The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 365 — 31 May 2023
Editor: João Alveswww.starformation.news

Links to sections

Interviews
Meetings

Reviews
Jobs

Perspective
New PhDs

Favorite objects
Announcements

Archive
Books

Cover image caption
L1688, the closest embedded stellar cluster to Earth, as seen by the VISTA telescope at ESO’s Paranal Observatory in Chile.
The cluster contains hundreds of young stars, including several protostars that are less than a million years old. The image
is a color composite (J, H, and Ks ), covers about 2×2 deg2 on the sky, and constitutes a small portion of ESO Public Survey
VISIONS, a sub-arcsec near-infrared atlas of all nearby (d < 500 pc) star formation complexes accessible from the southernhemisphere.
Credits: ESO, S. Meingast et al. 2023

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.

An analysis of the turbulence in the central region of M 42 (Orion Nebula) II: homogeneity and power-spectrum analyses
G. A. Anorve-Zeferino F In this second communication we continue our analysis of the turbulence in the Huygens

Region of the Orion Nebula (M 42). We calculate the associated transverse structure functions up to order 8-th
and find that the higher-order transverse structure functions are almost proportional to the second-order transverse
structure function: we find that after proper normalisation, the higher-order transverse structure functions only differ
by very small deviations from the second-order transverse structure function in a sub-interval of the inertial range.
We demonstrate that this implies that the turbulence in the Huygens Region is quasi-log-homogeneous, or to a better
degree of approximation, binomially weighted log-homogeneous in the statistical sense, this implies that there is some
type of invariant statistical structure in the velocity field of the Huygens Region. We also obtain and analyse thepower-spectrum of the turbulent field and find that it displays a large tail that follows very approximately two powerlaws, one of the form E(k) ∝ k −2.7 for the initial side of the tail, and one of the form E(k) ∝ k −1 for the end of thetail. We find that the power-law with exponent β ∼ −2.7 corresponds to spatial scales of 0.0301–0.6450 pc. We findthat the exponent of the first power-law β ∼ −2.7 is related to the exponent α2 of the second-order structure functionin the inertial range. We interpret the second power-law with exponent β ∼ −1 as an indicator of viscous-dissipative
processes occurring at scales of δr = 1–5 pixels which correspond to spatial scales of 0.00043–0.00215 pc.

2.

Gas distribution in ODISEA sources from ALMA long-baseline observations in
12
CO(2-1)
Juanita Antilen, Simon Casassus, Lucas A. Cieza, Camilo González-Ruilova F The 12 CO rotational lines inprotoplanetary discs are good tracers of the total spatial extension of the gas component, and potentially planet-discinteractions. We present ALMA long baseline observations of the 12 CO(2-1) line of ten protoplanetary discs fromthe Ophiuchus DIsc Survey Employing ALMA (ODISEA) project, aiming to set constraints on the gas distributionof these sources. The position angle of the gaseous disc can be inferred for five sources using high-velocity channels,
which trace the gas in the inner part of the disc. We compare the high-velocity PAs to the orientations inferred fromthe continuum, representative of the orientation over ∼ 53 to 256 au in these resolved discs. We find a significant

2difference in orientation for DoAr 44, which is evidence of a tilted inner disc. Eight discs show evidence of gas inside
inner dust cavities or gaps, and the disc of ISO-Oph 196 is not detected in 12 CO(2-1), except for the compact signal
located inside its dust cavity. Our observations also point out a possible outflow in WLY 2-63.

3.

Kinematics and stability of high-mass protostellar disk candidates at sub-arcsecond
resolution – Insights from the IRAM NOEMA large program CORE
Aida Ahmadi, H. Beuther, F. Bosco, C. Gieser, S. Suri, J. C. Mottram, R. Kuiper, Th. Henning, Á. SánchezMonge, H. Linz, R. E. Pudritz, D. Semenov, J. M. Winters, T. Möller, M. T. Beltrán, T. Csengeri, R. GalvánMadrid, K. G. Johnston, E. Keto, P. D. Klaassen, S. Leurini, S. N. Longmore, S. L. Lumsden, L. T. Maud,
L. Moscadelli, A. Palau, T. Peters, S. E. Ragan, J. S. Urquhart, Q. Zhang, H. Zinnecker F The fragmentation

mode of high-mass molecular clumps and the accretion processes that form the most massive stars (M & 8M ) arestill not well understood. To this end, we have undertaken a large observational program (CORE) making use ofinterferometric observations from the Northern Extended Millimetre Array (NOEMA) for a sample of 20 luminous(L > 104 L ) protostellar objects in the 1.37 mm wavelength regime in both continuum and line emission, reaching∼0.4" resolution (800 au at 2 kpc). Using the dense gas tracer CH3 CN, we find velocity gradients across 13 cores
perpendicular to the directions of bipolar molecular outflows, making them excellent disk candidates. Specific angularmomentum (j) radial profiles are on average ∼ 10−3 km /s pc and follow j ∝ r1.7 , consistent with a poorly resolved
rotating and infalling envelope/disk model. Fitting the velocity profiles with a Keplerian model, we find protostellar
masses in the range of ∼ 10 − 25 M . Modelling the level population of CH3 CN lines, we present temperature maps
and find median gas temperatures in the range 70 − 210 K. We create Toomre Q maps to study the stability of thedisks and find almost all (11 of 13) disk candidates to be prone to fragmentation due to gravitational instabilities at thescales probed by our observations. In particular, disks with masses greater than ∼ 10 − 20% of the mass of their host(proto)stars are Toomre unstable, and more luminous protostellar objects tend to have disks that are more massive
and hence more prone to fragmentation. Our finings show that most disks around high-mass protostars are prone todisk fragmentation early in their formation due to their high disk to stellar mass ratio. This impacts the accretion
evolution of high-mass protostars which will have significant implications for the formation of the most massive stars.

4.

H2 CN/H2 NC abundance ratio: a new potential temperature tracer for the interstellar
mediumDavid San Andrés, Laura Colzi, Víctor M. Rivilla, Juan García de la Concepción, Mattia Melosso, Jesús
Martín-Pintado, Izaskun Jiménez-Serra, Shaoshan Zeng, Sergio Martín, Miguel A. Requena-Torres F The

H2 NC radical is the high-energy metastable isomer of H2 CN radical, which has been recently detected for the firsttime in the interstellar medium towards a handful of cold galactic sources, besides a warm galaxy in front of the PKS
1830-211 quasar. These detections have shown that the H2 CN/H2 NC isomeric ratio, likewise the HCN/HNC ratio,
might increase with the kinetic temperature (Tkin ), but the shortage of them in warm sources still prevents us toconfirm this hypothesis and shed light about their chemistry. In this work, we present the first detection of H2 CN
and H2 NC towards a warm galactic source, the G+0.693-0.027 molecular cloud (with Tkin > 70 K), using IRAM 30m
observations. We have detected multiple hyperfine components of the NKa Kc = 101 − 000 and 202 − 101 transitions. We
derived molecular abundances with respect to H2 of (6.8±1.3)×10−11 for H2 CN and of (3.1±0.7)×10−11 for H2 NC,
and a H2 CN/H2 NC abundance ratio of 2.2±0.5. These detections confirm that the H2 CN/H2 NC ratio is &2 forsources with Tkin > 70 K, larger than the ∼1 ratios previously found in colder cores (Tkin ∼ 10 K). This isomericratio dependence with temperature cannot be fully explained with the currently proposed gas-phase formation anddestruction pathways. Grain surface reactions, including the H2 NC → H2 CN isomerization, deserve consideration
to explain the higher isomeric ratios and H2 CN abundances observed in warm sources, where the molecules can bedesorbed into the gas phase through thermal and/or shock-induced mechanisms.

5. Spectroscopic substellar initial mass function of NGC 2244
V. Almendros-Abad, K. Mužić, H. Bouy, A. Bayo, A. Scholz, K. Peña Ramírez, A. Moitinho, K. Kubiak, R.
Schöedel, R. Barač, P. Brčić, J. Ascenso, R. Jayawardhana F We aim at characterizing the low-mass (sub)stellar

population of the central portion (2.4 pc2 ) of the ∼2 Myr old cluster NGC 2244 using near infrared spectroscopy. By
studying this cluster, characterized by a low stellar density and numerous OB stars, we aim at exploring the effectthat OB stars may have on the production of BDs. We obtain near infrared HK spectroscopy of 85 faint candidate3

members of NGC 2244. We derive the spectral type and extinction by comparison with spectral templates. We evaluate
cluster membership using three gravity-sensitive spectral indices based on the shape of the H-band. Furthermore, we
evaluate the infrared excess from Spitzer of all the candidate members of the cluster. Finally, we estimate the massof all the candidate members of the cluster and derive the initial mass function, star-to-BD number ratio and disk
fraction. The initial mass function is well represented by a power law (dN/dM ∝ M −α ) below 0.4 M , with a slope
α = 0.7-1.1 depending on the fitted mass range. We calculate a star-to-BD number ratio of 2.2-2.8. We find thelow-mass population of NGC 2244 to be consistent with nearby star-forming regions, although it is at the high-end of
BD production. We find BDs in NGC 2244 to be on average closer to OB stars than to low-mass stars, which could
potentially be the first evidence of OB stars affecting the formation of BDs. We find a disk fraction of all the memberswith spectral type later than K0 of 39±9% which is lower than typical values found in nearby star-forming regions ofsimilar ages.

6.

Fullerenes in the circumstellar medium of Herbig Ae/Be stars: Insights from the Spitzer
mid-infrared spectral catalog
R. Arun, Blesson Mathew, P. Manoj, G. Maheswar, B. Shridharan, Sreeja S. Kartha, Mayank Narang F This

study presents the largest mid-infrared spectral catalog of Herbig Ae/Be stars to date, containing the Spitzer Infrared
Spectrograph spectra of 126 stars. Based on the catalog analysis, two prominent infrared vibrational modes of C60
bands at 17.4 µm and 18.9 µm are detected in the spectra of nine sources, while 7.0 µm feature is identified in the
spectra of HD 319896. The spectral index analysis and the comparison of the known sources with C60 features indicatedthat there exist two different types of emission classes among the sample of stars. The infrared spectra of six Herbig
Ae/Be stars in this study resemble that of reflection nebulae, and their association with previously known reflection
nebulae is confirmed. In the case of three Herbig Ae/Be stars we report the tentative evidence of C60 emission features
originating from the circumstellar disk or nearby diffused emission region. The detection fraction of C60 in the total
HAeBe star sample is ∼ 7%, whereas the detection fraction is 30% for HAeBe stars associated with nebulosity. In
the catalog, C60 is exclusively present in the circumstellar regions of B type Herbig Ae/Be stars, with no evidenceof its presence detected in stars with later spectral types. The present study has increased the number of youngstellar objects and reflection nebulae detected with C60 multifold, which can help in understanding the excitation andformation pathway of the species.

7. Constraints on star formation in Orion A from Gaia

Jairo A. Alzate, Gustavo Bruzual, Marina Kounkel, Gladis Magris, Lee Hartmann, Nuria Calvet, Lyra Cao

F We develop statistical methods within a Bayesian framework to infer the star formation history from photometricsurveys of pre-main sequence populations. Our procedures include correcting for biases due to extinction in magnitudelimited surveys, and using distributions from subsets of stars with individual extinction measurements. We also makemodest corrections for unresolved binaries. We apply our methods to samples of populations with Gaia photometry in
the Orion A molecular cloud. Using two well-established sets of evolutionary tracks, we find that, although our sample
is incomplete at youngest ages due to extinction, star formation has proceeded in Orion A at a relatively constantrate between ages of about 0.3 and 5 Myr, in contrast to other studies suggesting multiple epochs of star formation.
Similar results are obtained for a set of tracks that attempt to take the effects of strong magnetic fields into account.
We also find no evidence for a well-constrained "birthline" that would result from low-mass stars appearing first along
the deuterium-burning main sequence, especially using the magnetic evolutionary tracks. While our methods havebeen developed to deal with Gaia data, they may be useful for analyzing other photometric surveys of star-forming
regions.

8. Inner edges of planetesimal belts: collisionally eroded or truncated?
Amaia Imaz Blanco, Sebastian Marino, Luca Matrà, Mark Booth, John Carpenter, Virginie Faramaz, Thomas
Henning, A. Meredith Hughes, Grant M. Kennedy, Sebastián Pérez, Luca Ricci, Mark C. Wyatt F The radial

structure of debris discs can encode important information about their dynamical and collisional history. In this paper
we present a 3-phase analytical model to analyse the collisional evolution of solids in debris discs, focusing on theirjoint radial and temporal dependence. Consistent with previous models, we find that as the largest planetesimals
reach collisional equilibrium in the inner regions, the surface density of dust and solids becomes proportional to ∼ r2
within a certain critical radius. We present simple equations to estimate the critical radius and surface density of dust4

as a function of the maximum planetesimal size and initial surface density in solids (and vice versa). We apply thismodel to ALMA observations of 7 wide debris discs. We use both parametric and non-parametric modelling to test
if their inner edges are shallow and consistent with collisional evolution. We find that 4 out of 7 have inner edges
consistent with collisional evolution. Three of these would require small maximum planetesimal sizes below 10 km,
with HR 8799’s disc potentially lacking solids larger than a few centimeters. The remaining systems have inner edges
that are much sharper, which requires maximum planetesimal sizes & 10 km. Their sharp inner edges suggest they
could have been truncated by planets, which JWST could detect. In the context of our model, we find that the 7
discs require surface densities below a Minimum Mass Solar Nebula, avoiding the so-called disc mass problem. Finally,
during the modelling of HD 107146 we discover that its wide gap is split into two narrower ones, which could be due
to two low-mass planets formed within the disc.

FU Orionis disk outburst: evidence for a gravitational instability scenario triggered in
9. a magnetically dead zone
G. Bourdarot, J-P. Berger, G. Lesur, K. Perraut, F. Malbet, R. Millan-Gabet, J-B. Le Bouquin, R. GarciaLopez, J. D. Monnier, A. Labdon, S. Kraus, L. Labadie, A. Aarnio F Context: FUors outbursts are a crucial

stage of accretion in young stars. However a complete mechanism at the origin of the outburst still remains missing.
Aims: We aim at constraining the instability mechanism in FU Orionis star itself, by directly probing the size andthe evolution in time of the outburst region with near-infrared interferometry, and to confront it to physical models of
this region. Methods: FU Orionis has been a regular target of near-infrared interferometry. In this paper, we analyze
more than 20 years of interferometric observations to perform a temporal monitoring of the region of the outburst, andcompare it to the spatial structure deduced from 1D MHD simulations. Results: We measure from the interferometricobservations that the size variation of the outburst region is compatible with a constant or slightly decreasing size overtime in the H and K band. The temporal variation and the mean sizes are consistently reproduced by our 1D MHD
simulations. We find that the most compatible scenario is a model of an outburst occurring in a magnetically layered
disk, where a Magneto-Rotational Instability (MRI) is triggered by a Gravitational Instability (GI) at the outer edgeof a dead-zone. The scenario of a pure Thermal Instability (TI) fails to reproduce our interferometric sizes since it
can only be sustained in a very compact zone of the disk <0.1 AU. The scenario of MRI-GI could be compatible withan external perturbation enhancing the GI, such as tidal interactions with a stellar companion, or a planet at theouter edge of the dead-zone. Conclusions: The layered disk model driven by MRI turbulence is favored to interpretthe spatial structure and temporal evolution of FU Orionis outburst region. Understanding this phase gives a crucial
link between the early phase of disk evolution and the process of planet formation in the first inner AUs.

10. High Resolution Observations of HI in the IC 63 Reflection Nebula

L. Bonne, B-G Andersson, R. Minchin, A. Soam, J. Yaldaei, K. Kulas, J. Karoly, L. B. G. Knee, S. Kumar,
N. Roy F Photodissociation regions (PDRs), where the (far-)ultraviolet light from hot young stars interact with thegas in surrounding molecular clouds, provide laboratories for understanding the nature and role of feedback by starformation on the interstellar medium. While the general nature of PDRs is well understood - at least under simplified
conditions - the detailed dynamics and chemistry of these regions, including gas clumping, evolution over time etc.
can be very complex. We present interferometric observations of the 21 cm atomic hydrogen line, combined with [CII]
158 µm observations, towards the nearby reflection nebula IC 63. We find a clumpy HI structure in the PDR, anda ring morphology for the HI emission at the tip of IC 63. We further unveil kinematic substructure, of the order of
1 km s−1 , in the PDR layers and several legs that will disperse IC 63 in <0.5 Myr. We find that the dynamics in the
PDR explain the observed clumpy HI distribution and lack of a well-defined HI/H2 transition front. However, it iscurrently not possible to conclude whether HI self-absorption (HISA) and non-equilibrium chemistry also contributeto this clumpy morphology and missing HI/H2 transition front.

11. A heat-wave of accretion energy traced by masers in the G358-MM1 high-mass protostar

R. A. Burns, K. Sugiyama, T. Hirota, Kee-Tae Kim, A. M. Sobolev, B. Stecklum, G. C. MacLeod, Y. Yonekura,
M. Olech, G. Orosz, S. P. Ellingsen, L. Hyland, A. Caratti o Garatti, C. Brogan, T. R. Hunter, C. Phillips,
S. P. van den Heever, J. Eislöffel, H. Linz, G. Surcis, J. O. Chibueze, W. Baan, B. Kramer F High-mass stars

are thought to accumulate much of their mass via short, infrequent bursts of disk-aided accretion. Such accretion
events are rare and difficult to observe directly but are known to drive enhanced maser emission. In this Letter5

we report high-resolution, multi-epoch methanol maser observations toward G358.93-0.03 which reveal an interesting
phenomenon; the sub-luminal propagation of a thermal radiation "heat-wave" emanating from an accreting high-mass
proto-star. The extreme transformation of the maser emission implies a sudden intensification of thermal infrared
radiation from within the inner (40 mas, 270 au) region. Subsequently, methanol masers trace the radial passage ofthermal radiation through the environment at ≥ 4-8% the speed of light. Such a high translocation rate contrasts withthe ≤ 10 km s−1 physical gas motions of methanol masers typically observed using very long baseline interferometry(VLBI). The observed scenario can readily be attributed to an accretion event in the high-mass proto-star G358.930.03-MM1. While being the third case in its class, G358.93-0.03-MM1 exhibits unique attributes hinting at a possible‘zoo’ of accretion burst types. These results promote the advantages of maser observations in understanding high-massstar formation, both through single-dish maser monitoring campaigns and via their international cooperation as VLBI
arrays.

12.

A Keplerian disk with a four-arm spiral birthing an episodically accreting high-mass
protostar
R. A. Burns, Y. Uno, N. Sakai, J. Blanchard, Z. Rosli, G. Orosz, Y. Yonekura, Y. Tanabe, K. Sugiyama, T.
Hirota, Kee-Tae Kim, A. Aberfelds, A. E. Volvach, A. Bartkiewicz, A. Caratti o Garatti, A. M. Sobolev, B.
Stecklum, C. Brogan, C. Phillips, D. A. Ladeyschikov, D. Johnstone, G. Surcis, G. C. MacLeod, H. Linz, J. O.
Chibueze, J. Brand, J. Eislöffel, L. Hyland, L. Uscanga, M. Olech, M. Durjasz, O. Bayandina, S. Breen, S. P.
Ellingsen, S. P. van den Heever, T. R. Hunter, X. Chen F High-mass protostars (M? > 8 M ) are thought to gain

the majority of their mass via short, intense bursts of growth. This episodic accretion is thought to be facilitated bygravitationally unstable and subsequently inhomogeneous accretion disks. Limitations of observational capabilities,
paired with a lack of observed accretion burst events has withheld affirmative confirmation of the association between
disk accretion, instability and the accretion burst phenomenon in high-mass protostars. Following its 2019 accretion
burst, a heat-wave driven by a burst of radiation propagated outward from the high-mass protostar G358.93-0.03-MM1.
Six VLBI (very long baseline interferometry) observations of the raditively pumped 6.7 GHz methanol maser wereconducted during this period, tracing ever increasing disk radii as the heat-wave propagated outward. Concatenating
the VLBI maps provided a sparsely sampled, milliarcsecond view of the spatio-kinematics of the accretion disk coveringa physical range of ∼ 50 - 900 AU. We term this observational approach ‘heat-wave mapping’. We report the discovery
of a Keplerian accretion disk with a spatially resolved four-arm spiral pattern around G358.93-0.03-MM1. This result
positively implicates disk accretion and spiral arm instabilities into the episodic accretion high-mass star formation
paradigm.

13.

Three-Dimensional Dust Stirring by a Giant Planet Embedded in a Protoplanetary Disk
Fabian Binkert, Judit Szulágyi, Til Birnstiel F The motion of solid particles embedded in gaseous protoplanetarydisks is influenced by turbulent fluctuations. Consequently, the dynamics of moderately to weakly coupled solids can be
distinctly different from the dynamics of the gas. Additionally, gravitational perturbations from an embedded planet
can further impact the dynamics of solids. In this work, we investigate the combined effects of turbulent fluctuations
and planetary dust stirring in a protoplanetary disk on three-dimensional dust morphology and on synthetic ALMA
continuum observations. We carry out 3D radiative two-fluid (gas+1-mm-dust) hydrodynamic simulations in which
we explicitly model the gravitational perturbation of a Jupiter-mass planet. We derived a new momentum-conserving
turbulent diffusion model that introduces a turbulent pressure to the pressureless dust fluid to capture the turbulent
transport of dust. The model implicitly captures the effects of orbital oscillations and reproduces the theoretically
predicted vertical settling-diffusion equilibrium. We find a Jupiter-mass planet to produce distinct and large-scale
three-dimensional flow structures in the mm-size dust, which vary strongly in space. We quantify these effects by
locally measuring an effective vertical diffusivity (equivalent alpha) and find azimuthally averaged values in a rangeδeff ∼ 5 · 10−3 − 2 · 10−2 and local peaks at values of up to δeff ∼ 3 · 10−1 . In synthetic ALMA continuum observations of
inclined disks, we find effects of turbulent diffusion to be observable, especially at disk edges, and effects of planetary
dust stirring in edge-on observations.

614. Unveiling the formation of the massive DR21 ridge

L. Bonne, S. Bontemps, N. Schneider, R. Simon, S. D. Clarke, T. Csengeri, E. Chambers, U. Graf, J. M.
Jackson, R. Klein, Y. Okada, A. G. G. M. Tielens, M. Tiwari F We present new 13 CO(1-0), C18 O(1-0), HCO+ (1-0) and H13 CO+ (1-0) maps from the IRAM 30m telescope, and a spectrally-resolved [CII] 158 µm map observed with
the SOFIA telescope towards the massive DR21 cloud. This traces the kinematics from low- to high-density gas in thecloud which allows to constrain the formation scenario of the high-mass star forming DR21 ridge. The molecular line
data reveals that the sub-filaments are systematically redshifted relative to the dense ridge. We demonstrate that [CII]
unveils the surrounding CO-poor gas of the dense filaments in the DR21 cloud. We also show that this surrounding
gas is organized in a flattened cloud with curved redshifted dynamics perpendicular to the ridge. The sub-filaments
thus form in this curved and flattened mass reservoir. A virial analysis of the different lines indicates that self-gravity
should drive the evolution of the ridge and surrounding cloud. Combining all results we propose that bending of themagnetic field, due to the interaction with a mostly atomic colliding cloud, explains the velocity field and resulting
mass accretion on the ridge. This is remarkably similar to what was found for at least two nearby low-mass filaments.
We tentatively propose that this scenario might be a widespread mechanism to initiate star formation in the MilkyWay. However, in contrast to low-mass clouds, gravitational collapse plays a role on the pc scale of the DR21 ridge
because of the higher density. This allows more effective mass collection at the centers of collapse and should facilitate
massive cluster formation.

15.

On the interaction of pebble accreting embryos with the gaseous disc: importance ofthermal forces
S. Cornejo, F. S. Masset, F. J. Sánchez-Salcedo F A planetary embryo embedded in a gaseous disc can grow bypebble accretion while subjected to a gravitational force from the disc that changes its orbital elements. Usually, thatforce is considered to arise from the Lindblad and corotation resonances with the embryo. However, more important
contributions exist for low-mass planets. Radiative thermal diffusion in the vicinity of embryos yields an additional
contribution to the disc’s force that damps the eccentricity and inclination much more vigorously than the resonantinteraction with the disc, and that in general induces fast inward migration. In addition, the irradiation of the discby a hot embryo gives rise to an additional contribution that excites eccentricity and inclination, and induces outward
migration. Which of the two contributions dominates depends on the embryo’s luminosity. We assess the importanceof these contributions (termed thermal forces) on the dynamics and growth of a set of pebble-accreting embryos
initially of Martian mass, by means of N-body simulations that include analytic expressions for the disc’s force. We
find very different outcomes for the embryos subjected to thermal forces and those subjected only to resonant forces.
Importantly, we find that the median final mass of the embryos subjected to thermal forces is nearly independent of
the metallicity, whereas this mass roughly scales with the metallicity when they are subjected only to resonant forces.
These results can be explained by the strong damping of eccentricity and inclination at low metallicity, which enhances
the embryos’ accretion efficiency.

16.

Magnetic Fields and Fragmentation of Filaments in the Hub of California-X
Eun Jung Chung, Chang Won Lee, Woojin Kwon, Mario Tafalla, Shinyoung Kim, Archana Soam, Jungyeon
Cho F We present 850 µm polarization and C18 O(3 − 2) molecular line observations toward the X-shaped nebulain the California molecular cloud using the JCMT SCUBA-2/POL-2 and HARP instruments. The 850 µm emission
shows that the observed region includes two elongated filamentary structures (Fil1 and Fil2) having chains of regularly
spaced cores. We measured the mass per unit length of the filament and found that Fil1 and Fil2 are thermally superand subcritical, respectively, but both are subcritical if nonthermal turbulence is considered. The mean projectedspacings (∆S̄) of cores in Fil1 and Fil2 are 0.13 and 0.16 pc, respectively. ∆S̄ are smaller than 4×filament width
expected in the classical cylinder fragmentation model. The large-scale magnetic field orientations shown by Planck
are perpendicular to the long axes of Fil1 and Fil2, while those in the filaments obtained from the high-resolution
polarization data of JCMT are disturbed, but those in Fil1 tend to have longitudinal orientations. Using the modified
Davis-Chandrasekhar-Fermi (DCF) method, we estimated the magnetic field strengths (Bpos ) of filaments which are
110±80 and 90±60 µG. We calculated the gravitational, kinematic, and magnetic energies of the filaments, and foundthat the fraction of magnetic energy is larger than 60 % in both filaments. We propose that a dominant magnetic
energy may lead the filament to be fragmented into aligned cores as suggested by Tang et al., and a shorter core
spacing can be due to a projection effect via the inclined geometry of filaments or due to a non-negligible, longitudinalmagnetic fields in case of Fil1.
7

17.

The spatial distribution of an aromatic molecule, C6H5CN, in cold dark cloud TMC-1
J. Cernicharo, B. Tercero, N. Marcelino, M. Agundez, P. de Vicente F We present a highly sensitive 2D line surveyof TMC-1 obtained with the Yebes 40m radio telescope in the Q-band (31.13-49.53 GHz). These maps cover a regionof 320 arcsec x 320 arcsec centred on the position of the QUIJOTE line survey with a spatial sampling of 20 arcsec.
The region covering 240 arcsec x 240 arcsec, where a longer integration time was used, shows a homogenous sensitivityof 2-4 mK across the band. We present in this work the first determination of the spatial extent of benzonitrile(C6H5CN), which follows that of cyanopolyynes rather well, but differs significantly from that of the radicals CnH and
CnN. We definitively conclude that aromatic species in TMC-1 are formed from chemical reactions involving smaller
species in the densest zones of the cloud.

18.

Discovery of two rotational modulation periods from a young hierarchical triple system
Yu-Tao Chen, Hai-Jun Tian, Min Fang, Xiao-Xiong Zuo, Sarah A. Bird, Di Liu, Xin-Yu Zhu, Peng Zhang,
Gao-Chao Liu, Sheng Cui F GW Ori is a young hierarchical triple system located in λ Orionis, consisting of abinary (GW Ori A and B), a tertiary star (GW Ori C) and a rare circumtriple disk. Due to the limited data withpoor accuracy, several short-period signals were detected in this system, but the values from different studies are notfully consistent. As one of the most successful transiting surveys, the Transiting Exoplanet Survey Satellite (TESS)
provides an unprecedented opportunity to make a comprehensive periodic analysis of GW Ori. In this work we discover
two significant modulation signals by analyzing the light curves of GW Ori’s four observations from TESS, i.e., 3.02
± 0.15 d and 1.92 ± 0.06 d, which are very likely to be the rotational periods caused by starspot modulation on the
primary and secondary components, respectively. We calculate the inclinations of GW Ori A and B according to thetwo rotational periods. The results suggest that the rotational plane of GW Ori A and B and the orbital plane of thebinary are almost coplanar. We also discuss the aperiodic features in the light curves; these may be related to unstableaccretion. The light curves of GW Ori also include a third (possible) modulation signal with a period of 2.51±0.09 d,
but the third is neither quite stable nor statistically significant.

19. 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.

20. Updated Inventory of Carbon Monoxide in The Taurus Molecular Cloud
Yan Duan, Di Li, Laurent Pagani, Paul F. Goldsmith, Tao-Chung Ching, Chen Wang, Jinjin Xie F The mostextensive survey of carbon monoxide (CO) gas in the Taurus molecular cloud relied on 12 CO and 13 CO J = 1 → 0
emission only, distinguishing the region where 12 CO is detected without 13 CO (named mask 1 region) from the one
where both are detected (mask 2 region). We have taken advantage of recent 12 CO J = 3 → 2 JCMT observations
where they include mask 1 regions to estimate density, temperature, and N (CO) with a LVG model. This represents
1395 pixels out of ∼1.2 million in the mark 1 region. Compared to Pineda et al. (2010) results, and assuming a Tkinof 30 K, we find a higher volume density of molecular hydrogen of 3.3× 103 cm−3 , compared to their 250-700 cm−3and a CO column density of 5.7× 1015 cm−2 , about a quarter of their value. The differences are important and show
the necessity to observe several CO transitions to better describe the intermediate region between the dense cloud8and the diffuse atomic medium. Future observations to extend the 12 CO J = 3 → 2 mapping further away from the13
CO-detected region comprising mask 1 are needed to revisit our understanding of the diffuse portions of dark clouds.

21. The surprising evolution of the shadow on the TW Hya disk
J. Debes, R. Nealon, R. Alexander, A. J. Weinberger, S. G. Wolff, D. Hines, J. Kastner, H. Jang-Condell, C.
Pinte, P. Plavchan, L. Pueyo F We report new total intensity visible light high contrast imaging of the TW Hya disktaken with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). This represents
the first published images of the disk with STIS since 2016, when a moving shadow on the disk surface was reported.
We continue to see the shadow moving in a counter-clockwise fashion, but in these new images the shadow has evolved
into two separate shadows, implying a change in behavior for the occulting structure. Based on radiative transfer
models of optically thick disk structures casting shadows, we infer that a plausible explanation for the change is that
there are now two misaligned components of the inner disk. The first of these disks is located between 5-6au with aninclination of 5.5 deg and PA of 170 deg, the second between 6-7au with and inclination of 7 deg and PA of 50 deg.
Finally, we speculate on the implications of the new shadow structure and determine that additional observations areneeded to disentangle the nature of TW Hya’s inner disk architecture.

22. High-resolution [O I] line spectral mapping of TW Hya supportive of magnetothermal
wind
Min Fang, Lile Wang, Gregory J. Herczeg, Jun Hashimoto, Ziyan Xu, Ahmed Nemer, Ilaria Pascucci, Sebastiaan Haffert, Yuhiko Aoyama F Disk winds are thought to play a critical role in the evolution and dispersal of

protoplanetary disks. The primary diagnostic of this physics is emission from the wind, especially in the low-velocity
component of the [O I] λ6300 line. However, the interpretation of the line is usually based on spectroscopy alone,which leads to confusion between magnetohydrodynamic winds and photoevaporative winds. Here, we report thatin high-resolution VLT/MUSE spectral mapping of TW Hya, 80 % of the [O ] emission is confined to within 1 AU
radially from the star. A generic model of a magnetothermal wind produces [O I] emission at the base of the windthat broadly matches the flux and the observed spatial and spectral profiles. The emission at large radii is much
fainter that predicted from models of photoevaporation, perhaps because the magnetothermal wind partially shields
the outer disk from energetic radiation from the central star. This result calls into question the assumed importanceof photoevaporation in disk dispersal predicted by models.

23. Implementation of Rare Isotopologues into Machine Learning of the Chemical Inventoryof the Solar-Type Protostellar Source IRAS 16293-2422
Zachary T. P. Fried, Kin Long Kelvin Lee, Alex N. Byrne, Brett A. McGuire F Machine learning techniques
have been previously used to model and predict column densities in the TMC-1 dark molecular cloud. In interstellar
sources further along the path of star formation, such as those where a protostar itself has been formed, the chemistry
is known to be drastically different from that of largely quiescent dark clouds. To that end, we have tested the abilityof various machine learning models to fit the column densities of the molecules detected in source B of the Class 0
protostellar system IRAS 16293-2422. By including a simple encoding of isotopic composition in our molecular feature
vectors, we also examine for the first time how well these models can replicate the isotopic ratios. Finally, we report
the predicted column densities of the chemically relevant molecules that may be excellent targets for radioastronomical
detection in IRAS 16293-2422B.

Tree-based solvers for adaptive mesh refinement code FLASH – IV: An X-ray radiation
24. scheme to couple discrete and diffuse X-ray emission sources to the thermochemistryof the interstellar medium
Brandt A. L. Gaches, Stefanie Walch, Richard Wünsch, Jonathan Mackey F X-ray radiation, in particularradiation between 0.1 keV and 10 keV, is evident from both point-like sources, such as compact objects and T-Tauri
young stellar objects, and extended emission from hot, cooling gas, such as in supernova remnants. The X-ray radiation
is absorbed by nearby gas, providing a source of both heating and ionization. While protoplanetary chemistry models
now often include X-ray emission from the central young stellar object, simulations of star-forming regions have yet toinclude X-ray emission coupled to the chemo-dynamical evolution of the gas. We present an extension of the TreeRay
reverse raytrace algorithm implemented in the Flash magneto-hydrodynamic code which enables the inclusion of X9

ray radiation from 0.1 keV < Eγ < 100 keV, dubbed XrayTheSpot. XrayTheSpot allows for the use of an arbitrary
number of bins, minimum and maximum energies, and both temperature-independent and temperature-dependentuser-defined cross sections, along with the ability to include both point and extended diffuse emission and is coupled
to the thermochemical evolution. We demonstrate the method with several multi-bin benchmarks testing the radiationtransfer solution and coupling to the thermochemistry. Finally, we show two example star formation science cases
for this module: X-ray emission from protostellar accretion irradiating an accretion disk and simulations of molecular
clouds with active chemistry, radiation pressure, protostellar radiation feedback from infrared to X-ray radiation.

25. The origin of dust polarization in the Orion Bar
Valentin J. M. Le Gouellec, B-G Andersson, Archana Soam, Thiébaut Schirmer, Joseph M. Michail, Enrique
Lopez-Rodriguez, Sophia Flores, David T. Chuss, John E. Vaillancourt, Thiem Hoang, Alex Lazarian F The

linear polarization of thermal dust emission provides a powerful tool to probe interstellar and circumstellar magnetic
fields, because aspherical grains tend to align themselves with magnetic field lines. While the Radiative Alignment
Torque (RAT) mechanism provides a theoretical framework to this phenomenon, some aspects of this alignment
mechanism still need to be quantitatively tested. One such aspect is the possibility that the reference alignment
direction changes from the magnetic field ("B-RAT") to the radiation field k-vector ("k-RAT") in areas of strong
radiation fields. We investigate this transition toward the Orion Bar PDR, using multi-wavelength SOFIA HAWC+
dust polarization observations. The polarization angle maps show that the radiation field direction is on average
not the preferred grain alignment axis. We constrain the grain sizes for which the transition from B-RAT to k-RAT
occur in the Orion Bar (grains > 0.1 µm toward the most irradiated locations), and explore the radiatively driven
rotational disruption that may take place in the high-radiation environment of the Bar for large grains. While thegrains susceptible to rotational disruption should be in supra-thermal rotation and aligned with the magnetic field,
k-RAT aligned grains would rotate at thermal velocities. We find that the grain size at which the alignment shifts
from B-RAT to k-RAT corresponds to grains too large to survive the rotational disruption. Therefore, we expect alarge fraction of grains to be aligned at supra-thermal rotation with the magnetic field, and potentially be subject torotational disruption depending on their tensile strength.

26.

Large-scale Velocity-coherent Filaments in the SEDIGISM Survey: Association with
Spiral Arms and Fraction of Dense Gas
Y. Ge, K. Wang, A. Duarte-Cabral, A. R. Pettitt, C. L. Dobbs, Á. Sánchez-Monge, K. R. Neralwar, J. S.
Urquhart, D. Colombo, E. Durán-Camacho, H. Beuther, L. Bronfman, A. J. Rigby, D. Eden, S. Neupane, P.
Barnes, T. Henning, A. Y. Yang F Context. Filamentary structures in the interstellar medium are closely related

to star formation. Dense gas mass fraction (DGMF) or clump formation efficiency in large-scale filaments possibly
determine their hosting star formation activities. Aims. We aim to automatically identify large-scale filaments,characterize them, investigate their association with Galactic structures, and study their DGMFs. Methods. We
use a modified minimum spanning tree (MST) algorithm to chain parsec-scale 13CO clumps previously extracted
from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) survey. The
MST connects nodes in a graph such that the sum of edge lengths is minimum. Modified MST also ensures velocity
coherence between nodes, so the identified filaments are coherent in position-position-velocity (PPV) space. Results.
We generate a catalog of 88 large-scale (> 10pc) filaments in the inner Galactic plane (with −60◦ < l < 18◦ and|b| < 0.5◦ ). These SEDIGISM filaments are larger and less dense than MST filaments previously identified from the
BGPS and ATLASGAL surveys. We find that eight of the filaments run along spiral arms and can be regarded as"bones" of the Milky Way. We also find three bones associated with the Local Spur in PPV space. By compiling 168
large-scale filaments with available DGMF across the Galaxy, an order of magnitude more than previously investigated,
we find that DGMFs do not correlate with Galactic location, but bones have higher DGMFs than other filaments.

27. Magnetic Activity-Rotation-Age-Mass Relations in Late Pre-main Sequence Stars

Konstantin V. Getman, Eric D. Feigelson, Gordon P. Garmire F We study the four-dimensional relationships

between magnetic activity, rotation, mass and age for solar-type stars in the age range 5-25Myr. This is the late-premain sequence (l-PMS) evolutionary phase when rapid changes in star’s interior may lead to the changes in magnetic
dynamo mechanisms. We carefully derive rotational periods and spot sizes for 471 members of several l-PMS open
clusters using photometric light curves from the Zwicky Transient Facility. Magnetic activity was measured in our

10previous Chandra-based study, and additional rotational data were obtained from other work. Several results emerge.
Mass-dependent evolution of rotation through the l-PMS phase agrees with astrophysical models of stellar angularmomentum changes, although the data point to a subpopulation of stars with slower initial rotations than commonly
assumed. There is a hint of the onset of unsaturated tachoclinal dependency of X-ray activity on rotation, as reported
by Argiroffi et al. (2016), but this result is not confidently confirmed. Both X-ray luminosity and star spot area
decrease approximately as t−1 for solar mass stars suggesting that spot magnetic fields are roughly constant andl-PMS stars follow the universal solar-scaling law between the X-ray luminosity and surface magnetic flux. Assuming
convective dynamos are dominant, theoretical magnetic fluxes fail to reveal the universal law for l-PMS stars thatenter late Henyey tracks. Altogether we emerge with a few lines of evidence suggesting that the transition from theturbulent to solar-type dynamo occurs at the later stages of l-PMS evolution as stars approach the Zero-Age Main
Sequence.

A deep optical survey of young stars in the Carina Nebula. I. – UBVRI photometric
28. data and fundamental parameters
Hyeonoh Hur, Beomdu Lim, Moo-Young Chun F We present the deep homogeneous U BV RI photometric dataof 135,071 stars down to V ∼ 23 mag and I 22 mag toward the Carina Nebula. These stars are cross-matched withthose from the previous surveys in the X-ray, near-infrared, and mid-infrared wavelengths as well as the Gaia Early
Data Release 3 (EDR3). This master catalog allows us to select reliable members and determine the fundamental
parameters distance, size, stellar density of stellar clusters in this star-forming region. We revisit the reddening toward
the nebula using the optical and the near-infrared colors of early-type stars. The foreground reddening [E(B-V)f g ] isdetermined to be 0.35+/-0.02, and it seems to follow the standard reddening law. On the other hand, the total-toselective extinction ratio of the intracluster medium (RV ,cl) decreases from the central region (Trumpler 14 and 16,
RV ,cl 4.5) to the northern region (Trumpler 15, RV ,cl 3.4). It implies that the central region is more dusty than thenorthern region. We find that the distance modulus of the Carina Nebula to be 11.9+/-0.3 mag (d = 2.4+/-0.35 kpc)
using a zero-age main-sequence fitting method, which is in good agreement with that derived from the Gaia EDR3
parallaxes. We also present the catalog of 3,331 pre-main-sequence (PMS) members and 14,974 PMS candidates down
to V 22 mag based on spectrophotometric properties of young stars at infrared, optical, and X-ray wavelengths.
From the spatial distribution of PMS members and PMS candidates, we confirm that the member selection is very
reliable down to faint stars. Our data will have a legacy value for follow-up studies with different scientific purposes.

29. Unveiling the initial conditions of open star cluster formation
C. J. Hao, Y. Xu, L. G. Hou, Z. H. Lin, Y. J. Li F Open clusters (OCs) are infrequent survivors of embeddedclusters gestated in molecular clouds. Up to now, little is known about the initial conditions for the formation ofOCs. Here, we studied this issue using high-precision astrometric parameters provided by Gaia data release 3. The
statistics show that the peculiar motion velocities of OCs vary little from infancy to old age, providing a remarkable
opportunity to use OCs to trace their progenitors. Adopting a dynamical method, we derived the masses of theprogenitor clumps where OCs were born, which have statistical characteristics comparable to previously known results
for clumps observed in the Galaxy. Moreover, the masses of the progenitor clumps of OCs indicate they should becapable of gestating massive O-type stars. In fact, after inspecting the observed OCs and O-type stars, we found that
there are many O-type stars in OCs. The destructive stellar feedback from O-type stars may disintegrate the vast
majority of embedded clusters, and only those sufficiently dense ones can survive as OCs.

30. The Disc Miner II: Revealing Gas substructures and Kinematic signatures from Planetdisc interaction through line profile analysis
Andres F. Izquierdo, Leonardo Testi, Stefano Facchini, Giovanni P. Rosotti, Ewine van Dishoeck, Lisa Wölfer,
Teresa Paneque-Carreño F [Abridged] The aim of this work is to identify potential signatures from planet-discinteraction in the circumstellar discs around MWC 480, HD 163296, AS 209, IM Lup, and GM Aur, through thestudy of molecular lines observed as part of the ALMA large program MAPS. Extended and localised perturbations
in velocity, line width, and intensity have been analysed jointly using the DISCMINER modelling framework, in threebright CO lines, 12CO, 13CO, and C18O J = 2 − 1, to provide a comprehensive summary of the kinematic andcolumn density substructures that planets might be actively sculpting in these discs. We find convincing evidence forthe presence of four giant planets located at wide orbits in three of the discs in the sample: two around HD 163296, one

11

in MWC 480, and one in AS 209. One of the planet candidates in HD 163296, P94, previously associated with velocity
signatures detected in lower velocity resolution 12CO data, is confirmed and linked to localised velocity and line
width perturbations in 13CO and C18O too. We highlight that line widths are also powerful tracers of planet-forming
sites as they are sensitive to turbulent motions triggered by planet-disc interactions. In MWC 480, we identified
non-axisymmetric line width enhancements around the radial separation of candidate planet-driven buoyancy spirals,
which we used to narrow the location of the possible planet to an orbital radius of R = 245 au and PA = 193◦ .
In the disc of AS 209, we found excess 12CO line widths centred at R = 210 au, PA = 151◦ , spanning around theimmediate vicinity of a circumplanetary disc candidate proposed previously, which further supports its presence. Our
simultaneous analysis of multiple tracers and observables aims to lay the groundwork for robust studies of molecularline properties focused on the search for young planets in discs.

Study of the long-term BV Rc Ic photometric variability of eight PMS stars in the young
31. open cluster Trumpler 37
Sunay Ibryamov, Gabriela Zidarova, Evgeni Semkov, Stoyanka Peneva F This paper reports results from our longterm BV (RI)c photometric CCD observations of eight pre-main-sequence stars collected from June 2008 to October
2022. These stars are located in the young open cluster Trumpler 37, in the field of GM Cephei. The observational
data indicate that all stars from our study exhibit variability in all-optical passbands, typical for young stars. In thispaper, we describe and discuss the photometric behavior of the stars and the possible reasons for their variability. For
two of the objects, we identified periodicity in their light variation.

A 3D physico-chemical model of a pre-stellar core. I. Environmental and structural
32. impact on the distribution of CH OH and c-C H
33 2
S. S. Jensen, S. Spezzano, P. Caselli, T. Grassi, T. Haugbølle F Pre-stellar cores represent the earliest stage ofthe star- and planet-formation process. By characterizing the physical and chemical structure of these cores we canestablish the initial conditions for star and planet formation and determine to what degree the chemical compositionof pre-stellar cores is inherited to the later stages. A 3D MHD model of a pre-stellar core embedded in a dynamic
star-forming cloud is post-processed using sequentially continuum radiative transfer, a gas-grain chemical model, anda line-radiative transfer model. Results are analyzed and compared to observations of CH3 OH and c-C3 H2 in L1544.
Nine different chemical models are compared to the observations to determine which initial conditions are compatible
with the observed chemical segregation in the prototypical pre-stellar core L1544. The model is able to reproduce
several aspects of the observed chemical differentiation in L1544. Extended methanol emission is shifted towards colder
and more shielded regions of the core envelope while c-C3 H2 emission overlaps with the dust continuum, consistent
with the observed chemical structure. Increasing the strength of the interstellar radiation field or the cosmic-ray
ionization rate with respect to the typical values assumed in nearby star-forming regions leads to synthetic maps thatare inconsistent with the observed chemical structure. Our model shows that the observed chemical dichotomy in L1544
can arise as a result of uneven illumination due to the asymmetrical structure of the 3D core and the environment
within which the core has formed. This highlights the importance of the 3D structure at the core-cloud transition on
the chemistry of pre-stellar cores.

33. FacetClumps: A Facet-based Molecular Clump Detection Algorithm

Yu Jiang, Zhiwei Chen, Sheng Zheng, Zhibo Jiang, Yao Huang, Shuguang Zeng, Xiangyun Zeng, Xiaoyu Luo

F A comprehensive understanding of molecular clumps is essential for investigating star formation. We present analgorithm for molecular clump detection, called FacetClumps. This algorithm uses a morphological approach to extract
signal regions from the original data. The Gaussian Facet model is employed to fit the signal regions, which enhances
the resistance to noise and the stability of the algorithm in diverse overlapping areas. The introduction of the extremum
determination theorem of multivariate functions offers theoretical guidance for automatically locating clump centers.
To guarantee that each clump is continuous, the signal regions are segmented into local regions based on gradient, andthen the local regions are clustered into the clump centers based on connectivity and minimum distance to identify theregional information of each clump. Experiments conducted with both simulated and synthetic data demonstrate that
FacetClumps exhibits great recall and precision rates, small location error and flux loss, a high consistency between
the region of detected clump and that of simulated clump, and is generally stable in various environments. Notably,
the recall rate of FacetClumps in the synthetic data, which comprises 13 CO (J = 1 − 0) emission line of the MWISP

12

within 11.7◦ ≤ l ≤ 13.4◦ , 0.22◦ ≤ b ≤ 1.05◦ and 5 km s−1 ≤ v ≤ 35 km s−1 and simulated clumps, reaches 90.2%.
Additionally, FacetClumps demonstrates satisfactory performance when applied to observational data.

34.

ALMA ACA study of the H2 S/OCS ratio in low-mass protostars
Tanya Kushwahaa, Maria N. Drozdovskaya, Łukasz Tychoniec, Benoît Tabone F The identification of the main

sulfur reservoir on its way from the diffuse interstellar medium to the cold dense star-forming cores and eventually to
protostars is a long-standing problem. Despite sulfur’s astrochemical relevance, the abundance of S-bearing molecules
in dense cores and regions around protostars is still insufficiently constrained. The goal of this investigation is toderive the gas-phase H2 S/OCS ratio for several low-mass protostars, which could provide crucial information about
the physical and chemical conditions in the birth cloud of Sun-like stars. Using ALMA ACA Band 6 observations,
H2 S, OCS, and their isotopologs are searched for in 10 Class 0/I protostars with different source properties such asage, mass, and environmental conditions. An LTE model is used to fit synthetic spectra to the detected lines andto derive the column densities based solely on optically thin lines. The H2 S and OCS column densities span fourorders of magnitude across the sample. The H2 S/OCS ratio is found to be in the range from 0.2 to above 9.7. IRAS
16293-2422 A and Ser-SMM3 have the lowest ratio, while BHR71-IRS1 has the highest. Only the H2 S/OCS ratioof BHR71-IRS1 agress within uncertainties with the ratio in comet 67P/C−G. The determined gas-phase H2 S/OCS
ratios can be below the upper limits on the solid-state ratios by as much as an order of magnitude. The H2 S/OCS
ratio depends significantly on the environment of the birth cloud, such as UV-irradiation and heating received prior to
the formation of a protostar. The highly isolated birth environment of BHR71-IRS1 is hypothesized to be the reason
for its high gaseous H2 S/OCS ratio due to lower rates of photoreactions and more efficient hydrogenation reactions
under such dark, cold conditions. The gaseous inventory of S-bearing molecules in BHR71-IRS1 appears to be mostsimilar to that of interstellar ices.

The interplay between pebble and planetesimal accretion in population synthesis models
35. and its role in giant planet formation
Andrin Kessler, Yann Alibert F In the core accretion scenario of planet formation, rocky cores grow by firstaccreting solids until they are massive enough to accrete gas. For giant planet formation this means that a massive
core must form within the lifetime of the gas disk. The accretion of roughly km-sized planetesimals and the accretionof mm-cm sized pebbles are typically discussed separately as the main solid accretion mechanisms. We investigate theinterplay between the two accretion processes in a disk containing both pebbles and planetesimals for planet formationin general and in the context of giant planet formation specifically. The goal is to disentangle and understand thefundamental interactions that arise in such hybrid pebble-planetesimal models. We combine a simple model of pebble
formation and accretion with a global model of planet formation which considers the accretion of planetesimals. We
compare synthetic populations of planets formed in disks composed of different amounts of pebbles and 600 meter
sized planetesimals. On a system-level, we study the formation pathway of giant planets in these disks. We findthat, in hybrid disks containing both pebbles and planetesimals, the formation of giant planets is strongly suppressed
whereas in a pebbles-only or planetesimals-only scenario, giant planets can form. We identify the heating associatedwith the accretion of up to 100 km sized planetesimals after the pebble accretion period to delay the runaway gas
accretion of massive cores. Coupled with strong inward type-I migration acting on these planets, this results in close-in
icy sub-Neptunes originating from the outer disk. We conclude that, in hybrid pebble-planetesimal scenarios, the lateaccretion of planetesimals is a critical factor in the giant planet formation process and that inward migration is more
efficient for planets in increasingly pebble dominated disks.

Impact of turbulence intensity and fragmentation velocity on dust particle size evolution
36. and non-ideal magnetohydrodynamics effects
Yoshihiro Kawasaki, Masahiro N. Machida F We investigate the influence of dust particle size evolution on non-ideal

magnetohydrodynamic effects during the collapsing phase of star-forming cores, taking both the turbulence intensity inthe collapsing cloud core and the fragmentation velocity of dust particles as parameters. When the turbulence intensity
is small, the dust particles do not grow significantly, and the non-ideal MHD effects work efficiently in high-density
regions. The dust particles rapidly grow in a strongly turbulent environment, while the efficiency of non-ideal MHD
effects in such an environment depends on the fragmentation velocity of the dust particles. When the fragmentation
velocity is small, turbulence promotes coagulation growth and collisional fragmentation of dust particles, producing

13

small dust particles. In this case, the adsorption of charged particles on the dust particle surfaces becomes efficientand the abundance of charged particles decreases, making non-ideal MHD effects effective at high densities. On theother hand, when the fragmentation velocity is high, dust particles are less likely to fragment, even if the turbulenceis strong. In this case, the production of small dust particles become inefficient and non-ideal MHD effects becomeless effective. We also investigate the effect of the dust composition on the star and disk formation processes. We
constrain the turbulence intensity of a collapsing core and the fragmentation velocity of dust for circumstellar disk
formation due to the dissipation of the magnetic field.

37.

Binary Formation in a 100 mum-dark Massive Core
Shuo Kong, Héctor G. Arce, John J. Tobin, Yichen Zhang, María José Maureira, Kaitlin M. Kratter, Thushara
G. S. Pillai F We report high-resolution ALMA observations toward a massive protostellar core C1-Sa (∼30 M )in the Dragon Infrared Dark Cloud. At the resolution of 140 AU, the core fragments into two kernels (C1-Sa1 andC1-Sa2) with a projected separation of ∼1400 AU along the elongation of C1-Sa, consistent with a Jeans lengthscale of ∼1100 AU. Radiative transfer modeling using RADEX indicates that the protostellar kernel C1-Sa1 has atemperature of ∼75 K and a mass of 0.55 M . C1-Sa1 also likely drives two bipolar outflows, one being parallelto the plane-of-the-sky. C1-Sa2 is not detected in line emission and does not show any outflow activity but exhibits
ortho-H2 D+ and N2 D+ emission in its vicinity, thus it is likely still starless. Assuming a 20 K temperature, C1-Sa2 has
a mass of 1.6 M . At a higher resolution of 96 AU, C1-Sa1 begins to show an irregular shape at the periphery, but noclear sign of multiple objects or disks. We suspect that C1-Sa1 hosts a tight binary with inclined disks and outflows.
Currently, one member of the binary is actively accreting while the accretion in the other is significantly reduced.
C1-Sa2 shows hints of fragmentation into two sub-kernels with similar masses, which requires further confirmation
with higher sensitivity.

38. Merger Conditions of Population III Protostar Binaries

Takanobu Kirihara, Hajime Susa, Takashi Hosokawa, Tomoya Kinugawa F Massive close binary stars with extremely small separations have been observed, and they are possible progenitors of gravitational-wave sources. The
evolution of massive binaries in the protostellar accretion stage is key to understanding their formation process. We,
therefore, investigate how close the protostars, consisting of a high-density core and a vast low-density envelope, canapproach each other but not coalesce. To investigate the coalescence conditions, we conduct smoothed particle hydrodynamics simulations following the evolution of equal-mass binaries with different initial separations. Since Population(Pop) I and III protostars have similar interior structures, we adopt a specific Pop III model with the mass and radiusof 7.75 M and 61.1 R obtained by the stellar evolution calculations. Our results show that the binary separation
decreases due to the transport of the orbital angular momentum to spin angular momentum. If the initial separationis less than about 80 per cent of the sum of the protostellar radius, the binary coalesces in a time shorter than the
tidal lock timescale. The mass loss up to the merging is . 3 per cent. After coalescence, the star rotates rapidly, andits interior structure is independent of the initial separation. We conclude that there must be some orbital shrinking
mechanism after the protostars contract to enter the zero-age main-sequence stage.

39. The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43

Janik Karoly and the JCMT BISTRO Survey team. F We present observations of polarized dust emission at 850 µm

from the L43 molecular cloud which sits in the Ophiuchus cloud complex. The data were taken using SCUBA-2/POL-2
on the James Clerk Maxwell Telescope as a part of the BISTRO large program. L43 is a dense (NH2 ∼ 1022 -1023 cm−2 )complex molecular cloud with a submillimetre-bright starless core and two protostellar sources. There appears to bean evolutionary gradient along the isolated filament that L43 is embedded within, with the most evolved source closest
to the Sco OB2 association. One of the protostars drives a CO outflow that has created a cavity to the southeast. We
see a magnetic field that appears to be aligned with the cavity walls of the outflow, suggesting interaction with theoutflow. We also find a magnetic field strength of up to ∼160±30 µG in the main starless core and up to ∼90±40 µG
in the more diffuse, extended region. These field strengths give magnetically super- and sub-critical values respectively
and both are found to be roughly trans-Alfvénic. We also present a new method of data reduction for these denser
but fainter objects like starless cores.

14

40. The influence of planetesimal fragmentation on planet formation
Nicolas Kaufmann, Yann Alibert F Context. The effects of planetesimal fragmentation on planet formation has beenstudied by various models on single embryos therefore neglecting concurrent effects mostly in the outer disk. They showthat planetesimal fragmentation can both hinder or aid planet formation due to the introduction of competing effects,
namely speeding up accretion and depleting the feeding zone of forming planets. Aims. We investigate the influence ofthe collisional fragmentation of planetesimals on the planet formation process using a population synthesis approach.
We aim to investigate its effects for a large set of initial conditions and also explore the consequences on the formationof multiple embryos in the same disk. Methods. We run global planet formation simulations including fragmentation,
drift and an improved ice line description. To do this we use a fragmentation model in our code. The initial conditions
for the simulations that are informed by observations are varied to generate synthetic exoplanet populations. Results.
Our synthetic populations show that depending on the typical size of solids generated in collisions, fragmentation intandem with the radial drift can either enhance or hinder planet formation. For larger fragments we see increased
accretion throughout the populations especially beyond the ice line. However, the shorter drift timescale of smaller
fragments, due to their stronger coupling to the gas, can hinder the formation process. Furthermore, beyond the iceline fragmentation promotes late growth when the damping by gas drag fades Conclusions. Fragmentation significantly
affects the planet formation process in various ways for all types of planet and warrants further investigation.

41. A Census of the TW Hya Association with Gaia

K. L. Luhman F I have used high-precision photometry and astrometry from the third data release of Gaia toperform a survey for members of the TW Hya association (TWA). I have identified candidate members that appear
to share similar kinematics and ages with bona fide members compiled by Gagne et al. (2017) and I have assessed
their membership using radial velocities and spectroscopic diagnostics of age from various sources. My new catalog
of adopted members contains 67 Gaia sources in 55 systems. The histogram of spectral types for TWA peaks near
M5 ( 0.15 Msun), resembling the distributions measured for other nearby young associations. The UVW velocities of
its members indicate that the association is expanding. The rate of expansion corresponds to an age of 9.6+0.9/-0.8
Myr. In a Gaia color-magnitude diagram, the members of TWA exhibit well-defined sequences of single stars andunresolved binary stars. The combined sequence of low-mass stars in TWA is indicative of an age of 11.4+1.3/-1.2
Myr when compared to the sequence for Upper Centaurus-Lupus/Lower Centaurus-Crux, for which an age of 20 Myr
is assumed. Based on these expansion and isochronal ages, I have adopted an age of 10+/-2 Myr for TWA. Finally,
I have used mid-infrared photometry from the Wide-field Infrared Survey Explorer to check for excess emission fromcircumstellar disks among the TWA members. Fourteen members have detected disks, all of which have been reported
in previous studies. The fraction of members at <=M6 (>=0.1 Msun) that have full, transitional, or evolved disks
is 10/52=0.19+0.08/-0.06. That value is similar to the fraction previously measured for the Upper Sco association,
which is roughly coeval with TWA.

42.

HI Self-absorption toward the Cygnus X North: From Atomic Filament to Molecular
Filament
Chong Li, Keping Qiu, Di Li, Hongchi Wang, Yue Cao, Junhao Liu, Yuehui Ma, Chenglin Yang F Using the HI

self-absorption data from the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we perform a study ofthe cold atomic gas in the Cygnus-X North region. The most remarkable HI cloud is characterized by a filamentary
structure, associated in space and in velocity with the principle molecular filament in the Cygnus-X North region. We
investigate the transition from the atomic filament to the molecular filament. We find that the HII regions Cygnus
OB2 and G081.920+00.138 play a critical role in compressing and shaping the atomic Cygnus-X North filament,
where the molecular filament subsequently forms. The cold HI in the DR21 filament has a much larger column density(N(HI) ∼ 1 × 1020 cm−2 ) than the theoretical value of the residual atomic gas (∼ 1 × 1019 cm−2 ), suggesting thatthe HI-to-H2 transition is still in progress. The timescale of the HI-to-H2 transition is estimated to be 3 × 105 yr,
which approximates the ages of massive protostars in the Cygnus-X North region. This implies that the formation ofmolecular clouds and massive stars may occur almost simultaneously in the DR21 filament, in accord with a pictureof rapid and dynamic cloud evolution.

15

Dust dynamics in current sheets within protoplanetary disks. I. Isothermal models
43. including ambipolar diffusion and Ohmic resistivity
U. Lebreuilly, M. -M. Mac Low, B. Commerçon, D. S. Ebel F Context: Chondrules originate from the reprocessingof dust grains. They are key building blocks of telluric planets, yet their formation, which must happen in strongly
localized regions of high temperature, remains poorly understood. Aims: We examine the dust spatial distribution nearregions of strong local heating produced by current sheets, as a step toward exploring a potential path for chondrule
formation. We further aim to investigate current sheet formation under various conditions in protoplanetary disks inthe presence of ambipolar diffusion and Ohmic resistivity and the effect of current sheet morphology on dust dynamics
in their vicinity. Methods: We use the RAMSES code including modules for non-ideal magnetohydrodynamics andsolution of the dynamics of multiple sizes of dust grains to compute unstratified shearing box simulations of current
sheet formation. We investigate, through seven models the effect of the ambipolar diffusion and Ohmic resistivity
strength, the initial density, and magnetic field, as well as the resolution and box size. Results: We find that current
sheets form in all our models, with typical widths of 0.001-0.01 AU and that strong dust fraction variations occur for
millimeter-sized grains. These variations are typically of an order of magnitude and up to two orders of magnitude
for the most favorable cases. We also show that the box size and resolution has a strong impact on the current sheet
distribution and intensity. Conclusions: The formation of current sheets that can intensely heat their surroundings
near strong dynamical dust fraction variations could have important implications for chondrule formation, as it appears
likely to happen in regions of large dust fraction.

44. The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). IX.
Physical Properties and Spatial Distribution of Cores in IRDCs
Kaho Morii, Patricio Sanhueza, Fumitaka Nakamura, Qizhou Zhang, Giovanni Sabatini, Henrik Beuther, Xing
Lu, Shanghuo Li, Guido Garay, James M. Jackson, Fernando A. Olguin, Daniel Tafoya, Ken’ichi Tatematsu,
Natsuko Izumi, Takeshi Sakai, Andrea Silva F The initial conditions found in infrared dark clouds (IRDCs)

provide insights on how high-mass stars and stellar clusters form. We have conducted high-angular resolution andhigh-sensitivity observations toward thirty-nine massive IRDC clumps, which have been mosaicked using the 12m and7m arrays from the Atacama Large Millimeter/submillimeter Array (ALMA). The targets are 70 µm dark massive(220-4900 M ), dense (>104 cm−3 ), and cold (∼10-20K) clumps located at distances between 2 and 6 kpc. We identify
an unprecedented number of 839 cores, with masses between 0.05 and 81 M using 1.3 mm dust continuum emission.
About 55% of the cores are low-mass (<1 M ), whereas .1We detect no high-mass prestellar cores. The most massive
cores (MMC) identified within individual clumps lack sufficient mass to form high-mass stars without additional mass
feeding. We find that the mass of the MMCs is correlated with the clump surface density, implying denser clumps
produce more massive cores and a larger number of cores. There is no significant mass segregation except for a few
tentative detections. In contrast, most clumps show segregation once the clump density is considered instead of mass.
Although the dust continuum emission resolves clumps in a network of filaments, some of which consist of hub-filament
systems, the majority of the MMCs are not found in the hubs. Our analysis shows that high-mass cores and MMCs
have no preferred location with respect to low-mass cores at the earliest stages of high-mass star formation.

45. Study of the bipolar jet of the YSO Th 28 with VLT/SINFONI: Jet morphology andH2 emission
S. Yu. Melnikov, P. A. Boley, N. S. Nikonova, A. Caratti o Garatti, R. Garcia Lopez, B. Stecklum, J. Eislöffel,
G. Weigelt F Context. The YSO Th 28 possesses a highly collimated jet, which clearly exhibits an asymmetricbrightness of its jet lobes at optical and NIR wavelengths. There may be asymmetry in the jet plasma parametersin opposite jet lobes (e.g. electron density, temperature, and outflow velocity). Aims. We examined the Th 28 jetin a 3"x3" where the jet material is collimated and accelerated. Our goal is to map the morphology and determine
its physical parameters to determine the physical origin of such asymmetries. M ethods. We present JHK-spectra ofTh 28 obtained with the SINFONI on the (VLT, ESO) in June-July 2015. Results. The [Fe II] emission originatesin collimated jet lobes. Two new axial knots are detected at 1" in the blue lobe and 1".2 in the red lobe. The H2radiation is emitted from an extended region with a radius of & 270 au, which is perpendicular to the jet. The PV
diagrams of the bright H2 lines reveal faint H2 emission along both jet lobes as well. The compact and faint H Iemission (Paβ and Brγ) comes from two regions, namely from a spherical region around the star and from the jetlobes. The size of the jet launching region is derived as 0".015 (∼3 au at 185 pc), and the initial opening angle of theTh 28 jet is ∼ 280 , which makes this jet substantially less collimated than most jets from other CTTs. Conclusions.
16

The emission in [Fe II], H2 , and H I lines suggests a morphology in which the ionised gas in the disc appears to be
disrupted by the jet. The resolved disc-like H2 emission most likely arises in the disc atmosphere from shocks caused
by a radial uncollimated wind. The asymmetry of the [Fe II] photocentre shifts with respect to the jet source arises in
the immediate vicinity of the driving source of Th28 and suggests that the observed brightness asymmetry is intrinsic
as well.

46.

A runaway T-Tauri star leaving an extended trail
Josep Martí, Pedro L. Luque-Escamilla, Estrella Sánchez-Ayaso F Aims. We address the problem of young stellar

objects that are found too far away from possible star formation sites. Different mechanisms have been proposed before
to explain this unexpected circumstance. The idea of high-velocity protostars is one of these mechanisms, althoughobservational support is not always easy to obtain. We aim to shed light on this issue after the serendipitous discovery
of a related stellar system. Methods. Following the inspection of archival infrared data, a peculiar anonymous star was
found that apparently heads a long tail that resembles a wake-like feature. We conducted a multiwavelength analysis
including photometry, astrometry, and spectroscopy. Together with theoretical physical considerations, this approachprovided a reasonable knowledge of the stellar age and kinematic properties, together with compelling indications
that the extended feature is indeed the signature of a high-velocity, or runaway, newborn star. Results. Our main
result is the discovery of a low-mass young stellar object that fits the concept of a runaway T-Tauri star that was
hypothesized several decades ago. In this peculiar star, nicknamed UJT-1, the interaction of the stellar wind withthe surrounding medium becomes extreme. Under reasonable assumptions, this unusual degree of interaction has thepotential to encode the mass-loss history of the star on timescales of several 105 years

The Planetary Accretion Shock. III. Smoothing-free 2.5D simulations and calculation
47. of H alpha emission
Gabriel-Dominique Marleau, Rolf Kuiper, William Béthune, Christoph Mordasini F Surveys have looked for H

alpha emission from accreting gas giants but found very few objects. Analyses of the detections and non-detections
have assumed that the entire gas flow feeding the planet is in radial free-fall. However, hydrodynamical simulations
suggest that this is far from reality. We calculate the H alpha emission from multidimensional accretion onto a gas
giant, following the gas flow from Hill-sphere scales down to the circumplanetary disc (CPD) and the planetary surface.
We perform azimuthally-symmetric radiation-hydrodynamics simulations around the planet and use modern tabulated
gas and dust opacities. Crucially, contrasting with most previous simulations, we do not smooth the gravitational
potential and do follow the flow down to the planetary surface, where grid cells are 0.01 Jupiter radii small radially. We
find that only roughly one percent of the net gas inflow into the Hill sphere reaches directly the planet. As expected
for ballistic infall trajectories, most of the gas falls at too large a distance on the CPD to generate H alpha. Including
radiation transport removes the high-velocity sub-surface flow previously seen in hydrodynamics-only simulations, sothat only the free planet surface and the inner regions of the CPD emit substantially H alpha. Unless magnetosphericaccretion, which we neglect here, additionally produces H alpha, the corresponding H alpha production efficiency ismuch smaller than usually assumed, which needs to be taken into account when analysing (non-)detection statistics.

Multi log-normal density structure in Cygnus-X molecular clouds: A fitting for N-PDF
48. without power-law
Takeru Murase, Toshihiro Handa, Ren Matsusaka, Yoshito Shimajiri, Masato I. N. Kobayashi, Mikito Kohno,
Junya Nishi, Norimi Takeba, Yosuke Shibata F We studied the H2 column density probability distribution func-tion (N-PDF) based on molecular emission lines using the Nobeyama 45-m Cygnus X CO survey data. Using the
DENDROGRAM and SCIMES algorithms, we identified 124 molecular clouds in the 13 CO data. From these identified
molecular clouds, an N-PDF was constructed for 11 molecular clouds with an extent of more than 0.4 deg2 . From
the fitting of the N-PDF, we found that the N-PDF could be well-fitted with one or two log-normal distributions.
These fitting results provided an alternative density structure for molecular clouds from a conventional picture. We
investigated the column density, dense molecular cloud cores, and radio continuum source distributions in each cloudand found that the N-PDF shape was less correlated with the star-forming activity over a whole cloud. Furthermore,
we found that the log-normal N-PDF parameters obtained from the fitting showed two impressive features. First, thelog-normal distribution at the low-density part had the same mean column density (∼ 1021.5 cm−2 ) for almost all
the molecular clouds. Second, the width of the log-normal distribution tended to decrease with an increasing mean

17

density of the structures. These correlations suggest that the shape of the N-PDF reflects the relationship between
the density and turbulent structure of the whole molecular cloud but is less affected by star-forming activities.

49. The star in RNO 54 – a post-FUor with short faint jet?
T. Yu. Magakian, T. A. Movsessian, H. R. Andreasyan, A. V. Moiseev, R. I. Uklein F The aim of the present

study was the spectral analysis of an unusual pre-main-sequence star in the cometary nebula RNO 54, which wassuspected by several researchers as a FUori-like object. We performed long-slit spectroscopy of the star on the 6-m
telescope with the SCORPIO-2 multi-mode focal reducer. We discover a short (∼ 4 arcsec or ∼ 6000 AU) and faintemission shock-excited jet from this star, probably oriented toward the long axis of the nebular ellipse. The spectral
type of the star is estimated as G0-2 II; the split of absorption Li I line which is a typical sign indicating the FUori-like
spectrum, is confirmed. The analysis of the available data shows virtual absence of the photometric variability, for atleast the last 20 years. The lower limit of the bolometric luminosity of the star is estimated as 300 Lsun. Our study
supports the classification of RNO 54 star as a FUor-like object in the long-after-outburst stage.

Estimation of Stellar Parameters and Mass Accretion Rate of Classical T Tauri Stars
50. from LAMOST DR6
S. Nidhi, Blesson Mathew, B. Shridharan, Suman Bhattacharyya, Edwin Das, Sreeja S Kartha F Classical T
Tauri stars are low-mass pre-main sequence stars with an active circumstellar environment. In this work we present
the identification and study of 260 Classical T Tauri stars using LAMOST Data Release 6, among which 104 stars
are newly identified. We distinguish Classical T Tauri stars from Giants and main-sequence dwarfs based on the log
g values and the presence of H (alpha) emission line and infrared excess that arises from the circumstellar accretion
disk. We estimated the mass and age of 210 stars using the Gaia color-magnitude diagram. The age is from 0.1 to
20 Myr, where 90% of the stars have age below 10 Myr and the mass ranges between 0.11 to 1.9 Msolar. From themeasured H(alpha) equivalent widths, we homogeneously estimated the mass accretion rates for 172 stars, with mostvalues ranging from 10−7 to 10−10 M(solar)/yr. The mass accretion rates are found to follow a power law distribution
with the mass of the star, having a relation of the form Macc proportional to M(star)1.43+/−0.26 , in agreement withprevious studies.

51.

Resolving the Binary Components of the Outbursting Protostar HBC 494 with ALMA
Pedro Henrique Nogueira, Alice Zurlo, Sebastián Pérez, Camilo González-Ruilova, Lucas A. Cieza, Antonio Hales, Trisha Bhowmik, Dary A. Ruíz-Rodríguez, David A. Principe, Gregory J. Herczeg, Jonathan P.
Williams, Jorge Cuadra, Matías Montesinos, Nicolás Cuello, Prachi Chavan, Simon Casassus, Zhaohuan Zhu,
Felipe G. Goicovic F Episodic accretion is a low-mass pre-main sequence phenomenon characterized by sudden out-

bursts of enhanced accretion. These objects are classified into two: protostars with elevated levels of accretion thatlasts for decades or more, called FUors, and protostars with shorter and repetitive bursts, called EXors. HBC 494
is a FUor object embedded in the Orion Molecular Cloud. Earlier Atacama Large (sub-)Millimeter Array (ALMA)
continuum observations showed an asymmetry in the disk at 0.”2 resolution. Here, we present follow-up observations at
0.”03, resolving the system into two components: HBC 494 N (primary) and HBC 494 S (secondary). No circumbinary
disk was detected. Both disks are resolved with a projected separation of 0.”18 (75 au). Their projected dimensions
are 84+/-1.8 x 66.9+/-1.5 mas for HBC 494 N and 64.6+/-2.5 x 46.0+/-1.9 mas for HBC 494 S. The disks are almostaligned and with similar inclinations. The observations show that the primary is 5 times brighter/more massive and2 times bigger than the secondary. We notice that the northern component has a similar mass to the FUors, while
the southern has to EXors. The HBC 494 disks show individual sizes that are smaller than single eruptive YSOs.
In this work, we also report 12CO, 13CO, and C18O molecular line observations. At large scale, the 12CO emission
shows bipolar outflows, while the 13CO and C18O maps show a rotating and infalling envelope around the system. At
a smaller scale, the 12CO and 13CO moment zero maps show cavities within the continuum disks’ area, which may
indicate continuum over-subtraction or slow-moving jets and chemical destruction along the line-of-sight.

52. 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. While18

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.
stnd
53. Massive pre-main-sequence stars in M17: 1 and 2 overtone CO bandhead emission
and the thermal infrared

J. Poorta, M. C. Ramírez-Tannus, A. de Koter, F. Backs, A. Derkink, A. Bik, L. Kaper F Recently muchprogress has been made in probing the embedded stages of massive star formation, pointing to formation scenarios
akin to a scaled up version of low-mass star formation. However, the latest stages of massive star formation have rarely
been observed. Using 1st and 2nd overtone CO bandhead emission and near- to mid-infrared photometry we aim tocharacterize the remnant formation disks around 5 unique pre-main-sequence (PMS) stars with masses 6 − 12 M ,that have constrained stellar parameters thanks to their detectable photospheres. We seek to understand this emission
and the disks it originates from in the context of the evolutionary stage of the studied sources. We use an analytic
LTE disk model to fit the CO bandhead and the dust emission, found to originate in different disk regions. For the
first time we modeled the 2nd overtone emission. Furthermore, we fit continuum normalized bandheads and show
the importance of this in constraining the emission region. We also include 13 CO in our models as an additional
probe of the young nature of the studied objects. We find that the CO emission originates in a narrow region close to
the star (<1 AU) and under very similar disk conditions (temperatures and densities) for the different objects. Thisis consistent with previous modeling of this emission in a diverse range of young stellar objects. We discuss theseresults in the context of the positions of these PMS stars in the Hertzsprung-Russel diagram and the CO emission’s
association with early age and high accretion rates in (massive) young stellar objects. We conclude that, considering
their mass range and for the fact that their photospheres are detected, the M17 PMS stars are observed in a relatively
early formation stage. They are therefore excellent candidates for longer wavelength studies to further constrain theend stages of massive star formation.

54.

Infall and Outflow Towards High-mass Starless Clump Candidates
T. G. S. Pillai, J. S. Urquhart, S. Leurini, Q. Zhang, A. Traficante, D. Colombo, K. Wang, L. Gomez, F.
Wyrowski F The evolutionary sequence for high-mass star formation starts with massive starless clumps that goon to form protostellar, young stellar objects and then compact HII regions. While there are many examples of thethree later stages, the very early stages have proved to be elusive. We follow-up a sample of 110 mid-infrared dark
clumps selected from the ATLASGAL catalogue with the IRAM telescope in an effort to identify a robust sample
of massive starless clumps. We have used the HCO+ (1-0) and HNC (1-0) transitions to identify clumps associatedwith infall motion and the SiO (2-1) transition to identity outflow candidates. We have found blue asymmetric line
profile in 65% of the sample, and have measured the infall velocities and mass infall rates (0.6-36 × 10−3 Msun/yr)
for 33 of these clumps. We find a trend for the mass infall rate decreasing with an increase of bolometric luminosity
to clump mass i.e. star formation within the clumps evolves. Using the SiO 2-1 line, we have identified good outflow
candidates. Combining the infall and outflow tracers reveals that 67% of quiescent clumps are already undergoinggravitational collapse or are associated with star formation; these clumps provide us with our best opportunity todetermined the initial conditions and study the earliest stages of massive star formation. Finally, we provide an
overview of a systematic high-resolution ALMA study of quiescent clumps selected that allows us to develop a detailed
understanding of earliest stages and their subsequent evolution.

55. Investigating star formation activity in the Sh 2-61 H II region

Rakesh Pandey, Saurabh Sharma, Lokesh Dewangan, Aayushi Verma, Tapas Baug, Harmeen Kaur, Arpan
Ghosh F Using the multiwavelength data sets, we studied the star formation activity in H II region Sh 2-61 (hereafter

S61). We identified a clustering in the region and estimated the membership using the Gaia proper motion data. The
physical environment of S61 is inspected using infrared to radio wavelength images. We also determined the Lyman
continuum flux associated with the H II region and found that the H II region is formed by at least two massive

19

stars (S1 and S2). We also analyzed the 12CO (J =3-2) JCMT data of S61, and a shell structure accompanying
three molecular clumps are observed towards S61. We found that the ionized gas in S61 is surrounded by dust and amolecular shell. Many young stellar objects and three molecular clumps are observed at the interface of the ionizedgas and the surrounding gas. The pressure at the interface is higher than in a typical cool molecular cloud.

56. On encounter rates in star clusters
Krisada Rawiraswattana, Simon P. Goodwin F Close encounters between stars in star forming regions are importantas they can perturb or destroy protoplanetary discs, young planetary systems, and stellar multiple systems. We
simulate simple, viralised, equal-mass N -body star clusters and find that both the rate and total number of encounters
between stars varies by factors of several in statistically identical clusters due to the stochastic/chaotic details of orbits
and stellar dynamics. Encounters tend to rapidly ‘saturate’ in the core of a cluster, with stars there each having many
encounters, while more distant stars have none. However, we find that the fraction of stars that have had at least one
encounter within a particular distance grows in the same way (scaling with crossing time and half-mass radius) in all
clusters, and we present a new (empirical) way of estimating the fraction of stars that have had at least one encounterat a particular distance.

57.

First observations of warm and cold methanol in Class 0/I proto-brown dwarfs
B. Riaz, W. -F. Thi, M. N. Machida F We present results from the first molecular line survey to search for thefundamental complex organic molecule, methanol (CH3 OH), in 14 Class 0/I proto-brown dwarfs (proto-BDs). IRAM
30-m observations over the frequency range of 92-116 GHz and 213-280 GHz have revealed emission in 14 CH3 OH
transition lines, at upper state energy level, Eupper ∼7-49 K, and critical densities, ncrit of 105 to 109 cm−3 . The mostcommonly detected lines are at Eupper < 20 K, while 11 proto-BDs also show emission in the higher excitation lines
at Eupper ∼21-49 K and ncrit ∼105 to 108 cm−3 . In comparison with the brown dwarf formation models, the highexcitation lines likely probe the warm (∼25-50 K) corino region at ∼10-50 au in the proto-BDs, while the low-excitationlines trace the cold (< 20 K) gas at ∼50-150 au. The column density for the cold component is an order of magnitude
higher than the warm component. The CH3 OH ortho-to-para ratios range between ∼0.3-2.3. The volume-averaged
CH3 OH column densities show a rise with decreasing bolometric luminosity among the proto-BDs, with the mediancolumn density higher by a factor of ∼3 compared to low-mass protostars. Emission in high-excitation (Eupper > 25K) CH3 OH lines together with the model predictions suggest that a warm corino is present in ∼78% of the proto-BDs
in our sample. The remaining show evidence of only the cold component, possibly due to the absence of a strong,high-velocity jet that can stir up the warm gas around it.

58. First ALMA maps of cosmic ray ionisation rate in high-mass star-forming regions

Giovanni Sabatini, Stefano Bovino, Elena Redaelli F Low-energy cosmic rays (< 1 TeV) are a pivotal source ofionisation of the interstellar medium, where they play a central role in determining the gas chemical composition anddrastically influence the formation of stars and planets. Over the last few decades, H+
3 absorption lines observations
ion
in diffuse clouds have provided reliable estimates of the cosmic ray ionisation rate relative to H2 (ζH). However,2
in denser clouds, where stars and planets form, this method is often inefficient due to the lack of H+
3 rotational
iontransitions. The ζHestimatesare,therefore,
still
provisionalin
thiscontext
andrepresent
one
of
the
least
understood2
components when it comes to defining general models of star and planet formation. In this Letter, we present the firstionhigh-resolution maps of the ζHin two high-mass clumps obtained with a new analytical approach recently proposed
2
ion
ion
to estimate the ζH2 in the densest regions of molecular clouds. We obtain hζHi that span from 3 × 10−17 to 10−16 s−1 ,2depending on the different distribution of the main ion carriers, in excellent agreement with the most recent cosmic
ionrays propagation models. The cores belonging to the same parental clump show comparable ζH, suggesting that the2ionisation properties of prestellar regions are determined by global rather than local effects. These results provide
important information for the chemical and physical modelling of star-forming regions.

59. The Effelsberg survey of FU Orionis and EX Lupi objects II. – H2 O maser observations
Zs. M. Szabó, Y. Gong, W. Yang, K. M. Menten, O. S. Bayandina, C. J. Cyganowski, Á. Kóspál, P. Ábrahám,
A. Belloche, F. Wyrowski F FU Orionis (FUor) and EX Lupi (EXor) type objects are two groups of peculiar and rarepre-main sequence low-mass stars that are undergoing powerful accretion outbursts during their early stellar evolution.

20

Water masers are widespread in star forming regions and are powerful probes of mass accretion and ejection, but little
is known about the prevalence of them toward FUors/EXors. We perform the first systematic search for the 22.2
GHz water maser line in FUors/EXors to determine its overall incidence to perform follow-up high angular resolution
observations. We used the Effelsberg 100-m radio telescope to observe the 22.2 GHz H2O maser toward a sample of 51
objects. We detect 5 water masers; 3 are associated with eruptive stars, resulting in a 6% detection rate for eruptive
sources. These detections include one EXor, V512 Per (also known as SVS 13 or SVS 13A), and two FUors, Z CMa andHH 354 IRS. This is the first reported detection of water maser emission towards HH 354 IRS. We detect water maser
emission in our pointing towards the FUor binary RNO 1B/1C, which most likely originates from the nearby deeply
embedded source IRAS 00338+6312 ( 4”, from RNO 1B/1C). Emission was also detected from H2 O(B) (also known
as SVS 13C), a Class 0 source 30”, from the EXor V512 Per. The peak flux density of H2 O(B) in our observations,498.7 Jy, is the highest observed to date. In addition to the two non-eruptive Class 0 sources (IRAS 00338+6312 andH2 O(B) /SVS 13C), we detect maser emission towards one Class 0/I (HH 354 IRS) and two Class I (V512 Per and ZCMa) eruptive stars. We demonstrate the presence of 22.2 GHz water maser emission in FUor/EXor systems, opening
the way to radio interferometric observations to study these eruptive stars on small scales. Comparing our data withhistorical observations suggest that multiple water maser flares have occurred in both V512 Per and H2 O(B).

The edge-on protoplanetary disk HH 48 NE I. Modeling the geometry and stellar pa60. rameters
J. A. Sturm, M. K. McClure, C. J. Law, D. Harsono, J. B. Bergner, E. Dartois, M. N. Drozdovskaya, S.
Ioppolo, K. I. Öberg, M. E. Palumbo, Y. J. Pendleton, W. R. M. Rocha, H. Terada, R. G. Urso F Context.

Observations of edge-on disks are an important tool for constraining general protoplanetary disk properties that cannot be determined in any other way. However, most radiative transfer models cannot simultaneously reproduce thespectral energy distributions (SEDs) and resolved scattered light and submillimeter observations of these systems, due
to the differences in geometry and dust properties at different wavelengths. Aims. We simultaneously constrain thegeometry of the edge-on protoplanetary disk HH 48 NE and the characteristics of the host star. HH 48 NE is part of
the JWST early release science program Ice Age. This work serves as a stepping stone towards a better understandingof the disk physical structure and icy chemistry in this particular source. This kind of modeling lays the groundworkfor studying other edge-on sources to be observed with the JWST. Methods. We fit a parameterized dust model to HH
48 NE by coupling the radiative transfer code RADMC-3D and an MCMC framework. The dust structure was fitted
independently to a compiled SED, a scattered light image at 0.8 µm and an ALMA dust continuum observation at
890 µm. Results. We find that 90% of the dust mass in HH 48 NE is settled to the disk midplane, less than in averagedisks, and that the atmospheric layers of the disk contain exclusively large grains (0.3-10 µm). The exclusion of small
grains in the upper atmosphere likely has important consequences for the chemistry due to the deep penetration ofhigh-energy photons. The addition of a relatively large cavity (ca. 50 au in radius) is necessary to explain the strong
mid-infrared emission, and to fit the scattered light and continuum observations simultaneously.

61. The edge-on protoplanetary disk HH 48 NE II. Modeling ices and silicates
J. A. Sturm, M. K. McClure, J. B. Bergner, D. Harsono, E. Dartois, M. N. Drozdovskaya, S. Ioppolo, K.
I. Öberg, C. J. Law, M. E. Palumbo, Y. J. Pendleton, W. R. M. Rocha, H. Terada, R. G. Urso F The

abundance and distribution of ice in protoplanetary disks (PPD) is critical to understand the linkage between thecomposition of circumstellar matter and the composition of exoplanets. Edge-on PPDs are a useful tool to constrain
such ice composition and its location in the disk, as ice spectral signatures can be observed in absorption against thecontinuum emission arising from the warmer central disk regions. The aim of this work is to model ice absorption
features in PPDs and determine how well the abundance of the main ice species across the disk can be determinedwithin the uncertainty of the physical parameter space. The edge-on PPD around HH 48 NE, a target of the JWSTERS program IceAge, is used as a reference system. We use RADMC-3D to raytrace the mid-infrared continuum.
Using a constant parameterized ice abundance, ice opacities are added to the dust opacity in regions wherever the disk
is cold enough for the main carbon, oxygen and nitrogen carriers to freeze out. The global abundance of the main ice
carriers in HH 48 NE can be determined within a factor of 3, when taking the uncertainty of the physical parameters
into account. Ice features in PPDs can be saturated at an optical depth <1, due to local saturation. Spatiallyobserved ice optical depths cannot be directly related to column densities due to radiative transfer effects. Verticalsnowlines will not be a clear transition due to the radially increasing height of the snowsurface, but their location may
be constrained from observations using radiative transfer modeling. Radial snowlines are not really accesible. Not
21

only the ice abundance, but also inclination, settling, grain size distribution and disk mass have strong impact on theobserved ice absorption features in disks. Relative changes in ice abundance can be inferred from observations only if
the source structure is well constrained

62. NGTS clusters survey − V: Rotation in the Orion Star-forming Complex
Gareth D. Smith, Edward Gillen, Simon T. Hodgkin, Douglas R. Alves, David R. Anderson, Matthew P.
Battley, Matthew R. Burleigh, Sarah L. Casewell, Samuel Gill, Michael R. Goad, Beth A. Henderson, James
S. Jenkins, Alicia Kendall, Maximiliano Moyano, Gavin Ramsay, Rosanna H. Tilbrook, Jose I. Vines, Richard
G. West, Peter J. Wheatley F We present a study of rotation across 30 square degrees of the Orion Star-forming

Complex, following a ∼200 d photometric monitoring campaign by the Next Generation Transit Survey (NGTS).
From 5749 light curves of Orion members, we report periodic signatures for 2268 objects and analyse rotation period
distributions as a function of colour for 1789 stars with spectral types F0−M5. We select candidate members ofOrion using Gaia data and assign our targets to kinematic sub-groups. We correct for interstellar extinction on astar-by-star basis and determine stellar and cluster ages using magnetic and non-magnetic stellar evolutionary models.
Rotation periods generally lie in the range 1−10 d, with only 1.5 per cent of classical T Tauri stars or Class I/II
young stellar objects rotating with periods shorter than 1.8 d, compared with 14 per cent of weak-line T Tauri stars
or Class III objects. In period−colour space, the rotation period distribution moves towards shorter periods among
low-mass (>M2) stars of age 3−6 Myr, compared with those at 1−3 Myr, with no periods longer than 10 d for stars
later than M3.5. This could reflect a mass-dependence for the dispersal of circumstellar discs. Finally, we suggest thatthe turnover (from increasing to decreasing periods) in the period−colour distributions may occur at lower mass forthe older-aged population: ∼K5 spectral type at 1−3 Myr shifting to ∼M1 at 3−6 Myr.

63. A panoptic view of the Taurus molecular cloud I. The cloud dynamics revealed by gas
emission and 3D dust
J. D. Soler, C. Zucker, J. E. G. Peek, M. Heyer, P. F. Goldsmith, S. C. O. Glover, S. Molinari, R. S. Klessen,
P. Hennebelle, L. Testi, T. Colman, M. Benedettini, D. Elia, C. Mininni, S. Pezzuto, E. Schisano, A. Traficante

F We present a study of the three-dimensional (3D) distribution of interstellar dust derived from stellar extinction
observations toward the Taurus molecular cloud (MC) and its relation with the neutral atomic hydrogen (HI) emission
at 21 cm wavelength and the carbon monoxide 12 CO and 13 CO emission in the J = 1 → 0 transition. We used
the histogram of oriented gradients (HOG) method to match the morphology in a 3D reconstruction of the dust
density (3D dust) and the distribution of the gas tracers’ emission. The result of the HOG analysis is a map of
the relationship between the distances and radial velocities. The HOG comparison between the 3D dust and the HI
emission indicates a morphological match at the distance of Taurus but an anti-correlation between the dust density
and the HI emission, which uncovers a significant amount of cold HI within the Taurus MC. The HOG between the
3D dust and 12 CO reveals a pattern in radial velocities and distances that is consistent with converging motions of
the gas in the Taurus MC, with the near side of the cloud moving at higher velocities and the far side moving at lower
velocities. This convergence of flows is likely triggered by the large-scale gas compression caused by the interaction of
the Local Bubble and the Per-Tau shell, with Taurus lying at the intersection of the two bubble surfaces.

64. Formation of the warped debris disc around β Pictoris

Jeremy L. Smallwood F In light of the recent confirmation of an eccentric orbit giant planet, β Pic c, I revisit theformation and evolution of the warped debris disc in the system. β Pic c is interior to β Pic b, and the debris discis exterior to both planets. Previous N -body simulations have shown that β Pic b is responsible for exciting theinclination of the debris disc. With hydrodynamical simulations, I model a protoplanetary gas disc misaligned withthe planets. I find that the gas disc does not exhibit significant long lasting inclination excitation from the planets
even for the observed disc size. The warp that is excited by the planets propagates through the entire disc with atimescale much less than the gas disc lifetime. Therefore, the observed warp in the debris disc must be produced after
the gas disc has dispersed. With analytical secular theory calculations, I show that two secular resonances are exterior
to β Pic b, located at ∼ 20 au and ∼ 25 au. This agrees with my N -body simulations that show that these secularresonances shape the inner edge of the β Pic debris disc at a radius that agrees with observations.

22

A rich hydrocarbon chemistry and high C to O ratio in the inner disk around a very
65. low-mass star
B. Tabone, G. Bettoni, E. F. van Dishoeck, A. M. Arabhavi, S. L. Grant, D. Gasman, T. Henning, I. Kamp,
M. Güdel, P. -O. Lagage, T. P. Ray, B. Vandenbussche, A. Abergel, O. Absil, I. Argyriou, D. Barrado, A.
Boccaletti, J. Bouwman, A. Caratti o Garatti, V. Geers, A. M. Glauser, K. Justannont, F. Lahuis, M. Mueller,
C. Nehmé, G. Olofsson, E. Pantin, S. Scheithauer, C. Waelkens, L. B. F. M. Waters, J. H. Black, V. Christiaens,
R. Guadarrama, M. Morales-Calderón, H. Jang, J. Kanwar, N. Pawellek, G. Perotti, A. Perrin, D. RodgersLee, M. Samland, J. Schreiber, K. R. Schwarz, L. Colina, G. Östlin, G. Wright F Carbon is an essential element

for life but how much can be delivered to young planets is still an open question. The chemical characterizationof planet-forming disks is a crucial step in our understanding of the diversity and habitability of exoplanets. Very
low-mass stars (< 0.2 M ) are interesting targets because they host a rich population of terrestrial planets. Here we
present the JWST detection of abundant hydrocarbons in the disk of a very low-mass star obtained as part of the
MIRI mid-INfrared Disk Survey (MINDS). In addition to very strong and broad emission from C2 H2 and its 13 C12 CH2isotopologue, C4 H2 , benzene, and possibly CH4 are identified, but water, PAH and silicate features are weak or absent.
The lack of small silicate grains implies that we can look deep down into this disk. These detections testify to an active
warm hydrocarbon chemistry with a high C/O ratio in the inner 0.1 au of this disk, perhaps due to destruction ofcarbonaceous grains. The exceptionally high C2 H2 /CO2 and C2 H2 /H2 O column density ratios suggest that oxygen islocked up in icy pebbles and planetesimals outside the water iceline. This, in turn, will have significant consequences
for the composition of forming exoplanets.

66. Chemical Differentiation around Five Massive Protostars Revealed by ALMA -CarbonChain Species, Oxygen-/Nitrogen-Bearing Complex Organic MoleculesKotomi Taniguchi, Liton Majumdar, Paola Caselli, Shigehisa Takakuwa, Tien-Hao Hsieh, Masao Saito, Zhi-Yun
Li, Kazuhito Dobashi, Tomomi Shimoikura, Fumitaka Nakamura, Jonathan C. Tan, Eric Herbst F We present

Atacama Large Millimeter/submillimeter Array Band 3 data toward five massive young stellar objects (MYSOs), andinvestigate relationships between unsaturated carbon-chain species and saturated complex organic molecules (COMs).
An HC5 N (J = 35 − 34) line has been detected from three MYSOs, where nitrogen(N)-bearing COMs (CH2 CHCN
and CH3 CH2 CN) have been detected. The HC5 N spatial distributions show compact features and match with amethanol (CH3 OH) line with an upper-state energy around 300 K, which should trace hot cores. The hot regions are
more extended around the MYSOs where N-bearing COMs and HC5 N have been detected compared to two MYSOs
without these molecular lines, while there are no clear differences in the bolometric luminosity and temperature. We
run chemical simulations of hot-core models with a warm-up stage, and compare with the observational results. The
observed abundances of HC5 N and COMs show good agreements with the model at the hot-core stage with temperatures above 160 K. These results indicate that carbon-chain chemistry around the MYSOs cannot be reproduced bywarm carbon-chain chemistry, and a new type of carbon-chain chemistry occurs in hot regions around MYSOs.

67. Probing the Temperature Structure of the Inner Region of a Protoplanetary Disk

Takahiro Ueda, Satoshi Okuzumi, Akimasa Kataoka, Mario Flock F Midplane heating induced by disk accretion

plays a key role in determining the disk temperature particularly at the inner disk midplane where planets form. However, the efficiency of accretion heating has been not well constrained by observations. We construct two-dimensionalmodels of the Class II disk around CW Tau, taking into account the midplane heating. The models are comparedwith the ALMA dust continuum observations at Bands 4, 6, 7 and 8, with an angular resolution of 0.1 arcsec. The
observed brightness temperatures are almost wavelength-indenpendent at .10 au. We find that if the maximum dust
size amax is . 100 µm, the brightness temperatures predicted by the model exceed the observed values, regardless ofthe efficiency of accretion heating. The low observed brightness temperatures can be explained if millimeter scattering
reduces the intensity. If the disk is passive, amax needs to be either ∼ 150 µm or & few cm. The accretion heating
significantly increases the brightness temperature particularly when amax . 300 µm, and hence amax needs to beeither ∼ 300 µm or & few cm. The midplane temperature is expected to be ∼1.5-3 times higher than the observedbrightness temperatures, depending on the models. The dust settling effectively increases the temperature of the dust
responsible for the millimeter emission in the active disk, which makes the model with 300 µm-sized dust overpredicts
the brightness temperatures when strong turbulence is absent. Porous dust (porosity of 0.9) makes the accretion
heating more efficient so that some sort of reduction in accretion heating is required. Future longer wavelength andhigher angular resolution observations will help us constrain the heating mechanisms of the inner protoplanetary disks.
2368. Variability of Young Stellar Objects in the Perseus Molecular Cloud
Xiao-Long Wang, Min Fang, Gregory J. Herczeg, Yu Gao, Hai-Jun Tian, Xing-Yu Zhou, Hong-Xin Zhang,
Xue-Peng Chen F We present an analysis of 288 young stellar objects (YSOs) in the Perseus Molecular Cloudthat have well defined g and r-band lightcurves from the Zwicky Transient Facility. Of the 288 YSOs, 238 sources(83% of our working sample) are identified as variables based on the normalized peak-to-peak variability metric, withvariability fraction of 92% for stars with disks and 77% for the diskless populations. These variables are classified
into different categories using the quasiperiodicity (Q) and flux asymmetry (M ) metrics. Fifty-three variables areclassified as strictly periodic objects that are well phased and can be attributed to spot modulated stellar rotation.
We also identify 22 bursters and 25 dippers, which can be attributed to accretion burst and variable extinction,
respectively. YSOs with disks tend to have asymmetric and non-repeatable lightcurves, while the YSOs without disks
tend to have (quasi)periodic lightcurves. The periodic variables have the steepest change in g versus g − r, whilebursters have much flatter changes than dippers in g versus g − r. Periodic and quasiperiodic variables display thelowest variability amplitude. Simple models suggest that the variability amplitudes of periodic variables correspondto changes of the spot coverage of 30% to 40%, burster variables are attributed to accretion luminosity changes in therange of Lacc /L? = 0.1 − 0.3, and dippers are due to variable extinction with AV changes in the range of 0.5 − 1.3 mag.

High energy gamma-ray emission powered by a young protostar:
69. the case of S255 NIRS 3
Emma de Oña Wilhelmi, Rubén López-Coto, Yang Su F Evidence of efficient acceleration of cosmic rays in massive

young stellar objects has been recently reported. Among these massive protostars, S255 NIRS 3 for which extreme
flaring events associated with radio jets have been detected, is one of the best objects to test this hypothesis. We
search for gamma-ray emission associated with this object in Fermi-LAT data and inspect the gas content in different
molecular lines using the MWISP survey. A GeV source dubbed 4FGL J0613.1+1749c lies on top of the MYSO
region, where two filamentary 10 pc CO structures extend along the same direction of the sub-parsec radio jets. We
investigate the spectrum, morphology, and light curve of the gamma-ray source and compare it with the theoreticalemission expected from hadronic and leptonic populations accelerated in the radio jets. We argue that the gamma-ray
source could be powered by particles accelerated in the S255 NIRS 3 jets, radiating via Bremsstrahlung or protonproton interaction, and with a synchrotron component shinning in radio from primary or secondary electrons in thecase of a leptonic or hadronic population.

70.

Distinguishing Magnetized Disc Winds from Turbulent Viscosity through Substructure
Morphology in Planet-forming Discs
Yinhao Wu, Yi-Xian Chen, Haochang Jiang, Ruobing Dong, Enrique Macías, Min-Kai Lin, Giovanni P. Rosotti,
Vardan Elbakyan F The traditional paradigm of viscosity-dominated evolution of protoplanetary discs has been

recently challenged by magnetized disc winds. However, distinguishing wind-driven and turbulence-driven accretion
through observations has been difficult. In this study, we present a novel approach to identifying their separate
contribution to angular momentum transport by studying the gap and ring morphology of planet-forming discs in the
ALMA continuum. We model the gap-opening process of planets in discs with both viscous evolution and wind-driven
accretion by 2D multi-fluid hydrodynamical simulations. Our results show that gap-opening planets in wind-driven
accreting discs generate characteristic substructures that differ from those in purely viscous discs. Specifically, wedemonstrate that discs, where wind-driven accretion dominates the production of substructures, exhibit significant
asymmetries. Based on the diverse outputs of mock images in the ALMA continuum, we roughly divide the planetinduced features into four regimes (moderate-viscosity dominated, moderate-wind dominated, strong-wind dominated,inviscid). The classification of these regimes sets up a potential method to constrain the strength of magnetized discwind and viscosity based on the observed gap and ring morphology. We discuss the asymmetry feature in our mock
images and its potential manifestation in ALMA observations.

71. Star-forming environments in smoothed particle magnetohydrodynamics simulations I:
Clump extraction and properties
James Wurster, Connar Rowan F What is the nature of a star forming clump? Observations reveal these to bechaotic environments being modified and influenced by many physical processes. However, numerical simulations often
define these initial star forming clumps to be idealised objects. In this paper, we define and analyse 109 star forming

24

clumps extracted from our previous low-mass star cluster simulations. To define a clump, we identify all the gas in asimulation that ever becomes bound to or accreted onto a star, then follow the gas backwards in time until it decreases
to a critical density. This gas, and its neighbouring gas, is defined as our star forming clump. Our clumps span amass range of 0.15 . M/M . 10.2, while the density range within each clump spans 2–4 orders of magnitude. The
gas density distribution is not smooth, indicating that it is highly structured. The clumps are turbulent, with nocoherent rotation. Independent of the initial magnetic field strength of the parent cloud, all clumps yield a similar
range of field strengths. The clump magnetic field is ordered, but not reflective of the initial field geometry of theparent cloud. In general, most clump properties have a slight trend with clump mass but are independent of (or only
very weakly dependent on) the properties of the parent cloud. We conclude that stars are born from a wide variety ofenvironments and there is not a single universal star forming clump.

72. ATLASGAL: 3-mm class I methanol masers in high-mass star formation regions
W. Yang, Y. Gong, K. M. Menten, J. S. Urquhart, C. Henkel, F. Wyrowski, T. Csengeri, S. P. Ellingsen, A.
R. Bemis, J. Jang F We analyzed the 3-mm wavelength spectral line survey of 408 ATLASGAL clumps observedwith the IRAM 30m-telescope, focusing on the class I methanol masers with frequencies near 84, 95 and 104.3 GHz.
We detect narrow, maser-like features towards 54, 100 and 4 sources in the maser lines near 84, 95 and 104.3 GHz,
respectively. Among them, fifty 84 GHz masers, twenty nine 95 GHz masers and four rare 104.3 GHz masers are new
discoveries. The new detections increase the number of known 104.3 GHz masers from 5 to 9. The 95 GHz class I
methanol maser is generally stronger than the 84 GHz maser counterpart. We find 9 sources showing class I methanol
masers but no SiO emission, indicating that class I methanol masers might be the only signpost of protostellar outflow
activity in extremely embedded objects at the earliest evolutionary stage. Class I methanol masers that are associatedwith sources that show SiO line wings are more numerous and stronger than those without such wings. The total
integrated intensity of class I methanol masers is well correlated with the integrated intensity and velocity coverageof the SiO (2–1) emission. The properties of class I methanol masers are positively correlated with the bolometricluminosity, clump mass, peak H2 column density of their associated clumps but uncorrelated with the luminosityto-mass ratio, dust temperature, and mean H2 volume density. We suggest that the properties of class I masers are
related to shocks traced by SiO. Based on our observations, we conclude that class I methanol masers at 84 and 95
GHz can trace a similar evolutionary stage as H2 O maser, and appear prior to 6.7 and 12.2 GHz methanol and OH
masers. Despite their small number, the 104.3 GHz class I masers appear to trace a short and more evolved stage
compared to the other class I masers. [abridged]

73.

Observations of planet forming disks in multiple stellar systems
Alice Zurlo, Raffaele Gratton, Sebastián Pérez, Lucas Cieza F The demographic of circumstellar disks, thebirthplaces of planets, is diverse and rich in disks featuring rings, gaps, spirals, filaments, and arcs. Many studies
revealing these disk structures have focused on objects around single stars and disks in isolation. The scenario is more
complex if binarity or multiplicity is involved; most stars are part of multiple systems in crowded star-forming regions.
How does the presence of one or more stellar companions affect the shape and size of the circumstellar disks? Here we
review the landscape of results from optical, infrared, and (sub-) millimeter observations of the effects of multiplicity
on protoplanetary disks, emphasizing the demographic studies of nearby molecular clouds and the high-resolution
studies of multiple disk systems.

74. Substructures in Compact Disks of the Taurus Star-forming Region

Shangjia Zhang, Matt Kalscheur, Feng Long, Ke Zhang, Deryl E. Long, Edwin A. Bergin, Zhaohuan Zhu, Leon
Trapman F Observations of substructure in protoplanetary disks have largely been limited to the brightest and largest

disks, excluding the abundant population of compact disks which are likely sites of planet formation. Here, we reanalyze0.1”, 1.33 mm ALMA continuum observations of 12 compact protoplanetary disks in the Taurus star-forming region. By
fitting visibilities directly, we identify substructures in 6 of the 12 compact disks. We then compare the substructures
identified in the full Taurus sample of 24 disks in single star systems and the ALMA DSHARP survey, differentiating
between compact (Ref f ,90% < 50 au) and extended (Ref f ,90% > 50 au) disk sources. We find that substructures aredetected at nearly all radii in both small and large disks. Tentatively, we find fewer wide gaps in intermediate-sizeddisks with Ref f ,90% between 30 and 90 au. We perform a series of planet-disk interaction simulations to constrain thesensitivity of our visibility-fitting approach. Under an assumption of planet-disk interaction, we use the gap widths

25and common disk parameters to calculate potential planet masses within the Taurus sample. We find that the youngplanet occurrence rate peaks near Neptune masses, similar to the DSHARP sample. For 0.01 MJ /M . Mp /M∗ . 0.1
MJ /M , the rate is 17.4±8.3%; for 0.1 MJ /M . Mp /M∗ . 1 MJ /M , it is 27.8±8.3%. Both of them are consistent
with microlensing surveys. For gas giants more massive than 5 MJ , the occurrence rate is 4.2±4.2%, consistent withdirect imaging surveys.

26