The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 364 — 26 April 2023
Editor: João Alveswww.starformation.news

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Cover image caption
M74 captured by the James Webb Space Telescope Mid-InfraRed Instrument (MIRI), which revealed delicate network offilaments of gas and dust in this galaxy’s well-defined spiral arms. At about 10 Mpc away from Earth, face-on galaxies like M74
are becoming key to understand Milky Way’s ISM and star formation activity. Credits: ESA/Webb, NASA & CSA, J. Lee and
the PHANGS-JWST Team. Acknowledgement: J. Schmidt

Note from the Editor

The Star Formation Newsletter is now on the web at www.starformation.news. This PDF file contains the monthly
Abstracts and links to the different Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to
the SFN is as simple as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site. Do not remove
the LATEX formatting when submitting to the arXiv. If you do, your abstract will not look great either at thearXiv or the SFN.

Abstracts
1. Insights on the Sun birth environment in the context of star-cluster formation in hubfilament systems
Doris Arzoumanian, Sota Arakawa, Masato I. N. Kobayashi, Kazunari Iwasaki, Kohei Fukada, Shoji Mori,
Yutaka Hirai, Masanobu Kunitomo, M. S. Nanda Kumar, Eiichiro Kokubo F Cylindrical molecular filaments

are observed to be the main sites of Sun-like star formation, while massive stars form in dense hubs, at the junctionof multiple filaments. The role of hub-filament configurations has not been discussed yet in relation to the birthenvironment of the solar system and to infer the origin of isotopic ratios of Short-Lived Radionuclides (SLR, such as
26Al) of Calcium-Aluminum-rich Inclusions (CAIs) observed in meteorites. In this work, we present simple analyticalestimates of the impact of stellar feedback on the young solar system forming along a filament of a hub-filament
system. We find that the host filament can shield the young solar system from the stellar feedback, both during theformation and evolution of stars (stellar outflow, wind, and radiation) and at the end of their life (supernovae). We
show that the young solar system formed along a dense filament can be enriched with supernova ejecta (e.g., 26 Al)
during the formation timescale of CAIs. We also propose that the streamers recently observed around protostars
may be channeling the SLR-rich material onto the young solar system. We conclude that considering hub-filamentconfigurations as the birth environment of the Sun is important when deriving theoretical models explaining theobserved properties of the solar system.

2. Detection of ethanol, acetone, and propanal in TMC-1: New O-bearing complex organics in cold sources
M. Agundez, J. C. Loison, K. M. Hickson, V. Wakelam, R. Fuentetaja, C. Cabezas, N. Marcelino, B. Tercero,P. de Vicente, J. Cernicharo F We present the detection of ethanol (C2H5OH), acetone (CH3COCH3), and propanal(C2H5CHO) toward the cyanopolyyne peak of TMC-1. These three O-bearing complex organic molecules are known
to be present in warm interstellar clouds, but had never been observed in a starless core. The addition of these three
new pieces to the puzzle of complex organic molecules in cold interstellar clouds stresses the rich chemical diversityof cold dense cores in stages prior to the onset of star formation. The detections of ethanol, acetone, and propanal
were made in the framework of QUIJOTE, a deep line survey of TMC-1 in the Q band that is being carried out with
the Yebes 40m telescope. We derive column densities of (1.1 +/- 0.3)e12 cm-2 for C2H5OH, (1.4 +/- 0.6)e11 cm-2
for CH3COCH3, and (1.9 +/- 0.7)e11 cm-2 for C2H5CHO. The formation of these three O-bearing complex organic
molecules is investigated with the aid of a detailed chemical model which includes gas and ice chemistry. The calculated2

abundances at a time around 2e5 yr are in reasonable agreement with the values derived from the observations. The
formation mechanisms of these molecules in our chemical model are as follows. Ethanol is formed on grains by addition of atomic carbon on methanol followed by hydrogenation and non-thermal desorption. Acetone and propanal are
produced by the gas-phase reaction between atomic oxygen and two different isomers of the C3H7 radical, where thelatter follows from the hydrogenation of C3 on grains followed by non-thermal desorption. A gas-phase route involving
the formation of (CH3)2COH+ through several ion-neutral reactions followed by its dissociative recombination withelectrons do also contribute to the formation of acetone.

3. Predicting Stellar Mass Accretion: An Optimized Echo State Network Approach inTime Series Modeling
Gianfranco Bino, Shantanu Basu, Ramit Dey, Sayantan Auddy, Lyle Muller, Eduard I. Vorobyov F Modelingthe dynamics of the formation and evolution of protostellar disks as well as the history of stellar mass accretion
typically involve the numerical solution of complex systems of coupled differential equations. The resulting massaccretion history of protostars is known to be highly episodic due to recurrent instabilities and also exhibits shorttimescale flickering. By leveraging the strong predictive abilities of neural networks, we extract some of the critical
temporal dynamics experienced during the mass accretion including periods of instability. Particularly, we utilize anovel form of the Echo-State Neural Network (ESN), which has been shown to efficiently deal with data having inherent
nonlinearity. We introduce the use of Optimized-ESN (Opt-ESN) to make model-independent time series forecasting ofmass accretion rate in the evolution of protostellar disks. We apply the network to multiple hydrodynamic simulations
with different initial conditions and exhibiting a variety of temporal dynamics to demonstrate the predictability of
the Opt-ESN model. The model is trained on simulation data of ∼ 1 − 2 Myr, and achieves predictions with a low
normalized mean square error (∼ 10−5 to 10−3 ) for forecasts ranging between 100 and 3800 yr. This result shows thepromise of the application of machine learning based models to time-domain astronomy.

4. JOYS: JWST Observations of Young protoStars: Outflows and accretion in the highmass star-forming region IRAS23385+605
H. Beuther, E. F. van Dishoeck, L. Tychoniec, C. Gieser, P. J. Kavanagh, G. Perotti, M. L. van Gelder, P.
Klaassen, A. Caratti o Garatti, L. Francis, W. R. M. Rocha, K. Slavicinska, T. Ray, K. Justtanont, H. Linnartz,
C. Weakens, L. Colina, T. Greve, M. Guedel, T. Henning, P. O. Lagage, B. Vandenbussche, G. Oestlin, G.
Wright F Aims: The JWST program JOYS (JWST Observations of Young protoStars) aims at characterizing thephysical and chemical properties of young high- and low-mass star-forming regions, in particular the unique midinfrared diagnostics of the warmer gas and solid-state components. We present early results from the high-mass starformation region IRAS23385+6053. Methods: The JOYS program uses the MIRI MRS with its IFU to investigate
a sample of high- and low-mass star-forming protostellar systems. Results: The 5 to 28mum MIRI spectrum of
IRAS23385+6053 shows a plethora of features. While the general spectrum is typical for an embedded protostar, we
see many atomic and molecular gas lines boosted by the higher spectral resolution and sensitivity compared to previous
space missions. Furthermore, ice and dust absorption features are also present. Here, we focus on the continuum
emission, outflow tracers like the H2, [FeII] and [NeII] lines as well as the potential accretion tracer Humphreys alphaHI(7–6). The short-wavelength MIRI data resolve two continuum sources A and B, where mid-infrared source A is
associated with the main mm continuum peak. The combination of mid-infrared and mm data reveals a young clusterin its making. Combining the mid-infrared outflow tracer H2, [FeII] and [NeII] with mm SiO data shows a complex
interplay of at least three molecular outflows driven by protostars in the forming cluster. Furthermore, the Humphreysalpha line is detected at a 3-4sigma level towards the mid-infrared sources A and B. Following Rigliaco et al. (2015),
one can roughly estimate accretion luminosities and corresponding accretion rates between 2.6x10−6 and 0.9x10−4
Msun/yr. This is discussed in the context of the observed outflow rates. Conclusions: The analysis of the MIRI MRS
observations for this young high-mass star-forming region reveals connected outflow and accretion signatures.

5. Mother of Dragons: A Massive, quiescent core in the dragon cloud (IRDC G028.37+00.07)
A. T. Barnes, J. Liu, Q. Zhang, J. C. Tan, F. Bigiel, P. Caselli, G. Cosentino, F. Fontani, J. D. Henshaw, I.
Jiménez-Serra, D-S. Kalb, C. Y. Law, S. N. Longmore, R. J. Parker, J. E. Pineda, A. Sánchez-Monge, W. Lim,K. Wang F Context: Core accretion models of massive star formation require the existence of massive, starless coreswithin molecular clouds. Yet, only a small number of candidates for such truly massive, monolithic cores are currently

3known. Aims: Here we analyse a massive core in the well-studied infrared-dark cloud (IRDC) called the ’dragon
cloud’ (also known as G028.37+00.07 or ’Cloud C’). This core (C2c1) sits at the end of a chain of a roughly equally
spaced actively star-forming cores near the centre of the IRDC. Methods: We present new high-angular resolution 1
mm ALMA dust continuum and molecular line observations of the massive core. Results: The high-angular resolution
observations show that this region fragments into two cores C2c1a and C2c1b, which retain significant backgroundsubtracted masses of 23 Msun and 2 Msun (31 Msun and 6 Msun without background subtraction), respectively. The
cores do not appear to fragment further on the scales of our highest angular resolution images (0.200 arcsec, 0.005 pc
1000 AU). We find that these cores are very dense (nH2 > 106 cm−3 ) and have only trans-sonic non-thermal motions(Ms ∼ 1). Together the mass, density and internal motions imply a virial parameter of < 1, which suggests the coresare gravitationally unstable, unless supported by strong magnetic fields with strengths of ∼ 1 - 10 mG. From COline observations, we find that there is tentative evidence for a weak molecular outflow towards the lower-mass core,and yet the more massive core remains devoid of any star formation indicators. Conclusions: We present evidence forthe existence of a massive, pre-stellar core, which has implications for theories of massive star formation. This source
warrants follow-up higher-angular-resolution observations to further assess its monolithic and pre-stellar nature.

6. Surveying the Giant HII Regions of the Milky Way with SOFIA: V. DR7 and K3-50

James M. De Buizer, Wanggi Lim, James T. Radomski, Mengyao Liu F We present our fifth set of results fromour mid-infrared imaging survey of Milky Way Giant HII (GHII) regions with our detailed analysis of DR7 and K3-50.
We obtained 20/25 and 37um imaging maps of both regions using the FORCAST instrument on the Stratospheric
Observatory For Infrared Astronomy (SOFIA). We investigate the multi-scale properties of DR7 and K3-50 using ourdata in conjunction with previous multi-wavelength observations. Near to far-infrared spectral energy distributions ofindividual compact infrared sources were constructed and fitted with massive young stellar object (MYSO) models.
We find eight out of the ten (80%) compact sources in K3-50 and three out of the four (75%) sources in DR7 arelikely to be MYSOs. We derived luminosity-to-mass ratios of the extended radio sub-regions of DR7 and K3-50 toestimate their relative ages. The large spread in evolutionary state for the sub-regions in K3-50 likely indicates that thestar-forming complex has undergone multiple star-forming events separated more widely in time, whereas the smaller
spread in DR7 likely indicates the star formation sub-regions are more co-eval. DR7 and K3-50 have Lyman continuum
photon rates just above the formal threshold criterion for being categorized as a GHII region (1050 photons/s) but
with large enough errors that this classification is uncertain. By measuring other observational characteristics in theinfrared, we find that K3-50 has properties more akin to previous bona fide GHII regions we have studied, whereas
DR7 has values more like those of the non-GHII regions we have previously studied.

7. Three-dimensional, Time-dependent MHD Simulation of Disk-Magnetosphere-Stellar
Wind Interaction in a T Tauri, Protoplanetary System
Ofer Cohen, Cecilia Garraffo, Jeremy Drake, Kristina Monsch, Igor Sokolov, Julian Alvarado-Gomez, Federico
Fraschetti F We present a three-dimensional, time-dependent, MHD simulation of the short-term interaction between

a protoplanetary disk and the stellar corona in a T Tauri system. The simulation includes the stellar magnetic field,
self-consistent coronal heating and stellar wind acceleration, and a disk rotating at sub-Keplerian velocity to induce
accretion. We find that initially, as the system relaxes from the assumed initial conditions, the inner part of the disk
winds around and moves inward and close to the star as expected. However, the self-consistent coronal heating andstellar wind acceleration build up the original state after some time, significantly pushing the disk out beyond 10R? .
After this initial relaxation period, we do not find clear evidence of a strong, steady accretion flow funneled along
coronal field lines, but only weak, sporadic accretion. We produce synthetic coronal X-ray line emission light curves
which show flare-like increases that are not correlated with accretion events nor with heating events. These variationsin the line emission flux are the result of compression and expansion due to disk-corona pressure variations. Verticaldisk evaporation evolves above and below the disk. However, the disk - stellar wind boundary stays quite stable, andany disk material that reaches the stellar wind region is advected out by the stellar wind.

8. JWST/NIRCam discovery of the first Y+Y brown dwarf binary: WISE J033605.05−014350.4
Per Calissendorff, Matthew De Furio, Michael Meyer, Loïc Albert, Christian Aganze, Mohamad Ali-Dib,
Daniella C. Bardalez Gagliuffi, Frederique Baron, Charles A. Beichman, Adam J. Burgasser, Michael C. Cushing, Jacqueline Kelly Faherty, Clémence Fontanive, Christopher R. Gelino, John E. Gizis, Alexandra Z. Green-4baum, J. Davy Kirkpatrick, Sandy K. Leggett, Frantz Martinache, David Mary, Mamadou N’Diaye, Benjamin
J. S. Pope, Thomas L Roellig, Johannes Sahlmann, Anand Sivaramakrishnan, Daniel Peter Thorngren, Marie
Ygouf, Thomas Vandal F We report the discovery of the first brown dwarf binary system with a Y dwarf primary,

WISE J033605.05−014350.4, observed with NIRCam on JWST with the F150W and F480M filters. We employed
an empirical point spread function binary model to identify the companion, located at a projected separation of 84
milliarcseconds, position angle of 295 degrees, and with contrast of 2.8 and 1.8 magnitudes in F150W and F480M,
respectively. At a distance of 10 pc based on its Spitzer parallax, and assuming a random inclination distribution, thephysical separation is approximately 1 au. Evolutionary models predict for that an age of 1-5 Gyr, the companion
mass is about 4-12.5 Jupiter masses around the 7.5-20 Jupiter mass primary, corresponding to a companion-to-hostmass fraction of q = 0.61 ± 0.05. Under the assumption of a Keplerian orbit the period for this extreme binary isin the range of 5-9 years. The system joins a small but growing sample of ultracool dwarf binaries with effective
temperatures of a few hundreds of Kelvin. Brown dwarf binaries lie at the nexus of importance for understanding theformation mechanisms of these elusive objects, as they allow us to investigate whether the companions formed as stars
or as planets in a disk around the primary.

Planet formation in the PDS 70 system: Constraining the atmospheric chemistry of
9. PDS 70b and c
A. J. Cridland, S. Facchini, E. F. van Dishoeck, M. Benisty F Understanding the chemical link between protoplanetary disks and planetary atmospheres is complicated by the fact that the popular targets in the study of disks
and planets are widely separated both in space and time. The 5 Myr PDS 70 systems offers a unique opportunity
to directly compare the chemistry of a giant planet’s atmosphere to the chemistry of its natal disk. To that end, we
derive our current best physical and chemical model for the PDS 70 disk through forward modelling of the 12 CO,
C18 O, and C2 H emission radial profiles with the thermochemical code DALI and find a volatile C/O ratio above
unity in the outer disk. Using what we know of the PDS 70 disk today, we analytically estimate the properties ofthe disk as it was 4 Myr in the past when we assume that the giant planets started their formation, and compute achemical model of the disk at that time. We compute the formation of PDS 70b and PDS 70c using the standard coreaccretion paradigm and account for the accretion of volatile and refractory sources of carbon and oxygen to estimate
the resulting atmospheric carbon-to-oxygen number ratio (C/O) for these planets. Our inferred C/O ratio of the gas
in the PDS 70 disk indicates that it is marginally carbon rich relative to the stellar C/O = 0.44 which we derive froman empirical relation between stellar metallicity and C/O. Under the assumption that the disk has been carbon richfor most of its lifetime, we find that the planets acquire a super-stellar C/O in their atmospheres. If the carbon-richdisk is a relatively recent phenomenon (i.e. developed after the formation of the planets at ∼ 1 Myr) then the planets
should have close to the stellar C/O in their atmospheres. This work lays the groundwork to better understand thedisk in the PDS 70 system as well as the planet formation scenario that produce its planets.

Transition disc nature of post-AGB binary systems confirmed by mid-infrared interfer10. ometry
A. Corporaal, J. Kluska, H. Van Winckel, K. Andrych, N. Cuello, D. Kamath, A. Merand F Circumbinary discs

around evolved post-asymptotic giant branch (post-AGB) binary systems show many similar properties to protoplanetary discs around young stars. Deficits of near-infrared (near-IR) flux in the spectral energy distributions (SEDs)of such systems hints towards large dust-free cavities, reminiscent of transition discs as commonly observed aroundyoung stars. We aim to assess the inner rim size of 6 post-AGB binary systems with such a lack in near-IR using
resolved mid-IR high-angular resolution observations of VLTI/MATISSE and VLTI/MIDI. The inner rim of only one
such system was previously resolved. We compare these inner rim sizes to 5 systems with available MATISSE datathat were identified to host a disc starting at the dust sublimation radius. We used geometric ring models to estimate
the inner rim sizes, the relative flux contributions of the star, the ring, and an over-resolved emission, the orientationof the ring, and the spectral dependencies of the components. We find that the dust inner rims of the targets with alack of near-IR excess in their SEDs are 2.5 to 7.5 times larger than the theoretical dust sublimation radii while thesystems that do not show such a deficit have inner rim sizes similar to their dust sublimation radii. Physical radii ofthe inner rims of these transition discs around post-AGB binaries are 3-25 au, which are larger than the disc sizes
inferred for transition discs around young stars with VLTI/MIDI. This is due to the higher stellar luminosities ofpost-AGB systems compared to young stars, implying larger dust sublimation radii and thus larger physical transition
disc inner radii. With mid-IR interferometric data we directly confirm the transition disc nature of six discs around5

post-AGB binary systems. Future observational and modelling efforts are needed to progress on the structure, origin,and evolution of these transition discs.

The impact of dust evolution on the dead zone outer edge in magnetized protoplanetary
11. disks
Timmy N. Delage, Matías Gárate, Satoshi Okuzumi, Chao-Chin Yang, Paola Pinilla, Mario Flock, SebastianMarkus Stammler, Tilman Birnstiel F [Abridged] Aims. We provide an important step toward a better under-

standing of the magnetorotational instability (MRI)-dust coevolution in protoplanetary disks by presenting a proof
of concept that dust evolution ultimately plays a crucial role in the MRI activity. Methods. First, we study how afixed power-law dust size distribution with varying parameters impacts the MRI activity, especially the steady-state
MRI-driven accretion, by employing and improving our previous 1+1D MRI-driven turbulence model. Second, we
relax the steady-state accretion assumption in this disk accretion model, and partially couple it to a dust evolution
model in order to investigate how the evolution of dust (dynamics and grain growth processes combined) and MRIdriven accretion are intertwined on million-year timescales. Results. Dust coagulation and settling lead to a higher
gas ionization degree in the protoplanetary disk, resulting in stronger MRI-driven turbulence as well as a more compact dead zone. On the other hand, fragmentation has an opposite effect because it replenishes the disk in small
dust particles. Since the dust content of the disk decreases over million years of evolution due to radial drift, theMRI-driven turbulence overall becomes stronger and the dead zone more compact until the disk dust-gas mixture
eventually behaves as a grain-free plasma. Furthermore, our results show that dust evolution alone does not lead to
a complete reactivation of the dead zone. Conclusions. The MRI activity evolution (hence the temporal evolution of
the MRI-induced α-parameter) is controlled by dust evolution and occurs on a timescale of local dust growth, as longas there is enough dust particles in the disk to dominate the recombination process for the ionization chemistry. Once
it is no longer the case, it is expected to be controlled by gas evolution and occurs on a viscous evolution timescale.

A novel survey for young substellar objects with the W-band filter VI: Spectroscopic
12. census of sub-stellar members and the IMF of σ Orionis cluster
Belinda Damian, Jessy Jose, Beth Biller, Gregory J. Herczeg, Loic Albert, Katelyn Allers, Zhoujian Zhang,Michael C. Liu, Sophie Dubber, KT Paul, Wen-Ping Chen, Bhavana Lalchand, Tanvi Sharma, Yumiko Oasa F

Low-mass stars and sub-stellar objects are essential in tracing the initial mass function (IMF). We study the nearby
young σ Orionis cluster (d∼408 pc; age∼1.8 Myr) using deep NIR photometric data in J, W and H-bands from
WIRCam on the Canada-France-Hawaii Telescope. We use the water absorption feature to photometrically selectthe brown dwarfs and confirm their nature spectroscopically with the IRTF-SpeX. Additionally we select candidate
low-mass stars for spectroscopy and analyze their membership and that of literature sources using astrometry from
Gaia DR3. We obtain the near-IR spectra for 28 very low-mass stars and brown dwarfs and estimate their spectral
type between M3-M8.5 (mass ranging between 0.3-0.01 M ). Apart from these, we also identify 5 new planetary mass
candidates which require further spectroscopic confirmation of youth. We compile the comprehensive catalog of 170
spectroscopically confirmed members in the central region of the cluster, for a wide mass range of ∼19-0.004 M .
We estimate the star/BD ratio to be ∼4, within the range reported for other nearby star forming regions. With theupdated catalog of members we trace the IMF down to 4 MJup and we find that a two-segment power-law fits the
sub-stellar IMF better than the log-normal distribution.

13. Toward a 3D kinetic tomography of Taurus clouds: II. A new automated technique andits validation
Q. Duchêne, C. Hottier, R. Lallement, J. L. Vergely, C. Babusiaux, A. Marchal, F. Arenou F Three-dimensional(3D) kinetic maps of the Milky Way interstellar medium are an essential tool in studies of its structure and of starformation. We aim to assign radial velocities to Galactic interstellar clouds now spatially localized based on starlight
extinction and star distances from Gaia and stellar surveys. We developed an automated search for coherent projections
on the sky of clouds isolated in 3D extinction density maps on the one hand, and regions responsible for CO radio
emissions at specific Doppler shifts on the other hand. The discrete dust structures were obtained by application of
the Fellwalker algorithm to a recent 3D extinction density map. For each extinction cloud, a technique using a narrowsliding spectral window moved along the contour-bounded CO spectrum and geometrical criteria was used to selectthe most likely velocity interval. We applied the new contour-based technique to the 3D extinction density distribution

6

within the volume encompassing the Taurus, Auriga, Perseus and California molecular complexes. From the 45 clouds
issued from the decomposition, 42 were assigned a velocity. The remaining structures correspond to very weak COemission or extinction. We used the non-automated assignments of radial velocities to clouds of the same region
presented in paper I and based on KI absorption spectra as a validation test. The new fully automated determinations
were found in good agreement with these previous measurements. Our results show that an automated search basedon cloud contour morphology can be efficient and that this novel technique may be extended to wider regions of the
Milky Way and at larger distance. We discuss its limitations and potential improvements after combination with othertechniques.

14. Modeling Two First Hydrostatic Core Candidates Barnard 1b-N and 1b-S

Hao-Yuan Duan, Shih-Ping Lai, Naomi Hirano, Travis J. Thieme F A first hydrostatic core (FHC) is proposed

to form after the initial collapse of a prestellar core, as a seed of a Class 0 protostar. FHCs are difficult to observe
because they are small, compact, embedded, and short lived. In this work, we explored the physical properties of two
well-known FHC candidates, B1-bN and B1-bS, by comparing interferometric data from Submillimeter Array (SMA)
1.1 and 1.3 mm and Atacama Large Millimeter/submillimeter Array (ALMA) 870 µm observations with simulatedsynthesis images of the two sources. The simulated images are based on a simple model containing a single, hot
compact first-core-like component at the center surrounded by a large-scale, cold and dusty envelope described bya broken power-law density distribution with an index, α. Our results show that the hot compact components of
B1-bN and B1-bS can be described by temperatures of ∼ 500 K with a size of ∼ 4 au, which are in agreement withtheoretical predictions of an FHC. If the α inside the broken radii is fixed to -1.5, we find α ∼ -2.9 and ∼ -3.3
outside the broken radii for B1-bN and B1-bS, respectively, consistent with theoretical calculations of a collapsing,bounded envelope and previous observations. Comparing the density and temperature profiles of the two sources withradiation-hydrodynamic simulations of an FHC, we find both sources lie close to, but before, the second collapse stage.
We suggest that B1-bS may have started the collapsing process earlier compared to B1-bN, since a larger discontinuity
point is found in its density profile.

The importance of live binary evolution in numerical simulations of binaries embedded
15. in circumbinary discs
Alessia Franchini, Alessandro Lupi, Alberto Sesana, Zoltan Haiman F The shrinking of a binary orbit driven

by the interaction with a gaseous circumbinary disc, initially advocated as a potential way to catalyze the binary
merger, has been recently debated in the case of geometrically thick (i.e. with H/R & 0.1) discs. However, a clear
consensus is still missing mainly owing to numerical limitations, such as fixed orbit binaries or lack of resolution
inside the cavity carved by the binary in its circumbinary disc. In this work, we asses the importance of evolving thebinary orbit by means of hydrodynamic simulations performed with the code gizmo in meshless-finite-mass mode. In
order to model the interaction between equal mass circular binaries and their locally isothermal circumbinary discs,
we enforce hyper-Lagrangian resolution inside the cavity. We find that fixing the binary orbit ultimately leads to an
overestimate of the gravitational torque that the gas exerts on the binary, and in an underestimate of the torque dueto the accretion of material onto the binary components. Furthermore, we find that the modulation of the accretion
rate on the binary orbital period is strongly suppressed in the fixed orbit simulation, while it is clearly present in thelive binary simulations. This has potential implications for the prediction of the observable periodicities in massive
black hole binary candidates.

Photometric activity of CQ Tau on the time interval of 125 years
16. V. P. Grinin, L. V. Tambovtseva, O. Yu. Barsunova, D. N. Shakhovskoy F The star CQ Tau belongs to thefamily of UX Ori type stars. It has very complex photometric behavior and complex structure of the circumstellar
environment. In our paper we constructed the historical 125 years light curve of this star basing on the publishedphotometric observations. It follows that besides a random component characteristic of UX Ori type stars, the large
amplitude periodic component with the 10 year period is also present. Its existence was suspected earlier in [11].
New observations confirm its reality. It points to an existence of the second component close to the star. The density
waves and matter flows caused by the companion motion lead to periodic changes in the circumstellar extinction andbrightness of the star. This result is discussed in context of the recent observations of CQ Tau with high angularresolution.

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Physical and chemical complexity in high-mass star-forming regions with ALMA. I.
17. Overview and evolutionary trends of physical properties
Caroline Gieser, Henrik Beuther, Dmitry Semenov, Aida Ahmadi, Thomas Henning, Molly R. A. Wells F In

this study, we investigate how physical properties, such as the density and temperature profiles, evolve on core scales
through the evolutionary sequence during high-mass star formation ranging from protostars in cold infrared dark clouds
to evolved UCHII regions. We observed 11 high-mass star-forming regions with ALMA at 3 mm wavelengths. Basedon the 3 mm continuum morphology and recombination line emission, tracing locations with free-free (ff) emission,
the fragmented cores analyzed in this study are classified into either dust or dust+ff cores. In addition, we resolve
three cometary UCHII regions with extended 3 mm emission that is dominated by free-free emission. The temperature
structure and radial profiles (T r−q ) are determined by modeling molecular emission of CH3CN and CH313CN with
XCLASS and by using the HCN-to- HNC intensity ratio as probes for the gas kinetic temperature. The density profiles(n r−p ) are estimated from the 3 mm continuum visibility profiles. The masses M and H2 column densities N(H2)
are then calculated from the 3 mm dust continuum emission. Results. We find a large spread in mass and peak H2column density in the detected sources ranging from 0.1-150 Msun and 1023 - 1026 cm−2 , respectively. Including
the results of the CORE and CORE-extension studies (Gieser et al. 2021, 2022) to increase the sample size, we findevolutionary trends on core scales for the temperature power- law index q increasing from 0.1 to 0.7 from infrared darkclouds to UCHII regions, while for the the density power-law index p on core scales, we do not find strong evidence
for an evolutionary trend. However, we find that on the larger clump scales throughout these evolutionary phases thedensity profile flattens from p = 2.2 to p = 1.2. (abridged)

18. Accretion of aerodynamically large pebbles
Helong Huang, Chris W. Ormel F Due to their aerodynamical coupling with gas, pebbles in protoplanetary discs

can drift over large distances to support planet growth in the inner disc. In the past decade, this pebble accretionhas been studied extensively for aerodynamically small pebbles (Stokes number St < 1). However, accretion can also
operate in the St > 1 mode, e.g., when planetesimals collisionally fragment to smaller bodies or when the primordialgas disc disperses. This work aims to extend the study of pebble accretion to these aerodynamically loosely coupled
particles. We integrate the pebble’s equation of motion, accounting for gas drag, stellar and planetary gravity, in the
midplane of a laminar disc. The accretion probability () is calculated as function of Stokes number, disc pressure
gradient index, planet mass and eccentricity. We find that for Stokes number above unity (St) first rises, due to lower
drift and aided by a large atmospheric capture radius, until it reaches a plateau where the efficiency approaches 100
per cent. At high St the plateau region terminates as particles become trapped in resonance. These results are welldescribed by a semi-analytical "kick-and-drift" model and we also provide fully analytical prescriptions for . We apply
our model to the accretion of ∼ 30µm dust particles in a dispersing protoplanetary and secondary (CO-rich) debris
disc. It shows that physically small particles are mainly accreted as aerodynamically large Stokes number pebbles
during the debris disc phase. Earth-mass planets may obtain ∼ 25 per cent of their heavy elements through this lateaccretion phase.

role of previous generations of stars in triggering star formation and driving gas
19. Thedynamics
Nicholas P. Herrington, Clare L. Dobbs, Thomas J. R. Bending F We present hydrodynamic and magnetohydro-

dynamic (MHD) simulations of sub galactic regions including photoionising and supernova feedack. We aim to improve
the initial conditions of our region extraction models by including an initial population of stars. We also investigate
the reliability of extracting regions in simulations, and show that with a good choice of region, results are comparablewith using a larger region for the duration of our simulations. Simulations of star formation on molecular cloud scales
typically start with a turbulent cloud of gas, from which stars form and then undergo feedback. In reality, a typicalcloud or region within a galaxy may already include, or reside near some population of stars containing massive stars
undergoing feedback. We find the main role of a prior population is triggering star formation, and contributing togas dynamics. Early time supernova from the initial population are important in triggering new star formation anddriving gas motions on larger scales above 100 pc, whilst the ionising feedback contribution from the initial population
has less impact, since many members of the initial population have cleared out gas around them in the prior model. In
terms of overall star formation rates though, the initial population has a relatively small effect, and the feedback does
not for example suppress subsequent star formation. We find that MHD has a relatively larger impact than initialconditions, reducing the star formation rate by a factor of 3 at later times.
820. Simulated observations of star formation regions: infrared evolution of globally collapsing clouds
Jesús M. Jáquez-Domínguez, Roberto Galván-Madrid, Jacopo Fritz, Manuel Zamora-Avilés, Peter Camps,
Gustavo Bruzual, Maarten Baes, Yuxin Lin, Enrique Vázquez-Semadeni F The direct comparison between hy-

drodynamical simulations and observations is needed to improve the physics included in the former and test biases
in the latter. Post-processing radiative transfer and synthetic observations are now the standard way to do this. We
report on the first application of the SKIRT radiative transfer code to simulations of a star-forming cloud. The synthetic observations are then analyzed following traditional observational workflows. We find that in the early stagesof the simulation, stellar radiation is inefficient in heating dust to the temperatures observed in Galactic clouds, thus
the addition of an interstellar radiation field is necessary. The spectral energy distribution of the cloud settles rather
quickly after ∼ 3 Myr of evolution from the onset of star formation, but its morphology continues to evolve for ∼ 8 Myr
due to the expansion of Hii regions and the respective creation of cavities, filaments, and ridges. Modeling synthetic
Herschel fluxes with 1- or 2-component modified black bodies underestimates total dust masses by a factor of ∼ 2.
Spatially-resolved fitting recovers up to about 70% of the intrinsic value. This “missing mass” is located in a very cold
dust component with temperatures below 10 K, which does not contribute appreciably to the far-infrared flux. Thiseffect could bias real observations if such dust exists in large amounts. Finally, we tested observational calibrations of
the SFR based on infrared fluxes and concluded that they are in agreement when compared to the intrinsic SFR ofthe simulation averaged over ∼ 100 Myr.

21. A spectacular jet from the bright 244-440 Orion proplyd: the MUSE NFM view

A. Kirwan, C. F. Manara, E. T. Whelan, M. Robberto, A. F. McLeod, S. Facchini, G. Beccari, A. Miotello, P.
C. Schneider, A. Murphy, S. Vicente F In this work we present the highest spatial and spectral resolution integral

field observations to date of the bipolar jet from the Orion proplyd 244-440 using MUSE NFM) observations on the
VLT. We observed a previously unreported chain of six distinct knots in a roughly S-shaped pattern, and by comparing
them with HST images we estimated proper motions in the redshifted knots of 9.5 mas yr−1 with an inclination angleof 73◦ , though these quantities could not be measured for the blueshifted lobe. Analysis of the [FeII] and [NiII] lines
suggests jet densities on the order of ∼ 105 cm−3 . We propose that the observed S-shaped morphology originates froma jet launched by a smaller source with M? < 0.2 M in orbital motion around a larger companion of M? ' 0.5 M at
a separation of 30-40 au. The measured luminosities of the knots using the [OI]λ6300 and [SII]λ6731 lines were used
to estimate a lower limit to the mass-loss rate in the jet of 1.3 × 10−11 M yr−1 and an upper limit of 10−9 M yr−1 ,which is typical for low-mass driving sources. While the brightness asymmetry between the redshifted and blueshifted
lobes is consistent with external irradiation, further analysis of the [NiII] and [FeII] lines suggests that photoionizationof the jet is not likely to be a dominant factor, and that the emission is dominated by collisional excitation. The
dynamical age of the jet compared to the anticipated survival time of the proplyd demonstrates that photoevaporationof the proplyd occurred prior to jet launching, and that this is still an active source. These two points suggest thatthe envelope of the proplyd may shield the jet from the majority of external radiation, and that photoionization of
the proplyd does not appear to impact the ability of a star to launch a jet.

Spectral classification of young stars using conditional invertible neural networks I. In22. troducing and validating the method
Da Eun Kang, Victor F. Ksoll, Dominika Itrich, Leonardo Testi, Ralf S. Klessen, Patrick Hennebelle, Sergio
Molinari F Aims. We introduce a new deep learning tool that estimates stellar parameters (such as effective tem-

perature, surface gravity, and extinction) of young low-mass stars by coupling the Phoenix stellar atmosphere modelwith a conditional invertible neural network (cINN). Our networks allow us to infer the posterior distribution of eachstellar parameter from the optical spectrum. Methods. We discuss cINNs trained on three different Phoenix grids:
Settl, NextGen, and Dusty. We evaluate the performance of these cINNs on unlearned Phoenix synthetic spectra andon the spectra of 36 Class III template stars with well-characterised stellar parameters. Results. We confirm thatthe cINNs estimate the considered stellar parameters almost perfectly when tested on unlearned Phoenix synthetic
spectra. Applying our networks to Class III stars, we find good agreement with deviations of at most 5–10 per cent.
The cINNs perform slightly better for earlier-type stars than for later-type stars like late M-type stars, but we conclude
that estimations of effective temperature and surface gravity are reliable for all spectral types within the network’s
training range. Conclusions. Our networks are time-efficient tools applicable to large amounts of observations. Amongthe three networks, we recommend using the cINN trained on the Settl library (Settl-Net), as it provides the best9

performance across the largest range of temperature and gravity.

23. A Large Double-ring Disk around the Taurus M Dwarf J04124068+2438157
Feng Long, Bin B. Ren, Nicole L. Wallack, Daniel Harsono, Gregory J. Herczeg, Paola Pinilla, Dimitri Mawet,
Michael C. Liu, Sean M. Andrews, Xue-Ning Bai, Sylvie Cabrit, Lucas A. Cieza, Doug Johnstone, Jarron
M. Leisenring, Giuseppe Lodato, Yao Liu, Carlo F. Manara, Gijs D. Mulders, Enrico Ragusa, Steph Sallum,
Yangfan Shi, Marco Tazzari, Taichi Uyama, Kevin Wagner, David J. Wilner, Jerry W. Xuan F Planet formation

imprints signatures on the physical structures of disks. In this paper, we present high-resolution (∼50 mas, 8 au)
Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and CO line emission
toward the disk around the M3.5 star 2MASS J04124068+2438157. The dust disk consists only of two narrow rings
at radial distances of 0.47 and 0.78 arcsec (∼70 and 116 au), with Gaussian σ widths of 5.6 and 8.5 au, respectively.
The width of the outer ring is smaller than the estimated pressure scale height by ∼ 25%, suggesting dust trappingin a radial pressure bump. The dust disk size, set by the location of the outermost ring, is significantly larger (by 3σ)than other disks with similar millimeter luminosity, which can be explained by an early formation of local pressure
bump to stop radial drift of millimeter dust grains. After considering the disk’s physical structure and accretion
properties, we prefer planet–disk interaction over dead zone or photoevaporation models to explain the observed dust
disk morphology. We carry out high-contrast imaging at L0 band using Keck/NIRC2 to search for potential youngplanets, but do not identify any source above 5σ. Within the dust gap between the two rings, we reach a contrast levelof ∼7 mag, constraining the possible planet below ∼2–4 MJup . Analyses of the gap/ring properties suggest a ∼Saturn
mass planet at ∼90 au is likely responsible for the formation of the outer ring, which can be potentially revealed withJWST.

The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). VIII.
24. Dynamics of Embedded Dense Cores
Shanghuo Li, Patricio Sanhueza, Qizhou Zhang, Garay Guido, Giovanni Sabatini, Kaho Morii, Xing Lu, Daniel
Tafoya, Fumitaka Nakamura, Natsuko Izumi, Keńichi Tatematsu, Fei Li F We present the dynamical propertiesof 294 cores embedded in twelve IRDCs observed as part of the ASHES Survey. Protostellar cores have higher gas
masses, surface densities, column densities, and volume densities than prestellar cores, indicating core mass growthfrom the prestellar to the protostellar phase. We find that 80measurements are gravitationally bound (α< 2). We
also find an anti-correlation between the mass and the virial parameter of cores, with massive cores having on average
lower virial parameters. Protostellar cores are more gravitationally bound than prestellar cores, with an averagevirial parameter of 1.2 and 1.5, respectively. The observed non-thermal velocity dispersion (from N2 D+ or DCO+ ) is
consistent with simulations in which turbulence is continuously injected, whereas the core-to-core velocity dispersion
is neither in agreement with driven nor decaying turbulence simulations. We find no significant increment in the line
velocity dispersion from prestellar to protostellar cores, suggesting that dense gas within the core traced by these
deuterated molecules is not yet severely affected by turbulence injected from outflow activity at the early evolutionary
stages traced in ASHES. The most massive cores are strongly self-gravitating and have greater surface density, Mach
number, and velocity dispersion than cores with lower masses. Dense cores have not significant velocity shifts relative
to their low-density envelopes, suggesting that dense cores are co-moving with their envelopes. We conclude thatthe observed core properties are more in line with predictions of “clump-fed" scenarios rather than with “core-fed"
scenarios.

Far-infrared line emission from the outer Galaxy cluster Gy 3-7 with SOFIA/FIFI-LS:
25. Physical conditions and UV fields
N. Le, A. Karska, M. Figueira, M. Sewiło, A. Mirocha, Ch. Fischer, M. Kaźmierczak-Barthel, R. Klein,
M. Gawroński, M. Koprowski, K. Kowalczyk, W. J. Fischer, K. M. Menten, F. Wyrowski, C. König, L. E.
Kristensen F (abridged) Far-infrared (FIR) line emission provides key information about the gas cooling and heating

due to shocks and UV radiation associated with the early stages of star formation. Gas cooling via FIR lines might,
however, depend on metallicity. We aim to quantify the FIR line emission and determine the spatial distribution of the
CO rotational temperature, ultraviolet (UV) radiation field, and H2 number density toward the embedded cluster Gy
3-7 in the CMa-l224 star-forming region, whose metallicity is expected to be intermediate between that of the LMC
and the Solar neighborhood. By comparing the total luminosities of CO and [O I] toward Gy 3-7 with values found for10

low- and high-mass protostars extending over a broad range of metallicities, we also aim to identify the possible effectsof metallicity on the FIR line cooling within our Galaxy. We studied SOFIA/FIFI-LS spectra of Gy 3-7 covering
several FIR lines. The spatial extent of CO high-J (J>14) emission resembles that of the elongated 160 um continuum
emission detected with Herschel. The CO transitions from J=14-13 to J=16-15 are detected throughout the clusterand show a median rotational temperature of 170+/-30 K on Boltzmann diagrams. Comparisons to other protostars
observed with Herschel show a good agreement with intermediate-mass sources in the inner Galaxy. Assuming an
origin of the [O I] and high-J CO emission in UV-irradiated C-shocks, we obtained pre-shock H2 number densitiesof 104−5 cm−3 and UV radiation field strengths of 0.1-10 Habing fields. Far-IR line observations reveal ongoing starformation in Gy 3-7, dominated by intermediate-mass Class 0/I young stellar objects. The ratio of molecular-to-atomic
far-IR line emission shows a decreasing trend with bolometric luminosities of the protostars. However, it does notindicate that the low-metallicity has an impact on the line cooling in Gy 3-7.

26. Properties of the dense cores and filamentary structures in the Vela C molecular cloud

Xue-Mei Li, Guo-Yin Zhang, Alexander Men’shchikov, Jin-Zeng Li, Chang Zhang, Zhong-Zu Wu F The initialand boundary conditions of the Galactic star formation in molecular clouds are not well understood. In an effort toshed new light on this long-standing problem, we measured properties of dense cores and filamentary structures in the
Vela C molecular cloud, observed with Herschel. We applied the getsf extraction method to separate the components
of sources and filaments from each other and their backgrounds, before detecting, measuring, and cataloging thestructures. The cores and filamentary structures constitute 40low-density molecular background cloud. We selected
570 reliable cores, of which 149 are the protostellar cores and 421 are the starless cores. Almost 78% of the starless cores
were identified with the gravitationally bound prestellar cores. The exponent of the CMF (alpha = 1.35) is identicalto that of the Salpeter IMF. We selected 68 filaments with at least one side that appeared not blended with adjacentstructures. The filament widths are in the range of 0.15 pc to 0.63 pc, and have a median value of W = 0.3(0.11) pc.
The surface densities of filaments are well correlated with their contrasts and linear densities. Within uncertainties ofthe filament instability criterion, many filaments may well be both supercritical and subcritical. A large fraction offilaments may definitely be considered supercritical, in which are found 94 prestellar cores, 83 protostellar cores, andonly 1 unbound starless core. Taking into account the uncertainties, the supercritical filaments contain only prestellar
and protostellar cores. Our findings support the idea that there exists a direct relationship between the CMF and IMF
and that filaments play a key role in the formation of prestellar cores, which is consistent with the previous Herschelresults.

27. Modeling of thermal and non-thermal radio emission from HH80-81 jet

Sreelekshmi Mohan, Sarita Vig, Samir Mandal F Protostellar jets are one of the primary signposts of star formation.
A handful of protostellar objects exhibit radio emission from ionized jets, of which a few display negative spectral
indices, indicating the presence of synchrotron emission. In this study, we characterize the radio spectra of HH80-81
jet with the help of a numerical model that we have developed earlier, which takes into account both thermal free-freeand non-thermal synchrotron emission mechanisms. For modeling the HH80-81 jet, we consider jet emission towards
the central region close to the driving source along with two Herbig-Haro objects, HH80 and HH81. We have obtained
the best-fit parameters for each of these sources by fitting the model to radio observational data corresponding to two
frequency windows taken across two epochs. Considering an electron number density in the range 103 − 105 cm−3 , weobtained the thickness of the jet edges and fraction of relativistic electrons that contribute to non-thermal emission in
the range 0.01◦ − 0.1◦ and 10−7 − 10−4 , respectively. For the best-fit parameter sets, the model spectral indices lie in
the range of -0.15 to +0.11 within the observed frequency windows.

28. Herbig-Haro Flows and Young Stars in the Dobashi 5006 Dark Cloud
T. A. Movsessian, T. Yu. Magakian, A. S. Rastorguev, H. R. Andreasyan F Two new Herbig-Haro flows were

found in a study of the isolated Dobashi 5006 dark cloud (l= 216◦ .7, b= −13◦ .9): one certain (HH 1179) and one
presumable, associated with the infrared sources 2MASS 06082284−0936139 and 2MASS 06081525−0933490, correspondingly. Judging from their spectral energy distributions, these sources may be Class 1 objects with luminosities
of order 23 L and 3.6 L , respectively. They are part of the poor star cluster MWSC 0739, study of which basedon data from the Gaia DR3 survey has made it possible to detect 17 stars which are probably members of it. A list ofthem and their main parameters is given. The distance of the cluster is estimated to be 820 pc and the color excess11on the path to the cluster is E(BP-RP) ≈1.05 mag. All of these stars are PMS-objects and most of them are opticallyvariable. It is concluded that the newly discovered compact star-formation zone in the Dobashi 5006 cloud has an ageof no more than a few million years and this process continues up to the present time.

FAUST VIII. The protostellar disk of VLA 1623-2417 W and its streamers imaged by
29. ALMA
S. Mercimek, L. Podio, C. Codella, L. Chahine, A. López-Sepulcre, S. Ohashi, L. Loinard, D. Johnstone, F.
Menard, N. Cuello, P. Caselli, J. Zamponi, Y. Aikawa, E. Bianchi, G. Busquet, J. E. Pineda, M. Bouvier, M.
De Simone, Y. Zhang, N. Sakai, C. J. Chandler, C. Ceccarelli, F. Alves, A. Durán, D. Fedele, N. Murillo, I.
Jiménez-Serra, S. Yamamoto F More than 50% of solar-mass stars form in multiple systems. It is therefore crucial

to investigate how multiplicity affects the star and planet formation processes at the protostellar stage. We reportcontinuum and C18 O (2-1) observations of the VLA 1623-2417 protostellar system at 50 au angular resolution as partof the ALMA Large Program FAUST. The 1.3 mm continuum probes the disks of VLA 1623A, B, and W, and thecircumbinary disk of the A1+A2 binary. The C18 O emission reveals, for the first time, the gas in the disk-envelopeof VLA 1623W. We estimate the dynamical mass of VLA 1623W, Mdyn = 0.45 ± 0.08 M , and the mass of its disk,
Mdisk ∼ 6 × 10−3 M . C18 O also reveals streamers that extend up to 1000 au, spatially and kinematically connecting
the envelope and outflow cavities of the A1+A2+B system with the disk of VLA 1623W. The presence of the streamers,
as well as the spatial (∼1300 au) and velocity (∼2.2 km/s) offset of VLA 1623W suggest that either sources W and
A+B formed in different cores, interacting between them, or that source W has been ejected from the VLA 1623
multiple system during its formation. In the latter case, the streamers may funnel material from the envelope andcavities of VLA 1623AB onto VLA 1623W, thus concurring to set its final mass and chemical content.

30. Can Protostellar Outflows Set Stellar Masses?

Philip C. Myers, Michael M. Dunham, Ian W. Stephens F The opening angles of some protostellar outflows appear

too narrow to match the expected core-star mass efficiency SFE = 0.3-0.5 if outflow cavity volume traces outflow mass,
with a conical shape and a maximum opening angle near 90 deg. However, outflow cavities with paraboloidal shape
and wider angles are more consistent with observed estimates of the SFE. This paper presents a model of infall andoutflow evolution based on these properties. The initial state is a truncated singular isothermal sphere which has mass
≈1 M , free fall time ≈80 kyr, and small fractions of magnetic, rotational, and turbulent energy. The core collapses
pressure-free as its protostar and disk launch a paraboloidal wide-angle wind. The cavity walls expand radially andentrain envelope gas into the outflow. The model matches SFE values when the outflow mass increases faster thanthe protostar mass by a factor 1 - 2, yielding protostar masses typical of the IMF. It matches observed outflow angles
if the outflow mass increases at nearly the same rate as the cavity volume. The predicted outflow angles are thentypically ∼50 deg as they increase rapidly through the stage 0 duration of ∼40 kyr. They increase more slowly up to∼110 deg during their stage I duration of ∼70 kyr. With these outflow rates and shapes, model predictions appear
consistent with observational estimates of typical stellar masses, SFEs, stage durations, and outflow angles, with noneed for external mechanisms of core dispersal.

31. NGTS clusters survey IV. Search for Dipper stars in the Orion Nebular Cluster

Tyler Moulton, Simon T Hodgkin, Gareth D Smith, Joshua T Briegal, Edward Gillen, Jack S Acton, Matthew
P Battley, Matthew R Burleigh, Sarah L Casewell, Samuel Gill, Michael R Goad, Beth A Henderson, Alicia
Kendall, Gavin Ramsay, Rosanna H Tilbrook, Peter J Wheatley F The dipper is a novel class of young stellar

object associated with large drops in flux on the order of 10 to 50 per cent lasting for hours to days. Too significant toarise from intrinsic stellar variability, these flux drops are currently attributed to disk warps, accretion streams, and/ortransiting circumstellar dust. Dippers have been previously studied in young star forming regions including the Orion
Complex. Using Next Generation Transit Survey (NGTS) data, we identified variable stars from their lightcurves.
We then applied a machine learning random forest classifier for the identification of new dipper stars in Orion using
previous variable classifications as a training set. We discover 120 new dippers, of which 83 are known members of theComplex. We also investigated the occurrence rate of disks in our targets, again using a machine learning approach.
We find that all dippers have disks, and most of these are full disks. We use dipper periodicity and model-derived
stellar masses to identify the orbital distance to the inner disk edge for dipper objects, confirming that dipper stars
exhibit strongly extended sublimation radii, adding weight to arguments that the inner disk edge is further out than12

predicted by simple models. Finally, we determine a dipper fraction (the fraction of stars with disks which are dippers)
for known members of 27.8 plus minus 2.9 per cent. Our findings represent the largest population of dippers identified
in a single cluster to date.

32. Early Bombardment of the Moon: Connecting the Lunar Crater Record to the Terrestrial Planet Formation
David Nesvorny, Fernando V. Roig, David Vokrouhlicky, William F. Bottke, Simone Marchi, Alessandro Morbidelli, Rogerio Deienno F The lunar crater record features ∼ 50 basins. The radiometric dating of Apollo samples

indicates that the Imbrium basin formed relatively late – from the planet formation perspective – some ' 3.9 Ga.
Here we develop a dynamical model for impactors in the inner solar system to provide context for the interpretationof the lunar crater record. The contribution of cometary impactors is found to be insignificant. Asteroids produced
most large impacts on the terrestrial worlds in the last ' 3 Gyr. The great majority of early impactors were rocky
planetesimals left behind at ∼ 0.5–1.5 au after the terrestrial planet accretion. The population of terrestrial planetesimals was reduced by disruptive collisions in the first t ∼ 20 Myr after the gas disk dispersal. We estimate that
there were ∼ 4 × 105 diameter d > 10 km bodies when the Moon formed (total planetesimal mass ∼ 0.015 MEarth att ∼ 50 Myr). The early bombardment of the Moon was intense. To accommodate ∼ 50 known basins, the lunar basinsthat formed before ' 4.35–4.41 Ga must have been erased. The late formation of Imbrium occurs with a ∼ 15–35%
probability in our model. About 20 d > 10-km bodies were expected to hit the Earth between 2.5 and 3.5 Ga, whichis comparable to the number of known spherule beds in the late Archean. We discuss implications of our model forthe lunar/Martian crater chronologies, Late Veneer, and noble gases in the Earth atmosphere.

An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud
33. with the Atacama Compact Array. II. CO Cloud Catalog
Takahiro Ohno, Kazuki Tokuda, Ayu Konishi, Takeru Matsumoto, Marta Sewiło, Hiroshi Kondo, Hidetoshi
Sano, Kisetsu Tsuge, Sarolta Zahorecz, Nao Goto, Naslim Neelamkodan, Tony Wong, Hajime Fukushima,
Tatsuya Takekoshi, Kazuyuki Muraoka, Akiko Kawamura, Kengo Tachihara, Yasuo Fukui, Toshikazu Onishi

F The nature of molecular clouds and their statistical behavior in sub-solar metallicity environments are not fully
explored yet. We analyzed an unbiased CO(J = 2-1) survey data at a spatial resolution of ∼2 pc in the northern regionof the Small Magellanic Cloud (SMC) with the Atacama Compact Array to characterize the CO cloud properties. A
cloud decomposition analysis identified 426 spatially/velocity-independent CO clouds and their substructures. Basedon the cross-matching with known infrared catalogs by Spitzer and Herschel, more than 90% CO clouds show spatial
correlations with point sources. We investigated the basic properties of the CO clouds and found that the radiusvelocity linewidth (R-σv ) relation follows the Milky Way (MW) like power-low exponent, but the intercept is ∼1.5
times lower than that in the MW. The mass functions (dN/dM ) of the CO luminosity and virial mass are characterized
by an exponent of ∼1.7, which is consistent with previously reported values in the Large Magellanic Cloud and MW.

34. The distance to the Serpens South Cluster from H2O masers
Gisela N. Ortiz-Leon, Sergio A. Dzib, Laurent Loinard, Yan Gong, Thushara Pillai, Adele Plunkett F In thisLetter, we report Very Long Baseline Array observations of 22 GHz water masers toward the protostar CARMA-6,
located at the center of the Serpens South young cluster. From the astrometric fits to maser spots, we derive a distanceof 440.7+/-3.5 pc for the protostar (1% error). This represents the best direct distance determination obtained so far
for an object this young and deeply embedded in this highly obscured region. Taking into account depth effects, we
obtain a distance to the cluster of 440.7+/-4.6 pc. Stars visible in the optical that have astrometric solutions in the
Gaia Data Release 3 are, on the other hand, all located in the periphery of the cluster. Their mean distance of 437(+51, -41) pc is consistent within 1-sigma with the value derived from maser astrometry. As the maser source is justat the center of Serpens South, we finally solve the ambiguity of the distance to this region that has prevailed over theyears.

35. Correlating Changes in Spot Filling Factors with Stellar Rotation: The Case of LkCa 4
Facundo Pérez Paolino, Jeffrey S. Bary, Michael S. Petersen, Kimberly Ward-Duong, Benjamin M. Tofflemire,
Katherine B. Follette, Heidi Mach F We present a multi-epoch spectroscopic study of LkCa 4, a heavily spotted

non-accreting T Tauri star. Using SpeX at NASA’s Infrared Telescope Facility (IRTF), 12 spectra were collected13

over five consecutive nights, spanning ≈ 1.5 stellar rotations. Using the IRTF SpeX Spectral Library, we constructedempirical composite models of spotted stars by combining a warmer (photosphere) standard star spectrum with a cooler(spot) standard weighted by the spot filling factor, fspot . The best-fit models spanned two photospheric component
temperatures, Tphot = 4100 K (K7V) and 4400 K (K5V), and one spot component temperature, Tspot = 3060 K (M5V)
with an AV of 0.3. We find values of fspot to vary between 0.77 and 0.94 with an average uncertainty of ∼0.04. The
meanvariability of fspot is periodic and correlates with its 3.374 day rotational period. Using a mean value for fspot
torepresent the total spot coverage, we calculated spot corrected values for Tef f and L? . Placing these values alongside
evolutionary models developed for heavily spotted young stars, we infer mass and age ranges of 0.45-0.6 M and 0.501.25 Myr, respectively. These inferred values represent a twofold increase in the mass and a twofold decrease in theage as compared to standard evolutionary models. Such a result highlights the need for constraining the contributionsof cool and warm regions of young stellar atmospheres when estimating Tef f and L? to infer masses and ages as wellas the necessity for models to account for the effects of these regions on the early evolution of low-mass stars.

36. Line emission from filaments in molecular clouds

F. D. Priestley, D. Arzoumanian, A. P. Whitworth F Filamentary structures are often identified in column density

maps of molecular clouds, and appear to be important for both low- and high-mass star formation. Theoretically, thesestructures are expected to form in regions where the supersonic cloud-scale turbulent velocity field converges. While
this model of filament formation successfully reproduces several of their properties derived from column densities, it
is unclear whether it can also reproduce their kinematic features. We use a combination of hydrodynamical, chemical
and radiative transfer modelling to predict the emission properties of these dynamically-forming filaments in the 13 CO,
HCN and N2 H+ J = 1 − 0 rotational lines. The results are largely in agreement with observations; in particular, line
widths are typically subsonic to transonic, even for filaments which have formed from highly supersonic inflows. If theobserved filaments are formed dynamically, as our results suggest, no equilibrium analysis is possible, and simulations
which presuppose the existence of a filament are likely to produce unrealistic results.

37. Planet formation via pebble accretion in externally photoevaporating discs

Lin Qiao, Gavin A. L. Coleman, Thomas J. Haworth F We demonstrate that planet formation via pebble accretionis sensitive to external photoevaporation of the outer disc. In pebble accretion, planets grow by accreting from a flux ofsolids (pebbles) that radially drift inwards from the pebble production front. If external photoevaporation truncates theouter disc fast enough, it can shorten the time before the pebble production front reaches the disc outer edge, cutting
off the supply of pebble flux for accretion, hence limiting the pebble mass reservoir for planet growth. Conversely,
cloud shielding can protect the disc from strong external photoevaporation and preserve the pebble reservoir. Because
grain growth and drift can occur quickly, shielding even on a short time-scale (<1 Myr) can have a non-linear impact
on the properties of planets growing by pebble accretion. For example a 10−3 M⊕ planetary seed at 25 au stays
at 25 au with a lunar mass if the disc is immediately irradiated by a 103 G0 field, but grows and migrates to beapproximately Earth-like in both mass and orbital radius if the disc is shielded for just 1 Myr. In NGC 2024, external
photoevaporation is thought to happen to discs that are <0.5 Myr old, which coupled with the results here suggeststhat the exact planetary parameters can be very sensitive to the star forming environment. Universal shielding fortime-scales of at least ∼ 1.5 Myr would be required to completely nullify the environmental impact on planetaryarchitectures.

38. Mapping the distribution of OB stars and associations in Auriga

Alexis L. Quintana, Nicholas J. Wright, Robin D. Jeffries F OB associations are important probes of recent starformation and Galactic structure. In this study, we focus on the Auriga constellation, an important region of starformation due to its numerous young stars, star-forming regions and open clusters. We show using Gaia data that its
two previously documented OB associations, Aur OB1 and OB2, are too extended in proper motion and distance to begenuine associations, encouraging us to revisit the census of OB associations in Auriga with modern techniques. We
identify 5617 candidate OB stars across the region using photometry, astrometry and our SED fitting code, grouping
these into 5 high-confidence OB associations using HDBSCAN. Three of these are replacements to the historical pair ofassociations - Aur OB2 is divided between a foreground and a background association - while the other two associations
are completely new. We connect these OB associations to the surrounding open clusters and star-forming regions,analyse them physically and kinematically, constraining their ages through a combination of 3D kinematic traceback,14

the position of their members in the HR diagram and their connection to clusters of known age. Four of these OB
associations are expanding, with kinematic ages up to a few tens of Myr. Finally, we identify an age gradient in theregion spanning several associations that coincides with the motion of the Perseus spiral arm over the last ∼20 Myr
across the field of view.

39. Modelling the early mass-ejection in jet driven protostellar outflows. Lessons from Cep
E
P. R. Rivera-Ortiz, A. de A. Schutzer, B. Lefloch, A. Gusdorf F We have used the axisymmetric chemo-hydrodynamical code WALKIMYA-2D to numerically model and reproduce the physical and CO emission propertiesof the jet-driven outflow from the intermediate-mass protostar Cep E, which was observed at ∼ 800au resolution in the
CO J = 2 → 1 line with the IRAM interferometer. Our simulations take into account the observational constraints
available on the physical structure of the protostellar envelope to provide constraints on the dynamics of the innerprotostellar environment from the study of the outflow/jet propagation away from the launch region. WALKIMYA-2D
successfully reproduces the main qualitative and quantitative features of the Cep E outflow and the jet kinematics,
naturally accounting for their time variability. Signatures of internal shocks are detected as knots along the jet. In theearly times of the ejection process, the young emitted knots interact with the dense circumstellar envelope throughhigh-velocity, dissociative shocks, which strongly decrease the CO gas abundance in the jet. As time proceeds, theknots propagate more smoothly through the envelope and dissociative shocks disappear after ∼ 103 yr. The distribution of CO abundance along the jet shows that the latter bears memory of the early dissociative phase in the courseof its propagation. Analysis of the velocity field shows that the jet material mainly consists of gas entrained from thecircumstellar envelope and accelerated away from the protostar at 700 au scale. As a result, the overall jet mass loss
rate appears higher than the actual mass ejection rate by a factor ∼ 3. Numerical modeling of the Cep E jet-driven
outflow and comparison with the CO observations have allowed us to peer into the outflow formation mechanism with
unprecedented detail and to retrieve the history of the mass-loss events that have shaped the outflow.

40. Eccentricity Growth of Massive Planets inside Cavities of Protoplanetary Discs

Marina M. Romanova, Alexander V. Koldoba, Galina V. Ustyugova, Dong Lai, Richard V. E. Lovelace F We
carry out hydrodynamical simulations to study the eccentricity growth of a 1-30 Jupiter mass planet located inside
the fixed cavity of a protoplanetary disc. The planet exchanges energy and angular momentum with the disc atresonant locations, and its eccentricity grows due to Lindblad resonances. We observe several phases of eccentricity
growth where different eccentric Lindblad resonances dominate from 1:3 up to 3:5. The maximum values of eccentricity
reached in our simulations are 0.65-0.75. We calculate the eccentricity growth rate for different planet masses and discparameters and derive analytical dependencies on these parameters. We observe that the growth rate is proportional toboth the planet’s mass and the characteristic disc mass for a wide range of parameters. In a separate set of simulations,
we derived the width of the 1:3 Lindblad resonance.

The beta Pictoris system: Setting constraints on the planet and the disk structures at
41. mid-IR wavelengths with NEAR
Nour Skaf, Anthony Boccaletti, Eric Pantin, Philippe Thebault, Quentin Kral, Camilla Danielski, Raphael
Galicher, Julien Milli, Anne-Marie Lagrange, Clement Baruteau, Matthew Kenworthy, Olivier Absil, Maud
Langlois, Johan Olofsson, Gael Chauvin, Nuria Huelamo, Philippe Delorme, Benjamin Charnay, Olivier Guyon,
Michael Bonnefoy, Faustine Cantalloube, H. Jens Hoeijmakers, Ulli Käufl, Markus Kasper, Anne-Lise Maire,
Mathilde Mâlin, Ralf Siebenmorgen, Ignas Snellen, Gerard Zins F [abridged] We analyzed mid-infrared high-contrast coronagraphic images of the beta Pictoris system, taking advantage of the NEAR experiment using the
VLT/VISIR instrument. The goal of our analysis is to investigate both the detection of the planet beta Pictoris b
and of the disk features at mid-IR wavelengths. In addition, by combining several epochs of observation, we expect toconstrain the position of the known clumps and improve our knowledge on the dynamics of the disk. To evaluate theplanet b flux contribution, we extracted the photometry and compared it to the flux published in the literature. In
addition, we used previous data from T-ReCS and VISIR, to study the evolution of the position of the southwest clumpthat was initially observed in the planetary disk back in 2003. While we did not detect the planet b, we were able toput constraints on the presence of circumplanetary material, ruling out the equivalent of a Saturn-like planetary ringaround the planet. The disk presents several noticeable structures, including the known southwest clump. Using a15

16-year baseline, sampled with five epochs of observations, we were able to examine the evolution of the clump: theclump orbits in a Keplerian motion with an sma of 56.1+-0.4 au. In addition to the known clump, the images clearlyshow the presence of a second clump on the northeast side of the disk and fainter and closer structures that are yet
to be confirmed. We found correlations between the CO clumps detected with ALMA and the mid-IR images. If
the circumplanetary material were located at the Roche radius, the maximum amount of dust determined from theflux upper limit around beta Pictoris b would correspond to the mass of an asteroid of 5 km in diameter. Finally,
the Keplerian motion of the southwestern clump is possibly indicative of a yet-to-be-detected planet or signals thepresence of a vortex.

42. Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROONXJames Sikora, Jason Rowe, Saugata Barat, Jacob L. Bean, Madison Brady, Jean-Michel Désert, Adina D.
Feinstein, Emily A. Gilbert, Gregory Henry, David Kasper, Déreck-Alexandre Lizotte, Michael R. B. Matesic,
Vatsal Panwar, Andreas Seifahrt, Hinna Shivkumar, Gudmundur Stefánsson, Julian Stürmer F The early K-

type T-Tauri star, V1298 Tau (V = 10 mag, age ≈ 20 − 30 Myr) hosts four transiting planets with radii ranging from
4.9 − 9.6 R⊕ . The three inner planets have orbital periods of ≈ 8 − 24 d while the outer planet’s period is poorly
constrained by single transits observed with K2 and TESS. Planets b, c, and d are proto-sub-Neptunes that may beundergoing significant mass loss. Depending on the stellar activity and planet masses, they are expected to evolve into
super-Earths/sub-Neptunes that bound the radius valley. Here we present results of a joint transit and radial velocity(RV) modelling analysis, which includes recently obtained TESS photometry and MAROON-X RV measurements.
Assuming circular orbits, we obtain a low-significance (≈ 2σ) RV detection of planet c implying a mass of 19.8+9.3−8.9 M⊕and a conservative 2σ upper limit of < 39 M⊕ . For planets b and d, we derive 2σ upper limits of Mb < 159 M⊕ andMd < 41 M⊕ . For planet e, plausible discrete periods of Pe > 55.4 d are ruled out at a 3σ level while seven solutions
with 43.3 < Pe /d < 55.4 are consistent with the most probable 46.768131 ± 000076 d solution within 3σ. Adopting
the most probable solution yields a 2.6σ RV detection with mass a of 0.66 ± 0.26 MJup . Comparing the updated
mass and radius constraints with planetary evolution and interior structure models shows that planets b, d, and e areconsistent with predictions for young gas-rich planets and that planet c is consistent with having a water-rich corewith a substantial (∼ 5% by mass) H2 envelope.

43. An infrared study of the high-mass, multi-stage star-forming region IRAS 12272-6240

Mauricio Tapia, Paolo Persi, Miguel Roth, Davide Elia F IRAS 12272-6240 is a complex star forming region witha compact massive dense clump and several associated masers, located at a well-determined distance of d = 9.3 kpc
from the Sun. For this study, we obtained sub-arcsec broad- and narrow-band near-IR imaging and low-resolution
spectroscopy with the Baade/Magellan telescope and its camera PANIC. Mosaics of size 2 × 2 square arcmin in
the JHKs bands and with narrow-band filters centred in the 2.12 µm H2 and 2.17 µm Brγ lines were analysed in
combination with HI-GAL/Herschel and archive IRAC/Spitzer and WISE observations. We found that the compact
dense clump houses two Class I YSOs that probably form a 21 kAU-wide binary system. Its combined 1 to 1200
µm SED is consistent with an O9V central star with a 10−2 M disc and a 1.3 × 104 M dust envelope. Its totalluminosity is 8.5 × 104 L . A series of shocked H2 emission knots are found in its close vicinity, confirming the presenceof outflows. IRAS 12272-6240 is at the centre of an embedded cluster with a mean age of 1 Myr and 2.6 pc in sizethat contains more than 150 stars. At its nucleus, we found a more compact and considerably younger sub-cluster
containing the YSOs. We also identified and classified the O-type central stars of two dusty radio/IR HII regions
flanking the protostars. Our results confirm that these elements form a single giant young complex where massive starformation processes started some 1 million years ago and is still active.

44. Constraints on the non-thermal desorption of methanol in the cold core LDN 429-C

A. Taillard, V. Wakelam, P. Gratier, E. Dartois, M. Chabot, J. A. Noble, J. V. Keane, A. C. A. Boogert, D.
Harsono F Cold cores are an early step of star formation, characterized by densities > 104 cm−3 , low temperatures (<15 K), and very low external UV radiation. We investigate the physico-chemical processes at play to tracing the originof molecules that are predominantly formed via reactions on dust grain surfaces. We observed the cold core LDN 429-C
with the NOEMA interferometer and the IRAM 30m single dish telescope in order to obtain the gas-phase abundancesof key species, including CO and CH3 OH. Comparing the observed gas phase of methanol to its solid phase previously

16observed with Spitzer allows us to put quantitative constraints on the efficiency of the non-thermal desorption ofthis species. With physical parameters determined from available Herschel data, we computed abundance maps of
11 detected molecules with a non-local thermal equilibrium radiative transfer model. These observations allowed us
to probe the molecular abundances as a function of density and visual extinction, with the variation in temperature
being restrained between 12 and 18 K. We then compared the observed abundances to the predictions of the Nautilus
astrochemical model. We find that all molecules have lower abundances at high densities and visual extinctions withrespect to lower density regions, except for methanol. Comparing these observations with a grid of chemical models
based on the local physical conditions, we were able to reproduce these observations, allowing only the parameter time
to vary. Comparing the observed gas-phase abundance of methanol with previous measurements of the methanol ice,
we estimate a non-thermal desorption efficiency between 0.002% and 0.09%, increasing with density. The apparent
increase in the desorption efficiency cannot be reproduced by our model unless the yield of cosmic-ray sputtering isaltered due to the ice composition varying as a function of density.

Spin of protoplanets generated by pebble accretion: Influences of protoplanet-induced
45. gas flow
Kohsuke Takaoka, Ayumu Kuwahara, Shigeru Ida, Hiroyuki Kurokawa F We investigate the spin state of a

protoplanet during the pebble accretion influenced by the gas flow in the gravitational potential of the protoplanet
and how it depends on the planetary mass, the headwind speed, the distance from the host star, and the pebble
size. We perform nonisothermal three-dimensional hydrodynamical simulations in a local frame to obtain the gas
flow around the planet. We then numerically integrate three-dimensional orbits of pebbles under the obtained gas
flow. Finally, assuming uniform spatial distribution of incoming pebbles, we calculate net spin by summing up specificangular momentum that individual pebbles transfer to the protoplanet at impacts. We find that a protoplanet withthe envelope acquires prograde net spin rotation regardless of the planetary mass, the pebble size, and the headwind
speed of the gas. This is because accreting pebbles are dragged by the envelope that commonly has prograde rotation.
As the planetary mass or orbital radius increases, the envelope is thicker and the prograde rotation is faster, resulting
in faster net prograde spin. When the dimensionless thermal mass of the planet, m = RBondi /H, where RBondi and H
are the Bondi radius and the disk gas scale height, is larger than a certain critical mass (m & 0.3 at 0.1 au or m & 0.1
at 1 au), the spin rotation exceeds the breakup one. The predicted spin frequency reaches the breakup one at theplanetary mass miso,rot ∼ 0.1 (a/1 au)−1/2 (where a is the orbital radius), suggesting that the protoplanet cannot growbeyond miso,rot . It is consistent with the Earth’s current mass and could help the formation of the Moon by a giant
impact on fast-spinning proto-Earth.

into the Interior of Hot Cores with ALMA (DIHCA). III: The Chemical Link
46. Digging
between NH2 CHO, HNCO, and H2 CO
Kotomi Taniguchi, Patricio Sanhueza, Fernando A. Olguin, Prasanta Gorai, Ankan Das, Fumitaka Nakamura,
Masao Saito, Qizhou Zhang, Xing Lu, Shanghuo Li, Huei-Ru Vivien Chen F We have analyzed the NH2 CHO,

HNCO, H2 CO, and CH3 CN (13 CH3 CN) molecular lines at an angular resolution of ∼ 0.300 obtained by the Atacama
Large Millimeter/submillimeter Array (ALMA) Band 6 toward 30 high-mass star-forming regions. The NH2 CHO
emission has been detected in 23 regions, while the other species have been detected toward 29 regions. A total of
44 hot molecular cores (HMCs) have been identified using the moment 0 maps of the CH3 CN line. The fractional
abundances of the four species have been derived at each HMC. In order to investigate pure chemical relationships,
we have conducted a partial correlation test to exclude the effect of temperature. Strong positive correlations between
NH2 CHO and HNCO (ρ = 0.89) and between NH2 CHO and H2 CO (0.84) have been found. These strong correlations
indicate their direct chemical links; dual-cyclic hydrogen addition and abstraction reactions between HNCO andNH2 CHO and gas-phase formation of NH2 CHO from H2 CO. Chemical models including these reactions can reproduce
the observed abundances in our target sources.

47. Collision of molecular outflows in the L1448–C system

Iván Toledano–Juárez, Eduardo de la Fuente, Miguel A. Trinidad, Daniel Tafoya, Alberto Nigoche–Netro F

We present a study of the central zone of the star-forming region L1448 at 217–230 GHz (∼ 1.3 mm) using ALMA
observations. Our study focuses on the detection of proto-stellar molecular outflows and the interaction with thesurrounding medium toward sources L1448–C(N) and L1448–C(S). Both sources exhibit continuum emission, with17

L1448–C(N) being the brightest one. Based on its spectral index and the associated bipolar outflow, the continuum
emission is the most likely to be associated with a circumstellar disk. The 12 CO(J=2→1) and SiO(J= 5→4) emissions
associated with L1448–C(N) trace a bipolar outflow and a jet oriented along the northwest-southeast direction. The
12
CO(J=2→1) outflow for L1448–C(N) has a wide-open angle and a V-shape morphology. The SiO jet is highly
collimated and has an axial extent comparable with the 12 CO(J=2→1) emission. There is not SiO(J= 5→4) emission
towards L1448–C(S), but there is 12 CO(J=2→1) emission. The observations revealed that the red-shifted lobes of the
12
CO(J=2→1) outflows of L1448–C(N) and L1448–C(S) are colliding. As a result of this interaction, the L1448-C(S)lobe seems to be truncated. The collision of the molecular outflows is also hinted by the SiO(J= 5→4) emission, wherethe velocity dispersion increases significantly in the interaction zone. We also investigated whether it could be possiblethat this collision triggers the formation of new stars in the L1448–C system.

48. Survey of Orion Disks with ALMA (SODA) II: UV-driven disk mass loss in L1641 andL1647
S. E. van Terwisga, A. Hacar F External FUV irradiation of protoplanetary disks has an important impact on
their evolution and ability to form planets. However, nearby (<300 pc) star-forming regions lack sufficiently massive
young stars, while the Trapezium Cluster and NGC 2024 have complicated star-formation histories and their O-typestars’ intense radiation fields (> 104 G0 ) destroy disks too quickly to study this process in detail. We study disk
mass loss driven by intermediate (10 - 1000 G0 ) FUV radiation fields in L1641 and L1647, where it is driven by morecommon A0 and B-type stars. Using the large (N=873) sample size offered by the Survey of Orion Disks with ALMA(SODA), we search for trends in the median disk dust mass with FUV field strength across the region as a whole andin two separate regions containing a large number of irradiated disks. For radiation fields between 1 - 100 G0 , themedian disk mass in the most irradiated disks drops by a factor ∼ 2 over the lifetime of the region, while the 95th
percentile of disk masses drops by a factor 4 over this range. This effect is present in multiple populations of stars,
and localized in space, to within 2 pc of ionizing stars. We fit an empirical irradiation - disk mass relation for the+0.18
first time: Mdust,median = −1.3+0.14−0.13 log10 (FFUV /G0 ) + 5.2−0.19 . This work demonstrates that even intermediate FUV
radiation fields have a significant impact on the evolution of protoplanetary disks.

49. Investigating the asymmetric chemistry in the disk around the young star HD 142527

Milou Temmink, Alice S. Booth, Nienke van der Marel, Ewine F. van Dishoeck F The atmospheric composition ofplanets is determined by the chemistry of the disks in which they form. Studying the gas-phase molecular compositionof disks thus allows us to infer what the atmospheric composition of forming planets might be. Recent observations of
the IRS 48 disk have shown that (asymmetric) dust traps can directly impact the observable chemistry, through radial
and vertical transport, and the sublimation of ices. The asymmetric HD 142527 disk provides another good opportunity
to investigate the role of dust traps in setting the disk’s chemical composition. In this work, we use archival ALMA
observations of the HD 142527 disk to obtain an as large as possible molecular inventory, which allows us to investigate
the possible influence of the asymmetric dust trap on the disk’s chemistry. We present the first ALMA detections of[C I], 13C18O, DCO+, H2CO and additional transition of HCO+ and CS in this disk. In addition, we have acquired
upper limits for non-detected species such as SO and CH3OH. For the majority of the observed molecules, a decrementin the emission at the location of the dust trap is found. For the main CO isotopologues continuum over-subtraction
likely causes the observed asymmetry, while for CS and HCN we propose that the observed asymmetries are likely
due to shadows cast by the misaligned inner disk. As the emission of the observed molecules is not co-spatial with thedust trap and no SO or CH3OH are found, thermal sublimation of icy mantles does not appear to play a major rolein changing the gas-phase composition of the outer disk in HD 142527 disk. Using our observations of 13C18O and
DCO+ and a RADMC-3D model, we determine the CO snowline to be located beyond the dust traps, favouring cold
gas-phase formation of H2CO, rather than the hydrogenation of CO-ice and subsequent sublimation.

Magnetohydrodynamic Model of Late Accretion onto a Protoplanetary Disk: Cloudlet
50. Encounter Event
Masaki Unno, Tomoyuki Hanawa, Shinsuke Takasao F Recent observations suggest late accretion, which is generally

nonaxisymmetric, onto protoplanetary disks. We investigated nonaxisymmetric late accretion considering the effects
of magnetic fields. Our model assumes a cloudlet encounter event at a few hundred au scale, where a magnetized gas
clump (cloudlet) encounters a protoplanetary disk. We studied how the cloudlet size and the magnetic field strength18affect the rotational velocity profile in the disk after the cloudlet encounter. The results show that a magnetic field caneither decelerate or accelerate the rotational motion of the cloudlet material, primarily depending on the relative size ofthe cloudlet to the disk thickness. When the cloudlet size is comparable to or smaller than the disk thickness, magnetic
fields only decelerate the rotation of the colliding cloudlet material. However, if the cloudlet size is larger than thedisk thickness, the colliding cloudlet material can be super-Keplerian as a result of magnetic acceleration. We foundthat the vertical velocity shear of the cloudlet produces a magnetic tension force that increases the rotational velocity.
The acceleration mechanism operates when the initial plasma β is β . 2 × 101 . Our study shows that magnetic fields
modify the properties of spirals formed by tidal effects. These findings may be important for interpreting observationsof late accretion.

A systematic survey of millimetre-wavelength flaring variability of Young Stellar Objects
51. in the Orion Nebula Cluster
J. Vargas-González, J. Forbrich, V. M. Rivilla, K. M. Menten, M. Güdel, A. Hacar F High-energy processes are

ubiquitous even in the earliest stages of protostellar evolution. Motivated by the results of our systematic search forintense centimeter radio flares in Young Stellar Objects (YSOs) and by rare findings of strong millimeter-wavelengthvariability, we have conducted a systematic search for such variability in the Orion Nebula Cluster (ONC) using
Atacama Large Millimeter/submillimeter Array (ALMA). Rapid variability on timescales of minutes to hours in the(centimeter)millimeter-wavelength range indicates (gyro)synchrotron radiation. Additionally, mass accretion will also
affect the millimeter-wavelength luminosity but typically on longer timescales. Beyond studies of individual YSOs, ourcharacterization of strong millimeter-wavelength variability with ALMA in the ONC sets first systematic constraints
on the occurrence of such variability in a large number of YSOs (∼130). We report the discovery of an order ofmagnitude millimeter-flare within just a few minutes from a known YSO previously reported as a radio flaring sourceat cm-wavelengths (the "ORBS” source). We also present an assessment of the systematic variability effects causedby the use of time-sliced imaging of a complex region. These are mostly due to the impact of a changing synthesized
beam throughout the observations. We use simulated ALMA observations to reproduce and quantify these effects andset a lower limit for the variability that can be studied using our method in a complex region such as the ONC. Our
results demonstrate that the utility of time domain analysis of YSOs extends into the millimeter-wavelength range,potentially interfering with the conversion of observed fluxes into dust masses.

52. Gas and star kinematics in cloud-cloud collisions

James Wurster, Ian A. Bonnell F We model the collision of molecular clouds to investigate the role of the initialproperties on the remnants. Our clouds collide and evolve in a background medium that is approximately ten times lessdense than the clouds, and we show that this relatively dense background is dynamically important for the evolutionof the collision remnants. Given the motion of the clouds and the remnants through the background, we develop,
implement, and introduce dynamic boundary conditions. We investigate the effect of the initial cloud mass, velocity,internal turbulence, and impact angle. The initial velocity and its velocity components have the largest affect on theremnant. This affects the spatial extent of the remnant, which affects the number of resulting star clusters and the
distribution of their masses. The less extended remnants tend to have fewer, but more massive, clusters. Unlike theclusters, the gas distributions are relatively insensitive to the initial conditions, both the distribution of the bulk gas
properties and the gas clumps. In general, cloud collisions are relatively insensitive to their initial conditions whenmodelled hydrodynamically in a dynamically important background medium.

53. Imaging Molecular Outflow in Massive Star-forming Regions with HNCO Lines

Jinjin Xie, Juan Li, Junzhi Wang, Shu Liu, Kai Yang, Donghui Quan, Siqi Zheng, Yuqiang Li, Jingwen Wu,
Yan Duan, Di Li F Protostellar outflows are considered a signpost of star formation. These outflows can cause

shocks in the molecular gas and are typically traced by the line wings of certain molecules. HNCO (4–3) has been
regarded as a shock tracer because of the high abundance in shocked regions. Here we present the first imaging resultsof HNCO (4–3) line wings toward nine sources in a sample of twenty three massive star-forming regions using the
IRAM 30 m telescope. We adopt the velocity range of the full width of HC3 N (10–9) and H13 CO+ (1–0) emissions as
the central emission values, beyond which the emission from HNCO (4–3) is considered to be from line wings. The
spatial distributions of the red- and/or blue-lobes of HNCO (4–3) emission nicely associate with those lobes of HCO+
(1–0) in most of the sources. High intensity ratios of HNCO (4–3) to HCO+ (1–0) are obtained in the line wings.

19

The derived column density ratios of HNCO to HCO+ are consistent with those previously observed towards massive
star-forming regions. These results provide direct evidence that HNCO could trace outflow in massive star-forming
regions. This work also implies that the formation of some HNCO molecules is related to shock, either on the grainsurface or within the shocked gas.

54. Denoising Diffusion Probabilistic Models to Predict the Density of Molecular Clouds
Duo Xu, Jonathan C. Tan, Chia-Jung Hsu, Ye Zhu F We introduce the state-of-the-art deep learning Denoising

Diffusion Probabilistic Model (DDPM) as a method to infer the volume or number density of giant molecular clouds(GMCs) from projected mass surface density maps. We adopt magnetohydrodynamic simulations with different
global magnetic field strengths and large-scale dynamics, i.e., noncolliding and colliding GMCs. We train a diffusion
model on both mass surface density maps and their corresponding mass-weighted number density maps from different
viewing angles for all the simulations. We compare the diffusion model performance with a more traditional empiricaltwo-component and three-component power-law fitting method and with a more traditional neural network machinelearning approach (CASI-2D). We conclude that the diffusion model achieves an order of magnitude improvement on
the accuracy of predicting number density compared to that by other methods. We apply the diffusion method tosome example astronomical column density maps of Taurus and the Infrared Dark Clouds (IRDCs) G28.37+0.07 andG35.39-0.33 to produce maps of their mean volume densities.

55. Eccentric Dust Ring in the IRS 48 Transition Disk

Haifeng Yang, Manuel Fernandez-Lopez, Zhi-Yun Li, Ian W. Stephens, Leslie W. Looney, Zhe-Yu Daniel Lin,
Rachel Harrison F Crescent-shaped structures in transition disks hold the key to studying the putative companions

to the central stars. The dust dynamics, especially that of different grain sizes, is important to understanding the roleof pressure bumps in planet formation. In this work, we present deep dust continuum observation with high resolution
towards the Oph IRS 48 system. For the first time, we are able to significantly trace and detect emission along 95%
of the ring crossing the crescent-shaped structure. The ring is highly eccentric with an eccentricity of 0.27. The flux
density contrast between the peak of the flux and its counter part along the ring is ∼ 270. In addition, we detect
a compact emission toward the central star. If the emission is an inner circumstellar disk inside the cavity, it has aradius of at most a couple of astronomical units with a dust mass of 1.5 × 10−8 M , or 0.005 M⊕ . We also discuss theimplications of the potential eccentric orbit on the proper motion of the crescent, the putative secondary companion,
and the asymmetry in velocity maps.

Testing protoplanetary disc evolution with CO fluxes. A proof of concept in Lupus and56. Upper Sco
Francesco Zagaria, Stefano Facchini, Anna Miotello, Carlo F. Manara, Claudia Toci, Cathie J. Clarke F The
Atacama Large Millimeter/submillimeter Array (ALMA) revolutionised our understanding of protoplanetary discs.
However, the available data have not given conclusive answers yet on the underlying disc evolution mechanisms(viscosity or MHD winds). Improving upon the current results, mostly based on the analysis of disc sizes, is difficult
because larger, deeper and higher angular resolution surveys would be required, which could be prohibitive evenfor ALMA. In this Letter, we introduce an alternative method to study disc evolution based on 12 CO fluxes. In
fact, fluxes can be readily collected using less time-consuming, lower resolution observations, while tracing the same
disc physico-chemical processes as sizes: assuming that 12 CO is optically thick, fluxes scale with the disc surface
area. We developed a semi-analytical model to compute 12 CO fluxes and benchmarked it against the results of DALI
thermochemical models, recovering an agreement within a factor of three. As a proof of concept we compared ourmodels with Lupus and Upper Sco data, taking advantage of the increased samples, by a factor 1.3 (Lupus) and 3.6(Upper Sco), when studying fluxes instead of sizes. Models and data agree well only if CO depletion is considered.
However, the uncertainties on the initial conditions limited our interpretation of the observations. Our new method
can be used to design future ad hoc observational strategies to collect better data and give conclusive answers on disc20

evolution.

21