The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 354 — 30 June 2022
Editor: João Alveswww.starformation.news

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Cover image caption
30 Dor in the Large Magellanic Cloud (or the Tarantula Nebula) is the most active starburst region in the Local Group ofgalaxies. With an apparent magnitude of 8, 30 Dor is an extremely luminous non-stellar object. The Tarantula Nebula would
cast visible shadows if it were as close to Earth as the Orion Nebula. This composite image background is a series of NIR
images. The bright red-yellow streaks superimposed on the background NIR image come from CO observations taken by
ALMA, revealing complex filamentary networks stretching away approximately, from the central cluster, not unlike an upscaled
version of the Orion Nebula Cluster. Credit: ESO, ALMA (ESO/NAOJ/NRAO)/Wong et al. 2022, ESO/M.-R. Cioni/VISTA
Magellanic Cloud survey.
Note from the Editor
The Star Formation Newsletter is now on the web at www.starformation.news. This PDF file contains the monthly Abstracts
and links to the different Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to the SFN is as simple
as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site. Do not remove the LATEX formatting
when submitting to the arXiv. If you do, your abstract will not look great either at the arXiv or the SFN.

Abstracts
1. The origin of the [CII]-deficit in a simulated dwarf galaxies starburst
Thomas G. Bisbas, Stefanie Walch, Thorsten Naab, Natalia Lahén, Rodrigo Herrera-Camus, Ulrich P. Steinwandel, Constantina M. Fotopoulou, Chia-Yu Hu, Peter H. Johansson F We present [CII] synthetic observations ofsmoothed particle hydrodynamics (SPH) simulations of a dwarf galaxy merger. The merging process varies the star-formation
rate by more than three orders of magnitude. Several star clusters are formed, the feedback of which disperses and unbinds thedense gas through expanding HII regions and supernova (SN) explosions. For galaxies with properties similar to the modelled
ones, we find that the [CII] emission remains optically thin throughout the merging process. We identify the Warm Neutral
Medium (3 < log Tgas < 4 with χHI > 2χH2 ) to be the primary source of [CII] emission (∼ 58% contribution), although atstages when the HII regions are young and dense (during star cluster formation or SNe in the form of ionized bubbles) they
can contribute & 50% to the total [CII] emission. We find that the [CII]/FIR ratio decreases due to thermal saturation of the[CII] emission caused by strong FUV radiation fields emitted by the massive star clusters, leading to a [CII]-deficit medium. We
investigate the [CII]-SFR relation and find an approximately linear correlation which agrees well with observations, particularly
those from the Dwarf Galaxy Survey. Our simulation reproduces the observed trends of [CII]/FIR versus ΣSFR and ΣFIR , andit agrees well with the Kennicutt relation of SFR-FIR luminosity. We propose that local peaks of [CII] in resolved observations
may provide evidence for ongoing massive cluster formation.

Spectroscopy of free-floating planet candidates in Upper Scorpius and Ophi2. Infrareduchus
H. Bouy, M. Tamura, D. Barrado, K. Motohara, N. Castro Rodríguez, N. Miret-Roig, M. Konishi, S. Koyama,
H. Takahashi, N. Huelamo, E. Bertin, J. Olivares, L. M. Sarro, A. Berihuete, J. -C. Cuillandre, P. A. B. Galli,
Y. Yoshii, T. Miyata F Context: A rich population of low-mass brown dwarfs and isolated planetary mass objects has
been reported recently in the Upper Scorpius and Ophiuchus star forming complex. Aims: We investigate the membership,nature and properties of 17 of these isolated planetary mass candidates using low-resolution near-infrared spectra. Methods:
We investigate the membership by looking for evidences of youth using four diagnostics: the slope of the continuum between
the J and Ks band, the Hcont and TLI-g gravity sensitive indices, and by comparing the spectra to young and field (old) M andL-dwarf standards. Results: All the targets but one are confirmed as young ultracool objects, with spectral types between L0
and L6 and masses in the range 0.004-0.013 M according to evolutionary models. The status of the last target is unclear at thispoint. Conclusions: Only one possible contaminant has been identified among the 17 targets, suggesting that the contaminationlevel of the original sample must be lower than 6%2

3. Collisional Charging in the Low Pressure Range of Protoplanetary Disks

T. Becker, T. Steinpilz, J. Teiser, G. Wurm F In recent years, collisional charging has been proposed to promote thegrowth of pebbles in early phases of planet formation. Ambient pressure in protoplanetary disks spans a wide range frombelow 10−9 mbar up to way beyond mbar. Yet, experiments on collisional charging of same material surfaces have only been
conducted under Earth atmospheric pressure, Martian pressure and more generally down to 10−2 mbar thus far. This work
presents first pressure dependent charge measurements of same material collisions between 10−8 and 103 mbar. Strong charging
occurs down to the lowest pressure. In detail, our observations show a strong similarity to the pressure dependence of the
breakdown voltage between two electrodes and we suggest that breakdown also determines the maximum charge on colliding
grains in protoplanetary disks. We conclude that collisional charging can occur in all parts of protoplanetary disks relevant forplanet formation.

4. HCN snowlines in protoplanetary disks: constraints from ice desorption experiments

Jennifer B. Bergner, Mahesh Rajappan, Karin I. Oberg F HCN is among the most commonly detected molecules instar- and planet-forming regions. It is of broad interest as a tracer of star-formation physics, a probe of nitrogen astrochemistry,
and an ingredient in prebiotic chemical schemes. Despite this, one of the most fundamental astrochemical properties of HCN
remains poorly characterized: its thermal desorption behavior. Here, we present a series of experiments to characterize thethermal desorption of HCN in astrophysically relevant conditions, with a focus on predicting the HCN sublimation fronts inprotoplanetary disks. We derive HCN-HCN and HCN-H2O binding energies of 3207±197 K and 4192±68 K, which translate
to disk midplane sublimation temperatures around 85 K and 103 K. For a typical midplane temperature profile, HCN should
only begin to sublimate 1-2 au exterior to the H2O snow line. Additionally, in H2O-dominated mixtures (20:1 H2O:HCN), we
find that the majority of HCN remains trapped in the ice until H2O crystallizes. Thus, HCN may be retained in disk ices atalmost all radii where H2O-rich planetesimals form. This implies that icy body impacts to planetary surfaces should commonly
deliver this potential prebiotic ingredient. A remaining unknown is the extent to which HCN is pure or mixed with H2O inastrophysical ices, which impacts the HCN desorption behavior as well as the outcomes of ice-phase chemistry. Pure HCN and
HCN:H2O mixtures exhibit distinct IR bands, raising the possibility that the James Webb Space Telescope will elucidate themixing environment of HCN in star- and planet-forming regions and address these open questions.

Transit Hunt for Young and Maturing Exoplanets (THYME) VIII: a Pleiades-age as-

5. sociation harboring two transiting planetary systems from Kepler

Madyson G. Barber, Andrew W. Mann, Jonathan L. Bush, Benjamin M. Tofflemire, Adam L. Kraus, Daniel
M. Krolikowski, Andrew Vanderburg, Matthew J. Fields, Elisabeth R. Newton, Dylan A. Owens, Pa Chia Thao
F Young planets provide a window into the early stages and evolution of planetary systems. Ideal planets for such research
are in coeval associations, where the parent population can precisely determine their ages. We describe a young association(MELANGE-3) in the Kepler field, which harbors two transiting planetary systems (Kepler-1928 and Kepler-970). We identify
MELANGE-3 by searching for kinematic and spatial overdensities around Kepler planet hosts with high levels of lithium. To determine the age and membership of MELANGE-3, we combine new high-resolution spectra with archival light curves, velocities,
and astrometry of stars near Kepler-1928 spatially and kinematically. We use the resulting rotation sequence, lithium levels,and color-magnitude diagram of candidate members to confirm the presence of a coeval 105±10 Myr population. MELANGE-3
may be part of the recently identified Theia 316 stream. For the two exoplanet systems, we revise the stellar and planetaryparameters, taking into account the newly-determined age. Fitting the 4.5 yr Kepler light curves, we find that Kepler-1928 b
is a 2.0 ± 0.1R⊕ planet on a 19.58-day orbit, while Kepler-970 b is a 2.8 ± 0.2R⊕ planet on a 16.73-day orbit. Kepler-1928 waspreviously flagged as an eclipsing binary, which we rule out using radial velocities from APOGEE and statistically validate thesignal as planetary in origin. Given its overlap with the Kepler field, MELANGE-3 is valuable for studies of spot evolution on
year timescales, and both planets contribute to the growing work on transiting planets in young stellar associations.

new phase of massive star formation? A luminous outflow cavity centred on an
6. A
infrared quiet core
L. Bonne, N. Peretto, A. Duarte-Cabral, A. Schmiedeke, N. Schneider, S. Bontemps, A. Whitworth F We
present APEX, infrared and radio continuum observations of the G345.88-1.10 hub filament system which is a newly discoveredstar-forming cloud that hosts an unusually bright bipolar infrared nebulosity at its centre. At a distance of 2.26+0.30−0.21 kpc,
G345.88-1.10 exhibits a network of parsec-long converging filaments. At the junction of these filaments lie four infrared-quiet
fragments. The densest fragment (with M=210 M , Reff = 0.14 pc) sits at the centre of a wide (opening angle of ∼ 90±15o )bipolar nebulosity. 12 CO(2-1) observations show that these infrared-bright nebulosities are spatially associated with a powerfulmolecular outflow from the central fragment. Negligible radio continuum and no H30α emission is detected towards the cavities,
seemingly excluding that ionising radiation drives the evolution of the cavities. Furthermore, radiative transfer simulations
are unable to reproduce the observed combination of a low-luminosity (. 500 L ) central source and a surrounding highluminosity (∼ 4000 L ) mid-infrared-bright bipolar cavity. This suggests that radiative heating from a central protostar cannot

3

be responsible for the illumination of the outflow cavities. To our knowledge, this is the first reported object of this type. The
rarity of objects like G345.88-1.10 is likely related to a very short phase in the massive star and/or cluster formation processthat was so far unidentified. We discuss whether mechanical energy deposition by one episode or successive episodes of powerful
mass accretion in a collapsing hub might explain the observations. While promising in some aspects, a fully coherent scenariothat explains the presence of a luminous bipolar cavity centred on an infrared-dark fragment remains elusive at this point.

desorption of complex organic molecules in a hot core: Transition from non7. Resolving
thermal to thermal desorption or two-step thermal desorption?
Laura A. Busch, Arnaud Belloche, Robin T. Garrod, Holger S. P. Müller, Karl M. Menten F Using the highangular resolution provided by the ALMA interferometre we want to resolve the COM emission in the hot molecular core
Sagittarius B2(N1) and thereby shed light on the desorption process of Complex Organic Molecules (COMs) in hot cores. We
use data taken as part of the 3 mm spectral line survey Re-exploring Molecular Complexity with ALMA (ReMoCA) to investigate
the morphology of COM emission in Sagittarius B2(N1). Spectra of ten COMs are modelled under the assumption of LTE andpopulation diagrams are derived for positions at various distances to the south and west from the continuum peak. Based on
this analysis, resolved COM rotation temperature and COM abundance profiles are derived. Based on the morphology, a roughseparation into O- and N-bearing COMs can be done. Temperature profiles are in agreement with expectations of protostellar
heating of an envelope with optically thick dust. Abundance profiles reflect a similar trend as seen in the morphology and, toa great extent, agree with results of astrochemical models that, besides the co-desorption with water, predict that O-bearing
COMs are mainly formed on dust grain surfaces at low temperatures while at least some N-bearing COMs and CH3 CHO are
substantially formed in the gas phase at higher temperatures. Our observational results, in comparison with model predictions,suggest that COMs that are exclusively or to a great extent formed on dust grains desorb thermally at 100 K from thegrain surface likely alongside water. Non-zero abundance values below 100 K suggest that another desorption process is atwork at these low temperatures: either non-thermal desorption or partial thermal desorption related to lower binding energies
experienced by COMs in the outer, water-poor ice layers. In either case, this is the first time that the transition between two
regimes of COM desorption has been resolved in a hot core.

Orbital parameters and activity of ZZ Tau – a low mass young binary with circumbinary

8. disc

A. Belinski, M. Burlak, A. Dodin, N. Emelyanov, N. Ikonnikova, S. Lamzin, B. Safonov, A. Tatarnikov F We
present the results of our new observations of the young binary ZZ Tau with a circumbinary disc. The system was found to
consist of two coeval (age < 2 Myr) classical T Tauri stars with the total mass 0.86 ± 0.09 M , orbital period 46.8 ± 0.8 yr,
semimajor axis 88.2 ± 2.1 mas, eccentricity 0.58 ± 0.02 and the orbital inclination 123.o 8 ± 1.o 0. The accretion rate of ZZ Tau A
and ZZ Tau B are approximately 7×10−10 and 2×10−10 M yr−1 , respectively. No correlation was found between the long-term
photometric variability of ZZ Tau and orbital position of its components. The periodic light variations with P = 4.171 ± 0.002
days was observed in the BV RI bands presumably connected with an accretion (hot) spot on the surface of the primary (ZZ
Tau A). At the same time no periodicity was observed in the U band nor in the emission line profile variations probably due tothe significant contribution of ZZ Tau B’s emission, which dominates shortward of λ ≈ 0.4 µm. We argue that the extinction in
the direction to the primary is noticeably larger than that to the secondary. It appeared that the rotation axis of the primaryis inclined to the line of sight by ≈ 31o ± 4o . We concluded also that ZZ Tau is the source of an CO molecular outflow, however,ZZ Tau IRS rather than ZZ Tau is the source of the Herbig-Haro object HH393.

The signature of large scale turbulence driving on the structure of the interstellar

9. medium

Tine Colman, Jean-François Robitaille, Patrick Hennebelle, Marc-Antoine Miville-Deschênes, Noé Brucy, Ralf
S. Klessen, Simon C. O. Glover, Juan D. Soler, Davide Elia, Alessio Traficante, Sergio Molinari, Leonardo Testi
F The mechanisms that maintain turbulence in the interstellar medium (ISM) are still not identified. This work investigates
how we can distinguish between two fundamental driving mechanisms: the accumulated effect of stellar feedback versus theenergy injection from Galactic scales. We perform a series of numerical simulations describing a stratified star forming ISM
subject to self-consistent stellar feedback. Large scale external turbulent driving of various intensities is added to mimic galactic
driving mechanisms. We analyse the resulting column density maps with a technique called Multi-scale non-Gaussian segmentation that separates the coherent structures and the Gaussian background. This effectively discriminates between the various
simulations and is a promising method to understand the ISM structure. In particular the power spectrum of the coherent
structures flattens above 60 pc when turbulence is driven only by stellar feedback. When large-scale driving is applied, theturn-over shifts to larger scales. A systematic comparison with the Large Magellanic Cloud (LMC) is then performed. Only 1
out of 25 regions has a coherent power spectrum which is consistent with the feedback-only simulation. A detailed study of theturn-over scale leads us to conclude that regular stellar feedback is not enough to explain the observed ISM structure on scales
larger than 60 pc. Extreme feedback in the form of supergiant shells likely plays an important role but cannot explain all the4regions of the LMC. If we assume ISM structure is generated by turbulence, another large scale driving mechanism is needed
to explain the entirety of the observations.

10. The Twisted Magnetic Field of the Protobinary L483

Erin G. Cox, Giles Novak, Sarah Sadavoy, Leslie W. Looney, Dennis Lee, Marc Berthoud, Tyler L. Bourke,
Simon Coudé, Frankie Encalada, Laura M. Fissel, Rachel Harrison, Martin Houde, Zhi-Yun Li, Philip C. Myers,
Kate Pattle, Fabio P. Santos, Ian W. Stephens, Hailin Wang, Sebastian Wolf F We present H-band (1.65 µm) and
SOFIA HAWC+ 154 µm polarization observations of the low-mass core L483. Our H-band observations reveal a magnetic
field that is overwhelmingly in the E-W direction, which is approximately parallel to the bipolar outflow that is observed inscattered IR light and in single-dish 12 CO observations. From our 154 µm data, we infer a ∼ 45◦ twist in the magnetic fieldwithin the inner 5" (1000 au) of L483. We compare these new observations with published single-dish 350 µm polarimetry
and find that the 10,000 au scale H-band data match the smaller scale 350 µm data, indicating that the collapse of L483 ismagnetically regulated on these larger scales. We also present high-resolution 1.3 mm ALMA data of L483 which reveals it isa close binary star with a separation of 34 au. The plane of the binary of L483 is observed to be approximately parallel to thetwisted field in the inner 1000 au. Comparing this result to the ∼ 1000 au protostellar envelope, we find that the envelope isroughly perpendicular to the 1000 au HAWC+ field. Using the data presented, we speculate that L483 initially formed as awide binary and the companion star migrated to its current position, causing an extreme shift in angular momentum thereby
producing the twisted magnetic field morphology observed. More observations are needed to further test this scenario.

of the cyclic C5H radical in TMC-1
11. Discovery
Carlos Cabezas, Marcelino Agundez, Raul Fuentetaja, Yasuki Endo, Nuria Marcelino, Belen Tercero, Juan R.
Pardo, Pablo de Vicente, Jos Cernicharo F Cyclic C5H (c-C5H), the radical formed by substituting an ethynyl group
CCH for the hydrogen atom in the c-C3H radical, has been detected for the first time in the space. The c-C5H species is an
isomer of the well-known linear radical l-C5H and is 6 kcal/mol less stable. A total of 17 rotational transitions were detected forthe c-C5H species in TMC-1 within the 31.0-50.3 GHz range using the Yebes 40m radio telescope. We derive a column densityof (9.0 +/- 0.9)e10 cm-2 for c-C5H. Additionally, we observed 12 lines for l-C5H and derive a column density for it of (1.3 +/0.3)e12 cm-2, which results in an abundance ratio c-C5H/l-C5H of 0.069. This is in sharp contrast with the value found for the
analogue system c-C3H/l-C3H, whose ratio is 5.5 in TMC-1. We discuss the formation of c-C5H and conclude that this radical
is probably formed in the reaction of atomic carbon with diacetylene.

The Doppler-flip in HD100546 as a disk eruption: the elephant in the room of kinematic

12. protoplanet searches

Simon Casassus, Miguel Carcamo, Antonio Hales, Philipp Weber, Bill Dent F The interpretation of molecularline data in terms of hydro dynamical simulations of planet-disk interactions fosters new hopes for the indirect detection of
protoplanets. In a model-independent approach, embedded protoplanets should be found at the roots of abrupt Doppler flips
in velocity centroid maps. However, the largest velocity perturbation known for an unwarped disk, in the disk of HD100546,
leads to a conspicuous Doppler flip that coincides with a thick dust ring, in contradiction with an interpretation in terms ofa > 1Mjup body. Here we present new ALMA observations of the 12CO(2-1) kinematics in HD 100546, with a factor of two
finer angular resolutions. We find that the disk rotation curve is consistent with a central mass 2.1 < M* /Msun < 2.3, andthat the blue-shifted side of the Doppler flip is due to vertical motions, reminiscent of the disk wind proposed previously fromblue-shifted SO lines. We tentatively propose a qualitative interpretation in terms of a surface disturbance to the Keplerian
flow, i.e. a disk eruption, driven by an embedded outflow launched by a 10Mearth body. Another interpretation involves a
disk-mass-loading hot-spot at the convergence of an envelope accretion streamer.

13. Organic chemistry in the first phases of Solar-type protostars

C. Ceccarelli, C. Codella, N. Balucani, D. Bockelée-Morvan, E. Herbst, C. Vastel, P. Caselli, C. Favre, B.
Lefloch, K. Öberg F Planetary systems such as our own are formed after a long process where matter condenses from diffuse
clouds to stars, planets, asteroids, comets and residual dust, undergoing dramatic changes in physical and chemical state in lessthan a few million years. Several studies have shown that the chemical composition during the early formation of a Solar-type
planetary system is a powerful diagnostic to track the history of the system itself. Among the approximately 270 molecules so
far detected in the ISM, the so-called interstellar complex organic molecules (iCOMs) are of particular interest both becauseof their evolutionary diagnostic power and because they might be potential precursors of biomolecules, which are at the basisof terrestrial life. This Chapter focuses on the evolution of organic molecules during the early stages of a Solar-type planetarysystem, represented by the prestellar, Class 0/I and protoplanetary disk phases, and compares them with what is observed
presently in Solar System comets. Our twofold goal is to review the processes at the base of organic chemistry during Solar-typestar formation and, in addition, to possibly provide constraints on the early history of our own planetary system.

5

FAUST VI. VLA 1623–2417 B: a new laboratory for astrochemistry around protostars

14. on 50 au scale

C. Codella, A. López-Sepulcre, S. Ohashi, C. J. Chandler, M. De Simone, L. Podio, C. Ceccarelli, N. Sakai,
F. Alves, A. Durán, D. Fedele, L. Loinard, S. Mercimek, N. Murillo, E. Bianchi, M. Bouvier, G. Busquet,
P. Caselli, F. Dulieu, S. Feng, T. Hanawa, D. Johnstone, B. Lefloch, L. T. Maud, G. Moellenbrock, Y. Oya,B. Svoboda, S. Yamamoto F The ALMA interferometer, with its unprecedented combination of high-sensitivity and highangular resolution, allows for (sub-)mm wavelength mapping of protostellar systems at Solar System scales. Astrochemistry has
benefited from imaging interstellar complex organic molecules in these jet-disk systems. Here we report the first detection of
methanol (CH3OH) and methyl formate (HCOOCH3) emission towards the triple protostellar system VLA1623-2417 A1+A2+B,
obtained in the context of the ALMA Large Program FAUST. Compact methanol emission is detected in lines from Eu = 45 K
up to 61 K and 537 K towards components A1 and B, respectively. LVG analysis of the CH3OH lines towards VLA1623-2417 B
indicates a size of 0.11-0.34 arcsec (14-45 au), a column density N(CH3OH) = 1016 − 1017 cm−2 , kinetic temperature > 170 K,
and volume density > 108 cm−3 . An LTE approach is used for VLA1623-2417 A1, given the limited Eu range, and yields Trot <135 K. The methanol emission around both VLA1623-2417 A1 and B shows velocity gradients along the main axis of each disk.
Although the axial geometry of the two disks is similar, the observed velocity gradients are reversed. The CH3OH spectra from
B shows two broad (4-5 km/s) peaks, which are red- and blue-shifted by about 6-7 km/s from the systemic velocity. Assuming
a chemically enriched ring within the accretion disk, close to the centrifugal barrier, its radius is calculated to be 33 au. The
methanol spectra towards A1 are somewhat narrower (about 4 km/s), implying a radius of 12-24 au.

Stellar collisions in globular clusters: Constraints on the initial mass function of the

15. first generation of stars

Sami Dib, Valery V. Kravtsov, Hosein Haghi, Akram Hasani Zonoozi, José Antonio Belinchón F Globularclusters display an anticorrelation between the fraction of the first generation of stars (N (G1)/N (tot)) and the slope of thepresent-day mass function of the clusters (αpd ), which is particularly significant for massive clusters. In the framework of thebinary-mediated collision scenario for the formation of the second-generation stars in globular clusters, we test the effect ofa varying stellar initial mass function (IMF) of the G1 stars on the (N (G1)/N (tot)) − αpd anticorrelation. We use a simple
collision model that has only two input parameters, the shape of the IMF of G1 stars and the fraction of G1 stars that coalesce
to form second-generation stars. We show that a variable efficiency of the collision process is necessary in order to explain the(N (G1)/N (tot)) − αpd anticorrelation; however, the scatter in the anticorrelation can only be explained by variations in the
IMF, and in particular by variations in the slope in the mass interval ≈ (0.1-0.5) M . Our results indicate that in order toexplain the scatter in the (N (G1)/N (tot)) − αpd relation, it is necessary to invoke variations in the slope in this mass range
between ≈ −0.9 and ≈ −1.9. Interpreted in terms of a Kroupa-like broken power law, this translates into variations in themean mass of between ≈ 0.2 and 0.55 M . This level of variation is consistent with what is observed for young stellar clusters
in the Milky Way and may reflect variations in the physical conditions of the globular cluster progenitor clouds at the time theG1 population formed or may indicate the occurrence of collisions between protostellar embryos before stars settle on the main
sequence.

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

16. stellar disks

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

In-depth direct imaging and spectroscopic characterization of the young Solar System

17. analog HD 95086

C. Desgrange et al. F Context. HD 95086 is a young nearby Solar System analog hosting a giant exoplanet orbiting at
57 au from the star between an inner and outer debris belt. The existence of additional planets has been suggested as themechanism that maintains the broad cavity between the two belts. Aims. We present a dedicated monitoring of HD 95086 with
the VLT/SPHERE instrument to refine the orbital and atmospheric properties of HD 95086 b, and to search for additional
planets in this system. Methods. SPHERE observations, spread over ten epochs from 2015 to 2019 and including five newdatasets, were used. Combined with archival observations, from VLT/NaCo (2012-2013) and Gemini/GPI (2013-2016), theextended set of astrometric measurements allowed us to refine the orbital properties of HD 95086 b. We also investigated thespectral properties and the presence of a circumplanetary disk around HD 95086 b by using the special fitting tool exploring6the diversity of several atmospheric models. In addition, we improved our detection limits in order to search for a putative
planet c via the K-Stacker algorithm. Results. We extracted for the first time the JH low-resolution spectrum of HD 95086
b by stacking the six best epochs, and confirm its very red spectral energy distribution. Combined with additional datasetsfrom GPI and NaCo, our analysis indicates that this very red color can be explained by the presence of a circumplanetary disk
around planet b, with a range of high-temperature solutions (1400-1600 K) and significant extinction (Av > 10 mag), or by asuper-solar metallicity atmosphere with lower temperatures (800-1300 K), and small to medium amount of extinction (Av < 10mag). We do not find any robust candidates for planet c, but give updated constraints on its potential mass and location.

A Multiwavelength Study of the Sgr B Region: Contiguous Cloud-Cloud Collisions

18. Triggering Widespread Star Formation Events?

Rei Enokiya, Yasuo Fukui F The Sgr B region, including Sgr B1 and Sgr B2, is one of the most active star-forming regionsin the Galaxy. Hasegawa et al. (1994) originally proposed that Sgr B2 was formed by a cloud-cloud collision (CCC) between
two clouds with velocities of ∼45 km s−1 and ∼75 km s−1 . However, some recent observational studies conflict with this
scenario. We have re-analyzed this region, by using recent, fully sampled, dense-gas data and by employing a recently developed
CCC identification methodology, with which we have successfully identified more than 50 CCCs and compared them at various
wavelengths. We found two velocity components that are widely spread across this region and that show clear signatures of
a CCC, each with a mass of ∼106 M . Based on these observational results, we suggest an alternative scenario, in which
contiguous collisions between two velocity features with a relative velocity of ∼20 km s−1 created both Sgr B1 and Sgr B2. The
physical parameters, such as the column density and the relative velocity of the colliding clouds, satisfy a relation that has beenfound to apply to the most massive Galactic CCCs, meaning that the triggering of high-mass star formation in the Galaxy andstarbursts in external galaxies can be understood as being due to the same physical CCC process.

Gap opening by planets in discs with magnetised winds

19. Vardan Elbakyan, Yinhao Wu, Sergei Nayakshin, Giovanni Rosotti F Planets open deep gaps in protoplanetary discs
when their mass exceeds a gap opening mass, Mgap . We use one- and two-dimensional simulations to study planet gap opening
in discs with angular momentum transport powered by MHD disc winds. We parameterise the efficiency of the MHD discwind angular momentum transport through a dimensionless parameter αdw , which is an analogue to the turbulent viscosity αv .
We find that magnetised winds are much less efficient in counteracting planet tidal torques than turbulence is. For discs withastrophysically realistic values of αdw , Mgap is always determined by the residual disc turbulence, and is a factor of a few to ten
smaller than usually obtained for viscous discs. We introduce a gap opening criterion applicable for any values of αv and αdw
that may be useful for planet formation population synthesis. We show that in discs powered by magnetised winds, growing
planets detach from the disc at planet masses below ∼ 0.1MJup inside 10 AU. This promotes formation of super-Earth planets
rather than gas giants in this region, in particular precluding formation of hot jupiters in situ. On larger scales, ALMA gap
opening planet candidates may be less massive than currently believed. Future high-resolution observations with instruments
such as the extended ALMA, ngVLA, and SKA are likely to show abundant narrow annular features at R < 10 AU due toubiquitous super-Earth planets.

SIRIUS Project. IV. The formation history of the Orion Nebula Cluster driven by

20. clump mergers

Michiko S. Fujii, Long Wang, Yutaka Hirai, Yoshito Shimajiri, Jun Kumamoto, Takayuki Saitoh F The Orion
Nebula Cluster (ONC) is an excellent example for understanding the formation of star clusters. Recent studies have shown that
ONC has three distinct age populations and anisotropy in velocity dispersions, which are key characteristics for understanding
the formation history of the ONC. In this study, we perform a smoothed-particle hydrodynamics/N -body simulation of starcluster formation from a turbulent molecular cloud. In this simulation, stellar orbits are integrated using a high-order integrator
without gravitational softening; therefore, we can follow the collisional evolution of star clusters. We find that hierarchicalformation causes episodic star formation that is observed in the ONC. In our simulation, star clusters evolve due to mergers
of subclumps. The mergers bring cold gas with the clumps into the forming cluster. This enhances the star formation in thecluster centre. The dense cold gas in the cluster centre continues to form stars until the latest time. This explains the compact
distribution of the youngest stars observed in the ONC. Subclump mergers also contribute to the anisotropy in the velocity
dispersions and the formation of runaway stars. However, the anisotropy disappears within 0.5 Myr. The virial ratio of thecluster also increases after a merger due to the runaways. These results suggest that the ONC recently experienced a clump
merger. We predict that most runaways originated from the ONC have already been found, but walkaways have not.

7

21. The Mysterious Affair of the H2 in AU Mic

Laura Flagg, Christopher Johns-Krull, Kevin France, Gregory Herczeg, Joan Najita, Allison Youngblood,
Adolfo Carvalho, John Carptenter, Scott J. Kenyon, Elisabeth R. Newton, Keighley Rockcliffe F Molecularhydrogen is the most abundant molecule in the Galaxy and plays important roles for planets, their circumstellar environments,and many of their host stars. We have confirmed the presence of molecular hydrogen in the AU Mic system using high-resolution
FUV spectra from HST-STIS during both quiescence and a flare. AU Mic is a ∼23 Myr M dwarf which hosts a debris disk andat least two planets. We estimate the temperature of the gas at 1000 to 2000 K, consistent with previous detections. Based on
the radial velocities and widths of the H2 line profiles and the response of the H2 lines to a stellar flare, the H2 line emission is
likely produced in the star, rather than in the disk or the planet. However, the temperature of this gas is significantly below thetemperature of the photosphere (∼3650 K) and the predicted temperature of its star spots (&2650 K). We discuss the possibilityof colder star spots or a cold layer in the photosphere of a pre-main sequence M dwarf.

Project. V. Formation of off-center ionized bubbles associated with Orion
22. SIRIUS
Nebula Cluster
Michiko S. Fujii, Kohei Hattori, Long Wang, Yutaka Hirai, Jun Kumamoto, Yoshito Shimajiri, Takayuki R.
Saitoh F Massive stars born in star clusters terminate star cluster formation by ionizing the surrounding gas. This process is
considered to be prevalent in young star clusters containing massive stars. The Orion Nebula is an excellent example associatedwith a forming star cluster including several massive stars (the Orion Nebula Cluster; ONC) and a 2-pc size Hii region (ionizedbubble) opening toward the observer; however, the other side is still covered with dense molecular gas. Recent astrometric dataacquired by the Gaia satellite revealed the stellar kinematics in this region. By comparing this data with star cluster formation
simulation results, we demonstrate that massive stars born in the ONC center were ejected via three-body encounters. Further,
orbit analysis indicates that θ2 Ori A, the second massive star in this region, was ejected from the ONC center toward theobserver and is now returning to the cluster center. Such ejected massive stars can form a hole in the dense molecular cloudand contribute to the formation of the 2-pc bubble. Our results demonstrate that the dynamics of massive stars are essential
for the formation of star clusters and Hii regions that are not always centered by massive stars.

23. A detailed temperature map of the archetypal protostellar shocks in L1157
S. Feng, H. B. Liu, P. Caselli, A. Burkhardt, F. Du, R. Bachiller, C. Codella, C. Ceccarelli F We present sensitive
NH3 (1,1)–(7,7) line images from the Karl G. Jansky Very Large Array toward successive shocks, which are associated withthe blueshifted outflow lobe driven by the compact protobinary system L1157. Within a projection distance of 0.1 pc, ourobservations not only trace the quiescent and cold gas in the flattened envelope but also illustrate the complex physical andchemical processes that take place where the high-velocity jet impinges on its surrounding medium. Specifically, the NH3
ortho-to-para ratio is enhanced by a factor of 2–2.5 along the jet path, where the velocity offset between the line peak and theblueshifted wing reaches values as high as 10 km s−1 ; it also shows a strong spatial correlation with the NH3 column density,
which is enhanced to > 1016 cm−2 toward the shock cavities. At a linear resolution of 1500 au, our refined temperature map
from the seven NH3 lines shows a gradient from the warm B0 eastern cavity wall (> 120 K) to the cool cavity B1 and the earlier
shock B2 (< 80 K), indicating shock heating.

activation energy and desorption activation energy for astrochemically relevant
24. Diffusion
species on water ice show no clear relation
Kenji Furuya, Tetsuya Hama, Yasuhiro Oba, Akira Kouchi, Naoki Watanabe, Yuri Aikawa F The activation energy
for desorption (Edes) and that for surface diffusion (Esd) of adsorbed molecules on dust grains are two of the most importantparameters for the chemistry in the interstellar medium. Although Edes is often measured by laboratory experiments, themeasurement of Esd is sparse. Due to the lack of data, astrochemical models usually assume a simple scaling relation, Esd =fEdes, where f is a constant, irrespective of adsorbed species. Here, we experimentally measure Esd for CH4, H2S, OCS, CH3OH,
and CH3CN on water-ice surfaces using an ultra-high-vacuum transmission electron microscope (UHV-TEM). Compiling themeasured Esd values and Edes values from the literature, we find that the value of f ranges from 0.2 to 0.7, depending on thespecies. Unless f (or Esd) for the majority of species is available, a natural alternative approach for astrochemical models is
running multiple simulations, varying f for each species randomly. In this approach, ranges of molecular abundances predictedby multiple simulations, rather than abundances predicted by each simulation, are important. We here run 10,000 simulationsof astrochemical models of molecular clouds and protostellar envelopes, randomly assigning a value of f for each species. In theformer case, we identify several key species whose Esd most strongly affects the uncertainties of the model predictions; Esd for
those species should be investigated in future laboratory and quantum chemical studies. In the latter case, uncertainties in theEsd of many species contribute to the uncertainties in the model predictions.

8

of CH2CCHC4H and a rigorous detection of CH2CCHC3N in TMC-1 with
25. Discovery
the QUIJOTE line survey
R. Fuentetaja, C. Cabezas, M. Agundez, B. Tercero, N. Marcelino, J. R. Pardo, P. de Vicente, J. Cernicharo
F Using the QUIJOTE line survey in the 32.0-50.4 GHz range, we report the discovery of the molecule CH2CCHC4H towards
the prestellar cold core TMC-1 in the Taurus region. We also present a rigorous detection of CH2CCHC3N, along with its
detailed analysis. We identified a total of twenty rotational transitions for each one of these molecules. The rotational quantum
numbers range from Ju=17 up to 24 and Ka<=3. The column density for CH2CCHC4H is N=(2.2+/-0.2)x 1E12 cm-2, while
for CH2CCHC3N, we derived N=(1.2+/-0.15) x 1E11 cm-2. The rotational temperature is 9.0+/-0.5 K for both species. The
abundance ratio between CH2CCHC4H and CH2CCHC3N is 18+/-4. We also compared the column densities of these species
with those of their isomers CH3C6H and CH3C5N, derived from their J=20-19 up to J=30-29 rotational transitions observedwith the QUIJOTE line survey. The observed abundances for all these species are reasonably well explained by state-of-the-art
chemical models of TMC-1. The observed astronomical frequencies were merged with laboratory frequencies from the literature
to derive improved spectroscopic parameters.

Cosmic rays probed by H rovibrational lines: Is chemical modeling important to un-

2
26. derstand JWST H2 observations?

Brandt A. L. Gaches, Shmuel Bialy, Thomas G. Bisbas, Marco Padovani, Daniel Seifried, Stefanie Walch F
Context: It has been proposed that H2 near-infrared lines may be excited by cosmic rays and allow for a determination of thecosmic-ray ionization rate in dense gas. One-dimensional models show that measuring both the H2 gas column density and H2 line
intensity enables a constraint on the cosmic-ray ionization rate as well as the spectral slope of low-energy cosmic-ray protons
in the interstellar medium (ISM). Aims: We aim to investigate the impact of certain assumptions regarding the H2 chemical
models and ISM density distributions on the emission of cosmic-ray induced H2 emission lines. This is of particular importancefor utilizing observations of these lines with the James Webb Space Telescope to constrain the cosmic-ray ionization rate. Methods: We compare the predicted emission from cosmic-ray induced, ro-vibrationally excited H2 emission lines for different oneand three-dimensional models with varying assumptions on the gas chemistry and density distribution. Results: We find thatthe model predictions of the H2 line intensities for the (1-0)S(0), (1-0)Q(2), (1-0)O(2) and (1-0)O(4) transitions at 2.22, 2.41,
2.63 and 3.00 µm, respectively, are relatively independent of the astro-chemical model and the gas density distribution whencompared against the H2 column density, making them robust tracer of the cosmic-ray ionization rate. Conclusions: We recommend the use of ro-vibrational H2 line emission in combination with estimation of the cloud’s H2 column density, to constrain
the ionization rate and the spectrum of low energy cosmic-rays.

Formation of Dust Rings and Gaps in Non-ideal MHD Disks Through Meridional Gas

27. Flows

Xiao Hu, Zhi-Yun Li, Zhaohuan Zhu, Chao-Chin Yang F Rings and gaps are commonly observed in the dust continuum
emission of young stellar disks. Previous studies have shown that substructures naturally develop in the weakly ionized gas ofmagnetized, non-ideal MHD disks. The gas rings are expected to trap large mm/cm-sized grains through pressure gradientinduced radial dust-gas drift. Using 2D (axisymmetric) MHD simulations that include ambipolar diffusion and dust grains of
three representative sizes (1 mm, 3.3 mm, and 1 cm), we show that the grains indeed tend to drift radially relative to the gas
towards the centers of the gas rings, at speeds much higher than in a smooth disk because of steeper pressure gradients. However,their spatial distribution is primarily controlled by meridional gas motions, which are typically much faster than the dust-gas
drift. In particular, the grains that have settled near the midplane are carried rapidly inwards by a fast accretion stream to theinner edges of the gas rings, where they are lifted up by the gas flows diverted away from the midplane by a strong poloidal
magnetic field. The flow pattern in our simulation provides an attractive explanation for the meridional flows recently inferredin HD 163296 and other disks, including both "collapsing" regions where the gas near the disk surface converges towards the
midplane and a disk wind. Our study highlights the prevalence of the potentially observable meridional flows associated withthe gas substructure formation in non-ideal MHD disks and their crucial role in generating rings and gaps in dust.

Chemical and Physical Characterization of the Isolated Protostellar Source CB68: FAUST.

28. IV

Muneaki Imai, Yoko Oya, Brian Svoboda, FAUST members F Chemical diversity of low-mass protostellar sources has
so far been recognized, and environmental effects are invoked as its origin. In this context, observations of isolated protostellar
sources without influences of nearby objects are of particular importance. Here, we report chemical and physical structures ofthe low-mass Class 0 protostellar source IRAS 16544−1604 in the Bok globule CB68, based on 1.3 mm ALMA observations at
a spatial resolution of ∼70 au that were conducted as part of the large program FAUST. Three interstellar saturated complex
organic molecules (iCOMs), CH3 OH, HCOOCH3 , and CH3 OCH3 , are detected toward the protostar. The rotation temperatureand the emitting region size for CH3 OH are derived to be 131 ± 11 K and ∼10 au, respectively. The detection of iCOMs in close
proximity to the protostar indicates that CB68 harbors a hot corino. The kinematic structure of the C18 O, CH3 OH, and OCS

9lines is explained by an infalling-rotating envelope model, and the protostellar mass and the radius of the centrifugal barrier
are estimated to be 0.08 − 0.30 M and < 30 au, respectively. The small radius of the centrifugal barrier seems to be related
to the small emitting region of iCOMs. In addition, we detect emission lines of c-C3 H2 and CCH associated with the protostar,
revealing a warm carbon chain chemistry (WCCC) on a 1000 au scale. We therefore find that the chemical structure of CB68 is
described by a hybrid chemistry. The molecular abundances are discussed in comparison with those in other hot corino sources
and reported chemical models.

Star Formation Activity Beyond the Outer Arm II: Distribution and Properties of Star

29. Formation

Natsuko Izumi, Naoto Kobayashi, Chikako Yasui, Masao Saito, Satoshi Hamano, Patrick M. Koch F The outer
Galaxy beyond the Outer Arm represents a promising opportunity to study star formation in an environment vastly different
from the solar neighborhood. In our previous study, we identified 788 candidate star-forming regions in the outer Galaxy (atgalactocentric radii RG ≥ 13.5 kpc) based on Wide-field Infrared Survey Explorer (WISE) mid-infrared (MIR) all-sky survey.
In this paper, we investigate the statistical properties of the candidates and their parental molecular clouds derived from theFive College Radio Astronomy Observatory (FCRAO) CO survey. We show that the molecular clouds with candidates have ashallower slope of cloud mass function, a larger fraction of clouds bound by self-gravity, and a larger density than the molecular
clouds without candidates. To investigate the star formation efficiency (SFE) at different RG , we used two parameters: 1) the
fraction of molecular clouds with candidates and 2) the monochromatic MIR luminosities of candidates per parental molecular
cloud mass. We did not find any clear correlation between SFE parameters and RG at RG of 13.5 kpc to 20.0 kpc, suggestingthat the SFE is independent of environmental parameters such as metallicity and gas surface density, which vary considerablywith RG . Previous studies reported that the SFE per year (SFE/yr) derived from the star-formation rate surface density per
total gas surface density, HI plus H2 , decreases with increased RG . Our results might suggest that the decreasing trend is due
to a decrease in HI gas conversion to H2 gas.

Statistical properties and correlation length in star-forming molecular clouds: I. For-

30. malism and application to observations

Etienne Jaupart, Gilles Chabrier F The proper characterization of the general statistical behavior of these fluctuations,from a limited sample of observations or simulations, is of prime importance to understand the process of star formation. In
this article, we use the ergodic theory for any random field of fluctuations, as commonly used in statistical physics, to derive
rigorous statistical results. We outline how to evaluate the autocovariance function (ACF) and the characteristic correlation
length of these fluctuations. We then apply this statistical approach to astrophysical systems characterized by a field of density
fluctuations, notably star-forming clouds. When it is difficult to determine the correlation length from the empirical ACF, weshow alternative ways to estimate the correlation length. We show that the statistics of the column-density field is hampered bybiases introduced by integration effects along the line of sight and we explain how to reduce these biases. The statistics of theprobability density function (PDF) ergodic estimator also yields the derivation of the proper statistical error bars. We provide
a method that can be used by observers and numerical simulation specialists to determine the latter. We show that they (i)cannot be derived from simple Poisson statistics and (ii) become increasingly large for increasing density contrasts, severely
hampering the accuracy of the low and high end part of the PDF because of a sample size that is too small. As templates ofvarious stages of star formation in MCs, we then examine the case of the Polaris and Orion B clouds in detail. We calculate,from the observations, the ACF and the correlation length in these clouds and show that the latter is on the order of ∼1% of
the size of the cloud.

properties and correlation length in star-forming molecular clouds: II. Grav31. Statisticalitational potential and virial parameter
Etienne Jaupart, Gilles Chabrier F In the first article of this series, we have used the ergodic theory to assess the validityof a statistical approach to characterize various properties of star-forming molecular clouds (MCs) from a limited number ofobservations or simulations. This allows the proper determination of confidence intervals for various volumetric averages ofstatistical quantities obtained form observations or numerical simulations. In this joint paper, we apply the same formalism toa different kind of (observational or numerical) study of MCs. Indeed, as observations cannot fully unravel the complexity of
the inner density structure of star forming clouds, it is important to know whether global observable estimates, such as the total
mass and size of the cloud, can give an accurate estimation of various key physical quantities that characterize the dynamics ofthe cloud. Of prime importance is the correct determination of the total gravitational (binding) energy and virial parameter ofa cloud. We show that, whereas for clouds that are not in a too advanced stage of star formation, such as Polaris or Orion B,
the knowledge of only their mass and size is sufficient to yield an accurate determination of the aforementioned quantities fromobservations (i.e. in real space). In contrast, we show that this is no longer true for numerical simulations in a periodic box.
We derive a relationship for the ratio of the virial parameter in these two respective cases.

10

trends in the ALMA Taurus survey: Structured inner discs and com32. Super-resolution
pact discs
Jeff Jennings, Marco Tazzari, Cathie J. Clarke, Richard A. Booth, Giovanni P. Rosotti F The 1.33 mm surveyof protoplanetary discs in the Taurus molecular cloud found annular gaps and rings to be common in extended sources (> 55au), when their 1D visibility distributions were fit parametrically. We first demonstrate the advantages and limitations of
nonparametric visibility fits for data at the survey’s 0.12" resolution. Then we use the nonparametric model in Frankenstein(’frank’) to identify new substructure in three compact and seven extended sources. Among the new features we identify threetrends: a higher occurrence rate of substructure in the survey’s compact discs than previously seen, underresolved (potentiallyazimuthally asymmetric) substructure in the innermost disc of extended sources, and a ’shoulder’ on the trailing edge of a ringin discs with strong depletion at small radii. Noting the shoulder morphology is present in multiple discs observed at higher
resolution, we postulate it is tracing a common physical mechanism. We further demonstrate how a super-resolution frankbrightness profile is useful in motivating an accurate parametric model, using the highly structured source DL Tau in whichfrank finds two new rings. Finally we show that sparse (u, v) plane sampling may be masking the presence of substructure inseveral additional compact survey sources.

33. A multiwavelength study of the W33 Main ultracompact HII region

Sarwar Khan, Jagadheep D. Pandian, Dharam V. Lal, Michael R. Rugel, Andreas Brunthaler, Karl M. Menten,
F. Wyrowski, S-N. X. Medina, S. A. Dzib, H. Nguyen F The dynamics of ionized gas around the W33 Main ultracompact
HII region is studied using observations of hydrogen radio recombination lines and a detailed multiwavelength characterizationof the massive star-forming region W33 Main is performed. We used the Giant Meterwave Radio Telescope (GMRT) to observe
the H167α recombination line at 1.4 GHz at an angular resolution of 10 arcsec, and Karl. G. Jansky Very Large Array (VLA)
data acquired in the GLOSTAR survey to study the dynamics of ionized gas. We also observed the radio continuum at 1.4
GHz and 610 MHz with the GMRT and used GLOSTAR 4−8 GHz continuum data to characterize the nature of the radio
emission. In addition, archival data from submillimeter to near-infrared wavelengths were used to study the dust emission andidentify YSOs in the W33 Main star-forming region. The radio recombination lines were detected at good signal to noise in the
GLOSTAR data, while the H167α radio recombination line was marginally detected with the GMRT. The spectral index of radio
emission in the region determined from GMRT and GLOSTAR shows the emission to be thermal in the entire region. Alongwith W33 Main, an arc-shaped diffuse continuum source, G12.81−0.22, was detected with the GMRT data. The GLOSTAR
recombination line data reveal a velocity gradient across W33 Main and G12.81−0.22. The electron temperature is found to be
6343 K and 4843 K in W33 Main and G12.81−0.22, respectively. The physical properties of the W33 Main molecular clump
were derived by modeling the dust emission using data from the ATLASGAL and Hi-GAL surveys and they are consistent withthe region being a relatively evolved site of massive star formation. The gas dynamics and physical properties of G12.81−0.22
are consistent with the HII region being in an evolved phase and its expansion on account of the pressure difference is slowing
down.

34. The morphology of CSCha circumbinary disk suggesting the existence of a Saturn-massplanetN. T. Kurtovic, P. Pinilla, Anna B. T. Penzlin, M. Benisty, L. Pérez, C. Ginski, A. Isella, W. Kley, F. Menard,
S. Pérez, A. Bayo F Planets have been detected in circumbinary orbits in several different systems, despite the additional
challenges faced during their formation in such an environment. We investigate the possibility of planetary formation in the
spectroscopic binary CS Cha by analyzing its circumbinary disk. The system was studied with high angular resolution ALMA
observations at 0.87mm. Visibilities modeling and Keplerian fitting are used to constrain the physical properties of CS Cha,
and the observations were compared to hydrodynamic simulations. Our observations are able to resolve the disk cavity in the
dust continuum emission and the 12CO J:3-2 transition. We find the dust continuum disk to be azimuthally axisymmetric (lessthan 9% of intensity variation along the ring) and of low eccentricity (of 0.039 at the peak brightness of the ring). Under certain
conditions, low eccentricities can be achieved in simulated disks without the need of a planet, however, the combination of low
eccentricity and axisymmetry is consistent with the presence of a Saturn-like planet orbiting near the edge of the cavity.

35. Dynamical star forming history of Per OB2

Marina Kounkel, TingYan Deng, Keivan G. Stassun F We analyze the internal dynamics of young stars towards Perseus
using Gaia EDR3 data, including Per OB2 and California Cloud. Interpreting the current dynamics, we speculate that Per
OB2 may have formed from two separate clouds that have begun forming stars in a close proximity of each other. IC 348 iscaught in the middle between the two of them, inheriting kinematics of both, and it stands out as a possible site of cloud cloudinteraction. We also consider a possibility of a past supernova in Per OB2 - while one had likely occurred, it did not appear
to have caused any obvious triggered star formation, but it has created a shock which has swept away the molecular gas awayfrom IC 348. Finally, we examine a recently proposed shell between Taurus and Perseus. While its origin is unknown, we findno support for an expanding bubble in stellar kinematics, nor can we identify a likely progenitor for a supernova that may have11

caused it, disfavoring this scenario in the formation of this apparent shell.

36. The Role of Magnetic Fields in the Stability and Fragmentation of Filamentary Molecular Clouds: Two Case Studies at OMC-3 and OMC-4

Pak Shing Li, Enrique Lopez-Rodriguez, Archana Soam, Richard I. Klein F We present the stability analysis of two
regions, OMC-3 and OMC-4, in the massive and long molecular cloud complex of Orion A. We obtained 214 µm HAWC+/SOFIA
polarization data, and we make use of archival data for the column density and C18 O (1-0) emission line. We find clear depolarization in both observed regions and that the polarization fraction is anti-correlated with the column density and thepolarization-angle dispersion function. We find that the filamentary cloud and dense clumps in OMC-3 are magnetically supercritical and strongly subvirial. This region should be in the gravitational collapse phase and is consistent with many youngstellar objects (YSOs) forming in the region. Our histogram of relative orientations (HROs) analysis shows that the magnetic
field is dynamically sub-dominant in the dense gas structures of OMC-3. We present the first polarization map of OMC-4. We
find that the observed region is generally magnetically subcritical except for an elongated dense core, which could be a resultof projection effect of a filamentary structure aligned close to the line-of-sight. The relative large velocity dispersion and theunusual positive shape parameters at high column densities in the HROs analysis suggest that our viewing angle may be close toaxes of filamentary substructures in OMC-4. The dominating strong magnetic field in OMC-4 is unfavorable for star formationand is consistent with much fewer YSOs than in OMC-3.

A massive Keplerian protostellar disk with flyby-induced spirals in the Central Molec-

37. ular Zone

Xing Lu, Guang-Xing Li, Qizhou Zhang, Yuxin Lin F Accretion disks are an essential component in the paradigm of theformation of low-mass stars. Recent observations further identify disks surrounding low-mass pre-main-sequence stars perturbed
by flybys. Whether disks around more massive stars evolve in a similar manner becomes an urgent question. We report thediscovery of a Keplerian disk of a few solar masses surrounding a 32 solar-mass protostar in the Sagittarius C cloud around theGalactic Center. The disk is gravitationally stable with two embedded spirals. A combined analysis of analytical solutions andnumerical simulations demonstrates that the most likely scenario to form the spirals is through external perturbations induced
by a close flyby, and one such perturber with the expected parameters is identified. The massive, early O-type star embeddedin this disk forms in a similar manner with respect to low-mass stars, in the sense of not only disk-mediated accretion, but also
flyby-impacted disk evolution.

EDR3 comparative study of protoplanetary disk fractions in young stellar clusters
38. Gaia
I. Mendigutía, E. Solano, M. Vioque, L. Balaguer-Nuñez, A. Ribas, N. Huélamo, C. Rodrigo F (Abridged) The
lifetime of protoplanetary disks around young stars limits the timescale when planets form. A disk dissipation timescale < 10
Myr was inferred from surveys providing the fraction of stars with disks in young stellar clusters with different ages. However,most previous surveys focused on the compact region within 2 pc from the clusters’ centers, for which the disk fraction
information considering the outer part is practically absent. We aim to test if disk fraction estimates change when inferredfrom an extended region around the clusters’ centers. Gaia EDR3 data and a best-suited, Virtual Observatory (VO)-based
tool -Clusterix-, are used to identify member stars for a representative sample of 19 young clusters considering two concentricfields of view (FOV) with radii 20 pc and 2 pc. Our analysis reveals that the inner disk fractions inferred from the compact
and the extended regions are equal within 10%, which does not support a previous hypothesis proposing that disk fractions
should be significantly larger considering extended regions. A list of member and disk stars in each cluster is provided andstored in a VO-compliant archive. Averaged values and plots characterizing the whole clusters are also provided, including HR
diagrams based on Gaia colors and absolute magnitudes. Our results cover the largest fields ever probed when dealing with disk
fractions for all clusters analysed, and imply that their complete characterization requires the use of wide FOVs. The resulting
database is a benchmark for future detailed studies of young clusters, whose disk fractions must be accurately determined byusing multi-wavelength analysis potentially combined with data from coming Gaia releases.

Gas Column Density Distribution of Molecular Clouds in the Third Quadrant of the

39. Milky Way

Yuehui Ma, Hongchi Wang, Miaomiao Zhang, Chen Wang, Shaobo Zhang, Yao Liu, Chong Li, Yuqing Zheng,
Lixia Yuan, Ji Yang F We have obtained column density maps for an unbiased sample of 120 molecular clouds in the third
quadrant of the Milky Way mid-plane (b≤ |5|◦ ) within the galactic longitude range from 195◦ to 225◦ , using the high sensitivity
12
CO and 13 CO (J = 1 − 0) data from the Milky Way Imaging Scroll Painting (MWISP) project. The probability density
functions of the molecular hydrogen column density of the clouds, N-PDFs, are fitted with both log-normal (LN) function and
log-normal plus power-law (LN+PL) function. The molecular clouds are classified into three categories according to their shapesof N-PDFs, i.e., LN, LN+PL, and UN (unclear), respectively. About 72% of the molecular clouds fall into the LN category,

12

0.44
while 18% and 10% into the LN+PL and UN categories, respectively. A power-law scaling relation, σs ∝ NH
, exists between
2
the width of the N-PDF, σs , and the average column density, NH2 , of the molecular clouds. However, σs shows no correlation
with the mass of the clouds. A correlation is found between the dispersion of normalized column density, σN/<N> , and the sonic
Mach number, M, of molecular clouds. Overall, as predicted by numerical simulations, the N-PDFs of the molecular clouds
with active star formation activity tend to have N-PDFs with power-law high-density tails.

snowline locations in protostars: The impact of the structure of protostellar
40. Modelingcloud cores
Nadia M. Murillo, Tien-Hao Hsieh, Catherine Walsh F Abridged Context: Snowlines during star and disk formation
are responsible for a range of effects during the evolution of protostars, such as setting the chemical composition of the envelopeand disk. This in turn influences the formation of planets by changing the elemental compositions of solids and affecting
the collisional properties and outcomes of dust grains. Snowlines can also reveal accretion bursts, providing insight into theformation process of stars. Methods: A numerical chemical network coupled with a grid of cylindrical-symmetric physicalmodels was used to identify what physical parameters alter the CO and H2 O snowline locations. The investigated parameters
are the initial molecular abundances, binding energies of CO and H2 O, heating source, cloud core density, outflow cavity opening
angle, and disk geometry. Simulated molecular line emission maps were used to quantify the change in the snowline location
with each parameter. Conclusions: The models presented in this work show that the CO and H2 O snowline locations do notoccur at a single, well-defined temperature as is commonly assumed. Instead, the snowline position depends on luminosity,
cloud core density, and whether a disk is present or not. Inclination and spatial resolution affect the observability and successful
measurement of snowline locations. We note that N2 H+ and HCO+ emission serve as good observational tracers of CO andH2 O snowline locations. However, constraints on whether or not a disk is present, the observation of additional molecular
tracers, and estimating envelope density will help in accurately determining the cause of the observed snowline position. Plotsof the N2 H+ and HCO+ peak emission radius versus luminosity are provided to compare the models with observations of deeply
embedded protostars aiming to measure the CO and H2 O snowline locations.

41. ALMA Images the Eccentric HD 53143 Debris Disk

Meredith A. MacGregor, Spencer A. Hurt, Christopher C. Stark, Ward S. Howard, Alycia J. Weinberger, Bin
Ren, Glenn Schneider, Elodie Choquet, Dmitri Mawet F We present ALMA 1.3 mm observations of the HD 53143
debris disk - the first infrared or millimeter image produced of this 1 Gyr-old solar-analogue. Previous HST STIS coronagraphic
imaging did not detect flux along the minor axis of the disk which could suggest a face-on geometry with two ’clumps’ of dust.
These ALMA observations reveal a disk with a strikingly different structure. In order to fit models to the millimeter visibilities
and constrain the uncertainties on the disk parameters, we adopt an MCMC approach. This is the most eccentric debris disk
observed to date with a forced eccentricity of 0.21 ± 0.02, nearly twice that of the Fomalhaut debris disk, and also displays
apocenter glow. Although this eccentric model fits the outer debris disk well, there are significant interior residuals remainingthat may suggest a possible edge-on inner disk, which remains unresolved in these observations. Combined with the observed
structure difference between HST and ALMA, these results suggest a potential previous scattering event or dynamical instability
in this system. We also note that the stellar flux changes considerably over the course of our observations, suggesting flaring at
millimeter wavelengths. Using simultaneous TESS observations, we determine the stellar rotation period to be 9.6 ± 0.1 days.

42. Unraveling the observational signatures of cloud-cloud collision and hub-filament systems in W31

A. K. Maity, L. K. Dewangan, H. Sano, K. Tachihara, Y. Fukui, N. K. Bhadari F To understand the formation
process of massive stars, we present a multi-scale and multi-wavelength study of the W31 complex hosting two extended HII
regions (i.e., G10.30-0.15 (hereafter, W31-N) and G10.15-0.34 (hereafter, W31-S)) powered by a cluster of O-type stars. Several
Class I protostars and a total of 49 ATLASGAL 870 µm dust clumps (at d = 3.55 kpc) are found toward the HII regions wheresome of the clumps are associated with the molecular outflow activity. These results confirm the existence of a single physicalsystem hosting the early phases of star formation. The Herschel 250 µm continuum map shows the presence of hub-filament
system (HFS) toward both W31-N and W31-S. The central hubs harbour HII regions and they are depicted with extended
structures (with Td ∼ 25-32 K) in the Herschel temperature map. In the direction of W31-S, an analysis of the NANTEN2
12
CO(J = 1-0) and SEDIGISM 13 CO(J = 2-1) line data supports the presence of two cloud components around 8 and 16 km−1
s , and their connection in velocity space. A spatial complementary distribution between the two cloud components is also
investigated toward W31-S, where the signposts of star formation, including massive O-type stars, are concentrated. Thesefindings favor the applicability of cloud-cloud collision (CCC) around ∼2 Myr ago in W31-S. Overall, our observational findings
support the theoretical scenario of CCC in W31, which explains the formation of massive stars and the existence of HFSs.

13

43. The halo around HD 32297: µm-sized cometary dust

Johan Olofsson, Philippe Thébault, Grant M. Kennedy, Amelia Bayo F The optical properties of the second generation
dust that we observe in debris disks remain quite elusive, whether it is the absorption efficiencies at millimeter wavelengths orthe (un)polarized phase function at near-infrared wavelengths. Thankfully the same particles are experiencing forces that are
size dependent (e.g., radiation pressure), and with high angular resolution observations we can take advantage of this natural
spatial segregation. Observations at different wavelengths probe different ranges of sizes, and there is therefore a great synergy
in multi-wavelength observations to better constrain the optical properties of the particles. We present a new approach tosimultaneously model SPHERE and ALMA observations and apply it to the debris disk around HD 32297, putting the emphasison the spatial distribution of the grains with different β values. This modeling approach requires few assumptions on the actual
sizes of the particles and the interpretation can therefore be done a posteriori. We find that the ALMA observations are best
reproduced with a combination of small and large β values (0.03 and 0.42) while the SPHERE observations require several
intervals of β values. We discuss the nature of the halo previously reported in ALMA observations, and hypothesize it could becaused by over-abundant µm-sized particles (the over-abundance being the consequence of their extended lifetime). We model
the polarized phase function at near-infrared wavelengths and fluffy aggregates larger than a few µm provide the best solution.
Comparing our results with comets of the solar system, we postulate that the particles released in the disk originate from rather
pristine cometary bodies (to avoid compaction of the fluffy aggregates) and are then set on highly eccentric orbits, which could
explain the halo detected at long wavelengths.

of dust clumps with sub-Jupiter mass and cold shadowed region in gravita44. Formation
tionally unstable disk around Class 0/I protostar in L1527 IRS
Satoshi Ohashi, Riouhei Nakatani, Hauyu Baobab Liu, Hiroshi Kobayashi, Yichen Zhang, Tomoyuki Hanawa,
Nami Sakai F We have investigated the protostellar disk around a Class 0/I protostar, L1527 IRS, using multi-wavelength
observations of the dust continuum emission at λ = 0.87, 2.1, 3.3, and 6.8 mm obtained by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Jansky Very Large Array (VLA). Our observations achieved a spatial resolution of
3 − 13 au and revealed an edge-on disk structure with a size of ∼ 80 − 100 au. The emission at 0.87 and 2.1 mm is found to be
optically thick within a projected disk radius of rproj . 50 au. The emission at 3.3 and 6.8 mm shows that the power-law index
of the dust opacity (β) is β ∼ 1.7 around rproj ∼ 50 au, suggesting that grain growth has not yet begun. The dust temperature−2(Tdust ) shows a steep decrease with Tdust ∝ rproj
outside of the VLA clumps previously identified at rproj ∼ 20 au. Furthermore,
the disk is gravitationally unstable at rproj ∼ 20 au, as indicated by a Toomre Q parameter value of Q . 1.0. These results
suggest that the VLA clumps are formed via gravitational instability, which creates a shadow on the outside of the substructure,
resulting in the sudden drop in temperature. The derived dust masses for the VLA clumps are & 0.1 MJ . Thus, we suggestthat Class 0/I disks can be massive enough to be gravitationally unstable, which might be the origin of gas-giant planets in a
20 au radius. Furthermore, the protostellar disks can be cold due to shadowing.

evidence of the significant grain growth but tentative discovery of disk substructure
45. Noin a disk around the Class I Protostar L1489 IRS
Satoshi Ohashi, Hiroshi Kobayashi, Jinshi Sai, Nami Sakai F For revealing the first step of the plant formation, it isimportant to understand how and when dust grains become larger in a disk around a protostar. To investigate the grain growth,
we analyze dust continuum emission toward a disk around the Class I protostar, L1489 IRS at 0.9 and 1.3 mm wavelengths
obtained by the Atacama Large Millimeter/submillimeter Array. The dust continuum emission extends to a disk radius (r) ofr ∼ 300 au, and the spectral index (α) is derived to be α ∼ 3.6 at a radius of r ∼ 100 − 300 au, as similar to the interstellar
dust. Therefore, the grain growth does not occur significantly in the outer disk (r ∼ 100 − 300 au). Furthermore, we tentatively
identify a ring-like substructure at r ∼ 90 au even though the spatial resolution and sensitivity are not enough to determine
this structure. If this is the real ring structure, the ring position and small dust in the disk outer part are consistent with theidea of the growth front. These results suggest that the L1489 protostellar disk may be the beginning of the planet formation.

46. The Effects of Cosmic Rays on the Chemistry of Dense Cores

Ross O’Donoghue, Serena Viti, Marco Padovani, Tomas James F Cosmic rays are crucial for the chemistry of molecular
clouds and their evolution. They provide essential ionizations, dissociations, heating and energy to the cold, dense cores. As
cosmic rays pierce through the clouds they are attenuated and lose energy, which leads to a dependency on the column densityof a system. The detailed effects these particles have on the central regions still needs to be fully understood. Here, werevisit how cosmic rays are treated in the UCLCHEM chemical modeling code by including both ionization rate and H2
dissociation rate dependencies alongside the production of cosmic ray induced excited species and we study in detail theeffects of these treatments on the chemistry of pre-stellar cores. We find that these treatments can have significant effects on
chemical abundances, up to several orders of magnitude, depending on physical conditions. The ionization dependency is themost significant treatment, influencing chemical abundances through increased presence of ionized species, grain desorptions
and enhanced chemical reactions. Comparisons to chemical abundances derived from observations show the new treatments

14reproduce these observations better than the standard handling. It is clear that more advanced treatments of cosmic rays are
essential to chemical models and that including this type of dependency provides more accurate chemical representations.

Low mass young stars in the Milky Way unveiled by DBSCAN and Gaia EDR3. Map-

47. ping the star forming regions within 1.5 Kpc

L. Prisinzano, F. Damiani, S. Sciortino, E. Flaccomio, M. G. Guarcello, G. Micela, E. Tognelli, R. D. Jeffries,
J. M. Alcalá F With an unprecedented astrometric and photometric data precision, Gaia EDR3 gives us, for the first time,
the opportunity to systematically detect and map in the optical bands, the low mass populations of the star forming regions(SFRs) in the Milky Way. We provide a catalogue of the Gaia EDR3 data (photometry, proper motions and parallaxes) of theyoung stellar objects (YSOs) identified in the Galactic Plane (|b|<30 deg) within about 1.5 kpc. The catalogue of the SFRs
to which they belong is also provided to study the properties of the very young clusters and put them in the context of the
Galaxy structure. We applied the machine learning unsupervised clustering algorithm DBSCAN on a sample of Gaia EDR3 data
photometrically selected on the region where very young stars (t<10 Myr) are expected to be found, with the aim to identify
co-moving and spatially consistent stellar clusters. A subsample of 52 clusters, selected among the 7323 found with DBSCAN,
has been used as template data set, to identify very young clusters from the pattern of the observed color-absolute magnitude
diagrams through a pattern match process. We find 124440 candidate YSOs clustered in 354 SFRs and stellar clusters younger
than 10 Myr and within about 1.5 Kpc. In addition, 65863 low mass members of 322 stellar clusters located within about 500
pc and with ages 10 Myr<t<100 Myr were also found. The selected YSOs are spatially correlated with the well known SFRs.
Most of them are associated with well concentrated regions or complex structures of the Galaxy and a substantial number ofthem have been recognized for the first time. The massive SFRs, such as, for example, Orion, Sco-Cen and Vela, located within
600-700 pc trace a very complex three-dimensional pattern, while the farthest ones seem to follow a more regular pattern along
the Galactic Plane.

48. Efficient Dust Radial Drift Around Young Intermediate-mass Stars

Paola Pinilla, Antonio Garufi, Matías Gárate F The radial velocities and direct imaging observations of exoplanets havesuggested that the frequency of giant planets may decrease for intermediate-mass stars (2.5 − 8 M ). The key mechanism that
could hinder their formation remains unclear. From a theoretical point of view, planet formation around intermediate-mass stars
may take place on longer timescales, which – coupled with fast migration and efficient photoevaporation – may prevent planetary
formation in these environments. In this letter, we investigate the temporal evolution of the radial drift for dust particles in disks
when stellar evolution is taken into account. We demonstrate that the particle drift velocity around intermediate-mass stars
sharply increases after 1−2 Myr, potentially forming a difficult barrier to overcome in the first steps of planet formation. Thishigh radial drift could explain the lack of disk detections around intermediate-mass stars older than 3−4 Myr, as opposed to
low-mass stars (< 2.5 M ), where the drift may not be the most impactful factor for the disk evolution. Future high-resolution
images of these disks can help us to explain why planets around intermediate-mass stars may be rare. In addition, we can
explore whether the role of efficient dust radial drift does in fact hinder planet formation around intermediate-mass stars – orotherwise.

The Distributions of Gas, Small-, and Large-grains in the LkHα 330, Disk Trace a Young

49. Planetary System

P. Pinilla, M. Benisty, N. T. Kurtovic, J. Bae, R. Dong, Z. Zhu, S. Andrews, J. Carpenter, C. Ginski, J.
Huang, A. Isella, L. Pérez, L. Ricci, G. Rosotti, M. Villenave, D. Wilner F [abridged] We present new scattered
light and millimeter observations of the protoplanetary disk around LkHα 330, using SPHERE/VLT and ALMA respectively.
The scattered-light SPHERE observations reveal an asymmetric ring at around 45 au distance from the star in addition to
two spiral arms with similar radial launching points at around 90 au. The millimeter observations from ALMA (resolution of0.06”×0.04”) show mainly an asymmetric ring located at 110 au distance from the star. In addition to this asymmetry, there are
two faint symmetric rings at 60 au and 200 au. The 12 CO, 13 CO and C18 O lines seem to be less abundant in the inner disk (theseobservations have a resolution of 0.16”×0.11”). The 13 CO peaks at a location similar to the inner ring observed with SPHERE,
suggesting that this line is optically thick and traces variations of disk temperature instead of gas surface density variations,while the C18 O peaks slightly further away at around 60 au. We compare our observations with hydrodynamical simulations
that include gas and dust evolution, and conclude that a 10 MJup mass planet at 60 au and in an eccentric orbit (e = 0.1) canqualitatively explain most of the observed structures. A planet in a circular orbit leads to a much narrower concentration in
the millimeter emission, while a planet in a more eccentric orbit leads to a very eccentric cavity as well. In addition, the outer
spiral arm launched by the planet changes its pitch angle along the spiral due to the eccentricity and when it interacts withthe vortex, potentially appearing in observations as two distinct spirals. Our observations and models show that LkHα 330, is
an exciting target to search for (eccentric-) planets while they are still embedded in their parental disk, making it an excellent
candidate for studies on planet-disk interaction.

15

50. Large-scale expansion of OB stars in Cygnus

Alexis L. Quintana, Nicholas J. Wright F The proper motions (PMs) of OB stars in Cygnus have recently been found to
exhibit two large-scale kinematic patterns suggestive of expansion. We perform a 3D traceback on these OB stars, the newlyidentified OB associations and related open clusters in the region. We find that there are two groups of stars, associations and+0.8
clusters and that they were each more compact in the past, reaching their closest approach 7.9+3.0−1.8 and 8.5−2.8 Myr ago. We
consider two main scenarios for the driver of these large-scale expansion patterns: feedback-driven expansion from a previous
generation of massive stars, and expansion as a result of the turbulent velocity field in the primordial molecular cloud. While
it is tempting to attribute such large-scale expansion patterns to feedback processes, we find that the observed kinematics are
fully consistent with the turbulent origin, and therefore that the injection of further energy or momentum from feedback is not
required. Similar conclusions may be drawn for other star forming regions with large-scale expansion patterns.

precursors of the RNA-world in space: new nitriles in the G+0.693-0.027
51. Molecularmolecular cloud
Víctor M. Rivilla, Izaskun Jiménez-Serra, Jesus Martín-Pintado, Laura Colzi, Belén Tercero, Pablo de Vicente,
Shaoshan Zeng, Sergio Martín, Juan García de la Concepción, Luca Bizzocchi, Mattia Melosso, Fernando RicoVillas, Miguel A. Requena-Torres F Nitriles play a key role as molecular precursors in prebiotic experiments based on
the RNA-world scenario for the origin of life. These chemical compounds could have been partially delivered to the young
Earth from extraterrestrial objects, stressing the importance of establishing the reservoir of nitriles in the interstellar medium.
We report here the detection towards the molecular cloud G+0.693-0.027 of several nitriles, including cyanic acid (HOCN),
and three C4 H3 N isomers (cyanoallene, CH2 CCHCN; propargyl cyanide, HCCCH2 CN; and cyanopropyne (CH3 CCCN), andthe tentative detections of cyanoformaldehyde (HCOCN), and glycolonitrile (HOCH2 CN). We have also performed the firstinterstellar search of cyanoacetaldehyde (HCOCH2 CN), which was not detected. Based on the derived molecular abundancesof the different nitriles in G+0.693-0.027 and other interstellar sources, we have discussed their formation mechanisms in the
ISM. We propose that the observed HOCN abundance in G+0.693-0.027 is mainly due to surface chemistry and subsequent
shock-induced desorption, while HCOCN might be mainly formed through gas-phase chemistry. In the case of HOCH2 CN,several grain-surface routes from abundant precursors could produce it. The derived abundances of the three C4 H3 N isomers in
G+0.693-0.027 are very similar, and also similar to those previously reported in the dark cold cloud TMC-1. This suggests thatthe three isomers are likely formed through gas-phase chemistry from common precursors, possibly unsaturated hydrocarbons(CH3 CCH and CH2 CCH2 ) that react with the cyanide radical (CN). The rich nitrile feedstock found towards G+0.693-0.027
confirms that interstellar chemistry is able to synthesize in space molecular species that could drive the prebiotic chemistry of
the RNA-world.

52. Turbulent magnetic field in the HII region Sh 2-27

N. C. Raycheva, M. Haverkorn, S. Ideguchi, J. M. Stil, B. M. Gaensler, X. Sun, J. L. Han, E. Carretti, X.
Y. Gao, T. Wijte F Magnetic fields in the turbulent interstellar medium (ISM) are a key element in understanding Galactic
dynamics, but there are many observational challenges. One useful probe for studying the magnetic field component parallelto the line of sight (LoS) is Faraday rotation of linearly polarized radio synchrotron emission, combined with Hα observations.
HII regions are the perfect laboratories to probe such magnetic fields as they are localized in space, and are well-defined sources
often with known distances and measurable electron densities. We chose the HII region Sharpless 2-27 (Sh 2-27). By using a
map of the magnetic field strength along the LoS (Bk ) for the first time, we investigate the basic statistical properties of the
turbulent magnetic field inside Sh 2-27. We study the scaling of the magnetic field fluctuations, compare it to the Kolmogorov
scaling, and attempt to find an outer scale of the turbulent magnetic field fluctuations. We estimate the median value of ne as
7.3 ± 0.1 cm−3 , and the median value of Bk as −4.5 ± 0.1 µG, which is comparable to the magnetic field strength in diffuse ISM.
The slope of the structure function of the estimated Bk -map is found to be slightly steeper than Kolmogorov, consistent with
our Gaussian-random-field Bk simulations revealing that an input Kolmogorov slope in the magnetic field results in a somewhat
steeper slope in Bk . These results suggest that the lower limit to the outer scale of turbulence is 10 pc in the HII region, whichis comparable to the size of the computation domain. This may indicate that the turbulence probed here could actually becascading from the larger scales in the ambient medium, associated with the interstellar turbulence in the general ISM, which
is illuminated by the presence of Sh 2-27.

53. A survey of HDCO and D2 CO towards Class 0/I proto-brown dwarfs

B. Riaz, W. -F. Thi F Deuterium fractionation can constrain the physical and chemical conditions at the early stage ofbrown dwarf formation. We present IRAM 30m observations over a wide frequency range of 213-279 GHz of singly and doubly
deuterated species of formaldehyde (HDCO and D2 CO) towards Class 0/I proto-brown dwarfs (proto-BDs). Multiple lowexcitation HDCO and D2 CO transition lines with upper energy level ≤ 40 K are detected. The D2 CO/HDCO, HDCO/H2 CO,
D2 CO/H2 CO abundance ratios range between 0.01 and 2.5 for the proto-BDs, similar to the range seen in low-mass protostars.
The highest ratios of D2 CO/HDCO ∼1.3-2.5 are measured for two Stage 0 proto-BDs. These objects could possess a warm

16

corino, similar to the few hot corino cases reported among Class 0 protostars. The mean D2 CO/HDCO, D2 CO/H2 CO, andHDCO/H2 CO ratios for the proto-BDs are comparatively higher than the range predicted by the current gas-grain chemical
models, indicating that HDCO and D2 CO are formed via grain surface reactions in the dense and cold interiors of the proto-BDs
at an early formation stage.

Gemini-LIGHTS: Herbig Ae/Be and massive T-Tauri protoplanetary disks imaged with

54. Gemini Planet Imager

Evan A. Rich, John D. Monnier, Alicia Aarnio, Anna S. E. Laws, Benjamin R. Setterholm, David J. Wilner,
Nuria Calvet, Tim Harries, Chris Miller, Claire L. Davies, Fred C. Adams, Sean M. Andrews, Jaehan Bae,
Catherine Espaillat, Alexandra Z. Greenbaum, Sasha Hinkley, Stefan Kraus, Lee Hartmann, Andrea Isella,
Melissa McClure, Rebecca Oppenheimer, Laura M. Pérez, Zhaohuan Zhu F We present the complete sample ofprotoplanetary disks from the Gemini- Large Imaging with GPI Herbig/T-tauri Survey (Gemini-LIGHTS) which observed bright
Herbig Ae/Be stars and T-Tauri stars in near-infrared polarized light to search for signatures of disk evolution and ongoing planet
formation. The 44 targets were chosen based on their near- and mid-infrared colors, with roughly equal numbers of transitional,
pre-transitional, and full disks. Our approach explicitly did not favor well-known, "famous" disks or those observed by ALMA,
resulting in a less-biased sample suitable to probe the major stages of disk evolution during planet formation. Our optimized
data reduction allowed polarized flux as low as 0.002% of the stellar light to be detected, and we report polarized scattered lightaround 80% of our targets. We detected point-like companions for 47% of the targets, including 3 brown dwarfs (2 confirmed,
1 new), and a new super-Jupiter mass candidate around V1295 Aql. We searched for correlations between the polarized flux
and system parameters, finding a few clear trends: presence of a companion drastically reduces the polarized flux levels, far-IR
excess correlates with polarized flux for non-binary systems, and systems hosting disks with ring structures have stellar masses< 3 Msun. Our sample also included four hot, dusty "FS CMa" systems and we detected large-scale (> 100 au) scattered lightaround each, signs of extreme youth for these enigmatic systems. Science-ready images are publicly available through multiple
distribution channels using a new FITS file standard jointly developed with members of the VLT/SPHERE team.

and Near-Infrared Excesses are Correlated in T Tauri Stars
55. Optical
Kendall Sullivan, Adam L. Kraus F Accretion is one of the defining characteristics of classical T Tauri stars, fueled by
the presence of a circumstellar disk comprised of dust and gas. Accretion produces a UV and optical excess, while re-radiatedemission at the inner edge of the dust component of the disk produces a near-infrared (NIR) excess. The interplay between
stars and their disks helps regulate protoplanetary disk evolution and dispersal, which is key to a full understanding of planet
formation. To investigate the relations between NIR excess and optical excess in both single and binary stars, we used anarchival sample of spectroscopically characterized members of the Taurus star-forming region (τ ∼ 1-2 Myr) with measured
luminosities, spectral types, and optical veiling. We combined the archival sample with 2MASS and WISE NIR photometry
and high-resolution imaging surveys. We found that NIR and optical excesses are correlated in multiple NIR photometricbands, suggesting that they are closely related, likely because more massive disks have higher inner dust disk walls and are also
associated with higher accretion rates. We also found that multiplicity has no impact on accretion or inner disk properties ina sample with a wide range of separations, but the sample was too small to specifically investigate close binaries, where theeffects of multiplicity on disk properties should be most significant.

The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emis-

56. sion

Juan D. Soler, Marc-Antoine Miville-Deschênes, Sergio Molinari, Ralf S. Klessen, Patrick Hennebelle, Leonardo
Testi, Naomi M. McClure-Griffiths, Henrik Beuther, Davide Elia, Eugenio Schisano, Alessio Traficante, Philipp
Girichidis, Simon C. O. Glover, Rowan J. Smith, Mattia Sormani, Robin Treß F We present a study of the filamentary structure in the atomic hydrogen (HI) emission at the 21 cm wavelength toward the Galactic plane using the observationsin the HI4PI survey. Using the Hessian matrix method across radial velocity channels, we identified the filamentary structuresand quantified their orientations using circular statistics. We found that the regions of the Milky Way’s disk beyond 10 kpc andup to roughly 18 kpc from the Galactic center display HI filamentary structures predominantly parallel to the Galactic plane.
For regions at lower Galactocentric radii, we found that the HI filaments are mostly perpendicular or do not have a preferredorientation with respect to the Galactic plane. We interpret these results as the imprint of supernova feedback in the inner
Galaxy and Galactic rotation in the outer Milky Way. We found that the HI filamentary structures follow the Galactic warp
and that they highlight some of the variations interpreted as the effect of the gravitational interaction with satellite galaxies.
In addition, the mean scale height of the filamentary structures is lower than that sampled by the bulk of the HI emission, thus
indicating that the cold and warm atomic hydrogen phases have different scale heights in the outer galaxy. Finally, we foundthat the fraction of the column density in HI filaments is almost constant up to approximately 18 kpc from the Galactic center.
This is possibly a result of the roughly constant ratio between the cold and warm atomic hydrogen phases inferred from the HI
absorption studies. Our results indicate that the HI filamentary structures provide insight into the dynamical processes shaping

17

the Galactic disk. Their orientations record how and where the stellar energy input, the Galactic fountain process, the cosmic
ray diffusion, and the gas accretion have molded the diffuse interstellar medium in the Galactic plane.

57. Wavelike nature of the vertical shear instability in global protoplanetary disks

Eleonora Svanberg, Can Cui, Henrik N. Latter F The vertical shear instability (VSI) is a robust phenomenon in irradiatedprotoplanetary disks (PPDs). The majority of previous numerical simulations have focused on the turbulent properties of its
saturated state. However, the saturation of the VSI manifests as large-scale coherent radially travelling inertial waves. In thispaper, we study inertial-wave-disk interactions and their impact on VSI saturation. Inertial-wave linear theory is developed andapplied to a representative global 2D simulation using the Athena++ code. It is found that the VSI saturates by separating thedisk into several radial wave zones roughly demarcated by corotation resonances (turning points); this structure also manifests
in modest radial variations in the vertical turbulence strength. Future numerical work should employ large radial domains toaccommodate this radial structure of the VSI, while concurrently adopting sufficiently fine resolutions to resolve the parametricinstability that attacks the saturated VSI inertial waves.

Pulsational instability of pre-main-sequence models from accreting protostars II. Mod-58. elling echelle diagrams of δ Scuti stars without rotational splitting

T. Steindl, K. Zwintz, M. Müllner F The physics of early stellar evolution (e.g. accretion processes) is often not properly
included in the calculations of pre-main-sequence models, leading to insufficient model grids and hence systematic errors in
the results. We aim to investigate current and improved approaches for the asteroseismic modelling of pre-main-sequence delta
Scuti stars. We calculated an extensive grid of pre-main-sequence models including the early accretion phase and used theresulting equilibrium models as input to calculate theoretical frequency spectra. These spectra were used to investigate different
approaches in modelling echelle diagrams to find the most reliable methods. By applying Petersen diagrams, we present a simple
algorithm to extract echelle diagrams from observed pulsation frequencies. We show that model grids with insufficient input
physics and imperfect modelling approaches lead to underestimated uncertainties and systematic errors in the extracted stellar
parameters. Our re-discussion of HD 139614 leads to different stellar parameters than the ones derived by Murphy et al. (2021).
We performed a model comparison between this previous investigation and our results by applying the Akaike and Bayesian
information criteria. While the results with regard to our 10-d model are inconclusive, they show (very) strong evidence of a
6-d model with fixed accretion parameters (leading to almost identical stellar parameters to those of the 10-d model) to bepreferred over the model applied by Murphy et al. (2021). In general, our modelling approach can provide narrow constraints
on the stellar parameters (∆ R ∼ 0.05 R , ∆ log g < 0.01, and ∆ M? 0.1 M ). The extensively tested modelling approaches
and automatic extraction of echelle diagrams should allow us to study many more pre-main-sequence delta Scuti stars in the
future and lead to reliable stellar parameters.

59. How cooling influences circumbinary discs

Prakruti Sudarshan, Anna B. T. Penzlin, Alexandros Ziampras, Wilhelm Kley, Richard P. Nelson F Circumbinary
disc observations and simulations show large, eccentric inner cavities. Recent work has shown that the shape and size of thesecavities depend on the aspect ratio and viscosity of the disc, as well as the binary eccentricity and mass ratio. It has been further
shown that, for gaps created by planets, the cooling timescale significantly affects the shape and size of the gap. In this study,
we consider the effect of different cooling models on the cavity shape in a circumbinary disc. We compare locally isothermal
and radiatively cooled disc models to ones with a parametrised cooling timescale (β-cooling), implemented in 2D numericalsimulations for varying binary eccentricities. While the shape of the cavity for radiative and locally isothermal models remains
comparable, the inner disc structure changes slightly, leading to a change in the precession rate of the disc. With β-cooledmodels, the shape and size of the cavity changes dramatically towards values of β=1. Based on our findings, we introduce aparametrised β model that accounts for the shorter cooling timescale inside the cavity while adequately reproducing the resultsof the radiative model, and we highlight that accurate treatment of the thermodynamics inside the cavity has a significant
impact in modelling circumbinary systems.

and nonpolytropic astrophysical outflows. XI. Simulations of the circumstel60. Nonradial
lar environment of RY Tau
C. Sauty, R. M. G. de Albuquerque, V. Cayatte, J. J. G. Lima, J. F. Gameiro F Context. There are recent observational evidences that RY Tau may present two different outflow stages, a quiescent one and a more active one. We try to modelthat phenomenon. Aims. We have performed new 2.5D magneto-hydrodynamical simulations of the possible accretion-outflow
environment of RY Tau based on analytical solutions to reduce the relaxation time. Methods. We used as initial conditions theanalytical self-similar solution we used to model the RY Tau micro jet. In the closed field line region of the magnetosphere wehave reversed the direction of the flow and increased the accretion rate by increasing the density and the velocity. We have also
implemented the heating rate and adjusted it according to the velocity of the flow. The accretion disk is treated as a boundary18

condition. Results. The simulations show that the stellar jet and the accreting magnetosphere attain a steady state in only afew stellar rotations, confirming the robustness and stability of self-similar solutions. Additionally, two types of behavior wereobserved similar to the one observed in RY Tau. Either the steady stellar outflow and magnetospheric inflow are separated by a
low static force free region or the interaction between the stellar jet and the magnetospheric accretion creates coronal episodic
mass ejections originating from the disk and bouncing back onto the star. Conclusions. The ratio of mass loss rate to massaccretion rate that coincides with the change of behaviour observed in RY Tau, lays within the range of ratios that have beenmeasured during the period of the micro jet initial analysis.

graph theory-based multi-scale analysis of hierarchical cascade in molecular clouds :61. A
Application to the NGC 2264 region
B. Thomasson, I. Joncour, E. Moraux, C. Crespelle, F. Motte, Y. Pouteau, T. Nony F The spatial properties ofsmall star-clusters suggest that they may originate from a fragmentation cascade of the cloud for which there might be traces
up to a few dozen of kAU. Our goal is to investigate the multi-scale spatial structure of gas clumps, to probe the existence of ahierarchical cascade and to evaluate its possible link with star production in terms of multiplicity. From the Herschel emission
maps of NGC 2264, clumps are extracted using getsf software at each of their associated spatial resolution, respectively [8.4,13.5, 18.2, 24.9, 36.3]". Using the spatial distribution of these clumps and the class 0/I Young Stellar Object (YSO) from
Spitzer data, we develop a graph-theoretic analysis to represent the multi-scale structure of the cloud as a connected network.
From this network, we derive three classes of multi-scale structure in NGC 2264 depending on the number of nodes produced at
the deepest level: hierarchical, linear and isolated. The structure class is strongly correlated with the column density NH2 since
the hierarchical ones dominate the regions whose NH2 > 6 × 1022 cm−2 . Although the latter are in minority, they contain half ofthe class 0/I YSOs proving that they are highly efficient in producing stars. We define a novel statistical metric, the fractality
coefficient F that measure the fractal index describing the scale-free process of the cascade. For NGC 2264, we estimate F= 1.45±0.12. However, a single fractal index fails to fully describe a scale-free process since the hierarchical cascade starts
at a 13 kAU characteristic spatial scale. Our novel methodology allows us to correlate YSOs with their multi-scale gaseousenvironment. This hierarchical cascade that drives efficient star formation is suspected to be both hierarchical and rooted by
the larger-scale gas environment up to 13 kAU.

62. The Musca molecular cloud: The perfect “filament” is still a sheet

A. Tritsis, F. Bouzelou, R. Skalidis, K. Tassis, T. Enßlin, G. Edenhofer F The true 3-dimensional (3D) morphologyof the Musca molecular cloud is a topic that has received significant attention lately. Given that Musca does not exhibit intensestar-formation activity, unveiling its shape has the potential of also revealing crucial information regarding the physics that
dictates the formation of the first generation of stars within molecular clouds. Here, we revisit the shape of Musca and we
present a comprehensive array of evidence pointing towards a shape that is extended along the line-of-sight dimension: (a) 3D
maps of differential extinction; (b) new non-local thermodynamic equilibrium radiative transfer simulations of CO rotationaltransitions from a sheet-like, magnetically-dominated simulated cloud; (c) an effective/critical density analysis of available
CO observations; (d) indirect consequences that a filamentary structure would have had, from a theoretical star-formation
perspective. We conclude that the full collection of observational evidence strongly suggests that Musca has a sheet-likegeometry.

methanol in the [BHB2007] 11 protobinary system: hot corino versus shock origin?
63. Hot: FAUST V
C. Vastel et al. - FAUST team F Methanol is a ubiquitous species commonly found in the molecular interstellar medium.
It is also a crucial seed species for the building-up of the chemical complexity in star forming regions. Thus, understanding how
its abundance evolves during the star formation process and whether it enriches the emerging planetary system is of paramountimportance. We used new data from the ALMA Large Program FAUST (Fifty AU STudy of the chemistry in the disk/envelope
system of Solar-like protostars) to study the methanol line emission towards the [BHB2007] 11 protobinary system (sources A
and B), where a complex structure of filaments connecting the two sources with a larger circumbinary disk has been previously
detected. Twelve methanol lines have been detected with upper energies in the range [45-537] K along with one 13CH3OH
transition. The methanol emission is compact and encompasses both protostars, separated by only 28 au and presents threevelocity components, not spatially resolved by our observations, associated with three different spatial regions, with two of themclose to 11B and the third one associated with 11A. A non-LTE radiative transfer analysis of the methanol lines concludes
that the gas is hot and dense and highly enriched in methanol with an abundance as high as 1e-5. Using previous continuum
data, we show that dust opacity can potentially completely absorb the methanol line emission from the two binary objects.
Although we cannot firmly exclude other possibilities, we suggest that the detected hot methanol is resulting from the shockedgas from the incoming filaments streaming towards [BHB2007] 11 A and B, respectively. Higher spatial resolution observations
are necessary to confirm this hypothesis.

1964. The growth and migration of massive planets under the influence of external photoevaporation

Andrew J. Winter, Thomas J. Haworth, Gavin A. L. Coleman, Sergei Nayakshin F The formation of gas giant
planets must occur during the first few Myr of a star’s lifetime, when the protoplanetary disc still contains sufficient gas to beaccreted onto the planetary core. The majority of protoplanetary discs are exposed to strong ultraviolet irradiation from nearby
massive stars, which drives winds and depletes the mass budget for planet formation. It remains unclear to what degree external
photoevaporation affects the formation of massive planets. In this work, we present a simple one dimensional model for thegrowth and migration of a massive planet under the influence of external FUV fields. We find that even moderate FUV fluxes
FFUV & 100 G0 have a strong influence on planet mass and migration. By decreasing the local surface density and shutting off
accretion onto the planet, external irradiation suppresses planet masses and halts migration early. The distribution of typicalstellar birth environments can therefore produce an anti-correlation between semi-major axis and planet mass, which may explain the apparent decrease in planet occurrence rates at orbital periods Porb & 103 days. Even moderate fluxes FFUV strongly
suppress giant planet formation and inward migration for any initial semi-major axis if the stellar host mass M∗ . 0.5 M ,consistent with findings that massive planet occurrence is much lower around such stars. The outcomes of our prescription for
external disc depletion show significant differences to the current approximation adopted in state-of-the-art population synthesis
models, motivating future careful treatment of this important process.

The 30 Doradus Molecular Cloud at 0.4 pc Resolution with the Atacama Large Mil-65. limeter/submillimeter Array: Physical Properties and the Boundedness of CO-emitting
Structures
Tony Wong, Luuk Oudshoorn, Eliyahu Sofovich, Alex Green, Charmi Shah, Rémy Indebetouw, Margaret
Meixner, Alvaro Hacar, Omnarayani Nayak, Kazuki Tokuda, Alberto D. Bolatto, Mélanie Chevance, Guido De
Marchi, Yasuo Fukui, Alec S. Hirschauer, K. E. Jameson, Venu Kalari, Vianney Lebouteiller, Leslie W. Looney,
Suzanne C. Madden, Toshikazu Onishi, Julia Roman-Duval, Mónica Rubio, A. G. G. M. Tielens F We present
results of a wide-field (approximately 60 x 90 pc) ALMA mosaic of CO(2-1) and 13 CO(2-1) emission from the molecular cloud
associated with the 30 Doradus star-forming region. Three main emission complexes, including two forming a bowtie-shaped
structure extending northeast and southwest from the central R136 cluster, are resolved into complex filamentary networks.
Consistent with previous studies, we find that the central region of the cloud has higher line widths at fixed size relative to therest of the molecular cloud and to other LMC clouds, indicating an enhanced level of turbulent motions. However, there is noclear trend in gravitational boundedness (as measured by the virial parameter) with distance from R136. Structures observedin 13 CO are spatially coincident with filaments and are close to a state of virial equilibrium. In contrast, CO structures vary
greatly in virialization, with low CO surface brightness structures outside of the main filamentary network being predominantly
unbound. The low surface brightness structures constitute 10remnants of previously star-forming gas clumps, or alternatively
the CO-emitting parts of more massive, CO-dark structures.

A new method for direct measurement of isotopologue ratios in protoplanetary disks:

66. a case study of the 12 CO/13 CO ratio in the TW Hya disk

Tomohiro C. Yoshida, Hideko Nomura, Kenji Furuya, Takashi Tsukagoshi, Seokho Lee F Planetary systems
are thought to be born in protoplanetary disks. Isotope ratios are a powerful tool for investigating the material origin andevolution from molecular clouds to planetary systems via protoplanetary disks. However, it is challenging to measure theisotope (isotopologue) ratios, especially in protoplanetary disks, because the emission lines of major species are saturated. We
developed a new method to overcome these challenges by using optically thin line wings induced by thermal broadening. Asa first application of the method, we analyzed two carbon monoxide isotopologue lines, 12 CO 3 − 2 and 13 CO 3 − 2, fromarchival observations of a protoplanetary disk around TW Hya with the Atacama Large Millimeter/sub-millimeter Array. The
12
CO/13 CO ratio was estimated to be 20 ± 5 at disk radii of 70 − 110 au, which is significantly smaller than the value observedin the local interstellar medium, ∼ 69. It implies that an isotope exchange reaction occurs in a low-temperature environment
with C/O > 1 . In contrast, it is suggested that 12 CO/13 CO is higher than ∼ 84 in the outer disk (r > 130 au), which can be
explained by the difference in the binding energy of the isotopologues on dust grains and the CO gas depletion processes. Our
results imply that the gas-phase 12 CO/13 CO can vary by a factor of > 4 even inside a protoplanetary disk, and therefore, canbe used to trace material evolution in disks.

Molecular Gas Structures traced by 13 CO Emission in the 18,190 12 CO Molecular Clouds
67. from the MWISP Survey
Lixia Yuan, Ji Yang, Fujun Du, Yang Su, Xunchuan Liu, Shaobo Zhang, Yan Sun, Xin Zhou, Qing-Zeng Yan,
Yuehui Ma F After the morphological classification of the 18,190 12 CO molecular clouds, we further investigate the propertiesof their internal molecular gas structures traced by the 13 CO(J = 1−0) line emissions. Using three different methods to extract20

the 13 CO gas structures within each 12 CO cloud, we find that ∼ 15% of 12 CO clouds (2851) have 13 CO gas structures and these12
CO clouds contribute about 93% of the total integrated flux of 12 CO emission. In each of 2851 12 CO clouds with 13 CO gas
structures, the 13 CO emission area generally does not exceed 70% of the 12 CO emission area, and the 13 CO integrated flux does
not exceed 20% of the 12 CO integrated flux. We reveal a strong correlation between the velocity-integrated intensities of 12 COlines and those of 13 CO lines in both 12 CO and 13 CO emission regions. This indicates the H2 column densities of molecular
clouds are crucial for the 13 CO lines emission. After linking the 13 CO structure detection rates of the 18,190 12 CO molecular
clouds to their morphologies, i.e. nonfilaments and filaments, we find that the 13 CO gas structures are primarily detectedin the 12 CO clouds with filamentary morphologies. Moreover, these filaments tend to harbor more than one 13 CO structure.
That demonstrates filaments not only have larger spatial scales, but also have more molecular gas structures traced by 13 COlines, i.e. the local gas density enhancements. Our results favor the turbulent compression scenario for filament formation, in
which dynamical compression of turbulent flows induces the local density enhancements. The nonfilaments tend to be in the
low-pressure and quiescent turbulent environments of the diffuse interstellar medium.

of Molecular Cloud Samples on Angular Resolution, Sensitivity, and Algo68. Dependence
rithmsQing-Zeng Yan, Ji Yang, Yang Su, Yan Sun, Xin Zhou, Ye Xu, Hongchi Wang, Shaobo Zhang, Zhiwei Chen
F In this work, we investigate the observational and algorithmic effects on molecular cloud samples identified from positionposition-velocity (PPV) space. By smoothing and cutting off the high quality data of the Milky Way Imaging Scroll Painting(MWISP) survey, we extract various molecular cloud samples from those altered data with the DBSCAN (density-based spatial
clustering of applications with noise) algorithm. Those molecular cloud samples are subsequently used to gauge the significance of sensitivity, angular/velocity resolution, and DBSCAN parameters. Two additional surveys, the FCRAO Outer Galaxy
Survey (OGS) and the CfA-Chile 1.2 m complete CO (CfA-Chile) survey, are used to verify the MWISP results. We foundthat molecular cloud catalogs are not unique and the boundary and therefore the number shows strong variation with angularresolution and sensitivity. At low angular resolution (large beam sizes), molecular clouds merge together in PPV space, while
low sensitivity (high cutoffs) misses small faint molecular clouds and takes bright parts of large molecular clouds as single ones.
At high angular resolution and sensitivity, giant molecular clouds (GMCs) are resolved into individual clouds, and their diffuse
components are also revealed. Consequently, GMCs are more appropriately interpreted as clusters or aggregates of molecular
clouds, i.e., GMCs represent molecular cloud samples themselves.

69. Two Candidate KH 15D-like Systems from the Zwicky Transient Facility

Wei Zhu, Klaus Bernhard, Fei Dai, Min Fang, J. J. Zanazzi, Weicheng Zang, Subo Dong, Franz-Josef Hambsch,
Tianjun Gan, Zexuan Wu, Michael Poon F KH 15D contains a circumbinary disk that is tilted relative to the orbital
plane of the central binary. The precession of the disk and the orbital motion of the binary together produce rich phenomena in
the photometric light curve. In this work, we present the discovery and preliminary analysis of two objects that resemble the key
features of KH 15D from the Zwicky Transient Facility. These new objects, Bernhard-1 and Bernhard-2, show large-amplitude(> 1.5 mag), long-duration (more than tens of days), and periodic dimming events. A one-sided screen model is developed
to model the photometric behaviour of these objects, the physical interpretation of which is a tilted, warped circumbinary
disk occulting the inner binary. Changes in the object light curves suggest potential precession periods over timescales longer
than 10 years. Additional photometric and spectroscopic observations are encouraged to better understand the nature of theseinteresting systems.

70. Magnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I.
Orion A

Mengke Zhao, Jianjun Zhou, Yue Hu, A. Lazarian, Xindi Tang, Willem A. Baan, Jarken Esimbek, Yuxin He,
Dalei Li, Weiguang Ji, Kadirya Tursun F Magnetic fields play an important role in the evolution of molecular clouds
and star formation. Using the Velocity Gradient Technique (VGT) model, we measured the magnetic field in Orion A using
the 12CO, 13CO, and C18O (1-0) emission lines at a scale of 0.07 pc. The measured B-field shows an east-west orientationthat is perpendicular to the integral shaped filament of Orion A at large scale. The VGT magnetic fields obtained from 13CO
and C18O are in agreement with the B-field that is measured from the Planck 353 GHz dust polarization at a scale of 0.55 pc.
Removal of density effects by using a Velocity Decomposition Algorithm can significantly improve the accuracy of the VGT in
tracing magnetic fields with the 12CO (1-0) line. The magnetic field strength of seven sub-clouds, OMC-1, OMC-2, OMC-3,
OMC-4, OMC-5, L 1641-N, and NGC 1999 has also been estimated with the Davis-Chandrasekhar-Fermi (DCF) and MM2technique, and these are found to be in agreement with previous results obtained from dust polarization at far-infrared andsub-millimeter wavelengths. At smaller scales, the VGT proves a good method to measure magnetic fields.

21

ALMA Three-millimeter Observations of Massive Star-forming regions – XI.
71. ATOMS:
From inflow to infall in hub-filament systems
Jian-Wen Zhou et al. F We investigate the presence of hub-filament systems in a large sample of 146 active proto-clusters,
using H13 CO+ J=1-0 molecular line data obtained from the ATOMS survey. We find that filaments are ubiquitous in protoclusters, and hub-filament systems are very common from dense core scales (∼0.1 pc) to clump/cloud scales (∼1-10 pc). The
proportion of proto-clusters containing hub-filament systems decreases with increasing dust temperature (Td ) and luminosityto-mass ratios (L/M ) of clumps, indicating that stellar feedback from Hii regions gradually destroys the hub-filament systems
as proto-clusters evolve. Clear velocity gradients are seen along the longest filaments with a mean velocity gradient of 8.71 km
s−1 pc−1 and a median velocity gradient of 5.54 km s−1 pc−1 . We find that velocity gradients are small for filament lengths larger
than ∼1 pc, probably hinting at the existence of inertial inflows, although we cannot determine whether the latter are driven bylarge-scale turbulence or large-scale gravitational contraction. In contrast, velocity gradients below ∼1 pc dramatically increase
as filament lengths decrease, indicating that the gravity of the hubs or cores starts to dominate gas infall at small scales. We
suggest that self-similar hub-filament systems and filamentary accretion at all scales may play a key role in high-mass starformation.

72. The Pre-main Sequence: Challenges and Prospects for Asteroseismology

Konstanze Zwintz, Thomas Steindl F Stars do not simply pop up on the main sequence. Before the stars arrive on thezero-age main sequence, they form in the collapses of molecular clouds, gain matter through accretion processes, and compress
their cores until hydrogen can burn in full equilibrium. Although this evolutionary phase lasts a relatively short time, it is theimprint of these important physical processes that is often ignored by simplified assumptions. While asteroseismology offers agreat tool to investigate these physical processes, studying pre-MS oscillations in turn has the potential to further advance thefield. Asteroseismology of pre-main sequence stars faces observational and theoretical challenges. The remnants of their birthenvironment which is often still surrounding the young stars causes variability that can interfere with the signal of pulsations.
The lack of long time-base satellite observations in addition limits the applications of the method. Theoretical models of premain sequence stars include several assumptions and simplifications that influence the calculation of pulsation frequencies andexcitation properties of pulsation modes. Keeping all this in mind, the prospects for pre-main sequence asteroseismology are
manifold. An improved understanding of the structure of young stellar objects has the potential to answer some of the open
questions of stellar evolution, including angular momentum transport and the formation of magnetic fields. While gyrochronology, for example, struggles to determine the ages of the youngest clusters, pulsations in pre-main sequence stars can function as
an independent age indicator yielding higher precision for single stars. The increasing interest of stellar astrophysics in general
to investigate the formation and early evolution of stars and planets illustrates the growing importance of pre-main sequence
asteroseismology.

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