The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 357 — 30 September 2022
Editor: João Alveswww.starformation.news

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Cover image caption
Barnard 59, or B59, is the northern tip of the nearby Pipe Nebula dark cloud (the Pipe’s mouthpiece). Barnard 59 contains
about 20 YSOs, most deeply embedded towards this cloud’s center, and it is one of the closest embedded clusters of YSOs to
Earth, less well studied than the better-known L1688 in Ophiuchus (rho Oph core). The image was captured by the Wide Field
Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory.
Credit: ESO, MPG/ESO 2.2-m telescope
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. Ices in planet-forming disks: Self-consistent ice opacities in disk models

Aditya M. Arabhavi, Peter Woitke, Stephanie M. Cazaux, Inga Kamp, Christian Rab, Wing-Fai Thi F In coldand shielded environments, molecules freeze out on dust grain surfaces to form ices such as H2O, CO, CO2, CH4, CH3OH,
and NH3. In protoplanetary disks, the exact radial and vertical ice extension depend on disk mass, geometry, and stellar UV
irradiation. The goal of this work is to present a computationally efficient method to compute ice and bare-grain opacities inprotoplanetary disk models consistently with the chemistry and to investigate the effect of ice opacities on the physico-chemical
state and optical appearance of the disk. A matrix of Mie efficiencies is pre-calculated for different ice species and thicknesses,
from which the position dependent opacities of icy grains are then interpolated. This is implemented in the PRODIMO codeby a self-consistent solution of ice opacities and the local composition of ices, which are obtained from our chemical network.
Locally, the opacity can change significantly, for example, an increase by a factor of more than 200 in the midplane, especiallyat UV and optical wavelengths, due to ice formation. This is mainly due to changes in the size distribution of dust grains
resulting from ice formation. However, since the opacity only changes in the optically thick regions of the disk, the thermal disk
structure does not change significantly. For the same reason, the spectral energy distributions computed with our disk models
with ice opacities generally show only faint ice emission features at far-IR wavelengths. The ice absorption features are only
seen in the edgeon orientation. The assumption made on how the ice is distributed across the grain size distribution influences
the far-IR and millimeter slope of the SED. The ice features and their strengths are influenced by the ice power law and thetype of chemistry. Our models predict stronger ice features for observations that can spatially resolve the disk, particularly inabsorption.

2. Tracing the contraction of the pre-stellar core L1544 with HC17 O+ J = 1-0 emission

J. Ferrer Asensio, S. Spezzano, P. Caselli, F. O. Alves, O. Sipilä, E. Redaelli, L. Bizzocchi, F. Lique, A. Mullins
F Spectral line profiles of several molecules observed towards the pre-stellar core L1544 appear double-peaked. For abundant
molecular species this line morphology has been linked to self-absorption. However, the physical process behind the doublepeaked morphology for less abundant species is still under debate. In order to understand the cause behind the double-peaked
spectra of optically thin transitions and their link to the physical structure of pre-stellar cores, we present high-sensitivity
and high-spectral resolution HC17 O+ J =1-0 observations towards the dust peak in L1544. We observed the HC17 O+ (1-0)
spectrum with the Institut de Radioastronomie Millimétrique (IRAM) 30m telescope. By using new state-of-the-art collisional
rate coefficients, a physical model for the core and the fractional abundance profile of HC17 O+ , the hyperfine structure of thismolecular ion is modelled for the first time with the radiative transfer code LOC applied to the predicted chemical structure of acontracting pre-stellar core. We applied the same analysis to the chemically related C17 O molecule. The observed HC17 O+ (1-0)
and C17 O(1-0) lines have been successfully reproduced with a non-local thermal equilibrium (LTE) radiative transfer model2

applied to chemical model predictions for a contracting pre-stellar core. An upscaled velocity profile (by 30observations. The
double peaks observed in the HC17 O+ (1-0) hyperfine components are due to the contraction motions at densities close to thecritical density of the transition (∼105 cm−3 ) and to the fact that the HCO+ fractional abundance decreases toward the centre.

comets ejected early on during Solar System formation
3. Volatile-rich
S. E. Anderson, J. -M. Petit, B. Noyelles, O. Mousis, P. Rousselot F Comet C/2016 R2 PanSTARRS (hereafter
C/2016 R2) presents an unusually high N2/CO abundance ratio, as well as a heavy depletion in H2O, making it the only known
comet of its kind. Understanding its dynamical history is therefore of essential importance as it would allow us to gain a clearer
understanding of the evolution of planetesimal formation in our Solar System. Two studies have independently estimated thepossible origin of this comet from building blocks formed in a peculiar region of the protoplanetary disk, near the ice lineof CO and N2. We intend to investigate the fates of objects formed from the building blocks in these regions. We hope tofind a possible explanation for the lack of C/2016 R2-like comets in our Solar System. Using a numerical simulation of theearly stages of Solar System formation, we track the dynamics of these objects in the Jumping Neptune scenario based on fivedifferent initial conditions for the protosolar disk. We integrate the positions of 250 000 planetesimals over time in order toanalyze the evolution of their orbits and create a statistical profile of their expected permanent orbit. Results. We find that
objects formed in the region of the CO- and N2- ice lines are highly likely to be sent towards the Oort Cloud or possibly ejectedfrom the Solar System altogether on a relatively short timescale. In all our simulations, over 90in this region evolved into a
hyperbolic trajectory, and between 1were potentially captured by the Oort Cloud. The handful of comets that remained were
either on long-period, highly eccentric orbits like C/2016 R2, or absorbed into the Edgeworth-Kuiper belt. Comets formed <15
au were predominantly ejected early in the formation timeline. As this is the formation zone likely to produce comets of thiscomposition, this process could explain the lack of similar comets observed in the Solar System

The Star Formation-Gas Density Relation in Four Galactic GMCs: Effects of Stellar

4. Feedback

John H. Bieging, Shuo Kong F We present maps of 4 galactic giant molecular clouds (GMCs) in the J=2-1 emission ofboth CO and 13 CO. We use an LTE analysis to derive maps of the CO excitation temperature and column density and the
distribution of total molecular gas column density, Σgas . The depletion of CO by freeze-out onto cold dust grains is accounted
for by an approximation to the results of Lewis et al. (2021) which were derived from far-IR observations with Herschel. The
surface density of young stellar objects (YSOs) is obtained from published catalogs. The mean YSO surface density exhibits apower-law dependence on Σgas , with exponents in the range 0.9 to 1.9. Gas column density probability distribution functions(PDFs) show power-law tails extending to high column densities. The distributions of sonic Mach number, MS are sharply
peaked at MS ∼ 5 − 8 for 3 GMCs; a fourth has a broad distribution up to MS = 30, possibly a result of feedback effects
from multiple OB stars. An analysis following the methodology of Pokhrel et al. (2021) finds that our sample of GMCs shows
power-law relations that are somewhat shallower than found by Pokhrel et al. (2021) for the star formation rate vs. < Σgas >and vs. < Σgas > /tf f in a different sample of clouds. We discuss possible differences in the two samples of star-forming clouds
and the effects of stellar feedback on the relation between gas density and star formation rate.

Explosive Dispersal Outflow in IRAS 16076-5134 revealed with ALMA
5. Possible
Estrella Guzmán Ccolque, Manuel Fernández-López, Luis A. Zapata, Tapas Baug F We present 0.9 mm continuumand CO (3-2) line emission observations retrieved from the Atacama Large Millimeter/submillimeter Array (ALMA) archive
toward the high-mass star formation region IRAS 16076-5134. We identify fourteen dense cores with masses between 0.3 to
22 M . We find an ensemble of filament-like CO (3-2) ejections from -62 to +83 km s−1 that appear to arise radially from acommon central position, close to the dense core MM8. The ensemble of filaments, has a quasi-isotropic distribution in the planeof the sky. The radial velocity of several filaments follow a linear velocity gradient, incresing from a common origin. Considering
the whole ensemble of filaments, we estimate its total mass to be 138 and 216 M from its CO emission, for 70 K and 140 K
respectively. Also, assuming a constant velocity expansion of the filaments (of 83 km s−1 ) we estimate the dynamical age ofthe outflowing material (3500 years), its momentum ( 104 M km s−1 ) and its kinetic energy ( 1048−49 erg). The morphology
and kinematics presented by the filaments suggest the presence of a dispersal outflow with explosive characteristics in IRAS
16076-5134. In addition, we make a raw estimate of the lower limit of the frequency rate of the explosive dispersal outflows
in the Galaxy (one every 110 years) considering constant star formation rate and efficiency with respect to the galactocentric
radius of the Galaxy. This may imply a comparable rate of dispersal outflows and supernovae (approximately one every 50
years), which may be important for the energy budget of the Interstellar Medium and the link between dispersal outflows andhigh-mass star formation.

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6. Turbulence and Accretion: a High-resolution Study of the B5 Filaments

Michael Chun-Yuan Chen, James Di Francesco, Jaime E. Pineda, Stella S. Offner, Rachel K. Friesen F Highresolution observations of the Perseus B5 "core" have previously revealed that this subsonic region actually consists of several
filaments that are likely in the process of forming a quadruple stellar system. Since subsonic filaments are thought to be
produced at the ∼ 0.1 pc sonic scale by turbulent compression, a detailed kinematic study is crucial to test such a scenario in
the context of core and star formation. Here we present a detailed kinematic follow-up study of the B5 filaments at a 0.009
pc resolution using the VLA and GBT combined observations fitted with multi-component spectral models. Using precisely
identified filament spines, we find a remarkable resemblance between the averaged width profiles of each filament and Plummerlike functions, with filaments possessing FWHM widths of ∼ 0.03 pc. The velocity dispersion profiles of the filaments also show
decreasing trends towards the filament spines. Moreover, the velocity gradient field in B5 appears to be locally well ordered(∼ 0.04 pc) but globally complex, with kinematic behaviors suggestive of inhomogeneous turbulent accretion onto filaments andlongitudinal flows towards a local overdensity along one of the filaments.

the role of the giant planet instability in terrestrial planet formation models
7. Rethinking
Matthew S. Clement, Rogerio Deienno, Andre Izidoro F Advances in computing power and numerical methodologies
over the past several decades sparked a prolific output of dynamical investigations of the late stages of terrestrial planet formation.
Among other peculiar inner solar system qualities, the ability of simulations to reproduce the small mass of Mars within theplanets’ geochemically inferred accretion timescale of <10 Myr after the appearance of calcium aluminum-rich inclusions (CAIs)
is arguably considered the gold standard for judging evolutionary hypotheses. At present, a number of independent models
are capable of consistently generating Mars-like planets and simultaneously satisfying various important observational andgeochemical constraints. However, all models must still account for the effects of the epoch of giant planet migration andorbital instability; an event which dynamical and cosmochemical constraints indicate occurred within the first 100 Myr after
nebular gas dispersal. If the instability occurred in the first few Myr of this window, the disturbance might have affected thebulk of Mars’ growth. In this manuscript, we turn our attention to a scenario where the instability took place after t=50 Myr.
Specifically, we simulate the instability’s effects on three nearly-assembled terrestrial systems that were generated via previous
embryo accretion models and contain three large proto-planets with orbits interior to a collection of Mars-mass embryos anddebris. While the instability consistently triggers a Moon-forming impact and efficiently removes excessive material from theMars-region in our models, we find that our final systems are too dynamically excited and devoid of Mars and Mercury analogs.
Thus, we conclude that, while possible, our scenario is far more improbable than one where the instability either occurredearlier, or at a time where Earth and Venus’ orbits were far less dynamically excited.

8. Turbulence in outer protoplanetary disks: MRI or VSI?

Can Cui, Xue-Ning Bai F The outer protoplanetary disks (PPDs) can be subject to the magnetorotational instability (MRI)
and the vertical shear instability (VSI). While both processes can drive turbulence in the disk, existing numerical simulations
have studied them separately. In this paper, we conduct global 3D non-ideal magnetohydrodynamic (MHD) simulations forouter PPDs with ambipolar diffusion and instantaneous cooling, and hence conductive to both instabilities. Given the rangeof ambipolar Elsässer numbers (Am) explored, it is found that the VSI turbulence dominates over the MRI when ambipolar
diffusion is strong (Am = 0.1); the VSI and MRI can co-exist for Am = 1; and the VSI is overwhelmed by the MRI when
ambipolar diffusion is weak (Am = 10). Angular momentum transport process is primarily driven by MHD winds, while
viscous accretion due to MRI and/or VSI turbulence makes a moderate contribution in most cases. Spontaneous magnetic flux
concentration and formation of annular substructures remain robust in strong ambipolar diffusion dominated disks (Am ≤ 1)with the presence of the VSI. Ambipolar diffusion is the major contributor to the magnetic flux concentration phenomenon
rather than advection.

Population of Dipper Stars from the Transiting Exoplanet Survey Satellite Mission
9. A
Benjamin K. Capistrant, Melinda Soares-Furtado, Andrew Vanderburg, Marina Kounkel, Saul A. Rappaport,
Mark Omohundro, Brian P. Powell, Robert Gagliano, Thomas Jacobs, Veselin B. Kostov, Martti H. Kristiansen, Daryll M. LaCourse, Allan R. Schmitt, Hans Martin Schwengeler, Ivan A. Terentev F Dipper stars area classification of young stellar objects that exhibit dimming variability in their light curves, dropping in brightness by 10-50%,
likely induced by occultations due to circumstellar disk material. This variability can be periodic, quasi-periodic, or aperiodic.
Dipper stars have been discovered in young stellar associations via ground-based and space-based photometric surveys. We
present the detection and characterization of the largest collection of dipper stars to date: 293 dipper stars, including 234 newdipper candidates. We have produced a catalog of these targets, which also includes young stellar variables that exhibit predominately bursting-like variability and symmetric variability (equal parts bursting and dipping). The total number of catalog
sources is 414. These variable sources were found in a visual survey of TESS light curves, where dipping-like variability wasobserved. We found a typical age among our dipper sources of <5 Myr, with the age distribution peaking at 2 Myr, and a tailof the distribution extending to ages older than 20 Myr. Regardless of the age, our dipper candidates tend to exhibit infrared4

excess, which is indicative of the presence of disks. TESS is now observing the ecliptic plane, which is rich in young stellar
associations, so we anticipate many more discoveries in the TESS dataset. A larger sample of dipper stars would enhance thecensus statistics of light curve morphologies and dipper ages.

10. Complex Organic Molecules Formation in Cold Cores on Stochastically Heated Grains
Long-Fei Chen, Qiang Chang, Yao Wang, Di Li F We investigate the roles of stochastic grain heating in the formation ofcomplex organic molecules (COMs) in cold cores, where COMs have been detected. Two different types of grain-size distributions
are used in the chemical models. The first one is the MRN distribution, and the second one considers grain coagulation to
study its effects on the chemical evolution in these environments. The macroscopic Monte Carlo method is used to perform thetwo-phase chemical model simulations. We find that (1) grain coagulation can affect certain gas-phase species, such as CO2
and N2 H+ , in the cold core environments, which can be attributed to the volatile precursors originating from the small grains
with temperature fluctuations; (2) grains with radii around 4.6 × 10−3 µm contribute most to the production of COMs on dust
grains under cold core conditions, while few species can be formed on even smaller grains with radii less than 2 × 10−3 µm; (3)COMs formed on stochastically heated grains could help explain the observed abundances of gas-phase COMs in cold cores.

11. CHEMOUT: CHEMical complexity in star-forming regions of the OUTer Galaxy III.
Nitrogen isotopic ratios in the outer Galaxy

L. Colzi, D. Romano, F. Fontani, V. M. Rivilla, L. Bizzocchi, M. T. Beltrán, P. Caselli, D. Elia, L. Magrini F
Nitrogen isotopic ratios are a key tool for tracing Galactic stellar nucleosynthesis. We present the first study of the 14 N/15 Nabundance ratio in the outer regions of the Milky Way (namely, for galactocentric distances, RGC , from 12 kpc up to 19 kpc),
with the aim to study the stellar nucleosynthesis effects in the global Galactic trend. We analysed IRAM 30m observations
towards a sample of 35 sources in the context of the CHEMical complexity in star-forming regions of the OUTer Galaxy(CHEMOUT) project. We derived the 14 N/15 N ratios from HCN and HNC for 14 and 3 sources, respectively, using the J = 1-0
rotational transition of HN13 C, H15 NC, H13 CN, and HC15 N. The results found in the outer Galaxy have been combined withprevious measurements obtained in the inner Galaxy. We find an overall linear decreasing H13 CN/HC15 N ratio with increasing
RGC . This translates to a parabolic 14 N/15 N ratio with a peak at 11 kpc. Updated Galactic chemical evolution models havebeen taken into account and compared with the observations. The parabolic trend of the 14 N/15 N ratio with RGC can benaturally explained (i) by a model that assumes novae as the main 15 N producers on long timescales (≥1 Gyr) and (ii) by
updated stellar yields for low- and intermediate-mass stars.

Great Planetary Heist: Theft and capture in star-forming regions
12. TheEmma C. Daffern-Powell, Richard J. Parker, Sascha P. Quanz F Gravitational interactions in star-forming regions
are capable of disrupting and destroying planetary systems, as well as creating new ones. In particular, a planet can be stolen,
where it is directly exchanged between passing stars during an interaction; or captured, where a planet is first ejected from its
birth system and is free-floating for a period of time, before being captured by a passing star. We perform sets of direct N-bodysimulations of young, substructured star-forming regions, and follow their evolution for 10 Myr in order to determine how many
planets are stolen and captured, and their respective orbital properties. We show that in high density star-forming regions,stolen and captured planets have distinct properties. The semimajor axis distribution of captured planets is significantly skewed
to wider orbits compared to the semimajor axis distribution of stolen planets and planets that are still orbiting their parent
star (preserved planets). However, the eccentricity and inclination distributions of captured and stolen planets are similar, but
in turn very different to the inclination and eccentricity distributions of preserved planets. In low-density star-forming regions
these differences are not as distinct but could still, in principle, be used to determine whether observed exoplanets have likely
formed in situ or have been stolen or captured. We find that the initial degree of spatial and kinematic substructure in astar-forming region is as important a factor as the stellar density in determining whether a planetary system will be altered,disrupted, captured or stolen.

13. Thermophysical evolution of planetesimals in the Primordial Disk

Björn J. R. Davidsson F The Primordial Disk of small icy planetesimals, once located at 15-30 AU from the Sun, wasdisrupted by giant planet migration in the early Solar System. The Primordial Disk thereby became the source region of objects
in the current-day Kuiper Belt, Scattered Disk, and Oort Cloud. I present the thermophysics code "Numerical Icy Minor Body
evolUtion Simulator", or NIMBUS, and use it to study the thermophysical evolution of planetesimals in the Primordial Diskprior to its disruption. Such modelling is mandatory in order to understand the behaviour of dynamically new comets from theOort Cloud, as well as the activity of Centaurs and short-period comets from the Scattered Disk, that return pre-processed to
the vicinity of the Sun. I find that bodies in the midst of the Primordial Disk with diameters ranging 4-200 km lost all their
CO ice on time-scales of order 0.1-10 Myr depending on size, through a combination of protosolar and long-lived radionuclide
heating. CO and other hypervolatiles therefore require a less volatile host for their storage. I consider two possible hosts:

5

amorphous water ice and CO2 ice. Because of the high luminosity of the protosun, some Primordial Disk bodies may havesustained significant crystallisation, CO:CO2 segregation, and CO2 sublimation in the uppermost few tens of meters. I discuss
how this may affect coma abundance ratios and distant activity in dynamically new comets.

formation of clusters and OB associations in different density spiral arm environ14. The
ments
C. L. Dobbs, T. J. R. Bending, A. R. Pettitt, A. S. M. Buckner, M. R. Bate F We present simulations of theformation and evolution of clusters in spiral arms. The simulations follow two different spiral arm regions, and the total gas
mass is varied to produce a range of different mass clusters. We find that including photoionizing feedback produces the observed
cluster mass radius relation, increasing the radii of clusters compared to without feedback. Supernovae have little impact oncluster properties. We find that in our high density, high gas mass simulations, star formation is less affected by feedback, asstar formation occurs rapidly before feedback has much impact. In our lowest gas density simulation, the resulting clusters arecompletely different (e.g. the number of clusters and their masses) to the case with no feedback. The star formation rate isalso significantly suppressed. The fraction of stars in clusters in this model decreases with time flattening at about 20%. In
our lowest gas simulation model, we see the formation of a star forming group with properties similar to an OB association, inparticular similar to Orion Ia. We suggest that low densities, and stronger initial dynamics are conducive to forming associations
rather than clusters. In all models cluster formation is complex with clusters merging and splitting. The most massive clusters
which form have tended to undergo more mergers.

Accretion Burst Echoes as Probes of Protostellar Environments and Episodic Mass

15. Assembly

Logan Francis, Doug Johnstone, Jeong-Eun Lee, Gregory J. Herczeg, Feng Long, Steve Mairs, Carlos ContrerasPeña, Gerald Moriarty-Schieven F Protostars likely accrete material at a highly time variable rate, however, measurementsof accretion variability from the youngest protostars are rare, as they are still deeply embedded within their envelopes. Submm/mm observations can trace the thermal response of dust in the envelope to accretion luminosity changes, allowing variationsin the accretion rate to be quantified. In this paper, we present contemporaneous sub-mm/mm light curves of variable protostars
in Serpens Main, as observed by the ALMA ACA, SMA, and JCMT. The most recent outburst of EC 53 (V371 Ser), an ∼ 18
month periodic variable, is well-sampled in the SMA and JCMT observations. The SMA light curve of EC 53 is observed topeak weeks earlier and exhibit a stronger amplitude than at the JCMT. Stochastic variations in the ACA observations aredetected for SMM 10 IR with a factor ∼ 2 greater amplitude than as seen by the JCMT. We develop a toy model of theenvelope response to accretion outbursts to show EC 53’s light curves are plausibly explained by the delay associated with thelight travel time across the envelope and the additional dilution of the JCMT response by the incorporation of cold envelopematerial in the beam. The larger JCMT beam can also wash out the response to rapid variations, which may be occurring for
SMM 10 IR. Our work thus provides a valuable proof of concept for the usage of sub-mm/mm observations as a probe of boththe underlying accretion luminosity variations and the protostellar environment.

and extinction variations in the low-mass pre-main sequence binary system
16. Accretion
WX ChaEleonora Fiorellino, Gabriella Zsidi, Agnes Kospal, Peter Abraham, Attila Bodi, Gaitee Hussain, Carlo F.
Manara, Andras Pal F Light curves of young star systems show photometric variability due to different kinematic, andphysical processes. One of the main contributors to the photometric variability is the changing mass accretion rate, which
regulates the interplay between the forming young star and the protoplanetary disk. We collected high-resolution spectroscopy
in eight different epochs, as well as ground-based and space-borne multi-epoch optical and infrared photometry of WX Cha,an M0 binary system, with an almost edge-on disk (i = 87degrees) in the Chamaeleon I star-forming region. Spectroscopic
observations cover 72 days, the ground-based optical monitoring covers 42 days while space-borne TESS photometry extends for
56 days. The multi-wavelength light curves exhibit quasi-periodic variability of 0.35 - 0.53 mag in the near-infrared, and of 1.3
mag in g band. We studied the variability of selected emission lines that trace the accretion, computed the accretion luminosity
and the mass accretion rate using empirical relations and obtained values of the accretion luminosity between 1.6 and 3.2 Lsunand mass accretion rate between 3.31x10−7 Msun/yr and 7.76x10−7 Msun/yr. Our results show that WX Cha is accreting at a
rate larger than what is typical for T Tauri stars in the same star-forming region with the same stellar parameters. We theorizethat this is due to the higher disk mass of WX Cha than what is usual for stars with similar stellar mass, and to the binary
nature of the system. Daily changes in the accretion luminosity and in the extinction can explain the photometric variability.

617. The relation between the Mass Accretion Rate and the Disk Mass in Class I Protostars
Eleonora Fiorellino, Lukasz Tychoniec, Carlo F. Manara, Giovanni Rosotti, Simone Antoniucci, Fernando
Cruz-Saenz de Miera, Agnes Kospal, Brunella Nisini F The evidence of a relation between the mass accretion rate andthe disk mass is established for young, Class II pre-main sequence stars. This observational result opened an avenue to test
theoretical models and constrain the initial conditions of the disk formation, fundamental in the understanding of the emergenceof planetary systems. However, it is becoming clear that the planet formation starts even before the Class II stage, in disks
around Class 0 and I protostars. We show for the first time evidence for a correlation between the mass accretion rate and thedisk mass for a large sample of Class I young stars located in nearby (< 500 pc) star-forming regions. We fit our sample, findingthat the Class I objects relation has a slope flatter than Class II stars, and have higher mass accretion rates and disk masses.
The results are put in context of the disk evolution models.

degrees of nitrogen and carbon depletion in the warm molecular layers of
18. Different
protoplanetary disks
Kenji Furuya, Seokho Lee, Hideko Nomura F Observations have revealed that the elemental abundances of carbon andoxygen in the warm molecular layers of some protoplanetary disks are depleted compared to those is the interstellar medium bya factor of 10-100. Meanwhile, little is known about nitrogen. To investigate the time evolution of nitrogen, carbon, and oxygen
elemental abundances in disks, we develop a one-dimensional model that incorporates dust settling, turbulent diffusion of dust
and ices, as well as gas-ice chemistry including the chemistry driven by stellar UV/X-rays and the galactic cosmic rays. We findthat gaseous CO in the warm molecular layer is converted to CO2 ice and locked up near the midplane via the combinationof turbulent mixing (i.e., the vertical cold finger effect) and ice chemistry driven by stellar UV photons. On the other hand,gaseous N2, the main nitrogen reservoir in the warm molecular layer, is less processed by ice chemistry, and exists as it is. Thenthe nitrogen depletion occurs solely by the vertical cold finger effect of N2. As the binding energy of N2 is lower than that of
CO and CO2, the degree of nitrogen depletion is smaller than that of carbon and oxygen depletion, leading to higher elemental
abundance of nitrogen than that of carbon and oxygen. This evolution occurs within 1 Myr and proceeds further, when the αparameter for the diffusion coefficient is 0.001. Consequently, the N2H+/CO column density ratio increases with time. How
the vertical transport affects the midplane ice composition is briefly discussed.

The JCMT BISTRO Survey: Multi-wavelength polarimetry of bright regions in NGC

19. 2071 in the far-infrared/submillimetre range, with POL-2 and HAWC+

L. Fanciullo, F. Kemper, K. Pattle, P. M. Koch, S. Sadavoy, S. Coudé, A. Soam, T. Hoang, T. Onaka, V. J.
M. Le Gouellec, D. Arzoumanian, D. Berry, C. Eswaraiah, E. J. Chung, R. Furuya, C. L. H. Hull, J. Hwang,
D. Johnstone, J. -h. Kang, K. H. Kim, F. Kirchschlager, V. Könyves, J. Kwon, W. Kwon, S. -P. Lai, C. W.
Lee, T. Liu, A. -R. Lyo, I. Stephens, M. Tamura, X. Tang, D. Ward-Thompson, A. Whitworth, H. Shinnaga F
Polarized dust emission is a key tracer in the study of interstellar medium and of star formation. The observed polarization,
however, is a product of magnetic field structure, dust grain properties and grain alignment efficiency, as well as their variationsin the line of sight, making it difficult to interpret polarization unambiguously. The comparison of polarimetry at multiple
wavelengths is a possible way of mitigating this problem. We use data from HAWC+/SOFIA and from SCUBA-2/POL-2(from the BISTRO survey) to analyse the NGC 2071 molecular cloud at 154, 214 and 850 µm. The polarization angle changes
significantly with wavelength over part of NGC 2071, suggesting a change in magnetic field morphology on the line of sightas each wavelength best traces different dust populations. Other possible explanations are the existence of more than one
polarization mechanism in the cloud or scattering from very large grains. The observed change of polarization fraction withwavelength, and the 214-to-154 µm polarization ratio in particular, are difficult to reproduce with current dust models under
the assumption of uniform alignment efficiency. We also show that the standard procedure of using monochromatic intensity
as a proxy for column density may produce spurious results at HAWC+ wavelengths. Using both long-wavelength (POL-2, 850µm) and short-wavelength (HAWC+, . 200 µm) polarimetry is key in obtaining these results. This study clearly shows theimportance of multi-wavelength polarimetry at submillimeter bands to understand the dust properties of molecular clouds andthe relationship between magnetic field and star formation.

20. GIARPS High-resolution Observations of T Tauri stars (GHOsT). IV. Accretion properties of the Taurus-Auriga young association

M. Gangi, S. Antoniucci, K. Biazzo, A. Frasca, B. Nisini, J. M. Alcalà, T. Giannini, C. F. Manara, A. Giunta,
A. Harutyunyan, U. Munari, F. Vitali F In the framework of the GIARPS@TNG High-resolution Observations of T Tauristars (GHOsT) project, we study the accretion properties of 37 Classical T Tauri Stars of the Taurus-Auriga star forming region(SFR) with the aim of characterizing their relation with the properties of the central star, of jets and disk winds, and of the
global disk structure, in synergy with complementary ALMA millimiter observations. We derive stellar parameters, optical veiling, accretion luminosity (Lacc ) and mass accretion rate (Ṁacc ) in a homogeneous and self-consistent way using high-resolution

7

spectra acquired at the Telescopio Nazionale Galileo with the HARPS-N and GIANO spectrographs, and flux-calibrated basedon contemporaneous low-resolution spectroscopic and photometric ancillary observations. The Lacc -L? , Ṁacc -M? and Ṁacc -Mdisk
relationships of the Taurus sample are provided and compared with those of the coeval SFRs of Lupus and Chamaeleon I. Our
results demonstrate the potential of contemporaneous optical and near-infrared high-resolution spectroscopy to simultaneously
provide precise measurements of stellar and accretion/wind properties of young stars.

21. Nonlinear evolution of streaming instabilities in accreting protoplanetary disks

Chun-Yen Hsu, Min-Kai Lin F The streaming instability (SI) is one of the most promising candidates for triggering
planetesimal formation by producing dense dust clumps that undergo gravitational collapse. Understanding how the SI operates
in realistic protoplanetary disks (PPDs) is therefore crucial to assess the efficiency of planetesimal formation. Modern models
of PPDs show that large-scale magnetic torques or winds can drive laminar gas accretion near the disk midplane. In a previous
study, we identified a new linear dust-gas instability, the azimuthal drift SI (AdSI), applicable to such accreting disks and is
powered by the relative azimuthal motion between dust and gas that results from the gas being torqued. In this work, we
present the first nonlinear simulations of the AdSI. We show that it can destabilize an accreting, dusty disk even in the absenceof a global radial pressure gradient, which is unlike the classic SI. We find the AdSI drives turbulence and the formation ofvertically-extended dust filaments that undergo merging. In dust-rich disks, merged AdSI filaments reach maximum dust-to-gas
ratios exceeding 100. Moreover, we find that even in dust-poor disks the AdSI can increase local dust densities by two orders ofmagnitude. We discuss the possible role of the AdSI in planetesimal formation, especially in regions of an accreting PPD withvanishing radial pressure gradients.

hydrogen clock to infer the upper stellar mass
22. TheErin R. Higgins, Jorick S. Vink, Gautham N. Sabhahit, Andreas A. C. Sander F The most massive stars dominate
the chemical enrichment, mechanical and radiative feedback, and energy budget of their host environments. Yet how massive
stars initially form and how they evolve throughout their lives is ambiguous. The mass loss of the most massive stars remains a
key unknown in stellar physics, with consequences for stellar feedback and populations. In this work, we compare grids of very
massive star (VMS) models with masses ranging from 80-1000Msun, for a range of input physics. We include enhanced winds
close to the Eddington limit as a comparison to standard O-star winds, with consequences for present-day observations of 50100Msun stars. We probe the relevant surface H abundances (Xs) to determine the key traits of VMS evolution compared to O
stars. We find fundamental differences in the behaviour of our models with the enhanced-wind prescription, with a convergenceon the stellar mass at 1.6 Myr, regardless of the initial mass. It turns out that Xs is an important tool in deciphering the initial
mass due to the chemically homogeneous nature of VMS above a mass threshold. We use Xs to break the degeneracy of theinitial masses of both components of a detached binary, and a sample of WNh stars in the Tarantula nebula. We find thatfor some objects, the initial masses are unrestricted and, as such, even initial masses of the order 1000Msun are not excluded.
Coupled with the mass turnover at 1.6 Myr, Xs can be used as a ’clock’ to determine the upper stellar mass.

23. ALMA Datacubes and Continuum Maps of the Irradiated Western Wall in Carina

Patrick Hartigan, Maxwell Hummel, Andrea Isella, Turlough Downes F We present ALMA observations of thecontinuum and line emission of 12 CO, 13 CO, C18 O, and [C I] for a portion of the G287.38-0.62 (Car 1-E) region in the Carina
star-forming complex. The new data record how a molecular cloud responds on subarcsecond scales when subjected to a powerfulradiation front, and provide insights into the overall process of star formation within regions that contain the most massive
young stars. The maps show several molecular clouds superpose upon the line of sight, including a portion of the Western Wall,a highly-irradiated cloud situated near the young star cluster Trumpler 14. In agreement with theory, there is a clear progression
from fluoresced H2 , to [C I], to C18 O with distance into the PDR front. Emission from optically thick 12 CO extends across theregion, while 13 CO, [C I] and especially C18 O are more optically thin, and concentrate into clumps and filaments closer to the
PDR interface. Within the Western Wall cloud itself we identify 254 distinct core-sized clumps in our datacube of C18 O. The
mass distribution of these objects is similar to that of the stellar IMF. Aside from a large-scale velocity gradient, the clump
radial velocities lack any spatial coherence size. There is no direct evidence for triggering of star formation in the Western Wallin that its C18 O clumps and continuum cores appear starless, with no pillars present. However, the densest portion of the cloudlies closest to the PDR, and the C18 O emission is flattened along the radiation front.

gap at 1 au in the disk of DI Cha A revealed by infrared interferometry
24. A
Tímea Juhász, Péter Ábrahám, Attila Moór, Lei Chen, Ágnes Kóspál, József Varga, Zsolt Regály, Gabriella
Zsidi, András Pál F DI Cha A is K0-type pre-main sequence star, the brightest component of a quadruple stellar system.
Here we report on a detailed study of this star based on archival VLTI/MIDI and VLTI/PIONIER infrared interferometricobservations, as well as optical–infrared photometric monitoring from ground-based and space-born instruments. We determined the structure of the circumstellar disk by fitting simultaneously the interferometric visibilities and the spectral energy

8distribution, using both analytical models and the radiative transfer code RADMC-3D. The modeling revealed that the radial
density distribution of the disk appears to have a gap between 0.21 and 3.0 au. The inner ring, whose inner size coincides
with the sublimation radius, is devoid of small, submicrometer-sized dust grains. The inner edge of the outer disk features
a puffed-up rim, typically seen in intermediate-mass stars. Grain growth, although less progressed, was also detected in theouter disk. The inner ring is variable at mid-infrared wavelengths on both daily and annual timescales, while the star stays
remarkably constant in the optical, pointing to geometrical or accretion changes in the disk as possible explanation for the flux
variations.

Confirmation of a Population of Isolated, Intermediate-Mass YSOs
25. Spectroscopic
Michael A. Kuhn, Ramzi Saber, Matthew S. Povich, Rafael S. de Souza, Alberto Krone-Martins, Emille E. O.
Ishida, Catherine Zucker, Robert A. Benjamin, Lynne A. Hillenbrand, Alfred Castro-Ginard, Xingyu Zhou F
Wide-field searches for young stellar objects (YSOs) can place useful constraints on the prevalence of clustered versus distributed
star formation. The Spitzer/IRAC Candidate YSO (SPICY) catalog is one of the largest compilations of such objects ( 120,000
candidates in the Galactic midplane). Many SPICY candidates are spatially clustered, but, perhaps surprisingly, approximately
half the candidates appear spatially distributed. To better characterize this unexpected population and confirm its nature, we
obtained Palomar/DBSP spectroscopy for 26 of the optically-bright (G<15 mag) "isolated" YSO candidates. We confirm the
YSO classifications of all 26 sources based on their positions on the Hertzsprung-Russell diagram, H and Ca II line-emission
from over half the sample, and robust detection of infrared excesses. This implies a contamination rate of <10% for SPICY stars
that meet our optical selection criteria. Spectral types range from B4 to K3, with A-type stars most common. Spectral energy
distributions, diffuse interstellar bands, and Galactic extinction maps indicate moderate to high extinction. Stellar masses range
from 1 to 7 M , and the estimated accretion rates, ranging from 3 × 10−8 to 3 × 10−7 M yr−1 , are typical for YSOs in thismass range. The 3D spatial distribution of these stars, based on Gaia astrometry, reveals that the "isolated" YSOs are not
evenly distributed in the Solar neighborhood but are concentrated in kpc-scale dusty Galactic structures that also contain the
majority of the SPICY YSO clusters. Thus, the processes that produce large Galactic star-forming structures may yield nearly
as many distributed as clustered YSOs.

26. MHD simulations of dense core collision

Shinichi W. Kinoshita, Fumitaka Nakamura F We investigated the effect of magnetic fields on the collision process
between dense molecular cores. We performed three-dimensional magnetohydrodynamic simulations of collisions between two
self-gravitating cores using the Enzo adaptive mesh refinement code. The core was modeled as a stable isothermal Bonnor-Ebert(BE) sphere immersed in uniform magnetic fields. Collisions were characterized by the offset parameter b, Mach number of theinitial core M, magnetic field strength B0 , and angle θ between the initial magnetic field and collision axis. For head-on (b = 0)collisions, one protostar was formed in the compressed layer. The higher the magnetic field strength, the lower the accretion
rate. For models with b = 0 and θ = 90◦ , the accretion rate was more dependent on the initial magnetic field strength comparedwith b = 0 and θ = 0◦ models. For off-center (b = 1) collisions, the higher specific angular momentum increased; therefore, thegas motion was complicated. In models with b = 1 and M = 1, the number of protostars and gas motion highly depended on
B0 and θ. For models with b = 1 and M = 3, no significant shock-compressed layer was formed and star formation was not
triggered.

27. Primordial Dusty Rings and Episodic Outbursts in Protoplanetary Discs

Kundan Kadam, Eduard Vorobyov, Shantanu Basu F We investigate the formation and evolution of "primordial" dusty
rings occurring in the inner regions of protoplanetary discs, with the help of long-term, coupled dust-gas, magnetohydrodynamic
simulations. The simulations are global and start from the collapse phase of the parent cloud core, while the dead zone iscalculated via an adaptive α formulation by taking into account the local ionization balance. The evolution of the dusty
component includes its growth and back reaction on to the gas. Previously, using simulations with only a gas component, we
showed that dynamical rings form at the inner edge of the dead zone. We find that when dust evolution as well as magnetic
field evolution in the flux-freezing limit are included, the dusty rings formed are more numerous and span a larger radial extent
in the inner disc, while the dead zone is more robust and persists for a much longer time. We show that these dynamicalrings concentrate enough dust mass to become streaming unstable, which should result in rapid planetesimal formation evenin the embedded phases of the system. The episodic outbursts caused by the magnetorotational instability have significant
impact on the evolution of the rings. The outbursts drain the inner disc of grown dust, however, the period between bursts issufficiently long for the planetesimal growth via streaming instability.The dust mass contained within the rings is large enoughto ultimately produce planetary systems with the core accretion scenario. The low mass systems rarely undergo outbursts andthus, the conditions around such stars can be especially conducive for planet formation.

9

young stellar objects in the Local Group spiral galaxy M33 identified using
28. Massive
machine learning
David A. Kinson, Joana M. Oliveira, Jacco Th. van Loon F We present a supervised machine learning classificationof stellar populations in the Local Group spiral galaxy M 33. The Probabilistic Random Forest (PRF) methodology, previously
applied to populations in NGC 6822, utilises both near and far-IR classification features. It classifies sources into nine target
classes: young stellar objects (YSOs), oxygen- and carbon-rich asymptotic giant branch stars, red giant branch and red supergiant stars, active galactic nuclei, blue stars (e.g. O-, B- and A-type main sequence stars), Wolf-Rayet stars and Galactic
foreground stars. Across 100 classification runs the PRF classified 162,746 sources with an average estimated accuracy of∼ 86 per cent, based on confusion matrices. We identified 4985 YSOs across the disk of M 33, applying a density-based clustering
analysis to identify 68 star forming regions (SFRs) primarily in the galaxy’s spiral arms. SFR counterparts to known H ii regions
were recovered, with ∼ 91 per cent of SFRs spatially coincident with giant molecular clouds identified in the literature. Using
photometric measurements, as well as SFRs in NGC 6822 with an established evolutionary sequence as a benchmark, we
employed a novel approach combining ratios of [Hα]/[24µm] and [250µm]/[500µm] to estimate the relative evolutionary statusof all M 33 SFRs. Masses were estimated for each YSO ranging from 6 − 27 M . Using these masses, we estimate star formation
rates based on direct YSO counts of 0.63 M yr−1 in M 33’s SFRs, 0.79 ± 0.16 M yr−1 in its centre and 1.42 ± 0.16 M yr−1
globally.

Role of Filamentary Structures in the Formation of Two Dense Cores, L1544 and L694-2

29. Shinyoung Kim, Chang Won Lee, Mario Tafalla, Maheswar Gophinathan, Paola Caselli, Philip C. Myers, Eun

Jung Chung, Shanghuo Li F We present mapping results of two prestellar cores, L1544 and L694-2, embedded in filamentary
clouds in C18 O (3-2), 13 CO (3-2), 12 CO (3-2), HCO+ (4-3), and H13 CO+ (4-3) with the JCMT telescope to examine the roleof the filamentary structures in the formation of dense cores in the clouds, with new distance estimates for L1544 (175+4−3 pc)and L694-2 (203+6
pc).
From
these
observations,
we
found
that
the
non-thermalvelocity
dispersionoftwoprestellar
cores−7
and their surrounding clouds are smaller than or comparable to the sound speed. This may indicate that the turbulence has
already been dissipated for both filaments and cores during their formation time. We also found a λ/4 shift between the periodic
oscillations in the velocity and the column density distributions implying the possible presence of gravitational core-forming
flow motion along the axis of the filament. The mass accretion rates due to these flow motions are estimated to be 2-3 M
Myr−1 , being comparable to that for Serpens cloud but much smaller than those for the Hub filaments, cluster, or high mass
forming filaments by 1 or 2 order of magnitudes. From this study, we suggest that the filaments in our targets might be formed
from the shock-compression of colliding clouds, and then the cores are formed by gravitational fragmentation of the filaments
to evolve to the prestellar stage. We conclude that the filamentary structures in the clouds play an important role in the entire
process of formation of dense cores and their evolution.

30. Isolated Massive Star Formation in G28.20-0.05

Chi-Yan Law, Jonathan C. Tan, Prasanta Gorai, Yichen Zhang, Rubén Fedriani, Daniel Tafoya, Kei Tanaka,
Giuliana Cosentino, Yao-Lun Yang, Diego Mardones, Maria Teresa Beltrán, Guido Garay F We report highresolution 1.3 mm continuum and molecular line observations of the massive protostar G28.20-0.05 with ALMA. The continuum
image reveals a ring-like structure with 2,000 au radius, similar to morphology seen in archival 1.3 cm VLA observations. Basedon its spectral index and associated H30α emission, this structure mainly traces ionised gas. However, there is evidence for∼ 30 M of dusty gas near the main mm continuum peak on one side of the ring, as well as in adjacent regions within 3,000 au.
A virial analysis on scales of ∼2,000 au from hot core line emission yields a dynamical mass of ∼ 80 M . A strong velocity
gradient in the H30α emission is evidence for a rotating, ionized disk wind, which drives a larger-scale molecular outflow. An
infrared SED analysis indicates a current protostellar mass of m∗ ∼ 40 M forming from a core with initial mass Mc ∼ 300 M
in a clump with mass surface density of Σcl ∼ 0.8 g cm−2 . Thus the SED and other properties of the system can be understoodin the context of core accretion models. Structure-finding analysis on the larger-scale continuum image indicates G28.20-0.05
is forming in a relatively isolated environment, with no other concentrated sources, i.e., protostellar cores, above ∼ 1 M foundfrom ∼0.1 to 0.4 pc around the source. This implies that a massive star can form in relative isolation and the dearth of otherprotostellar companions within the ∼ 1 pc environs is a strong constraint on massive star formation theories that predict thepresence of a surrounding protocluster.

FUor-like Sources: The Parameter Space of Viscously Heated Disks in the
31. Diagnosing
Optical and Near-IR
Hanpu Liu, Gregory J. Herczeg, Doug Johnstone, Carlos Contreras-Peña, Jeong-Eun Lee, Haifeng Yang,
Xingyu Zhou, Sung-Yong Yoon, Ho-Gyu Lee, Masanobu Kunitomo, Jessy Jose F FU Ori type objects (FUors)
are decades-long outbursts of accretion onto young stars that are strong enough to viscously heat disks so that the disk
outshines the central star. We construct models for FUor objects by calculating emission components from a steady-stateviscous accretion disk, a passively-heated dusty disk, magnetospheric accretion columns, and the stellar photosphere. We

10explore the parameter space of the accretion rate and stellar mass to investigate implications on the optical and near-infrared
spectral energy distribution and spectral lines. The models are validated by fitting to multi-wavelength photometry of three
confirmed FUor objects, FU Ori, V883 Ori and HBC 722 and then comparing the predicted spectrum to observed opticaland infrared spectra. The brightness ratio between the viscous disk and the stellar photosphere, η, provides an important
guide for identifying viscous accretion disks, with η = 1 ("transition line") and η = 5 ("sufficient dominance line") marking
turning points in diagnostics, evaluated here in the near-infrared. These turning points indicate the emergence and complete
development of FUor-characteristic strong CO absorption, weak metallic absorption, the triangular spectral continuum shapein the H-band, and location in color-magnitude diagrams. Lower stellar mass M∗ and higher accretion rate Ṁ lead to larger η;for M∗ = 0.3 M , η = 1 corresponds to Ṁ = 2 × 10−7 M /yr and η = 5 to Ṁ = 6 × 10−7 M /yr. The sufficient dominance line
also coincides with the expected accretion rate where accreting material directly reaches the star. We discuss implications of
the models on extinction diagnostics, FUor brightening timescales, viscous disks during initial protostellar growth, and eruptive
young stellar objects (YSO) associated with FUors.

32. On The Unusual Variability of 2MASS J06195260-2903592: A Long-Lived Disk arounda Young Ultracool Dwarf

Michael C. Liu, Eugene A. Magnier, Eric Gaidos, Trent J. Dupuy, Pengyu Liu, Beth A. Biller, Johanna M.
Vos, Katelyn N. Allers, Jason T. Hinkle, Benjamin J. Shappee, Sage N. L. Constantinou, Mitchell T. Dennis,
Kenji S. Emerson F We present the characterization of the low-gravity M6 dwarf 2MASS J0619-2903 previously identified
as an unusual field object based on its strong IR excess and variable near-IR spectrum. Multiple epochs of low-resolution(R 150) near-IR spectra show large-amplitude ( 0.1-0.5 mag) continuum variations on timescales of days to 12 years, unlike thesmall-amplitude variability typical for field ultracool dwarfs. The variations between epochs are well-modeled as changes in therelative extinction (∆AV ≈ 2 mag). Likewise, Pan-STARRS optical photometry varies on timescales as long as 11 years (andpossibly as short as an hour) and implies similar amplitude AV changes. NEOWISE mid-IR light curves also suggest changes
on 6-month timescales, with amplitudes consistent with the optical/near-IR extinction variations. However, near-IR spectra,near-IR photometry, and optical photometry obtained in the past year indicate the source can also be stable on hourly andmonthly timescales. From comparison to objects of similar spectral type, the total extinction of 2MASS J0619-2903 seems to be
AV ≈ 4 − 6 mag, with perhaps epochs of lower extinction. Gaia EDR3 finds that 2MASS J0619-2903 has a wide-separation (1.2’+0.04= 10450 AU) stellar companion, with an isochronal age of 31+22−10 Myr and a mass of 0.30−0.03 Msun. Adopting this companion’s
age and EDR3 distance (145.2±0.6 pc), we estimate a mass of 0.11-0.17 Msun for 2MASS J0619-2903. Altogether, 2MASS
J0619-2903 appears to possess an unusually long-lived primordial circumstellar disk, perhaps making it a more obscured analog
to the "Peter Pan" disks found around a few M dwarfs in nearby young moving groups.

33. ALMA Detection of Dust Trapping around Lagrangian Points in the LkCa 15 Disk

Feng Long, Sean M. Andrews, Shangjia Zhang, Chunhua Qi, Myriam Benisty, Stefano Facchini, Andrea Isella,David J. Wilner, Jaehan Bae, Jane Huang, Ryan A. Loomis, Karin I. Öberg, Zhaohuan Zhu F We present
deep high-resolution (∼50 mas, 8 au) ALMA 0.88 and 1.3 mm continuum observations of the LkCa 15 disk. The emission
morphology shows an inner cavity and three dust rings at both wavelengths, but with slightly narrower rings at the longer
wavelength. Along a faint ring at 42 au, we identify two excess emission features at ∼10σ significance at both wavelengths: oneas an unresolved clump and the other as an extended arc, separated by roughly 120 degrees in azimuth. The clump is unlikely
to be a circumplanetary disk (CPD) as the emission peak shifts between the two wavelengths even after accounting for orbital
motion. Instead, the morphology of the 42 au ring strongly resembles the characteristic horseshoe orbit produced in planet–diskinteraction models, where the clump and the arc trace dust accumulation around Lagrangian points L4 and L5 , respectively.
The shape of the 42 au ring, dust trapping in the outer adjacent ring, and the coincidence of the horseshoe ring location witha gap in near-IR scattered light, are all consistent with the scenario of planet sculpting, with the planet likely having a mass
between those of Neptune and Saturn. We do not detect point-like emission associated with a CPD around the putative planet
location (0.00 27 in projected separation from the central star at a position angle of ∼60 deg), with upper limits of 70 and 33 µJy
at 0.88 and 1.3 mm, respectively, corresponding to dust mass upper limits of 0.02–0.03 M⊕ .

BFS 10: A nascent bipolar H II region in a filamentary molecular cloud

34. Nicholas Larose, C. R. Kerton F We present a study of the compact blister HII region BFS 10 and its highly filamentary
molecular cloud. We utilize 12CO observations from the Five College Radio Astronomy Observatory to determine the distance,
size, mass, and velocity structure of the molecular cloud. Infrared observations obtained from the UKIRT Infrared Deep Sky
Survey and the Spitzer Infrared Array Camera, as well as radio continuum observations from the Canadian Galactic Plane
Survey, are used to extract information about the central HII region. This includes properties such as the ionizing photon rateand infrared luminosity, as well as identifying a rich embedded star cluster associated with the central O9 V star. Time-scales
regarding the expansion rate of the HII region and lifetime of the ionizing star reveal a high likelihood that BFS 10 will develop
into a bipolar HII region. Although the region is expected to become bipolar, we conclude from the clouds velocity structure11that there is no evidence to support the idea that star formation at the location of BFS 10 was triggered by two colliding clouds.
A search for embedded young stellar objects (YSOs) within the molecular cloud was performed. Two distinct regions of YSOs
were identified; one region associated with the rich embedded cluster and another sparse group associated with an intermediate
mass YSO.

The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). VII:

35. Chemistry of Embedded Dense Cores

Shanghuo Li, Patricio Sanhueza, Xing Lu, Chang Won Lee, Qizhou Zhang, Stefano Bovino, Giovanni Sabatini,
Tie Liu, Kee-Tae Kim, Kaho Morii, Daniel Tafoya, Ken’ichi Tatematsu, Takeshi Sakai, Junzhi Wang, Fei Li,
Andrea Silva, Natsuko Izumi, David Allingham F We present a study of chemistry toward 294 dense cores in 12 molecular
clumps using the data obtained from the ALMA Survey of 70 µm dark High-mass clumps in Early Stages (ASHES). We identified
97 protostellar cores and 197 prestellar core candidates based on the detection of outflows and molecular transitions of highupper energy levels (Eu /k > 45 K). The detection rate of the N2 D+ emission toward the protostellar cores is 38%, which ishigher than 9% for the prestellar cores, indicating that N2 D+ does not exclusively trace prestellar cores. The detection rates of
the DCO+ emission are 35% for the prestellar cores and 49% for the protostellar cores, which are higher than those of N2 D+ ,implying that DCO+ appears more frequently than N2 D+ in both prestellar and protostellar cores. Both N2 D+ and DCO+
abundances appear to decrease from the prestellar to protostellar stage. The DCN, C2 D and 13 CS emission lines are rarely
seen in the dense cores of early evolutionary phases. The detection rate of the H2 CO emission toward dense cores is 52%, threetimes higher than that of CH3 OH (17%). In addition, the H2 CO detection rate, abundance, line intensities, and line widths
increase with the core evolutionary status, suggesting that the H2 CO line emission is sensitive to protostellar activity.

evolution of protoplanetary disc radii and disc masses in star-forming regions
36. TheBridget Marchington, Richard J. Parker F Protoplanetary discs are crucial to understanding how planets form and evolve,
but these objects are subject to the vagaries of the birth environments of their host stars. In particular, photoionising radiationfrom massive stars has been shown to be an effective agent in disrupting protoplanetary discs. External photoevaporation leads
to the inward evolution of the radii of discs, whereas the internal viscous evolution of the disc causes the radii to evolve outwards.
We couple N-body simulations of star-forming regions with a post-processing analysis of disc evolution to determine how theradius and mass distributions of protoplanetary discs evolve in young star-forming regions. To be consistent with observations,
we find that the initial disc radii must be of order 100au, even though these discs are readily destroyed by photoevaporationfrom massive stars. Furthermore, the observed disc radii distribution in the Orion Nebula Cluster is more consistent withmoderate initial stellar densities (100M pc−3 ), in tension with dynamical models that posit much higher inital densities for
the ONC. Furthermore, we cannot reproduce the observed disc radius distribution in the Lupus star-forming region if its discs
are subject to external photoevaporation. A more detailed comparison is not possible due to the well-documented uncertainties
in determining the ages of pre-main sequence (disc-hosting) stars.

Recent progress with observations and models to characterize the magnetic fields from37. star-forming cores to protostellar disksAnaëlle Maury, Patrick Hennebelle, Josep Miquel Girart F In this review paper, we aim at providing a global outlook
on the progresses made in the recent years to characterize the role of magnetic fields during the embedded phases of the starformation process. Thanks to the development of observational capabilities and the parallel progress in numerical models
capturing most of the important physics at work during star formation, it has recently become possible to confront detailed
predictions of magnetized models to observational properties of the youngest protostars. We provide an overview of the mostimportant consequences when adding magnetic fields to state-of-the-art models of protostellar formation, emphasizing their role
to shape the resulting star(s) and their disk(s). We discuss the importance of magnetic field coupling to set the efficiency ofmagnetic processes, and provide a review of observational works putting constraints on the two main agents responsible forthe coupling in star-forming cores: dust grains and ionized gas. We recall the physical processes and observational methods
allowing to trace the magnetic field topology and its intensity in embedded protostars, and review the main steps, success andlimitations in comparing real observations to synthetic observations from the non-ideal MHD models. Finally, we discuss themain threads of observational evidence that suggest a key role of magnetic fields for star and disk formation, and propose ascenario solving the angular momentum for star formation, also highlighting the remaining tensions that exist between models
and observations.

12imaging of the filamentary infrared dark clouds G1.75-0.08 and G11.36+0.80:
38. ArTéMiS
Dust-based physical properties of the clouds and their clumps
Oskari Miettinen, Michael Mattern, Philippe André F We imaged the infrared dark clouds (IRDCs) G1.75-0.08 andG11.36+0.80 at 350 µm and 450 µm using the ArTéMiS bolometer. These data were used in conjunction with our previous
870 µm observations with the Large APEX BOlometer CAmera (LABOCA). The clumps in G11.36+0.80 were also observedin the N2 H+ (1 − 0) transition with the IRAM 30-metre telescope. G1.75-0.08 was found to be composed of two cold (∼ 14.5K), massive (several ∼ 103 M ) clumps that are projectively separated by ∼ 3.7 pc. Both clumps are 70 µm dark, but they
do not appear to be bounded by self-gravity. The G1.75-0.08 filament was found to be subcritical by a factor of ∼ 14 withrespect to its critical line mass. G11.36+0.80 was found to be moderately (by a factor of ∼ 2) supercritical and composed offour clumps. The dust temperatures of the clumps are ∼ 13 − 15 K, and their masses are in the range ∼ 232 − 633 M . All theclumps are gravitationally bound. The projected, average separation of the clumps is ∼ 1 pc. A configuration that is observedin G1.75-0.08, namely two clumps at the ends of the filament, could be the result of gravitational focussing acting along thecloud. The two clumps fulfil the mass-radius threshold for high-mass star formation. Owing to the location of G1.75-0.08 near
the Galactic centre (∼ 270 pc), environmental effects such as a high level of turbulence, tidal forces, and shearing motions could
affect the cloud dynamics. The observed clump separation in G11.36+0.80 can be understood in terms of a sausage instability.
The G11.36+0.80 clumps do not lie above the mass-radius threshold for high-mass star formation. The substructure observedin one of the clumps in G11.36+0.80 suggests that the IRDC has fragmented in a hierarchical fashion. This conforms to thefilamentary paradigm for Galactic star formation.

millimeter-multiwavelength continuum study of VLA 1623 West
39. A
Arnaud Michel, Sarah I. Sadavoy, Patrick D. Sheehan, Leslie W. Looney, Erin G. Cox F VLA 1623 West is an
ambiguous source that has been described as a shocked cloudlet as well as a protostellar disk. We use deep ALMA 1.3 and0.87 millimeter observations to constrain its shape and structure to determine its origins better. We use a series of geometricmodels to fit the uv visibilities at both wavelengths with GALARIO. Although the Real visibilities show structures similar
to what has been identified as gaps and rings in protoplanetary disks, we find that a modified Flat-Topped Gaussian at highinclination provides the best fit to the observations. This fit agrees well with expectations for an optically thick, highly inclined
disk. Nevertheless, we find that the geometric models consistently yield positive residuals at the four corners of the disk at both
wavelengths. We interpret these residuals as evidence that the disk is flared in the millimeter dust. We use a simple toy model
for an edge-on flared disk and find that the residuals best match a disk with flaring that is mainly restricted to the outer disk
at R & 30 au. Thus, VLA 1623W may represent a young protostellar disk where the large dust grains have not yet had enoughtime to settle into the mid-plane. This result may have implications for how disk evolution and vertical dust settling impact
the initial conditions leading to planet formation.

of a magnetohydrodynamic disk wind traced by water maser observations
40. Snapshot
Luca Moscadelli, Alberto Sanna, Henrik Beuther, André Oliva, Rolf Kuiper F The formation of astrophysicalobjects of different nature and size, from black holes to gaseous giant planets, involves a disk-jet system, where the disk
drives the mass accretion onto a central compact object and the jet is a fast collimated ejection along the disk rotation axis.
Magnetohydrodynamic disk winds can provide the link between mass accretion and ejection, which is essential to ensure thatthe excess angular momentum is removed from the system and accretion onto the central object can proceed. However, up tonow, we have been lacking direct observational proof of disk winds. This work presents a direct view of the velocity field of a disk
wind around a forming massive star. Achieving a very high spatial resolution of 0.05 au, our water maser observations trace thevelocities of individual streamlines emerging from the disk orbiting the forming star. We find that, at low elevation above thedisk midplane, the flow co-rotates with its launch point in the disk, in agreement with magneto-centrifugal acceleration where thegas is flung away along the magnetic field line anchored to the disk. Beyond the co-rotation point, the flow rises spiraling aroundthe disk rotation axis along a helical magnetic field. We have performed (resistive-radiative-gravito-) magnetohydrodynamic
simulations of the formation of a massive star and record the development of a magneto-centrifugally launched jet presenting
many properties in agreement with our observations.

kilomasers pinpoint supermassive stars?
41. Could
Katarzyna Nowak, Martin. G. H. Krause, Daniel Schaerer F A strong nuclear kilomaser, W1, has been found in the
nearby galaxy NGC 253, associated with a forming super star cluster. Kilomasers could arise from the accretion disc aroundsupermassive stars (> 103 Msun), hypothetical objects that have been proposed as polluters responsible for the chemical
peculiarities in globular clusters. The supermassive stars would form via runaway collisions, simultaneously with the cluster.
Their discs are perturbed by stellar flybys, inspiralling and colliding stars. This raises the question if an accretion disc would at
all be able to survive in such a dynamic environment and mase water lines. We investigated what the predicted maser spectrumof such a disc would look like using 2D hydrodynamic simulations and compared this to the W1 kilomaser. We derived model
maser spectra from the simulations by using a general maser model for appropriate disc temperatures. All our model discs

13

survived. The model maser spectra for the most destructive case for the simulations of M = 1000 Msun are a reasonable matchwith the W1 kilomaser spectrum in terms of scaling, flux values and some of the signal trends. Details in the spectrum suggestthat a star of a few 1000 Msun might fit even better, with 10,000 Msun clearly giving too large velocities. Our investigations
thus support the hypothesis that kilomasers could pinpoint supermassive stars.

Star Formation in the Young SMC Region NGC 602: Insights from ALMA
42. Sequential
Theo J. O’Neill, Remy Indebetouw, Karin Sandstrom, Alberto D. Bolatto, Katherine E. Jameson, Lynn R.
Carlson, Molly K. Finn, Margaret Meixner, Elena Sabbi, Marta Sewilo F NGC 602 is a young, low-metallicity starcluster in the "Wing" of the Small Magellanic Cloud. We reveal the recent evolutionary past of the cluster through analysis
of high-resolution (∼0.4 pc) Atacama Large Millimeter/submillimeter Array observations of molecular gas in the associated
HII region N90. We identify 110 molecular clumps (R < 0.8 pc) traced by CO emission, and study the relationship between
the clumps and associated young stellar objects (YSOs) and pre-main-sequence (PMS) stars. The clumps have high virial
parameters (typical αvir = 4-11) and may retain signatures of a collision in the last .8 Myr between HI components of theadjacent supergiant shell SMC-SGS 1. We obtain a CO-bright-to-H2 gas conversion factor of XCO,B = (3.4 ± 0.2) × 1020
cm−2 (K km s−1 )−1 , and correct observed clump properties for CO-dark H2 gas to derive a total molecular gas mass in N90
of 16, 600 ± 2, 400 M . We derive a recent (. 1 Myr) star formation rate of 130 ± 30 M Myr−1 with an efficiency of 8 ±3% assessed through comparing total YSO mass to total molecular gas mass. Very few significant radial trends exist between
clump properties or PMS star ages and distance from NGC 602. We do not find evidence for a triggered star formation scenario
among the youngest (.2 Myr) stellar generations, and instead conclude that a sequential star formation process in which NGC
602 did not directly cause recent star formation in the region is likely.

Depletion of gaseous CO in protoplanetary disks by surface-energy-regulated ice forma-

43. tion

Diana Powell, Peter Gao, Ruth Murray-Clay, Xi Zhang F Empirical constraints of fundamental properties of protoplanetary disks are essential for understanding planet formation and planetary properties (1,2). Carbon monoxide (CO) gas isoften used to constrain disk properties (3). However, estimates show that the CO gas abundance in disks is depleted relative to
expected values (4,5,6,7), and models of various disk processes impacting the CO abundance could not explain this depletionon observed 1Myr timescales (8,9,10,11,12,13,14). Here we demonstrate that surface energy effects on particles in disks, suchas the Kelvin effect, that arise when ice heterogeneously nucleates onto an existing particle can efficiently trap CO in its ice
phase. In previous ice formation models, CO gas was released when small ice-coated particles were lofted to warmed disk layers.
Our model can reproduce the observed abundance, distribution and time evolution of gaseous CO in the four most studied
protoplanetary disks (7). We constrain the solid and gaseous CO inventory at the midplane and disk diffusivities and resolveinconsistencies in estimates of the disk mass – three crucial parameters that control planetary formation.

Binding Energies of Interstellar Relevant S-bearing Species on Water Ice Mantles: A

44. Quantum Mechanical Investigation

J. Perrero, J. Enrique-Romero, S. Ferrero, C. Ceccarelli, L. Podio, C. Codella, A. Rimola, P. Ugliengo F Binding
energies (BEs) are one of the most important parameters for astrochemical modeling determining, because they govern whether
a species stays in the gas-phase or is frozen on the grain surfaces. It is currently known that, in the denser and colder regions of
the interstellar medium, sulphur is severely depleted in the gas phase. It has been suggested that it may be locked into the grain
icy mantles. However, which are the main sulphur carriers is still a matter of debate. This work aims at establishing accurate
BEs of 17 sulphur-containing species on two validated water ice structural models, the proton-ordered crystalline (010) surface
and an amorphous water ice surface. We adopted Density Functional Theory (DFT)-based methods (the hybrid B3LYP-D3(BJ)
and the hybrid meta-GGA M06-2X functionals) to predict structures and energetics of the adsorption complexes. London’sdispersion interactions are shown to be crucial for an accurate estimate of the BEs due to the presence of the high polarizable
sulphur element. While on the crystalline model the adsorption is restricted to a very limited number of binding sites with single
valued BEs, on the amorphous model several adsorption structures are predicted, giving a BE distribution for each species. With
the exception of few cases, both experimental and other computational data are in agreement with our calculated BE values. A
final discussion on how useful the computed BEs are with respect to the snow lines of the same species in protoplanetary disks
is provided

14

Jet from the enigmatic high-latitude star BP Psc and evolutionary status of its driving

45. source

I. S. Potravnov, M. Yu. Khovritchev, S. A. Artemenko, D. N. Shakhovskoy F BP Psc is an active late-type (sp:G9)
star with unclear evolutionary status lying at high galactic latitude b = −57◦ . It is also the source of the well collimated bipolarjet. We present results of the proper motion and radial velocity study of BP Psc outflow based on the archival Hα imaging with
the GMOS camera at 8.1-m Gemini-North telescope as well as recent imaging and long-slit spectroscopy with the SCORPIO
multi-mode focal reducer at 6-m BTA telescope of SAO RAS. The 3D kinematics of the jet revealed the full spatial velocity
up to ∼140 km·s−1 and allows us to estimate the distance to BP Psc system as D = 135 ± 40 pc. This distance leads toan estimation of the central source luminosity L∗ ≈ 1.2L , indicating that it is the ≈1.3M T Tauri star with an age t . 7
Myr. We measured the electron density of order Ne ∼ 102 cm−3 and mean ionization fraction f ≈ 0.04 within the jet knots
and estimated upper limit of the mass-loss rate in NE lobe as Ṁout ≈ 1.2 · 10−8 M · yr−1 . The physical characteristics of theoutflow are typical for the low-excitation YSO jets and consistent with the magnetocentrifugal mechanism of its launching andcollimation. Prominent wiggling pattern revealed in Hα images allowed us to suppose the existence of a secondary substellar
companion in a non-coplanar orbit and estimate its most plausible mass as Mp ≈ 30MJup . We conclude that BP Psc is one of
the closest to the Sun young jet-driving systems and its origin is possibly related to the episode of star formation triggered byexpanding supershells in Second Galactic quadrant.

46.

Star and Cluster Formation in the Sh2-112 Filamentary Cloud Complex
Alik Panja, Yan Sun, Wen Ping Chen, Soumen Mondal F We present the star formation activity around the emission
nebula Sh2-112. At a distance of ∼ 2.1 kpc, this ion H2 complex, itself 3 pc in radius, is illuminated by the massive star (O8 V)
BD+45 3216. The associated molecular cloud extends in angular scales of 2.0 × 0.83, corresponding to linear sizes of 73 pc by
30 pc, along the Galactic longitude. The high-resolution (30 arcsec) extinction map reveals a chain of dust clumps aligned withthe filament-like structure with an average extinction of AV ∼ 2.78 mag, varying up to a maximum of ∼ 17 mag. Our analysis
led to identification of a rich population (∼ 500) of young (average age of ∼ 1 Myr) stars, plus a numerous number (∼ 350) of Hαemitters, spatially correlated with the filamentary clouds. Located near the edge of the cloud, the luminous star BD+45 3216
has created an arc-like pattern as the ionizing radiation encounters the dense gas, forming a blister-shaped morphology. We
found three distinct young stellar groups, all coincident with relatively dense parts of the cloud complex, signifying ongoingstar formation. Moreover, the cloud filament (excitation temperature ∼ 10 K) traced by the CO isotopologues and extending
nearly ∼ 80 pc is devoid of ionized gas except at the dense cores (excitation temperature ∼ 28–32 K) wherein significant ionizedemission excited by OB stars (dynamical age ∼ 0.18–1.0 Myr) pertains. The radial velocity is dynamic (median ∼ −3.65 km s−1 )along the main filament, increasing from Galactic east to west, features mass flow to form the massive stars/clusters at thecentral hubs.

BEASTies: dynamical formation of planetary systems around massive stars
47. Making
Richard J. Parker, Emma C. Daffern-Powell F Exoplanets display incredible diversity, from planetary system architectures around Sun-like stars that are very different to our Solar System, to planets orbiting post-main sequence stars or stellar
remnants. Recently the B-star Exoplanet Abundance STudy (BEAST) reported the discovery of at least two super-Jovian
planets orbiting massive stars in the Sco Cen OB association. Whilst such massive stars do have Keplerian discs, it is hard toenvisage gas giant planets being able to form in such hostile environments. We use N-body simulations of star-forming regions
to show that these systems can instead form from the capture of a free-floating planet, or the direct theft of a planet from one
star to another, more massive star. We find that this occurs on average once in the first 10Myr of an association’s evolution,and that the semimajor axes of the hitherto confirmed BEAST planets (290 and 556au) are more consistent with capture thantheft. Our results lend further credence to the notion that planets on more distant (>100au) orbits may not be orbiting theirparent star.

of a brown dwarf with quasi-spherical mass-loss
48. Discovery
Dary A. Ruíz-Rodríguez, Lucas A. Cieza, Simon Casassus, Victor Almendros-Abad, Paula Jofré, Koraljka
Muzic, Karla Peña Ramirez, Grace Batalla-Falcon, Michael M. Dunham, Camilo González-Ruilova, Antonio
Hales, Elizabeth Humphreys, Pedro H. Nogueira, Claudia Paladini, John Tobin, Jonathan P. Williams, Alice
Zurlo F We report the serendipitous discovery of an elliptical shell of CO associated with the faint stellar object SSTc2d
J163134.1-24006 as part of the "Ophiuchus Disk Survey Employing ALMA" (ODISEA), a project aiming to study the entire
population of protoplanetary disks in the Ophiuchus Molecular Cloud from 230 GHz continuum emission and 12 CO (J=2-1),
13
CO (J=2-1) and C18 CO (J=2-1) lines readable in Band-6. Remarkably, we detect a bright 12 CO elliptical shape emission of∼ 3” × 4” towards SSTc2d J163134.1-24006 without a 230 GHz continuum detection. Based on the observed near-IR spectrum
taken with the Very Large Telescope (KMOS), the brightness of the source, its 3-dimensional motion, and Galactic dynamic
arguments, we conclude that the source is not a giant star in the distant background (>5 - 10 kpc) and is most likely to be ayoung brown dwarf in the Ophiuchus cloud, at a distance of just ∼139 pc. This is the first report of quasi-spherical mass loss15

in a young brown dwarf. We suggest that the observed shell could be associated with a thermal pulse produced by the fusionof deuterium, which is not yet well understood, but for a sub-stellar object is expected to occur during a short period of timeat an age of a few Myr, in agreement with the ages of the objects in the region. Other more exotic scenarios, such as a merger
with planetary companions, cannot be ruled out from the current observations.

49. Dynamics of young stellar clusters as planet forming environments

Megan Reiter, Richalsrd J. Parker F Most stars and thus most planetary systems do not form in isolation. The larger
star-forming environment affects protoplanetary disks in multiple ways: gravitational interactions with other stars truncate
disks and alter the architectures of exoplanet systems; external irradiation from nearby high-mass stars truncates disks andshortens their lifetimes; and remaining gas and dust in the environment affects dynamical evolution (if removed by feedback
processes) and provides some shielding for disks from external irradiation. The dynamical evolution of the region regulates whenand how long various feedback mechanisms impact protoplanetary disks. Density is a key parameter that regulates the intensityand duration of UV irradiation and the frequency of dynamical encounters. The evolution of larger star-forming complexes
may also play an important role by mixing populations. Observations suggest that clusters are not a single-age population but
multiple populations with small age differences which may be key to resolving several timescale issues (i.e., proplyd lifetimes,enrichment). In this review, we consider stellar clusters as the ecosystems in which most stars and therefore most planets form.
We review recent observational and theoretical results and highlight upcoming contributions from facilities expected to begin
observations in the next five years. Looking further ahead, we argue that the next frontier is large-scale surveys of low-massstars in more distant high-mass star-forming regions. The future of ecosystem studies is bright as faint low-mass stars in moredistant high-mass star-forming regions will be routinely observable in the era of Extremely Large Telescopes (ELTs).

Planet Formation. VII. Astrochemical Models of Protoplanetary Disks and
50. Inside-Out
Implications for Planetary Compositions
Arturo Cevallos Soto, Jonathan C. Tan, Xiao Hu, Chia-Jung Hsu, Catherine Walsh F Inside-Out Planet Formation(IOPF) proposes that the abundant systems of close-in Super-Earths and Mini-Neptunes form in situ at the pressure maximum
associated with the Dead Zone Inner Boundary (DZIB). We present a model of physical and chemical evolution of protoplanetary
disk midplanes that follows gas advection, radial drift of pebbles and gas-grain chemistry to predict abundances from 300 au
down to the DZIB near 0.2 au. We consider typical disk properties relevant for IOPF, i.e., accretion rates 1E-9 < dM/dt /(Msun/yr) < 1E-8 and viscosity parameter alpha = 1E-4, and evolve for fiducial duration of t = 1E5 years. For outer, cool disk
regions, we find that C and up to 90% of O nuclei start locked in CO and O2 ice, which keeps abundances of CO2 and H2O one
order of magnitude lower. Radial drift of icy pebbles is influential, with gas-phase abundances of volatiles enhanced up to twoorders of magnitude at ice-lines, while the outer disk becomes depleted of dust. Disks with decreasing accretion rates graduallycool, which draws in icelines closer to the star. At < 1 au, advective models yield water-rich gas with C/O ratios < 0.1, which
may be inherited by atmospheres of planets forming here via IOPF. For planetary interiors built by pebble accretion, IOPF
predicts volatile-poor compositions. However, advectively-enhanced volatile mass fractions of 10% can occur at the water ice
line.

51. Molecular Fraction in the Galactic Center: The Central Molecular and HI Zones
Yoshiaki Sofue F By mapping the molecular fraction of the Galactic Center (GC), we quantitatively address the question of
how much molecular and central the CMZ (Central Molecular Zone) is. For this purpose we analyze the CO and HI-line archivalρΣand fmol, which are the ratio of column-massdata, and determine the column- (surface-) and volume-molecular fractions, fmol
density of H2 projected on the sky to that of total gas (H2 + HI) from the line intensities, and the ratio of volume-mass densitiesΣof H2 to total gas from the brightness temperature, respectively. It is shown that fmol
is as high as ∼ 0.9 − 0.95 in the CMZ, andρfmol
is 0.93 − 0.98 in the GC Arms I and II attaining the highest value of ∼ 0.98 toward Sgr B2. The expanding molecular ringΣΣ
(EMR, or the parallelogram) has a slightly smaller fmol
as ∼ 0.9 − 0.93. We define the CMZ as the region with fmol
≥ 0.8 − 0.9◦◦
between the shoulders of plateau-like distribution of H2 column density from l = −1 .1 to +1 .8 having Gaussian vertical
distribution with a half thickness of ±0◦ .2. The CMZ is embedded in the Central HI Zone (CHZ), which is defined as an HI
disc between l ∼ −2◦ and +2◦ .5, b = −0◦ .5 and +0◦ .5. Based on the analysis, we discuss the origin of CMZ and interstellarρΣ
physics such as the volume filling factors of molecular and HI gases inferred from the difference between fmoland fmol.

A novel pipeline for detection and characterization of close-in faint compan52. StraKLIP:
ions through Karhunen-Loêve Image Processing algorithm
Giovanni M. Strampelli, Laurent Pueyo, Jonathan Aguilar, Antonio Aparicio, Gaspard Duchêne, Massimo
Robberto F We present a new pipeline developed to detect and characterize faint astronomical companions at small angularseparation from the host star using sets of wide-field imaging observations not specifically designed for High Contrast Imaging
analysis. The core of the pipeline relies on Karhunen-Loêve truncated transformation of the reference PSF library to perform16

PSF subtraction and identify candidates. Tests of reliability of detections and characterization of companions are made throughsimulation of binaries and generation of Receiver Operating Characteristic curves for false positive/true positive analysis. The
algorithm has been successfully tested on large HST/ACS and WFC3 datasets acquired for two HST Treasury Programs on theOrion Nebula Cluster. Based on these extensive numerical experiments we find that, despite being based on methods designed
for observations of single star at a time, our pipeline performs very well on mosaic space based data. In fact, we are able todetect brown dwarf-mass companions almost down to the planetary mass limit. The pipeline is able to reliably detect signals
at separations as close as & 0.1” with a completeness of & 10%, or ∼ 0.2” with a completeness of ∼ 30%. This approach
can potentially be applied to a wide variety of space based imaging surveys, starting with data in the existing HST archive,near-future JWST mosaics, and future wide-field Roman images.

53. Rogue planets and brown dwarfs: Predicting the populations of free-floating planetary
mass objects observable with JWST

Aleks Scholz, Koraljka Muzic, Ray Jayawardhana, Lyra Quinlan, James Wurster F Free-floating (or rogue) planets
are planets that are liberated (or ejected) from their host systems. Although simulations predict their existence in substantial
numbers, direct observational evidence for free-floating planets with masses below 5 MJup is still lacking. Several cycle-1
observing programs with JWST aim to hunt for them in four different star-forming clusters. These surveys are designed to besensitive to masses of 1-15 MJup (assuming a hot-start formation), which corresponds to spectral types of early L to late T
for the ages of these clusters. If the existing simulations are not wide off the mark, we show here that the planned programs
are likely to find up to 10-20 giant rogue planets in moderate density clusters like NGC1333 or IC348, and several dozen to
100 in high-density regions like NGC2024 and the Orion Nebula Cluster. These numbers correspond to 1-5% of the totalcluster population; they could be substantially higher if stars form multiple giant planets at birth. In contrast, the number offree-floating brown dwarfs, formed from core collapse ("like stars") is expected to be significantly lower, only about 0.25numberof stars, or 1-7 for the clusters considered here. Below 10 MJup that number drops further by an order of magnitude. We also
show that the planned surveys are not at risk of being significantly contaminated by field brown dwarfs in the foreground or
background, after spectroscopic confirmation. Taken together, our results imply that if a population of L and T dwarfs were to
be found in these JWST surveys, it is expected to be predominantly made up of rogue planets.

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

54. Fragmentation and multi-scale gas kinematics in protoclusters G12.42+0.50 and G19.880.53

Anindya Saha, Anandmayee Tej, Hong-Li Liu, Tie Liu, Namitha Issac, Chang Won Lee, Guido Garay, Paul F.
Goldsmith, Mika Juvela, Sheng-Li Qin, Amelia Stutz, Shanghuo Li, Ke Wang, Tapas Baug, Leonardo Bronfman,Feng-Wei Xu, Yong Zhang, Chakali Eswaraiah F We present new continuum and molecular line data from the ALMA
Three-millimeter Observations of Massive Star-forming regions (ATOMS) survey for the two protoclusters, G12.42+0.50 andG19.88-0.53. The 3 mm continuum maps reveal seven cores in each of the two globally contracting protoclusters. These coressatisfy the radius-mass relation and the surface mass density criteria for high-mass star formation. Similar to their natal
clumps, the virial analysis of the cores suggests that they are undergoing gravitational collapse (αvir << 2). The clump tocore scale fragmentation is investigated and the derived core masses and separations are found to be consistent with thermal
Jeans fragmentation. We detect large-scale filamentary structures with velocity gradients and multiple outflows in both regions.
Dendrogram analysis of the H13 CO+ map identifies several branch and leaf structures with sizes ∼ 0.1 and 0.03 pc, respectively.
The supersonic gas motion displayed by the branch structures is in agreement with the Larson power-law indicating that thegas kinematics at this spatial scale is driven by turbulence. The transition to transonic/subsonic gas motion is seen to occur at
spatial scales of ∼0.1 pc indicating the dissipation of turbulence. In agreement with this, the leaf structures reveal gas motions
that deviate from the slope of Larson’s law. From the large-scale converging filaments to the collapsing cores, the gas dynamics
in G12.42+0.50 and G19.88-0.53 show scale-dependent dominance of turbulence and gravity and the combination of these two
driving mechanisms needs to be invoked to explain massive star formation in the protoclusters.

55. Core orientations and magnetic fields in isolated molecular clouds

Ekta Sharma, Maheswar Gopinathan, Archana Soam, Chang Won Lee, T. R. Seshadri F Molecular clouds are sitesof star formation. Magnetic fields are believed to play an important role in their dynamics and shaping morphology. We aim
to study any possible correlation that might exist between the magnetic fields orientation inside the clouds and the magnetic
fields at envelope scales and their connection with respect to the observed morphology of the selected clouds. We examine
the magnetic field orientation towards the clouds L1512, L1523, L1333, L1521E, L1544, L1517, L1780, and L183 using opticaland Planck polarization observations. We also found the correlation between the ambient magnetic field and core orientations
derived using Astrodendrogram on the Herschel 250 µm data. We find that the magnetic fields derived from optical and Planck
agree with each other. The derived magnetic fields are aligned along the observed emission of each cloud as seen in Herschel
250 µm data. We also find that the relative orientation between the cores and the magnetic fields is random. This lack of17

correlation may arise due to the fact that the core orientation could also be influenced by the different magnetization within
individual clouds at higher densities or the feedback effects which may vary from cloud to cloud. The estimated magnetic fieldstrength and the mass-to-flux ratio suggest that all the clouds are in a magnetically critical state except L1333, L1521E, andL183 where the cloud envelope could be strongly supported by the magnetic field lines.

Bird’s eye view of molecular clouds in the Milky Way: II. Cloud kinematics from sub-pc

56. to kpc scales

Andri Spilker, Jouni Kainulainen, Jan Orkisz F The kinematics of molecular gas are crucial for setting the stage for starformation. One key question related to the kinematic properties of gas is how they depend on the spatial scale. We aim to
describe the CO spectra, velocity dispersions, and especially the linewidth-size relation, of molecular gas from cloud (parsec-)scales to kiloparsec scales in a complete region within the Milky Way disk. We utilise the census of molecular clouds within 2 kpc
from our earlier work, together with CO emission data for them from the literature. We study the kinematics and the Larson’s
relations for the sample of individual clouds. We also mimic a face-on view of the Milky Way and analyse the kinematics ofthe clouds within apertures of 0.25-2 kpc in size. In this way, we describe the scale-dependency of the CO gas kinematics
and Larson’s relations. We describe the spectra of CO gas at cloud scales and in apertures between 0.25-2 kpc in our survey
area. The spectra within the apertures are relatively symmetric but show non-Gaussian high-velocity wings. At cloud-scales,
our sample shows a linewidth-size relation σv = 1.5 × R0.3±0.1 with a large scatter. The mass-size relation in the sample ofclouds is MCO = 794× R1.5±0.5 . The relations are also present for the apertures at kpc-scales. A suggestive dependency on
galactic environment is seen, with apertures closer to the Galactic centre and the Sagittarius spiral arm having slightly higher
velocity dispersions. We explore the possible effect of a diffuse component in the survey area, and find that such a component
would widen the CO spectra and could flatten the linewidth-size relation. Understanding the nature of the possible diffuse COcomponent and its effects on observations is crucial for connecting Galactic and extragalactic data.

57. The imprint of star formation on stellar pulsations

Thomas Steindl, Konstanze Zwintz, Eduard Vorobyov F In the earliest phases of their evolution, stars gain mass throughthe acquisition of matter from their birth clouds. The widely accepted classical concept of early stellar evolution neglects thedetails of this accretion phase and assumes the formation of stars with large initial radii that contract gravitationally. In thispicture, the common idea is that once the stars begin their fusion processes, they have forgotten their past. By analysing stellar
oscillations in recently born stars, we show that the accretion history leaves a potentially detectable imprint on the stars’ interior
structures. Currently available data from space would allow discriminating between these more realistic accretion scenarios andthe classical early stellar evolution models. This opens a window to investigate the interior structures of young pulsating stars
that will also be of relevance for related fields, such as stellar oscillations in general and exoplanet studies.

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Scattered

58. light detection of a possible disk wind in RY Tau

P. -G. Valegård, C. Ginski, C. Dominik, J. Bae, M. Benisty, T. Birnstiel, S. Facchini, A. Garufi, M. Hogerheijde,
R. G. van Holstein, M. Langlois, C. F. Manara, P. Pinilla, Ch. Rab, Á. Ribas, L. B. F. M. Waters, J. Williams F
Disk winds are an important mechanism for accretion and disk evolution around young stars. The accreting intermediate-mass
T-Tauri star RY Tau has an active jet and a previously known disk wind. Archival optical and new near-infrared observations of
the RY Tau system show two horn-like components stretching out as a cone from RY Tau. Scattered light from the disk around
RY Tau is visible in near-infrared but not seen at optical wavelengths. In the near-infrared, dark wedges that separates the horns
from the disk, indicating we may see the scattered light from a disk wind. We use archived ALMA and SPHERE/ZIMPOL
I-band observations combined with newly acquired SPEHRE/IRDIS H-band observations and available literature to build a
simple geometric model of the RY Tau disk and disk wind. We use Monte Carlo radiative transfer modelling MCMax3D to createcomparable synthetic observations that test the effect of a dusty wind on the optical effect in the observations. We constrain thegrain size and dust mass needed in the disk wind to reproduce the effect from the observations. A model geometrically reminiscentof a dusty disk wind with small micron to sub-micron size grains elevated above the disk can reproduce the optical effect seen in
the observations. The mass in the obscuring component of the wind has been constrained to 1 × 10−9 M ≤ M ≤ 5 × 10−8 M
which corresponds to a lower limit mass loss rate in the wind of about ∼ 1 × 10−8 M yr−1 . While an illuminate dust cavity
cannot be ruled out without measurements of the gas velocity, we argue that a magnetically launched disk wind is the most
likely scenario.

18

Physical properties of accretion shocks toward the Class I protostellar system Oph-IRS

59. 44

E. Artur de la Villarmois, V. V. Guzmán, J. K. Jørgensen, L. E. Kristensen, E. A. Bergin, D. Harsono, N.
Sakai, E. F. van Dishoeck, S. Yamamoto F (Abridged) Physical processes such as accretion shocks are thought to becommon in the protostellar phase, where the envelope component is still present, and they can release molecules from the dust to
the gas phase, altering the original chemical composition of the disk. Consequently, the study of accretion shocks is essential fora better understanding of the physical processes at disk scales and their chemical output. The purpose of this work is to assess
the characteristics of accretion shocks traced by sulfur-related species. We present ALMA high angular resolution observations(0.1") of the Class I protostar Oph-IRS 44. The continuum emission at 0.87 mm is observed, together with sulfur-related species
such as SO, SO2 , and 34 SO2 . Six lines of SO2 , two lines of 34 SO2 , and one line of SO are detected toward IRS 44. The emissionof all the detected lines peaks at 0.1" ( 14 au) from the continuum peak and we find infalling-rotating motions inside 30 au.
However, only redshifted emission is seen between 50 and 30 au. Colder and more quiescent material is seen toward an offset
region located at a distance of 400 au from the protostar, and we do not find evidence of a Keplerian profile in these data.
Accretion shocks are the most plausible explanation for the high temperatures, high densities, and velocities found for the SO2
emission. When material enters the disk–envelope system, it generates accretion shocks that increase the dust temperature anddesorb SO2 molecules from dust grains. High-energy SO2 transitions ( 200 K) seem to be the best tracers of accretion shocks
that can be followed up by future higher angular resolution ALMA observations and compared to other species to assess theirimportance in releasing molecules from the dust to the gas phase.

Multi-wavelength Observations of MWC 297: Constraints on Disk Inclination and Mass

60. Outflow

William D. Vacca, Göran Sandell F MWC 297 is a young, early-type star driving an ionized outflow and surroundedby warm, entrained dust. Previous analyses of near- and mid-IR interferometric images suggest that the emission at thesewavelengths arises from a compact accretion disk with a moderate (i < 40 degrees) inclination. We have obtained 5-40 micron
images of MWC 297 with FORCAST on SOFIA, as well as near-infrared spectra acquired with SpeX on the IRTF and radio
data obtained with the VLA and BIMA, and supplemented these with archival data from Herschel/PACS and SPIRE. The
FORCAST images, combined with the VLA data, indicate that the outflow lobes are aligned nearly north-south and are well
separated. Simple geometrical modeling of the FORCAST images suggests that the disk driving the outflow has an inclinationof 55 ± 5 degrees, in disagreement with the results of the interferometric analyses. Analysis of the SpeX data, with a wind−7
model, suggests the the mass loss rate is on the order of 6.0±3.7
M yr−1 and the extinction to the source is AV ∼ 8.1±2.5
1.7 ×101.5
mag. We have combined our data with values from the literature to generate the spectral energy distribution of the source from
0.35 µm to 6 cm and estimate the total luminosity. We find the total luminosity to be about 7900 L , if we include emission
from an extended region around the star, only slightly below that expected for a B1.5V star. The reddening must be produced
by dust along the line of sight, but distant from the star.

of the outflow in L1451-mm: SiO line and CH3 OH maser detections
61. Confirmation
V. Wakelam, A. Coutens, P. Gratier, T. H G Vidal, N. Vaytet F The observational counterparts of theoretically
predicted first hydrostatic cores (FHSC) have been searched for in the interstellar medium for nearly two decades now. Distinguishing them from other types of more evolved but still embedded objects remains a challenge because these objects havea short lifetime, are small, and embedded in a dense cocoon. One possible lead to finding them is the characterization of theoutflows that are launched by these objects. We observed the L1451-mm FHSC candidate with the NOEMA interferometer inorder to study the emission of several molecules. A nonlocal thermodynamic equilibrium analysis of the CH3 OH detected lines
was performed to retrieve the physical conditions of the emitting region around the central source, together with the CH3 OH,
SiO, CS, and H2 CO column densities. Of the targeted molecules, we detected lines of c-C3 H2 , CH3 OH, CS, C34 S, SO, DCN,
DCO+ , H2 CO, HC3 N, HDCO, and SiO. One of the methanol lines appears to be a maser line. The detection of this class I
maser and the SiO line in L1451-mm support the presence of a low-velocity and compact outflow. The excitation conditions of
the thermal lines of methanol are also compatible with shocks (H2 density of ∼ 3 × 106 cm−3 and a temperature higher than
40 K). Although these low-velocity outflows are theoretically predicted by some models of FHSC, these models also predict
the shock temperature to be below 20 K, that is, not evaporating methanol. In addition, the predicted velocities would noterode the grains and release silicon in the gas phase. We therefore conclude that these new observations favor the hypothesisthat L1451-mm would be at a very early protostellar stage, launching an outflow nearly on the plane of the sky with a higher
velocity than is observed.

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uncovers highly filamentary structure towards the Sgr E region
62. ALMA
J. Wallace, C. Battersby, E. A. C. Mills, J. D. Henshaw, M. C. Sormani, A. Ginsburg, A. T. Barnes, H. P.
Hatchfield, S. C. O. Glover, L. D. Anderson F We report on the discovery of linear filaments observed in CO(1-0) emission
for a ∼ 20 field of view toward the Sgr E star forming region centered at (l,b)=(358.720◦ , 0.011◦ ). The Sgr E region is thought
to be at the turbulent intersection of the ”far dust lane” associated with the Galactic bar and the Central Molecular Zone
(CMZ). This region is subject to strong accelerations which are generally thought to inhibit star formation, yet Sgr E contains
a large number of HII regions. We present 12 CO(1-0), 13 CO(1-0), and C18 O(1-0) spectral line observations from ALMA andprovide measurements of the physical and kinematic properties for two of the brightest filaments. These filaments have widths(FWHM) of ∼ 0.1 pc and are oriented nearly parallel to the Galactic plane, with angles from the Galactic plane of ∼ 2◦ . The
filaments are elongated, with lower limit aspect ratios of ∼5:1. For both filaments we detect two distinct velocity componentsthat are separated by about 15 km s−1 . In the C18 O spectral line data with ∼0.09 pc spatial resolution, we find that thesevelocity components have relatively narrow (∼1-2 km s−1 ) FWHM linewidths when compared to other sources towards the
Galactic center. The properties of these filaments suggest that the gas in the Sgr E complex is being ”stretched” as it is rapidly
accelerated by the gravitational field of the Galactic bar while falling towards the CMZ, a result that could provide insight into
the extreme environment surrounding this region and the large-scale processes which fuel this environment.

Discovery of Line Pressure Broadening and Direct Constraint on Gas Surface Density

63. in a Protoplanetary Disk

Tomohiro C. Yoshida, Hideko Nomura, Takashi Tsukagoshi, Kenji Furuya, Takahiro Ueda F The gas surface
density profile of protoplanetary disks is one of the most fundamental physical properties to understand planet formation.
However, it is challenging to determine the surface density profile observationally, because the H2 emission cannot be observedin low-temperature regions. We analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) archival data of the COline toward the protoplanetary disk around TW Hya and discovered extremely broad line wings due to the pressure broadening.
In conjunction with a previously reported optically thin CO isotopologue line, the pressure broadened line wings enabled us todirectly determine the midplane gas density for the first time. The gas surface density at ∼ 5 au from the central star reaches∼ 103 g cm−2 , which suggests that the inner region of the disk has enough mass to form a Jupiter-mass planet. Additionally,
the gas surface density drops at the inner cavity by ∼ 2 orders of magnitude compared to outside the cavity. We also found a
low CO abundance of ∼ 10−6 with respect to H2 , even inside the CO snowline, which suggests conversion of CO to less volatile
species. Combining our results with previous studies, the gas surface density jumps at r ∼ 20 au, suggesting that the inner region(3 < r < 20 au) might be the magnetorotational instability dead zone. This study sheds light on direct gas-surface-density
constraint without assuming the CO/H2 ratio using ALMA.

Directly Detecting the Envelopes of Low-mass Planets Embedded In Protoplanetary

64. Discs and The Case For TW Hydrae

Zhaohuan Zhu, Avery Bailey, Enrique Macías, Takayuki Muto, Sean M. Andrews F Despite many methods developed to find young massive planets in protoplanetary discs, it is challenging to directly detect low-mass planets that areembedded in discs. On the other hand, the core-accretion theory suggests that there could be a large population of embedded
low-mass young planets at the Kelvin-Helmholtz (KH) contraction phase. We adopt both 1-D models and 3-D simulations
to calculate the envelopes around low-mass cores (several to tens of M⊕ ) with different luminosities, and derive their thermal
fluxes at radio wavelengths. We find that, when the background disc is optically thin at radio wavelengths, radio observations
can see through the disc and probe the denser envelope within the planet’s Hill sphere. When the optically thin disc is observedwith the resolution reaching one disc scale height, the radio thermal flux from the planetary envelope around a 10 M⊕ core ismore than 10% higher than the flux from the background disc. The emitting region can be extended and elongated. Finally,
our model suggests that the au-scale clump at 52 au in the TW Hydrae disc revealed by ALMA is consistent with the envelopeof an embedded 10-20 M⊕ planet, which can explain the detected flux, the spectral index dip, and the tentative spirals. The
observation is also consistent with the planet undergoing pebble accretion. Future ALMA and ngVLA observations may directly
reveal more such low-mass planets, enabling us to study core growth and even reconstruct the planet formation history using
the embedded "protoplanet" population.

– Radial Velocity Survey for Planets around Young Stars. Target characteri65. RVSPY
zation and high-cadence survey
O. Zakhozhay, R. Launhardt, A. Mueller, S. Brems, P. Eigenthaler, M. Gennaro, A. Hempel, M. Hempel, Th.
Henning, G. Kennedy, S. Kim, M. Kuerster, R. Lachaume, Y. Manerikar, J. Patel, A. Pavlov, S. Reffert, T.
Trifonov F We introduce our Radial Velocity Survey for Planets around Young stars (RVSPY), characterise our target stars,
and search for substellar companions at orbital separations smaller than a few au from the host star. We use the FEROS
spectrograph to obtain high signal-to-noise spectra and time series of precise radial velocities (RVs) of 111 stars most of which
are surrounded by debris discs. Our target stars have spectral types between early F and late K, a median age of 400 Myr,

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and a median distance of 45 pc. We determine for all target stars their basic stellar parameters and present the results of thehigh-cadence RV survey and activity characterization. We achieve a median single-measurement RV precision of 6 m/s andderive the short-term intrinsic RV scatter of our targets (median 22 m/s), which is mostly caused by stellar activity and decays
with age from >100 m/s at <20 Myr to <20 m/s at >500 Myr. We discover six previously unknown close companions withorbital periods between 10 and 100 days, three of which are low-mass stars, and three are in the brown dwarf mass regime. We
detect no hot companion with an orbital period <10 days down to a median mass limit of 1 MJup for stars younger than 500
Myr, which is still compatible with the established occurrence rate of such companions around main-sequence stars. We findsignificant RV periodicities between 1.3 and 4.5 days for 14 stars, which are, however, all caused by rotational modulation due
to starspots. We also analyse the TESS photometric time series data and find significant periodicities for most of the stars.
For 11 stars, the photometric periods are also clearly detected in the RV data. We also derive stellar rotation periods ranging
from 1 to 10 days for 91 stars, mostly from TESS data. From the intrinsic activity-related short-term RV jitter, we derive theexpected mass-detection thresholds for longer-period companions.

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