The Star Formation Newsletter
A community newsletter on Star and Planet Formation research 27 December 2021
Editor: João Alves
No. 348www.starformation.news

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Cover image caption
The NGC 2264 cluster, at a distance of about 700 pc from Earth, played an important role in early star formation studies. Here

"The occurrence of T Tauri stars in the cluster and theirlocation in the color-magnitude diagram indicate that stars of this type are extremely young and are still in the gravitational
contraction state. Whether the T Tauri phenomenon represents a necessary stage in the gravitational contraction of all newly
formed stars cannot be determined from the present observations." Image credit: (B, V, R, and H-alpha) with the Wide Field
is an enlightening extract from Merle Walker's classic 1956 paper:

Imager at ESO's La Silla Observatory. The image shows a region of space about ten pc across.

Note from the Editor
The Star Formation Newsletter is now on the web atwww.starformation.news. This PDF le contains the monthly Abstracts

and links to the dierent Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to the SFN is as simple

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.
as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site.

Abstractsof a New Population of Galactic HII Regions with Ionized Gas Velocity
1. Discovery
Gradients
Dana S. Balser, Trey V. Wenger, L. D. Anderson, W. P. Armentrout, T. M. Bania, J. R. Dawson, John M.
Dickey F We investigate the kinematic properties of Galactic HII regions using radio recombination line (RRL) emission

detected by the Australia Telescope Compact Array (ATCA) at 4-10 GHz and the Jansky Very Large Array (VLA) at 8-10
GHz.

Our HII region sample consists of 425 independent observations of 374 nebulae that are relatively well isolated fromother, potentially confusing sources and have a single RRL component with a high signal-to-noise ratio. We perform Gaussian
ts to the RRL emission in position-position-velocity data cubes and discover velocity gradients in 178 (42%) of the nebulaewith magnitudes between 5 and 200 m/s/arcsec. About 15% of the sources also have a RRL width spatial distribution thatpeaks toward the center of the nebula. The velocity gradient position angles appear to be random on the sky with no favoredorientation with respect to the Galactic Plane.

We craft HII region simulations that include bipolar outows or solid bodyrotational motions to explain the observed velocity gradients. The simulations favor solid body rotation since, unlike the bipolaroutow kinematic models, they are able to produce both the large, > 40 m/s/arcsec, velocity gradients and also the RRL width
structure that we observe in some sources. The bipolar outow model, however, cannot be ruled out as a possible explanation
for the observed velocity gradients for many sources in our sample. We nevertheless suggest that most HII region complexes
are rotating and may have inherited angular momentum from their parent molecular clouds.

2. Investigating the structure of star-forming regions using INDICATE

George A. Blaylock-Squibbs, Richard J. Parker, Anne S. M. Buckner, Manuel Guedel F The ability to makemeaningful comparisons between theoretical and observational data of star-forming regions is key to understanding the starformation process. In this paper we test the performance of INDICATE, a new method to quantify the clustering tendencies
of individual stars in a region, on synthetic star-forming regions with sub-structured, and smooth, centrally concentrated
distributions. INDICATE quanties the amount of stellar aliation of each individual star, and also determines whether thisaliation is above random expectation for the star-forming region in question.

We show that INDICATE cannot be used

to quantify the overall structure of a region due to a degeneracy when applied to regions with dierent geometries. We test
the ability of INDICATE to detect dierences in the local stellar surface density and its ability to detect and quantify masssegregation. We then compare it to other methods such as the mass segregation ratio ΛMSR , the local stellar surface density ratio

2ΣLDR and the cumulative distribution of stellar positions. INDICATE detects signicant dierences in the clustering tendenciesof the most massive stars when they are at the centre of a smooth, centrally concentrated distribution, corresponding to areasof greater stellar surface density. When applied to a subset of the 50 most massive stars we show INDICATE can detect signals
of mass segregation. We apply INDICATE to the following nearby star-forming regions: Taurus, ONC, NGC 1333, IC 348 andρ Ophiuchi and nd a diverse range of clustering tendencies in these regions.

3. Probing inner and outer disk misalignments in transition disksA. J. Bohn, M. Benisty, K. Perraut, N. van der Marel, L. Wölfer, E. F. van Dishoeck, S. Facchini, C. F.
Manara, R. Teague, L. Francis, J-P. Berger, R. Garcia-Lopez, C. Ginski, T. Henning, M. Kenworthy, S. Kraus,
F. Ménard, A. Mérand, L. M. Pérez F For several transition disks (TDs), dark regions interpreted as shadows have been
observed in scattered light imaging and are hypothesized to originate from misalignments between distinct disk regions. We
aim to investigate the presence of misalignments in TDs. We study the inner disk geometries of 20 well-known transition disks
1213with VLTI/GRAVITY observations and use complementary
CO andCO molecular line data from ALMA to derive theorientation of the outer disk regions.

We t simple models to the GRAVITY data to derive the inner disks inclination andposition angles. The outer disk geometries were derived from Keplerian ts to the ALMA velocity maps and compared to theinner disk constraints. We also predicted the locations of shadows for signicantly misaligned systems. Our analysis reveals six
disks to exhibit signicant misalignments between their inner and outer disks. The predicted shadow positions agree well withthe scattered light images of HD100453 and HD142527, and we nd supporting evidence for a shadow in the disk around CQTau. In the other three targets for which we infer signicantly misaligned disks, V1247 Ori, V1366 Ori, and RY Lup, we do notsee any evident sign of shadows in the scattered light images. The scattered light shadows observed in DoAr44, HD135344B,
and HD139614 are consistent with our observations, yet the underlying morphology is likely too complex to be described byour models and the accuracy achieved by our observations. Whereas we can derive precise constraints on the potential shadow
positions for well-resolved inner disks around HAeBe stars, the statistical uncertainties for the marginally resolved inner disks
around the TTS of our sample make it dicult to extract conclusive constraints for the presence of shadows in these systems.

Enlightening the chemistry of infalling envelopes and accretion disks around Sun-like

4. protostars: the ALMA FAUST project

C. Codella, C. Ceccarelli, C. Chandler N. Sakai, S. Yamamoto, the FAUST team F The huge variety of planetarysystems discovered in recent decades likely depends on the early history of their formation. In this contribution we introduce
the FAUST Large Program, which focuses specically on the early history of Solar-like protostars and their chemical diversity at
scales of ∼ 50 au, where planets are expected to form. In particular, the goal of the project is to reveal and quantify the varietyof chemical composition of the envelope/disk system at scales of 50 au in a sample of Class 0 and I protostars representativeof the chemical diversity observed at larger scales. For each source, we propose a set of molecules able to: (1) disentangle thecomponents of the 50-2000 au envelope/disk system; (2) characterise the organic complexity in each of them; (3) probe their
ionization structure; (4) measure their molecular deuteration.

The output will be a homogeneous database of thousands ofimages from dierent lines and species, i.e., an unprecedented source-survey of the chemical diversity of Solar-like protostars.
FAUST will provide the community with a legacy dataset that will be a milestone for astrochemistry and star formation studies.

Physical Properties of the SVS 13 Protobinary System: Two Circumstellar Disks
5. Theand a Spiraling Circumbinary Disk in the Making

Ana K. Diaz-Rodriguez, Guillem Anglada, Guillermo Blázquez-Calero, Mayra Osorio, José F. Gómez, Gary A.
Fuller, Robert Estalella, José M. Torrelles, Sylvie Cabrit, Luis F. Rodríguez, Charlène Lefèvre, Enrique Macías,
Carlos Carrasco-González, Luis A. Zapata, Itziar de Gregorio-Monsalvo, Paul T. P. Ho F We present VLA and
ALMA observations of the close (0.3" = 90 au separation) protobinary system SVS 13. We detect two small circumstellar disks(radii ∼12 and ∼9 au in dust, and ∼30 au in gas) with masses of ∼0.004-0.009 Msun for VLA 4A (the western component) and∼0.009-0.030 Msun for VLA 4B (the eastern component). A circumbinary disk with prominent spiral arms extending ∼500 au
and a mass of ∼0.052 Msun appears to be in the earliest stages of formation. The dust emission is more compact and witha very high optical depth toward VLA 4B, while toward VLA 4A the dust column density is lower, allowing the detection ofstronger molecular transitions. We infer rotational temperatures of ∼140 K, on scales of ∼30 au, across the whole source, and arich chemistry. Molecular transitions typical of hot corinos are detected toward both protostars, being stronger toward VLA 4A,
with several ethylene glycol transitions detected only toward this source. There are clear velocity gradients, that we interpretin terms of infall plus rotation of the circumbinary disk, and purely rotation of the circumstellar disk of VLA 4A. We measured
orbital proper motions and determined a total stellar mass of 1 Msun . From the molecular kinematics we infer the geometry
and orientation of the system, and stellar masses of ∼0.26 Msun for VLA 4A and ∼0.60 Msun for VLA 4B.

3

6. The JCMT BISTRO Survey: Evidence for Pinched Magnetic Fields in Quiescent Fila-

ments of NGC 1333

Yasuo Doi, Kohji Tomisaka, Tetsuo Hasegawa, Simon Coudé, Doris Arzoumanian, Pierre Bastien, Masafumi
Matsumura, Mehrnoosh Tahani, Sarah Sadavoy, Charles L. H. Hull, Doug Johnstone, James Di Francesco,
Yoshito Shimajiri, Ray S. Furuya, Jungmi Kwon, Motohide Tamura, Derek Ward-Thompson, Valentin J. M.
Le Gouellec, Thiem Hoang, Florian Kirchschlager, Jihye Hwang, Chakali Eswaraiah, Patrick M. Koch, Anthony
P. Whitworth, Kate Pattle, Woojin Kwon, Jihyun Kang, Shu-ichiro Inutsuka, Tyler L. Bourke, Xindi Tang,
Lapo Fanciullo, Chang Won Lee, Hong-Li Liu, A-Ran Lyo, Keping Qiu, Shih-Ping Lai F We investigate theinternal 3D magnetic structure of dense interstellar laments within NGC 1333 using polarization data at 850µm from theB -elds In STar-forming Region Observations survey at the James Clerk Maxwell Telescope. Theoretical models predict thatthe magnetic eld lines in a lament will tend to be dragged radially inward (i.e., pinched) toward the central axis due tothe lament's self-gravity. We study the cross-sectional proles of the total intensity (I ) and polarized intensity (PI) of dust
emission in four segments of laments unaected by local star formation that are expected to retain a pristine magnetic eldstructure.

We nd that the laments' FWHM in PI are not the same as those in I , with two segments being appreciably

narrower in PI (FWHM ratio ' 0.7 − 0.8) and one segment being wider (FWHM ratio ' 1.3). The lament proles of thepolarization fraction (P ) do not show a minimum at the spine of the lament, which is not in line with an anticorrelation
between P and I normally seen in molecular clouds and protostellar cores. Dust grain alignment variation with density cannot
reproduce the observed P distribution. We demonstrate numerically that the I and PI cross-sectional proles of laments inmagnetohydrostatic equilibrium will have diering relative widths depending on the viewing angle.

The observed variationsof FWHM ratios in NGC 1333 are therefore consistent with models of pinched magnetic eld structures inside laments, andespecially if they are magnetically near-critical or supercritical.

survey for variable young stars with small telescopes: V - Analysis of TXOri, V505Ori,
7. A
and V510Ori, the HST ULLYSES targets in the σOri cluster

Dirk Froebrich, Jochen Eislöel, Bringfried Stecklum, Carys Herbert, Franz-Josef Hambsch F Investigations of

the formation of young stellar objects (YSOs) and planets require the detailed analysis of individual sources as well as statisticalanalysis of a larger number of objects.

The Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES)

project provides such a unique opportunity by establishing a UV spectroscopic library of young high- and low-mass stars in
the local universe. Here we analyse optical photometry of the three ULLYSES targets (TXOri, V505Ori, V510Ori) and otherYSOs in the σ Ori cluster taken at the time of the HST observations to provide a reference for those spectra. We identify three
populations of YSOs along the line of sight to σ Ori, separated in parallax and proper motion space. The ULLYSES targets show
−8
typical YSO behaviour with pronounced variability and mass accretion rates of the order of 10
M /yr. Optical colours do notagree with standard interstellar reddening and suggest a signicant contribution of scattered light. They are also amongst themost variable and strongest accretors in the cluster. V505 Ori shows variability with a seven day period, indicating an inner disk
warp at the co-rotation radius. Uncovering the exact nature of the ULLYSES targets will require improved detailed modellingof the HST spectra in the context of the available photometry, including scattered light contributions as well as non-standard
reddening.

8. Quantifying the chemical desorption of H2 S and PH3 from amorphous water ice surfaces
Kenji Furuya, Yasuhiro Oba, Takashi Shimonishi F Nonthermal desorption of molecules from icy grain surfaces is required
to explain molecular line observations in the cold gas of star-forming regions. Chemical desorption is one of the nonthermal
desorption processes and is driven by the energy released by chemical reactions. After an exothermic surface reaction, the excessenergy is transferred to products' translational energy in the direction perpendicular to the surface, leading to desorption. The
desorption probability of product species, especially that of product species from water ice surfaces, is not well understood.
This uncertainty limits our understanding of the interplay between gas-phase and ice surface chemistry. In the present work, weconstrain the desorption probability of H2 S and PH3 per reaction event on porous amorphous solid water (ASW) by numericallysimulating previous laboratory experiments. Adopting the microscopic kinetic Monte Carlo method, we nd that the desorption
probabilities of H2 S and PH3 from porous ASW per hydrogen addition event of the precursor species are 3 ± 1.5% and 4 ± 2%,
respectively.

These probabilities are consistent with a theoretical model of chemical desorption proposed in the literature if∼7% of energy released by the reactions is transferred to the translational excitation of the products. As a byproduct, we ndthat approximately 70% (40%) of adsorption sites for atomic H on porous ASW should have a binding energy lower than ∼300
K (∼200 K). The astrochemical implications of our ndings are briey discussed.

4

images of two wiggling stellar jets, MHO 1502 and MHO 2147, obtained
9. High-resolution
with GSAOI+GeMS

L. V. Ferrero, G. Günthardt, L. García, M. Gómez, V. M. Kalari, H. P. Saldaño F We investigated the possible
cause-eect relation between the wiggling shape of two stellar jets, MHO 1502 and MHO 2147, and the potential binarity of therespective driving stars. We present high-angular-resolution H2 (2.122 µm) and K-band images obtained with the Gemini South
Adaptive Optics Imager (GSAOI) and the Gemini Multi-conjugate Adaptive Optics System (GeMS). The proles of the jets are
depicted in detail by the H2 images. We used K-band data to search for potential close companions to the previously suggested
exciting sources, and used archive data to investigate these sources and the environments in which the jets are located. We
also applied a model to reproduce the wiggling proles of the jets. MHO 1502 is composed of a chain of knots delineating the
wiggling jet, suggesting that the driving source emitted them in an intermittent manner. Our K-band image of the previously
proposed exciting star, IRAC 18064, shows two sources separated by ∼ 240 AU, hinting at its binarity. However, as IRAC 18064
is located o the jet axis at ∼ 2064 AU, it is questionable as to whether this source is the true exciting star. Moreover, theorbital model centred on IRAC 18064 suggests a binary companion at a much greater distance (∼ 2200 AU) than the nearby

star (at ∼240 AU). On the other hand, the orbital model centred on the axis provides the best ts. Nevertheless, the precession
2
model centred on the axis cannot be discarded, despite having larger residuals and χ . MHO 2147 displays an S-shaped gentle
continuous emission in H2 . We identify two other jets in the eld of MHO 2147: a previously reported quasi-perpendicular jet,
MHO 2148, and a third jet adjacent to MHO 2147. The model that best ts the morphology of the MHO 2147 jet and that ofits adjacent jet is precession. The exciting source of MHO 2147 may be a triple system.

10. Gaia 20eae: A newly discovered episodically accreting young star

Arpan Ghosh, Saurabh Sharma, Joe. P. Ninan, Devendra K. Ojha, Bhuwan C. Bhatt, Shubham Kanodia,
Suvrath Mahadevan, Gudmundur Stefansson, R. K. Yadav, A. S. Gour, Rakesh Pandey, Tirthendu Sinha,
Neelam Panwar, John P. Wisniewski, Caleb I. Canas, Andrea S. J. Lin, Arpita Roy, Fred Hearty, Lawrence
Ramsey, Paul Robertson, Christian Schwab F The Gaia Alert System issued an alert on 2020 August 28, on Gaia 20eae
when its light curve showed a ∼4.25 magnitude outburst. We present multi-wavelength photometric and spectroscopic follow-up

observations of this source since 2020 August and identify it as the newest member of the FUor/EXor family of sources. We ndthat the present brightening of Gaia 20eae is not due to the dust clearing event but due to an intrinsic change in the spectralenergy distribution. The light curve of Gaia 20eae shows a transition stage during which most of its brightness (∼3.4 mag) has
occurred at a short timescale of 34 days with a rise-rate of 3 mag/month. Gaia 20eae has now started to decay at a rate of 0.3
mag/month. We have detected a strong P Cygni prole in Hα which indicates the presence of winds originating from regions
close to the accretion. We nd signatures of very strong and turbulent outow and accretion in Gaia 20eae during this outburst
phase.

We have also detected a red-shifted absorption component in all the Ca II IR triplet lines consistent with signatureof hot in-falling gas in the magnetospheric accretion funnel.

This enables us to constrain the viewing angle with respect tothe accretion funnel. Our investigation of Gaia 20eae points towards magnetospheric accretion being the phenomenon for thecurrent outburst.

11. The density structure of supersonic self-gravitating turbulence

Shivan Khullar, Christoph Federrath, Mark R. Krumholz, Christopher D. Matzner F We conduct numericalexperiments to determine the density probability distribution function (PDF) produced in supersonic, isothermal, self-gravitating
turbulence of the sort that is ubiquitous in star-forming molecular clouds. Our experiments cover a wide range of turbulent
Mach number and virial parameter, allowing us for the rst time to determine how the PDF responds as these parameters vary,
and we introduce a new diagnostic, the dimensionless star formation eciency versus density (ff (s)) curve, which provides asensitive diagnostic of the PDF shape and dynamics. We show that the PDF follows a universal functional form consisting ofa log-normal at low density with two distinct power law tails at higher density; the rst of these represents the onset of selfgravitation, and the second reects the onset of rotational support. Once the star formation eciency reaches a few percent,the PDF becomes statistically steady, with no evidence for secular time-evolution at star formation eciencies from about ve
to 20 percent. We show that both the Mach number and the virial parameter inuence the characteristic densities at which the
log-normal gives way to the rst power-law, and the rst to the second, and we extend (for the former) and develop (for thelatter) simple theoretical models for the relationship between these density thresholds and the global properties of the turbulent
medium.

5

Young Stellar Population, Distance, and Cloud-Cloud Collision Induced Star For12. The
mation Scenario of the Trid Nebula
Venu M. Kalari F The Trid Nebula is a young, nearby star-forming region where star formation is proposed to have been
triggered by cloud-cloud collision (CCC), based on observations of molecular clouds.

It oers a unique opportunity to test

whether the CCC hypothesis is supported by the spatial distribution and star formation chronology of young stars. We present
the rst study of the optically visible pre-main sequence (PMS) population of the region using riHα imaging and Gaia astrometry.
Combined with an analysis of young stellar objects (YSOs) using infrared imaging, we capture the spatial distribution and starformation chronology of the young stellar population.

From the analysis, 15 Flat/Class I YSOs, 46 Class II YSOs, and 41

accreting PMS stars are identied (diskless/non-accreting sources are not included in the analysis). The distance based on Gaia
parallaxes is ∼1250 pc, signicantly closer than previously reported. The Class II YSOs and PMS stars (∼1.5 Myr old) are
spread toward the edge of the molecular clouds. They are slightly younger than the estimated crossing time of ∼2.7Myr andcloser to the estimated dynamical age ∼0.85 Myr. Younger Class I YSOs are more concentrated spatially. There exists a cavity
devoid of young stars where the two clouds overlap. This evidence suggests that the current generation of stars formed after
the collision of two clouds ∼1 Myr ago, and this result can be corroborated using future spectroscopic studies.

coalescence and hub structure in MonR2: Implications to massive star and13. Filament
cluster formation

M. S. N. Kumar, D. Arzoumanian, A. Men'shchikov, P. Palmeirim, M. Matsumura, S-i. Inutsuka F Here we

study the MonR2 star forming region, which has a rich network of laments joining in a star cluster forming hub, aiming at
understanding the hub structure and to examine the mass fraction residing in the hub and in the laments, which is a key
factor that inuences massive star formation. We conducted a multi-scale, multi-component analysis of the Herschel column
density maps (resolution of 18.2" or ∼0.07 pc at 830 pc) of the region using a newly developed algorithm "getsf" to identify the
structural components, namely, extended cloud, laments, and sources. We nd that cascades of lower column density laments
coalesce to form higher density laments eventually merging inside the hub (0.8 pc radius). As opposed to the previous viewof the hub as a massive clump with ∼1 pc radius, we nd it to be a network of short high-density laments. The total mass
reservoir in the MonR2 HFS (5 pc × 5 pc) is split between laments (54%), extended cloud (37%) and sources (9%). The M/Lof laments increase from ∼ 10 Msun/pc at 1.5pc from the hub to ∼ 100 Msun/pc at its centre, while the number of laments
per annulus of 0.2pc width decreases from 20 to 2 in the same range.

The observed radial column density structure of the−2.17
up to a radius of ∼2.5 pc from the central

HFS (lament component only) displays a power-law dependence of NH2 ∝ rhub, resembling a global collapse of the HFS. We present a scenario where the HFS can be supported by magnetic elds whichinteract, merge and reorganize themselves as the laments coalesce. In the new view of the hub as a network of high-density
laments, we suggest that only the stars located in the network can benet from the longitudinal ows of gas to become massive,
which may explain the reason for the formation of many low-mass stars in cluster centres.

observations of NGC 6334S. II. Subsonic and Transonic Narrow Filaments in a
14. ALMA
High-mass Star Formation Cloud

Shanghuo Li, Patricio Sanhueza, Chang Won Lee, Qizhou Zhang, Henrik Beuther, Aina Palau, Hong-Li Liu,
Howard Smith, Hauyu Baobab Liu, Izaskun, Jiménez-Serra, Kee-Tae Kim, Siyi Feng, Josep Miquel. Girart,
Tie Liu, Junzhi Wang, Di Li, Keping Qiu, Xing Lu, Ke Wang, Fei Li, Juan Li, Yue Cao, Shinyoung Kim, Shaye
Strom F We present a study of narrow laments toward a massive infrared dark cloud, NGC 6334S, using the Atacama Large

13+
Millimeter/submillimeter Array (ALMA). Thirteen gas laments are identied using the H CO line, while a single continuum

lament is revealed by the continuum emission. The laments present a compact radial distribution with a median lament
width of ∼0.04 pc narrower than the previously proposed `quasi-universal' 0.1 pc lament width. The higher spatial resolution
observations and higher-density gas tracer tend to identify even narrower and lower mass laments. The lament widths areroughly twice the size of embedded cores. The gas laments are largely supported by thermal motions. The nonthermal motions
are predominantly subsonic and transonic in both identied gas laments and embedded cores, which may imply that stars arelikely born in environments of low turbulence. A fraction of embedded objects show a narrower velocity dispersion comparedwith their corresponding natal laments, which may indicate that the turbulent dissipation is taking place in these embedded
cores. The physical properties (mass, mass per unit length, gas kinematics, and width) of gas laments are analogous to thoseof narrow laments found in low- to high-mass star-forming regions. The more evolved sources are found to be farther awayfrom the laments, a situation that may have resulted from the relative motions between the YSOs and their natal laments.

615. Mapping the magnetic eld in the Taurus/B211 lamentary cloud with SOFIA HAWC+

and comparing with simulation

Pak Shing Li, Enrique Lopez-Rodriguez, Hamza Ajeddig, Philippe André, Christopher F. McKee, Jeonghee
Rho, Richard I. Klein F Optical and infrared polarization mapping and recent Planck observations of the lamentary cloud
L1495 in Taurus show that the large-scale magnetic eld is approximately perpendicular to the long axis of the cloud. We use
the HAWC+ polarimeter on SOFIA to probe the complex magnetic eld in the B211 part of the cloud. Our results reveal◦
a dispersion of polarization angles of 36 , about ve times that measured on a larger scale by Planck. Applying the Davis18
Chandrasekhar-Fermi (DCF) method with velocity information obtained from IRAM 30m C O(1-0) observations, we nd two
distinct sub-regions with magnetic eld strengths diering by more than a factor 3. The quieter sub-region is magnetically criticaland sub-Alfvénic; the eld is comparable to the average eld measured in molecular clumps based on Zeeman observations.
The more chaotic, super-Alfvénic sub-region shows at least three velocity components, indicating interaction among multiple
substructures. Its eld is much less than the average Zeeman eld in molecular clumps, suggesting that the DCF value of theeld there may be an underestimate. Numerical simulation of lamentary cloud formation shows that lamentary substructures
can strongly perturb the magnetic eld.

DCF and true eld values in the simulation are compared.

Pre-stellar cores areobserved in B211 and are seen in our simulation. The appendices give a derivation of the standard DCF method that allows
for a dispersion in polarization angles that is not small, present an alternate derivation of the structure function version of the
DCF method, and treat fragmentation of laments.

KAgoshima Galactic Object survey with Nobeyama 45-metre telescope by Mapping in

16. Ammonia lines (KAGONMA): Star formation feedback on dense molecular gas in theW33 complex

Takeru Murase, Toshihiro Handa, Yushi Hirata, Toshihiro Omodaka, Makoto Nakano, Kazuyoshi Sunada,
Yoshito Shimajiri, Junya Nishi F We present the results of NH3 (1,1), (2,2) and (3,3) and H2O maser simultaneous
mapping observations toward the high-mass star-forming region W33 with the Nobeyama 45-m radio telescope.

W33 hassix dust clumps and one of which, W33 Main, is associated with a compact HII region. To investigate star-forming feedback
activity on its surroundings, the spatial distribution of the physical parameters was established. The distribution of the rotationaltemperature shows a systematic change from west to east in our observed region. The high-temperature region obtained in theregion near W33 Main is consistent with interaction between the compact HII region and the periphery molecular gas. The sizeof the interaction area is estimated to be approximately 1.25 pc. NH3 absorption features are detected toward the centre of the
HII region. Interestingly, the absorption feature was detected only in the NH3 (1,1) and (2,2) transitions, with no absorption
feature seen in the (3,3) transition. These complex proles in NH3 are dicult to explain by a simple model and may suggestthat the gas distribution around the HII region is highly complicated.

17. Near-infrared detection of H2 ows in the core of Mon R1 association

T. Yu. Magakian, A. M. Tatarnikov, T. A. Movsessian, H. R Andreasyan F We report the discovery of 4 new H2jets in Mon R1 star-forming region on the images obtained with the 2.5-m telescope of the Caucasian Mountain Observatory of
SAI MSU through the lter, centered on the H2 1-0 S(1) emission line. This discovery conrms the nature of these ows, which
existence was previously suspected using archival Spitzer GLIMPSE360 and WISE survey images. Also two infrared reection
nebulae were revealed. On the Herschel PACS survey images we found a small group of far-infrared sources, mostly unknown
ones. Among them are the possible exciting objects of these outows. Spectral energy distributions of new sources show theirextremely red colour and the bolometric luminosities reaching 3 Lsun and even 10 Lsun . They should be PMS objects at thevery early evolutionary stages.

18. How to inate a wind-blown bubble

J. M. Pittard, C. J. Wareing, M. M. Kupilas F Stellar winds are one of several ways that massive stars can aect thestar formation process on local and galactic scales. In this paper we investigate the numerical resolution needed to inate anenergy-driven stellar wind bubble in an external medium. We nd that the radius of the wind injection region, rinj , must be
below a maximum value, rinj,max , in order for a bubble to be produced, but must be signicantly below this value if the bubble
properties are to closely agree with analytical predictions. The nal bubble momentum is within 25 per cent of the value from ahigher resolution reference model if χ = rinj /rinj,max = 0.1. Our work has signicance for the amount of radial momentum thata wind-blown bubble can impart to the ambient medium in simulations, and thus on the relative importance of stellar wind
feedback.

7

19. Constraints on star formation in NGC2264

Richard J. Parker, Christina Schoettler F We quantify the spatial distribution of stars for two subclusters centred aroundthe massive/intermediate mass stars S Mon and IRS1/2 in the NGC2264 star-forming region. We nd that both subclusters
are have neither a substructured, nor a centrally concentrated distribution according to the Q-parameter. Neither subcluster
displays mass segregation according to the ΛMSR ratio, but the most massive stars in IRS1/2 have higher relative surface
densities according to the ΣLDR ratio.

We then compare these quantities to the results of N-body simulations to constrain
4−3
the initial conditions of NGC2264, which are consistent with having been dense (ρ̃ ∼ 10 M pc), highly substructured andsubvirial. These initial conditions were also derived from a separate analysis of the runaway and walkaway stars in the region,and indicate that star-forming regions within 1kpc of the Sun likely have a broad range of initial stellar densities. In the case of
NGC2264, its initial stellar density could have been high enough to cause the destruction or truncation of protoplanetary discs
and edgling planetary systems due to dynamical encounters between stars in the early stages of its evolution.

20. Sh 2-301: a blistered H II region undergoing star formation

Rakesh Pandey, Saurabh Sharma, Lokesh K. Dewangan, Devendra K. Ojha, Neelam Panwar, Swagat Das, D.
P. Bisen, Arpan Ghosh, Tirthendu Sinha F We present a multiwavelength study of the H II region Sh 2-301 (S301) using
deep optical data, near-infrared data, radio continuum data and other archival data at longer wavelengths. A cluster of youngstellar objects (YSOs) is identied in the north-east (NE) direction of S301. The Hα and radio continuum images trace the
distribution of the ionized gas surrounding a massive star ALS 207, and the S301 H II region is bounded by an arc-like structureof gas and dust emission in the south-eastern direction. The north-western part of S301 seems to be devoid of gas and dust
emission, while the presence of molecular material between the NE cluster and the central massive star ALS 207 is found. The
distribution of warm dust emission, ionized gas, and neutral hydrogen together suggests a blistered morphology of the S301 H II
region powered by ALS 207, which appears to be located near the edge of the cloud. The location of the NE cluster embeddedin the cold molecular cloud is found opposite to the blistered morphology.

There is a noticeable age dierence investigatedbetween the massive star and the NE cluster. This age dierence, pressure calculation, photodissociation regions (PDRs), andthe distribution of YSOs favour the positive feedback of the massive star ALS 207 in S301. On a wider scale of S301, the H II
region and the young stellar cluster are depicted toward the central region of a hub-lamentary system, which is evident in theinfrared images.

21. An upper limit on late accretion and water delivery in the Trappist-1 exoplanet system

Sean N. Raymond, Andre Izidoro, Emeline Bolmont, Caroline Dorn, Franck Selsis, Martin Turbet, Eric Agol,
Patrick Barth, Ludmila Carone, Rajdeep Dasgupta, Michael Gillon, Simon L. Grimm F The Trappist-1 system
contains seven roughly Earth-sized planets locked in a multi-resonant orbital conguration, which has enabled precise measurements of the planets' masses and constrained their compositions.

Here we use the system's fragile orbital structure toplace robust upper limits on the planets' bombardment histories. We use N-body simulations to show how perturbations fromadditional objects can break the multi-resonant conguration by either triggering dynamical instability or simply removing theplanets from resonance. The planets cannot have interacted with more than ∼ 5% of an Earth mass (M⊕ ) in planetesimals or a single rogue planet more massive than Earth's Moon  without disrupting their resonant orbital structure. This implies−4−2
an upper limit of 10
to 10
M⊕ of late accretion on each planet since the dispersal of the system's gaseous disk. This iscomparable to or less than the late accretion on Earth after the Moon-forming impact, and demonstrates that the Trappist-1
planets' growth was complete in just a few million years, roughly an order of magnitude faster than Earth's. Our results imply
that any large water reservoirs on the Trappist-1 planets must have been incorporated during their formation in the gaseousdisk.

22. A new method for measuring the 3D turbulent velocity dispersion of molecular clouds

Madeleine Stewart, Christoph Federrath F The structure and star formation activity of a molecular cloud are fundamentally linked to its internal turbulence. However, accurately measuring the turbulent velocity dispersion is challenging due toprojection eects and observational limitations, such as telescope resolution, particularly for clouds that include non-turbulent
motions, such as large-scale rotation. Here we develop a new method to recover the three-dimensional (3D) turbulent velocity
dispersion (σv,3D ) from position-position-velocity (PPV) data. We simulate a rotating, turbulent, collapsing molecular cloudand compare its intrinsic σv,3D with three dierent measures of the velocity dispersion accessible in PPV space: 1) the spatial

mean of the 2nd-moment map, σi , 2) the standard deviation of the gradient/rotation-corrected 1st-moment map, σ(c−grad) ,2
2
1/2
and 3) a combination of 1) and 2), called the 'gradient-corrected parent velocity dispersion', σ(p−grad) = (σi + σ(c−grad) ).
We show that the gradient correction is crucial in order to recover purely turbulent motions of the cloud, independent of theorientation of the cloud with respect to the line of sight (LOS). We nd that with a suitable correction factor and appropriate
lters applied to the moment maps, all three statistics can be used to recover σv,3D , with method 3 being the most robust

8and reliable. We determine the correction factor as a function of the telescope beam size for dierent levels of cloud rotation,and nd that for a beam FWHM f and cloud radius R, the 3D turbulent velocity dispersion can best be recovered from thegradient-corrected parent velocity dispersion via σv,3D = [(−0.29 ± 0.26)f /R + 1.93 ± 0.15]σ(p−grad) for f /R < 1, independentof the level of cloud rotation or LOS orientation.

23. Constraining the initial conditions of NGC 2264 using ejected stars found in Gaia DR2

Christina Schoettler, Richard J. Parker, Jos de Bruijne F Fast, ejected stars have been found around several youngstar-forming regions, such as the Orion Nebula Cluster (ONC). These ejected stars can be used to constrain the initial density,
spatial and kinematic substructure when compared to predictions from N -body simulations. We search for runaway and slower

walkaway stars using Gaia DR2 within 100 pc of NGC 2264, which contains subclustered regions around higher-mass OBstars (S Mon, IRS 1 and IRS 2). We nd ve runaways and nine walkaways that trace back to S Mon and six runaways andve walkaways that trace back to IRS 1/2 based on their 3D-kinematics. We compare these numbers to a range of N -bodysimulations with dierent initial conditions. The number of runaways/walkaways is consistent with initial conditions with a−3high initial stellar density (∼10 000 M
pc), a high initial amount of spatial substructure and either a subvirial or virialised
ratio for all subclusters. We also conrm the trajectories of our ejected stars using the data from Gaia EDR3, which reduces thenumber of runaways from IRS 1/2 from six to four but leaves the number of runaways from S Mon unchanged. The reduction in
runaways is due to smaller uncertainties in the proper motion and changes in the parallax/distance estimate for these stars in

Gaia EDR3. We nd further runaway/walkaway candidates based on proper motion alone in Gaia DR2, which could increase
these numbers once radial velocities are available. We also expect further changes in the candidate list with upcoming Gaia
data releases.

24. The impact of the presence of water ice on the analysis of debris disk observations

Thomas A. Stuber, Sebastian Wolf F The analysis of debris disk observations is often based on the assumption of a dust

phase composed of compact spherical grains consisting of astronomical silicate.

Instead, observations indicate the existenceof water ice in debris disks. We quantify the impact of water ice as a potential grain constituent in debris disks on the disk
parameter values estimated from photometric and spatially resolved observations in the mid- and far-infrared. We simulated
photometric measurements and radial proles of debris disks containing water ice and analyzed them by applying a disk model
purely consisting of astronomical silicate. Subsequently, we quantied the deviations between the derived and the true parametervalues. As stars in central positions we discuss a β Pic sibling and main-sequence stars with spectral types ranging from A0
to K5. To simulate observable quantities we employed selected observational scenarios regarding the choice of wavelengths andinstrument characteristics. For the β Pic stellar model and ice fractions ≥ 50 % the derived inner disk radius is biased by ice
sublimation toward higher values.

However, the derived slope of the radial density prole is mostly unaected. Along withan increasing ice fraction, the slope of the grain size distribution is overestimated by up to a median factor of ∼ 1.2 for an
ice fraction of 90 % while the total disk mass is underestimated by a factor of ∼ 0.4. The reliability of the derived minimum
grain size strongly depends on the spectral type of the central star.

For an A0-type star the minimum grain size can beunderestimated by a factor of ∼ 0.2, while for solar-like stars it is overestimated by up to a factor of ∼ 4 − 5. Neglecting radialprole measurements and using solely photometric measurements, the factor of overestimation increases for solar-like stars up
to ∼ 7 − 14.

physics of the MHD disk-jet transition in binary systems: jetted spiral walls
25. Thelaunched from disk spiral arms

Somayeh Sheikhnezami, Christian Fendt F We present a detailed physical analysis of the jet launching mechanism ofa circum-stellar disk that is located in a binary system.

Applying 3D resistive MHD simulations, we investigate the local

and global properties of the system, such as the angular momentum transport and the accretion and ejection mass uxes. In
comparison to previous works, for the rst time, we have considered the full magnetic torque, the presence of an outow, thus
the angular momentum transport by vertical motion, and the binary torque. We discuss its specic 3D structure, and how it

launched into the outow. We propose tojet spiral wall. These spiral features follow the same time evolution, with the jet spiralis aected by tidal eects. We nd that the spiral structure evolving in the disk iscall this newly discovered structure asomewhat lagging the disk spiral. We nd that the vertical transport of angular momentum has a signicant role in the total
angular momentum budget also in a binary system. The same holds for the magnetic torque, however, the contribution fromthe φ-derivative of magnetic pressure and the Bφ Br stresses are small. The gravity torque arising from the time-dependent 3DRoche potential becomes essential, as it constitutes the fundamental cause for all 3D eects appearing in our disk-jet system.
Quantitatively, we nd that the disk accretion rate in a binary system increases by 20% compared to a disk around a single
star. The disk wind mass ux increases by even 50%.

9

26. The mass and size of Herbig disks as seen by ALMA

L. Stapper, M. R. Hogerheijde, E. F. van Dishoeck, R. Mentel F Many population studies have been performed with
the Atacama Large Millimeter/submillimeter Array (ALMA) to understand the bulk properties of protoplanetary disks aroundyoung stars.

The studied populations mostly consisted of G, K & M stars, with relatively few more massive Herbig stars.

With GAIA updated distances, now is a good time to use ALMA archival data for a Herbig disk population study and take animportant step forward in our understanding of planet formation. This work determines the masses and sizes of all Herbig dust
disks observed with ALMA to date out to 450 pc. These masses and sizes are put into context of the Lupus and Upper Sco T
Tauri disk populations. ALMA Band 6 and Band 7 archival data of 36 Herbig stars are used, making this work 64% complete
excluding Orion. Using stellar parameters and distances the dust masses and sizes of the disks are determined and survival
analysis is used to make cumulative distributions of the dust masses and radii. Herbig disks have a higher dust mass than the
T Tauri disk populations of Lupus and Upper Sco by factors of ∼ 3 and ∼ 7 respectively. In addition, Herbig disks are often
larger than the typical T Tauri disk. Although the masses and sizes of Herbig disks extend over a similar range as those of T
Tauri disks, the distributions of masses and sizes of Herbig disks are signicantly skewed toward higher values. Lastly, group I
disks are more massive than group II disks. Based on these ndings we speculate that these dierences between Herbig and T
Tauri disks nd their origin in an initial disk mass that scales with the stellar mass, and that subsequent disk evolution enlarges
the observable dierences, especially if (sub)mm continuum optical depth plays a role. Moreover, the larger disk masses andsizes of Herbig stars could be linked to the increasing prevalence of giant planets with host star mass.

27. NIR jets from a clustered region of massive star formation: Morphology and compositionin the IRAS 18264-1152 region

A. R. Costa Silva, R. Fedriani, J. C. Tan, A. Caratti o Garatti, S. Ramsay, V. Rosero, G. Cosentino, P. Gorai,
S. Leurini F Massive stars form deeply embedded in their parental clouds, making it challenging to directly observe these stars
and their immediate environments. It is known that accretion and ejection processes are intrinsically related, thus observing
massive protostellar outows can provide crucial information about the processes governing massive star formation close to
the central engine. We aim to probe the IRAS 18264-1152 (G19.88-0.53) high-mass star-forming complex in the near infrared(NIR) through its molecular hydrogen (H2) jets to analyse the morphology and composition of the line emitting regions andto compare with other outow tracers. We observed the H2 NIR jets via K-band (1.9-2.5um) observations obtained with the
integral eld units VLT/SINFONI and VLT/KMOS. SINFONI provides the highest NIR angular resolution achieved so far
for the central region ( 0.2). We compared the geometry of the NIR outows with that of the associated molecular outow
probed by CO (2-1) emission mapped with SMA. We identify nine point sources. Four of these display a rising continuum in
the K-band and are BrG emitters, revealing that they are young, potentially jet-driving sources. The spectro-imaging analysis
focusses on the H2 jets, for which we derived visual extinction, temperature, column density, area, and mass. The intensity,
velocity, and excitation maps based on H2 emission strongly support the existence of a protostellar cluster, with at least two(and up to four) dierent large-scale outows. The literature is in agreement with the outow morphology found here. We−3derived a stellar density of 4000 stars pc. Our study reveals the presence of several outows driven by young sources from aforming cluster of young, massive stars. The derived stellar number density together with the geometry of the outows suggestthat stars can form in a relatively ordered manner in this cluster.

Secular evolution of MHD wind-driven discs: analytical solutions in the expanded α-

28. frameworkBenoît Tabone, Giovanni P. Rosotti, Alexander J. Cridland, Philip J. Armitage, Giuseppe Lodato F The
evolution of protoplanetary discs and the related process of planet formation is regulated by angular momentum transport andmass-loss processes. Over the past decade, the paradigm of viscosity has been challenged and MHD disc winds appear as acompelling scenario to account for disc accretion. In this work, we aim to construct the equivalent of the widely used analyticaldescription of viscous evolution for the MHD wind case. The transport of angular momentum and mass induced by the wind isparameterized by an α-like parameter and by the magnetic lever arm parameter λ. Extensions of the paradigmatic Lynden-Belland Pringle similarity solutions to the wind case are presented. We show that wind-driven accretion leads to a steeper decreasein the disc mass and accretion rate than in viscous models due to the absence of disc spreading. If the decline of the magnetic
eld strength is slower than that of the gas surface density, the disc is dispersed after a nite time. The evolution of the discin the Ṁ∗ − MD plane is sensitive to the wind and turbulence parameters.

A disc population evolving under the action ofwinds can exhibit a correlation between Ṁ∗ and MD depending on the initial conditions. The simplied framework proposedin this work opens to a new avenue to test the eectiveness of wind-driven accretion from the observed disc demographics andconstitutes an important step to include wind-driven accretion in planet population synthesis models.

10

disc winds can reproduce fast disc dispersal and the correlation between accretion
29. MHDrate and disc mass in LupusBenoît Tabone, Giovanni P. Rosotti, Giuseppe Lodato, Philip J. Armitage, Alexander J. Cridland, Ewine F.
van Dishoeck F The nal architecture of planetary systems depends on the extraction of angular momentum and mass-loss
processes of the discs in which they form. Theoretical studies proposed that magnetized winds launched from the discs (MHDdisc winds) could govern accretion and disc dispersal. In this work, we revisit the observed disc demographics in the frameworkof MHD disc winds, combining analytical solutions of disc evolution and a disc population synthesis approach. We show thatMHD disc winds alone can account for both disc dispersal and accretion properties.

The decline of disc fraction over timeis reproduced by assuming that the initial accretion timescale (a generalization of the viscous timescale) varies from disc todisc and that the decline of the magnetic eld strength is slower than that of the gas. The correlation between accretion rateand disc mass, and the dispersion of the data around the mean trend as observed in Lupus is then naturally reproduced. The
model also accounts for the rapidity of the disc dispersal. This paves the way for planet formation models in the paradigm ofwind-driven accretion.

30. Evolution of dust in protoplanetary disks of eruptive stars

Eduard Vorobyov, Aleksandr M. Skliarevskii, Tamara Molyarova, Vitaly Akimkin, Yaroslav Pavlyuchenkov,
Ágnes Kóspál, Hauyu Baobab Liu, Michihiro Takami, Anastasiia Topchieva F Luminosity bursts in young FU

Orionis-type stars warm up the surrounding disks of gas and dust, thus inicting changes on their morphological and chemicalcomposition. In this work, we aim at studying the eects that such bursts may have on the spatial distribution of dust grain
sizes and the corresponding spectral index in protoplanetary disks. We use the numerical hydrodynamics code FEOSAD, which
simulates the co-evolution of gas, dust, and volatiles in a protoplanetary disk, taking dust growth and back reaction on gas into
account. The dependence of the maximum dust size on the water ice mantles is explicitly considered. The burst is initialized
by increasing the luminosity of the central star to 100-300 L

for a time period of 100 yr. The water snowline shifts during

the burst to a larger distance, resulting in the drop of the maximum dust size interior to the snowline position because of moreecient fragmentation of bare grains. After the burst, the water snowline shifts quickly back to its preburst location followedby renewed dust growth. The timescale of dust regrowth after the burst depends on the radial distance so that the dust grains
at smaller distances reach the preburst values faster than the dust grains at larger distances. As a result, a broad peak in theradial distribution of the spectral index in the millimeter dust emission develops at ≈ 10 au, which shifts further out as thedisk evolves and dust grains regrow to preburst values at progressively larger distances. This feature is most pronounced in
evolved axisymmetric disks rather than in young gravitationally unstable counterparts, although young disks may still be goodcandidates if gravitational instability is suppressed. Abridged.

31. Is the molecular KS relationship universal down to low metallicities?

David J. Whitworth, Rowan J. Smith, Robin Tress, Scott T. Kay, Simon C. O. Glover, Mattia C. Sormani,
Ralf S. Klessen F In recent years it has been speculated that in extreme low metallicity galactic environments, stars form inregions that lack H2. In this paper we investigate how changing the metallicity and UV-eld strength of a galaxy aects thestar formation within, and the molecular gas Kennicutt-Schmidt relation. Using extremely high resolution arepo simulations ofisolated dwarf galaxies, we independently vary the metallicity and UV-eld to between 110% solar neighbourhood values. We
include a non-equilibrium, time-dependant chemical network to model the molecular composition of the ISM, and include theeects of gas shielding from an ambient UV eld. Crucially our simulations directly model the gravitational collapse of gas intostar-forming clumps and cores and their subsequent accretion using sink particles. In this rst publication we nd that reducing
the metallicity and UV-eld by a factor of 10 has no eect on star formation, and minimal eect on the cold, dense star forminggas. The cold gas depletion times are almost an order of magnitude longer than the molecular gas depletion time due to thepresence of star formation in HI dominated cold gas. We study the H2 Kennicutt-Schmidt relationship that arises naturally
within the simulations and nd a near linear power law index of N = 1.09 +/- 0.014 in our ducial 10% solar metallicity model.
As the metallicity and UV-eld are reduced this becomes moderately steeper, with a slope of N = 1.24 +/- 0.022 for our 1%
solar metallicity and 1% solar UV eld model.

32. A Census of Protostellar Outows in Nearby Molecular Clouds

Duo Xu, Stella Oner, Robert Gutermuth, Shuo Kong, Hector G. Arce F We adopt the deep learning method
CASI-3D (Convolutional Approach to Structure Identication-3D) to systemically identify protostellar outows in 12CO and
13CO observations of the nearby molecular clouds, Ophiuchus, Taurus, Perseus and Orion. The total outow masses are 267
Msun, 795 Msun, 1305 Msun and 6332 Msun for Ophiuchus, Taurus, Perseus and Orion, respectively. We show the outow
mass in each cloud is linearly proportional to the total number of young stellar objects. The estimated total 3D deprojectedoutow energies are 9e45 ergs, 6e46 ergs, 1.2e47 ergs and 6e47 ergs for Ophiuchus, Taurus, Perseus and Orion, respectively. The

11

energy associated with outows is sucient to oset turbulent dissipation at the current epoch for all four clouds. All clouds
also exhibit a break point in the spatial power spectrum of the outow prediction map, which likely corresponds to the typicaloutow mass and energy injection scale.

A Comprehensive Study of the Young Cluster IRAS 05100+3723: Properties, Sur-

33. rounding Interstellar Matter, and Associated Star Formation

R. K. Yadav, M. R. Samal, E. Semenko, A. Zavagno, S. Vaddi, P. Prajapati, D. K. Ojha, A. K. Pandey, M.
Ridsdill-Smith, J. Jose, S. Patra, S. Dutta, P. Irawati, S. Sharma, D. K. Sahu, N. Panwar F We present acomprehensive multiwavelength investigation of a likely massive young cluster `IRAS 05100+3723' and its environment with theaim to understand its formation history and feedback eects. We nd that IRAS 05100+3723 is a distant (∼3.2 kpc), moderatemass (∼500 M), young (∼3 Myr) cluster with its most massive star being an O8.5V-type. From spectral modeling, we estimate

the eective temperature and log g of the star as ∼33,000 K and ∼3.8, respectively. Our radio continuum observations revealthat the star has ionized its environment forming an HII region of size ∼2.7 pc, temperature ∼5,700 K, and electron density∼165 cm−3 . However, our large-scale dust maps reveal that it has heated the dust up to several parsecs (∼10 pc) in the range
1317−28 K and the morphology of warm dust emission resembles a bipolar HII region. From dust andCO gas analyses, we ndevidences that the formation of the HII region has occurred at the very end of a long lamentary cloud around 3 Myr ago, likely
due to edge collapse of the lament. We show that the HII region is currently compressing a clump of mass ∼2700 M

at itswestern outskirts, at the junction of the HII region and lament. We observe several 70 µm point sources of intermediate-mass
and class 0 nature within the clump. We attribute these sources as the second generation stars of the complex. We proposethat the star formation in the clump is either induced or being facilitated by the compression of the expanding HII region onto
the inowing lamentary material.

34. Atomic Shocks in the Outow of L1551 IRS 5 Identied with SOFIA-upGREAT Ob-

servations of [OI]

Yao-Lun Yang, Neal J. Evans II, Agata Karska, Lars E. Kristensen, Rebeca Aladro, Jon P. Ramsey, Joel D.
Green, Jeong-Eun Lee F We present velocity resolved SOFIA/upGREAT observations of [OI] and [CII] lines toward a Class
I protostar, L1551 IRS 5, and its outows. The SOFIA observations detect [OI] emission toward only the protostar and [CII]−1emission toward the protostar and the red-shifted outow. The [OI] emission has a width of ∼100 km s
only in the blueshifted velocity, suggesting an origin in shocked gas. The [CII] lines are narrow, consistent with an origin in a photodissociation
region.

Dierential dust extinction from the envelope due to the inclination of the outows is the most likely cause of themissing red-shifted [OI] emission. Fitting the [OI] line prole with two Gaussian components, we nd one component at the−1−1source velocity with a width of ∼20 km s
and another extremely broad component at -30 km s
with a width of 87.5 km−1s, the latter of which has not been seen in L1551 IRS 5. The kinematics of these two components resemble cavity shocks inmolecular outows and spot shocks in jets. Radiative transfer calculations of the [OI], high-J CO, and H2 O lines in the cavity
shocks indicate that [OI] dominates the oxygen budget, making up more than 70oxygen abundance and suggesting [O]/[H]−4of ∼1.5×10. Attributing the extremely broad [OI] component to atomic winds, we estimate the intrinsic mass loss rate of−6−1(1.3±0.8)× 10
M yr. The intrinsic mass loss rates derived from low-J CO, [OI], and HI are similar, supporting the modelof momentum-conserving outows, where the atomic wind carries most momentum and drives the molecular outows.

of the molecular interstellar medium probed by Gaia: steep velocity dispersion35. Kinematics
size relation, isotropic turbulence, and location-dependent energy dissipation
Ji-Xuan Zhou, Guang-Xing Li, Bing-Qiu Chen F The morphology and kinematics of the molecular interstellar medium

are controlled by processes such as turbulence, gravity, stellar feedback, and Galactic shear. Using a sample of 15149 youngstellar objects (YSOs) with Gaia Data Release 2 (DR2) astrometric measurements, we study morphology and kinematic structureof their associated molecular gas. We identify 150 YSO associations with distance d . 3 kpc. The YSO associations are oriented◦
parallel to the disk midplane, with a median angle of 30 , and they have a median aspect ratio of 1.97. Along the Galactic
0.66±0.05
longitude direction, the velocity dispersion is related to the separation by σvl = 0.58 (rl /pc)
(km s−1 ), along the Galactic
0.64±0.04−1
0.67±0.05
latitude direction, σvb = 0.54 (rb /pc)
(km s ), and overall σv,2D = 0.74 (r/pc)(km s−1 ). The slope is on the3
stepper side, yet consistent with previous measurements. The energy dissipation rate of turbulence ˙ = σv,3D /L decreases−4 −0.45 (rgal /kpc)−1 −1
with the Galactocentric distance rgal by ˙ = 1.77 × 10e(erg g s ) for clouds with 40 pc < r < 130 pc,−1which corresponds to a gradient of 0.2 dex kpc. This decrease can be explained if turbulence is driven by cloud collisions,as the clouds located in the inner Galaxy have higher chances to accrete smaller clouds. Although the density structures of
the complexes are anisotropic, the turbulence is consistent with being isotropic.

Thus, the clouds are long-lived, stationary

structures shaped by the Galactic motion where turbulence is maintained by a continuous injection.

1236. Magnetic eld structure of OMC-3 in the far infrared revealed by SOFIA/HAWC+

Niko Zielinski, Sebastian Wolf F We report the SOFIA/HAWC+ band D (154 µm) and E (214 µm) polarimetric observationsof the lamentary structure OMC-3 that is part of the Orion molecular cloud. The polarization pattern is uniform for bothbands and parallel to the lament structure.

The polarization degree decreases toward regions with high intensity for bothbands, revealing a so called "polarization hole." We identied an optical depth eect in which polarized emission and extinction
act as counteracting mechanisms as a potential contributor to this phenomenon. Assuming that the detected polarization iscaused by the emission of magnetically aligned non-spherical dust grains, the inferred magnetic eld is uniform and oriented
perpendicular to the lament.

The magnetic eld strength derived from the polarization patterns at 154 µm and 214 µm

amounts to 202 µG and 261 µG, respectively. The derived magnetic eld direction is consistent with that derived from previous
polarimetric observations in the far infrared and submillimeter (submm) wavelength range.

Investigating the far-infrared

polarization spectrum derived from the SOFIA/HAWC+ observations, we do not nd a clear correlation between the polarization
spectrum and cloud properties, namely, the column density, N (H2 ), and temperature, T .

13