The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 347 — 19 November 2021
Editor: João Alveswww.starformation.news

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Cover image caption
ALMA image of the PDS 70 system (resolution 20 mas, 2.3 au), located in the Sco-Cen association. The system features
a star at its centre and at least two planets orbiting it, PDS 70b (not visible in the image) and PDS 70c, surrounded by acircumplanetary disc (the dot to the right of the star). The planets have carved a cavity in the circumstellar disk. Credit
Benisty et al.
Note from the Editor
The Star Formation Newsletter is now on the web at www.starformation.news. This PDF file contains the monthly Abstracts
and links to the different Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to the SFN is as simple
as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site. Do not remove the LATEX formatting
when submitting to the arXiv. If you do, your abstract will not look great either at the arXiv or the SFN.

Abstracts
1. θ1 Ori C as a medieval bully: a possible very recent ejection in the Trapezium
J. Maíz Apellániz, M. Pantaleoni González, R. H. Barbá F We use Gaia EDR3 astrometry to propose that a dynamicalinteraction between the multiple system θ1 Ori C and θ1 Ori F ejected the latter as a walkaway star 1100 years ago (without
deceleration) or somewhat later (with a more likely deceleration included). It is unclear whether the final 3-D velocity of θ1 Ori
F will be large enough to escape the Orion nebula cluster.

2. Investigating variations in the dust emissivity index in the Andromeda galaxy

G. Athikkat-Eknath, S. A. Eales, M. W. L. Smith, A. Schruba, K. A. Marsh, A. P. Whitworth F Over the
past decade, studies of dust in the Andromeda galaxy (M31) have shown radial variations in the dust emissivity index (β).
Understanding the astrophysical reasons behind these radial variations may give clues about the chemical composition of dust
grains, their physical structure, and the evolution of dust. We use 12 CO(J=1-0) observations taken by the Combined Array for
Research in Millimeter Astronomy (CARMA) and dust maps derived from Herschel images, both with an angular resolution of8" and spatial resolution of 30 pc, to study variations in β across an area of ≈ 18.6 kpc2 in M31. We extract sources, which we
identify as molecular clouds, by applying the astrodendro algorithm to the 12 CO and dust maps, which as a byproduct allows us
to compare continuum emission from dust and CO emission as alternative ways of finding molecular clouds. We then use thesecatalogues to investigate whether there is evidence that β is different inside and outside molecular clouds. Our results confirm
the radial variations of β seen in previous studies. However, we find little difference between the average β inside molecular
clouds compared to outside molecular clouds, in disagreement with models which predict an increase of β in dense environments.
Finally, we find some clouds traced by dust with very little CO which may be either clouds dominated by atomic gas or cloudsof molecular gas that contain little CO.

3. Supersonic Expansion of the Bipolar Hii Region Sh2-106: A 3,500 Year-Old Explosion?

John Bally, Zen Chia, Adam Ginsburg, Bo Reipurth, Kei E. I. Tanaka, Hans Zinnecker, John Faulhaber F
Multi-epoch narrow-band HST images of the bipolar Hii region Sh2-106 reveal highly supersonic nebular proper motions which
increase with projected distance from the massive young stellar object S106 IR, reaching over 30 mas/year ( 150 km/s at
D=1.09 kpc) at a projected separation of 1.4’ (0.44 pc) from S106 IR. We propose that S106 IR experienced a ∼ 1047 erg
explosion 3,500 years ago. The explosion may be the result of a major accretion burst, a recent encounter with another star, ora consequence of the interaction of a companion with the bloated photosphere of S106 IR as it grew from 10 through 15 Solar
masses at a high accretion rate. Near-IR images reveal fingers of molecular hydrogen emission pointing away from S106 IR

2

and an asymmetric photon-dominated region surrounding the ionized nebula. Radio continuum and Brackett-gamma emission
reveal a C-shaped bend in the plasma, either indicating motion of S106 IR toward the east, or deflection of plasma toward thewest by the surrounding cloud. The Hii region bends around a 1’ diameter dark bay west of S106 IR that may be shielded fromdirect illumination by a dense molecular clump. Herbig-Haro (HH) and Molecular Hydrogen Objects (MHOs) tracing outflows
powered by stars in the Sh2-106 proto-cluster such as the Class 0 source S106 FIR are discussed.

4. Kinematics and Structure of Ionized Gas in the UCHII Regions of W33 Main

Dan Beilis, Sara Beck, John Lacy F High mass proto-stars create Ultra-Compact Hii regions (UCHII) at the stage ofevolution when most of the accretion is finished but the star is still heavily embedded in molecular material. The morphologies
of UCHII regions reflect the interactions of stellar winds, stellar motions, and density structure in the molecular cloud; they arecomplex and it has been very difficult to interpret them. We here present data obtained with TEXES on the NASA IRTF of the[NeII] emission line in the proto-cluster of young OB stars in W33 Main. The data cube has a spatial resolution of 1.4 arcsec
and true velocity resolution 5 km/s; with A 0.02Av it is relatively unaffected by extinction. We have run 3D hydrodynamic
and line profile simulations, using PLUTO and RADMC-3D, of the gas structures created by multiple windy stars moving
relative to each other through the ambient cloud. By iterative comparison of the data cube and the simulations, we arrive
at models that reproduce the different morphology and kinematic structure of each UCHII region in W33 Main. The results
indicate that each sub-source probably holds multiple exciting stars, permitting an improved view of the stellar population, andfinds the stellar trajectories, which may determine the dynamical development of the proto-cluster.

Robustness of Synthetic Observations in Producing Observed Core Properties: Predic-

5. tions for the TolTEC Clouds to Cores Legacy Survey

S. K. Betti, R. Gutermuth, S. Offner, G. Wilson, A. Sokol, R. Pokhrel F We use hydrodynamical simulations ofstar-forming gas with stellar feedback and sink particles (proxies for young stellar objects, i.e., YSOs) to produce and analyze
synthetic 1.1mm continuum observations at different distances (150 - 1000pc) and ages (0.49 - 1.27 Myr). We characterize
how the inferred core properties, including mass, size, and clustering with respect to diffuse natal gas structure, change with
distance, cloud evolution, and the presence of YSOs. We find that atmospheric filtering and core segmentation treatments
have distance-dependent impacts on the resulting core properties for d < 300pc and 500pc, respectively, which dominate overevolutionary differences. Concentrating on synthetic observations at further distances (650-1000pc), we find a growing separation between the inferred sizes and masses of cores with and without YSOs in the simulations, which is not seen in recent
observations of the Mon R2 cloud at 860pc. We find that the synthetic cores cluster in smaller groups, and their mass densities
are correlated with gas column density over a much narrower range, than the Mon R2 observations. Such differences limit
applicability of the evolutionary predictions we report here and motivate future efforts to adapt our synthetic observation andanalysis framework to next generation simulations such as STARFORGE. These predictions and systematic characterizations
will help guide analysis of cores for the upcoming TolTEC Clouds to Cores Legacy Survey on the Large Millimeter Telescope
Alfonso Serrano (LMT).

Per-Tau Shell: A Giant Star-Forming Spherical Shell Revealed by 3D Dust Obser6. The
vations
Shmuel Bialy, Catherine Zucker, Alyssa Goodman, Michael M. Foley, João Alves, Vadim A. Semenov, Robert
Benjamin, Reimar Leike, Torsten Enßlin F A major question in the field of star formation is how molecular clouds formout of the diffuse Interstellar Medium (ISM). Recent advances in 3D dust mapping are revolutionizing our view of the structureof the ISM. Using the highest-resolution 3D dust map to date, we explore the structure of a nearby star-forming region, which
includes the well-known Perseus and Taurus molecular clouds. We reveal an extended near-spherical shell, 156 pc in diameter,
hereafter the "Per-Tau Shell", in which the Perseus and Taurus clouds are embedded. We also find a large ring structure at
the location of Taurus, hereafter, the "Tau Ring". We discuss a formation scenario for the Per-Tau Shell, in which previous
stellar and supernova (SN) feedback events formed a large expanding shell, where the swept-up ISM has condensed to form
both the shell and the Perseus and Taurus molecular clouds within it. We present auxiliary observations of HI, Hα, 26 Al, and
X-rays that further support this scenario, and estimate Per-Tau Shell’s age to be ≈ 6 − 22 Myrs. The Per-Tau shell offers thefirst three-dimensional observational view of a phenomenon long-hypothesized theoretically, molecular cloud formation and starformation triggered by previous stellar and SN feedback.

37. The SEDIGISM survey: The influence of spiral arms on the molecular gas distributionof the inner Milky Way

D. Colombo, A. Duarte-Cabral, A. R. Pettitt, J. S. Urquhart, F. Wyrowski, T. Csengeri, K. R. Neralwar, F.
Schuller, K. M. Menten, L. Anderson, P. Barnes, H. Beuther, L. Bronfman, D. Eden, A. Ginsburg, T. Henning,
C. Koenig, M. -Y. Lee, M. Mattern, S. Medina, S. E. Ragan, A. J. Rigby, A. Sanchez-Monge, A. Traficante, A.
Y. Yang, M. Wienen F The morphology of the Milky Way is still a matter of debate. In order to shed light on uncertainties
surrounding the structure of the Galaxy, in this paper, we study the imprint of spiral arms on the distribution and properties of
its molecular gas. To do so, we take full advantage of the SEDIGISM survey that observed a large area of the inner Galaxy inthe 13 CO(2-1) line at an angular resolution of 28". We analyse the influences of the spiral arms by considering the features ofthe molecular gas emission as a whole across the longitude-velocity map built from the full survey. Additionally, we examine theproperties of the molecular clouds in the spiral arms compared to the properties of their counterparts in the inter-arm regions.
Through flux and luminosity probability distribution functions, we find that the molecular gas emission associated with thespiral arms does not differ significantly from the emission between the arms. On average, spiral arms show masses per unit
length of ∼ 105 − 106 M kpc−1 . This is similar to values inferred from data sets in which emission distributions were segmented
into molecular clouds. By examining the cloud distribution across the Galactic plane, we infer that the molecular mass in the
spiral arms is a factor of 1.5 higher than that of the inter-arm medium, similar to what is found for other spiral galaxies in thelocal Universe. We observe that only the distributions of cloud mass surface densities and aspect ratio in the spiral arms show
significant differences compared to those of the inter-arm medium; other observed differences appear instead to be driven by adistance bias. By comparing our results with simulations and observations of nearby galaxies, we conclude that the measured
quantities would classify the Milky Way as a flocculent spiral galaxy, rather than as a grand-design one.

and outflows in the early phases of massive star formation: influence of magnetic
8. Discs
fields and ambipolar diffusionBenoît Commerçon, Matthias González, Raphaël Mignon-Risse, Patrick Hennebelle, Neil Vaytet F We study
mass accretion and ejection in the vicinity of massive star forming cores using high-resolution (5 au) 3D AMR numericalsimulations. We investigate the mechanisms at the origin of outflows and characterise the properties of the disc forming aroundmassive protostars. We include both protostellar radiative feedback via PMS evolutionary tracks and magnetic ambipolar
diffusion. We studied 3 different cases: purely hydrodynamical, ideal MHD, and ambipolar diffusion. In the resistive models, weinvestigate the effects the initial amplitude of both magnetic field and rotation have on the properties of the massive protostellar
system. We use simple criteria to identify the outflow and disc material and follow their evolution as the central star accretes
mass up to 20 solar mass. The outflow is completely different when magnetic fields are introduced, so that magnetic processes
are the main driver of the outflow up to stellar masses of 20 solar mass. The disc properties depend on the physics included.
The disc formed in the ideal and resistive runs show opposite properties in terms of plasma beta and of magnetic fields topology.
While the disc in the ideal case is dominated by the magnetic pressure and the toroidal magnetic fields, the one formed in theresistive runs is dominated by the thermal pressure and has essentially vertical magnetic fields in the inner regions (R<200au). We find that magnetic processes dominate the early evolution of massive protostellar systems (<20 solar mass) and shapes
the accretion/ejection as well as the disc formation. Ambipolar diffusion is mainly at work at disc scales and regulates its
properties. Our finding for the outflow and disc properties are reminiscent of low-mass star formation, suggesting that accretionand ejection in young massive and low-mass protostars are regulated by the same physical processes at the early stages.

Gas dynamics in the star forming region G18.148−0.283: Is it a manifestation of two

9. colliding molecular clouds?

Jyotirmoy Dey, Jagadheep D. Pandian, Dharam Vir Lal F We report the results obtained from a multi-wavelength studyof the HII region, G18.148−0.283, using the upgraded Giant Metre-wave Radio Telescope (uGMRT) at 1350 MHz along withother archival data. In addition to the radio continuum emission, we have detected the H169α and H170α radio recombinationlines towards G18.148−0.283 using a correlator bandwidth of 100 MHz. The moment-1 map of the ionized gas reveals a velocity
gradient of approximately 10 km s−1 across the radio continuum peaks. The 12 CO (J=3−2) molecular line data from the
COHRS survey also shows the presence of two velocity components that are very close to the velocities detected in the ionizedgas. The spectrum and position-velocity diagram from CO emission reveal molecular gas at an intermediate velocity range
bridging the velocity components. We see mid-infrared absorption and far-infrared emission establishing the presence of afilamentary infrared dark cloud, the extent of which includes the targeted HII region. The magnetic field inferred from dust
polarization is perpendicular to the filament within the HII region. We have also identified two O9 stars and 30 young stellar
objects towards the target using data from the 2MASS, UKIDSS, and GLIMPSE surveys. Cumulatively, this suggests that theregion is the site of a cloud-cloud collision that has triggered massive star formation and subsequent formation of an HII region.

4

formation of massive stellar clusters in converging galactic flows with photoionisa10. Thetion
C. L. Dobbs, T. J. R. Bending, A. R. Pettitt, M. R. Bate F We have performed simulations of cluster formation
along two regions of a spiral arm taken from a global Milky Way simulation, including photoionising feedback. One region ischaracterised by strongly converging flows, the other represents a more typical spiral arm region. We find that more massive
clusters are able to form on shorter timescales for the region with strongly converging flows. Mergers between clusters are
frequent in the case of the strongly converging flows and enable the formation of massive clusters. We compare equivalentclusters formed in simulations with and without ionisation. Photoionisation does not prevent massive cluster formation, but
can be seen to limit the masses of the clusters. On average the mass is reduced by around 20%, but we see a large spread fromionisation having minimal difference to leading to a 50% reduction in mass. Photoionisation is also able to clear out the gas in
the vicinity of the clusters on Myr timescales, which can produce clusters with larger radii that are surrounded by more massive
stellar halos. We find that the ionising feedback has more impact in our second region which is less dense and has less strongly
converging flows.

space analysis of the young stellar component of the Radcliffe Wave
11. Phase
J. Donada, F. Figueras F The Radcliffe Wave is a galactic-scale structure recently proposed by J. Alves et al. (2019).
The authors propose that various molecular complexes in the solar environment follow a specific alignment and displacementthat make them worthy of a common origin and evolution. In this work, we first collected and analyzed the population ofvery young stars and open clusters around this structure. The criteria for cross-matching these star-forming tracers with theidentified Radcliffe Wave cloud complexes have been defined and applied, all based on the quality of the available astrometricand photometric data. We performed a first characterization of the structure and kinematic properties of the young stellar
population linked to this wave. Our conclusions, although verypreliminary, are: 1) we have identified 13 open clusters, eachof them physically linked to a Cloud Complex, which are probable members of the Radcliffe Wave; 2) The OB field stars do
not present the elongated structure that departs from an straight line at the Sun position observed in the Cloud Complexes; 3)
the vertical motion of 11 CC-OCs members associated with the Wave is not contradictory with the behaviour expected from a
simple model of harmonic motion in the vertical direction, and 4) the orbits back on time neither suggest an origin associatedto a point nor to a straight line in the XZ plane.

the Potential for Radio Variability in Disks around T Tauri Stars with Obser12. Testing
vations and Chemical Modeling
C. C. Espaillat, E. Macias, J. Wendeborn, R. Franco-Hernandez, N. Calvet, A. Rilinger, L. I. Cleeves, P.
D’Alessio F A multiwavelength observing campaign of the T Tauri star (TTS) GM Aur was undertaken in 2019 Decemberthat obtained Swift X-ray and NUV fluxes, HST NUV spectra, LCOGT ugri and TESS photometry, CHIRON Halpha spectra,
ALMA 13CO and C18O line fluxes, and VLA 3 cm continuum fluxes taken contemporaneously over one month. The X-ray
to optical observations were presented previously. Here we present the ALMA and VLA data and make comparisons to GM
Aur’s accretion and X-ray properties. We report no variability in the observed millimeter CO emission. Using disk chemistrymodels, we show that the magnitude of the changes seen in the FUV luminosity of GM Aur could lead to variation of up to
6% in CO line emission and changes in the X-ray luminosity could lead to larger changes of 25%. However, the FUV and
X-ray luminosity increases must last at least 100 years in order to induce changes, which seems implausible in the TTS stage;also, these changes would be too small to be detectable by ALMA. We report no variability in the 3 cm emission observed by
the VLA, showing that changes of less than a factor of 3 in the accretion rates of TTSs do not lead to detectable changes in
the mass-loss rate traced by the jet at centimeter wavelengths. We conclude that typically seen changes in the FUV and X-ray
luminosities of TTSs do not lead to observable changes in millimeter CO line emission or jet centimeter continuum emission.

13. The Effects of Starspots on Spectroscopic Mass Estimates of Low-mass Young Stars
C. Flores, M. S. Connelley, B. Reipurth, G. Duchêne F Magnetic fields and mass accretion processes create dark andbright spots on the surface of young stars. These spots manifest as surface thermal inhomogeneities, which alter the global
temperature measured on the stars. To understand the effects and implications of these starspots, we conducted a large iSHELL
high-resolution infrared spectroscopic survey of T Tauri stars in Taurus-Auriga and Ophiuchus star-forming regions. From the
K band spectra, we measured stellar temperatures and magnetic field strengths using a magnetic radiative transfer code.
We compared our infrared-derived parameters against literature optical temperatures and found a) a systematic temperature
difference between optical and infrared observations, and b) a positive correlation between the magnetic field strengths andthe temperature differences. The discrepant temperature measurements imply significant differences in the inferred stellar
masses from stellar evolutionary models. To discern which temperature better predicts the mass of the star, we compared ourmodel-derived masses against dynamical masses measured from ALMA and PdBI for a sub-sample of our sources. From thiscomparison we conclude that, in the range of stellar masses from 0.3 to 1.3 M , neither infrared nor optical temperatures
perfectly reproduce the stellar dynamical masses. But, on average, infrared temperatures produce more precise and accurate

5stellar masses than optical ones.

14. Binary Formation in the Orion Nebula Cluster: Exploring the Sub-stellar Limit

Matthew De Furio, Michael R. Meyer, Megan Reiter, John Monnier, Adam Kraus, Trent Dupuy F We present
results constraining the multiplicity of the very low mass stars and sub-stellar objects in the Orion Nebula Cluster (ONC). Our
sample covers primary masses 0.012-0.1M using archival Hubble Space Telescope data obtained with the Advanced Camera
for Surveys using multiple filters. Studying the binary populations of clusters provides valuable constraints of how the birthenvironment affects binary formation and evolution. Prior surveys have shown that the binary populations of high-mass, highdensity star clusters like the ONC may substantially differ from those in low-mass associations. Very low mass stellar andsub-stellar binaries at wide separations, >20AU, are statistically rare in the Galactic field and have been identified in stellar
associations like Taurus-Auriga and Ophiuchus. They also may be susceptible to dynamical interactions, and their formation
may be suppressed by feedback from on-going star formation. We implement a double point-spread function (PSF) fitting
algorithm using empirical, position dependent PSF models to search for binary companions at projected separations > 10 AU(25 mas). With this technique, we identify 7 very low mass binaries, 5 of which are new detections, resulting in a binary
frequency of 12+6
−3.2 % over mass ratios of 0.5 - 1.0 and projected separations of 20 - 200 AU. We find an excess of very low mass
binaries in the ONC compared to the Galactic field, with a probability of 10−6 that the populations are statistically consistent.
The sub-stellar population of the ONC may require further dynamical processing of the lowest binding energy binaries toresemble the field population.

ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) VI: Accretion

15. shocks in the disk of DG Tau and HL Tau

A. Garufi, L. Podio, C. Codella, D. Segura-Cox, M. Vander Donckt, S. Mercimek, F. Bacciotti, D. Fedele,M. Kasper, J. E. Pineda, E. Humphreys, L. Testi F Planet-forming disks are not isolated systems. Their interaction
with the surrounding medium affects their mass budget and chemical content. In the context of the ALMA-DOT program, we
obtained high-resolution maps of assorted lines from six disks that are still partly embedded in their natal envelope. In thiswork, we examine the SO and SO2 emission that is detected from four sources: DG Tau, HL Tau, IRAS 04302+2247, andT Tau. The comparison with CO, HCO+ , and CS maps reveals that the SO and SO2 emission originates at the intersection
between extended streamers and the planet-forming disk. Two targets, DG Tau and HL Tau, offers clear cases of inflowing
material inducing an accretion shock on the disk material. The measured rotational temperatures and radial velocities are
consistent with this view. In contrast to younger Class 0 sources, these shocks are confined to the specific disk region impacted
by the streamer. In HL Tau, the known accreting streamer induces a shock in the disk outskirt, and the released SO and SO2
molecules spiral toward the star in a few hundreds years. These results suggest that shocks induced by late accreting material
may be common in the disks of young star-forming regions with possible consequences on the chemical composition and masscontent of the disk. They also highlight the importance of SO and SO2 line observations to probe accretion shocks from a larger
sample.

SPHERE survey of self-shadowed planet-forming disks
16. A
A. Garufi, C. Dominik, C. Ginski, M. Benisty, R. G. van Holstein, Th. Henning, N. Pawellek, C. Pinte, H.
Avenhaus, S. Facchini, R. Galicher, R. Gratton, F. Menard, G. Muro-Arena, J. Milli, T. Stolker, A. Vigan, M.
Villenave, T. Moulin, A. Origne, F. Rigal, J. -F. Sauvage, L. Weber F To date, nearly two hundred planet-forming
disks have been imaged with high resolution. Our propensity to study bright and extended objects is however biasing our viewof the disk demography. In this work, we contribute to alleviate this bias by analyzing fifteen disks targeted with VLT/SPHERE
that look faint in scattered light. Sources were selected based on a low far-IR excess from the spectral energy distribution.
The comparison with the ALMA images available for a few sources shows that the scattered light surveyed by these datasets isonly detected from a small portion of the disk extent. The mild anti-correlation between the disk brightness and the near-IR
excess demonstrates that these disks are self-shadowed: the inner disk rim intercepts much starlight and leaves the outer disk inpenumbra. Based on the uniform distribution of the disk brightness in scattered light across all spectral types, self-shadowing
would act similarly for inner rims at a different distance from the star. We discuss how the illumination pattern of the outerdisk may evolve with time. Some objects in the sample are proposed to be at an intermediate stage toward bright disks fromthe literature with either no shadow or with sign of azimuthally confined shadows.

6the Champagne: Dynamics and Radiation Trapping of Wind-Driven Bubbles
17. Bottling
around Massive Stars
Sam Geen, Alex de Koter F In this paper we make predictions for the behaviour of wind bubbles around young massive
stars using analytic theory. We do this in order to determine why there is a discrepancy between theoretical models thatpredict that winds should play a secondary role to photoionisation in the dynamics of HII regions, and observations of young
HII regions that seem to suggest a driving role for winds. In particular, regions such as M42 in Orion have neutral hydrogenshells, suggesting that the ionising radiation is trapped closer to the star. We first derive formulae for wind bubble evolution
in non-uniform density fields, focusing on singular isothermal sphere density fields with a power law index of -2. We find thata classical "Weaver"-like expansion velocity becomes constant in such a density distribution. We then calculate the structureof the photoionised shell around such wind bubbles, and determine at what point the mass in the shell cannot absorb all of
the ionising photons emitted by the star, causing an "overflow" of ionising radiation. We also estimate perturbations fromcooling, gravity, magnetic fields and instabilities, all of which we argue are secondary effects for the conditions studied here.
Our wind-driven model provides a consistent explanation for the behaviour of M42 to within the errors given by observational
studies. We find that in relatively denser molecular cloud environments around single young stellar sources, champagne flows
are unlikely until the wind shell breaks up due to turbulence or clumping in the cloud.

A wind-blown bubble in the Central Molecular Zone cloud G0.253+0.016

18. J. D. Henshaw, M. R. Krumholz, N. O. Butterfield, J. Mackey, A. Ginsburg, T. J. Haworth, F. NoguerasLara, A. T. Barnes, S. N. Longmore, J. Bally, J. M. D. Kruijssen, E. A. C. Mills, H. Beuther, D. L. Walker,
C. Battersby, A. Bulatek, T. Henning, J. Ott, J. D. Soler F G0.253+0.016, commonly referred to as "the Brick"and located within the Central Molecular Zone, is one of the densest (≈ 103−4 cm−3 ) molecular clouds in the Galaxy to lacksignatures of widespread star formation. We set out to constrain the origins of an arc-shaped molecular line emission feature
located within the cloud. We determine that the arc, centred on {l0 , b0 } = {0.248◦ , 0.18◦ }, has a radius of 1.3 pc and kinematics−1
indicative of the presence of a shell expanding at 5.2+2.7. Extended radio continuum emission fills the arc cavity and−1.9 km s
recombination line emission peaks at a similar velocity to the arc, implying that the molecular and ionised gas are physicallyrelated. The inferred Lyman continuum photon rate is NLyC = 1046.0 − 1047.9 photons s−1 , consistent with a star of spectral
type B1-O8.5, corresponding to a mass of ≈ 12 − 20 M . We explore two scenarios for the origin of the arc: i) a partial shell
swept up by the wind of an interloper high-mass star; ii) a partial shell swept up by stellar feedback resulting from in-situ starformation. We favour the latter scenario, finding reasonable (factor of a few) agreement between its morphology, dynamics, andenergetics and those predicted for an expanding bubble driven by the wind from a high-mass star. The immediate implication isthat G0.253+0.016 may not be as quiescent as is commonly accepted. We speculate that the cloud may have produced a . 103
M star cluster & 0.4 Myr ago, and demonstrate that the high-extinction and stellar crowding observed towards G0.253+0.016
may help to obscure such a star cluster from detection.

19. Molecules with ALMA at Planet-forming Scales (MAPS). IX. Distribution and Properties of the Large Organic Molecules HC3 N, CH3 CN, and c-C3 H2John D. Ilee, Catherine Walsh, Alice S. Booth, Yuri Aikawa, Sean M. Andrews, Jaehan Bae, Edwin A. Bergin,
Jennifer B. Bergner, Arthur D. Bosman, Gianni Cataldi, L. Ilsedore Cleeves, Ian Czekala, Viviana V. Guzmán,Jane Huang, Charles J. Law, Romane Le Gal, Ryan A. Loomis, François Ménard, Hideko Nomura, Karin IÖberg, Chunhua Qi, Kamber R. Schwarz, Richard Teague, Takashi Tsukagoshi, David J. Wilner, Yoshihide
Yamato, Ke Zhang F The precursors to larger, biologically-relevant molecules are detected throughout interstellar space,but determining the presence and properties of these molecules during planet formation requires observations of protoplanetarydisks at high angular resolution and sensitivity. Here we present 0.3" observations of HC3 N, CH3 CN, and c-C3 H2 in five protoplanetary disks observed as part of the Molecules with ALMA at Planet-forming Scales (MAPS) Large Program. We robustly
detect all molecules in four of the disks (GM Aur, AS 209, HD 163296 and MWC 480) with tentative detections of c-C3 H2and CH3 CN in IM Lup. We observe a range of morphologies – central peaks, single or double rings – with no clear correlationin morphology between molecule nor disk. Emission is generally compact and on scales comparable with the millimetre dust
continuum. We perform both disk-integrated and radially-resolved rotational diagram analysis to derive column densities androtational temperatures. The latter reveals 5-10 times more column density in the inner 50-100 au of the disks when compared with the disk-integrated analysis. We demonstrate that CH3 CN originates from lower relative heights in the disks whencompared with HC3 N, in some cases directly tracing the disk midplane. Finally, we find good agreement between the ratio ofsmall to large nitriles in the outer disks and comets. Our results indicate that the protoplanetary disks studied here are host to
significant reservoirs of large organic molecules, and that this planet- and comet-building material can be chemically similar tothat in our own Solar System. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement Series.

7

transport equation of the Autocovariance Function of the density field and
20. Generalised
mass invariant in star-forming clouds
Etienne Jaupart, Gilles Chabrier F In this Letter, we study the evolution of the autocovariance function (ACF) of density
field fluctuations in star-forming clouds and thus of the correlation length lc (ρ) of these fluctuations, which can be identified as theaverage size of the most correlated structures within the cloud. Generalizing the transport equation derived by Chandrasekhar(1951) for static, homogeneous turbulence, we show that the mass contained within these structures is an invariant, i.e. thatthe average mass contained in the most correlated structures remains constant during the evolution of the cloud, whatever
dominates the global dynamics (gravity or turbulence). We show that the growing impact of gravity on the turbulent flow yields
an increase of the variance of the density fluctuations and thus a drastic decrease of the correlation length. Theoretical relations
are successfully compared to numerical simulations. This picture brings a robust support to star formation paradigms where
the mass concentration in turbulent star-forming clouds evolves from initially large, weakly correlated filamentary structuresto smaller, denser more correlated ones, and eventually to small, tightly correlated prestellar cores. We stress that the present
results rely on a pure statistical approach of density fluctuations and do not involve any specific condition for the formationof prestellar cores. Interestingly enough, we show that, under average conditions typical of Milky Way molecular clouds, thisinvariant average mass is about a solar mass, providing an appealing explanation for the apparent universality of the IMF undersuch environments.

Discovery of a Circumsecondary Disk Transiting EPIC 220208795
21. K2
L. van der Kamp, D. M. van Dam, M. A. Kenworthy, E. E. Mamajek, G. Pojmański F Observations of the star
EPIC 220208795 (2MASS J01105556+0018507) reveal a single, deep and asymmetric eclipse, which we hypothesize is due toan eclipsing companion surrounded by a tilted and inclined opaque disk, similar to those seen around V928 Tau and EPIC
204376071. We aim to derive physical parameters of the disk and orbital parameters for the companion around the primarystar. The modeling is carried out using a modified version of the python package pyPplusS, and optimization is done using
emcee. The period analysis makes use of photometry from ground-based surveys, where we perform a period folding searchfor other possible eclipses by the disk. Parameters obtained by the best model fits are used to obtain the parameter space ofthe orbital parameters, while the most likely period obtained is used to constrain these parameters. The best model has an
opaque disk with a radius of 1.14 ± 0.03 R , an impact parameter of 0.61 ± 0.02 R , an inclination of 77.01◦ ± 0.03◦ , a tilt of
36.81◦ ± 0.05◦ and a transverse velocity of 77.45 ± 0.05 km s−1 . The two most likely periods are ∼ 290 days and ∼ 236 days,
corresponding to an eccentricity of ∼ 0.7, allowing us to make predictions for the epochs of the next eclipses. All models withtilted and inclined disks result in a minimum derived eccentricity of 0.3, which in combination with the two other known smalltransiting disk candidates V928 Tau and EPIC 204376071, suggest that there may be a common origin for their eccentric orbits.

Nobeyama 45 m Local Spur CO survey. I. Giant molecular filaments and cluster for-22. mation in the Vulpecula OB association

Mikito Kohno, Atsushi Nishimura, Shinji Fujita, Kengo Tachihara, Toshikazu Onishi, Kazuki Tokuda, Yasuo
Fukui, Yusuke Miyamoto, Shota Ueda, Ryosuke Kiridoshi, Daichi Tsutsumi, Kazufumi Torii, Tetsuhiro Minamidani, Kazuya Saigo, Toshihiro Handa, Hidetoshi Sano F We have performed new large-scale 12 CO, 13 CO, andC18 O J =1-0 observations toward the Vulpecula OB association (l ∼ 60◦ ) as part of the Nobeyama 45 m Local Spur CO survey
project. Molecular clouds are distributed over ∼ 100 pc, with local peaks at the Sh 2-86, Sh 2-87, and Sh 2-88 high-massstar-forming regions in the Vulpecula complex. The molecular gas is associated with the Local Spur, which corresponds to thenearest inter-arm region located between the Local Arm and the Sagittarius Arm. We discovered new giant molecular filaments(GMFs) in Sh 2-86, with a length of ∼ 30 pc, width of ∼ 5 pc, and molecular mass of ∼ 4 × 104 M . We also found that Sh 2-86
contains the three velocity components at 22, 27, and 33 km s−1 . These clouds and GMFs are likely to be physically associatedwith Sh 2-86 because they have high 12 CO J = 2-1 to J = 1-0 intensity ratios and coincide with the infrared dust emission.
The open cluster NGC 6823 exists at the common intersection of these clouds. We argue that the multiple cloud interaction
scenario, including GMFs, can explain cluster formation in the Vulpecula OB association.

23. Misaligned disks induced by infall

M. Kuffmeier, C. P. Dullemond, S. Reissl, F. G. Goicovic F Arc- and tail-like structures associated with disks around
Herbig stars can be a consequence of infall events occurring after the initial collapse phase of a forming star. An encounter
event of gas with a star can lead to the formation of a second-generation disk after the initial protostellar collapse phase.
Additionally, observations of shadows in disks can be well described by a configuration of misaligned inner and outer disk,
such that the inner disk casts a shadow on the outer disk. Carrying out altogether eleven 3D hydrodynamical models with themoving mesh code AREPO, we test whether a late encounter of an existing star-disk system with a cloudlet of gas can leadto the formation of an outer disk that is misaligned with respect to the primordial inner disk. Our models demonstrate that asecond-generation disk with large misalignment with respect to an existing primordial disk can easily form if the infall angle islarge. The second-generation outer disk is more eccentric, though the asymmetric infall also triggers eccentricity of the inner8

disk of e ≈ 0.05 to 0.1. Retrograde infall can lead to the formation of counter-rotating disks and enhanced accretion. As theangular momentum of the inner disk is reduced, the inner disk shrinks and a gap forms between the two disks. The resulting
misaligned disk system can survive for ∼ 100 kyr or longer without aligning each other even for low primordial disk masses
given an infall mass of ∼ 10−4 M . A synthetic image reveals shadows in the outer disk similar to the ones observed in multiple
transition disks that are caused by the misaligned inner disk. We conclude that late inclined infall onto a star-disk system leads
to the formation of a misaligned outer disk. Infall might therefore be responsible for observations of shadows in at least sometransition disks.

Formation Regulation and Self-Pollution by Stellar Wind Feedback
24. Star
Lachlan Lancaster, Eve C. Ostriker, Jeong-Gyu Kim, Chang-Goo Kim F Stellar winds contain enough energy to easily
disrupt the parent cloud surrounding a nascent star cluster, and for this reason have been considered candidates for regulatingstar formation. However, direct observations suggest most wind power is lost, and Lancaster21a,b recently proposed that this isdue to efficient mixing and cooling processes. Here, we simulate star formation with wind feedback in turbulent, self-gravitating
clouds, extending our previous work. Our simulations cover clouds with initial surface density 102 − 104 M pc−2 , and showthat star formation and residual gas dispersal is complete within 2 - 8 initial cloud free-fall times. The "Efficiently Cooled"model for stellar wind bubble evolution predicts enough energy is lost for the bubbles to become momentum-driven, we findthis is satisfied in our simulations. We also find that wind energy losses from turbulent, radiative mixing layers dominate losses
by "cloud leakage" over the timescales relevant for star formation. We show that the net star formation efficiency (SFE) in our
simulations can be explained by theories that apply wind momentum to disperse cloud gas, allowing for highly inhomogeneousinternal cloud structure. For very dense clouds, the SFE is similar to those observed in extreme star-forming environments.
Finally, we find that, while self-pollution by wind material is insignificant in cloud conditions with moderate density (only. 10−4 of the stellar mass originated in winds), our simulations with conditions more typical of a super star cluster have starparticles that form with as much as 1% of their mass in wind material.

ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – V.

25. Hierarchical fragmentation and gas dynamics in IRDC G034.43+00.24

Hong-Li Liu, Anandmayee Tej, Tie Liu, Namitha Issac, Anindya Saha, Paul F. Goldsmith, Jun-Zhi Wang,
Qizhou Zhang, Sheng-Li Qin, Ke Wang, Shanghuo Li, Archana Soam, Lokesh Dewangan, Chang Won Lee,
Pak-Shing Li, Xun-Chuan Liu, Yong Zhang, Zhiyuan Ren, Mika Juvela, Leonardo Bronfman, Yue-Fang Wu,
Ken’ichi Tatematsu, Xi Chen, Di Li, Amelia Stutz, Siju Zhang, L. Viktor Toth, Qiu-Yi Luo, Feng-Wei Xu,
Jinzeng Li, Rong Liu, Jianwen Zhou, Chao Zhang, Mengyao Tang, Chao Zhang, Tapas Baug, E. Mannfors,
Eswaraiah Chakali, Somnath Dutta F We present new 3-mm continuum and molecular lines observations from the ATOMS
survey towards the massive protostellar clump, MM1, located in the filamentary infrared dark cloud (IRDC), G034.43+00.24(G34). The lines observed are the tracers of either dense gas (e.g. HCO+/H13CO+ J = 1-0) or outflows (e.g. CS J = 2-1).
The most complete picture to date of seven cores in MM1 is revealed by dust continuum emission. These cores are found to be
gravitationally bound, with virial parameter, αvir < 2. At least four outflows are identified in MM1 with a total outflowing massof ∼ 45M , and a total energy of ∼ 1 × 1047 erg, typical of outflows from a B0-type star. Evidence of hierarchical fragmentation,
where turbulence dominates over thermal pressure, is observed at both the cloud and the clump scales. This could be linked tothe scale-dependent, dynamical mass inflow/accretion on clump and core scales. We therefore suggest that the G34 cloud could
be undergoing a dynamical mass inflow/accretion process linked to the multiscale fragmentation, which leads to the sequential
formation of fragments of the initial cloud, clumps, and ultimately dense cores, the sites of star formation.

fields in star formation: a complete compilation of all the DCF estimations
26. Magnetic
Junhao Liu, Keping Qiu, Qizhou Zhang F The Davis-Chandrasekhar-Fermi (DCF) method provides an indirect way toestimate the magnetic field strength from statistics of magnetic field orientations. We compile all the previous DCF estimations
from polarized dust emission observations and re-calculate the magnetic field strength of the selected samples with the new
DCF correction factors in Liu et al. (2021). We find the magnetic field scales with the volume density as B ∝ n0.57 . However,
the estimated power-law index of the observed B − n relation has large uncertainties and may not be comparable to the B − nrelation of theoretical models. A clear trend of decreasing magnetic viral parameter (i.e., increasing mass-to-flux ratio in unitsof critical value) with increasing column density is found in the sample, which suggests the magnetic field dominates the gravity
at lower densities but cannot compete with the gravity at higher densities. This finding also indicates that the magnetic flux
is dissipated at higher column densities due to ambipolar diffusion or magnetic recennection, and the accumulation of mass at
higher densities may be by mass flows along the magnetic field lines. Both sub-Alfvénic and super-Alfvénic states are found in
the sample, with the average state being approximately trans-Alfvénic.

9

27. Chemical survey of Class I protostars with the IRAM-30m

S. Mercimek, C. Codella, L. Podio, E. Bianchi, L. Chahine, M. Bouvier, A. Lopez-Sepulcre, R. Neri, C.
Ceccarelli F Class I protostars are a bridge between Class 0 protostars, and Class II protoplanetary disks. Recent studies
show gaps and rings in the dust distribution of disks younger than 1 Myr, suggesting that planet formation may start alreadyat the Class I stage. To understand what chemistry planets will inherit, it is crucial to characterize the chemistry of Class I
sources and to investigate how chemical complexity evolves from Class 0 protostars to protoplanetary disks. The goal is twofold:to obtain a census of the molecular complexity in a sample of four Class I protostars, and to compare it with the chemicalcompositions of earlier and later phases of the Sun-like star formation process. We performed IRAM-30m observations towards
Class I objects (L1489-IRS, B5-IRS1, L1455-IRS1, and L1551-IRS5). The column densities of the detected species are derived
assuming LTE or LVG. We detected 27 species: C-chains, N-bearing, S-bearing, Si-bearing species, deuterated molecules, andiCOMs. Different spectral profiles are observed: narrow lines towards all the sources, broader lines towards L1551-IRS5, and line
wings due to outflows. Narrow c-C3H2 emission originates from the envelope. The iCOMs in L1551-IRS5 reveal the occurrenceof hot corino chemistry, with CH3OH and CH3CN lines originating from a compact and warm region. Finally, OCS and H2Sseem to probe the circumbinary disks in the L1455-IRS1 and L1551-IRS5 binary systems. The deuteration in terms of elemental
D/H in the molecular envelopes and hot corino are derived. In addition, B5 IRS1, L1455-IRS1 and L1551-IRS5 show a low
excitation methanol line, suggesting an origin from an extended structure, plausibly UV illuminated. The abundance ratios of
iCOMs with respect CH3OH measured towards the L1551-IRS5 hot corino and the deuteration in our sample are comparable
to that estimated at earlier stages, as well as to that found in comets.

Models of Triggered Star Formation with Young Stellar Objects in Cepheus
28. Testing
OB4
Abby Mintz, Joseph L. Hora, Elaine Winston F OB associations are home to newly formed massive stars, whose turbulent
winds and ionizing flux create H II regions rich with star formation. Studying the distribution and abundance of young stellar
objects (YSOs) in these ionized bubbles can provide essential insight into the physical processes that shape their formation,
allowing us to test competing models of star formation. In this work, we examined one such OB association, Cepheus OB4 (CepOB4) - a well-suited region for studying YSOs due to its Galactic location, proximity, and geometry. We created a photometriccatalog from Spitzer/IRAC mosaics in bands 1 (3.6 µm) and 2 (4.5 µm). We supplemented the catalog with photometry from
WISE, 2MASS, IRAC bands 3 (5.8 µm) and 4 (8.0 µm), MIPS 24 µm, and MMIRS near IR data. We used color-color selections
to identify 821 YSOs, which we classified using the IR slope of the YSOs’ spectral energy distributions (SEDs), finding 67 ClassI, 103 flat spectrum, 569 Class II, and 82 Class III YSOs. We conducted a clustering analysis of the Cep OB4 YSOs and fit
their SEDs. We found many young Class I objects distributed in the surrounding shell and pillars as well as a relative age
gradient of unclustered sources, with YSOs generally decreasing in age with distance from the central cluster. Both of theseresults indicate that the expansion of the H II region may have triggered star formation in Cep OB4.

29. Star burst in W49N presumably induced by cloud-cloud collision

Ryosuke Miyawaki, Masahiko Hayashi, Tetsuo Hasegawa F We present high resolution observations of CS(J=1-0),
H13CO+ (J=1-0), and SiO(v=0:J=1-0) lines, together with the 49GHz and 86GHz continuum emissions, toward W49N carriedout with Nobeyama Millimeter Array. We identified 11 CS, 8 H13CO+, and 6 SiO clumps with radii of 0.1-0.5pc. The CS
and H13CO+ clumps are mainly divided into two velocity components, one at 4kms-1 and the other at 12kms-1, while the SiO
clumps have velocities between the two components. The SiO emission is distributed toward the UCHII ring, where the 4kms-1
component clumps of CS and H13CO+ also exist. The 12kms-1 component clumps of CS are detected at the east and westof the UCHII ring with an apparent hole toward the ring. The clump masses vary from 4.4x102 M to 4.9x104 M with themean values of 0.94x104 M , 0.88x104 M , and 2.2x104 M for the CS, H13CO+, and SiO clumps, respectively. The total
masses derived from CS, H13CO+, and SiO clumps are 1.0x105 M , 0.70x105 M , and 1.3x105 M , respectively, which agree
well with the corresponding virial masses of 0.71x105 M , 1.3x105 M , and 0.88x105 M , respectively. The average molecularhydrogen densities of the clumps are 0.90x106 cm-3, 1.4x106 cm-3, and 7.6x106 cm-3 for the CS, H13CO+ and SiO clumps,
respectively. The density derived from the SiO clumps seems significantly higher than those from the others, probably because
the SiO emission is produced in high density shocked regions. The free fall time scale of the clumps is estimated to be 3x104
yr, which gives an accretion rate of 3x10−3 − 1 M /yr onto a stellar core. The observed clumps are, if they are undergoing freefall, capable of producing dozens of massive stars in the next 105 yr. We propose a view that pre-existing two clouds collided
with each other almost face-on to produce the observed clumps and triggered the burst of massive star formation in W49N.

30 A cold accretion flow onto one component of a multiple protostellar system
Nadia M. Murillo, Ewine F. van Dishoeck, Alvaro Hacar, Daniel Harsono, Jes K. Jørgensen F Context: Gas. accretion flows transport material from the cloud core onto the protostar. In multiple protostellar systems, it is not clear if thedelivery mechanism is preferential or evenly distributed among the components. Aims: Gas accretion flows within IRAS16293
is explored out to 6000 AU. Methods: ALMA Band 3 observations of low-J transitions of HNC, cyanopolyynes (HC3 N, HC5 N),

10and N2 H+ are used to probe the cloud core structure at 100 AU resolution. Additional Band 3 archival data provide low-J
HCN and SiO lines. These data are compared with the corresponding higher-J lines from the PILS Band 7 data for excitation
analysis. The HNC/HCN ratio is used as a temperature tracer. Results: The low-J transitions of HC3 N, HC5 N, HNC andN2 H+ trace extended and elongated structures from 6000 AU down to 100 AU, without accompanying dust continuum emission.
Two structures are identified: one traces a flow that is likely accreting toward the most luminous component of the system
IRAS16293 A. Temperatures inferred from the HCN/HNC ratio suggest that the gas in this flow is cold, between 10 and 30
K. The other structure is part of an UV-irradiated cavity wall entrained by one of the outflows. The two outflows driven by
IRAS16293 A present different molecular gas distributions. Conclusions: Accretion of cold gas is seen from 6000 AU scales
onto IRAS16293 A, but not onto source B, indicates that cloud core material accretion is competitive due to feedback onto
a dominant component in an embedded multiple protostellar system. The preferential delivery of material could explain thehigher luminosity and multiplicity of source A compared to source B. The results of this work demonstrate that several different
molecular species, and multiple transitions of each species, are needed to confirm and characterize accretion flows in protostellar
cloud cores.

Pebbles and Planetesimals to Planets and Dust: the Protoplanetary Disk–Debris
31. From
Disk Connection
Joan R. Najita, Scott J. Kenyon, Benjamin C. Bromley F The similar orbital distances and detection rates of debris
disks and the prominent rings observed in protoplanetary disks suggest a potential connection between these structures. We
explore this connection with new calculations that follow the evolution of rings of pebbles and planetesimals as they grow intoplanets and generate dusty debris. Depending on the initial solid mass and planetesimal formation efficiency, the calculations
predict diverse outcomes for the resulting planet masses and accompanying debris signature. When compared with debris
disk incidence rates as a function of luminosity and time, the model results indicate that the known population of bright colddebris disks can be explained by rings of solids with the (high) initial masses inferred for protoplanetary disk rings and modest
planetesimal formation efficiencies that are consistent with current theories of planetesimal formation. These results support
the possibility that large protoplanetary disk rings evolve into the known cold debris disks. The inferred strong evolutionary
connection between protoplanetary disks with large rings and mature stars with cold debris disks implies that the remaining
majority population of low-mass stars with compact protoplanetary disks leave behind only modest masses of residual solids
at large radii and evolve primarily into mature stars without detectable debris beyond 30 au. The approach outlined here
illustrates how combining observations with detailed evolutionary models of solids strongly constrains the global evolution of
disk solids and underlying physical parameters such as the efficiency of planetesimal formation and the possible existence ofinvisible reservoirs of solids in protoplanetary disks.

of IRAS 05168+3634 star-forming region
32. Structure
E. H. Nikoghosyan, N. M. Azatyan, D. H. Andreasyan, D. S. Baghdasaryan F This study aims to determine themain physical parameters (N(H2) hydrogen column density and Td dust temperature) of the Interstellar medium, and theirdistribution in the extended star-forming region, which includes IRAS 05156+3643, 05162+3639, 05168+3634, 05177+3636,
and 05184+3635 sources. We also provide a comparative analysis of the properties of the Interstellar medium and young stellar
objects. Analysis of the results revealed that Interstellar medium forms relativity dense condensations around IRAS sources,
which are interconnected by a filament structure. In general, in sub-regions Td varies from 11 to 24 K, and N(H2) - from 1.0
to 4.0 x 1023 cm−2 . The masses of the ISM vary from 1.7 x 104 to 2.1 x 105 Msol. All BGPSv2 objects identified in thisstar-forming region are located at the N(H2) maximum. The direction of the outflows, which were found in two sub-regions,
IRAS 05168+3634 and 05184+3635, correlates well with the isodenses direction. The sub-regions with the highest N(H2) andInterstellar medium mass have the largest percentage of young stellar objects with Class I evolutionary stage. The wide spreadof the evolutionary ages of stars in all sub-regions (from 105 to 107 years) suggests that the process of star formation in theconsidered region is sequential. In those sub-regions where the mass of the initial, parent molecular cloud is larger, this process
is likely to proceed more actively. On the Gaia EDR3 database, it can be assumed that all sub-regions are embedded in the
single molecular cloud and belong to the same star-forming region, which is located at a distance of about 1.9 kpc.

Cores to Build Star Cluster Multiple Populations
33. Rebounding
G. Parmentier, A. Pasquali F We present a novel approach to the riddle of star cluster multiple populations. Stars form
from molecular cores. But not all cores form stars. Following their initial compression, such ’failed’ cores re-expand, rather
than collapsing. We propose that their formation and subsequent dispersal regulate the gas density of cluster-forming clumps
and, therefore, their core and star formation rates. Clumps for which failed cores are the dominant core type experience starformation histories with peaks and troughs. In contrast, too few failed cores results in smoothly decreasing star formation
rates. We identify three main parameters shaping the star formation history of a clump: the star and core formation efficiencies
per free-fall time, and the time-scale on which failed cores return to the clump gas. The clump mass acts as a scaling factor.
We use our model to constrain the density and mass of the Orion Nebula Cluster progenitor clump, and to caution that the11star formation histories of starburst clusters may contain close-by peaks concealed by stellar age uncertainties. Our model
generates a great variety of star formation histories. Intriguingly, the chromosome maps and O-Na anti-correlations of old
globular clusters also present diverse morphologies. This prompts us to discuss our model in the context of globular cluster
multiple stellar populations. More massive globular clusters exhibit stronger multiple stellar population patterns, which ourmodel can explain if the formation of the polluting stars requires a given stellar mass threshold.

34. Chemical environments of 6.7 GHz methanol maser sources

Sonu Tabitha Paulson, Jagadheep D. Pandian F 6.7 GHz methanol masers are the brightest of class II methanol masersthat are regarded as excellent signposts in the formation of young massive stars. We present here a molecular line study of 68
6.7 GHz methanol maser hosts chosen from the MMB catalogue, that have MALT90 data available. We performed (1) pixelby-pixel study of 9 methanol maser sources that have high signal-to-noise ratio and (2) statistical study taking into accountthe entire 68 sources. We estimated the molecular column densities and abundances of N2 H+ (1-0), HCO+ (1-0), HCN(1-0) andHNC(1-0) lines. The derived abundances are found to be in congruence with the typical values found towards high mass star
forming regions. We derived the column density and abundance ratios between these molecular species as an attempt to unveil
the evolutionary stage of methanol maser sources. We found the column density and abundance ratio of HCN to HNC toincrease and that of N2 H+ to HCO+ to decline with source evolution, as suggested by the chemical models. The HCN/HNC,
N2 H+ /HCO+ , HNC/HCO+ and N2 H+ /HNC ratios of the methanol maser sources are consistent with them being at a later
evolutionary state than quiescent phase and possibly protostellar phase, but at an earlier stage than HII regions and PDRs.

35. Galactic Star Formation with NIKA2 (GASTON): Evidence of mass accretion onto
dense clumps

GASTON collaboration A. J. Rigby et al. F High-mass stars (m∗ & 8 M ) play a crucial role in the evolution of galaxies,
and so it is imperative that we understand how they are formed. We have used the New IRAM KIDs Array 2 (NIKA2) cameraon the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope to conduct high-sensitivity continuum mapping of∼ 2 deg2 of the Galactic plane (GP) as part of the Galactic Star Formation with NIKA2 (GASTON) large program. We haveidentified a total of 1467 clumps within our deep 1.15 mm continuum maps and, by using overlapping continuum, molecular line,
and maser parallax data, we have determined their distances and physical properties. By placing them upon an approximate
evolutionary sequence based upon 8 µm Spitzer imaging, we find evidence that the most massive dense clumps accrete material
from their surrounding environment during their early evolution, before dispersing as star formation advances, supporting
clump-fed models of high-mass star formation.

Bank-LOFAR Carbon Radio Recombination Line observations toward
36. Arecibo-Green
cold HI Clouds
D. Anish Roshi, W. M. Peters, K. L. Emig, P. Salas, J. B. R. Oonk, M. E. Lebrón, J. M. Dickey F We present
results from a search for radio recombination lines in three HI self-absorbing (HISA) clouds at 750 MHz and 321 MHz with theRobert C. Byrd Green Bank Telescope (GBT), and in three Galactic Plane positions at 327 MHz with the Arecibo Telescope.
We detect Carbon Recombination Lines (CRRLs) in the direction of DR4 and DR21, as well as in the galactic plane position
G34.94+0.0. We additionally detect Hydrogen Recombination Lines (HRRLs) in emission in five of the six sightlines, anda Helium line at 750 MHz towards DR21. Combining our new data with 150 MHz LOFAR detections of CRRL absorption
towards DR4 and DR21, we estimate the electron densities of the line forming regions by modeling the line width as a functionof frequency. The estimated densities are in the range 1.4 → 6.5 cm−3 towards DR4, for electron temperatures 200 → 20 K. A
dual line forming region with densities between 3.5 → 24 cm−3 and 0.008 → 0.3 cm−3 could plausibly explain the observed line
width as a function of frequency on the DR21 sightline. The central velocities of the CRRLs compare well with CO emissionand HISA lines in these directions. The cloud densities estimated from the CO lines are smaller (at least a factor of 5) thanthose of the CRRL forming regions. It is likely that the CRRL forming and HI self-absorbing gas is located in a denser, shocked
region either at the boundary of or within the CO emitting cloud.

37. Which Part of Dense Cores Feeds Material to Protostars?: The Case of L1489 IRS

Jinshi Sai, Nagayoshi Ohashi, Anaëlle J. Maury, Sébastien Maret, Hsi-Wei Yen, Yusuke Aso, Mathilde Gaudel
F We have conducted mapping observations (∼ 20 × 20 ) of the Class I protostar L1489 IRS using the 7-m array of the Atacama
Compact Array (ACA) and the IRAM-30m telescope in the C18 O 2-1 emission to investigate the gas kinematics on 1000-10,000
au scales. The C18 O emission shows a velocity gradient across the protostar in a direction almost perpendicular to the outflow.
The radial profile of the peak velocity was measured from a C18 O position-velocity diagram cut along the disk major axis. The
measured peak velocity decreases with radius at a radii of ∼1400-2900 au, but increases slightly or is almost constant at radiiof r &2900 au. Disk-and-envelope models were compared with the observations to understand the nature of the radial profileof the peak velocity. The measured peak velocities are best explained by a model where the specific angular momentum is12

constant within a radius of 2900 au but increases with radius outside 2900 au. We calculated the radial profile of the specificangular momentum from the measured peak velocities, and compared it to analytic models of core collapse. The analytic
models reproduce well the observed radial profile of the specific angular momentum and suggest that material within a radius of∼4000-6000 au in the initial dense core has accreted to the central protostar. Because dense cores are typically ∼10,000-20,000
au in radius, and as L1489 IRS is close to the end of mass accretion phase, our result suggests that only a fraction of a dense
core eventually forms a star.

properties of cm-sized high-porosity ice and dust aggregates and their appli38. Collisional
cations to early planet formation
Rainer R. Schräpler, Wolf A. Landeck, Jürgen Blum F In dead zones of protoplanetary discs, it is assumed thatmicrometre-sized particles grow Brownian, sediment to the midplane and drift radially inward. When collisional compaction
sets in, the growing aggregates collect slower and therefore dynamically smaller particles. This sedimentation and growth phaseof highly porous ice and dust aggregates is simulated with laboratory experiments in which we obtained mm- to cm-sized ice
aggregates with a porosity of 90% as well as cm-sized dust agglomerates with a porosity of 85%. We modelled the growth
process during sedimentation in an analytical calculation to compute the agglomerate sizes when they reach the midplane ofthe protoplanetary disc. In the midplane, the dust particles form a thin dense layer and gain relative velocities by, e.g., thestreaming instability or the onset of shear turbulence. To investigate also these collisions, we performed additional laboratory
drop tower experiments with the high-porosity aggregates formed in the sedimentary-growth experiments and determined theirmechanical parameters, including their sticking threshold velocity, which is important for their further collisional evolution
on their way to form planetesimals. Finally, we developed a method to calculate the packing-density-dependent fundamental
properties of our dust and ice agglomerates, the Young’s modulus, the Poisson ratio, the shear viscosity and the bulk viscosity
from compression measurements. With these parameters, it was possible to derive the coefficient of restitution which fits ourmeasurements. In order to physically describe these outcomes, we applied a collision model. With this model, predictions about
general dust-aggregate collisions are possible.

phase Elemental abundances in Molecular cloudS (GEMS) V. Methanol in Taurus
39. GasS. Spezzano, A. Fuente, P. Caselli, A. Vasyunin, D. Navarro-Almaida, M. Rodríguez-Baras, A. Punanova, C.
Vastel, V. Wakelam F Methanol, one of the simplest complex organic molecules in the Interstellar Medium (ISM), has beenshown to be present and extended in cold environments such as starless cores. We aim at studying methanol emission acrossseveral starless cores and investigate the physical conditions at which methanol starts to be efficiently formed, as well as how thephysical structure of the cores and their surrounding environment affect its distribution. Methanol and C18 O emission lines at 3mm have been observed with the IRAM 30m telescope within the large program "Gas phase Elemental abundances in Molecular
CloudS" (GEMS) towards 66 positions across 12 starless cores in the Taurus Molecular Cloud. A non-LTE radiative transfer
code was used to compute the column densities in all positions. We then used state-of-the-art chemical models to reproduce
our observations. We have computed N(CH3 OH)/N(C18 O) column density ratios for all the observed offsets, and two different
behaviours can be recognised: the cores where the ratio peaks at the dust peak, and the cores where the ratio peaks with aslight offset with respect to the dust peak (∼10000 AU). We suggest that the cause of this behaviour is the irradiation on the
cores due to protostars nearby which accelerate energetic particles along their outflows. The chemical models, which do nottake into account irradiation variations, can reproduce fairly well the overall observed column density of methanol, but cannot
reproduce the two different radial profiles observed. We confirm the substantial effect of the environment onto the distributionof methanol in starless cores. We suggest that the clumpy medium generated by protostellar outflows might cause a more
efficient penetration of the interstellar radiation field in the molecular cloud and have an impact on the distribution of methanol
in starless cores.

40. The "Maggie" filament: Physical properties of a giant atomic cloud

J. Syed, J. D. Soler, H. Beuther, Y. Wang, S. Suri, J. D. Henshaw, M. Riener, S. Bialy, S. Rezaei Kh., J. M.
Stil, P. F. Goldsmith, M. R. Rugel, S. C. O. Glover, R. S. Klessen, J. Kerp, J. S. Urquhart, J. Ott, N. Roy,N. Schneider, R. J. Smith, S. N. Longmore, H. Linz F The atomic phase of the interstellar medium plays a key role in
the formation process of molecular clouds. Due to the line-of-sight confusion in the Galactic plane that is associated with its
ubiquity, atomic hydrogen emission has been challenging to study. Employing the high-angular resolution data from the THOR
survey, we identify one of the largest, coherent, mostly atomic HI filaments in the Milky Way at the line-of-sight velocities
around -54 km/s. The giant atomic filament "Maggie", with a total length of 1.2 kpc, is not detected in most other tracers,
and does not show signs of active star formation. At a kinematic distance of 17 kpc, Maggie is situated below (by 500 pc) but
parallel to the Galactic HI disk and is trailing the predicted location of the Outer Arm by 5-10 km/s in longitude-velocity space.
The centroid velocity exhibits a smooth gradient of less than ±3 km/s /10 pc and a coherent structure to within ±6 km/s.
The line widths of 10 km/s along the spine of the filament are dominated by non-thermal effects. After correcting for opticaldepth effects, the mass of Maggie’s dense spine is estimated to be 7.2 × 105 M . The mean number density of the filament is13

4 cm−3 , which is best explained by the filament being a mix of cold and warm neutral gas. In contrast to molecular filaments,
the turbulent Mach number and velocity structure function suggest that Maggie is driven by transonic to moderately supersonicvelocities that are likely associated with the Galactic potential rather than being subject to the effects of self-gravity or stellar
feedback. The column density PDF displays a log-normal shape around a mean of NHI = 4.8 × 1020 cm−2 , thus reflecting theabsence of dominating effects of gravitational contraction.

Flows or Outflow Cavities? Uncovering the Gas Dynamics around Lupus
41. Accretion
3-MMS
Travis J. Thieme, Shih-Ping Lai, Sheng-Jun Lin, Pou-Ieng Cheong, Chin-Fei Lee, Hsi-Wei Yen, Zhi-Yun Li, Ka
Ho Lam, Bo Zhao F Understanding how material accretes onto the rotationally supported disk from the surrounding envelopeof gas and dust in the youngest protostellar systems is important for describing how disks are formed. Magnetohydrodynamic
simulations of magnetized, turbulent disk formation usually show spiral-like streams of material (accretion flows) connecting theenvelope to the disk. However, accretion flows in these early stages of protostellar formation still remain poorly characterized
due to their low intensity and possibly some extended structures are disregarded as being part of the outflow cavity. We use
ALMA archival data of a young Class 0 protostar, Lupus 3-MMS, to uncover four extended accretion flow-like structures in
C18 O that follow the edges of the outflows. We make various types of position-velocity cuts to compare with the outflows andfind the extended structures are not consistent with the outflow emission, but rather more consistent with a simple infall model.
We then use a dendrogram algorithm to isolate five sub-structures in position-position-velocity space. Four out of the five substructures fit well (>95%) with our simple infall model, with specific angular momenta between 2.7 − 6.9 × 10−4 km s−1 pc andmass-infall rates of 0.5−1.1×10−6 M yr−1 . Better characterization of the physical structure in the supposed "outflow-cavities"
is important to disentangle the true outflow cavities and accretion flows.

42. The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars V. A Characterization of Protostellar Multiplicity

John J. Tobin, Stella S. R. Offner, Kaitlin M. Kratter, S. Thomas Megeath, Patrick D. Sheehan, Leslie W.
Looney, Ana Karla Diaz-Rodriguez, Mayra Osorio, Guillem Anglada, Sarah I. Sadavoy, Elise Furlan, DominiqueSegura-Cox, Nicole Karnath, Merel L. R. van ’t Hoff, Ewine F. van Dishoeck, Zhi-Yun Li, Rajeeb Sharma,
Amelia M. Stutz, Lukasz Tychoniec F We characterize protostellar multiplicity in the Orion molecular clouds using ALMA
0.87 mm and VLA 9 mm continuum surveys toward 328 protostars. These observations are sensitive to projected spatial separations as small as ∼20 au, and we consider source separations up to 104 au as potential companions. The overall multiplicity
fraction (MF) and companion fraction (CF) for the Orion protostars are 0.30±0.03 and 0.44±0.03, respectively, considering
separations from 20 to 104 au. The MFs and CFs are corrected for potential contamination by unassociated young stars using aprobabilistic scheme based on the surface density of young stars around each protostar. The companion separation distribution
as a whole is double peaked and inconsistent with the separation distribution of solar-type field stars, while the separation distribution of Flat Spectrum protostars is consistent solar-type field stars. The multiplicity statistics and companion separation
distributions of the Perseus star-forming region are consistent with those of Orion. Based on the observed peaks in the Class
0 separations at ∼100 au and ∼103 au, we argue that multiples with separations <500 au are likely produced by both disk
fragmentation and turbulent fragmentation with migration, and those at 103 au result primarily from turbulent fragmentation.
We also find that MFs/CFs may rise from Class 0 to Flat Spectrum protostars between 100 and 103 au in regions of highYSO density. This finding may be evidence for migration of companions from >103 au to <103 au, and that some companions
between 103 and 104 au must be (or become) unbound.

simulations of evolving rotational distributions of low-mass stars in young
43. Monte-Carlo
open clusters. Testing the influence of initial conditions
Maria Jaqueline Vasconcelos, Jérôme Bouvier, Florian Gallet, Edson A. Luz Filho F The rotational evolution of ayoung stellar population can give informations about the rotation pattern of more evolved clusters. Combined with rotational
period values of thousands of young stars and theoretical propositions about the redistribution and loss of stellar angularmomentum, it allows us to trace the rotational history of stars according to their mass. We want to investigate how internaland environmental changes on single stars can change the rotational evolution of a young stellar population. We run Monte
Carlo simulations of a young cluster composed by solar mass stars of 0.5, 0.8 and 1.0 M from 1 to 550 Myr taking into accountobservational and theoretical parameters. In order to compare our results with the observations we run Kolmogorov-Smirnov
tests. Our standard model is able to reproduce some clusters younger than h Per and marginally M37, which is 550 Myr old.
Varying the disk fraction or the initial period distribution did not improve the results. However, when we run a model with afiner mass grid the Pleiades can be also reproduced. Changing the initial mass distribution to be similar to the empirical ONC
mass function also gives good results. Modeling the evolution of a young synthetic cluster from pre-main sequence to early main
sequence considering physical mechanisms of extraction and exchange of angular momentum can not be achieved successfully
for all clusters for which we have enough rotational data. Clusters of about the same age present different rotational behaviors

14due perhaps to differences in their initial conditions.

44. A Kpc Scale Molecular Wave in the Inner Galaxy: Feather of the Milky Way?

V. S. Veena, P. Schilke, Á. Sánchez-Monge, M. C. Sormani, R. S. Klessen, F. Schuller, D. Colombo, T. Csengeri,
M. Mattern, J. S. Urquhart F We report the discovery of a velocity coherent, kpc-scale molecular structure towards the
Galactic center region with an angular extent of 30deg and an aspect ratio of 60:1. The kinematic distance of the CO structure
ranges between 4.4 to 6.5 kpc. Analysis of the velocity data and comparison with the existing spiral arm models support thata major portion of this structure is either a sub-branch of the Norma arm or an inter-arm giant molecular filament, likely to bea kpc-scale feather (or spur) of the Milky Way, similar to those observed in nearby spiral galaxies. The filamentary cloud is atleast 2.0 kpc in extent, considering the uncertainties in the kinematic distances, and it could be as long as 4 kpc. The vertical
distribution of this highly elongated structure reveals a pattern similar to that of a sinusoidal wave. The exact mechanisms
responsible for the origin of such a kpc-scale filament and its wavy morphology remains unclear. The distinct wave-like shapeand its peculiar orientation makes this cloud, named as the Gangotri wave, one of the largest and most intriguing structures
identified in the Milky Way.

physical parameters in Orion KL at high spatial resolution
45. Mapping
Olivia H. Wilkins, P. Brandon Carroll, Geoffrey A. Blake F The Orion Kleinmann-Low nebula (Orion KL) is notoriously
complex and exhibits a range of physical and chemical components. We conducted high angular resolution (sub-arcsecond)observations of 1 3CH3 OH ν = 0 (∼0.300 and ∼0.700 ) and CH3 CN ν8 = 1 (∼0.200 and ∼0.900 ) line emission with the Atacama Large
Millimeter/submillimeter Array (ALMA) to investigate Orion KL’s structure on small spatial scales (≤350 au). Gas kinematics,
excitation temperatures, and column densities were derived from the molecular emission via a pixel-by-pixel spectral line fittingof the image cubes, enabling us to examine the small-scale variation of these parameters. Sub-regions of the Hot Core have ahigher excitation temperature in a 0.200 beam than a 0.900 beam, indicative of possible internal sources of heating. Furthermore,
the velocity field includes a bipolar ∼7−8 km s−1 feature with a southeast-northwest orientation against the surrounding ∼4−5
km s−1 velocity field, which may be due to an outflow. We also find evidence of a possible source of internal heating toward theNorthwest Clump, since the excitation temperature there is higher in a smaller beam versus a larger beam. Finally, the region
southwest of the Hot Core (Hot Core-SW) presents itself as a particularly heterogeneous region bridging the Hot Core andCompact Ridge. Additional studies to identify the (hidden) sources of luminosity and heating within Orion KL are necessary
to better understand the nebula and its chemistry.

Instability with Multiple Dust Species: II. Turbulence and Dust-Gas Dy46. Streaming
namics at Nonlinear Saturation
Chao-Chin Yang, Zhaohuan Zhu F The streaming instability is a fundamental process that can drive dust-gas dynamics
and ultimately planetesimal formation in protoplanetary discs. As a linear instability, it has been shown that its growth witha distribution of dust sizes can be classified into two distinct regimes, fast- and slow-growth, depending on the dust-size distribution and the total dust-to-gas density ratio . Using numerical simulations of an unstratified disc, we bring three cases indifferent regimes into nonlinear saturation. We find that the saturation states of the two fast-growth cases are similar to its
single-species counterparts. The one with maximum dimensionless stopping time τs,max = 0.1 and  = 2 drives turbulent verticaldust-gas vortices, while the other with τs,max = 2 and  = 0.2 leads to radial traffic jams and filamentary structures of dust
particles. The dust density distribution for the former is flat in low densities, while the one for the latter has a low-end cutoff.
By contrast, the one slow-growth case results in a virtually quiescent state. Moreover, we find that in the fast-growth regime,
significant dust segregation by size occurs, with large particles moving towards dense regions while small particles remain in the
diffuse regions, and the mean radial drift of each dust species is appreciably altered from the (initial) drag-force equilibrium. The
former effect may skew the spectral index derived from multi-wavelength observations and change the initial size distributionof a pebble cloud for planetesimal formation. The latter along with turbulent diffusion may influence the radial transport andmixing of solid materials in young protoplanetary discs.

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