The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 360 — 31 December 2022
Editor: João Alveswww.starformation.news

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Cover image caption
Artstics impression of EX Lupi by Ruth Jarman and Joe Gerhardt (Semiconductor). This image is part of Spectral Constellations a series of generative animations, driven by scientific data of young stars. Credits: Semiconductor. Spectral Constellations
was commissioned through a residency with the Planet Disk Connection group, STFC, and DJCAD at the University of
Dundee, Scotland.

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 thearXiv or the SFN.

Abstracts
1. Discovery of interstellar NC4NH+: dicyanopolyynes are indeed abundant in space
M. Agundez, C. Cabezas, N. Marcelino, R. Fuentetaja, B. Tercero, P. de Vicente, J. Cernicharo F The previous

detection of two species related to the non polar molecule cyanogen (NCCN), its protonated form (NCCNH+) andone metastable isomer (CNCN), in cold dense clouds supported the hypothesis that dicyanopolyynes are abundant inspace. Here we report the first identification in space of NC4NH+, which is the protonated form of NC4N, the second
member of the series of dicyanopolyynes after NCCN. The detection was based on the observation of six harmonicallyrelated lines within the Yebes 40m line survey of TMC-1 QUIJOTE. The six lines can be fitted to a rotational constantB = 1293.90840 +/- 0.00060 MHz and a centrifugal distortion constant D = 28.59 +/- 1.21 Hz. We confidently assign
this series of lines to NC4NH+ based on high-level ab initio calculations, which supports the previous identificationof HC5NH+ by Marcelino et al. (2020) from the observation of a series of lines with a rotational constant 2 MHz
lower than that derived here. The column density of NC4NH+ in TMC-1 is (1.1 +1.4 -0.6)e10 cm-2, which implies
that NC4NH+ is eight times less abundant than NCCNH+. The species CNCN, previously reported toward L483 andtentatively in TMC-1, is confirmed in this latter source. We estimate that NCCN and NC4N are present in TMC-1
with abundances a few times to one order of magnitude lower than HC3N and HC5N, respectively. This means thatdicyanopolyynes NC-(CC)n-CN are present at a lower level than the corresponding monocyanopolyynes HCC-(CC)nCN. The reactions of the radicals CN and C3N with HNC arise as the most likely formation pathways to NCCN and
NC4N in cold dense clouds.

2. On the Number of Stars in the Sun’s Birth Cluster

Sota Arakawa, Eiichiro Kokubo F The Sun is thought to be formed within a star cluster. The coexistence of 26 Al-richand 26 Al-poor calcium–aluminum-rich inclusions indicates that a direct injection of 26 Al-rich materials from a nearby
core-collapse supernova should occur in the first 105 years of the solar system. Therefore, at least one core-collapse
supernova should occur within the duration of star formation in the Sun’s birth cluster. Here we revisit the numberof stars in the Sun’s birth cluster from the point of view of the probability for acquiring at least one core-collapse
supernova within the finite duration of star formation in the birth cluster. We find that the number of stars in thebirth cluster can be significantly larger than that previously considered, depending on the duration of star formation.

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3. Time-dependent Monte Carlo continuum radiative transfer
A. Bensberg, S. Wolf F Aims.

We present an implementation of an algorithm for 3D time-dependent Monte
Carlo radiative transfer. It allows one to simulate temperature distributions as well as images and spectral energy
distributions of the scattered light and thermal reemission radiation for variable illuminating and heating sources
embedded in dust distributions, such as circumstellar disks and dust shells on time scales up to weeks. Methods.
We extended the publicly available 3D Monte Carlo radiative transfer code POLARIS with efficient methods forthe simulation of temperature distributions, scattering, and thermal reemission of dust distributions illuminated bytemporally variable radiation sources. The influence of the chosen temporal step width and the number of photon
packages per time step as key parameters for a given configuration is shown by simulating the temperature distribution
in a spherical envelope around an embedded central star. The effect of the optical depth on the temperature simulation
is discussed for the spherical envelope as well as for a model of a circumstellar disk with an embedded star. Finally,
we present simulations of an outburst of a star surrounded by a circumstellar disk. Results. The presented algorithm
for time-dependent 3D continuum Monte Carlo radiative transfer is a valuable basis for preparatory studies as well as
for the analysis of continuum observations of the dusty environment around variable sources, such as accreting youngstellar objects. In particular, the combined study of light echos in the optical and near-infrared wavelength range
and the corresponding time-dependent thermal reemission observables of variable, for example outbursting sources,
becomes possible on all involved spatial scales.

modeling of Orion Nebula Cluster disks: evidence for massive, compact gas
4. Chemicaldisks with ISM-like gas-to-dust ratios
Ryan D. Boyden, Josh A. Eisner F The stellar cluster environment is expected to play a central role in the evolutionof circumstellar disks. We use thermochemical modeling to constrain the dust and gas masses, disk sizes, UV and X-ray
radiation fields, viewing geometries, and central stellar masses of 20 Class II disks in the Orion Nebula Cluster (ONC).
We fit a large grid of disk models to 350 GHz continuum, CO J = 3 − 2, and HCO+ J = 4 − 3 ALMA observations ofeach target, and we introduce a procedure for modeling interferometric observations of gas disks detected in absorption
against a bright molecular cloud background. We find that the ONC disks are massive and compact, with typical radii< 100 AU, gas masses ≥ 10−3 M , and gas-to-dust ratios ≥ 100. The ISM-like gas-to-dust ratios derived from ourmodeling suggest that compact, externally-irradiated disks in the ONC are less prone to gas-phase CO depletion thanthe massive and extended gas disks that are commonly found in nearby low-mass star-forming regions. The presenceof massive gas disks indicates that external photoevaporation may have only recently begun operating in the ONC,
though it remains unclear whether other cluster members are older and more evaporated than the ones in our sample.
Finally, we compare our dynamically-derived stellar masses with the stellar masses predicted from evolutionary models
and find excellent agreement. Our study has significantly increased the number of dynamical mass measurements inthe mass range ≤ 0.5 M , demonstrating that the ONC is an ideal region for obtaining large samples of dynamical
mass measurements towards low-mass M-dwarfs.

5. The Star Formation History of the Milky Way’s Nuclear Star Cluster
Zhuo Chen, Tuan Do, Andrea M. Ghez, Matthew Hosek Jr., Anja Feldmeier-Krause, Devin Chu, Rory Bentley,
Jessica R. Lu, Mark R. Morris F We report the first star formation history study of the Milky Way’s nuclear starcluster (NSC) that includes observational constraints from a large sample of stellar metallicity measurements. These
metallicity measurements were obtained from recent surveys from Gemini and VLT of 770 late-type stars within thecentral 1.5 pc. These metallicity measurements, along with photometry and spectroscopically derived temperatures,are forward modeled with a Bayesian inference approach. Including metallicity measurements improves the overall
fit quality, as the low-temperature red giants that were previously difficult to constrain are now accounted for, andthe best fit favors a two-component model. The dominant component contains 93([M/H] ∼0.45), and has an ageof 5+3−2 Gyr, which is ∼3 Gyr younger than earlier studies with fixed (solar) metallicity; this younger age challenges
co-evolutionary models in which the NSC and supermassive black holes formed simultaneously at early times. The
minor population component has low metallicity ([M/H] ∼ -1.1) and contains ∼7- 5 Gyr old). Using the estimatedparameters, we infer the following NSC stellar remnant population (with ∼18neutron stars, 2.5×105 stellar mass black
holes (BHs) and 2.2×104 BH-BH binaries. These predictions result in 2-4 times fewer neutron stars compared toearlier predictions that assume solar metallicity, introducing a possible new path to understand the so-called "missing
pulsar problem". Finally, we present updated predictions for the BH-BH merger rates (0.01-3 Gpc−3 yr−1 ).

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6. The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
Tao-Chung Ching and the BISTRO team F We present 850 µm dust polarization observations of the massive DR21
filament from the B-fields In STar-forming Region Observations (BISTRO) survey, using the POL-2 polarimeter andthe SCUBA-2 camera on the James Clerk Maxwell Telescope. We detect ordered magnetic fields perpendicular tothe parsec-scale ridge of the DR21 main filament. In the sub-filaments, the magnetic fields are mainly parallel to thefilamentary structures and smoothly connect to the magnetic fields of the main filament. We compare the POL-2 andPlanck dust polarization observations to study the magnetic field structures of the DR21 filament on 0.1–10 pc scales.
The magnetic fields revealed in the Planck data are well aligned with those of the POL-2 data, indicating a smoothvariation of magnetic fields from large to small scales. The plane-of-sky magnetic field strengths derived from angulardispersion functions of dust polarization are 0.6–1.0 mG in the DR21 filament and ∼ 0.1 mG in the surrounding
ambient gas. The mass-to-flux ratios are found to be magnetically supercritical in the filament and slightly subcriticalto nearly critical in the ambient gas. The alignment between column density structures and magnetic fields changes
from random alignment in the low-density ambient gas probed by Planck to mostly perpendicular in the high-density
main filament probed by JCMT. The magnetic field structures of the DR21 filament are in agreement with MHD
simulations of a strongly magnetized medium, suggesting that magnetic fields play an important role in shaping theDR21 main filament and sub-filaments.

7. Making the Solar System
John Chambers F We model the early stages of planet formation in the Solar System, including continual planetesimalformation, and planetesimal and pebble accretion onto planetary embryos in an evolving disk driven by a disk wind.
The aim is to constrain aspects of planet formation that have large uncertainties by matching key characteristics of
the Solar System. The model produces a good fit to these characteristics for a narrow range of parameter space.
Planetary growth beyond the ice line is dominated by pebble accretion. Planetesimal accretion is more important
inside the ice line. Pebble accretion inside the ice line is slowed by higher temperatures, partial removal of inflowing
pebbles by planetesimal formation and pebble accretion further out in the disk, and increased radial velocities due
to gas advection. The terrestrial planets are prevented from accreting much water ice because embryos beyond theice line reach the pebble isolation mass before the ice line enters the terrestrial-planet region. When only pebble
accretion is considered, embryos typically remain near their initial mass or grow to the pebble-isolation mass. Adding
planetesimal accretion allows Mars-sized objects to form inside the ice line, and allows giant-planet cores to form overa wider region beyond the ice line. In the region occupied by Mercury, pebble Stokes numbers are small. This delays
the formation of embryos and stunts their growth, so that only low-mass planets can form here.

8. UV-driven Chemistry as a Signpost for Late-stage Planet Formation

Jenny K. Calahan, Edwin A. Bergin, Arthur D. Bosman, Evan Rich, Sean M. Andrews, Jennifer B. Bergner,
L. Ilsedore Cleeves, Viviana V. Guzman, Jane Huang, John D. Ilee, Charles J. Law, Romane Le Gal, Karin
I. Oberg, Richard Teague, Catherine Walsh, David J. Wilner, Ke Zhang F The chemical reservoir within pro-toplanetary disks has a direct impact on planetary compositions and the potential for life. A long-lived carbon-and
nitrogen-rich chemistry at cold temperatures (<=50K) is observed within cold and evolved planet-forming disks. Thisis evidenced by bright emission from small organic radicals in 1-10 Myr aged systems that would otherwise have frozen
out onto grains within 1 Myr. We explain how the chemistry of a planet-forming disk evolves from a cosmic-ray/Xray-dominated regime to an ultraviolet-dominated chemical equilibrium. This, in turn, will bring about a temporaltransition in the chemical reservoir from which planets will accrete. This photochemical dominated gas phase chemistry develops as dust evolves via growth, settling and drift, and the small grain population is depleted from the disk
atmosphere. A higher gas-to-dust mass ratio allows for deeper penetration of ultraviolet photons is coupled with acarbon-rich gas (C/O > 1) to form carbon-bearing radicals and ions. This further results in gas phase formation oforganic molecules, which then would be accreted by any actively forming planets present in the evolved disk.

9. Length-scales and Dynamics of Carina’s Western Wall

Turlough Downes, Patrick Hartigan, Andrea Isella F We present a variety of analyses of the turbulent dynamics
of the boundary of a photo-dissociation region (PDR) in the Carina Nebula using high resolution ALMA observations.
Using Principal Component Analysis we suggest that the turbulence in this molecular cloud is driven at large scales.
Analysis of the centroid velocity structure functions indicate that the turbulence is dominated by shocks rather than4

local (in k-space) transport of energy. We further find that length-scales in the range 0.02 - 0.03 pc are important in
the dynamics of this cloud and this finding is supported by analysis of the dominant emission structure length-scale.
These length-scales are well resolved by the observational data and we conclude that the apparent importance of thisrange of scales is physical in origin. Given that it is also well within the range strongly influenced by ambipolar
diffusion, we conclude that it is not primarily a product of turbulence alone, but is more likely to be a result of theinterplay between gravity and turbulence. Finally, through comparison of these results with previous observations ofH2 emission from the Western Wall we demonstrate that observations of a PDR can be used to probe the internal
structure of the undisturbed portion of a molecular cloud.

10. Discovery of a New Molecular Bubble-Outflow Structure in the Taurus B18 Cloud

Yan Duan, Di Li, Paul F. Goldsmith, Laurent Pagani, Tao-Chung Ching, Shu Liu, Jinjin Xie, Chen Wang

F Star formation can produce bubbles and outflows, as a result of stellar feedback. Outflows and bubbles inject
momentum and energy into the surrounding interstellar medium, and so are related to the overall energy balance ofthe molecular cloud. Molecular bubbles can be resolved by higher-resolution radio telescopes to quantify the effect ofstar formation on molecular clouds. We report here the identification of a new molecular bubble with an outflow, andan Herbig Haro object, HH319, located at the bubble center. Multi-wavelength data have been utilized to study its
spatial structure, energy injection, and dynamical timescale. This bubble has a kinetic energy of 5.8 × 1043 erg within
the smallest radius of a bubble in Taurus, 0.077 pc. The bubble formed ∼70,000 years ago. According to the propermotion velocities of protostars from Gaia EDR3, the T Tauri binary stars (FY Tau and FZ Tau) at the southwestedge of the bubble may have produced the outflow-bubble structure. This is an unusual new structure found in lowand intermediate-mass star formation regions. Only a bubble in Orion A, driven by V380 Ori, has a similar structure.
The bubble-outflow structure provides additional observational evidence for the theory of stellar wind from T Tauristars. It enhances our understanding of how stellar feedback acts on molecular clouds.

11. Constraining the turbulence and the dust disk in IM Lup: onset of planetesimal formation

Riccardo Franceschi, Tilman Birnstiel, Thomas Henning, Anirudh Sharma F Observations of protoplanetarydisks provide information on planet formation and the reasons for the diversity of planetary systems. The key tounderstanding planet formation is the study of dust evolution from small grains to pebbles. Smaller grains are wellcoupled to the gas dynamics, and their distribution is significantly extended above the disk midplane. Larger grains
settle much faster and are efficiently formed only in the midplane. By combining near-infrared polarized light andmillimeter observations, it is possible to constrain the spatial distribution of both the small and large grains. We aim toconstruct detailed models of the size distribution and vertical/radial structure of the dust particles in protoplanetarydisks based on observational data. In particular, we are interested in recovering the dust distribution in the IM Lup
protoplanetary disk. We create a physical model for the dust distribution of protoplanetary disks and simulate theradiative transfer of the millimeter continuum and the near-infrared polarized radiation. Using a Markov chain Monte
Carlo method, we compare the derived images to the observations available for the IM Lup disk to constrain thebest physical model for IM Lup and to recover the vertical grain size distribution. The millimeter and near-infraredemission tightly constrain the dust mass and grain size distribution of our model. We find size segregation in the
dust distribution, with millimeter-sized grains in the disk midplane. These grains are efficiently formed in the disk,
possibly by sedimentation-driven coagulation, in accord with the short settling timescales predicted by our model.
This also suggests a high dust-to-gas ratio at smaller radii in the midplane, possibly triggering streaming instabilities
and planetesimal formation in the inner disk.

12. A 3D View of Orion: I. Barnard’s Loop
Michael M. Foley, Alyssa Goodman, Catherine Zucker, John C. Forbes, Ralf Konietzka, Cameren Swiggum,João Alves, John Bally, Juan D. Soler, Josefa E. Großschedl, Shmuel Bialy, Michael Y. Grudić, Reimar Leike,
Torsten Ensslin F Barnard’s Loop is a famous arc of Hα emission located in the Orion star-forming region. Here,

we provide evidence of a possible formation mechanism for Barnard’s Loop and compare our results with recent worksuggesting a major feedback event occurred in the region around 6 Myr ago. We present a 3D model of the large-scale
Orion region, indicating coherent, radial, 3D expansion of the OBP-Near/Briceño-1 (OBP-B1) cluster in the middle
of a large dust cavity. The large-scale gas in the region also appears to be expanding from a central point, originally5

proposed to be Orion X. OBP-B1 appears to serve as another possible center, and we evaluate whether Orion X or
OBP-B1 is more likely to be the cause of the expansion. We find that neither cluster served as the single expansion
center, but rather a combination of feedback from both likely propelled the expansion. Recent 3D dust maps areused to characterize the 3D topology of the entire region, which shows Barnard’s Loop’s correspondence with a large
dust cavity around the OPB-B1 cluster. The molecular clouds Orion A, Orion B, and Orion λ reside on the shellof this cavity. Simple estimates of gravitational effects from both stars and gas indicate that the expansion of thisasymmetric cavity likely induced anisotropy in the kinematics of OBP-B1. We conclude that feedback from OBP-B1
has affected the structure of the Orion A, Orion B, and Orion λ molecular clouds and may have played a major rolein the formation of Barnard’s Loop.

saturated states of the vertical shear instability in protoplanetary disks with ver13. Twotically varying cooling times
Yuya Fukuhara, Satoshi Okuzumi, Tomohiro Ono F Turbulence in protoplanetary disks plays an important role indust evolution and planetesimal formation. The vertical shear instability (VSI) is one of the candidate hydrodynamic
mechanisms that can generate turbulence in the outer disk regions. The VSI requires rapid gas cooling in addition
to vertical shear. A linear stability analysis suggests that the VSI may not operate around the midplane where gas
cooling is inefficient. In this study, we investigate the nonlinear outcome of the VSI in disks with a linearly VSI-stablemidplane region. We perform two-dimensional global hydrodynamical simulations of an axisymmetric disk with vertically varying cooling times. The vertical cooling time profile determines the thicknesses of the linearly VSI-stablemidplane layer and unstable layers above and below the midplane. We find that the thickness of the midplane stablelayer determines the vertical structure of VSI-driven turbulence in the nonlinear saturated state. We identify two
types of final saturated state: (1) T states characterized by vertical turbulent motion penetrating into the VSI-stablemidplane layer and (2) pT states characterized by turbulent motion confined in the unstable layers. The pT states are
realized when the midplane VSI-stable layer is thicker than two gas scale heights. We also find that the VSI-driven
turbulence is largely suppressed at all heights when the VSI-unstable region lying above and below the midplane isthinner than two gas scale heights. We present empirical formulas that predict the strength of VSI-driven turbulence
as a function of the thicknesses of the unstable and stable layers. These formulas will be useful for studying how
VSI-driven turbulence and dust grains controlling the disk cooling efficiency evolve simultaneously.

Distance determination of molecular clouds in the 1st quadrant of the Galactic plane

14. using deep learning : I. Method and Results

Shinji Fujita, A. M. Ito, Yusuke Miyamoto, Yasutomo Kawanishi, Kazufumi Torii, Yoshito Shimajiri, Atsushi
Nishimura, Kazuki Tokuda, Toshikazu Ohnishi, Hiroyuki Kaneko, Tsuyoshi Inoue, Shunya Takekawa, Mikito
Kohno, Shota Ueda, Shimpei Nishimoto, Ryuki Yoneda, Kaoru Nishikawa, Daisuke Yoshida F Machine learning

has been successfully applied in varied field but whether it is a viable tool for determining the distance to molecular
clouds in the Galaxy is an open question. In the Galaxy, the kinematic distance is commonly employed as the distanceto a molecular cloud. However, there is a problem in that for the inner Galaxy, two different solutions, the “Near”
solution, and the “Far” solution, can be derived simultaneously. We attempted to construct a two-class (“Near” or“Far”) inference model using a Convolutional Neural Network (CNN), a form of deep learning that can capture spatial
features generally. In this study, we used the CO dataset toward the 1st quadrant of the Galactic plane obtained with
the Nobeyama 45-m radio telescope (l = 62-10 degree, |b| < 1 degree). In the model, we applied the three-dimensional
distribution (position-position-velocity) of the 12CO (J=1-0) emissions as the main input. The dataset with “Near” or“Far” annotation was made from the HII region catalog of the infrared astronomy satellite WISE to train the model.
As a result, we could construct a CNN model with a 76training dataset. By using the model, we determined the
distance to molecular clouds identified by the CLUMPFIND algorithm. We found that the mass of the molecular
clouds with a distance of < 8.15 kpc identified in the 12CO data follows a power-law distribution with an index ofabout -2.3 in the mass range of M >103 Msun. Also, the detailed molecular gas distribution of the Galaxy as seenfrom the Galactic North pole was determined.

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15. Clustered Formation of Massive Stars within an Ionized Rotating Disk
Roberto Galván-Madrid, Qizhou Zhang, Andrés Izquierdo, Charles J. Law, Thomas Peters, Eric Keto, Hauyu
Baobab Liu, Paul T. P. Ho, Adam Ginsburg, Carlos Carrasco-González F We present ALMA observations witha 800 au resolution and radiative-transfer modelling of the inner part (r ≈ 6000 au) of the ionized accretion flow
around a compact star cluster in formation at the center of the luminous ultra-compact (UC) HII region G10.6-0.4.
We modeled the flow with an ionized Keplerian disk with and without radial motions in its outer part, or with an
external Ulrich envelope. The MCMC fits to the data give total stellar masses M? from 120 to 200 M , with muchsmaller ionized-gas masses Mion−gas = 0.2 to 0.25 M . The stellar mass is distributed within the gravitational radius
Rg ≈ 1000 to 1500 au, where the ionized gas is bound. The viewing inclination angle from the face-on orientation isi = 49 to 56 deg. Radial motions at radii r > Rg converge to vr,0 ≈ 8.7 km/s, or about the speed of sound of ionizedgas, indicating that this gas is marginally unbound at most. From additional constraints on the ionizing-photon rate
and far-IR luminosity of the region, we conclude that the stellar cluster consists of a few massive stars with Mstar = 32
to 60 M , or one star in this range of masses accompanied by a population of lower-mass stars. Any active accretionof ionized gas onto the massive (proto)stars is residual. The inferred cluster density is very large, comparable to thatreported at similar scales in the Galactic Center. Stellar interactions are likely to occur within the next Myr.

between metallicities and spectral energy distributions of Herbig Ae/Be stars.
16. Relation
A potential link with planet formation
J. Guzman-Diaz, B. Montesinos, I. Mendigutia, M. Kama, G. Meeus, M. Vioque, R. D. Oudmaijer, E. Villaver

F (Abridged) The stellar metallicity, [M/H], may have important implications for planet formation. In particular,
Kama et al. proposed that the deficit of refractory elements in the surfaces of some Herbig Ae/Be stars (HAeBes) may
be linked to the presence of disk cavities likely caused by Jovian planets that trap the metal-rich content. This work
aims to provide a robust test on the previous proposal by analyzing the largest sample of HAeBes with homogeneously
derived [M/H] values, stellar, and circumstellar properties. [M/H] values of 67 HAeBes were derived based on observed
spectra and Kurucz synthetic models. Statistical analyses were carried out aiming to test the potential relation between[M/H] and the group I sources from the spectral energy distribution (SED) classification by Meeus et al., associatedto the presence of cavities potentially carved by giant planets. Our study robustly confirms that group I sources tend
to have a lower [M/H] than that of group II HAeBes. A similar analysis involving SED-based transitional disks does
not reveal such a relation, indicating that not all processes capable of creating dust holes have an effect on the stellar
abundances. We also show that the observed [M/H] differences are not driven by environmental effects. Finally, group
I sources tend to have stronger (sub-) mm continuum emission presumably related to the presence of giant planets.
Indeed, literature results indicate that disk substructures probably associated to their presence are up to ten times
more frequent in group I HAeBes. We provide indirect evidences suggesting that giant planets are more frequentaround group I/low [M/H] stars than around the rest of the HAeBes. However, the direct test requires multiple
detections of forming planets in their disks, so far limited to the candidate around the metal depleted ([M/H] = -0.35+- 0.25) group I HAeBe star AB Aur.

17. Models of Rotating Infall for the B335 Protostar

Neal J. Evans II, Yao-Lun Yang, Joel D. Green, Bo Zhao, James Di Francesco, Jeong-Eun Lee, Jes K. Jørgensen, Minho Choi, Philip C. Myers, Diego Mardones F Models of the protostellar source, B335, are developed

using axisymmetric three-dimensional models to resolve conflicts found in one-dimensional models. The models areconstrained by a large number of observations, including ALMA, Herschel, and Spitzer data. Observations of the
protostellar source B335 with ALMA show red-shifted absorption against a central continuum source indicative ofinfall in the HCO+ and HCN J = 4 → 3 transitions. The data are combined with a new estimate of the distanceto provide strong constraints to three-dimensional radiative transfer models including a rotating, infalling envelope,
outflow cavities, and a very small disk. The models favor ages since the initiation of collapse between 3 × 104 and4 × 104 yr for both the continuum and the lines, resolving a conflict found in one-dimensional models. The models
under-predict the continuum emission seen by ALMA, suggesting an additional component such as a pseudo-disk. The
best-fitting model is used to convert variations in the 4.5 µm flux in recent years into a model for a variation of afactor of 5-7 in luminosity over the last 8 years.

718. X-Shooter Survey of Young Intermediate Mass Stars – I. Stellar Characterization andDisc Evolution

Daniela P. Iglesias, Olja Panić, Mario van den Ancker, Monika G. Petr-Gotzens, Lionel Siess, Miguel Vioque,
Ilaria Pascucci, René Oudmaijer, James Miley F Intermediate mass stars (IMSs) represent the link between

low-mass and high-mass stars and cover a key mass range for giant planet formation. In this paper, we present aspectroscopic survey of 241 young IMS candidates with IR-excess, the most complete unbiased sample to date within
300 pc. We combined VLT/X-Shooter spectra with BVR photometric observations and Gaia DR3 distances to estimate
fundamental stellar parameters such as Teff, mass, radius, age, and luminosity. We further selected those stars within
the intermediate mass range 1.5 <= Mstar/Msun <= 3.5 and discarded old contaminants. We used 2MASS and
WISE photometry to study the IR-excesses of the sample, finding 92 previously unidentified stars with IR-excess. We
classified this sample into ’protoplanetary’, ’hybrid candidates’ and ’debris’ discs based on their observed fractional
excess at 12microns, finding a new population of 17 hybrid disc candidates. We studied inner disc dispersal timescalesfor λ < 10µm and found very different trends for IMSs and low mass stars (LMSs). IMSs show excesses dropping
fast during the first 6 Myrs independently of the wavelength, while LMSs show consistently lower fractions of excess
at the shortest wavelengths and increasingly higher fractions for longer wavelengths, with slower dispersal rates. In
conclusion, this study demonstrates empirically that IMSs dissipate their inner discs very differently than LMSs,
providing a possible explanation for the lack of short period planets around IMSs.

Motion and Possibility of Dust Growth in a Growing Circumstellar Disk
19. Dust
Shunta Koga, Masahiro N. Machida F We calculate the evolution of a star-forming cloud core using a threedimensional resistive magnetohydrodynamics simulation, treating dust grains as Lagrangian particles, to investigate
the dust motion in the early star formation stage. We prepare six different-sized set of dust particles in the range
ad = 0.01–1000 µm, where ad is the dust grain size. In a gravitationally collapsing cloud, a circumstellar disk forms
around a protostar and drives a protostellar outflow. Almost all the small dust grains (ad . 10–100 µm) initiallydistributed in the region θ0 . 45◦ are ejected from the center by the outflow, where θ0 is the initial zenith angle
relative to the rotation axis, whereas only a small number of the large dust grains (ad & 100 µm) distributed in
the region are ejected. All other grains fall onto either the protostar or disk without being ejected by the outflow.
Regardless of the dust grain size, the behavior of the dust motion is divided into two trends after dust particles settle
into the circumstellar disk. The dust grains reaching the inner disk region from the upper envelope preferentially fall
onto the protostar, while those reaching the outer disk region or disk outer edge from the envelope can survive without
an inward radial drift. These surviving grains can induce dust growth. Thus, we expect that the outer disk regions
could be a favored place of planet formation.

20. The shocked molecular layer in RCW 120
M. S. Kirsanova, Ya. N. Pavlyuchenkov, A. O. H. Olofsson, D. A. Semenov, A. F. Punanova F Expansion ofwind-blown bubbles or HII regions lead to formation of shocks in the interstellar medium, which compress surrounding
gas into dense layers. We made spatially and velocity-resolved observations of the RCW 120 PDR and nearby moleculargas with CO(6-5) and 13CO(6-5) lines and distinguished a bright CO-emitting layer, which we related with the dense
shocked molecular gas moving away from the ionizing star due to expansion of HII region. Simulating gas density andtemperature, as well as brightness of several CO and C+ emission lines from the PDR, we found reasonable agreementwith the observed values. Analysing gas kinematics, we revealed the large-scale shocked PDR and also several dense
environments of embedded protostars and outflows. We observe the shocked layer as the most regular structure in theCO(6-5) map and in the velocity space, when the gas around YSOs is dispersed by the outflows.

21. The molecular environment of the solar-type protostar IRAS 16293-2422

K. Angelique Kahle, Antonio Hernández-Gómez, Friedrich Wyrowski, Karl M. Menten F Studying the physicaland chemical processes leading to the formation of low-mass stars is crucial for understanding the origin of our Sun
and the Solar System. In particular, analyzing the emission and absorption lines from molecules is a fundamental
tool to obtain information on the kinematics and chemistry at the very early stages of star formation. In this work
we aim to examine the spatial structures and molecular abundances of material surrounding the very well-known
low-mass binary protostar IRAS 16293-2422 and the prestellar core 16293E, which are embedded in the Lynds 1689N
dark cloud. We have used the LAsMA heterodyne array installed on the Atacama Pathfinder EXperiment (APEX) 12

8

meter submillimeter telescope to image a region of about 0.12x0.12pc2 around IRAS 16293-2422 and 16293E and to
study their molecular environment covering 45.6GHz in a frequency range from 277GHz to 375GHz. We have identified
144 transitions from 36 molecular species, including isotopologues. The maps reveal the envelope to have a complex
morphology around the cloud cores and the emission peaks known as E1, E2, W1, W2, and HE2, including the outflow
structure arising from IRAS 16293-2422. Using several transitions of para-H2 CO, we have derived new lower limits forthe kinetic temperatures toward IRAS 16293-2422 and the surrounding emission peaks. Based on these temperatures,H2 volume densities and column densities for all detected species were derived around the cloud cores and all emission
peaks. Our new observations further confirm the scenario of an outflow arising from IRAS 16293-2422 interactingwith the prestellar core 16293E. We observe a large-scale velocity gradient across the molecular cloud. Furthermore,
we see clear chemical differences at the examined positions. The data suggests that emission peak W2 may be related
to a colder dust source.

22. Disk dissipation, giant planet formation and star-formation-rate fluctuations in the past
three-million-year history of Gould’s Belt

Mingchao Liu, Jinhua He, Jixing Ge, Tie Liu, Yuping Tang, Xuzhi Li F Although episodic star formation (SF) had

been suggested for nearby SF regions, a panoramic view to the latest episodic SF history in the solar neighborhood
is still missing. By uniformly constraining the slope α of infrared spectral energy distributions (SEDs) of youngstellar objects (YSOs) in the 13 largest Gould’s Belt (GB) protoclusters surveyed by Spitzer Space Telescope, wehave constructed a cluster-averaged histogram of α representing YSO evolution lifetime as a function of the α value.
Complementary to the traditional SED classification scheme (0, I, F, II, III) that is based on different α values, astaging scheme (A,B,C,D,E) of SED evolution is advised on the basis of the α statistical features that can be better
matched to the physical stages of disk dissipation and giant planet formation. This has also allowed us to unravel
the fluctuations of star formation rate (SFR) in the past three-million-year (3 Myr) history of these GB protoclusters.
Diverse evolutionary patterns such as single peak, double peaks and on-going acceleration of SFR are revealed. The
SFR fluctuations are between 20% ∼ 60% (∼ 40% on average) and no dependence on the average SFR or the number of
SFR episodes is found. However, spatially close protoclusters tend to share similar SFR fluctuation trends, indicatingthat the driving force of the fluctuations should be at size scales beyond the typical cluster sizes of several parsec.

23. Dust Rings and Cavities in the Protoplanetary Disks around HD 163296 and DoAr 44
Harrison Leiendecker, Hannah Jang-Condell, Neal J. Turner, Adam D. Myers F We model substructure in the
protoplanetary disks around DoAr 44 and HD 163296 in order to better understand the conditions under which planets
may form. We match archival millimeter-wavelength thermal emission against models of the disks’ structure that are
in radiation balance with the starlight heating and in vertical hydrostatic equilibrium, and then compare to archival
polarized scattered near-infrared images of the disks. The millimeter emission arises in the interior, while the scatterednear-infrared radiation probes the disks’ outer layers. Our best model of the HD 163296 disk has dust masses 81 ± 13
M⊕ in the inner ring at 68 au and 82+26−16 M⊕ in the outer ring at 102 au, both falling within the range of estimatesfrom previous studies. Our DoAr 44 model has total dust mass 84+7.0−3.5 M⊕ . Unlike HD 163296, DoAr 44 as of yet has
no detected planets. If the central cavity in the DoAr 44 disk is caused by a planet, the planet’s mass must be at least
0.5 MJ and is unlikely to be greater than 1.6 MJ . We demonstrate that the DoAr 44 disk’s structure with a brightring offset within a fainter skirt can be formed by dust particles drifting through a plausible distribution of gas.

The IGRINS YSO Survey III: Stellar parameters of pre-main sequence stars in Ophi-

24. uchus and Upper Scorpius

Ricardo López-Valdivia, Gregory N. Mace, Eunkyu Han, Erica Sawczynec, Jesús Hernández, L. Prato, Christopher M. Johns-Krull, Heeyoung Oh, Jae-Joon Lee, Adam Kraus, Joe Llama, Daniel T. Jaffe F We used the

Immersion GRating Infrared Spectrometer (IGRINS) to determine fundamental parameters for 61 K- and M-type
young stellar objects (YSOs) located in the Ophiuchus and Upper Scorpius star-forming regions. We employed synthetic spectra and a Markov chain Monte Carlo approach to fit specific K-band spectral regions and determine thephotospheric temperature (Teff ), surface gravity (log g), magnetic field strength (B), projected rotational velocity(v sin i), and K-band veiling (rK ). We determined B for ∼46the results from Taurus-Auriga and the TW Hydrae
Association (TWA) presented in Paper I of this series. We classified all the YSOs in the IGRINS survey with infrared
spectral indices from 2MASS and WISE photometry between 2 and 24 µm. We found that Class II YSOs typically9have lower log g and v sin i, similar B, and higher K-band veiling than their Class III counterparts. Additionally, we
determined the stellar parameters for a sample of K and M field stars also observed with IGRINS. We have identified
intrinsic similarities and differences at different evolutionary stages with our homogeneous determination of stellar
parameters in the IGRINS YSO Survey. Considering log g as a proxy for age, we found that the Ophiuchus andTaurus samples have a similar age. We also find that Upper Scorpius and TWA YSOs have similar ages, and are more
evolved than Ophiuchus/Taurus YSOs.

25. Mapping Protoplanetary Disk Vertical Structure with CO Isotopologue Line Emission
Charles J. Law, Richard Teague, Karin I. Öberg, Evan A. Rich, Sean M. Andrews, Jaehan Bae, Myriam
Benisty, Stefano Facchini, Kevin Flaherty, Andrea Isella, Sheng Jin, Jun Hashimoto, Jane Huang, Ryan A.
Loomis, Feng Long, Carlos E. Muñoz-Romero, Teresa Paneque-Carreño, Laura M. Pérez, Chunhua Qi, Kamber
R. Schwarz, Jochen Stadler, Takashi Tsukagoshi, David J. Wilner, Gerrit van der Plas F High spatial resolution

observations of CO isotopologue line emission in protoplanetary disks at mid-inclinations (≈30-75 degrees) allow us
to characterize the gas structure in detail, including radial and vertical substructures, emission surface heights andtheir dependencies on source characteristics, and disk temperature profiles. By combining observations of a suite of
CO isotopologues, we can map the 2D (r, z) disk structure from the disk upper atmosphere, as traced by CO, to near
the midplane, as probed by less abundant isotopologues. Here, we present high angular resolution (.0."1 to ≈0."2;≈15-30 au) observations of CO, 13 CO, and C18 O in either or both J=2-1 and J=3-2 lines in the transition disks around
DM Tau, Sz 91, LkCa 15, and HD 34282. We derived line emission surfaces in CO for all disks and in 13 CO for the
DM Tau and LkCa 15 disks. With these observations, we do not resolve the vertical structure of C18 O in any disk,
which is instead consistent with C18 O emission originating from the midplane. Both the J=2-1 and J=3-2 lines show
similar heights. Using the derived emission surfaces, we computed radial and vertical gas temperature distributions
for each disk, including empirical temperature models for the DM Tau and LkCa 15 disks. After combining our sample
with literature sources, we find that 13 CO line emitting heights are also tentatively linked with source characteristics,
e.g., stellar host mass, gas temperature, disk size, and show steeper trends than seen in CO emission surfaces.

26. First detection of CHD2 OH towards pre-stellar cores

Yuxin Lin, Silvia Spezzano, Paola Caselli F The inheritance of material across the star and planet formation

process is traced by deuterium fractionation. We report here the first detection of doubly deuterated methanol
towards pre-stellar cores. We study the deuterium fractionation of methanol, CH3 OH, towards two starless and two
pre-stellar cores. We derive a D/H ratio of 0.8-1.9% with CH2 DOH in pre-stellar cores H-MM1 and L694-2, consistent
with measurements in more evolved Class 0/I objects and comet 67P/Churyumov-Gerasimenko, suggesting a direct
chemical link arising in the pre-stellar stage. Furthermore, the column density ratios of CHD2 OH/CH2 DOH are ∼5080%, consistently high as that towards Class 0/I objects, indicating an efficient formation mechanism of CHD2 OH,
possibly through H atom additions to D2 CO. The CH2 DOH/CH3 OH and CHD2 OH/CH3 OH column density ratios in
the two pre-stellar cores are larger than that in the two starless cores B68 and L1521E, representing an evolutionary
trend of methanol deuteration in early-stage cores.

27. Rossby numbers of fully and partially convective stars
N. R. Landin, L. T. S. Mendes, L. P. R. Vaz, S. H. P. Alencar F We investigate stellar magnetic activity fromthe theoretical point of view, by using stellar evolution models to calculate theoretical convective turnover times (τc )and Rossby numbers (Ro) for pre-main-sequence and main-sequence stars. The problem is that the canonical place
where τc is usually determined (half a mixing length above the base of the convective zone) fails for fully convective
stars and there is no agreement on this in the literature. Our calculations were performed with the ATON stellar
evolution code. We concentrated our analysis on fully and partially convective stars motivated by recent observationsof slowly rotating fully convective stars, whose X-ray emissions correlate with their Rossby numbers in the same way
as in solar-like stars, suggesting that the presence of a tachocline is not required for magnetic field generation. We
investigate the behaviour of τc over the stellar radius for stars of different masses and ages. As Ro depends on τc ,which varies strongly with the stellar radius, we use our theoretical results to determine a better radial position atwhich to calculate it for fully convective stars. Using our alternative locations, we fit a sample of 847 stars in therotation-activity diagram (LX /Lbol versus Ro) with a two-part power-law function. Our fit parameters are consistent
with previous work, showing that stars with Ro≤Rosat are distributed around a saturation level in LX /Lbol and, for10

stars with Ro>Rosat , LX /Lbol clearly decays with Ro with an exponent of −2.4±0.1.

28. The role of the turbulence driving mode for the Initial Mass Function

Sajay Sunny Mathew, Christoph Federrath, Amit Seta F Turbulence is a critical ingredient for star formation,
yet its role for the initial mass function (IMF) is not fully understood. Here we perform magnetohydrodynamical(MHD) simulations of star cluster formation including gravity, turbulence, magnetic fields, stellar heating and outflow
feedback to study the influence of the mode of turbulence driving on IMF. We find that simulations that employ purelycompressive turbulence driving (COMP) produce a higher fraction of low-mass stars as compared to simulations thatuse purely solenoidal driving (SOL). The characteristic (median) mass of the sink particle (protostellar) distribution
for COMP is shifted to lower masses by a factor of 1.5 compared to SOL. Our simulation IMFs capture the importantfeatures of the observed IMF form. We find that turbulence-regulated theories of the IMF match our simulation IMFs
reasonably well in the high-mass and low-mass range, but underestimate the number of very low-mass stars, which
form towards the later stages of our simulations and stop accreting due to dynamical interactions. Our simulations
show that for both COMP and SOL, the multiplicity fraction is an increasing function of the primary mass, although
the multiplicity fraction in COMP is higher than that of SOL for any primary mass range. We find that binary mass
ratio distribution is independent of the turbulence driving mode. The average specific angular momentum of the sinkparticles in SOL is a factor of 2 higher than that for COMP. Overall, we conclude that the turbulence driving mode
plays a significant role in shaping the IMF.

29. An expanding ring of the hypercompact HII region W49N:A2

Ryosuke Miyawaki, Masahiko Hayashi, Tetsuo Hasegawa F We present 250 GHz continuum and H29alpha line
data toward W49N:A2, a hypercompact HII region ionized by an O9 star. The data obtained with ALMA at aresolution of 0"05 (600 au) confirmed the presence of an ionized ring with a radius of 700 au inclined by 50degree(0degree for pole-on). It has a width of 1000 au and is relatively flat with a scale height of less than several hundredau. The tilted ring, or the apparent ellipse, has a prominent velocity difference between its NW and SE ridges along
the minor axis, suggesting that it is expanding in the equatorial plane at a velocity of 13.2 km/s. The ring also shows ahint of rotation at 2.7 km/s, which is significantly (2.5sigma) smaller than the Kepler velocity of 5.2 km/s at its radiusaround the 20 M star. This can be interpreted that the ring gas has been transported from the radius of 170 au byconserving its original specific angular momentum that it had there. The ionized ring may thus be a remnant of theaccretion disk that fed the O9 star, whose radiation or magnetic activities became so strong that the disk accretion
was reversed due to the intense thermal or magneto-hydrodynamic pressure around the star. The data has revealed arare example of how a massive star terminates its accretion at the end of its formation, transforming a hypercompact
HII region into an ultracompact HII region.

Evolution of the Angular Momentum of Molecular Cloud Cores Formed from Filament

30. Fragmentation

Yoshiaki Misugi, Shu-ichiro Inutsuka, Doris Arzoumanian F The angular momentum of molecular cloud cores plays

an essential role in the star formation process. However, the time evolution of the angular momentum of molecular
cloud cores is still unclear. In this paper, we perform three-dimensional simulations to investigate the time evolutionof the angular momentum of molecular cloud cores formed through filament fragmentation. As a result, we find thatmost of the cores rotate perpendicular to the filament axis. The mean angular momentum of the cores changes by
only around 30the initial stage of their formation process and then remains almost constant. In addition, we analyze
the internal angular momentum structure of the cores. Although the cores gain angular momentum with various
directions from the initial turbulent velocity fluctuations of their parent filaments, the angular momentum profile ineach core converges to the self-similar solution. We also show that the degree of complexity of the angular momentum
structure in a core slightly decreases with time. Moreover, we perform synthetic observations and show that theangular momentum profile measured from the synthetic mean velocity map is compatible with the observations when
the filament inclination is taken into account. The present study suggests a theory of core formation from filament
fragmentation where the angular momentum structures of the cores are determined by the velocity fluctuation along
the filaments and both are compatible with the observations. This theory also provides new insights on the coreproperties that could be observationally tested.

11

of HAC evolution on the formation of small hydrocarbons in the Orion Bar and31. Impact
the Horsehead PDRs
M. S. Murga, A. I. Vasyunin, M. S. Kirsanova F We study evolution of hydrogenated amorphous carbon (HAC)

grains under harsh UV radiation in photo-dissociation regions (PDRs) near young massive stars. Our aim is to evaluate
the impact of the HAC grains on formation of observed small hydrocarbons: C2 H, C2 H2 , C3 H+ , C3 H, C3 H2 , C4 H,
in PDRs. We developed a microscopic model of the HAC grains based on available experimental results. The model
includes processes of photo- and thermodesorption, accretion of hydrogen and carbon atoms and subsequent formationof carbonaceous mantle on dust surface. H2 , CH4 , C2 H2 , C2 H4 , C2 H6 , C3 H4 , C3 H6 , C3 H8 are considered as the main
fragments of the HAC photo-destruction. We simulated evolution of the HAC grains under the physical conditions of
two PDRs, the Orion Bar and the Horsehead nebula. We estimated the production rates of the HAC fragments in gas
phase chemical reactions and compared them with the production rates of fragments due to the HAC destruction. The
latter rates may dominate under some conditions, namely, at AV =0.1 in both PDRs. We coupled our model with thegas-grain chemical model MONACO and calculated abundances of observed small hydrocarbons. We conclude thatthe contribution of the HAC destruction fragments to chemistry is not enough to match the observed abundances,although it increases the abundances by several orders of magnitude in the Orion Bar at AV =0.1. Additionally, we
found that the process of carbonaceous mantle formation on dust surface can be an inhibitor for the formation ofobserved small hydrocarbons in PDRs.

32. Cold Deuterium Fractionation in the Nearest Planet-Forming Disk
Carlos E. Muñoz-Romero, Karin I. Öberg, Charles J. Law, Richard Teague, Yuri Aikawa, Jennifer B. Bergner,
David J. Wilner Jane Huang, Viviana V. Guzmán, L. Ilsedore Cleeves F Deuterium fractionation provides awindow to the thermal history of volatiles in the solar system and protoplanetary disks. While evidence of active
molecular deuteration has been observed towards a handful of disks, it remains unclear whether this chemistry affects
the composition of forming planetesimals due to limited observational constraints on the radial and vertical distributionof deuterated molecules. To shed light on this question, we introduce new ALMA observations of DCO+ and DCN
J = 2 − 1 at an angular resolution of 0.5” (30 au) and combine them with archival data of higher energy transitions
towards the protoplanetary disk around TW Hya. We carry out a radial excitation analysis assuming both LTE andnon-LTE to localize the physical conditions traced by DCO+ and DCN emission in the disk, thus assessing deuterium
fractionation efficiencies and pathways at different disk locations. We find similar disk-averaged column densities of
1.9 × 1012 and 9.8 × 1011 cm−2 for DCO+ and DCN, with typical kinetic temperatures for both molecules of 20-30K,
indicating a common origin near the comet- and planet-forming midplane. The observed DCO+ /DCN abundance
ratio, combined with recent modeling results, provide tentative evidence of a gas phase C/O enhancement within < 40
au. Observations of DCO+ and DCN in other disks, as well as HCN and HCO+ , will be necessary to place the trends
exhibited by TW Hya in context, and fully constrain the main deuteration mechanisms in disks.

Dust hot spots at 10 au scales around the Class 0 binary IRAS 16293-2422 A: a departure

33. from the passive irradiation model

M. J. Maureira, M. Gong, J. E. Pineda, H. B. Liu, K. Silsbee, P. Caselli, J. Zamponi, D. Segura-Cox, A.
Schmiedeke F Characterizing the physical conditions at disk scales in Class 0 sources is crucial for constraining

the protostellar accretion process and the initial conditions for planet formation. We use ALMA 1.3 mm and 3 mm
observations to investigate the physical conditions of the dust around the Class 0 binary IRAS 16293-2422 A (sep<100 au) down to 10 au scales. The circumbinary material’s spectral index, alpha, has a median of 3.1 and adispersion of 0.2, providing no firm evidence of mm-sizes grains therein. Continuum substructures with brightness
temperature peaks of Tb 60-80 K at 1.3 mm are observed near the disks at both wavelengths. These peaks do
not overlap with strong variations of alpha, indicating they trace high-temperature spots instead of regions withsignificant optical depth variations. The lower limits to the inferred dust temperature in the hot spots are 122, 87
and 49 K. Depending on the assumed dust opacity index, these values can be several times higher. They overlap
with high gas temperatures and enhanced complex organic molecular (COM) emission. This newly resolved dust
temperature distribution is in better agreement with the expectations from mechanical instead of the most commonly
assumed radiative heating. In particular, we find that the temperatures agree with shock heating predictions. Thisevidence and recent studies highlighting accretion heating in Class 0 disks suggest that mechanical heating (shocks,
dissipation powered by accretion, etc.) is important during the early stages and should be considered when modelingand measuring properties of deeply embedded protostars and disks.
1234. Gas accretion onto Jupiter mass planets in discs with laminar accretion flows

R. P. Nelson, E. Lega, A. Morbidelli F (Abridged) Studies have shown that a Jovian mass planet embedded in a

viscous protoplanetary disc (PPD) can accrete gas efficiently through the gap and doubles its mass in ∼ 0.1 Myr. The
planet also migrates inwards on a timescale of ∼ 0.1 Myr. These timescales are short compared to PPD lifetimes,
and raise questions about the origins of cold giant exoplanets. However, PPDs are unlikely to be globally turbulent,and instead they may launch magnetised winds such that accretion towards the star occurs in laminar accretion flows
located in narrow layers near the surfaces of the disc. The aim of this study is to examine the rate at which gas
accretes onto Jovian mass planets that are embedded in layered PPDs. We use 3D hydrodynamical simulations ofplanets embedded in PPDs, in which a constant radial mass flux towards the star of ṁ = 10−8 M yr−1 is sustained.
We consider a classical viscous alpha model, and also models in which an external torque is applied in narrow surface
layers to mimic the effects of a magnetised wind. The accreting layers are parameterised by their column densities
ΣA , and we consider values in the range 0.1 to 10 g cm−2 . The viscous model gives results in agreement with previous
studies. We find the accretion rate onto the planet in the layered models crucially depends on the planet’s ability toblock the wind-induced mass flow. For ΣA = 10 g cm−2 , the planet torque can block the mass flow through the disc,accretion onto the planet is slow, and a mass doubling time of 10 Myr is obtained. For ΣA = 0.1 g cm−2 , accretion isfast and the mass doubling time is 0.2 Myr. Although the radial mass flow through the layered disc models is always
10−8 M yr−1 , adopting different values of ΣA leads to very different gas accretion rates onto gas giant planets.

35. Environmental Effects of Star-Forming Cores on Mass Accretion Rate
Shingo Nozaki, Masahiro N. Machida F We calculate the evolution of cloud cores embedded in different envelopes

to investigate environmental effects on the mass accretion rate onto protostars. As the initial state, we neglect themagnetic field and cloud rotation, and adopt star-forming cores composed of two parts: a centrally condensed core andan outer envelope. The inner core has a critical Bonnor-Ebert density profile and is enclosed by the outer envelope.
We prepare 15 star-forming cores with different outer envelope densities and gravitational radii, within which the gas
flows into the collapsing core, and calculate their evolution until ∼ 2 × 105 yr after protostar formation. The massaccretion rate decreases as the core is depleted when the outer envelope density is low. In contrast, the mass accretion
rate is temporarily enhanced when the outer envelope density is high and the resultant protostellar mass exceeds theinitial mass of the centrally condensed core. Some recent observations indicate that the mass of prestellar cores is too
small to reproduce the stellar mass distribution. Our simulations show that the mass inflow from outside the core
contributes greatly to protostellar mass growth when the core is embedded in a high-density envelope, which could
explain the recent observations.

The evolution of circumstellar discs in the Galactic Centre: an application to the G-

36. clouds

James E. Owen, Douglas N. C. Lin F The Galactic Centre is known to have undergone a recent star formation

episode a few Myrs ago, which likely produced many T Tauri stars hosting circumstellar discs. It has been suggested
that these discs may be the compact and dusty ionized sources identified as “G-clouds”. Given the Galactic Centre’s
hostile environment, we study the possible evolutionary pathways these discs experience. We compute new external
photoevaporation models applicable to discs in the Galactic Centre that account for the sub-sonic launching of thewind and absorption of UV photons by dust. Using evolutionary disc calculations, we find that photoevaporation’s
rapid truncation of the disc causes them to accrete onto the central star rapidly. Ultimately, an accreting circumstellar
disc has a lifetime . 1 Myr, which would fail to live long enough to explain the G-clouds. However, we identify a new
evolutionary pathway for circumstellar discs in the Galactic Centre. Removal of disc material by photoevaporation
prevents the young star from spinning down due to magnetic braking, ultimately causing the rapidly spinning youngstar to torque the disc into a “decretion disc” state which prevents accretion. At the same time, any planetarycompanion in the disc will trap dust outside its orbit, shutting down photoevaporation. The disc can survive for up
to ∼10 Myr in this state. Encounters with other stars are likely to remove the planet on Myr timescales, causing
photoevaporation to restart, giving rise to a G-cloud signature. A giant planet fraction of ∼ 10% can explain thenumber of observed G-clouds.

13spectroscopy of a massive young stellar object in the direction toward the
37. Near-infrared
Galactic Center: XCN and aromatic C-D features
Takashi Onaka, Itsuki Sakon, Takashi Shimonishi F We report near-infrared (2.5–5 micron) long-slit ( 30 arcsec)
spectroscopy of a young stellar object in the direction toward the Galactic center with the Infrared Camera on board
the AKARI satellite. The present target is suggested to be AFGL 2006 based on its very red color and close location.
The spectra show strong absorption features of H2 O and CO2 ices, and emission of HI Br alpha recombination line
and the 3.3 micron band, the latter of which originates from polycyclic aromatic hydrocarbons (PAHs) or materials
containing PAHs. The spectra show a broad, complex absorption feature at 4.65 micron, which is well explainedby a combination of absorption features of CO ice, CO gas, and XCN, and HI Pf beta emission. The spectra also
indicate excess emission at 4.4 micron. The characteristics of the spectra suggest that the object is a massive youngstellar object. The XCN feature shows a good correlation with the Br alpha emission, suggesting that the photolysis
by ultraviolet photons plays an important role in the formation of the XCN carriers, part of which are attributed toOCN− . The 4.4 micron emission shows a good correlation with the 3.3 micron PAH emission, providing supporting
evidence that it comes from the aromatic C-D stretching vibration. The formation of OCN− is of importance for theformation process of prebiotic matter in the interstellar medium (ISM), while the detection of aromatic C-D emission
provides valuable information on the deuteration process of PAHs in the ISM and implications on the hiding site of
the missing deuterium in the ISM.

VII – Investigating the origin of stellar masses: CMF evolution in the
38. ALMA-IMF
W43-MM2&MM3 mini-starburst
Y. Pouteau, F. Motte, T. Nony, M. Gonzalez, I. Joncour, J. -F. Robitaille, G. Busquet, R. Galvan-Madrid, A.
Gusdorf, P. Hennebelle, A. Ginsburg, T. Csengeri, P. Sanhueza, P. Dell’Ova, A. M. Stutz, A. P. M. Towner,
N. Cunningham, F. Louvet, A. Men’shchikov, M. Fernandez-Lopez, N. Schneider, M. Armante, J. Bally, T.
Baug, M. Bonfand, S. Bontemps, L. Bronfman, N. Brouillet, D. Diaz-Gonzalez, F. Herpin, B. Lefloch, H. -L.
Liu, X. Lu, F. Nakamura, Q. Nguyen Luong, F. Olguin, K. Tatematsu, M. Valeille-Manet F Among the mostcentral open questions on the initial mass function (IMF) of stars is the impact of the environment on the shape of thecore mass function (CMF) and thus potentially on the IMF. The ALMA-IMF Large Program aims to investigate thevariations of the core distributions with cloud characteristics, as diagnostic observables of the formation process andevolution. The present study focuses on the W43-MM2&MM3 mini-starburst, whose CMF has been recently foundto be top-heavy with respect to the Salpeter slope. W43-MM2&MM3 is a useful test case for environmental studies
because it harbors a rich cluster containing a statistically significant number of cores, previously characterized in paper
III. We applied a multiscale decomposition technique on the ALMA 1.3 mm and 3 mm continuum images to define
six subregions. For each subregion we characterize the high column density probability distribution function, n-PDF,
shape of the cloud gas using the 1.3 mm image. Using the core catalog, we investigate correlations between the CMF,
n-PDF and core mass segregation. We classify the subregions into different stages of evolution, from quiescent to burst
to post-burst, based on the surface number density of cores, number of outflows, and UCHii presence. The high-mass
end of the subregion CMFs vary from being close to the Salpeter slope (quiescent) to top-heavy (burst and post-burst).
Moreover, the second tail of the n-PDF varies from steep, to flat like observed for the high mass star-forming clouds.
We found that subregions with flat second n-PDF tails display top-heavy CMFs. The CMF may evolve from Salpeter
to top-heavy throughout the star formation process from the quiescent to the burst phase. This scenario raises thequestion of if the CMF might revert again to Salpeter as the cloud approaches the end of its star formation stage, ahypothesis that remains to be tested.

39. Star formation timescale in the molecular filament WB 673

O. L. Ryabukhina, M. S. Kirsanova, C. Henkel, D. S. Wiebe F We present observations of ammonia emission

lines toward the interstellar filament WB 673 hosting the dense clumps WB 673, WB 668, S233-IR and G173.57+2.43.
LTE analysis of the lines allows us to estimate gas kinetic temperature (. 30 K in all the clumps), number density(7 − 17 × 103 cm−3 ), and ammonia column density (≈ 1 − 1.5 × 1015 cm−2 ) in the dense clumps. We find signatures ofcollapse in WB 673 and presence of compact spatially unresolved dense clumps in S233-IR. We reconstruct 1D density
and temperature distributions in the clumps and estimate their ages using astrochemical modelling. Considering CO,
CS, NH3 and N2 H+ molecules (plus HCN and HNC for WB 673), we find a chemical age of tchem = 1 − 3 × 105 yrs
providing the best agreement between the simulated and observed column densities in all the clumps. Therefore, we
consider tchem as the chemical age of the entire filament. A long preceding low-density stage of gas accumulation in the14

astrochemical model would break the agreement between the simulated and observed column densities. We suggestthat rapid star formation over a ∼ 105 yrs timescale take place in the filament.

Significance Mode Analysis (SigMA) for hierarchical structures. An application to the

40. Sco-Cen OB association

Sebastian Ratzenböck, Josefa E. Großschedl, Torsten Möller, João Alves, Immanuel Bomze, Stefan Meingast F

We present a new clustering method, Significance Mode Analysis (SigMA), to extract co-spatial and co-moving stellar
populations from large-scale surveys such as ESA Gaia. The method studies the topological properties of the density
field in the multidimensional phase space. We validate SigMA on simulated clusters and find that it outperforms
competing methods, especially in cases where many clusters are closely spaced. We apply the new method to Gaia
DR3 data of the closest OB association to Earth, Scorpio-Centaurus (Sco-Cen), and find more than 13,000 co-moving
young objects, with about 19% of these having a sub-stellar mass. SigMA finds 37 co-moving clusters in Sco-Cen.
These clusters are independently validated by their narrow HRD sequences and, to a certain extent, by their association
with massive stars too bright for Gaia, hence unknown to SigMA. We compare our results with similar recent work andfind that the SigMA algorithm recovers richer populations, is able to distinguish clusters with velocity differences down
to about 0.5 km s−1 , and reaches cluster volume densities as low as 0.01 sources/pc3 . The 3D distribution of these37 coeval clusters implies a larger extent and volume for the Sco-Cen OB association than typically assumed in theliterature. Additionally, we find the association to be more actively star-forming and dynamically more complex thanpreviously thought. We confirm that the star-forming molecular clouds in the Sco-Cen region, namely, Ophiuchus,
L134/L183, Pipe Nebula, Corona Australis, Lupus, and Chamaeleon, are part of the Sco-Cen The application of SigMA
to Sco-Cen demonstrates that advanced machine learning tools applied to the superb Gaia data allows to construct
an accurate census of the young populations, to quantify their dynamics, and to reconstruct the recent star formation
history of the local Milky Way.

41. Determining Dust Properties in Protoplanetary Disks: SED-derived Masses and Settling With ALMA

Anneliese Rilinger, Catherine Espaillat, Zihua Xin, Álvaro Ribas, Enrique Macías, Sarah Luettgen F We

present spectral energy distribution (SED) modeling of 338 disks around T Tauri stars from eleven star-forming regions, ranging from ∼0.5 to 10 Myr old. The disk masses we infer from our SED models are typically greater thanthose reported from (sub)mm surveys by a factor of 1.5-5, with the discrepancy being generally higher for the more
massive disks. Masses derived from (sub)mm fluxes rely on the assumption that the disks are optically thin at all
millimeter wavelengths, which may cause the disk masses to be underestimated since the observed flux is not sensitive
to the whole mass in the disk; SED models do not make this assumption and thus yield higher masses. Disks withmore absorbing material should be optically thicker at a given wavelength; which could lead to a larger discrepancy
for disks around massive stars when the disk temperature is scaled by the stellar luminosity. We also compare thedisk masses and degree of dust settling across the different star-forming regions and find that disks in younger regions
have more massive disks than disks in older regions, but a similar degree of dust settling. Together, these results
offer potential partial solutions to the "missing" mass problem: disks around T Tauri stars may indeed have enoughmaterial to form planetary systems, though previous studies have underestimated the mass by assuming the disks
to be optically thin; these planetary systems may also form earlier than previously theorized since significant dust
evolution (i.e., settling) is already apparent in young disks.

42. Modelling the CO streamers in the explosive ejection of Orion BN/KL region

Ary Rodríguez-González, Pedro Ruben Rivera-Ortiz, Antonio Castellanos-Ramírez, Alejandro C. Raga, Liliana
Hernández-Martínez, Jorge Cantó, Luis A. Zapata, Fátima Robles-Valdez F We present reactive gasdynamic,

axisymmetric simulations of dense, high velocity clumps for modelling the CO streamers observed in Orion BN/KL.
We have considered 15 chemical species, a cooling function for atomic and molecular gas, and heating through cosmic
rays. Our numerical simulations explore different ejection velocities, interstellar medium density configurations, andCO content. Using the CO density and temperature, we have calculated the CO (J = 2 → 1) emissivity, and havebuilt CO maps and spatially resolved line profiles, allowing us to see the CO emitting regions of the streamers and toobtain position velocity diagrams to compare with observations. We find that in order to reproduce the images andline profiles of the BN/KL CO streamers and H2 fingers, we need to have clumps that first travel within a dense cloud15

core, and then emerge into a lower-density environment.

43. Building the molecular cloud population: the role of cloud mergers

Maya S. Skarbinski, Sarah M. R. Jeffreson, Alyssa A. Goodman F We study the physical drivers of slow molecular
cloud mergers within a simulation of a Milky Way-like galaxy in the moving-mesh code Arepo, and determine theinfluence of these mergers on the mass distribution and star formation efficiency of the galactic cloud population. We
find that 83 per cent of these mergers occur at a relative velocity below 5 km/s, and are associated with large-scaleatomic gas flows, driven primarily by (1) expanding bubbles of hot, ionised gas caused by supernova explosions and (2)galactic rotation. The major effect of these mergers is to aggregate molecular mass into higher-mass clouds: mergers
account for over 50 per cent of the molecular mass contained in clouds of mass M > 2 × 106 Msun. These highmass clouds have higher densities, internal velocity dispersions and instantaneous star formation efficiencies than their
unmerged, lower-mass precursors. As such, the mean instantaneous star formation efficiency in our simulated galaxy,with its merger rate of just 1 per cent of clouds per Myr, is 25 per cent higher than in a similar population of clouds
containing no mergers.

Measuring the 8621 Å Diffuse Interstellar Band in Gaia DR3 RVS Spectra: Obtaining

44. a Clean Catalog by Marginalizing over Stellar Types

Andrew K. Saydjari, Catherine Zucker, J. E. G. Peek, Douglas P. Finkbeiner F Diffuse interstellar bands (DIBs)

are broad absorption features associated with interstellar dust and can serve as chemical and kinematic tracers.
Conventional measurements of DIBs in stellar spectra are complicated by residuals between observations and bestfit stellar models. To overcome this, we simultaneously model the spectrum as a combination of stellar, dust, andresidual components, with full posteriors on the joint distribution of the components. This decomposition is obtainedby modeling each component as a draw from a high-dimensional Gaussian distribution in the data-space (the observed
spectrum) – a method we call "Marginalized Analytic Data-space Gaussian Inference for Component Separation"(MADGICS). We use a data-driven prior for the stellar component, which avoids missing stellar features not included
in synthetic line lists. This technique provides statistically rigorous uncertainties and detection thresholds, which arerequired to work in the low signal-to-noise regime that is commonplace for dusty lines of sight. We reprocess all publicGaia DR3 RVS spectra and present an improved 8621 Å DIB catalog, free of detectable stellar line contamination.
We constrain the rest-frame wavelength to 8623.14 ± 0.087 Å (vacuum), find no significant evidence for DIBs in the
Local Bubble from the 1/6th of RVS spectra that are public, and show unprecedented correlation with kinematic
substructure in Galactic CO maps. We validate the catalog, its reported uncertainties, and biases using synthetic
injection tests. We believe MADGICS provides a viable path forward for large-scale spectral line measurements in thepresence of complex spectral contamination.

45. Heavy-element Accretion by Proto-Jupiter in a Massive Planetesimal Disk, Revisited
Sho Shibata, Ravit Helled, Hiroshi Kobayashi F Planetesimal accretion is a key source for heavy-element enrichment

in giant planets. It has been suggested that Jupiter’s enriched envelope is a result of planetesimal accretion during
its growth assuming it formed in a massive planetesimal disk. In this study, we simulate Jupiter’s formation inthis scenario. We assume in-situ formation and perform N-body simulations to infer the solid accretion rate. We
find that tens-Earth masses of planetesimals can be captured by proto-Jupiter during the rapid gas accretion phase.
However, if several embryos are formed near Jupiter’s core, which is an expected outcome in the case of a massive
planetesimal disk, scattering from the embryos increases the eccentricity and inclination of planetesimals and therefore
significantly reduces the accretion efficiency. We also compare our results with published semi-analytical models andshow that these models cannot reproduce the N-body simulations especially when the planetesimal disk has a large
eccentricity and inclination. We show that when the dynamical evolution of planetesimals is carefully modelled, thetotal mass of captured planetesimals Mcap,tot is 2M⊕ . Mcap,tot . 18M⊕ . The metallicity of Jupiter’s envelope canbe explained by the planetesimal accretion in our massive disk model despite the low accretion efficiency coming fromthe high eccentricity and inclination of planetesimals. Our study demonstrates the importance of detailed modelling ofplanetesimal accretion during the planetary growth and its implications to the heavy-element mass in gaseous planets.

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46. Comets and Planetesimal Formation
Jacob B. Simon, Jürgen Blum, Til Birnstiel, David Nesvorný F In this chapter, we review the processes involvedin the formation of planetesimals and comets. We will start with a description of the physics of dust grain growth andhow this is mediated by gas-dust interactions in planet-forming disks. We will then delve into the various models ofplanetesimal formation, describing how these planetesimals form as well as their resulting structure. In doing so, we
focus on and compare two paradigms for planetesimal formation: the gravitational collapse of particle over-densities(which can be produced by a variety of mechanisms) and the growth of particles into planetesimals via collisional andgravitational coagulation. Finally, we compare the predictions from these models with data collected by the Rosetta
and New Horizons missions and that obtained via observations of distant Kuiper Belt Objects.

Non-ideal magnetohydrodynamic simulations of the first star formation: the effect of

47. ambipolar diffusion

Kenji Eric Sadanari, Kazuyuki Omukai, Kazuyuki Sugimura, Tomoaki Matsumoto, Kengo Tomida F In thepresent-day universe, magnetic fields play such essential roles in star formation as angular momentum transport andoutflow driving, which control circumstellar disc formation/fragmentation and also the star formation efficiency. While
only a much weaker field has been believed to exist in the early universe, recent theoretical studies find that strong
fields can be generated by turbulent dynamo during the gravitational collapse. Here, we investigate the gravitational
collapse of a cloud core (∼ 103 cm−3 ) up to protostar formation (∼ 1020 cm−3 ) by non-ideal magnetohydrodynamics(MHD) simulations considering ambipolar diffusion (AD), the dominant non-ideal effects in the primordial-gas. We
systematically study rotating cloud cores either with or without turbulence and permeated with uniform fields ofdifferent strengths. We find that AD can slightly suppress the field growth by dynamo especially on scales smaller
than the Jeans-scale at the density range 1010 − 1014 cm−3 , while we could not see the AD effect on the temperature
evolution, since the AD heating rate is always smaller than compression heating. The inefficiency of AD makes thefield as strong as 103 − 105 G near the formed protostar, much stronger than in the present-day cases, even in caseswith initially weak fields. The magnetic field affects the inflow motion when amplified to the equipartition levelwith turbulence on the Jeans-scale, although disturbed fields do not launch winds. This might suggest that dynamo
amplified fields have smaller impact on the dynamics in the later accretion phase than other processes such as ionisation
feedback.

Using Molecular Gas Observations to Guide Initial Conditions for Star Cluster Simu-

48. lations

Alison Sills, Steven Rieder, Anne S. M. Buckner, Alvaro Hacar, Simon Portegies Zwart, Paula S. Teixeira F

The earliest evolution of star clusters involves a phase of co-existence of both newly-formed stars, and the gas fromwhich they are forming. Observations of the gas in such regions provide a wealth of data that can inform the simulations which are needed to follow the evolution of such objects forward in time. We present a method for transforming
the observed gas properties into initial conditions for simulations that include gas, stars, and ongoing star formation.
We demonstrate our technique using the Orion Nebula Cluster. Since the observations cannot provide all the necessary
information for our simulations, we make choices for the missing data and assess the impact of those choices. We findthat the results are insensitive to the adopted choices of the gas velocity in the plane of the sky. The properties ofthe surrounding gas cloud (e.g. overall density and size), however, have an effect on the star formation rate and paceof assembly of the resultant star cluster. We also analyze the stellar properties of the cluster and find that the stars
become more tightly clustered and in a stronger radial distribution even as new stars form in the filament.

49. A Census of the Low Accretors. II: Accretion Properties
Thanawuth Thanathibodee, Brandon Molina, Javier Serna, Nuria Calvet, Jesús Hernández, James Muzerolle,
Ramiro Franco-Hernández F Much is known about the processes driving accretion from protoplanetary disks onto

low-mass pre-main-sequence stars (T Tauri stars). Nevertheless, it is unclear how accretion stops. To determine
the accretion properties and their relation to stellar properties and gain insight into the last stages of accretion, we
present a detailed analysis of 24 low and possible accretors, previously identified using the He I λ10830 line. We
model moderate-resolution Hα profiles of these stars using magnetospheric accretion flow models that account forthe chromospheric contribution at the line center. Based on parameters derived from the fits of 20 stars that can be
reproduced with the models, we find a power-law relation between the disk truncation radius and the mass accretion17

rate consistent with predictions from theory and simulations. Comparing the corotation and truncation radii, we findthat most of our targets are accreting in the unstable regime and rule out the propeller as the main process stopping
accretion. For the truncation radius to be the same as the magnetic radius, the dipole magnetic field and/or theefficiency parameter ξ need to be smaller than previously determined, suggesting that higher-order fields dominate in
low accretion rates. Lastly, we determine that the lowest accretion rates that can be detected by Hα line modeling are
1 − 3 × 10−11 M yr−1 for M3 stars and 3 − 5 × 10−11 M yr−1 for K5 stars. These limits are lower than the observed
accretion rates in our sample, suggesting that we have reached a physical lower limit. This limit, Ṁ ∼ 10−10 M yr−1 ,is consistent with EUV-dominated photoevaporation.

BISTRO Observations: Magnetic Field Morphology of Bubbles Associated with
50. JCMTNGC 6334
Mehrnoosh Tahani and the Bistro team F We study the HII regions associated with the NGC 6334 molecular cloud
observed in the sub-millimeter and taken as part of the B-fields In STar-forming Region Observations (BISTRO)
Survey. In particular, we investigate the polarization patterns and magnetic field morphologies associated with these
HII regions. Through polarization pattern and pressure calculation analyses, several of these bubbles indicate thatthe gas and magnetic field lines have been pushed away from the bubble, toward an almost tangential (to the bubble)
magnetic field morphology. In the densest part of NGC 6334, where the magnetic field morphology is similar to anhourglass, the polarization observations do not exhibit observable impact from HII regions. We detect two nested
radial polarization patterns in a bubble to the south of NGC 6334 that correspond to the previously observed bipolarstructure in this bubble. Finally, using the results of this study, we present steps (incorporating computer vision;
circular Hough Transform) that can be used in future studies to identify bubbles that have physically impacted
magnetic field lines.

Modeling the CO outflow in DG Tau B: Swept-up shells versus perturbed MHD disk

51. windA. de Valon, C. Dougados, S. Cabrit, F. Louvet, L. A. Zapata, D. Mardones F The origin of outflows and their
exact impact on disk evolution and planet formation remain crucial open questions. DG Tau B is a Class I protostar
associated with a rotating conical CO outflow and a structured disk. Hence it is an ideal target to study thesequestions. We aim to characterize the morphology and kinematics of the DG Tau B outflow in order to elucidate its
origin and potential impact on the disk. Our analysis is based on Atacama Large Millimeter Array (ALMA) 12CO(2-1)
observations of DG Tau B at 20 au angular resolution. We characterize three different types of substructures in thisoutflow (arches, fingers, and cusps) with apparent acceleration. Wind-driven shell models with a Hubble law fail toexplain these substructures. In contrast, both the morphology and kinematics of the conical flow can be explained bya steady conical magnetohydrodynamic (MHD) disk wind with foot-point radii r0= 0.7-3.4 au, a small magnetic levelarm parameter lambda < 1.6), and quasi periodic brightness enhancements. These might be caused by the impact ofjet bow shocks, source orbital motion caused by a 25 MJ companion at 50 au, or disk density perturbations accretingthrough the wind launching region. The large CO wind mass flux (four times the accretion rate onto the centralstar) can also be explained if the MHD disk wind removes most of the angular momentum required for steady disk
accretion. Our results provide the strongest evidence so far for the presence of massive MHD disk winds in Class I
sources with residual infall, and they suggest that the initial stages of planet formation take place in a highly dynamic
environment.

Formation of pebbles in (gravito-)viscous protoplanetary disks with various turbulent

52. strengths

Eduard I. Vorobyov, Vardan G. Elbakyan, Anders Johansen, Michiel Lambrechts, Aleksandr M. Skliarevskii,
O. P. Stoyanovskaya F Aims. Dust plays a crucial role in the evolution of protoplanetary disks. We study the

dynamics and growth of initially sub-µm dust particles in self-gravitating young protoplanetary disks with various
strengths of turbulent viscosity. We aim to understand the physical conditions that determine the formation and spatial
distribution of pebbles when both disk self-gravity and turbulent viscosity can be concurrently at work. Methods. We
perform the thin-disk hydrodynamics simulations of self-gravitating protoplanetary disks over an initial time periodof 0.5 Myr using the FEOSAD code. Turbulent viscosity is parameterized in terms of the spatially and temporally
constant α-parameter, while the effects of gravitational instability on dust growth is accounted for by calculating the18effective parameter αGI . We consider the evolution of dust component including momentum exchange with gas, dust
self-gravity, and also a simplified model of dust growth. Results. We find that the level of turbulent viscosity strongly
affects the spatial distribution and total mass of pebbles in the disk. The α = 10−2 model is viscosity-dominated,pebbles are completely absent, and dust-to-gas mass ratio deviates from the reference 1:100 value no more than by 30%
throughout the disk extent. On the contrary, the α = 10−3 model and, especially, the α = 10−4 model are dominatedby gravitational instability. The effective parameter α + αGI is now a strongly varying function of radial distance. As
a consequence, a bottle neck effect develops in the innermost disk regions, which makes gas and dust accumulate in aring-like structure. Abridged.

TESS Hunt for Young and Maturing Exoplanets (THYME) IX: a 27 Myr extended

53. population of Lower-Centaurus Crux with a transiting two-planet system

Mackenna L. Wood and the THYME team F We report the discovery and characterization of a nearby ( 85pc), older (27 +/- 3 Myr), distributed stellar population near Lower-Centaurus-Crux (LCC), initially identified bysearching for stars co-moving with a candidate transiting planet from TESS (HD 109833; TOI 1097). We determine
the association membership using Gaia kinematics, color-magnitude information, and rotation periods of candidate
members. We measure it’s age using isochrones, gyrochronology, and Li depletion. While the association is near known
populations of LCC, we find that it is older than any previously found LCC sub-group (10-16 Myr), and distinct in both
position and velocity. In addition to the candidate planets around HD 109833 the association contains four directlyimaged planetary-mass companions around 3 stars, YSES-1, YSES-2, and HD 95086, all of which were previously
assigned membership in the younger LCC. Using the Notch pipeline, we identify a second candidate transiting planetaround HD 109833. We use a suite of ground-based follow-up observations to validate the two transit signals as
planetary in nature. HD 109833 b and c join the small but growing population of <100 Myr transiting planets from
TESS. HD 109833 has a rotation period and Li abundance indicative of a young age (< 100 Myr), but a positionand velocity on the outskirts of the new population, lower Li levels than similar members, and a CMD position below
model predictions for 27 Myr. So, we cannot reject the possibility that HD 109833 is a young field star coincidentally
nearby the population.

54. An ionized outflow in Orion-KL source I?

Melvyn Wright, Tomoya Hirota, Jan Forbrich, Richard Plambeck, John Bally, Ciriaco Goddi, Adam Ginsburg,
Brett A. McGuire F We present images at 6 and 14 GHz of Source I in Orion-KL. At higher frequencies, from 43

to 340 GHz, images of this source are dominated by thermal emission from dust in a 100 AU diameter circumstellar
disk, but at 6 and 14 GHz the emission is elongated along the minor axis of the disk, aligned with the SiO bipolar
outflow from the central object. Gaussian fits to the 6, 14, 43, and 99 GHz images find a component along the disk
minor axis whose flux and length vary with frequency consistent with free-free emission from an ionized outflow. The
data favor a broad outflow from a disk wind, rather than a narrow ionized jet. Source I was undetected in higher
resolution 5 GHz e-MERLIN observations obtained in 2021. The 5-6 GHz structure of SrcI may be resolved out by
the high sidelobe structure of the e-MERLIN synthesized beam, or be time variable.

55. Measuring the Dust Masses of Protoplanetary Disks in Lupus with ALMA: Evidence
that Disks can be Optically Thick at 3 mm

Z. Xin, C. C. Espaillat, A. M. Rilinger, A. Ribas, E. Macias F Accurate disk mass measurements are necessary toconstrain disk evolution and the timescale of planet formation, but such measurements are difficult to make and arevery dependent on assumptions. Here we look at the assumption that the disk is optically thin at radio wavelengths
and the effect of this assumption on measurements of disk dust mass. We model the optical to radio spectral energy
distributions (SEDs) of 41 protoplanetary disks located in the young ( 1-3 Myr old) Lupus star-forming region,
including 0.89 mm, 1.33 mm, and 3 mm flux densities when available. We measure disk dust masses that are 1.5-6
times higher than when using the commonly adopted disk dust mass equation under the assumption of optically thinemission in the (sub-)millimeter. The cause of this discrepancy is that most disks are optically thick at millimeter
wavelengths, even up to 3 mm, demonstrating that observations at longer wavelengths are needed to trace the fully
optically thin emission of disks.

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56. On the Spatial Distribution of CO Structures within CO Molecular Clouds

Lixia Yuan, Ji Yang, Fujun Du, Xunchuan Liu, Yang Su, Qing-Zeng Yan, Xuepeng Chen, Yan Sun, Shaobo
Zhang, Xin Zhou, Yuehui Ma F We look into the 2851 12 CO molecular clouds harboring 13 CO structures to reveal

the distribution of the projected angular separations and radial velocity separations between their internal 13 CO
structures. The projected angular separations are determined using the minimal spanning tree algorithm. We findthat ∼ 50% of the angular separations fall in a narrow range of ∼ 3 – 7 arcmin with a median of ∼ 5 arcmin, andthe corresponding radial velocity separations mainly range from ∼ 0.3 km s−1 to 2.5 km s−1 . The mean and standard
deviation of the angular separations of the internal 13 CO structures within 12 CO clouds appear to be universal,
independent of the 12 CO cloud angular areas and the counts of their internal 13 CO structures. We also reveal a
scaling relation between the 12 CO cloud angular area and its harbored 13 CO structure count. These results suggest
there is a preferred angular separation between 13 CO structures in these 12 CO clouds, considering the distance effects.
According to that, we propose an alternative picture for the assembly and destruction of molecular clouds: there isa fundamental separation for the internal structures of molecular clouds, the build-up and destruction of molecular
clouds proceeds under this fundamental unit.

57. Direct measurements of carbon and sulfur isotope ratios in the Milky Way

Y. T. Yan, C. Henkel, C. Kobayashi, K. M. Menten, Y. Gong, J. S. Zhang, H. Z. Yu, K. Yang, J. J. Xie,
Y. X. Wang F With the IRAM 30 meter telescope, we performed observations of the J = 2-1 transitions of CS,

C33 S, C34 S, C36 S, 13 CS, 13 C33 S, and 13 C34 S as well as the J = 3-2 transitions of C33 S, C34 S, C36 S, and 13 CS
toward a large sample of 110 HMSFRs. We measured the 12 C/13 C, 32 S/34 S, 32 S/33 S, 32 S/36 S, 34 S/33 S, 34 S/36 S, and33
S/36 S abundance ratios with rare isotopologs of CS, thus avoiding significant saturation effects. With accurate
distances obtained from parallax data, we confirm previously identified 12 C/13 C and 32 S/34 S gradients as a functionof galactocentric distance (RGC). In the CMZ, 12 C/13 C ratios are higher than suggested by a linear fit to the disk
values as a function of RGC. While 32 S/34 S ratios near the Galactic center and in the inner disk are similar, this is
not the case for 12 C/13 C, when comparing central values with those near RGC of 5 kpc. As was already known, there
is no 34 S/33 S gradient but the average ratio of 4.35 ± 0.44 derived from the J = 2-1 transition lines of C34 S and C33 S
is well below previously reported values. A comparison between solar and local interstellar 32 S/34 S and 34 S/33 S ratios
suggests that the Solar System may have been formed from gas with a particularly high 34 S abundance. For the firsttime, we report positive gradients of 32 S/33 S, 34 S/36 S, 33 S/36 S, and 32 S/36 S in our Galaxy. The predicted 12 C/13 C
ratios from the latest GCE models are in good agreement with our results. While 32 S/34 S and 32 S/36 S ratios show
larger differences at larger RGC, 32 S/33 S ratios show an offset across the entire inner 12 kpc of the Milky Way.

58. The Solar Neighborhood in the Age of Gaia

Catherine Zucker, João Alves, Alyssa Goodman, Stefan Meingast, Phillip Galli F Most of what we know about
the formation of stars, and essentially everything we know about the formation of planets, comes from observations of
our solar neighborhood within 2 kpc of the Sun. Before 2018, accurate distance measurements needed to turn the 2D
Sky into a faithful 3D physical picture of the distribution of stars, and the interstellar matter that forms them, were few
and far between. Here, we offer a holistic review of how, since 2018, data from the Gaia mission are revealing previously
unseen and often unexpected 3D distributions of gas, dust, and young stars in the solar neighborhood. We summarize
how new extinction-based techniques yield 3D dust maps and how the density structure mapped out offers key context
for measuring young stars’ 3D positions from Gaia and VLBI. We discuss how a subset of young stars in Gaia withmeasured radial velocities and proper motions is being used to recover 3D cloud motion and characterize the internal
dynamics of individual star-forming regions. We review relationships between newly-identified clusters and streams ofyoung stars and the molecular interstellar medium from which they evolve. The combination of these measures of gas
and stars’ 3D distribution and 3D motions provides unprecedented data for comparison with simulations and reframes
our understanding of local star formation in a larger Galactic context. This new 3D view of our solar neighborhood in
the age of Gaia shows that star-forming regions once thought to be isolated are often connected on kiloparsec scales,causing us to reconsider models for the arrangement of gas and young stars in galaxies.

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59. Supervised machine learning on Galactic filaments Revealing the filamentary structureof the Galactic interstellar medium

A. Zavagno, F. -X. Dupé, S. Bensaid, E. Schisano, G. Li Causi, M. Gray, S. Molinari, D. Elia, J. -C. Lambert,
M. Brescia, D. Arzoumanian, D. Russeil, G. Riccio, S. Cavuoti F Context. Filaments are ubiquitous in the

Galaxy, and they host star formation. Detecting them in a reliable way is therefore key towards our understanding of
the star formation process. Aims. We explore whether supervised machine learning can identify filamentary structureson the whole Galactic plane. Methods. We used two versions of UNet-based networks for image segmentation.We
used H2 column density images of the Galactic plane obtained with Herschel Hi-GAL data as input data. We trained
the UNet-based networks with skeletons (spine plus branches) of filaments that were extracted from these images,
together with background and missing data masks that we produced. We tested eight training scenarios to determine
the best scenario for our astrophysical purpose of classifying pixels as filaments. Results. The training of the UNets
allows us to create a new image of the Galactic plane by segmentation in which pixels belonging to filamentary
structures are identified. With this new method, we classify more pixels (more by a factor of 2 to 7, depending on
the classification threshold used) as belonging to filaments than the spine plus branches structures we used as input.
New structures are revealed, which are mainly low-contrast filaments that were not detected before.We use standard
metrics to evaluate the performances of the different training scenarios. This allows us to demonstrate the robustnessof the method and to determine an optimal threshold value that maximizes the recovery of the input labelled pixel
classification. Conclusions. This proof-of-concept study shows that supervised machine learning can reveal filamentary
structures that are present throughout the Galactic plane. The detection of these structures, including low-density
and low-contrast structures that have never been seen before, offers important perspectives for the study of thesefilaments.

60. Hydrodynamic turbulence in disks with embedded planets

Alexandros Ziampras, Wilhelm Kley, Richard P. Nelson F The vertical shear instability (VSI) is a source ofhydrodynamic turbulence that can drive vigorous vertical mixing and moderate levels of accretion in protoplanetarydisks, and it could be observable in the near future. With high-resolution three-dimensional numerical hydrodynamics
simulations, we modeled the behavior of the VSI in protoplanetary disks with and without embedded planets. We thenmeasured its accretion and mixing capabilities by comparing the full Reynolds stress, which includes the contributionof nonaxisymmetric features, such as spiral arms and vortices, to the Reynolds stress due to the azimuthally averaged
velocity field, which can be attributed to good approximation to the VSI. We verified that the VSI can contribute to
the accretion stress and showed that, depending on disk conditions, an embedded planet can coexist with or suppress
VSI turbulent stress. Specifically, the presence of spiral shocks launched by a planet or planet-generated vortices caninterfere with the VSI near the planet’s vicinity, with the instability recovering at large enough distances from theplanet or vortex. Our results suggest that observations of VSI signatures are unlikely in disks that contain massive,
nonaxisymmetric features.

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