The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 366 — 30 June 2023
Editor: João Alveswww.starformation.news

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Cover image caption
The core of the Lagoon Nebula (M8). Visible near the image center are two distinctive funnel-shaped clouds, each spanningapproximately half a light-year. These structures originate from the combined effects of vigorous stellar winds and intenseradiant energy generated within the vicinity. Herschel 36, a remarkable O-star with 32 M seen towards the center of theimage, illuminates the surrounding region. Walls of dust obscure and impart a reddish hue to the light emitted by other young,hot stars present in the area. The Lagoon Nebula lies at about 1.5 kpc, in the recently identified Sagittarius Spur.
Credits: NASA, ESA, Hubble; Processing by Francisco Javier Pobes Serrano
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
Hα emission line sources from VLT-MUSE in a low-metallicity star forming region –1. Dolidze 25
Mizna Ashraf, Jessy Jose, Gregory Herczeg, Min Fang F The process of accretion through circumstellar disks in youngstellar objects is an integral part of star formation and the Hα emission line is a prominent signature of accretion in low-massstars. We present the detection and characterization of Hα emission line sources in the central region of a distant, low-metallicity
young stellar cluster - Dolidze 25 (at ∼ 4.5 kpc) - using medium-resolution optical spectra (4750-9350 Å ) obtained with theMulti-Unit Spectroscopic Explorer (MUSE) at the VLT. We have identified 14 potential accreting sources within a rectangularregion of (20 x 10 ) towards the center of the cluster based on the detection of strong and broad emissions in Hα as well as thepresence of other emission lines such as [OI] and Hβ. Based on their positions in both photometric color-magnitude and colorcolor diagrams, we have also confirmed that these objects belong to the pre-main sequence phase of star formation. Our results
were compared with the disk and diskless members of the cluster previously identified by Guarcello et al. (2021) using near-IR
colors, and all sources they had identified as disks were confirmed to be accreting based on the spectroscopic characteristics.

2. Size Dependence of the Bouncing Barrier in Protoplanetary Dust Growth

Sota Arakawa, Satoshi Okuzumi, Misako Tatsuuma, Hidekazu Tanaka, Eiichiro Kokubo, Daisuke Nishiura,
Mikito Furuichi, Taishi Nakamoto F Understanding the collisional behavior of dust aggregates is essential in the context
of planet formation. It is known that low-velocity collisions of dust aggregates result in bouncing rather than sticking when
the filling factor of colliding dust aggregates is higher than a threshold value. However, a large discrepancy between numericaland experimental results on the threshold filling factor was reported so far. In this study, we perform numerical simulations
using soft-sphere discrete element methods and demonstrate that the sticking probability decreases with increasing aggregatesradius. Our results suggest that the large discrepancy in the threshold filling factor may reflect the difference in the size of dust
aggregates in earlier numerical simulations and laboratory experiments.

Streamers feeding the SVS13-A protobinary system: astrochemistry reveals accretion
3. shocks?
Eleonora Bianchi, Ana López-Sepulcre, Cecilia Ceccarelli, Claudio Codella, Linda Podio, Mathilde Bouvier,Joan Enrique-Romero, Rafael Bachiller, Bertrand Leflochb F We report ALMA high-angular resolution ( 50 au)
observations of the binary system SVS13-A. More specifically, we analyse deuterated water (HDO) and sulfur dioxide (SO2)emission. The molecular emission is associated with both the components of the binary system, VLA4A and VLA4B. The

2

spatial distribution is compared to that of formamide (NH2CHO), previously analysed in the system. Deuterated water reveals
an additional emitting component spatially coincident with the dust accretion streamer, at a distance larger than 120 aufrom the protostars, and at blue-shifted velocities (> 3 km/s from the systemic velocities). We investigate the origin of themolecular emission in the streamer, in light of thermal sublimation temperatures calculated using updated binding energies (BE)distributions. We propose that the observed emission is produced by an accretion shock at the interface between the accretion
streamer and the disk of VLA4A. Thermal desorption is not completely excluded in case the source is actively experiencing an
accretion burst.

4.

The Origin of Universality in the Inner Edges of Planetary Systems
Konstantin Batygin, Fred C. Adams, Juliette Becker F The characteristic orbital period of the inner-most objects
within the galactic census of planetary and satellite systems appears to be nearly universal, with P on the order of a few
days. This paper presents a theoretical framework that provides a simple explanation for this phenomenon. By considering
the interplay between disk accretion, magnetic field generation by convective dynamos, and Kelvin-Helmholtz contraction, we
derive an expression for the magnetospheric truncation radius in astrophysical disks, and find that the corresponding orbital
frequency is independent of the mass of the host body. Our analysis demonstrates that this characteristic frequency corresponds
to a period of P ∼ 3 days, although intrinsic variations in system parameters are expected to introduce a factor of ∼ 2 − 3
spread in this result. Standard theory of orbital migration further suggests that planets should stabilize at an orbital periodthat exceeds disk truncation by a small margin. Cumulatively, our findings predict that the periods of close-in bodies should
span P ∼ 2 − 12 days - a range that is consistent with observations.

5.

Episodic infall towards a compact disk in B335?

6.

Deuterium Fractionation across the Infrared Dark Cloud G034.77-00.55 interacting with
the Supernova Remnant W44

Per Bjerkeli, Jon P. Ramsey, Daniel Harsono, Adele Plunkett, Zhi-Yun Li, Matthijs H. D., van der Wiel,
Hannah Calcutt, Jes K. Jørgensen, Lars E. Kristensen F Previous observations of B335 have presented evidence ofongoing infall in various molecular lines, e.g., HCO+ , HCN, CO. There have been no confirmed observations of a rotationally
supported disk on scales greater than 12 au. The presence of an outflow in B335 suggests that also a disk should be present orin formation. To constrain the earliest stages of protostellar evolution and disk formation, we aim to map the region where gas
falls inwards and observationally constrain its kinematics. Furthermore, we aim to put strong limits on the size and orientationof any disk-like structure in B335. We use high angular resolution 13 CO data from ALMA, and combine it with shorter-baselinearchival data to produce a high-fidelity image of the infall in B335. We also revisit the imaging of high-angular resolution Band
6 continuum data to study the dust distribution in the immediate vicinity of B335. Continuum emission shows an ellipticalstructure (10 by 7 au) with a position angle 5 degrees east of north, consistent with the expectation for a forming disk in B335.
A map of the infall velocity (as estimated from the 13 CO emission), shows evidence of asymmetric infall, predominantly fromthe north and south. Close to the protostar, infall velocities appear to exceed free-fall velocities. 3D radiative transfer models,
where the infall velocity is allowed to vary within the infall region, can explain the observed kinematics. The data suggests thata disk has started to form in B335 and that gas is falling towards that disk. However, kinematically-resolved line data towards
the disk itself is needed to confirm the presence of a rotationally supported disk around this young protostar. The measured
high infall velocities are not easily reconcilable with a magnetic braking scenario and suggest that there is a pressure gradientthat allows the infall velocity to vary in the region.

G. Cosentino, J. C. Tan, I. Jiménez-Serra, F. Fontani, P. Caselli, J. D. Henshaw, A. T. Barnes, C. -Y. Law, S.
Viti, R. Fedriani, C. -J. Hsu, P. Gorai, S. Zeng F Supernova remnants (SNRs) may regulate star formation in galaxies.
For example, SNR-driven shocks may form new molecular gas or compress pre-existing clouds and trigger the formation of+
2H
new stars. To test this scenario, we measure the deuteration of N2 H + , DfNrac, a well-studied tracer of pre-stellar cores,
across the Infrared Dark Cloud (IRDC) G034.77-00.55, known to be experiencing a shock interaction with the SNR W44. We
use N2 H+ and N2 D+ J=1-0 single pointing observations obtained with the 30m antenna at the Instituto de Radioastronomia+
2H
Millimetrica to infer DfNrac
toward five positions across the cloud, namely a massive core, different regions across the shock
2H
front, a dense clump and ambient gas. We find DfNrac+in the range 0.03-0.1, several orders of magnitude larger than the+
2H
Across the shock front, DfNrac+

2H
cosmic D/H ratio (∼10 ).
is enhanced by more than a factor of 2 (DfNrac∼0.05-0.07) withrespect to the ambient gas (≤0.03) and similar to that measured generally in pre-stellar cores. Indeed, in the massive core and+2Hdense clump regions of this IRDC we measure DfNrac∼0.1. We find enhanced deuteration of N2 H + across the region of theshock, at a level that is enhanced with respect to regions of unperturbed gas. It is possible that this has been induced by shockcompression, which would then be indirect evidence that the shock is triggering conditions for future star formation. However,since unperturbed dense regions also show elevated levels of deuteration, further, higher-resolution studies are needed to better−53

understand the structure and kinematics of the deuterated material in the shock region, e.g., if it still in relatively diffuse formor already organised in a population of low-mass pre-stellar cores.

7. Magnetically-activated accretion outbursts of pre-main sequence discs

Jacob Cleaver, Lee Hartmann, Jaehan Bae F We investigate whether triggering of the magnetorotational instability(MRI) in protoplanetary discs can account for the wide diversity of observed accretion outbursts. We show that short-lived,
relatively low accretion rate events probably result from triggering in the inner disc and can occur at low surface densities,
comparable to or smaller than the minimum mass solar nebula, and thus are very unlikely to result from MRI triggering bygravitational instability. We develop time-dependent accretion disc models using an α-viscosity approach and calculate light
curves to compare with observations. Our modeling indicates that the lag time between infrared and optical bursts seen in
Gaia 17bpi can be explained with an outside-in propagation with an α ∼ 0.1 in the MRI-active region, consistent with otherestimates. While outbursts in inner discs can show time delays of a few years between infrared and optical light curves,
our models indicate that large, FU Ori-like bursts can exhibit infrared precursors decades before optical bursts. Detecting
such precursors could enable analysis of the central star before it is overwhelmed by the rapid accreting material, as well as
constraining outburst physics. Our results emphasize the importance of near-infrared monitoring of young stellar objects inaddition to optical surveys. In addition, our findings emphasize the need for more sophisticated, three-dimensional, non-ideal
magnetohydrodynamic simulations to fully exploit observational results.

8. Observational Signatures of Circumbinary Discs I: Kinematics

Josh Calcino, Daniel J. Price, Christophe Pinte, Himanshi Garg, Brodie J. Norfolk, Valentin Christiaens,
Hui Li, Richard Teague F We present five morphological and kinematic criteria to aid in asserting the binary nature of a
protoplanetary disc, based on 3D hydrodynamical simulations of circumbinary discs post-processed with Monte Carlo radiativetransfer. We find that circumbinary discs may be identified by i) a central cavity, ii) spiral arms both in and outside of
their central cavities, iii) non-localised perturbations in their iso-velocity curves, iv) asymmetry between the lines of maximum
speed of the blue and red-shifted wings and v) asymmetry between the area of the blue and red-shifted wings. We provide
quantitative metrics for the last two criteria that can be used, in conjunction with the morphological criteria, to signal whether
a protoplanetary disc is likely to be a circumbinary disc.

9. Astrochemical models of interstellar ices: History matters

A. Clément, A. Taillard, V. Wakelam, P. Gratier, J. -C. Loison, E. Dartois, F. Dulieu, J. A. Noble, M.
Chabot F Ice is ubiquitous in the interstellar medium. We model the formation of the main constituents of interstellar ices,
including H2O, CO2 , CO, and CH3 OH. We strive to understand what physical or chemical parameters influence the final
composition of the ice and how they benchmark to what has already been observed, with the aim of applying these models
to the preparation and analysis of JWST observations. We used the Nautilus gas-grain model, which computes the gas andice composition as a function of time for a set of physical conditions, starting from an initial gas phase composition. All
important processes (gas-phase reactions, gas-grain interactions, and grain surface processes) are included and solved with therate equation approximation. We first ran an astrochemical code for fixed conditions of temperature and density mapped in
the cold core L429-C to benchmark the chemistry. One key parameter was revealed to be the dust temperature. When the
dust temperature is higher than 12 K, CO2 will form efficiently at the expense of H2O, while at temperatures below 12 K, it
will not form. Whatever hypothesis we assumed for the chemistry (within realistic conditions), the static simulations failed toreproduce the observed trends of interstellar ices in our target core. In a second step, we simulated the chemical evolution ofparcels of gas undergoing different physical and chemical situations throughout the molecular cloud evolution and starting a
few 1e7 yr prior to the core formation (dynamical simulations). Our dynamical simulations satisfactorily reproduce the main
trends already observed for interstellar ices. Moreover, we predict that the apparent constant ratio of CO2/H2O observed todate is probably not true for regions of low AV , and that the history of the evolution of clouds plays an essential role, evenprior to their formation.

10. Protoplanetary disks around young stellar and substellar objects in the σ Orionis cluster
Belinda Damian, Jessy Jose, Beth Biller, KT Paul F Understanding the evolution and dissipation of protoplanetarydisks are crucial in star and planet formation studies. We report the protoplanetary disk population in the nearby young σOrionis cluster (d∼408 pc; age∼1.8 Myr) and analyse the disk properties such as dependence on stellar mass and disk evolution.
We utilise the comprehensive census of 170 spectroscopic members of the region refined using astrometry from Gaia DR3 fora wide mass range of ∼19-0.004 M . Using the near infrared (2MASS) and mid infrared (WISE) photometry we classify thesources based on the spectral index into class I, class II, flat spectrum and class III young stellar objects. The frequency ofsources hosting a disk with stellar mass <2 M in this region is 41±7% which is consistent with the disk fraction estimated inprevious studies. We see that there is no significant dependence of disk fraction on stellar mass among T Tauri stars (<2 M ),4but we propose rapid disk depletion around higher mass stars (>2 M ). Furthermore we find the lowest mass of a disk bearing
object to be ∼ 20 MJup and the pronounced disk fraction among the brown dwarf population hints at the formation scenariothat brown dwarfs form similar to low-mass stars.

11. The evolution of the internal structure of massive star forming regions in the Milky
Way as revealed by ALMA
Sami Dib F We analyze the structure of 15 protocluster forming regions in the Milky Way using their 1.3 mm continuum
emission maps from the ALMA-IMF large program. The analysis of the clouds structure is performed using the delta-variancespectrum technique. The calculated spectra display a self-similar regime on small scales as well as the presence of a prominent
bump on larger scales and whose physical size, Lhub , falls in the range of ≈ 7000 au to 60000 au. These scales correspondto the sizes of the most compact clumps within the protocluster forming clouds. A significant correlation is found between
Lhub and the surface density of the free-free emission estimated from the integrated flux of the H41α recombination lineΣfree−freeas well as a significant anti-correlation between Lhub and the ratio of the 1.3 mm to 3 mm continuum emission fluxes
H41α


cloud
cloud
cloud
cloud
S1.3mm/S3mm. Smaller values of S1.3mm/S3mm
and larger values of Σfree−freecorrespond to more advanced evolutionary
H41αstages of the protocluster forming clumps. Hence, our results suggest that the sizes of the densest regions in the clouds are
directly linked to their evolutionary stage and to their star formation activity with more evolved clouds having larger protocluster
forming clumps. This is an indication that gravity plays a vital role in regulating the size and mass growth and star formation
activity of these clumps with ongoing gas accretionthe frequencies of circumbinary discs in protostellar systems
12. OnDaniel Elsender, Matthew R. Bate, Ben S. Lakeland, Eric L. N. Jensen, Stephen H. Lubow F We report theanalysis of circumbinary discs formed in a radiation hydrodynamical simulation of star cluster formation. We consider bothpure binary stars and pairs within triple and quadruple systems. The protostellar systems are all young (ages < 105 yrs). We
find that the systems that host a circumbinary disc have a median separation of ≈ 11 au, and the median characteristic radiusof the discs is ≈ 64 au. We find that 89 per cent of pure binaries with semi-major axes a < 1 au have a circumbinary disc,and the occurrence rate of circumbinary discs is bimodal with log-separation in pure binaries with a second peak at a ≈ 50 au.
Systems with a > 100 au almost never have a circumbinary disc. The median size of a circumbinary disc is between ≈ 5 − 6 adepending on the order of the system, with higher order systems having larger discs relative to binary separation. We findthe underlying distribution of mutual inclinations between circumbinary discs and binary orbit of both observed and simulated
discs to not differ statistically.

13. Star Cluster Formation from Turbulent Clumps. III. Across the mass spectrum

Juan P. Farias, Jonathan C. Tan F We study the formation and early evolution of star clusters that have a wide range of
masses and background cloud mass surface densities, Σcloud , which help set the initial sizes, densities, and velocity dispersionsof the natal gas clumps. Initial clump masses of 300, 3, 000 and 30, 000 M are considered, from which star clusters are bornwith an assumed 50% overall star formation efficiency and with 50% primordial binarity. This formation is gradual, i.e., with arange of star formation efficiencies per free-fall time from 1% to 100%, so that the formation time can range from 0.7 Myr for
low-mass, high-Σcloud clumps to ∼ 30 Myr for high-mass, low-Σcloud clumps. Within this framework of the Turbulent Clumpmodel, for a given Σcloud , clumps of higher mass are of lower initial volume density, but their dynamical evolution leads to higher
bound fractions and causes them to form much higher density cluster cores and maintain these densities for longer periods.
This results in systematic differences in the evolution of binary properties, degrees of mass segregation and rates of creation of
dynamically ejected runaways. We discuss the implications of these results for observed star clusters and stellar populations.

The sharpest view on the high-mass star-forming region S255IR. Near-InfraRed Adap14. tive Optics Imaging on the Outbursting Source NIRS3
R. Fedriani, A. Caratti o Garatti, R. Cesaroni, J. C. Tan, B. Stecklum, L. Moscadelli, M. Koutoulaki, G.
Cosentino, M. Whittle F Massive stars have an impact on their surroundings from early in their formation until the end of
their lives. However, very little is known about their formation. Episodic accretion may play a crucial role, but observationsof these events have only been reported towards a handful of massive protostars. We aim to investigate the outburst eventfrom the high-mass star-forming region S255IR where recently the protostar NIRS3 underwent an accretion outburst. We
follow the evolution of this source both in photometry and morphology of its surroundings. Methods: We perform near-infrared
adaptive optics observations on the S255IR central region using the Large Binocular Telescope in the Ks broad-band and theH2 and Brγ narrow-band filters with an angular resolution of ∼ 0.06 arcsec, close to the diffraction limit. We discover a newnear-infrared knot north-east from NIRS3 that we interpret as a jet knot that was ejected during the last accretion outburst
and observed in the radio regime as part of a follow-up after the outburst. We measure a mean tangential velocity for thisknot of 450 ± 50 km s−1 . We analyse the continuum-subtracted images from H2 which traces jet shocked emission, and Brγ

5which traces scattered light from a combination of accretion activity and UV radiation from the central massive protostar. We
observe a significant decrease in flux at the location of NIRS3, with K=13.48 mag being the absolute minimum in the historic
series. Our observations strongly suggest a scenario where the episodic accretion is followed by an episodic ejection responsein the near-infrared, as it was seen in the earlier radio follow-up. The 30 years of ∼ 2 µm photometry suggests that NIRS3
might have undergone another outburst in the late 1980s, being the first massive protostar with such evidence observed in thenear-infrared.

15. Stellar clustering and the kinematics of stars around Collinder 121 using Gaia DR3

Graham D. Fleming, Jason M. Kirk, Derek Ward-Thompson F We study the region around Collinder 121 (Cr 121)
using newly available 6-dimensional data from the Gaia DR3 catalogue. Situated in the third quadrant, near the galactic plane,
Collinder 121 lies in the region of Canis Major centred around l = 236 degrees, b = -10 degrees. Previous studies have suggested
that the stellar associations in this region comprise an OB association (CMa OB2) lying at about 740 pc with a more distant
open cluster (Cr 121) at approximately 1170 pc. Despite these studies, the precise nature of Collinder 121 remains uncertain.
This study investigates the region bounded by the box l = 225 to 245 degrees, b = 0.00 to -20.00 degrees to a depth of 700
pc from 500 to 1200 pc which fully encompasses the region discussed in the literature. Using Gaia DR3 data, we do not findassociations at the distances given in the literature. Instead, using the HDBSCAN machine learning algorithm, we find a major
association of OB stars centred around 803 pc. Within this association we find four smaller subgroups that may be indicativeof a larger association and which are located at a mean distance of 827 pc. Proper motion studies find coherence between thesefour subgroups and show a distinctive east to west increase in the size of the velocity vectors which supports contemporary
studies that show similar trends in OB populations in Cygnus and within the Carina spiral Arm. Therefore, we hypothesizethat Cr 121 and CMa OB2 are the same cluster, consistent with the 1977 study by Hoogerwerf.

PENELLOPE IV. A comparison between optical forbidden lines and H2 UV lines in the
16. Orion OB1b and σ-Ori associations
M. Gangi, B. Nisini, C. F. Manara, K. France, S. Antoniucci, K. Biazzo, T. Giannini, G. J. Herczeg, J. M.
Alcalá, A. Frasca, K. Maucó, J. Campbell-White, M. Siwak, L. Venuti, P. C. Schneider, Á. Kóspál, A. Carattio Garatti, E. Fiorellino, E. Rigliaco, R. K. Yadav F Observing the spatial distribution and excitation processes ofatomic and molecular gas in the inner regions (< 20 au) of young (< 10 Myr) protoplanetary disks helps us to understandthe conditions for the formation and evolution of planetary systems. In the framework of the PENELLOPE and ULLYSES
projects, we aim to characterize the atomic and molecular component of protoplanetary disks in a sample of 11 Classical T
Tauri Stars (CTTs) of the Orion OB1 and σ-Orionis associations. We analyzed the flux-calibrated optical-forbidden lines andthe fluorescent ultraviolet H2 progressions using spectra acquired with ESPRESSO at VLT, UVES at VLT and HST-COS. Linemorphologies were characterized through Gaussian decomposition. We then focused on the properties of the narrow low-velocity(FWHM < 40 km s−1 and |vp | < 30 km s−1 ) component (NLVC) of the [OI] 630 nm line, compared with the properties of
the UV-H2 lines. We found that the [OI]630 NLVC and the UV-H2 lines are strongly correlated in terms of peak velocities,
full width at half maximum, and luminosity. The luminosities of the [OI]630 NLVC and UV-H2 correlate with the accretion
luminosity with a similar slope, as well as with the luminosity of the CIV 154.8, 155 nm doublet. We discuss such correlationsin the framework of the currently suggested excitation processes for the [OI]630 NLVC. Our results can be interpreted in a
scenario in which the [OI]630 NLVC and UV-H2 have a common disk origin with a partially overlapped radial extension. We
also suggest that the excitation of the [OI] NLVC is mainly induced by stellar FUV continuum photons more than being ofthermal origin. This study demonstrates the potential of contemporaneous wide-band high-resolution spectroscopy in linking
different tracers of protoplanetary disks.

17. Post-outburst evolution of bonafide FUor V2493 Cyg: A Spectro-photometric monitoring
Arpan Ghosh, Saurabh Sharma, Joe P. Ninan, Devendra K. Ojha, Bhuwan C. Bhatt, D. K. Sahu, Tapas Baug,R. K. Yadav, Puji Irawati, A. S. Gour, Neelam Panwar, Rakesh Pandey, Tirthendu Sinha, Aayushi VermaF We present here the results of eight years of our near-simultaneous optical/near-infrared spectro-photometric monitoringof bonafide FUor candidate ‘V2493 Cyg’ starting from 2013 September to 2021 June. During our optical monitoring period(between October 16, 2015 and December 30, 2019), the V2493 Cyg is slowly dimming with an average dimming rate of ∼26.6± 5.6 mmag/yr in V band. Our optical photometric colors show a significant reddening of the source post the second outburst
pointing towards a gradual expansion of the emitting region post the second outburst. The mid infra-red colors, on the contrary,
exhibits a blueing trend which can be attributed to the brightening of the disc due to the outburst. Our spectroscopic monitoring shows a dramatic variation of the Hα line as it transitioned from absorption feature to the emission feature and back.
Such transition can possibly be explained by the variation in the wind structure in combination with accretion. Combining ourtime evolution spectra of the Ca II infra-red triplet lines with the previously published spectra of V2493 Cyg, we find that theaccretion region has stabilised compared to the early days of the outburst. The evolution of the O I λ7773 Å line also points

6

towards the stabilization of the circumstellar disc post the second outburst.

in compact to giant H II regions
18. Turbulence
J. García-Vázquez, William J. Henney, H. O. Castañeda F Radial velocity fluctuations on the plane of the sky are a
powerful tool for studying the turbulent dynamics of emission line regions. We conduct a systematic statistical analysis of theH alpha velocity field for a diverse sample of 9 H II regions, spanning two orders of magnitude in size and luminosity, locatedin the Milky Way and other Local Group galaxies. By fitting a simple model to the second-order spatial structure function ofvelocity fluctuations, we extract three fundamental parameters: the velocity dispersion, the correlation length, and the powerlaw slope. We determine credibility limits for these parameters in each region, accounting for observational limitations of noise,
atmospheric seeing, and the finite map size. The plane-of-sky velocity dispersion is found to be a better diagnostic of turbulent
motions than the line width, especially for lower luminosity regions where the turbulence is subsonic. The correlation lengthof velocity fluctuations is found to be always roughly 2% of the H II region diameter, implying that turbulence is driven on
relatively small scales. No evidence is found for any steepening of the structure function in the transition from subsonic tosupersonic turbulence, possibly due to the countervailing effect of projection smoothing. Ionized density fluctuations are toolarge to be explained by the action of the turbulence in any but the highest luminosity sources. A variety of behaviors are seenon scales larger than the correlation length, with only a minority of sources showing evidence for homogeneity on the largest
scales.

19. Similar levels of deuteration in the pre-stellar core L1544 and the protostellar core
HH211
K. Giers, S. Spezzano, P. Caselli, E. Wirström, O. Sipilä, J. E. Pineda, E. Redaelli, C. T. Bop, F. Lique F In
the centre of pre-stellar cores, deuterium fractionation is enhanced due to the low temperatures and high densities. Therefore,
the chemistry of deuterated molecules can be used to study the earliest stages of star formation. We analyse the deuterium
fractionation of simple molecules, comparing the level of deuteration in the envelopes of the pre-stellar core L1544 in Taurus
and the protostellar core HH211 in Perseus. We used single-dish observations of CCH, HCN, HNC, HCO+ , and their 13 C-,
18
O- and D-bearing isotopologues, detected with the Onsala 20m telescope. We derived the column densities and the deuterium
fractions of the molecules. Additionally, we used radiative transfer simulations and results from chemical modelling to reproduce
the observed molecular lines. We used new collisional rate coefficients for HNC, HN13 C, DNC, and DCN that consider thehyperfine structure of these molecules. We find high levels of deuteration for CCH (10%) in both sources, consistent with othercarbon chains, and moderate levels for HCN (5-7%) and HNC (8%). The deuterium fraction of HCO+ is enhanced towards
HH211, most likely caused by isotope-selective photodissociation of C18 O. Similar levels of deuteration show that the process islikely equally efficient towards both cores, suggesting that the protostellar envelope still retains the chemical composition of theoriginal pre-stellar core. The fact that the two cores are embedded in different molecular clouds also suggests that environmental
conditions do not have a significant effect on the deuteration within dense cores. Radiative transfer modelling shows that it isnecessary to include the outer layers of the cores to consider the effects of extended structures. Besides HCO+ observations,
HCN observations towards L1544 also require the presence of an outer diffuse layer where the molecules are relatively abundant.

20. JWST Peers into the Class I Protostar TMC1A: Atomic Jet and Spatially Resolved
Dissociative Shock Region
Daniel Harsono, Per Bjerkeli, Jon Ramsey, Klaus Pontoppidan, Lars Kristensen, Jes Jørgensen, Hannah Calcutt, Zhi-Yun Li, Adele Plunkett F Outflows and winds launched from young stars play a crucial role in the evolutionof protostars and the early stages of planet formation. However, the specific details of the mechanism behind these phenomena, including how they affect the protoplanetary disk structure, are still debated. We present JWST NIRSpec Integral Field
Unit (IFU) observations of atomic and H2 lines from 1 – 5.1 µm toward the low-mass protostar TMC1A. For the first time, acollimated atomic jet is detected from TMC1A in the [Fe II] line at 1.644 µm along with corresponding extended H2 2.12 µm
emission. Towards the protostar, we detected spectrally broad H I and He I emissions with velocities up to 300 km/s that canbe explained by a combination of protostellar accretion and a wide-angle wind. The 2µm continuum dust emission, H I, He I,
and O I all show emission from the illuminated outflow cavity wall and scattered line emission. These observations demonstrate
the potential of JWST to characterize and reveal new information about the hot inner regions of nearby protostars. In thiscase, a previously undetected atomic wind and ionized jet in a well-known outflow.

21. Inner Planetary System Gap Complexity is a Predictor of Outer Giant Planets

Matthias Y. He, Lauren M. Weiss F The connection between inner small planets and outer giant planets is crucial to ourunderstanding of planet formation across a wide range of orbital separations. While Kepler provided a plethora of compact
multi-planet systems at short separations (. 1 AU), relatively little is known about the occurrence of giant companions atlarger separations and how they impact the architectures of the inner systems. Here, we use the catalog of systems from the7Kepler Giant Planet Search (KGPS) to study how the architectures of the inner transiting planets correlate with the presenceof outer giant planets. We find that for systems with at least three small transiting planets, the distribution of inner-system gap
complexity (C), a measure of the deviation from uniform spacings, appears to differ (p . 0.02) between those with an outer giant
planet (50M⊕ ≤ Mp sin i ≤ 13MJup ) and those without any outer giants. All four inner systems (with 3+ transiting planets)
with outer giant(s) have a higher gap complexity (C > 0.32) than 79% (19/24) of the inner systems without any outer giants(median C ' 0.06). This suggests that one can predict the occurrence of outer giant companions by selecting multi-transiting
systems with highly irregular spacings. We do not find any correlation between outer giant occurrence and the size (similarity
or ordering) patterns of the inner planets. The larger gap complexities of inner systems with an outer giant hints that massive
external planets play an important role in the formation and/or disruption of the inner systems.

Constraint on the Amount of Hydrogen from the CO Chemistry in Debris Disks
22. A
Kazunari Iwasaki, Hiroshi Kobayashi, Aya E. Higuchi, Yuri Aikawa F The faint CO gases in debris disks are easily
dissolved into C by UV irradiation, while CO can be reformed via reactions with hydrogen. The abundance ratio of C/CO
could thus be a probe of the amount of hydrogen in the debris disks. We conduct radiative transfer calculations with chemical
reactions for debris disks. For a typical dust-to-gas mass ratio of debris disks, CO formation proceeds without the involvementof H2 because a small amount of dust grains makes H2 formation inefficient. We find that the CO to C number density ratio
depends on a combination of nH Z 0.4 χ−1.1 , where nH is the hydrogen nucleus number density, Z is the metallicity, and χ is the
FUV flux normalized by the Habing flux. Using an analytic formula for the CO number density, we give constraints on theamount of hydrogen and metallicity for debris disks. CO formation is accelerated by excited H2 either when the dust-to-gas
mass ratio is increased or the energy barrier of chemisorption of hydrogen on the dust surface is decreased. This acceleration of
CO formation occurs only when the shielding effects of CO are insignificant. In shielded regions, the CO fractions are almost
independent of the parameters of dust grains.

Investigating the Impact of Metallicity on Star Formation in the Outer Galaxy. I.
23. VLT/KMOS Survey of Young Stellar Objects in Canis Major
Dominika Itrich, Agata Karska, Marta Sewiło, Lars E. Kristensen, Gregory J. Herczeg, Suzanne Ramsay,
William J. Fischer, Benoît Tabone, Will R. M. Rocha, Maciej Koprowski, Ngân Lê, Beata Deka-Szymankiewicz
F The effects of metallicity on the evolution of protoplanetary disks may be studied in the outer Galaxy where the metallicity
is lower than in the solar neighbourhood. We present the VLT/KMOS integral field spectroscopy in the near-infrared of ∼120
candidate young stellar objects (YSOs) in the CMa-`224 star-forming region located at a Galactocentric distance of 9.1 kpc.
We characterise the YSO accretion luminosities and accretion rates using the hydrogen Brγ emission and find the medianaccretion luminosity of log (Lacc ) = −0.82+0.80−0.82 L . Based on the measured accretion luminosities, we investigate the hypothesisof star formation history in the CMa-`224. Their median values suggest that Cluster C, where most of YSO candidates havebeen identified, might be the most evolved part of the region. The accretion luminosities are similar to those observed toward
low-mass YSOs in the Perseus and Orion molecular clouds, and do not reveal the impact of lower metallicity. Similar studies
in other outer Galaxy clouds covering a wide range of metallicities are critical to gain a complete picture of star formation in
the Galaxy.

Investigating the Impact of Metallicity on Star Formation in the Outer Galaxy. I.
24. VLT/KMOS Survey of Young Stellar Objects in Canis Major
Dominika Itrich, Agata Karska, Marta Sewiło, Lars E. Kristensen, Gregory J. Herczeg, Suzanne Ramsay,
William J. Fischer, Benoît Tabone, Will R. M. Rocha, Maciej Koprowski, Ngân Lê, Beata Deka-Szymankiewicz
F The effects of metallicity on the evolution of protoplanetary disks may be studied in the outer Galaxy where the metallicity
is lower than in the solar neighbourhood. We present the VLT/KMOS integral field spectroscopy in the near-infrared of ∼120
candidate young stellar objects (YSOs) in the CMa-`224 star-forming region located at a Galactocentric distance of 9.1 kpc.
We characterise the YSO accretion luminosities and accretion rates using the hydrogen Brγ emission and find the medianaccretion luminosity of log (Lacc ) = −0.82+0.80−0.82 L . Based on the measured accretion luminosities, we investigate the hypothesisof star formation history in the CMa-`224. Their median values suggest that Cluster C, where most of YSO candidates havebeen identified, might be the most evolved part of the region. The accretion luminosities are similar to those observed toward
low-mass YSOs in the Perseus and Orion molecular clouds, and do not reveal the impact of lower metallicity. Similar studies
in other outer Galaxy clouds covering a wide range of metallicities are critical to gain a complete picture of star formation in
the Galaxy.

25. In search for infalling clumps in molecular clouds – A catalogue of CO blue-profiles
Zhibo Jiang, Shaobo Zhang, Zhiwei Chen, Yang Yang, Shuling Yu, Haoran Feng, Ji Yang, the MWISP group F
We have started a systematic survey of molecular clumps with infall motions to study the very early phase of star formation. Our

8first step is to utilize the data products by MWISP to make an unbiased survey for blue asymmetric line profiles of CO isotopicalmolecules. Within a total area of ∼ 2400 square degrees nearby the Galactic plane, we have found 3533 candidates showing
blue-profiles, in which 3329 are selected from the 12 CO&13 CO pair and 204 are from the 13 CO&C18 O pair. Exploration of theparametric spaces suggests our samples are in the cold phase with relatively high column densities ready for star formation.
Analysis of the spatial distribution of our samples suggests that they exist virtually in all major components of the Galaxy.
The vertical distribution suggest that the sources are located mainly in the thick disk of ∼ 85 parsec, but still a small part arelocated far beyond Galactic midplane. Our follow-up observation indicates that these candidates are a good sample to start a
search for infall motions, and to study the condition of very early phase of star formation.

26. Near infrared view on the photodissociation regions S255, S257, NGC7538 and S140

M. S. Kirsanova, A. M. Tatarnikov, P. A. Boley, D. S. Wiebe, N. A. Maslennikova, A. A. Tatarnikov F We
performed photometric observations of the S255, S257, S140, NGC7358 and the Orion Bar photo-dissociation regions (PDRs)
at 2 micron using narrow-band filters centered on the Br-gamma, H2 and [FeII] lines, as well as the narrow-band Kcont andthe broad-band H filters for continuum subtraction. The observations were done with the 2.5-m telescope of the SAI Caucasian
Mountain Observatory and the near-infrared camera and spectrograph ASTRONIRCAM. We find several high-density arc-likestructures in the Br-gamma and [FeII] images of the ionized gas in NGC7538 and extended shells and arcs visible throughthe H2 emission. The H ionization front and H2 dissociation front are merged in NGC7538. In S255 and S257 we detected
only Br-gamma emission from the HII regions and bright H2 emission from the PDRs. The projected distance between the H
ionization and H2 dissociation fronts are approx. 0.3-0.4 pc, which cannot be explained using models of a uniform medium.
Most probably, the ionized and neutral gas in these PDRs is clumpy. The H-to-H2 transitions in the NGC7538, S255, S257 andS140 PDRs are gradual with no sharp borders. This conclusion also confirms the suggestion of a clumpy medium.

27. Classification of Chandra X-ray Sources in Cygnus OB2

Vinay L. Kashyap, Mario G. Guarcello, Nicholas J. Wright, Jeremy J. Drake, Ettore Flaccomio, Tom L.
Aldcroft, Juan F. Albacete Colombo, Kevin Briggs, Francesco Damiani, Janet E. Drew, Eduardo L. Martin,
Giusi Micela, Tim Naylor, Salvatore Sciortino F We have devised a predominantly Naive Bayes method to classify
the optical/IR matches to X-ray sources detected by Chandra in the Cygnus OB2 association into foreground, member, andbackground objects. We employ a variety of X-ray, optical, and infrared characteristics to construct likelihoods using training
sets defined by well-measured sources. Combinations of optical photometry from SDSS (riz) and IPHAS (riHa), IR magnitudes
from UKIDSS and 2MASS (JHK), X-ray quantiles and hardness ratios, and estimates of extinction Av are used to compute therelative probabilities that a given source belongs to one of the classes. We use Principal Component Analysis of photometricmagnitude combinations to isolate the best axes for classification. We incorporate measurement errors into the classification.
We evaluate the accuracy of the classification by inspection and reclassify a number of sources based on IR magnitudes, presenceof disks, and X-ray spectral hardness. We also consider systematic errors due to extinction. We find that about 6100 objects
are association members, 1400 are background, and 500 are foreground objects. The overall classification accuracy is 95%.

28. SPYGLASS. IV. New Stellar Survey of Recent Star Formation within 1 kpc
Ronan Kerr, Adam Kraus, Aaron Rizzuto F Young stellar populations provide a powerful record that traces millionsof years of star formation history in the solar neighborhood. Using a revised form of the SPYGLASS young star identification
methodology, we produce an expanded census of nearby young stars (Age < 50 Myr). We then use the HDBSCAN clustering
algorithm to produce a new SPYGLASS Catalog of Young Associations (SCYA), which reveals 116 young associations within 1
kpc. More than 25% of these groups are largely new discoveries, as 20 are substantively different from any previous definition, and10 have no equivalent in the literature. The new associations reveal a yet undiscovered demographic of small associations withlittle connection to larger structures. Some of the groups we identify are especially unique for their high transverse velocities,
which can differ from the solar velocity by 30-50 km s−1 , and for their positions, which can reach up to 300 pc above thegalactic plane. These features may suggest a unique origin, matching existing evidence of infalling gas parcels interacting withthe disk ISM. Our clustering also suggests links between often-separated populations, hinting to direct structural connections
between Orion Complex and Perseus OB2, and between the subregions of Vela. The ∼30 Myr old Cepheus-Hercules association
is another emerging large-scale structure, with a size and population comparable to Sco-Cen. Cep-Her and other similarly-aged
structures are also found clustered along extended structures perpendicular to known spiral arm structure, suggesting that
arm-aligned star formation patterns have only recently become dominant in the solar neighborhood.

29. The magnetic fields around the cometary globules, L328, L323 and L331

Siddharth Kumar, Archana Soam, Nirupam Roy F This work presents the magnetic field geometry in a complex ofthree cometary (with head-tail morphology) globules, namely LDN 323, LDN 328, and LDN 331, using R-band polarization
measurements of background stars. These observations were combined with a Planck sky survey to study the large-scale

9morphology of the magnetic fields in the region. The distances of the target stars were adopted from the Gaia catalog. The
variation of degree of polarization and polarization position angle with distances of stars is analyzed. The field geometry ismostly found to follow the cometary shape of the cloud, with some randomness at certain locations. For studying the correlation
between cloud morphology and magnetic field orientations, a modified version of the Histogram of Relative Orientation analysis
was employed.

SO and SiS Emission Tracing an Embedded Planet and Compact 12 CO and 13 CO Coun30. terpartsin the HD 169142 Disk
Charles J. Law, Alice S. Booth, Karin I. Öberg F Planets form in dusty, gas-rich disks around young stars, while atthe same time, the planet formation process alters the physical and chemical structure of the disk itself. Embedded planets
will locally heat the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms suchas Si from dust grains. This should cause chemical asymmetries detectable in molecular gas observations. Using high-angularresolution ALMA archival data of the HD 169142 disk, we identify compact SO J=88 -77 and SiS J=19-18 emission coincident
with the position of a ∼2 MJup planet seen as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at≈38 au. The SiS emission is located along an azimuthal arc and has a similar morphology as a known 12 CO kinematic excess.
This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that the planet is driving sufficiently
strong shocks to produce gas-phase SiS. We also report the discovery of compact 12 CO and 13 CO J=3-2 emission coincident withthe planet location. Taken together, a planet-driven outflow provides the best explanation for the properties of the observed
chemical asymmetries. We also resolve a bright, azimuthally-asymmetric SO ring at ≈24 au. While most of this SO emission
originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations driven by a misaligned
inner disk or planet-disk interactions. Overall, the HD 169142 disk shows several distinct chemical signatures related to giant
planet formation and presents a powerful template for future searches of planet-related chemical asymmetries in protoplanetarydisks.

Molecular Clouds in the Galactic Plane from l = [59.75◦ , 74.75◦ ] and b = [−5.25◦ , +5.25◦ ]31. Chunxue
Li, Hongchi Wang, Yuehui Ma, Lianghao Lin, Yang Su, Chong Li, Yan Sun, Xin Zhou, Ji Yang F

In this paper we present the distribution of molecular gas in the Milky Way Galactic plane from l = [59.75, 74.75]◦ and b= [−5.25, +5.25]◦ , using the MWISP 12 CO/13 CO/C18 O emission line data. The molecular gas in this region can be mainly
attributed to the Local spur, Local arm, Perseus arm, and Outer arm. Statistics of the physical properties of the molecular gas
in each arm, such as excitation temperature, optical depth, and column density, are presented. Using the DBSCAN algorithm,
we identified 15 extremely distant molecular clouds with kinematic distances of 14.72−17.77 kpc and masses of 363−520 M ,which we find could be part of the Outer Scutum-Centaurus (OSC) arm identified by [?] and [?]. It is also possible that, 12of these 15 extremely distant molecular clouds constitute an independent structure between the Outer and the OSC arms or a
spur. There exist two Gaussian components in the vertical distribution of the molecular gas in the Perseus spiral arm. These
two Gaussian components correspond to two giant filaments parallel to the Galactic plane. We find an upward warping of themolecular gas in the Outer spiral arm with a displacement of around 270 pc with respect to the Galactic mid-plane.

32. JWST/NIRSpec Observations of the Planetary Mass Companion TWA 27B

K. L. Luhman, P. Tremblin, S. M. Birkmann, E. Manjavacas, J. Valenti, C. Alves de Oliveira, T. L. Beck, G.
Giardino, N. Lutzgendorf, B. J. Rauscher, M. Sirianni F We present 1-5um spectroscopy of the young planetary masscompanion TWA 27B (2M1207B) performed with NIRSpec on board the James Webb Space Telescope. In these data, thefundamental band of CH4 is absent and the fundamental band of CO is weak. The nondetection of CH4 reinforces a previously
observed trend of weaker CH4 with younger ages among L dwarfs, which has been attributed to enhanced non-equilibrium
chemistry among young objects. The weakness of CO may reflect an additional atmospheric property that varies with age, suchas the temperature gradient or cloud thickness. We are able to reproduce the broad shape of the spectrum with an ATMO
cloudless model that has T=1300 K, non-equilibrium chemistry, and a temperature gradient reduction caused by fingering
convection. However, the fundamental bands of CH4 and CO are somewhat stronger in the model. In addition, the model
temperature of 1300 K is higher than expected from evolutionary models given the luminosity and age of TWA 27B (T=1200 K).
Previous models of young L-type objects suggest that the inclusion of clouds could potentially resolve these issues; it remains tobe seen whether cloudy models can provide a good fit to the 1-5um data from NIRSpec. TWA 27B exhibits emission in Paschentransitions and the He I triplet at 1.083um, which are signatures of accretion that provide the first evidence of a circumstellar
disk. We have used the NIRSpec data to estimate the bolometric luminosity of TWA 27B (log L/Lsun =-4.466+/-0.014), which
implies a mass of 5-6 MJup according to evolutionary models.

10

First Detection of A Linear Structure in the Midplane of the Young HH 211 Protostellar
33. Disk: A Spiral Arm?
Chin-Fei Lee, Kai-Syun Jhan, Anthony Moraghan F Spiral structures have been detected in evolved protostellar disks,
driving the disk accretion towards the central protostars to facilitate star formation. However, it is still unclear if thesestructures can form earlier in young protostellar disks. With the Atacama Large Millimeter/submillimeter Array (ALMA), we
have detected and spatially resolved a very young and nearly edge-on dusty disk with a radius of only 20 au in the HH 211
protostellar system at submillimeter wavelength. It is geometrically thick, indicating that the submillimeter light-emitting dust
grains have yet to settle to the midplane for planet formation. Intriguingly, it shows 3 bright linear structures parallel to theequatorial plane, resembling a 3-layer pancake that has not been seen before. The top and bottom ones arise from the warm
disk surfaces, unveiling the flared structure of the disk. More importantly, the middle one is in the dense midplane of the disk
and can be modeled as a trailing spiral arm excited by disk gravity, as seen in evolved protostellar disks, supporting the presenceof spiral structures in the very early phase for disk accretion.

34. Imaging the warped dusty disk wind environment of SU Aurigae with MIRC-X

Aaron Labdon, Stefan Kraus, Claire L. Davies, Alexander Kreplin, Sebastian Zarrilli, John D. Monnier, JeanBaptiste le Bouquin, Narsireddy Anugu, Benjamin Setterholm, Tyler Gardner, Jacob Ennis, Cyprien Lanthermann, Theo ten Brummelaar, Gail Schaefer, Tim J. Harries F SU Aurigae is a widely studied T Tauri star and here
we present original state-of-the-art interferometric observations with better uv and baseline coverage than previous studies. We
aim to investigate the characteristics of the circumstellar material around SU Aur, constrain the disk geometry, composition andinner dust rim structure. The MIRC-X instrument at CHARA is a 6 telescope optical beam combiner offering baselines up to
331 m. We undertook image reconstruction for model-independent analysis, and fitted geometric models such as Gaussian andring distributions. Additionally, the fitting of radiative transfer models constrains the physical parameters of the disk. Image
reconstruction reveals a highly inclined disk with a slight asymmetry consistent with inclination effects obscuring the inner disk
rim through absorption of incident star light on the near-side and thermal re-emission/scattering of the far-side. Geometricmodels find that the underlying brightness distribution is best modelled as a Gaussian with a FWHM of 1.53 ± 0.01mas at an
inclination of 56.9 ± 0.4◦ and minor axis position angle of 55.9 ± 0.5◦ . Radiative transfer modelling shows a flared disk withan inner radius at 0.16 au which implies a grain size of 0.14µm assuming astronomical silicates and a scale height of 9.0 au at
100 au. In agreement with literature, only the dusty disk wind successfully accounts for the NIR excess by introducing dust
above the mid-plane. Our results confirm and provide better constraints than previous inner disk studies of SU Aurigae. We
confirm the presence of a dusty disk wind in the cicumstellar environment, the strength of which is enhanced by a late infall
event which also causes very strong misalignments between the inner and outer disks.

35. Triple spiral arms of a triple protostar system imaged in molecular lines
Jeong-Eun Lee, Tomoaki Matsumoto, Hyun-Jeong Kim, Seokho Lee, Daniel Harsono, Jaehan Bae, Neal J.
Evans II, Shu-ichiro Inutsuka, Minho Choi, Ken’ichi Tatematsu, Jae-Joon Lee, Dan Jaffe F Most stars formin multiple star systems. For a better understanding of their formation processes, it is important to resolve the individual
protostellar components and the surrounding envelope and disk material at the earliest possible formation epoch because theformation history can be lost in a few orbital timescales. Here we present the ALMA observational results of a young multiple
protostellar system, IRAS 04239+2436, where three well-developed large spiral arms were detected in the shocked SO emission.
Along the most conspicuous arm, the accretion streamer was also detected in the SO2 emission. The observational results arecomplemented by numerical magneto-hydrodynamic simulations, where those large arms only appear in magnetically weakened
clouds. The numerical simulations also suggest that the large triple spiral arms are the result of gravitational interactions
between compact triple protostars and the turbulent infalling envelope.

36. ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): A forming quadruple system with continuum ‘ribbons’ and intricate outflows
Qiu-yi Luo, Tie Liu, Aaron T. Lee, Stella S. R. Offner, James di Francesco, Doug Johnstone, Mika Juvela,
Paul F. Goldsmith, Sheng-Li Qin, Xiaofeng Mai, Xun-chuan Liu, Patricio Sanhueza, Feng-Wei Xu, Ken’ichi
Tatematsu, Somnath Dutta, Huei-Ru Vivien Chen, Shanghuo Li, Aiyuan Yang, Sheng-Yuan Liu, Chin-Fei Lee,
Naomi Hirano, Chang Won Lee, Dipen Sahu, Hsien Shang, Shih-Ying Hsu, Leonardo Bronfman, Woojin Kwon,
M. G. Rawlings, David Eden, Xing Lu, Qi-lao Gu, Zhiyuan Ren, D Ward-Thompson, Zhi-Qiang Shen F One
of the most poorly understood aspects of low-mass star formation is how multiple-star systems are formed. Here we present
the results of Atacama Large Millimeter/submillimeter Array (ALMA) Band-6 observations towards a forming quadruple protostellar system, G206.93-16.61E2, in the Orion B molecular cloud. ALMA 1.3 mm continuum emission reveals four compact
objects, of which two are Class I young stellar objects (YSOs), and the other two are likely in prestellar phase. The 1.3 mm
continuum emission also shows three asymmetric ribbon-like structures that are connected to the four objects, with lengths
ranging from ∼500 au to ∼2200 au. By comparing our data with magneto-hydrodynamic (MHD) simulations, we suggest that11

these ribbons trace accretion flows and also function as gas bridges connecting the member protostars. Additionally, ALMA CO
J=2-1 line emission reveals a complicated molecular outflow associated with G206.93-16.61E2 with arc-like structures suggestiveof an outflow cavity viewed pole-on.

High-resolution SOFIA/EXES Spectroscopy of Water Absorption Lines in the Massive
37. Young Binary W3 IRS 5
Jialu Li, Adwin Boogert, Andrew G. Bar, Curtis DeWitt, Maisie Rashman, David Neufeld, Nick Indriolo,
Yvonne Pendleton, Edward Montiel, Matt Richter, J. E. Chiar, Alexander G. G. Tielens F We present in thispaper mid-infrared (5-8 µm) spectroscopy toward the massive young binary W3 IRS 5, using the EXES spectrometer in highresolution mode (R ∼50,000) from the NASA Stratospheric Observatory for Infrared Astronomy (SOFIA). Many (∼180) ν2 =1–0
and (∼90) ν2 =2-1 absorption rovibrational transitions are identified. Two hot components over 500 K and one warm componentof 190 K are identified through Gaussian fittings and rotation diagram analysis. Each component is linked to a CO component
identified in the IRTF/iSHELL observations (R=88,100) through their kinematic and temperature characteristics. Revealed by
the large scatter in the rotation diagram, opacity effects are important, and we adopt two curve-of-growth analyses, resulting incolumn densities of ∼ 1019 cm−2 . In one analysis, the model assumes a foreground slab. The other assumes a circumstellar disk
with an outward-decreasing temperature in the vertical direction. The disk model is favored because fewer geometry constraints
are needed, although this model faces challenges as the internal heating source is unknown. We discuss the chemical abundancesalong the line of sight based on the CO-to-H2 O connection. In the hot gas, all oxygen not locked in CO resides in water. In
the cold gas, we observe a substantial shortfall of oxygen and suggest that the potential carrier could be organics in solid ice.

Ca II lines as tracers of disk structure in T Tauri Stars: The Chamaeleon I region
38. TheMarbely Micolta, Nuria Calvet, Thanawuth Thanathibodee, Gladis Magris C., María José Colmenares, Jesús
V. Díaz, Jairo Alzate-Trujillo F We present a study of the Ca II K and IR-triplet lines in a sample of Classical T Tauristars in the Chamaeleon I star-forming region. We study X-shooter spectra of the stars in the sample and find that in some ofthese stars the Ca II lines are much weaker than expected from their H line fluxes and mass accretion rate. Since the Ca II K
lines have characteristic magnetospheric accretion line profiles and the magnetospheric flows feed directly from the inner disk,
we interpret the Ca deficit in terms of depletion due to processes happening in the disk. To test this hypothesis, we define acoarse depletion indicator using the flux of the Ca II K line and show that it correlates with disk properties. In particular, using
indicators extracted from Spitzer/IRS spectra, we obtain that all the transitional and pre-transitional disks of the sample show
depletion, consistent with trapping of refractories in pressure bumps created by planets and/or in the planets themselves. We
find full disks with Ca depletion in the sample that also show indications of advanced dust evolution. We apply magnetosphericaccretion models to fit the Balmer and Ca II line fluxes of a star showing clear Ca depletion and derive a Ca abundance in its
inner disk of about 17% solar.

39. Shear, writhe and filaments: turbulence in the high latitude molecular cloud MBM 40

Marco Monaci, Loris Magnani, Steven N. Shore, Henrik Olofsson, Mackenzie R. Joy F Context. It is almost banal
to say that the interstellar medium (ISM) is structurally and thermodynamically complex. But the variety of the governing
processes, including stellar feedback, renders the investigation challenging. High latitude molecular clouds (HLMCs) with noevidence of internal star formation, such as MBM 40, are excellent sites for studying the chemistry and dynamic evolution of thecold neutral ISM. Aims. We used this high latitude cloud as an exemplar for the dynamical and chemical processes in the diffuse
interstellar medium. Methods. We analyzed new and archival 12 CO, 13 CO, CH, HCO+ , CS, H2 CO, HCN data from Five College
Radio Observatory (FCRAO), Onsala Space Observatory (OSO), Arizona Radio Observatory (ARO) and W. Gordon telescope(Arecibo) combined with the Galactic Arecibo L-band Feed Array HI (GALFA-HI) HI 21 cm data set, to study the chemistry,thermal state, and dynamics of MBM 40. A new dynamical analytical approach was adopted by considering each line profile asa line of sight Probability Distribution Function (PDF) of the turbulence weighted by gas emissivity. Results. The atomic andmolecular gas are smoothly distributed in space and velocity. No steep transition is seen between circumcloud atomic and cloud
molecular gas in either radial velocity or structure. We proposed a topology of the cloud from the molecular tracers, a contorted
filamentary structure that is shaped by a broad embedding shear flow in the neutral atomic gas. Comparative examination ofdifferent molecular tracers shows that 13 CO, H2 CO and CS arise from only denser molecular cores, where 12 CO, CH and HCO+
traces diffuse gas with broader range of dynamics.

40. B-fields And dust in interstelLar fiLAments using Dust POLarization (BALLAD-POL):
I. The massive filament G11.11-0.12 observed by SOFIA/HAWC+
Nguyen Bich Ngoc, Pham Ngoc Diep, Thiem Hoang, Le Ngoc Tram, Nguyen Chau Giang, Ngan Le, Thuong
Duc Hoang, Nguyen Thi Phuong, Dieu D. Nguyen, Nguyen Minh Khang, Gia Bao Truong Le F We report the firstmeasurement of polarized thermal dust emission toward the entire early and massive Infrared Dark Cloud G11.11−0.12 taken

12

by the polarimeter SOFIA/HAWC+ at 214 µm wavelength. Magnetic fields (B-fields) obtained from the polarized emission
tend to be perpendicular to the filament’s spine. We produce a map of B-field strengths for the center region of the filament.
The strengths vary in the range of 100-600 µG and are strongest along the filament’s spine. The central region is sub-Alfvénicand mostly sub-critical meaning that B-fields dominate over turbulence and are strong enough to resist gravitational collapse.
The alignment and properties of dust grains are studied in the filament using the RAdiative Torque (RAT) theory. We find thedecrease of polarization degree P with emission intensity I, i.e., depolarization effect, of the form P ∝ I −α with α ∼0.8-0.9,
implying a significant loss of grain alignment in the filament’s spine. The depolarization can be explained by the decreasein RAT alignment efficiency toward the denser regions with lower dust temperature, and cannot be explained by the B-field
tangling. We study the effect of the enhanced magnetic relaxation by embedded iron inclusions on RAT alignment and findthat the high polarization fraction P ∼20-30% in the outer layer of the filament is potential evidence for the enhanced RATalignment by magnetic relaxation. This is the first time this effect is evaluated in a filament. Based on the polarization fraction
and RAT alignment theory, we find evidence for grain growth in the filament.

41. Time series photometry and multi-wavelength characterisation of the young stellar cluster Mon R2
Santiago Orcajo, Lucas A. Cieza, Roberto Gamen F Using the Las Cumbres Observatory Global Telescope Network(LCOGT), we have obtained multi-epoch photometry of the young cluster Mon R2. We have monitored over 6000 sources with
i-band between 13 and 23 mag within a 260 x260 field of view. For each star, we collected ∼ 1500 photometric points coveringa temporal window of 23 days. Based on these data, we have measured rotation-modulated of 136 stars and identified around90 additional variables, including 14 eclipsing binary candidates. Moreover, we found 298 other variables with photometrichigh-scatter. In addition, we have obtained r-band and Hα narrow-band photometry of the cluster with LCOGT and lowresolution optical spectroscopy of 229 stars with GMOS-Gemini. We used the Gaia data from the periodic stars and objects
with Hα or IR-excesses, which are mostly low-mass pre-main sequence stars (< 1Msun ) in the cluster to estimate the distance(825 ± 51 pc) and the mean proper motions (µα cos(δ) = −2.75mas yr−1 and µδ = 1.15mas yr−1 ) of its members. This allows
us to use the Gaia data to identify additional Mon R2 member candidates. We also used Pan-STARRS photometry from our
LCOGT sources to construct a more precise H-R diagram, from which we estimate the mean age of the cluster and identify
other possible members including eleven spectroscopy brown dwarf with M7 to M9 GMOS spectral types. Finally, we combined
our membership lists with Spitzer infrared photometry to investigate the incidence of stars with discs and the effect these haveon stellar rotation.

42. Search and study of ultracompact HII regions
D. Quiroga-Gonzalez, M. A. Trinidad, E. de la Fuente, J. M. Masque, T. Rodriguez-Esnard F We present resultsfrom a sample of 106 high-luminosity IRAS sources observed with the Very Large Array in the B and C configurations. 96
sources were observed in the X-band and 52 in the K-band, with 42 of them observed at both wavelengths. We also usedpreviously published observations in the C-band for 14 of them. The detection rate of sources with 3.6 cm continuum emission
was ∼ 25%, while only 10% have emission at 1.3 cm. In order to investigate the nature of these sources, their physical parameters
were calculated mainly using the 3.6 cm continuum emission, and for sources detected at two wavelengths, we used the best
fit of three HII region models with different geometries. As a final result, we present a catalog of the detected sources, which
includes their basic physical parameters for further analysis. The catalog contains 17 ultracompact HII regions and 3 compact
HII regions.

43. Nitrogen fractionation in ammonia and its insights on nitrogen chemistry
14
15

Elena Redaelli, Luca Bizzocchi, Paola Caselli, Jaime E. Pineda F Context. Observations of N/ N in the interstellar
medium are becoming more frequent thanks to the increased telescope capabilities. However, interpreting these data is still
puzzling. In particular, measurements of 14 N/15 N in diazenylium revealed high levels of anti-fractionation in cold cores. Aims.
Furuya & Aikawa (2018), using astrophysical simulations coupled with a gas-grain chemical code, concluded that the 15 Ndepletion in prestellar cores could be inherited from the initial stages, when 14 N 15 N is selectively photodissociated and 15N
atoms deplete onto the dust grain, forming ammonia ices. We aim to test this hypothesis. Methods. We targeted threesources (the prestellar core L1544, the protostellar envelope IRAS4A, and the shocked region L1157-B1) with distinct degrees ofdesorption or sputtering of the ammonia ices. We observed the NH3 isotopologues with the GBT, and we inferred the 14 N/15 N
via a spectral fitting of the observed inversion transitions. Results. 15 NH3(1,1) is detected in L1544 and IRAS4A, whilst only
upper limits are deduced in L1157-B1. The NH3 isotopic ratio is significantly lower towards the protostar than at the centreof L1544, where it is consistent with the elemental value. We also present the first spatially resolved map of NH3 nitrogenisotopic ratio towards L1544. Conclusions. Our results are in agreement with the hypothesis that ammonia ices are enrichedin 15 N, leading to a decrease of the 14 N/15 N ratio when the ices are sublimated into the gas phase for instance due to thetemperature rise in protostellar envelopes. The ammonia 14 N/15 N value at the centre of L1544 is a factor of 2 lower than that of
N2H+, suggesting that the dominant formation pathway is hydrogenation of N atoms on dust grains, followed by non-thermal

13desorption.

44. Young Stellar Object Candidates in IC 417
L. M. Rebull, R. L. Anderson III, G. Hall, J. D. Kirkpatrick, X. Koenig, C. E. Odden, B. Rodriguez, R. Sanchez,
B. Senson, V. Urbanowski, M. Austin, K. Blood, E. Kerman, J. Long, N. Roosa F IC 417 is in the Galactic Plane,
and likely part of the Aur OB2 association; it is 2 kpc away. Stock 8 is one of the densest cluster constituents; off of it to theEast, there is a ’Nebulous Stream’ (NS) that is dramatic in the infrared (IR). We have assembled a list of literature-identified
young stellar objects (YSOs), new candidate YSOs from the NS, and new candidate YSOs from IR excesses. We vetted thislist via inspection of the images, spectral energy distributions (SEDs), and color-color/color-magnitude diagrams. We placed
the 710 surviving YSOs and candidate YSOs in ranked bins, nearly two-thirds of which have more than 20 points defining their
SEDs. The lowest-ranked bins include stars that are confused, or likely carbon stars. There are 503 in the higher-ranked bins;
half are SED Class III, and ∼40% are SED Class II. Our results agree with the literature in that we find that the NS and Stock
8 are at about the same distance as each other (and as the rest of the YSOs), and that the NS is the youngest region, with Stock
8 a little older. We do not find any evidence for an age spread within the NS, consistent with the idea that the star formation
trigger came from the north. We do not find that the other literature-identified clusters here are as young as either the NS or
Stock 8; at best they are older than Stock 8, and they may not all be legitimate clusters.

The role of magnetic fields in the fragmentation of the Taurus B213 filament into Sun45. type star-forming cores
Anirudh R., Chakali Eswaraiah, Sihan Jiao, Jessy Jose F Fragmentation is a key step in the process of transforming
clouds (and their substructures such as filaments, clumps, and cores) into protostars. The thermal gas pressure and gravitational
collapse are believed to be the primary agents governing this process, referred to as the thermal Jeans fragmentation. However,the contributions of other factors (such as magnetic fields and turbulence) to the fragmentation process remain less explored. In
this work, we have tested possible fragmentation mechanisms by estimating the mean core mass and mean inter-core separationof the B213 filament. We have used the ∼14" resolution James Clerk Maxwell Telescope (JCMT) Submillimetre Common-User
Bolometer Array 2 (SCUBA-2)/POL-2 850 µm dust continuum map and combined it with a Planck 850 µm map and Herscheldata. We find that in addition to the thermal contribution, the presence of ordered magnetic fields could be important in the
fragmentation of the B213 filament.

A panoptic view of the Taurus molecular cloud I. The cloud dynamics revealed by gas
46. emission and 3D dust
J. D. Soler, C. Zucker, J. E. G. Peek, M. Heyer, P. F. Goldsmith, S. C. O. Glover, S. Molinari, R. S. Klessen,
P. Hennebelle, L. Testi, T. Colman, M. Benedettini, D. Elia, C. Mininni, S. Pezzuto, E. Schisano, A. Traficante
F We present a study of the three-dimensional (3D) distribution of interstellar dust derived from stellar extinction observations
toward the Taurus molecular cloud (MC) and its relation with the neutral atomic hydrogen (HI) emission at 21 cm wavelengthand the carbon monoxide 12 CO and 13 CO emission in the J = 1 → 0 transition. We used the histogram of oriented gradients(HOG) method to match the morphology in a 3D reconstruction of the dust density (3D dust) and the distribution of the gas
tracers’ emission. The result of the HOG analysis is a map of the relationship between the distances and radial velocities. The
HOG comparison between the 3D dust and the HI emission indicates a morphological match at the distance of Taurus but
an anti-correlation between the dust density and the HI emission, which uncovers a significant amount of cold HI within the
Taurus MC. The HOG between the 3D dust and 12 CO reveals a pattern in radial velocities and distances that is consistent
with converging motions of the gas in the Taurus MC, with the near side of the cloud moving at higher velocities and the far
side moving at lower velocities. This convergence of flows is likely triggered by the large-scale gas compression caused by theinteraction of the Local Bubble and the Per-Tau shell, with Taurus lying at the intersection of the two bubble surfaces.

47. Broadband VLA Spectral Line Survey of a Sample of Ionized Jet Candidates
E. Sanchez-Tovar, E. D. Araya, V. Rosero, P. Hofner, S. Kurtz F The study of the interaction between ionized jets,
molecular outflows and their environments is critical to understanding high-mass star formation, especially because jets andoutflows are thought to be key in the transfer of angular momentum outwards from accretion disks. We report a low-spectral
resolution VLA survey for hydrogen radio recombination lines, OH, NH3 , and CH3 OH lines toward a sample of 58 high-massstar forming regions that contain numerous ionized jet candidates. The observations are from a survey designed to detect
radio continuum; the novel aspect of this work is to search for spectral lines in broadband VLA data (we provide the script
developed in this work to facilitate exploration of other datasets). We report detection of 25 GHz CH3 OH transitions toward
ten sources; five of them also show NH3 emission. We found that most of the sources detected in CH3 OH and NH3 have beenclassified as ionized jets or jet candidates and that the emission lines are coincident with, or very near (. 0.1 pc) these sources,
hence, these molecular lines could be used as probes of the environment near the launching site of jets/outflows. No radio14

recombination lines were detected, but we found that the RMS noise of stacked spectra decreases following the radiometerequation. Therefore, detecting radio recombination lines in a sample of brighter free-free continuum sources should be possible.
This work demonstrates the potential of broadband VLA continuum observations as low-resolution spectral line scans.

Planetesimal formation at the gas pressure bump following a migrating planet II. Effects
48. of dust growth
Yuhito Shibaike, Yann Alibert F Planetesimal formation is still mysterious. One of the ways to form planetesimals is to
invoke a gas pressure bump in a protoplanetary disc. In our previous paper, we propose a new scenario in which the piled-up dust
at a gas pressure bump created by a migrating planet form planetesimals by streaming instability in a wide region of the disc as
the planet migrates inward. In this work, we consider the global time evolution of dust and investigate the detailed conditions
and results of the planetesimal formation in our scenario. We use a 1D grid single-sized dust evolution model, which can follow
the growth of the particles by their mutual collision and their radial drift and diffusion. We calculate the time-evolution of theradial distribution of the peak mass and surface density of the dust in a gas disc perturbed by an embedded migrating planet
and investigate if the dust satisfies the condition for planetesimal formation. We find that planetesimals form in a belt-likeregion between the snowline and the position where the planet reaches its pebble-isolation mass when the strength of turbulence
is 10−4 ≤ α ≤ 10−3 , which is broadly consistent with observed value. The mechanism of the formation, streaming instability or
mutual collision, depends on the timescale of the streaming instability. The total mass of planetesimals also depends on α andis about 30 − 100 ME if the planetary core has already existed at the beginning and grows by gas accretion, but it decreases
as the timing of the formation of the planetary core is later. We also provide simple approximate expressions of the surface
density and total mass of the planetesimals and find that the total mass strongly depends on the dust mass. We show thatplanetesimals form in a belt-like region by the combination of the dust pile-up at the gas pressure bump formed by a planet
and its inward migration.

49. Anisotropic Ionizing Illumination from an M-type Pre-main Sequence Star, DM Tau

Yuka Terada, Hauyu Baobab Liu, David Mkrtichian, Jinshi Sai, Mihoko Konishi, Ing-Guey Jiang, Takayuki
Muto, Jun Hashimoto, Motohide Tamura F The powerful, high-energy magnetic activities of young stars play importantroles in the magnetohydrodynamics in the innermost parts of the protoplanetary disks. In addition, the associated UV and
X-ray emission dictates the photochemistry; moreover, the corona activities can affect the atmosphere of a newborn extra-solar
planet. How the UV and X-ray photons are generated, and how they illuminate the disks, are not well understood. Here
we report the analyses of the optical and infrared (OIR) photometric monitoring observations and the high angular-resolution
centimeter band images of the low-mass (M1 type) pre-main sequence star, DM Tau. We found that the OIR photometric light
curves present periodic variations, which is consistent with that the host young star is rotating in the same direction as the natal
disk and is hosting at least one giant cold spot. In addition, we resolved that the ionized gas in the DM Tau disk is localized,
and its spatial distribution is varying with time. All the present observations can be coherently interpreted, if the giant cold
spot is the dominant anisotropic UV and/or X-ray source that illuminates the ambient cone-like region. These results indicatethat a detailed theoretical model of the high-energy protostellar emission is essential in the understanding of the space weather
around the extra-solar planets and the origin of life.

50. A Chondritic Solar Neighborhood

Isabella L. Trierweiler, Alexandra E. Doyle, Edward D. Young F A persistent question in exoplanet demographics
is whether exoplanetary systems form from similar compositional building blocks to our own. Polluted white dwarf stars offer
a unique way to address this question as they provide measurements of the bulk compositions of exoplanetary material. We
present a statistical analysis of the rocks polluting oxygen-bearing white dwarfs and compare their compositions to rocks in
the Solar System. We find that the majority of the extrasolar rocks are consistent with the composition of typical chondrites.
Measurement uncertainties prevent distinguishing between chondrites and bulk Earth, but do permit detecting the differences
between chondritic compositions and basaltic or continental crust. We find no evidence of crust amongst the polluted whitedwarfs. We show that the chondritic nature of extrasolar rocks is also supported by the compositions of local stars. Whilegalactic chemical evolution results in variations in the relative abundances of rock-forming elements spatially and temporally
on galaxy-wide scales, the current sample of polluted white dwarfs are sufficiently young and close to Earth that they are notaffected by this process. We conclude that exotic compositions are not required to explain the majority of observed rock types
around polluted white dwarfs, and that variations between exoplanetary compositions in the stellar neighborhood are generally
not due to significant differences in the initial composition of protoplanetary disks. Nonetheless, there is evidence from stellar
observations that planets formed in the first several billion years in the Galaxy have lower metal core fractions compared with
Earth on average.

15

51. Excited Hydroxyl Outflow in the High-Mass Star-Forming Region G34.26+0.15

W. S. Tan, E. D. Araya, C. Rigg, P. Hofner, S. Kurtz, H. Linz, V. Rosero F G34.26+0.15 is a region of high-massstar formation that contains a broad range of young stellar objects in different stages of evolution, including a hot molecularcore, hyper-compact HII regions and a prototypical cometary ultra-compact HII region. Previous high-sensitivity single dishobservations by our group resulted in the detection of broad 6035 MHz OH absorption in this region; the line showed a significant
blue-shifted asymmetry indicative of molecular gas expansion. We present high-sensitivity Karl G. Jansky Very Large Array(VLA) observations of the 6035 MHz OH line conducted to image the absorption and investigate its origin with respect to thedifferent star formation sites in the region. In addition, we report detection of 6030 MHz OH absorption with the VLA andfurther observations of 4.7 GHz and 6.0 GHz OH lines obtained with the Arecibo Telescope. The 6030 MHz OH line shows avery similar absorption profile as the 6035 MHz OH line. We found that the 6035 MHz OH line absorption region is spatiallyunresolved at ∼ 2" scales, and it is coincident with one of the bright ionized cores of the cometary HII region that shows
broad radio recombination line emission. We discuss a scenario where the OH absorption is tracing the remnants of a pole-on
molecular outflow that is being ionized inside-out by the ultra-compact HII region.

52.

X-Shooting ULLYSES: massive stars at low metallicity. I. Project Description
Jorick S. Vink and the ULLYSES Team F Observations of individual massive stars, super-luminous supernovae, gammaray bursts, and gravitational-wave events involving spectacular black-hole mergers, indicate that the low-metallicity Universe
is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm
understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted
500 orbits to observe 250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the
ULLYSES program. The complementary “X-Shooting ULLYSES” (XShootU) project provides enhanced legacy value withhigh-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO’s
Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU
optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity,
luminosity, and abundances, as well as wind properties such as mass-loss rates in function of Z. As uncertainties in stellar andwind parameters percolate into many adjacent areas of Astrophysics, the data and modelling of the XShootU project is expected
to be a game-changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb
Space Telescope (JWST) spectra of the first stellar generations, the individual spectra of low Z stars need to be understood,
which is exactly where XShootU can deliver.

53. A high-resolution extinction mapping technique for face-on disc galaxies

Helena Faustino Vieira, Ana Duarte-Cabral, Timothy A. Davis, Nicolas Peretto, Matthew W. L. Smith, MiguelQuerejeta, Dario Colombo, Michael Anderson F We present a new dust extinction technique with which we are able toretrieve parsec-scale gas surface density maps for entire nearby galaxies. The method measures the dust attenuation in opticalbands on a pixel-by-pixel basis against a smoothed, reconstructed stellar distribution. The contribution of foreground light along
the line-of-sight is calibrated using dust emission observations, assuming that the dust sits in a layer close to the mid-plane of
the face-on galaxy. Here, we apply this technique to M51 (NGC 5194) as a proof-of-concept, obtaining a resolution of 0.14" (5pc). Our dust (and gas) surface density map is consistent with independent dust- and CO-based studies at lower resolution. We
find that discrepancies between our estimates of surface density and other studies stem primarily from the choice of dust model(i.e. different dust absorption coefficients). When assuming the same dust opacity law, our technique produces surface densities
that are consistent with independent studies. This dust extinction technique provides us with gas surface density maps at an
unprecedented resolution for full disc coverage studies of nearby galaxies. The resulting well-resolved spatial information opens
the possibility for more in-depth examination of the influence of large-scale dynamics (and also stellar feedback mechanisms)
on the interstellar medium at parsec-scales, and consequently star formation in nearby galaxies.

16

BEAST detection of a brown dwarf and a low-mass stellar companion around the young
54. bright B star HIP 81208
Gayathri Viswanath, Markus Janson, Raffaele Gratton, Vito Squicciarini, Laetitia Rodet, Simon C. Ringqvist,
Eric E. Mamajek, Sabine Reffert, Gaël Chauvin, Philippe Delorme, Arthur Vigan, Mickaël Bonnefoy, Natalia
Engler, Silvano Desidera, Thomas Henning, Janis Hagelberg, Maud Langlois, Michael Meyer F Recent observations from B-star Exoplanet Abundance Study (BEAST) have illustrated the existence of sub-stellar companions around very
massive stars. In this paper, we present the detection of two lower mass companions to a relatively nearby (148.7+1.5−1.3 pc),
young (17+3
B9V star HIP 81208 residing in the Sco-Cen association,−4 Myr), bright (V=6.632 ± 0.006 mag), 2.58 ± 0.06 M
using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope (VLT) in+0.010Chile. Analysis of the photometry obtained gives mass estimates of 67+6
for
−7 MJ for the inner companion and 0.135−0.013 M
the outer companion, indicating the former to be most likely a brown dwarf and the latter to be a low-mass star. The system
is compact but unusual, as the orbital planes of the two companions are likely close to orthogonal. The preliminary orbital
solutions we derived for the system indicate that the star and the two companions are likely in a Kozai resonance, rendering
the system dynamically very interesting for future studies.

55. Dynamical detection of a companion driving a spiral arm in a protoplanetary disk

Chen Xie, Bin B. Ren, Ruobing Dong, Élodie Choquet, Arthur Vigan, Jean-François Gonzalez, Kevin Wagner,
Taotao Fang, Maria Giulia Ubeira-Gabellini F Radio and near-infrared observations have observed dozens of protoplanetary disks that host spiral arm features. Numerical simulations have shown that companions may excite spiral density waves
in protoplanetary disks via companion-disk interaction. However, the lack of direct observational evidence for spiral-driving
companions poses challenges to current theories of companion-disk interaction. Here we report multi-epoch observations of
the binary system HD 100453 with the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) facility at the Very
Large Telescope. By recovering the spiral features via robustly removing starlight contamination, we measure spiral motion
across 4 yr to perform dynamical motion analyses. The spiral pattern motion is consistent with the orbital motion of theeccentric companion. With this first observational evidence of a companion driving a spiral arm among protoplanetary disks,
we directly and dynamically confirm the long-standing theory on the origin of spiral features in protoplanetary disks. With thepattern motion of companion-driven spirals being independent of companion mass, here we establish a feasible way of searchingfor hidden spiral-arm-driving planets that are beyond the detection of existing ground-based high-contrast imagers.

observational evidence of the multi-scale, dynamical mass accretion toward a
56. Direct
high-mass star forming hub-filament system
Dongting Yang, Hong-Li Liu, Anandmayee Tej, Tie Liu, Patricio Sanhueza, Sheng-Li Qin, Xing Lu, Ke Wang,
Sirong Pan, Feng-Wei Xu, Enrique Vazquez-Semadeni, Shanghuo Li, Gilberto C. Gomez, Aina Palau, Guido
Garay, Paul F. Goldsmith, Mika Juvela, Anindya Saha, Leonardo Bronfman, Chang Won Lee, Kenichi Tatematsu, Lokesh Dewangan, Jianwen Zhou, Yong Zhang, Amelia Stutz, Chakali Eswaraiah, L. Viktor Toth, Isabelle
Ristorcelli, Xianjin Shen, Anxu Luo, James O. Chibueze F There is growing evidence that high-mass star formationand hub-filament systems (HFS) are intricately linked. The gas kinematics along the filaments and the forming high-massstar(s) in the central hub are in excellent agreement with the new generation of global hierarchical high-mass star formation
models. In this paper, we present an observational investigation of a typical HFS cloud, G310.142+0.758 (G310 hereafter)
which reveals unambiguous evidence of mass inflow from the cloud scale via the filaments onto the forming protostar(s) at the
hub conforming with the model predictions. Continuum and molecular line data from the ATOMS and MALT90 surveys areused that cover different spatial scales. Three filaments (with total mass 5.7 ± 1.1 × 103 M ) are identified converging toward
the central hub region where several signposts of high-mass star formation have been observed. The hub region contains a
massive clump (1280 ± 260 M ) harbouring a central massive core. Additionally, five outflow lobes are associated with thecentral massive core implying a forming cluster. The observed large-scale, smooth and coherent velocity gradients from thecloud down to the core scale, and the signatures of infall motion seen in the central massive clump and core, clearly unveil anearly-continuous, multi-scale mass accretion/transfer process at a similar mass infall rate of ∼ 10−3 M yr−1 over all scales,feeding the central forming high-mass protostar(s) in the G310 HFS cloud.

in Compact Disks of the Taurus Star-forming Region
57. Substructures
Shangjia Zhang, Matt Kalscheur, Feng Long, Ke Zhang, Deryl E. Long, Edwin A. Bergin, Zhaohuan Zhu, Leon
Trapman F Observations of substructure in protoplanetary disks have largely been limited to the brightest and largest disks,
excluding the abundant population of compact disks which are likely sites of planet formation. Here, we reanalyze 0.1”, 1.33
mm ALMA continuum observations of 12 compact protoplanetary disks in the Taurus star-forming region. By fitting visibilities
directly, we identify substructures in 6 of the 12 compact disks. We then compare the substructures identified in the full Taurus
sample of 24 disks in single star systems and the ALMA DSHARP survey, differentiating between compact (Ref f ,90% < 50 au)
and extended (Ref f ,90% > 50 au) disk sources. We find that substructures are detected at nearly all radii in both small and17large disks. Tentatively, we find fewer wide gaps in intermediate-sized disks with Ref f ,90% between 30 and 90 au. We perform
a series of planet-disk interaction simulations to constrain the sensitivity of our visibility-fitting approach. Under an assumptionof planet-disk interaction, we use the gap widths and common disk parameters to calculate potential planet masses within the
Taurus sample. We find that the young planet occurrence rate peaks near Neptune masses, similar to the DSHARP sample. For
0.01 MJ /M . Mp /M∗ . 0.1 MJ /M , the rate is 17.4±8.3%; for 0.1 MJ /M . Mp /M∗ . 1 MJ /M , it is 27.8±8.3%. Bothof them are consistent with microlensing surveys. For gas giants more massive than 5 MJ , the occurrence rate is 4.2±4.2%,
consistent with direct imaging surveys.

Dust Particles in Protoplanetary Disks: Application to the HL Tau Disk
58. Porous
Shangjia Zhang, Zhaohuan Zhu, Takahiro Ueda, Akimasa Kataoka, Anibal Sierra, Carlos Carrasco-González,Enrique Macías F Dust particle sizes constrained from dust continuum and polarization observations by radio interferometry
are inconsistent by at least an order of magnitude. Motivated by porous dust observed in small Solar System bodies (e.g., fromthe Rosetta mission), we explore how the dust particle’s porosity affects the estimated particle sizes from these two methods.
Porous particles have lower refractive indices, which affect both opacity and polarization fraction. With weaker Mie interference
patterns, the porous particles have lower opacity at mm wavelengths than the compact particles if the particle size exceeds
several hundred microns. Consequently, the inferred dust mass using porous particles can be up to a factor of six higher. The
most significant difference between compact and porous particles is their scattering properties. The porous particles have awider range of particle sizes with high linear polarization from dust self-scattering, allowing mm-cm-sized particles to explain
polarization observations. With a Bayesian approach, we use porous particles to fit HL Tau disk’s multi-wavelength continuum
and mm-polarization observations from ALMA and VLA. The moderately porous particles with sizes from 1 mm-1 m can explain
both continuum and polarization observations, especially in the region between 20-60 au. If the particles in HL Tau are porous,
the porosity should be from 70% to 97% from current polarization observations. We also predict that future observations of theself-scattering linear polarization at longer wavelengths (e.g., ALMA B1 and ngVLA) have the potential to further constrain
the particle’s porosity and size.

18