar/disk to a speed of several km/s, sufficient for the protostar/disk system to encounter within ∼ 1 Myr the more distantregions of a giant molecular cloud complex that might be expected to have a depleted inventory of supernova-derived nuclides.

4

The Gaia-ESO Survey: Constraining evolutionary models and ages for young low mass

10. stars with measurements of lithium depletion and rotation

A. S. Binks, R. D. Jeffries, G. G. Sacco, R. J. Jackson, L. Cao, A. Bayo, M. Bergemann, R. Bonito, G.
Gilmore, A. Gonneau, F. Jiminéz-Esteban, L. Morbidelli, S. Randich, V. Roccatagliata, R. Smiljanic, S. Zaggia
F A growing disquiet has emerged in recent years that standard stellar models are at odds with observations of the colourmagnitude diagrams (CMDs) and lithium depletion patterns of pre main sequence (PMS) stars in clusters. In this work weselect 1,246 high probability K/M-type constituent members of 5 young open clusters (5–125 Myr) in the Gaia-ESO Survey totest a series of models that use standard input physics and others that incorporate surface magnetic fields or cool starspots.
We find that: standard models provide systematically under-luminous isochrones for low-mass stars in the CMD and fail topredict Li-depletion of the right strength at the right colour; magnetic models provide better CMD fits with isochrones thatare ∼ 1.5 − 2 times older, and provide better matches to Li depletion patterns. We investigate how rotation periods, most ofwhich are determined here for the first time from Transiting Exoplanet Survey Satellite data, correlate with CMD position and
Li. Among the K-stars in the older clusters we find the brightest and least Li-depleted are the fastest rotators, demonstrating
the classic "Li-rotation connection" for the first time at ∼ 35 Myr in NGC 2547, and finding some evidence that it exists in theearly M-stars of NGC 2264 at < 10 Myr. However, the wide dispersion in Li depletion observed in fully-convective M-dwarfs
in the γ Vel cluster at ∼ 20 Myr appears not to be correlated with rotation and is challenging to explain without a very large(> 10 Myr) age spread.

Two Rings and a Marginally Resolved, 5 AU, Disk Around LkCa 15 Identified Via Near

11. Infrared Sparse Aperture Masking Interferometry

Dori Blakely, Logan Francis, Doug Johnstone, Anthony Soulain, Peter Tuthill, Anthony Cheetham, Joel
Sanchez-Bermudez, Anand Sivaramakrishnan, Ruobing Dong, Nienke van der Marel, Rachel Cooper, Arthur
Vigan, Faustine Cantalloube F Sparse aperture masking interferometry (SAM) is a high resolution observing technique thatallows for imaging at and beyond a telescope’s diffraction limit. The technique is ideal for searching for stellar companions at
small separations from their host star; however, previous analysis of SAM observations of young stars surrounded by dusty disks
have had difficulties disentangling planet and extended disk emission. We analyse VLT/SPHERE-IRDIS SAM observations of
the transition disk LkCa 15, model the extended disk emission, probe for planets at small separations, and improve contrast limits for planets. We fit geometrical models directly to the interferometric observables and recover previously observed extended
disk emission. We use dynamic nested sampling to estimate uncertainties on our model parameters and to calculate evidences
to perform model comparison. We compare our extended disk emission models against point source models to robustly conclude
that the system is dominated by extended emission within 50 au. We report detections of two previously observed asymmetricrings at ∼17 au and ∼45 au. The peak brightness location of each model ring is consistent with the previous observations.
We also, for the first time with imaging, robustly recover an elliptical Gaussian inner disk, previously inferred via SED fitting.
This inner disk has a FWHM of 5 au and a similar inclination and orientation as the outer rings. Finally, we recover no clear
evidence for candidate planets. By modelling the extended disk emission, we are able to place a lower limit on the near infraredcompanion contrast of at least 1000.

UV-shielding in the terrestrial planet-forming zone: Implications from water
12. Water
emission
Arthur D. Bosman, Edwin A. Bergin, Jenny Calahan, Sara E. Duval F Mid-infrared spectroscopy is one of the few
ways to observe the composition of the terrestial planet forming zone, the inner few au, of proto-planetary disks. The species
currently detected in the disk atmosphere, for example CO, CO2, H2O and C2H2, are theoretically enough to constrain the C/O
ratio in the disk surface. However, thermo-chemical models have difficulties in reproducing the full array of detected species
in the mid-infrared simultaneously. In an effort to get closer to the observed spectra, we have included water UV-shielding aswell as more efficient chemical heating into thermo-chemical code Dust And Lines. We find that both are required to matchthe observed emission spectrum. Efficient chemical heating, in addition to traditional heating from UV photons, is necessary toelevate the temperature of the water emitting layer to match the observed excitation temperature of water. We find that water
UV-shielding stops UV photons from reaching deep into the disk, cooling down the lower layers with higher column. These two
effects create a hot emitting layer of water with a column of 1-10×1018 cm−2 . This is only 1-10mid-infrared wavelengths in themodels and represents < 1% of the total water column.

5

of Embedded Jovian Planet Formation At A Wide Separation Around AB Au13. Images
rigae
Thayne Currie, Kellen Lawson, Glenn Schneider, Wladimir Lyra, John Wisniewski, Carol Grady, Olivier
Guyon, Motohide Tamura, Takayuki Kotani, Hajime Kawahara, Timothy Brandt, Taichi Uyama, Takayuki
Muto, Ruobing Dong, Tomoyuki Kudo, Jun Hashimoto, Misato Fukagawa, Kevin Wagner, Julien Lozi, Jeffrey Chilcote, Taylor Tobin, Tyler Groff, Kimberly Ward-Duong, William Januszewski, Barnaby Norris, Peter
Tuthill, Nienke van der Marel, Michael Sitko, Vincent Deo, Sebastien Vievard, Nemanja Jovanovic, Frantz
Martinache, Nour Skaf F Direct images of protoplanets embedded in disks around infant stars provide the key to understanding the formation of gas giant planets like Jupiter. Using the Subaru Telescope and Hubble Space Telescope, we findevidence for a jovian protoplanet around AB Aurigae orbiting at a wide projected separation (93 au), likely responsible for multiple planet-induced features in the disk. Its emission is reproducible as reprocessed radiation from an embedded protoplanet.
We also identify two structures located at 430-580 au that are candidate sites of planet formation. These data reveal planet
formation in the embedded phase and a protoplanet discovery at wide, > 50 au separations characteristic of most imaged exoplanets. With at least one clump-like protoplanet and multiple spiral arms, the AB Aur system may also provide the evidence
for a long-considered alternative to the canonical model for Jupiter’s formation: disk (gravitational) instability.

Dusty circumbinary discs: inner cavity structures and stopping locations of migrating

14. planets

Gavin A. L. Coleman, Richard P. Nelson, Amaury H. M. J. Triaud F We present the results of two-fluid hydrodynamical simulations of circumbinary discs consisting of gas and dust, with and without embedded planets, to examine theinfluence of the dust on the structure of the tidally truncated inner cavity and on the parking locations of migrating planets.
In this proof-of-concept study, we consider Kepler-16 and -34 analogues, and examine dust fluids with Stokes numbers in therange 10−4 ≤ St ≤ 10−1 and dust-to-gas ratios of 0.01 and 1. For the canonical dust-to-gas ratio of 0.01, we find the inclusionof the dust has only a minor effect on the cavity and stopping locations of embedded planets compared to dust-free simulations.
However, for the enhanced dust-to-gas ratio of unity, assumed to arise because of significant dust drift and accumulation, we
find that the dust can have a dramatic effect by shrinking and circularising the inner cavity, which brings the parking locationsof planets closer to the central binary. This work demonstrates the importance of considering both gas and dust in studies ofcircumbinary discs and planets, and provides a potential means of explaining the orbital properties of circumbinary planets
such as Kepler-34b, which have hitherto been difficult to explain using gas-only hydrodynamical simulations.

15. The Many-Faceted Light Curves of Young Disk-bearing Stars in Taurus as Seen by K2
Ann Marie Cody, Lynne A. Hillenbrand, Luisa M. Rebull F We present a comprehensive study of the variability
properties of young disk-bearing stars in the Taurus star-forming region, paralleling our previous investigation in rho Oph andUpper Sco. A sample of 99 confirmed Taurus association members is placed in the diagnostic Q-M plane of flux asymmetry (M)and quasi-periodicity (Q), which guides our assignment of variability classes. We find a similar proportion of flux-symmetricvariables in Taurus, but more bursters and fewer dippers relative to Upper Sco. The regions also differ in that the amplitudes
for periodic and quasi-periodic sources are larger in Taurus relative to the more evolved Upper Sco star/disk systems. The
relationship between photometric variability patterns at optical wavelengths, which arise in the inner disk and at the stellar
surface, are assessed relative to available disk inclination measurements.

New evidences in IRDC G333.73+0.37: colliding filamentary clouds, hub-filament sys-

16. tem, and embedded cores

L. K. Dewangan F To unravel the star formation process, we present a multi-scale and multi-wavelength study of the filamentary infrared dark cloud (IRDC) G333.73+0.37, which hosts previously known two HII regions located at its center. EachHII region is associated with a mid-infrared source, and is excited by a massive OB star. Two filamentary structures and a
hub-filament system (HFS) associated with one HII region are investigated in absorption using the Spitzer 8.0 µm image. The
13
CO(J = 2-1) and C18 O(J = 2-1) line data reveal two velocity components (around −35.5 and −33.5 km s−1 ) toward the
IRDC, favouring the presence of two filamentary clouds at different velocities. Nonthermal (or turbulent) motions are depictedin the IRDC using the C18 O line data. The spatial distribution of young stellar objects (YSOs) identified using the VVV
near-infrared data traces star formation activities in the IRDC. Low-mass cores are identified toward both the HII regions
using the ALMA 1.38 mm continuum map. The VLT/NACO adaptive-optics L0 -band images show the presence of at least
three point-like sources and the absence of small-scale features in the inner 4000 AU around YSOs NIR31 and MIR 16 locatedtoward the HII regions. The HII regions and groups of YSO are observed toward the central part of the IRDC, where the two
filamentary clouds intersect. A scenario of cloud-cloud collision or converging flows in the IRDC seems to be applicable, which
may explain star formation activities including HFS and massive stars.

6

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Evidence for a

17. Molecular Jet Launched at an Unprecedented Early Phase of Protostellar evolution

Somnath Dutta, Chin-Fei Lee, Naomi Hirano, Tie Liu, Doug Johnstone, Sheng-Yuan Liu, Kenichi Tatematsu,
Paul F. Goldsmith, Dipen Sahu, Neal J. Evans, Patricio Sanhueza, Woojin Kwon, Sheng-Li Qin, Manash
Ranjan Samal, Qizhou Zhang, Kee-Tae Kim, Hsien Shang, Chang Won Lee, Anthony Moraghan, Kai-Syun
Jhan, Shanghuo Li, Jeong-Eun Lee, Alessio Traficante, Mika Juvela, Leonardo Bronfman, David Eden, ArchanaSoam, Jinhua He, Hong-li Liu, Yi-Jehng Kuan, Veli-Matti Pelkonen, Qiuyi Luo, Hee-Weon Yi, Shih-Ying Hsu F
Protostellar outflows and jets play a vital role in star formation as they carry away excess angular momentum from the inner disk
surface, allowing the material to be transferred toward the central protostar. Theoretically, low velocity and poorly collimatedoutflows appear from the beginning of the collapse, at the first hydrostatic core (FHSC) stage. With growing protostellar
core mass, high-density jets are launched which entrain an outflow from the infalling envelope. Until now, molecular jets havebeen observed at high velocity (& 100 km/s) in early Class 0 protostars. We, for the first time, detect a dense molecular jet
in SiO emission with small-velocity (∼ 4.2 km s−1 , deprojected ∼ 24 km s−1 ) from source G208.89-20.04Walma (hereafter,
G208Walma) using ALMA Band 6 observations. This object has some characteristics of FHSCs, such as a small outflow/jet
velocity, extended 1.3 mm continuum emission, and N2 D+ line emission. Additional characteristics, however, are typical of early
protostars: collimated outflow and SiO jet. The full extent of the outflow corresponds to a dynamical time scale of ∼ 930+200−100
years. The spectral energy distribution also suggests a very young source having an upper limit of Tbol ∼ 31 K and Lbol ∼ 0.8
L . We conclude that G208Walma is likely in the transition phase from FHSC to protostar, and the molecular jet has beenlaunched within a few hundred years of initial collapse. Therefore, G208Walma may be the earliest object discovered in the
protostellar phase with a molecular jet.

Different molecular filament widths as tracers of accretion onto filaments

18. Gilberto C. Gómez, Catherine Walsh, Aina Palau F We explore how dense filament widths, when measured using
different molecular species, may change as a consequence of gas accretion toward the filament. As a gas parcel falls into thefilament, it will experience different density, temperature, and extinction values. The rate at which this environment changes willaffect differently the abundance of different molecules. So, a molecule that forms quickly will better reflect the local physicalconditions a gas parcel experiences than a slower-forming molecule. Since these differences depend on how the respective
timescales compare, the different molecular distributions should reflect how rapidly the environment changes, i.e., the accretion
rate toward the filament. We find that the filament widths measured from time-dependent abundances for C2H, CO, CN, CS,
and C3H2, are sensitive the most to this effect, being those molecules the ones presenting also the wider filament widths. On
the contrary, molecules such as N2H+, NH3, H2CO, HNC or CH3OH are not so sensitive to accretion and present the narrowest
filament widths. We propose that ratios of filament widths for different tracers could be a useful tool to estimate the accretion
rate onto the filament.

Prospects for Hurricane-like Vortices in Protoplanetary Disks
19. TheKonstantin Gerbig, Gregory Laughlin F When ice on the surface of dust grains in protoplanetary disk sublimates, it
adds its latent heat of water sublimation to the surrounding flow. Drawing on the analogy provided by tropical cyclones on
Earth, we investigate if this energy source is sufficient to sustain or magnify anticyclonic disk vortices that would otherwise fallvictim to viscous dissipation. An analytical treatment, supported by exploratory two-dimensional simulations, suggests thateven modestly under-saturated flows can extend the lifetime of vortices, potentially to a degree sufficient to aid particle trapping
and planetesimal formation. We expect the best conditions for this mechanism to occur will be found near the disk’s water ice
line if turbulent motions displace gas parcels out of thermodynamic equilibrium with the dust mid-plane.

of magnetic field orientations in dense cores on gas kinematics in protostellar
20. Effects
envelopes
Aashish Gupta, Hsi-Wei Yen, Patrick Koch, Pierre Bastien, Tyler L. Bourke, Eun Jung Chung, Tetsuo
Hasegawa, Charles L. H. Hull, Shu-ichiro Inutsuka, Jungmi Kwon, Woojin Kwon, Shih-Ping Lai, Chang Won
Lee, Chin-Fei Lee, Kate Pattle, Keping Qiu, Mehrnoosh Tahani, Motohide Tamura, Derek Ward-Thompson
F Theoretically, misalignment between the magnetic field and rotational axis in a dense core is considered to be dynamicallyimportant in the star formation process, however, extent of this influence remains observationally unclear. For a sample of 32
Class 0 and I protostars in the Perseus Molecular Cloud, we analyzed gas motions using C18 O data from the SMA MASSES
survey and the magnetic field structures using 850 µm polarimetric data from the JCMT BISTRO-1 survey and archive. We
do not find any significant correlation between the velocity gradients in the C18 O emission in the protostellar envelopes at a1,000 au scale and the misalignment between the outflows and magnetic field orientations in the dense cores at a 4,000 au scale,and there is also no correlation between the velocity gradients and the angular dispersions of the magnetic fields. However, asignificant dependence on the misalignment angles emerges after we normalize the rotational motion by the infalling motion,
where the ratios increase from . 1 to & 1 with increasing misalignment angles. This suggests that the misalignment could7

prompt angular momentum transportation to the envelope scale but is not a dominant factor in determining the envelope
rotation, and other parameters, like mass accretion in protostellar sources, also play an important role. These results remain
valid after taking into account projection effects. The comparison between our estimated angular momentum in the protostellar
envelopes and the sizes of the known protostellar disks suggests that significant angular momentum is likely lost between radiiof ∼1,000-100 au in protostellar envelopes.

ZTF Look at Optical Variability of Young Stellar Objects in the North America and21. A
Pelican Nebulae Complex
Lynne A. Hillenbrand, Thaddaeus J. Kiker, Miles Gee, Owen Lester, Noah L. Braunfeld, Luisa M. Rebull,Michael A. Kuhn F We present a study of 323 photometrically variable young stellar objects that are likely members of
the North America and Pelican (NAP) nebulae star forming region. To do so, we utilize over two years of data in the g andr photometric bands from the Zwicky Transient Facility (ZTF). We first investigate periodic variability, finding 46 objects(∼15% of the sample) with significant periods that phase well, and can be attributed to stellar rotation. We then use the quasiperiodicity (Q) and flux asymmetry (M) variability metrics to assign morphological classifications to the remaining aperiodic
light curves. Another ∼39% of the variable star sample beyond the periodic sources are also flux-symmetric, but with a quasiperiodic (moderate Q) or stochastic (high Q) nature. Concerning flux-asymmetric sources, our analysis reveals ∼14% bursters(high negative M ) and ∼29% dippers (high positive M ). We also investigate the relationship between variability slopes in
the g vs g − r color-magnitude diagram, and the light curve morphological classes. Burster-type objects have shallow slopes,
while dipper-type variables tend to have higher slopes that are consistent with extinction driven variability. Our work is oneof the earliest applications of the Q and M metrics to ground-based data. We therefore contrast the Q values of high-cadence
and high-precision space-based data, for which these metrics were designed, with Q determinations resulting from degradedspace-based lightcurves that have the cadence and photometric precision characteristic of ground-based data.

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): A Panchro-

22. matic View of DO Tau’s Complex Kilo-au Environment

Jane Huang, Christian Ginski, Myriam Benisty, Bin Ren, Alexander J. Bohn, Élodie Choquet, Karin I. Öberg,Álvaro Ribas, Jaehan Bae, Edwin A. Bergin, Til Birnstiel, Yann Boehler, Stefano Facchini, Daniel Harsono,
Michiel Hogerheijde, Feng Long, Carlo F. Manara, François Ménard, Paola Pinilla, Christophe Pinte, ChristianRab, Jonathan P. Williams, Alice Zurlo F While protoplanetary disks are often treated as isolated systems in planet
formation models, observations increasingly suggest that vigorous interactions between Class II disks and their environments
are not rare. DO Tau is a T Tauri star that has previously been hypothesized to have undergone a close encounter with the HV
Tau system. As part of the DESTINYS ESO Large Programme, we present new VLT/SPHERE polarimetric observations of DO
Tau and combine them with archival HST scattered light images and ALMA observations of CO isotopologues and CS to map
a network of complex structures. The SPHERE and ALMA observations show that the circumstellar disk is connected to arms
extending out to several hundred au. HST and ALMA also reveal stream-like structures northeast of DO Tau, some of which
are at least several thousand au long. These streams appear not to be gravitationally bound to DO Tau, and comparisons withprevious Herschel far-IR observations suggest that the streams are part of a bridge-like structure connecting DO Tau and HVTau. We also detect a fainter redshifted counterpart to a previously known blueshifted CO outflow. While some of DO Tau’s
complex structures could be attributed to a recent disk-disk encounter, they might be explained alternatively by interactions
with remnant material from the star formation process. These panchromatic observations of DO Tau highlight the need tocontextualize the evolution of Class II disks by examining processes occurring over a wide range of size scales.

Few Observation Binary Orbit Solver (FOBOS) from two (or more) astrometric obser-

23. vations

Rebecca J. Houghton, Simon P. Goodwin F We have developed a new, fast method of estimating the orbital propertiesof a binary or triple system using as few as two epochs of astrometric data. FOBOS (Few Observation Binary Orbit Solver)
uses a flat prior brute force Monte Carlo method to produce probability density functions of the likely orbital parameters. We
test the code on fake observations and show that it can (fairly often) constrain the semi-major axis to within a factor of 2-3, andthe inclination to within ∼20◦ from only two astrometric observations. We also show that the 68 and 95 per cent confidence
intervals are statistically reliable. Applying this method to triple systems allows the relative inclination of the secondary andtertiary star orbits to be constrained. FOBOS can usually find a statistically significant number of possible matches in CPU
minutes for binary systems, and CPU hours for triple systems.

8young embedded disk L1527 IRS: constraints on the water snowline and cosmic ray
24. Theionization rate from HCO+ observations
Merel L. R. van ’t Hoff, Margot Leemker, John J. Tobin, Daniel Harsono, Jes K. Jørgensen, Edwin A. Bergin
F The water snowline in circumstellar disks is a crucial component in planet formation, but direct observational constraints
on its location remain sparse due to the difficulty of observing water in both young embedded and mature protoplanetarydisks. Chemical imaging provides an alternative route to locate the snowline, and HCO+ isotopologues have been shown to
be good tracers in protostellar envelopes and Herbig disks. Here we present ∼0.500 resolution (∼35 au radius) Atacama Large
Millimeter/submillimeter Array (ALMA) observations of HCO+ J = 4 − 3 and H13 CO+ J = 3 − 2 toward the young (Class0/I) disk L1527 IRS. Using a source-specific physical model with the midplane snowline at 3.4 au and a small chemical network,
we are able to reproduce the HCO+ and H13 CO+ emission, but for HCO+ only when the cosmic ray ionization rate is loweredto 10−18 s−1 . Even though the observations are not sensitive to the expected HCO+ abundance drop across the snowline, thereduction in HCO+ above the snow surface and the global temperature structure allow us to constrain a snowline location
between 1.8 and 4.1 au. Deep observations are required to eliminate the envelope contribution to the emission and to derivemore stringent constraints on the snowline location. Locating the snowline in young disks directly with observations of H2 O
isotopologues may therefore still be an alternative option. With a direct snowline measurement, HCO+ will be able to provide
constraints on the ionization rate.

25. Correlation between the gas-phase metallicity and ionization parameter in extragalactic
HII regions

Xihan Ji, Renbin Yan F The variations of the metallicity and ionization parameter in HII regions are usually thought to be
the dominant factors that produce the variations we see in the observed emission line spectra. There is an increasing amountof evidence that these two quantities are physically correlated, although the exact form of this correlation is debatable in theliterature. Simulated emission line spectra from photoionized clouds provide important clues about the physical conditions of
HII regions and are frequently used for deriving metallicities and ionization parameters. Through a systematic investigation on
the assumptions and methodology used in applying photoionization models, we find that the derived correlation has a strong
dependence on the choice of model parameters. On the one hand, models that give consistent predictions over multiple emissionline ratios yield a positive correlation between the metallicity and ionization parameter for the general population of HII regions.
On the other hand, models that are inconsistent with the data locus in the line-ratio space yield discrepant correlations whendifferent subsets of line ratios are used in the derivation. The correlation between the metallicity and ionization parameterhas a secondary dependence on the SFR surface density, with the higher SFR regions showing higher ionization parameter but
weaker correlations. The existence of the positive correlation contradicts the wind-driven bubble model for HII regions. We
explore assumptions in the models and conclude that there is a potential bias associated with the geometry. However, this is stillinsufficient to explain the correlation. Mechanisms that suppress the dynamical influence of stellar winds in realistic HII regions
might be the key to solving this puzzle, though more sophisticated combinations of dynamical models and photoionization
models to test are required.

Nucleation and growth of iron pebbles explains the formation of iron-rich planets akin26. to Mercury

Anders Johansen, Caroline Dorn F The pathway to forming the iron-rich planet Mercury remains mysterious. Mercury’score makes up 70% of the planetary mass, which implies a significant enrichment of iron relative to silicates, while its mantle
is strongly depleted in oxidized iron. The high core mass fraction is traditionally ascribed to evaporative loss of silicates, e.g.
following a giant impact, but the high abundance of moderately volatile elements in the mantle of Mercury is inconsistent withreaching temperatures much above 1,000 K during its formation. Here we explore the nucleation of solid particles from a gasof solar composition that cools down in the hot inner regions of the protoplanetary disc. The high surface tension of ironcauses iron particles to nucleate homogeneously (i.e., not on a more refractory substrate) under very high supersaturation. The
low nucleation rates lead to depositional growth of large iron pebbles on a sparse population of nucleated iron nano-particles.
Silicates in the form of iron-free MgSiO3 nucleate at similar temperatures but obtain smaller sizes due to the much higher
number of nucleated particles. This results in a chemical separation of large iron particles from silicate particles with ten
times lower Stokes numbers. We propose that such conditions lead to the formation of iron-rich planetesimals by the streaming
instability. In this view, Mercury formed by accretion of iron-rich planetesimals with a sub-solar abundance of highly reduced
silicate material. Our results imply that the iron-rich planets known to orbit the Sun and other stars are not required to haveexperienced mantle-stripping impacts. Instead their formation could be a direct consequence of temperature fluctuations in
protoplanetary discs and chemical separation of distinct crystal species through the ensuing nucleation process.

927. Precursors of fatty alcohols in the ISM: Discovery of n-propanol

Izaskun Jimenez-Serra, Lucas F. Rodriguez-Almeida, Jesus Martin-Pintado, Victor M. Rivilla, Mattia Melosso,
Shaoshan Zeng, Laura Colzi, Yoshiyuki Kawashima, Eizi Hirota, Cristina Puzzarini, Belen Tercero, Pablo deVicente, Fernando Rico-Villas, Miguel A. Requena-Torres, Sergio Martin F Theories on the origins of life proposethat early cell membranes were synthesized from amphiphilic molecules simpler than phospholipids such as fatty alcohols. The
discovery in the interstellar medium (ISM) of ethanolamine, the simplest phospholipid head group, raises the question whether
simple amphiphilic molecules are also synthesized in space. We investigate whether precursors of fatty alcohols are present in
the ISM. For this, we have carried out a spectral survey at 7, 3, 2 and 1 mm toward the Giant Molecular Cloud G+0.6930.027 located in the Galactic Center using the IRAM 30m and Yebes 40m telescopes. Here, we report the detection in the
ISM of the primary alcohol n-propanol (in both conformers Ga-n-C3H7OH and Aa-n-C3H7OH), a precursor of fatty alcohols.
The derived column densities of n-propanol are (5.5±0.4)×1013 cm−2 for the Ga conformer and (3.4+-0.3)×1013 cm−2 for the
Aa conformer, which imply molecular abundances of (4.1+-0.3)x10− 10 for Ga-n-C3H7OH and of (2.5+-0.2)x10−10 for Aa-nC3H7OH. We also searched for the AGa conformer of n-butanol (AGa-n-C4H9OH) without success yielding an upper limit to
its abundance of <4.1x10−11 . The inferred CH3OH:C2H5OH:C3H7OH:C4H9OH abundance ratios go as 1:0.04:0.006:<0.0004
toward G+0.693-0.027, i.e. they decrease roughly by one order of magnitude for increasing complexity. We also report thedetection of both syn and anti conformers of vinyl alcohol, with column densities of (1.11+-0.08)x1014 cm−2 and (1.3±0.4)x1013
cm−2 , and abundances of (8.2+-0.6)x10−10 and (9.6±3.0)x10−11 , respectively. The detection of n-propanol, together with therecent discovery of ethanolamine in the ISM, opens the possibility that precursors of lipids according to theories of the originof life, could have been brought to Earth from outer space.

28. Nearby Young Stars and Young Moving Groups

Joel H. Kastner, David A. Principe F The past two decades have seen dramatic progress in our knowledge of the populationof stars of age .150 Myr that lie within ∼100 pc of the Sun. Most such stars are found in loose kinematic groups ("nearby young
moving groups"; NYMGs). The proximity of NYMGs and their members facilitates studies of the X-ray properties of coevalgroups of pre-main sequence (pre-MS) stars as well as of individual pre-MS systems. In this review, we focus on how NYMG
X-ray studies provide unique insight into the early evolution of stellar magnetic activity, the X-ray signatures of accretion, andthe irradiation and dissipation of protoplanetary disks by high-energy photons originating with their host pre-MS stars. We
discuss the likely impacts of the next generation of X-ray observing facilities on these aspects of the study of NYMGs and theirmembers.

Influence of the magnetic field on the formation of protostellar disks

29. N. S. Kargaltseva, S. A. Khaibrakhmanov, A. E. Dudorov, S. N. Zamozdra, A. G. Zhilkin F We numericallymodel the collapse of magnetic rotating protostellar clouds with mass of 10 Msun . The simulations are carried out with the helpof 2D MHD code Enlil. The structure of the cloud at the isothermal stage of the collapse is investigated for the cases of weak,moderate, and strong initial magnetic field. Simulations reveal the universal hierarchical structure of collapsing protostellar
clouds, consisting of flattened envelope with the qausi-magnetostatc disk inside and the first core in its center. The size of the
primary disk increases with the initial magnetic energy of the cloud. The magnetic braking efficiently transports the angularmomentum from the primary disk into the envelope in the case, when initial magnetic energy of the cloud is more than 20%
of its gravitational energy. Intensity of the outflows launched from the region near the boundary of the first core increases
with initial magnetic energy. The ‘dead’ zone with small ionization fraction, x < 10−11 , forms inside the first hydrostatic core
and at the base of the outflow. Ohmic dissipation and ambipolar diffusion determine conditions for further formation of the
protostellar disk in this region.

30. A Gaia view on the star formation in the Monoceros OB1 and R1 associations

Beomdu Lim, Yael Naze, Jongsuk Hong, Sung-yong Yoon, Jinhee Lee, Narae Hwang, Byeong-Gon Park, JeongEun Lee F Stellar kinematics provides the key to understanding star formation process. In this respect, we present a kinematic
study of the Monoceros OB1 (Mon OB1) and R1 (Mon R1) associations using the recent Gaia data and radial velocities ofstars derived from high-resolution spectroscopy and the literature. A total of 728 members are selected using the criteria basedon the intrinsic properties of young stars, parallaxes, and proper motions. The spatial distribution and kinematic properties ofmembers show that these associations have distinct substructures. In Mon OB1, we find one northern group and two southerngroups. Mon R1 is composed of three small stellar groups that are spatially and kinematically distinct. Some stars are found ina halo around these two associations. We detect patterns of expansion for most stellar groups in the associations. In addition,
two stellar groups in Mon OB1 show the signature of rotation, which provides an important constraint on cluster formation.
The star formation history of Mon OB1 is slightly revised. Star formation first occurred in the southern region and subsequently
in the northern region. Recent star-forming events ignited deeper into the southern region, while some stars are escaping fromMon OB1, forming a halo. Mon R1 might have formed at the same epoch as the formation of the northern group in Mon OB1.
Given that star formation is taking place on different scales along a large arc-like structure, Mon OB1 and Mon R1 may be the10results of hierarchical star formation.

31. ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): How do dense coreproperties affect the multiplicity of protostars?

Qiuyi Luo, Tie Liu, Kenichi Tatematsu, ShengYuan Liu, Pak Shing Li, James di Francesco, Doug Johnstone,
Paul F. Goldsmith, Somnath Dutta, Naomi Hirano, ChinFei Lee, Di Li, KeeTae Kim, Chang Won Lee, JeongEun
Lee, Xunchuan Liu, Mika Juvela, Jinhua He, ShengLi Qin, HongLi Liu, David Eden, Woojin Kwon, Dipen Sahu,
Shanghuo Li, FengWei Xu, Siju Zhang, ShihYing Hsu, Leonardo Bronfman, Patricio Sanhueza, VeliMatti
Pelkonen, Jianwen Zhou, Rong Liu, Qilao Gu, Yuefang Wu, Xiaofeng Mai, Edith Falgarone, ZhiQiang Shen F
During the transition phase from prestellar to protostellar cloud core, one or several protostars can form within a single gascore. The detailed physical processes of this transition, however, still remain unclear. We present 1.3 mm dust continuum andmolecular line observations with the Atacama Large Millimeter/submillimeter Array (ALMA) toward 43 protostellar cores in
the Orion molecular cloud complex (λOrionis, Orion B, and Orion A) with an angular resolution of ∼ 0.35 (∼ 140 au). In
total, we detect 13 binary/multiple systems. We derive an overall multiplicity frequency (MF) of 28% ± 4% and a companion
star fraction (CSF) of 51% ± 6%, over a separation range of 300-8900 au. The median separation of companions is about2100 au. The occurrence of stellar multiplicity may depend on the physical characteristics of the dense cores. Notably, thosecontaining binary/multiple systems tend to show higher gas density and Mach number than cores forming single stars. The
integral-shaped filament (ISF) of Orion A GMC, which has the highest gas density and hosts high-mass star formation in its
central region (Orion Nebula Cluster or ONC), shows the highest MF and CSF among Orion GMCs. In contrast, the λ Orionis
Giant Molecular Cloud (GMC) has a lower MF and CSF than the Orion B and Orion A GMCs, indicating that feedback
from Hii regions may suppress the formation of multiple systems. We also find that the protostars comprising binary/multiple
systems are usually at different evolutionary stages.

MCN-a: a disk accreting massive protostar embedded in an early-phase hot
32. W49N
molecular core
Ryosuke Miyawaki, Masahiko Hayashi, Tetsuo Hasegawa F We present ALMA archival data for 219-235 GHz continuum
and line observations toward the hot molecular core (HMC) W49N MCN-a (UCHII region J1) at a resolution of 0."3. The dust
continuum emission, showing an elongated structure of 1."40x0."95 (PA=43.5deg) perpendicular to the outflow seen in SiO andSO, represents a rotating flattened envelope, or torus, with a radius of 7,800au inclined at 47.5deg or larger. The emissions from
CH3CN and 11 molecular lines exhibit a consistent velocity gradient as a result of rotation. The magnitude of each velocity
gradient is different, reflecting that each line samples a specific radial region. This allows us to derive a rotation curve as Vrot
prop R0.44+−0.11 for 2,400au < R < 14,000au, giving the dynamical mass as Mdyn = 57.0+24.5-17.1 (R [au]/3, 000)1.88 Msun.
The envelope mass independently estimated from the dustemission is 910Msun (for Tdust =180K) for R<7,800au and 32Msun(for Tdust=300K) for R<1,700 au. The dynamical mass formula agrees well with these mass estimates within an uncertainty
of a factor of three in the latter. The envelope is self-gravitating and is unstable to form spiral arms and fragments, allowing
rapid accretion to the inner radii with a rate of order 10−2 Msun yr−1 , although inward motion was not detected. The envelope
may become a non self-gravitating Keplerian disk at R<(300-1,000) au. The formula is also consistent with the total mass
104 Msun of the entire HMC 0.15 pc (31,000 au) in radius. Multiple transitions of CH3CN, HNCO and CH3OH provide therotation temperatures, suggesting that the central source of MCN-a has an intrinsic bolometric luminosity of 106 Lsun. These
results have revealed the structure and kinematics of MCN-a at its intermediate radii. With no broad-line H30alpha emission
detected, MCN-a may be in the earliest phase of massive star formation.

33. A model grid for the reflected light from transition disksJ. Ma, H. M. Schmid F The dust in protoplanetary disks is an important ingredient in planet formation and can beinvestigated with model simulations and quantitative imaging polarimetry of the scattered stellar light. This study explores
circumstellar disks with calculations for the intensity and polarization of the reflected light. The photon scattering and absorption
by the disk are calculated with a Monte Carlo method for a grid of simple, rotationally symmetric models approximated ateach point by a plane-parallel dusty atmosphere. The results of our simple disk models reproduce well the measurements forthe intensity I/I? , azimuthal polarization Qϕ /I? , and fractional polarization pϕ reported for well-observed transition disks.
They describe the dependencies of the scattered radiation on the disk geometry and the dust scattering parameters in detail.
Particularly strong constraints on disk properties can be obtained from certain diagnostic quantities. Therefore, they can beused as a diagnostic tool for the analysis of quantitative measurements, specifically in constraining or even determining thescattering properties of the dust particles in disks. Collecting and comparing such information for many systems is required tounderstand the nature of the scattering dust in planet-forming disks.

11

1 under the light of Gaia EDR3: Distance, isolation, extent, and a hidden
34. Westerlund
population
Ignacio Negueruela, Emilio J. Alfaro, Ricardo Dorda, Amparo Marco, Jesús Maíz Apellániz, Carlos GonzálezFernández F (Abridged) We have used Gaia EDR3 data, together with spectra of a large sample of luminous stars in the fieldsurrounding Westerlund 1, to explore the extent of the cluster. We carry out a non-parametric analysis of proper motions andmembership determination. We investigate the reddening and proper motions of several dozen OB stars and red supergiants <1 deg away from Wd 1. We identify a population of kinematic members of Wd 1 that largely includes the known spectroscopic
members. From their EDR3 parallaxes, we derive a distance to the cluster of 4.23+0.23−0.21 kpc. Extinction in this direction increases
by a large amount around 2.8 kpc, due to dark clouds associated to the Scutum-Crux arm. As a consequence, we hardly see anystars at distances comparable to that of the cluster. The proper motions of Wd 1, however, are very similar to those of stars in
the field surrounding it, but distinct. We find a second, astrometrically well-defined population in the foreground (d ≈ 2 kpc),
likely connected to the possible open cluster BH197. Wd 1 is very elongated, an effect not driven by the very heavy extinction
to the East and South. We find a low-density halo extending up to 10’ from the cluster centre, mainly in the NW quadrant. A
few OB stars at larger distances from the cluster, most notably the LBV MN48, share its proper motions, suggesting that Wd 1
has little or no peculiar motion with respect to the field population of the Norma arm. However, we are unable to find any red
supergiant that could belong to an extended population related to the cluster, although we observe several dozen such objects inthe foreground. We find a substantial population of luminous OB members obscured by several more magnitudes of extinction
than most known members. These objects, mostly located in the central region of the cluster, increase the population of OB
supergiants by about 25

35. ALMA constraints on assembly of Core Accretion planets

Sergei Nayakshin, Vardan Elbakyan, Giovanni Rosotti F Resolved dust continuum and CO line ALMA imaging, andin some cases detection of Hα emission, hint that young massive planets are abundant at wide separations in protoplanetary
discs. Here, we show how these observations can probe the runaway phase of planetary growth in the Core Accretion theory.
Planets in this phase have the right range of masses to account for the predominantly moderate contrast gaps and rings seen
in ALMA observations. However, we find that these planets gain mass and migrate inward very rapidly. As a result, the phasewhen they could produce gaps with properties similar to those observed is very short, i.e., tgap . 0.1 Myr, independently ofthe disc viscosity parameter. This would require many tens to hundreds of gas giant planets to be born per ALMA system,
violating the available mass budget of solids in realistic discs. This also predicts preponderance of discs with very wide gaps
or complete inner disc holes, which is not observed. We show that suppression of both planet accretion and migration by afactor of at least ten is a possible solution to these serious problems. Future population synthesis models of planet formation
should aim to address both exoplanetary data of older discless planetary systems and ALMA discs with embedded planets in
one framework.

Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR3 II: Hier36. 3Darchical Star Formation Revealed by Spatial and Kinematic Substructures
Xiaoying Pang, Shih-Yun Tang, Yuqian Li, Zeqiu Yu, Long Wang, Jiayu Li, Yezhang Li, Yifan Wang, Yanshu
Wang, Teng Zhang, Mario Pasquato, M. B. N. Kouwenhoven F We identify members of 65 open clusters in thesolar neighborhood using the machine-learning algorithm StarGO based on Gaia EDR3 data. After adding members of twenty
clusters from previous studies (Pang et al. 2021a,b; Li et al. 2021) we obtain 85 clusters, and study their morphology andkinematics. We classify the substructures outside the tidal radius into four categories: filamentary (f1) and fractal (f2) for
clusters < 100 Myr, and halo (h) and tidal-tail (t) for clusters > 100 Myr. The kinematical substructures of f1-type clusters areelongated; these resemble the disrupted cluster Group X. Kinematic tails are distinct in t-type clusters, especially Pleiades. We
identify 29 hierarchical groups in four young regions (Alessi 20, IC 348, LP 2373, LP 2442); ten among these are new. The hierarchical groups form filament networks. Two regions (Alessi 20, LP 2373) exhibit global "orthogonal" expansion (stellar motion
perpendicular to the filament), which might cause complete dispersal. Infalling-like flows (stellar motion along the filament)
are found in UBC 31 and related hierarchical groups in the IC 348 region. Stellar groups in the LP 2442 region (LP 2442 gp
1-5) are spatially well-mixed but kinematically coherent. A merging process might be ongoing in the LP 2442 subgroups. For
younger systems (. 30 Myr), the mean axis ratio, cluster mass and half-mass radius tend to increase with age values. These
correlations between structural parameters may imply two dynamical processes occurring in the hierarchical formation scenario
in young stellar groups: (1) filament dissolution and (2) sub-group mergers.

37. Wide-angle protostellar outflows driven by narrow jets in stratified cores

M. Rabenanahary, S. Cabrit, Z. Meliani, G. Pineau des Forêts F Most simulations of outflow feedback on starformation are based on the assumption that outflows are driven by a wide angle "X-wind," rather than a narrow jet. However,
the arguments initially raised against pure jet-driven flows were based on steady ejection in a uniform medium, a notion thatis no longer supported based on recent observations. We aim to determine whether a pulsed narrow jet launched in a density-

12

stratified, self-gravitating core could reproduce typical molecular outflow properties, without the help of a wide-angle windcomponent. We performed axisymmetric hydrodynamic simulations using the MPI-AMRVAC code with optically thin radiative
cooling on timescales up to 10000 yrs. Then we computed and compared the predicted properties with observational data.
First, the jet-driven shell expands faster and wider through a core with steeply decreasing density than through an uniform
core. Second, when blown into the same singular flattened core, a jet-driven shell has a similar width as a wide-angle winddriven shell in the first few hundred years, but a decelerating expansion on long timescales. The flow adopts a conical shapeand a base opening angle reaching up to 90 deg. Third, after ∼ 10000 yrs, a pulsed jet-driven shell shows fitting features anda qualitative resemblance with recent observations of protostellar outflows with the Atacama Large Millimeter Array (ALMA),
such as HH46-47 and CARMA-7. In particular, similarities are seen in the shell widths, opening angles, position-velocity
diagrams, and mass-velocity distribution, with some showing a closer resemblance than in simulations based on a wide-angle"X-wind" model. Therefore, a realistic ambient density stratification in addition to millenia-long integration times are equally
essential to reliably predict the properties of outflows driven by a pulsed jet and to confront them with the observations.

Ori Stars Eclipses by Large-Scale Disc Perturbations
38. UX
S. G. Shulman, V. P. Grinin F We simulate the polarized radiative transfer in vicinities of the UX Ori type stars during theirminima. Our model of an eclipse by an extended disc perturbation generalizes the compact gas-dust cloud eclipse model. We
apply the radiative transfer method based on enumeration using the directions grid to model the influence of the perturbation
extensions along azimuth and radius on the eclipse depth and parameters of the linear polarization. We investigate eclipses
both for the flared disc and for the disc with a puffing-up in the dust sublimation zone. The puffing-up is obtained by adding
a disc wind to the model. Comparison with a compact cloud eclipse model reveals that the eclipse by a large-scale azimuthally
extended perturbation may be significantly deeper and show a greater linear polarization degree. We also demonstrate thatthe perturbation extension together with the disc puffing-up can strongly affect the degree of polarization and colour index of
the star during the eclipse. The position angle of the linear polarization may also change markedly during and after an eclipse
by a large scale perturbation for the model with a puffed-up inner rim. Also, in this model, the maximum degree of the linear
polarization can be achieved not at the brightness minimum but closer to the end of the eclipse. We discuss the modelling
results in the context of the photopolarimetric observations of UX Ori stars.

the accuracy of HI observations in molecular clouds – More cold HI than thought?
39. OnD. Seifried, H. Beuther, S. Walch, J. Syed, J. D. Soler, P. Girichidis, R. Wünsch F We present a study of the cold
atomic hydrogen (HI) content of molecular clouds simulated within the SILCC-Zoom project. We produce synthetic observationsof HI at 21 cm including HI self-absorption (HISA) and observational effects. We find that HI column densities, NHI , of &1022
cm−2 are frequently reached in molecular clouds with HI temperatures as low as ∼10 K. Hence, HISA observations assuming
a fixed HI temperature tend to underestimate the amount of cold HI in molecular clouds by a factor of 3 - 10 and produce
an artificial upper limit of NHI around 1021 cm−2 . We thus argue that the cold HI mass in clouds could be a factor of afew higher than previously estimated. Also NHI -PDFs obtained from HISA observations might be subject to observationalbiases and should be considered with caution. The underestimation of cold HI in HISA observations is due to both the large
HI temperature variations and the effect of noise in regions of high optical depth. We find optical depths of cold HI around1 - 10 making optical depth corrections essential. We show that the high HI column densities (&1022 cm−2 ) can in parts
be attributed to the occurrence of up to 10 individual HI-H2 transitions along the line of sight. This is also reflected in the
spectra, necessitating Gaussian decomposition algorithms for their analysis. However, also for a single HI-H2 transition, NHI
frequently exceeds 1021 cm−2 , challenging 1D, semi-analytical models. This is due to non-equilibrium chemistry effects andthe fact that HI-H2 transition regions usually do not possess a 1-dimensional geometry. Finally, we show that the HI gas ismoderately supersonic with Mach numbers of a few. The corresponding non-thermal velocity dispersion can be determined via
HISA observations within a factor of ∼2.

40. Gas and Dust Shadows in the TW Hydrae Disk

Richard Teague, Jaehan Bae, Myriam Benisty, Sean M. Andrews, Stefano Facchini, Jane Huang, David Wilner
F We present new observations of CO J=2-1 emission from the protoplanetary disk around TW Hya. Emission is detected
out to 240 au (4") and found to exhibit azimuthal variations up to 20% beyond 180 au (3"), with the west side of the disk
brighter than the east. This asymmetry is interpreted as tracing the shadow previously seen in scattered light. A reanalysis of
the multi-epoch observations of the dust shadow in scattered light from Debes et al. (2017) suggests that an oscillatory motion
would provide a better model of the temporal evolution of the dust shadow rather than orbital motion. Both models predictan angular offset between the dust shadow and the gas shadow of up to 100 deg. We attribute this offset to the finite rate
at which dust grains and gas molecules can exchange heat, dominated by the collisional rate between gas molecules and dust
grains, tcoll . The angular offsets derived are equivalent to collisional timescales that range from the near instantaneous up totcoll 10 years, depending on whether a straight or a curved dust shadow, as suggested by HST observations reported by Debeset al. (2017), is adopted. The inferred range of tcoll are consistent with those predictions based on representative gas densities,

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temperatures, gas-to-dust ratios and grain sizes. These results represent the first time empirical constraints can be placed on
tcoll .

Vibrationally-excited Lines of HC3 N Associated with the Molecular Disk around the

41. G24.78+0.08 A1 Hyper-compact HII Region

Kotomi Taniguchi, Kei E. I. Tanaka, Yichen Zhang, Rubén Fedriani, Jonathan C. Tan, Shigehisa Takakuwa,
Fumitaka Nakamura, Masao Saito, Liton Majumdar, Eric Herbst F We have analyzed Atacama Large Millimeter/submillimeter Array Band 6 data of the hyper-compact HII region G24.78+0.08 A1 (G24 HC HII ) and report the detectionof vibrationally-excited lines of HC3 N (v7 = 2, J = 24 − 23). The spatial distribution and kinematics of a vibrationally-excitedline of HC3 N (v7 = 2, J = 24 − 23, l = 2e) are found to be similar to the CH3 CN vibrationally-excited line (v8 = 1), whichindicates that the HC3 N emission is tracing the disk around the G24 HC HII region previously identified by the CH3 CN lines.
We derive the 13 CH3 CN/HC13 CCN abundance ratios around G24 and compare them to the CH3 CN/HC3 N abundance ratios
in disks around Herbig Ae and T Tauri stars. The 13 CH3 CN/HC13 CCN ratios around G24 (∼ 3.0 − 3.5) are higher than the
CH3 CN/HC3 N ratios in the other disks (∼ 0.03 − 0.11) by more than one order of magnitude. The higher CH3 CN/HC3 N ratios
around G24 suggest that the thermal desorption of CH3 CN in the hot dense gas and efficient destruction of HC3 N in the region
irradiated by the strong UV radiation are occurring. Our results indicate that the vibrationally-excited HC3 N lines can beused as a disk tracer of massive protostars at the HC HII region stage, and the combination of these nitrile species will provide
information of not only chemistry but also physical conditions of the disk structures.

Massive compact dust disk with a gap around CW Tau revealed by ALMA multi-band

42. observations

Takahiro Ueda, Akimasa Kataoka, Takashi Tsukagoshi F Compact protoplanetary disks with a radius of . 50 au arecommon around young low-mass stars. We report high resolution ALMA dust continuum observations toward a compact disk
around CW Tau at Band 4 (λ = 2.2 mm), 6 (1.3 mm), 7 (0.89 mm) and 8 (0.75 mm). The SED shows the spectral slope of
2.0 ± 0.24 between 0.75 and 1.3 mm, while it is 3.7 ± 0.29 between 2.17 and 3.56 mm. The steep slope between 2.17 and 3.56 mm
is consistent with that of optically thin emission from small grains (. 350 µm). We perform parametric fitting of the ALMA
data to characterize the dust disk. Interestingly, if the dust-to-gas mass ratio is 0.01, the Toomre’s Q parameter reaches ∼ 1-3,
suggesting that the CW Tau disk might be marginally gravitationally unstable. The total dust mass is estimated as ∼ 250M⊕
for the maximum dust size of 140 µm that is inferred from the previous Band 7 polarimetric observation and at least 80M⊕
even for larger grain sizes. This result shows that the CW Tau disk is quite massive in spite of its smallness. Furthermore,
we clearly identify a gap structure located at ∼ 20 au, which might be induced by a giant planet. In spite of these interesting
characteristics, the CW Tau disk has normal disk luminosity, size and spectral index at ALMA Band 6, which could be a clue
to the mass budget problem in Class II disks.

43. A highly settled disk around Oph 163131

M. Villenave, K. R. Stapelfeldt, G. Duchene, F. Menard, M. Lambrechts, A. Sierra, C. Flores, W. R. F. Dent,
S. Wolff, A. Ribas, M. Benisty, N. Cuello, C. Pinte F High dust density in the midplane of protoplanetary disks isfavorable for efficient grain growth and can allow fast formation of planetesimals and planets, before disks dissipate. Verticalsettling and dust trapping in pressure maxima are two mechanisms allowing dust to concentrate in geometrically thin andhigh density regions. In this work, we aim to study these mechanisms in the highly inclined protoplanetary disk SSTC2D
J163131.2-242627 (Oph163131, i 84deg). We present new high angular resolution continuum and 12CO ALMA observations of
Oph163131. The gas emission appears significantly more extended in the vertical and radial direction compared to the dust
emission, consistent with vertical settling and possibly radial drift. In addition, the new continuum observations reveal two
clear rings. The outer ring, located at 100 au, is well resolved in the observations, which allows us to put stringent constraints
on the vertical extent of millimeter dust particles. We model the disk using radiative transfer and find that the scale height ofmillimeter sized grains is 0.5au or less at 100au from the central star. This value is about one order of magnitude smaller than
the scale height of smaller micron-sized dust grains constrained by previous modeling, which implies that efficient settling of thelarge grains is occurring in the disk. When adopting a parametric dust settling prescription, we find that the observations are
consistent with a turbulent viscosity coefficient of about alpha≤10−5 at 100au. Finally, we find that the thin dust scale heightmeasured in Oph163131 is favorable for planetary growth by pebble accretion: a 10 MEarth planet may grow within less than
10 Myr, even in orbits exceeding 50au.

44. ALMA Discovery of a Disk around the Planetary-mass Companion SR 12 c

Ya-Lin Wu, Brendan P. Bowler, Patrick D. Sheehan, Laird M. Close, Joshua A. Eisner, William M. J. Best,
Kimberly Ward-Duong, Zhaohuan Zhu, Adam L. Kraus F We report an Atacama Large Millimeter/submillimeter
Array 0.88 mm (Band 7) continuum detection of the accretion disk around SR 12 c, an ∼11 MJup planetary-mass companion

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(PMC) orbiting its host binary at 980 au. This is the first submillimeter detection of a circumplanetary disk around a wide
PMC. The disk has a flux density of 127 ± 14 µJy and is not resolved by the ∼0.1" beam, so the dust disk radius is likely lessthan 5 au and can be much smaller if the dust continuum is optically thick. If, however, the dust emission is optically thin,then the SR 12 c disk has a comparable dust mass to the circumplanetary disk around PDS 70 c but is about five times lower
than that of the ∼12 MJup free-floating OTS 44. This suggests that disks around bound and unbound planetary-mass objects
can span a wide range of masses. The gas mass estimated with an accretion rate of 10−11 M yr−1 implies a gas-to-dust ratio
higher than 100. If cloud absorption is not significant, a nondetection of 12 CO(3-2) implies a compact gas disk around SR 12
c. Future sensitive observations may detect more PMC disks at 0.88 mm flux densities of .100 µJy.

of the SDC13 Hub-Filament System: A Cloud-Cloud Collision Imprinted on
45. Formation
The Multiscale Magnetic Field
Jia-Wei Wang, Patrick M. Koch, Ya-Wen Tang, Gary A. Fuller, Nicolas Peretto, Gwenllian M. Williams, HsiWei Yen, Han-Tsung Lee, Wei-An Chen F Hub-filament systems (HFSs) are potential sites of protocluster and massive
star formation, and play a key role in mass accumulation. We report JCMT POL-2 850 µm polarization observations toward
the massive HFS SDC13. We detect an organized magnetic field near the hub center with a cloud-scale "U-shape" morphology
following the western edge of the hub. Together with larger-scale APEX 13CO and PLANCK polarization data, we find that
SDC13 is located at the convergent point of three giant molecular clouds (GMCs) along a large-scale, partially spiral-likemagnetic field. The smaller "U-shape" magnetic field is perpendicular to the large-scale magnetic field and the converging
GMCs. We explain this as the result of a cloud-cloud collision. Within SDC13, we find that local gravity and velocity gradients
point toward filament ridges and hub center. This suggests that gas can locally be pulled onto filaments and overall converges
to the hub center. A virial analysis of the central hub shows that gravity dominates magnetic and kinematic energy. Combining
large- and small-scale analyses, we propose that SDC13 is initially formed from a collision of clouds moving along the large-scale
magnetic field. In the post-shock regions, after the initial turbulent energy has dissipated, gravity takes over and starts to drive
the gas accretion along the filaments toward the hub center.

Architecture of planetary systems predicted from protoplanetary disks observed with

46. ALMA II: evolution outcomes and dynamical stability

Shijie Wang, Kazuhiro D. Kanagawa, Yasushi Suto F Recent ALMA observations on disk substructures suggest thepresence of embedded protoplanets in a large number disks. The primordial configurations of these planetary systems can be
deduced from the morphology of the disk substructure and serve as initial conditions for numerical investigation of their future
evolution. Starting from the initial configurations of 12 multi-planetary systems deduced from ALMA disks, we carried out
two-stage N-body simulation to investigate the evolution of the planetary systems at the disk stage as well as the long term
orbital stability after the disk dispersal. At the disk stage, our simulation includes both the orbital migration and pebble/gas
accretion effects. We found a variety of planetary systems are produced and can be categorised into distant giant planets,
Jupiter-like planets, Neptune-like planets and distant small planets. We found the disk stage evolution as well as the final
configurations are sensitive to both the initial mass assignments and viscosity. After the disk stage, we implement only mutual
gravity between star and planets and introduce stochastic perturbative forces. All systems are integrated for up to 10 Gyr
to test their orbital stability. Most planetary systems are found to be stable for at least 10 Gyr with perturbative force in areasonable range. Our result implies that a strong perturbation source such as stellar flybys is required to drive the planetarysystem unstable. We discuss the implications of our results on both the disk and planet observation, which may be confirmedby the next generation telescopes such as JWST and ngVLA.

population of compact radio sources in M 17
47. TheVanessa Yanza, Josep M. Masqué, Sergio A. Dzib, Luis F. Rodríguez, S. -N. X. Medina, Stan Kurtz, Laurent
Loinard, Miguel A. Trinidad, Karl M. Menten, Carlos A. Rodríguez-Rico F We present a catalog of radio sources ofthe M 17 region based on deep X band radio observations centered at 10 GHz obtained with the Jansky Very Large Array in the
A configuration. We detect a total of 194 radio sources, 12 of them extended and 182 compact. We find that a significant fraction(at least 40% in our catalog) have suspected gyrosynchrotron emission associated with stellar coronal emission. By comparing
the radio luminosities of our sources with their X ray counterparts, when available, we find that they are underluminous in
X rays with respect to the Güdel Benz relation, but a correlation with a similar slope is obtained provided that only sources
with evident non thermal nature are selected from the sample compiled for the Orion Nebula Cluster (ONC) and M 17. The
comparison of M 17 with the ONC and NGC 6334D-F leads to a similar luminosity function for the three regions, at least forthe more luminous sources. However, the radio sources in M 17 are three times more numerous compared to the other regions at
a given luminosity and their spatial distribution differs from that of Orion. Moreover, an arc-shaped structure of 40” in extent
is observed in our map, identified previously as an ionizing front, with the cometary Hyper Compact source UC1 at its focus.
Archival 1 mm ALMA data reveals compact emission coincident with the radio wavelength peak, possibly associated with aprotostellar disk of the massive star exciting UC1.

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