The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 340 — 21 April 2021
Editor: João Alveswww.starformation.news

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Cover image caption
Simulation of diffuse Interstellar Medium flows passing through a spiral shock (face-on view in the galactic disk). Colors
represent velocity, from red (at about 20 to 30 km/s) to blue (at about −20 km/s). Gas enters the spiral arm from the bottom
left with positive velocities of 10 − 30 km/s, while gas already present in the arm has negative velocities. This produces aconvergent flow and a shock of the order of 20 to 30 km/s (red color). The figure covers about 500 pc in x and y. Credit:
Smilgys & Bonnell 2016.
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. We extract the title, authors, and the abstract’s
text directly from the arXiv, so please do not remove the LATEX formatting when submitting to the arXiv. If you
do, your abstract will not look great either at the arXiv (which uses MathJax to convert LATEX math symbols to the web) or
the SFN.

Abstracts
1. ALMA-IRDC: Dense gas mass distribution from cloud to core scales
A. T. Barnes, J. D. Henshaw, F. Fontani, J. E. Pineda, G. Cosentino, J. C. Tan, P. Caselli, I. Jiménez-Serra,
C. Y. Law, A. Avison, F. Bigiel, S. Feng, S. Kong, S. N. Longmore, L. Moser, R. J. Parker, Á. Sánchez-Monge,
K. Wang F Infrared dark clouds (IRDCs) are potential hosts of the elusive early phases of high-mass star formation (HMSF).
Here we conduct an in-depth analysis of the fragmentation properties of a sample of 10 IRDCs, which have been highlighted assome of the best candidates to study HMSF within the Milky Way. To do so, we have obtained a set of large mosaics covering
these IRDCs with ALMA at band 3 (or 3mm). These observations have a high angular resolution ( 3arcsec or 0.05pc), and highcontinuum and spectral line sensitivity ( 0.15mJy/beam and 0.2K per 0.1km/s channel at the N2H+(1-0) transition). From thedust continuum emission, we identify 96 cores ranging from low- to high-mass (M = 3.4 to 50.9 Msun) that are gravitationallybound (alphavir = 0.3 to 1.3) and which would require magnetic field strengths of B = 0.3 to 1.0mG to be in virial equilibrium.
We combine these results with a homogenised catalogue of literature cores to recover the hierarchical structure within theseclouds over four orders of magnitude in spatial scale (0.01pc to 10pc). Using supplementary observations at an even higher
angular resolution, we find that the smallest fragments (<0.02pc) within this hierarchy do not currently have the mass and/or
the density required to form high-mass stars. Nonetheless, the new ALMA observations presented in this paper have facilitatedthe identification of 19 (6 quiescent and 13 star-forming) cores that retain >16Msun without further fragmentation. These
high-mass cores contain trans-sonic non-thermal motions, are kinematically sub-virial, and require moderate magnetic fieldstrengths for support against collapse. The identification of these potential sites of high-mass star formation represents a key
step in allowing us to test the predictions from high-mass star and cluster formation theories.

2. Fragmentation and kinematics in high-mass star formation: CORE-extension targeting
two very young high-mass star-forming regions

H. Beuther, C. Gieser, S. Suri, H. Linz, P. Klaassen, D. Semenov, J. M. Winters, Th. Henning, J. D. Soler, J.
S. Urquhart, J. Syed, S . Feng, T. Moeller, M. T. Beltran, A. Sanchez-Monge, S. N. Longmore, T. Peters, J.
Ballesteros-Paredes, P. Schilke, L. Moscadelli, A. Palau, R. Cesaroni, S. Lumsden, R. Pudritz, F. Wyrowski,
R. Kuiper, A. Ahmadi F Context: The formation of high-mass star-forming regions from their parental gas cloud and thesubsequent fragmentation processes lie at the heart of star formation research. Aims: We aim to study the dynamical andfragmentation properties at very early evolutionary stages of high-mass star formation. Methods: Employing the NOrthern2Extended Millimeter Array (NOEMA) and the IRAM 30m telescope, we observed two young high-mass star-forming regions,
ISOSS22478 and ISOSS23053, in the 1.3mm continuum and spectral line emission at a high angular resolution (∼0.8”). Results:
We resolved 29 cores that are mostly located along filament-like structures. Depending on the temperature assumption, thesecores follow a mass-size relation of approximately M∼r2.0 , corresponding to constant mean column densities. However, withdifferent temperature assumptions, a steeper mass-size relation up to M∼r3.0 , which would be more likely to correspond toconstant mean volume densities, cannot be ruled out. The correlation of the core masses with their nearest neighbor separations
is consistent with thermal Jeans fragmentation. We found hardly any core separations at the spatial resolution limit, indicatingthat the data resolve the large-scale fragmentation well. Although the kinematics of the two regions appear very different at firstsight - multiple velocity components along filaments in ISOSS22478 versus a steep velocity gradient of more than 50km/s/pc in
ISOSS23053 - the findings can be explained within the framework of a dynamical cloud collapse scenario. Conclusions: While
our data are consistent with a dynamical cloud collapse scenario and subsequent thermal Jeans fragmentation, the importanceof additional environmental properties, such as the magnetization of the gas or external shocks triggering converging gas flows,
is nonetheless not as well constrained and would require future investigation.

3. SEDBYS: A python-based SED Builder for Young Stars
Claire L Davies F Spectral energy distributions (SEDs) are useful primary and complementary tools in the analysis of observations of young stars. However, the process of collating, inspecting, and flux-converting archival photometry and spectroscopy
to build spectral energy distributions for young stars can be time-consuming. Here, I present SEDBYS (Spectral Energy Distribution Builder for Young Stars), a python-based repository of command-line tools built to (i) query online photometric andspectroscopic catalogs and a distributed database of archival photometry, (ii) use a look-up table of zero points to flux-convert
the acquired data, (iii) enable visual inspection of the SED and (iv) handle book-keeping to collate references in bibTeX format.
The code is distributed via git and is equipped with additional tools to enable users to add existing or forthcoming catalogs to
the list of sources queried, ensuring the longevity of SEDBYS as a tool for the star formation community.

4. Magnetic fields and Star Formation around HII regions: The S235 complex
R. Devaraj, D. P. Clemens, L. K. Dewangan, A. Luna, T. P. Ray, J. Mackey F Magnetic fields are ubiquitous andessential in star formation. In particular, their role in regulating formation of stars across diverse environments like HII regions
needs to be well understood. In this study, we present magnetic field properties towards the S235 complex using near-infrared(NIR) H-band polarimetric observations, obtained with the Mimir and POLICAN instruments. We selected 375 backgroundstars in the field through combination of Gaia distances and extinctions from NIR colors. The plane-of-sky (POS) magnetic
field orientations inferred from starlight polarization angles reveal a curved morphology tracing the spherical shell of the HII
region. The large-scale magnetic field traced by Planck is parallel to the Galactic plane. We identified 11 dense clumps using
1.1 mm dust emission, with masses between 33 − 525 M . The clump averaged POS magnetic field strengths were estimatedto be between 36 − 121 µG, with a mean of ∼65 µG. The mass-to-flux ratios for the clumps are found to be sub-critical withturbulent Alfvén Mach numbers less than 1, indicating a strongly magnetized region. The clumps show scaling of magnetic fieldstrength vs density with a power-law index of 0.52 ± 0.07, similar to ambipolar diffusion models. Our results indicate the S235
complex is a region where stellar feedback triggers new stars and the magnetic fields regulate the rate of new star formation.

5. Unraveling the inner substructure of new candidate hub-filament system in the HII
region G25.4NW

L. K. Dewangan F We present multi-scale and multi-wavelength data of the Galactic HII region G25.4-0.14 (hereafter
G25.4NW, distance 5.7 kpc). The SHARC-II 350 micron continuum map displays a hub-filament configuration containing fiveparsec scale filaments and a central compact hub. Through the 5 GHz radio continuum map, four ionized clumps (i.e., Ia-Id)
are identified toward the central hub, and are powered by massive OB-stars. The Herschel temperature map depicts the warm
dust emission (i.e., Td 23-39 K) toward the hub. High resolution Atacama Large Millimeter/submillimeter Array (ALMA) 1.3
mm continuum map (resolution 0".82 X 0".58) reveals three cores (c1-c3; mass 80-130 Msun) toward the ionized clumps Ia,
and another one (c4; mass 70 Msun) toward the ionized clump Ib. A compact near-infrared (NIR) emission feature (extent
0.2 pc) is investigated toward the ionized clump Ia excited by an O8V-type star, and contains at least three embedded K-bandstars. In the direction of the ionized clump Ia, the ALMA map also shows an elongated feature (extent 0.2 pc) hosting thecores c1-c3. All these findings together illustrate the existence of a small cluster of massive stars in the central hub. Considering
the detection of the hub-filament morphology and the spatial locations of the mm cores, a global non-isotropic collapse (GNIC)
scenario appears to be applicable in G25.4NW, which includes the basic ingredients of the global hierarchical collapse andclump-fed accretion models. Overall, the GNIC scenario explains the birth of massive stars in G25.4NW.

3

Hi-GAL compact source catalogue – II. The 360° catalogue of clump physical prop6. The
ertiesD. Elia, M. Merello, S. Molinari, E. Schisano, A. Zavagno, D. Russeil, P. Mège, P. G. Martin, L. Olmi, M.
Pestalozzi, R. Plume, S. E. Ragan, M. Benedettini, D. J. Eden, T. J. T. Moore, A. Noriega-Crespo, R. Paladini, P. Palmeirim, S. Pezzuto, G. L. Pilbratt, K. L. J. Rygl, P. Schilke, F. Strafella, J. C. Tan, A. Traficante,
A. Baldeschi, J. Bally, A. M. di Giorgio, E. Fiorellino, S. J. Liu, L. Piazzo, D. Polychroni F We present the360◦ catalogue of physical properties of Hi-GAL compact sources, detected between 70 and 500 µm. This release not only
completes the analogous catalogue previously produced by the Hi-GAL collaboration for −71◦ . ` . 67◦ , but also meaningfully
improves it thanks to a new set of heliocentric distances, 120808 in total. About a third of the 150223 entries are located in
the newly added portion of the Galactic plane. A first classification based on detection at 70 µm as a signature of ongoingstar-forming activity distinguishes between protostellar sources (23 per cent of the total) and starless sources, with the latter
further classified as gravitationally bound (pre-stellar) or unbound. The integral of the spectral energy distribution, including
ancillary photometry from λ = 21 to 1100 µm, gives the source luminosity and other bolometric quantities, while a modified
black body fitted to data for λ ≥ 160 µm yields mass and temperature. All tabulated clump properties are then derived using
photometry and heliocentric distance, where possible. Statistics of these quantities are discussed with respect to both source
Galactic location and evolutionary stage. No strong differences in the distributions of evolutionary indicators are found between
the inner and outer Galaxy. However, masses and densities in the inner Galaxy are on average significantly larger, resulting
in a higher number of clumps that are candidates to host massive star formation. Median behaviour of distance-independent
parameters tracing source evolutionary status is examined as a function of the Galactocentric radius, showing no clear evidenceof correlation with spiral arm positions.

7. Launching the asymmetric bipolar jet of DO Tau

J. Erkal, C. Dougados, D. Coffey, S. Cabrit, F. Bacciotti, R. Garcia-Lopez, D. Fedele, A. Chrysostomou F The
role of bipolar jets in the formation of stars, and in particular how they are launched, is still not well understood. We probe theprotostellar jet launching mechanism, via high resolution observations of the near-IR [FeII] 1.53,1.64 micron lines. We consider
the bipolar jet from the Classical T Tauri star, DO Tau, investigate jet morphology and kinematics close to the star, using
AO-assisted IFU observations from GEMINI/NIFS. The brighter, blue-shifted jet is collimated quickly after launch. This earlycollimation requires the presence of magnetic fields. We confirm velocity asymmetries between the two jet lobes, and confirm notime variability in the asymmetry over a 20 year interval. This sustained asymmetry is in accordance with recent simulationsof magnetised disk-winds. We examine the data for jet rotation. We report an upper limit on differences in radial velocityof 6.3 and 8.7 km/s for the blue and red-shifted jets, respectively. Interpreting this as an upper limit on jet rotation implies
that any steady, axisymmetric magneto-centrifugal model of jet launching is constrained to a launch radius in the disk-planeof 0.5 and 0.3 au for the blue and red-shifted jets, respectively. This supports an X-wind or narrow disk-wind model. This
pertains only to the observed high velocity [FeII] emission, and does not rule out a wider flow launched from a wider radius.
We report detection of small amplitude jet axis wiggling in both lobes. We rule out orbital motion of the jet source as thecause. Precession can better account for the observations but requires double the precession angle, and a different phase for thecounter-jet. Such non-solid body precession could arise from an inclined massive Jupiter companion, or a warping instability
induced by launching a magnetic disk-wind. Overall, our observations are consistent with an origin of the DO Tau jets fromthe inner regions of the disk.

8. Magnetic Fields in Massive Star-Forming Regions (MagMaR) I. Linear Polarized Imaging of the UCHII Region G5.89-0.39

M. Fernández-López, P. Sanhueza, L. A. Zapata, I. Stephens, C. Hull, Q. Zhang, J. M. Girart, P. M. Koch,
P. Cortés, A. Silva, K. Tatematsu, F. Nakamura, A. E. Guzmán, Q. Nguyen Luong, E. Guzmán Ccolque, Y.
-W. Tang, V. Chen F We report 1.2 mm polarized continuum emission observations carried out with the Atacama Large
Millimeter/submillimeter Array (ALMA) toward the high-mass star formation region G5.89-0.39. The observations show aprominent 0.2 pc north-south filamentary structure. The UCHII in G5.89-0.39 breaks the filament in two pieces. Its millimeteremission shows a dusty belt with a mass of 55-115 M and 4,500 au in radius, surrounding an inner part comprising mostly
ionized gas with a dust emission only accounting about 30millimeter emission. We also found a lattice of convex arches which
may be produced by dragged dust and gas from the explosive dispersal event involving the O5 Feldt’s star. The north-south
filament has a mass between 300-600 M and harbours a cluster of about 20 millimeter envelopes with a median size and massof 1700 au and 1.5 M , respectively, some of which are already forming protostars. We interpret the polarized emission in thefilament as mainly coming from magnetically aligned dust grains. The polarization fraction is 4.4filaments and 2.1Filamentand perpendicular to the South Filament. In the Central Shell, the magnetic fields are roughly radial in a ring surrounding the
dusty belt between 4,500 and 7,500 au, similar to the pattern recently found in the surroundings of Orion BN/KL. This may
be an independent observational signpost of explosive dispersal outflows and should be further investigated in other regions.

49. Streaming instability in a global patch simulation of protoplanetary disks

Mario Flock, Andrea Mignone F In the recent years, sub/mm observations of protoplanetary disks have discovered anincredible diversity of substructures in the dust emission. An important result was the finding that dust grains of mm size areembedded in very thin dusty disks. This implies that the dust mass fraction in the midplane becomes comparable to the gas,increasing the importance of the interaction between the two components there. We address this problem by means of numerical
2.5D simulations in order to study the gas and dust interaction in fully global stratified disks. To this purpose, we employ the
recently developed dust grain module in the PLUTO code. Our model focuses on a typical T Tauri disk model, simulating ashort patch of the disk at 10 au which includes grains of constant Stokes number of St = 0.01 and St = 0.1, corresponding to
grains with sizes of 0.9 cm and 0.9 mm, respectively, for the given disk model. By injecting a constant pebble flux at the outerdomain, the system reaches a quasi steady state of turbulence and dust concentrations driven by the streaming instability. For
our given setup and using resolutions up to 2500 cells per scale height we resolve the streaming instability, leading to local
dust clumping and concentrations. Our results show dust density values of around 10-100 times the gas density with a steadystate pebble flux between 3.5 × 10−4 and 2.5 × 10−3 MEarth /year for the models with St = 0.01 and St = 0.1. The grain sizeand pebble flux for model St = 0.01 compares well with dust evolution models of the first million years of disk evolution. For
those grains the scatter opacity dominates the extinction coefficient at mm wavelengths. These types of global dust and gas
simulations are a promising tool for studies of the gas and dust evolution at pressure bumps in protoplanetary disks.

Clustered star formation towards Berkeley 87 / ON2. I. Multi-wavelength census and10. the population overlap problem

Diego de la Fuente, Carlos G. Román-Zúñiga, Elena Jiménez-Bailón, João Alves, Miriam Garcia, Sean Venus
F (ABRIDGED) Disentangling line-of-sight alignments of young stellar populations is crucial for observational studies ofstar-forming complexes. This task is particularly problematic in a Cygnus-X subregion where several components, locatedat different distances, are overlapped: the Berkeley 87 young massive cluster, the poorly-known [DB2001] Cl05 embeddedcluster, and the ON2 star-forming complex, in turn composed of several HII regions. We aim at providing a methodology
for building an exhaustive census of young objects that can consistently deal with large differences in both extinction anddistance. OMEGA2000 near-infrared observations of the Berkeley 87 / ON2 field are merged with archival data from Gaia,
Chandra, Spitzer, and Herschel, as well as cross-identifications from the literature. To address the incompleteness effects andselection biases that arise from the line-of-sight overlap, we adapt existing methods for extinction estimation and young object
classification, and we define the intrinsic reddening index, Rint , a new tool to separate intrinsically red sources from those
whose infrared color excess is caused by extinction. We also introduce a new method to find young stellar objects based on
Rint . The flexibility of our approach allows to overcome photometric biases in order to obtain homogeneous catalogs of young
sources. As a result, we find 571 objects whose classification is related to recent or ongoing star formation. Together with otherpoint sources with individual estimates of distance or extinction, we compile a catalog of 3005 objects to be used for further
membership work. A new distance for Berkeley 87, (1673 ± 17) pc, is estimated as a median of 13 spectroscopic members withaccurate Gaia EDR3 parallaxes. Our multi-wavelength census will serve as a basis for disentangling the overlapped populations.

11. An ALMA Survey of Protoplanetary Disks in Lynds 1641

Sierra L. Grant, Catherine C. Espaillat, John Wendeborn, John J. Tobin, Enrique Macías, Anneliese Rilinger,Álvaro Ribas, S. Thomas Megeath, William J. Fischer, Nuria Calvet, Kyoung Hee Kim F We present ALMA
observations of 101 protoplanetary disks within the star-forming region Lynds 1641 in the Orion Molecular Cloud A. Our
observations include 1.33 mm continuum emission and spectral windows covering the J=2-1 transition of 12 CO, 13 CO, andC18 O. We detect 89 protoplanetary disks in the dust continuum at the 4σ level (∼88and 31 in 12 CO, 13 in 13 CO, and 4 in
C18 O. Our sample contains 23 transitional disks, 20 of which are detected in the continuum. We target infrared-bright ClassII objects, which biases our sample towards massive disks. We determine dust masses or upper limits for all sources in our
sample and compare our sample to protostars in this region. We find a decrease in dust mass with evolutionary state. We also
compare this sample to other regions surveyed in the (sub-)millimeter and find that Lynds 1641 has a relatively massive dust
disk population compared to regions of similar and older ages, with a median dust mass of 11.1+32.9−4.6 M⊕ and 27masses equal
to or greater than the minimum solar nebula dust mass value of ∼30 M⊕ . We analyze the disk mass-accretion rate relationshipin this sample and find that the viscous disk lifetimes are similar to the age of the region, however with a large spread. One
object, [MGM2012] 512, shows large-scale (>5000 AU) structure in both the dust continuum and the three gas lines. We discuss
potential origins for this emission, including an accretion streamer with large dust grains.

5timescale of protoplanetary disks in the low-metallicity young cluster Dolidze
12. Dispersal
25
M. G. Guarcello, K. Biazzo, J. J. Drake, G. Micela, L. Prisinzano, S. Sciortino, F. Damiani, E. Flaccomio, C.
Neiner, N. J. Wright F The dispersal of protoplanetary disks sets the timescale available for planets to assemble, and thus
it is one of the fundamental parameters in theories of planetary formation. Disk dispersal is determined by several propertiesof the central star, the disk itself, and the surrounding environment. In particular, the metallicity of disks may impact theirevolution, even if to date controversial results exist: in low-metallicity clusters disks seem to rapidly disperse, while in the
Magellanic Clouds some evidence supports the existence of accreting disks few tens of Myrs old. In this paper we study thedispersal timescale of disks in Dolidze 25, the young cluster in proximity of the Sun with lowest metallicity, with the aim ofunderstanding whether disk evolution is impacted by the low-metallicity of the cluster. We have analyzed Chandra/ACIS-I
observations of the cluster and combined the resulting source catalog with existing optical and infrared catalogs of the region.
We selected the disk-bearing population and the disk-less population of Dolidze 25. We have derived stellar parameters fromisochrones fitted to color-magnitude diagrams. We derived a disk fraction of about 34existing estimates of the disk fraction ofclusters younger than 10 Myrs, our study suggests that the disk fraction of Dolidze 25 is lower than what is expected from its
age alone. Even if our results are not conclusive given the intrinsic uncertainty on stellar ages estimated from isochrones fitting
to color-magnitude diagrams, we suggest that disk evolution in Dolidze 25 may be impacted by the environment. Given thepoor O star population and low stellar density of the cluster, it is more likely that disks dispersal timescale is dictated more by
the low metallicity of the cluster rather than external photoevaporation or dynamical encounters.

Analysis of physical processes in eruptive YSOs with near infrared spectra and multi-

13. wavelength light curves

Zhen Guo, P. W. Lucas, C. Contreras Peña, L. C. Smith, C. Morris, R. G. Kurtev, J. Borissova, J. AlonsoGarcía, D. Minniti, A. -N. Chené, M. S. N. Kumar, A. Caratti o Garatti, D. Froebrich, W. H. Stimson F
The decade-long Vista Variables in the Via Lactea (VVV) survey has detected numerous highly variable young stellar objects(YSOs). We present a study of 61 highly variable VVV YSOs (∆Ks = 1-5 mag), combining near infrared spectra from Magellan
and VLT with VVV and NEOWISE light curves to investigate physical mechanisms behind eruptive events. Most sources arespectroscopically confirmed as eruptive variables (typically Class I YSOs) but variable extinction is also seen. Among them,magnetically controlled accretion, identified by Hi recombination emission (usually accompanied by CO emission), is observedin 46 YSOs. Boundary layer accretion, associated with FU Ori-like outbursts identified by CO overtone and H2 O absorption,
is observed only in longer duration events (≥5 yr total duration). However, even in long duration events, the magneticallycontrolled accretion mode predominates, with amplitudes similar to the boundary layer mode. Shorter (100-700 days) eruptive
events usually have lower amplitudes and these events are generally either periodic accretors or multiple timescale events,
wherein large photometric changes occur on timescales of weeks and years. We find that the ratio of amplitudes in Ks and W 2
can distinguish between variable accretion and variable extinction. Several YSOs are periodic or quasi-periodic variables. We
identify examples of periodic accretors and extinction-driven periodicity among them (with periods up to 5 yr) though moredata are needed to classify some cases. The data suggest that dynamic interactions with a companion may control the accretion
rate in a substantial proportion of eruptive systems, although star-disc interactions should also be considered.

HST Survey of Protostellar Outflow Cavities: Does Feedback Clear Envelopes?
14. AnNolan M. Habel, S. Thomas Megeath, Joseph Jon Booker, William J. Fischer, Marina Kounkel, Charles
Poteet, Elise Furlan, Amelia Stutz, P. Manoj, John J. Tobin, Zsofia Nagy, Riwaj Pokhrel, Dan Watson F We
study protostellar envelope and outflow evolution using Hubble Space Telescope NICMOS or WFC3 images of 304 protostars
in the Orion Molecular clouds. These near-IR images resolve structures in the envelopes delineated by the scattered light of thecentral protostars with 80 AU resolution and they complement the 1.2-870 micron spectral energy distributions obtained with
the Herschel Orion Protostar Survey program (HOPS). Based on their 1.60 micron morphologies, we classify the protostars into
five categories: non-detections, point sources without nebulosity, bipolar cavity sources, unipolar cavity sources, and irregulars.
We find point sources without associated nebulosity are the most numerous, and show through monochromatic Monte Carloradiative transfer modeling that this morphology occurs when protostars are observed at low inclinations or have low envelope
densities. We also find that the morphology is correlated with the SED-determined evolutionary class with Class 0 protostars
more likely to be non-detections, Class I protostars to show cavities and flat-spectrum protostars to be point sources. Using anedge detection algorithm to trace the projected edges of the cavities, we fit power-laws to the resulting cavity shapes, thereby
measuring the cavity half-opening angles and power-law exponents. We find no evidence for the growth of outflow cavities as
protostars evolve through the Class I protostar phase, in contradiction with previous studies of smaller samples. We conclude
that the decline of mass infall with time cannot be explained by the progressive clearing of envelopes by growing outflow cavities.
Furthermore, the low star formation efficiency inferred for molecular cores cannot be explained by envelope clearing alone.

6

of an Edge-on Circumstellar Debris Disk Around BD+45 598: a Newly Iden15. Discovery
tifed Member of the β Pictoris Moving Group◦

Sasha Hinkley, Elisabeth C. Matthews, Charlène Lefevre, Jean-Francois Lestrade, Grant Kennedy, Dimitri
Mawet, Karl R. Stapelfeldt, Shrishmoy Ray, Eric Mamajek, Brendan P. Bowler, David Wilner, Jonathan
Williams, Megan Ansdell, Mark Wyatt, Alexis Lau, Mark W. Phillips Jorge Fernandez Fernandez, Jonathan
Gagné, Emma Bubb, Ben J. Sutlieff, Thomas J. G. Wilson, Brenda Matthews, Henry Ngo, Danielle Piskorz,
Justin R. Crepp, Erica Gonzalez, Andrew W. Mann, Gregory Mace F We report the discovery of a circumstellar
debris disk viewed nearly edge-on and associated with the young, K1 star BD+45◦ 598 using high-contrast imaging at 2.2µm
obtained at the W.M. Keck Observatory. We detect the disk in scattered light with a peak significance of ∼5σ over threeepochs, and our best-fit model of the disk is an almost edge-on ∼70 AU ring, with inclination angle ∼87◦ . Using the NOEMA
interferometer at the Plateau de Bure Observatory operating at 1.3mm, we find resolved continuum emission aligned with the−4ring structure seen in the 2.2µm images. We estimate a fractional infrared luminosity of LIR /Ltot ' 6+2, higher than
−1 ×10◦that of the debris disk around AU Mic. Several characteristics of BD+45 598, such as its galactic space motion, placement ina color-magnitude diagram, and strong presence of Lithium, are all consistent with its membership in the β Pictoris Moving
Group with an age of 23±3 Myr. However, the galactic position for BD+45◦ 598 is slightly discrepant from previously-known
members of the β Pictoris Moving Group, possibly indicating an extension of members of this moving group to distances ofat least 70pc. BD+45◦ 598 appears to be an example from a population of young circumstellar debris systems associated with
newly identified members of young moving groups that can be imaged in scattered light, key objects for mapping out the early
evolution of planetary systems from ∼10-100 Myr. This target will also be ideal for northern-hemisphere, high-contrast imaging
platforms to search for self-luminous, planetary mass companions residing in this system.

The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Strong
16. Increase in Mid-Infrared Continuum Emission
T. R. Hunter, C. L. Brogan, J. M. De Buizer, A. P. M. Towner, C. D. Dowell, G. C. MacLeod, B. Stecklum, C.
J. Cyganowski, S. J. El-Abd, B. A. McGuire F In recent years, dramatic outbursts have been identified toward massive
protostars via infrared and millimeter dust continuum and molecular maser emission. The longest lived outburst (> 6 yr) persists in NGC6334I-MM1, a deeply-embedded object with no near-IR counterpart. Using FORCAST and HAWC+ on SOFIA,
we have obtained the first mid-infrared images of this field since the outburst began. Despite being undetected in pre-outburst
ground-based 18 µm images, MM1 is now the brightest region at all three wavelengths (25, 37, and 53 µm), exceeding the ultracompact HII region MM3 (NGC6334F). Combining the SOFIA data with ALMA imaging at four wavelengths, we construct aspectral energy distribution of the combination of MM1 and the nearby hot core MM2. The best-fit Robitaille radiative transfer
model yields a luminosity of (4.9 ± 0.8) × 104 L . Accounting for an estimated pre-outburst luminosity ratio MM1:MM2 =2.1 ± 0.4, the luminosity of MM1 has increased by a factor of 16.3 ± 4.4. The pre-outburst luminosity implies a protostar of mass
6.7 M , which can produce the ionizing photon rate required to power the pre-outburst hypercompact HII region surrounding
the likely outbursting protostar MM1B. The total energy and duration of the outburst exceed the S255IR-NIRS3 outburst bya factor of & 3, suggesting a different scale of event involving expansion of the protostellar photosphere (to & 20 R ), thereby
supporting a higher accretion rate (&0.0023 M yr−1 ) and reducing the ionizing photon rate. In the grid of hydrodynamic
models of Meyer et al. 2021, the combination of outburst luminosity and magnitude (3) places the NGC6334I-MM1 event in
the region of moderate total accretion (∼0.1-0.3 M ) and hence long duration (∼40-130 yr).

Long-term V (RI)c CCD photometry of pre-main-sequence stars in the association Cepheus

17. OB3

Sunay Ibryamov, Gabriela Zidarova, Evgeni Semkov, Stoyanka Peneva F Results from optical CCD photometricobservations of 13 pre-main-sequence stars collected during the period from February 2007 to November 2020 are presented.
These stars are located in the association Cepheus OB3, in the field of the young star V733 Cephei. Photometric observations,especially concerning the long-term variability of the stars, are missing in the literature. We present the first long-term V (RI)cmonitoring for them, that cover 13 years. Results from our study indicate that all of the investigated stars manifest strong
photometric variability. The presented paper is a part of our program for the photometric study of PMS stars located in active
star-forming regions.

inner regions of protoplanetary discs. I. A detailed model of disc structure
18. MRI-active
Marija R. Jankovic, James E. Owen, Subhanjoy Mohanty, Jonathan C. Tan F Short-period super-Earth-sized planets
are common. Explaining how they form near their present orbits requires understanding the structure of the inner regions ofprotoplanetary discs. Previous studies have argued that the hot inner protoplanetary disc is unstable to the magneto-rotational
instability (MRI) due to thermal ionization of potassium, and that a local gas pressure maximum forms at the outer edge ofthis MRI-active zone. Here we present a steady-state model for inner discs accreting viscously, primarily due to the MRI. The

7

structure and MRI-viscosity of the inner disc are fully coupled in our model; moreover, we account for many processes omitted
in previous such models, including disc heating by both accretion and stellar irradiation, vertical energy transport, realistic
dust opacities, dust effects on disc ionization and non-thermal sources of ionization. For a disc around a solar-mass star witha standard gas accretion rate (Ṁ ∼10−8 M yr−1 ) and small dust grains, we find that the inner disc is optically thick, and theaccretion heat is primarily released near the midplane. As a result, both the disc midplane temperature and the location of
the pressure maximum are only marginally affected by stellar irradiation, and the inner disc is also convectively unstable. As
previously suggested, the inner disc is primarily ionized through thermionic and potassium ion emission from dust grains, which,at high temperatures, counteract adsorption of free charges onto grains. Our results show that the location of the pressure
maximum is determined by the threshold temperature above which thermionic and ion emission become efficient.

19. Gas infalling motions in the envelopes of Very Low Luminosity Objects

Mi-Ryang Kim, Chang Won Lee, Maheswar, G, Philip C. Myers, Gwanjeong Kim F We present the results ofa single dish survey toward 95 VeLLOs in optically thick (HCN 1-0) and thin (N2 H+ 1-0) lines performed for the purpose ofunderstanding the physical processes of inward motions in the envelopes of the VeLLOs and characterizing their true nature.
The normalized velocity differences (δVHCN ) between the peak velocities of the two lines were derived for 41 VeLLOs detectedin both lines. The δV distribution of these VeLLOs is found to be significantly skewed to the blue, indicating the dominanceof infalling motions in their envelopes. The infall speeds were derived for 15 infall candidates by using the HILL5 radiativetransfer model. The speeds were in the range of 0.03 km s−1 to 0.3 km s−1 , with a median value of 0.16 km s−1 , being consistent
with the gravitational free-fall speeds from pressure-free envelopes. The mass infall rates calculated from the infall speeds aremostly of the order of 10−6 M yr−1 with a median value of 3.4 ± 1.5 × 10−6 M yr−1 . These are found to be also consistent
with the values predicted with the inside-out collapse model and show a fairly good correlation with the internal luminosities of
the VeLLOs. This again indicates that the infall motions observed toward the VeLLOs are likely to be due to the gravitational
infall motions in their envelopes. Our study suggests that most of the VeLLOs are potentially faint protostars while two of the
VeLLOs could possibly be proto-brown dwarf candidates.

Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds I. Fractal Theory and

20. Application to Star-Forming Clouds

Lachlan Lancaster, Eve C. Ostriker, Jeong-Gyu Kim, Chang-Goo Kim F Winds from massive stars have velocities of1000 km/s or more, and produce hot, high pressure gas when they shock. We develop a theory for the evolution of bubbles driven
by the collective winds from star clusters early in their lifetimes, which involves interaction with the turbulent, dense interstellar
medium of the surrounding natal molecular cloud. A key feature is the fractal nature of the hot bubble’s surface. The large areaof this interface with surrounding denser gas strongly enhances energy losses from the hot interior, enabled by turbulent mixing
and subsequent cooling at temperatures T = 104 -105 K where radiation is maximally efficient. Due to the extreme cooling, thebubble radius scales differently (R ∼ t1/2 ) from the classical Weaver (1977) solution, and has expansion velocity and momentum
lower by factors of 10-102 at given R, with pressure lower by factors of 102 - 103 . Our theory explains the weak X-ray emission
and low shell expansion velocities of observed sources. We discuss further implications of our theory for observations of the
hot bubbles and cooled expanding shells created by stellar winds, and for predictions of feedback-regulated star formation in arange of environments. In a companion paper, we validate our theory with a suite of hydrodynamic simulations.

Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds II. Validation of Theory

21. with Hydrodynamic Simulations

Lachlan Lancaster, Eve C. Ostriker, Jeong-Gyu Kim, Chang-Goo Kim F In a companion paper, we develop a theory
for the evolution of stellar wind driven bubbles in dense, turbulent clouds. This theory proposes that turbulent mixing at afractal bubble-shell interface leads to highly efficient cooling, in which the vast majority of the input wind energy is radiatedaway. This energy loss renders the majority of the bubble evolution momentum-driven rather than energy-driven, with expansion
velocities and pressures orders of magnitude lower than in the classical Weaver (1977) solution. In this paper, we validate ourtheory with three-dimensional, hydrodynamic simulations. We show that extreme cooling is not only possible, but is generic tostar formation in turbulent clouds over more than three orders of magnitude in density. We quantify the few free parametersin our theory, and show that the momentum exceeds the wind input rate by only a factor about 1.2-4. We verify that the
bubble/cloud interface is a fractal with dimension about 2.5-2.7. The measured turbulent amplitude (vt about 200-400 km/s)
in the hot gas near the interface is shown to be consistent with theoretical requirements for turbulent diffusion to efficiently mix
and radiate away most of the wind energy. The fraction of energy remaining after cooling is only 1-Θ ∼ 0.1-0.01, decreasing
with time, explaining observations that indicate low hot-gas content and weak dynamical effects of stellar winds.

8

22. A Low-mass Cold and Quiescent Core Population in a Massive Protocluster

Shanghuo Li, Xing Lu, Qizhou Zhang, Chang-Won Lee, Patricio Sanhueza, Henrik Beuther, Izaskun, JiménezSerra, Keping Qiu, Aina Palau, Siyi Feng, Thushara Pillai, Kee-Tae Kim, Hong-Li Liu, Josep Miquel. Girart,
Tie Liu, Junzhi Wang, Ke Wang, Hauyu Baobab Liu, Howard A. Smith, Di Li, Jeong-Eun Lee, Fei Li, Juan
Li, Shinyoung Kim, Nannan Yue, Shaye Strom F Pre-stellar cores represent the initial conditions of star formation.
Although these initial conditions have been investigated in detail toward low-mass pre-stellar cores, such initial conditions
remain vastly unexplored for massive star-forming regions. We report the detection of a cluster of low-mass starless and prestellar core candidates in a massive protocluster forming cloud, NGC6334S. With the ALMA observations at a ∼0.02 pc spatial
resolution, we identified 17 low-mass starless core candidates that do not show any evidence of protostellar activity. These
candidates present small velocity dispersions, high fractional abundances of NH2 D, high NH3 deuterium fractionations, and arecompletely dark in the infrared wavelengths from 3.6 up to 70 µm. Turbulence is significantly dissipated and the gas kinematics
are dominated by thermal motions toward these candidates. Nine out of the 17 cores are gravitationally bound, and therefore
are identified as pre-stellar core candidates. The embedded cores of NGC6334S show a wide diversity in masses and evolutionary
stages.

Multi-wavelength Study on the Formation of AFGL 333-Ridge
23. A
XiaoLian Liang, Jin-Long Xu, Ye Xu, Jun-Jie Wang F We presented a multi-wavelength study of AFGL 333-Ridge.
The molecular line data reveals that the AFGL 333-Ridge has two independent velocity components at -50.5 km/s and -48.0
km/s. In the Position-Velocity diagram, the bridge feature connects with two parts that are spatially correlated but separated
in velocity. These observational evidences support the scenario that the two velocity components have collided and merged into
one molecular cloud. The majority of Class I YSOs are distributed within the collision region, suggesting that the cloud-cloud
collision has induced the YSOs formation in the ridge. Using the radio recombination line (RRL) data obtained by the Fivehundred-meter Aperture Spherical radio Telescope (FAST), the RRL velocities of three HII regions are consistent with that of
the AFGL 333-Ridge. By comparing the three HII regions’ dynamical ages with the collision timescale of the two components,
we conclude that the influence of the three HII regions may not drive the two clouds to merge. The formation of the AFGL
333-Ridge is probably due to the expansion of the giant HII region W4.

Ionization Conditions of Sz 102 with Spatially Resolved [Ne III] Microjets
24. Revealing
Chun-Fan Liu, Hsien Shang, Gregory J. Herczeg, Frederick M. Walter F Forbidden neon emission lines from smallscale microjets can probe high-energy processes in low-mass young stellar systems. We obtained spatially resolved [Ne III] spectraof the microjets from the classical T Tauri Star Sz 102 using the Hubble Space Telescope Imaging Spectrograph (HST/STIS) ata spatial resolution of 0".1. The blueshifted and redshifted [Ne III] emission both peak in intensity within 0".1 of the star andgradually decay along the flow outward to 0".24. The spatial distribution and extent of the [Ne III] microjet is consistent witha jet that is ionized close to the base and subsequently recombines on a longer timescale than the flow time. Ca II H and K
lines are also detected from the redshifted microjet with a line full-width at half-maximum of 170 km/s, consistent with thoseof other forbidden emission lines, atop a 300-km/s wide stellar component. The launching radius of the Sz 102 jet, inferredfrom the observed line centroids and the range of inclination angles and stellar masses from the literature, is on the order of
0.03 au. The possible proximity of the launching region to the star allows immediate ionization without distance dilution fromthe circumstellar ionization sources, most likely keV X-ray flares generated by magnetic reconnection events in the star-disk
system, to sustain the observed [Ne III] flux.

Do ultra compact dwarf galaxies form monolithically or as merged star cluster com-

25. plexes?

Hamidreza Mahani, Akram Hasani Zonoozi, Hosein Haghi, Tereza Jerabkova, Pavel Kroupa, Steffen Mieske
F Some ultra-compact dwarf galaxies (UCDs) have elevated observed dynamical V-band mass-to-light (M/LV ) ratios withrespect to what is expected from their stellar populations assuming a canonical initial mass function (IMF). Observations havealso revealed the presence of a compact dark object in the centers of several UCDs, having a mass of a few to 15% of thepresent-day stellar mass of the UCD. This central mass concentration has typically been interpreted as a super-massive blackhole, but can in principle also be a sub-cluster of stellar remnants. We explore the following two formation scenarios of UCDs,i) monolithic collapse and ii) mergers of star clusters in cluster complexes as are observed in massively star-bursting regions.
We explore the physical properties of the UCDs at different evolutionary stages assuming different initial stellar masses of the
UCDs and the IMF being either universal or changing systematically with metallicity and density according to the Integrated
Galactic IMF (IGIMF) theory. While the observed elevated M/LV ratios of the UCDs cannot be reproduced if the IMF isinvariant and universal, the empirically derived IMF which varies systematically with density and metallicity shows agreementwith the observations. Incorporating the UCD-mass-dependent retention fraction of dark remnants improves this agreement.
In addition we apply the results of N-body simulations to young UCDs and show that the same initial conditions describing theobserved M/LV ratios reproduce the observed relation between the half-mass radii and the present-day masses of the UCDs.

9

The findings thus suggest that the majority of UCDs that have elevated M/LV ratios could have formed monolithically withsignificant remnant-mass components that are centrally concentrated, while those with small M/LV values may be mergedstar-cluster complexes.

the ESO data legacy program to complement the Hubble UV Legacy
26. PENELLOPE:
Library of Young Stars (ULLYSES) I. Survey presentation and accretion properties ofOrion OB1 and σ-Orionis

PENELLOPE team - C. F. Manara et al.
F The evolution of young stars and disks is driven by the interplay ofseveral processes, notably accretion and ejection of material. Critical to correctly describe the conditions of planet formation,these processes are best probed spectroscopically. About five-hundred orbits of the Hubble Space Telescope (HST) are being
devoted in 2020-2022 to the ULLYSES public survey of about 70 low-mass (M<2Msun) young (age<10 Myr) stars at UV
wavelengths. Here we present the PENELLOPE Large Program that is being carried out at the ESO Very Large Telescope(VLT) to acquire, contemporaneous to HST, optical ESPRESSO/UVES high-resolution spectra to investigate the kinematics ofthe emitting gas, and UV-to-NIR X-Shooter medium-resolution flux-calibrated spectra to provide the fundamental parametersthat HST data alone cannot provide, such as extinction and stellar properties. The data obtained by PENELLOPE have no
proprietary time, and the fully reduced spectra are made available to the whole community. Here, we describe the data andthe first scientific analysis of the accretion properties for the sample of thirteen targets located in the Orion OB1 associationand in the sigma-Orionis cluster, observed in Nov-Dec 2020. We find that the accretion rates are in line with those observed
previously in similarly young star-forming regions, with a variability on a timescale of days of <3. The comparison of the fits
to the continuum excess emission obtained with a slab model on the X-Shooter spectra and the HST/STIS spectra shows ashortcoming in the X-Shooter estimates of <10uncertainty. Its origin can be either a wrong UV extinction curve or due to thesimplicity of this modelling, and will be investigated in the course of the PENELLOPE program. The combined ULLYSES andPENELLOPE data will be key for a better understanding of the accretion/ejection mechanisms in young stars.

27. Magnetic Properties of Star-Forming Dense Cores

Philip C. Myers, Shantanu Basu F Magnetic and energetic properties are presented for 17 dense cores within a few hundred
pc of the Sun. Their plane-of-sky field strengths are estimated from the dispersion of polarization directions, following Davis,
Chandrasekhar and Fermi (DCF). Their ratio of mass to magnetic critical mass is 0.5-3, indicating nearly critical field strengths.
The field strength Bpos is correlated with column density N as Bpos ∼ Np , where p=1.05±0.08, and with density n as Bpos
∼nq , where q=0.66±0.05. These magnetic properties are consistent with those derived from Zeeman studies (Crutcher et al.
2010), with less scatter. Relations between virial mass MV , magnetic critical mass MB , and Alfven amplitude sigmaB /B matchthe observed range of M/MB for cores observed to be nearly virial, with M/MV =0.5-2, with moderate Alfven amplitudes, andwith sigmaB /B=0.1-0.4. The B-N and B-n correlations in the DCF and Zeeman samples can be explained when such bound,
Alfvenic, and nearly-critical cores have central concentration and spheroidal shape. For these properties, B N because M/MB
is nearly constant compared to the range of N, and B∼n2/3 because M1/3 is nearly constant compared to the range of n2/3 .
The observed core fields which follow B∼n2/3 need not be much weaker than gravity, in contrast to core fields which follow
B∼n2/3 due to spherical contraction at constant mass (Mestel 1966). Instead, the nearly critical values of M/MB suggest thatthe observed core fields are nearly as strong as possible, among values which allow gravitational contraction.

28. Testing the Turbulent Origin of the Stellar Initial Mass Function
D. G. Nam, C. Federrath, M. R. Krumholz F Supersonic turbulence in the interstellar medium (ISM) is closely linked
to the formation of stars, and hence many theories connect the stellar initial mass function (IMF) with the turbulent propertiesof molecular clouds. Here we test three turbulence-based IMF models (by Padoan & Nordlund 2002, Hennebelle & Chabrier
2008, and Hopkins 2012), which predict the relation between the high-mass slope (Γ) of the IMF, dN/d log M ∝ M Γ and theexponent n of the velocity power spectrum of turbulence, Ev (k) ∝ k−n , where n ≈ 2 corresponds to typical ISM turbulence.
Using hydrodynamic simulations, we drive turbulence with an unusual index of n ≈ 1, measure Γ, and compare the results withn ≈ 2. We find that reducing n from 2 to 1 primarily changes the high-mass region of the IMF (beyond the median mass),
where we measure high-mass slopes within the 95 per cent confidence interval of −1.5 < Γ < −1 for n ≈ 1 and −3.7 < Γ < −2.4
for n ≈ 2, respectively. Thus, we find that n = 1 results in a significantly flatter high-mass slope of the IMF, with more massive
stars formed than for n ≈ 2. We compare these simulations with the predictions of the three IMF theories. We find that while
the Padoan & Nordlund theory matches our simulations with fair accuracy, the other theories either fail to reproduce the main
qualitative outcome of the simulations or require some modifications. We conclude that turbulence plays a key role in shaping
the IMF, with a shallower turbulence power spectrum producing a shallower high-mass IMF, and hence more massive stars.

1029. X-ray induced chemistry of water and related molecules in low-mass protostellar envelopes

Shota Notsu, Ewine F. van Dishoeck, Catherine Walsh, Arthur D. Bosman, Hideko Nomura F Recent waterline observations toward several low-mass protostars suggest low water gas fractional abundances in the inner warm envelopes.
Water destruction by X-rays has been proposed to influence the water abundances in these regions, but the detailed chemistry,including the nature of alternative oxygen carriers, is not yet understood. In this study, we aim to understand the impact of
X-rays on the composition of low-mass protostellar envelopes, focusing specifically on water and related oxygen bearing species.
We compute the chemical composition of two low-mass protostellar envelopes using a 1D gas-grain chemical reaction network,
under various X-ray field strengths. According to our calculations, outside the water snowline, the water gas abundance increases
with LX . Inside the water snowline, water maintains a high abundance of ∼ 10−4 for small LX , with water and CO being thedominant oxygen carriers. For large LX , the water gas abundances significantly decrease just inside the water snowline (downto ∼ 10−8 − 10−7 ) and in the innermost regions (∼ 10−6 ). For these cases, the O2 and O gas abundances reach ∼ 10−4 within
the water snowline, and they become the dominant oxygen carriers. The HCO+ and CH3 OH abundances, which have beenused as tracers of the water snowline, significantly increase/decrease within the water snowline, respectively, as the X-ray fluxes
become larger. The abundances of some other dominant molecules, such as CO2 , OH, CH4 , HCN, and NH3 , are also affectedby strong X-ray fields, especially within their own snowlines. These X-ray effects are larger in lower density envelope models.
Future observations of water and related molecules (using e.g., ALMA and ngVLA) will access the regions around protostars
where such X-ray induced chemistry is effective.

30. The double signature of local cosmic-ray acceleration in star-forming regions

Marco Padovani, Alexandre Marcowith, Daniele Galli, Leslie K. Hunt, Francesco Fontani F Recently, there has
been an increased interest in the study of the generation of low-energy cosmic rays (CRs; < 1 TeV) in shocks situated on thesurface of a protostar or along protostellar jets. These locally accelerated CRs offer an attractive explanation for the high levelsof non-thermal emission and ionisation rate, ζ, observed close to these sources. The high ζ observed in some protostellar sources
is generally attributed to shock-generated UV photons. The aim of this article is to show that when synchrotron emission anda high ζ are measured in the same spatial region, a locally shock-accelerated CR flux is sufficient to explain both phenomena.
We assume that relativistic particles are accelerated according to the first-order Fermi acceleration mechanism and compute ζand the non-thermal emission at cm wavelengths. We then apply our model to the star-forming region OMC-2 FIR 3/FIR 4.
Using a Bayesian analysis, we constrain the parameters of the model and estimate the spectral indices of the non-thermal radio
emission. We demonstrate that the local CR acceleration model makes it possible to simultaneously explain the synchrotron
emission along the HOPS 370 jet within the FIR 3 region and ζ observed near the FIR 4 protocluster. Our model constrains themagnetic field strength ( 250-450 µG), its turbulent component ( 20-40 µG), and the jet velocity in the shock reference frame
for the three non-thermal sources of the HOPS 370 jet ( 350-1000 km s−1 ). Beyond the modelling of the OMC-2 FIR 3/FIR
4 system, we show how the combination of continuum observations at cm wavelengths and molecular transitions is a powerful
new tool for the analysis of star-forming regions: these two types of observations can be simultaneously interpreted by invoking
only the presence of locally accelerated CRs, without having to resort to shock-generated UV photons.

31. Modulated accretion in T Tauri star RY Tau – stable MHD propeller or a planet at 0.2
AU?

P. P. Petrov, M. M. Romanova, K. N. Grankin, S. A. Artemenko, E. V. Babina, S. Yu. Gorda F Planets arethought to form at the early stage of stellar evolution when the mass accretion is still ongoing. RY Tau is a T Tauri type star at
the age of a few Myr, with accretion disc seen at high inclination, so that line of sight crosses both the wind and the accretiongas flows. In a long series of spectroscopic monitoring of the star in 2013-2020, we detected variations in H-alpha and NaI D
absorptions at radial velocities of infall (accretion) and outflow (wind) with a period of about 22 days. The absorptions in theinfalling and the outflowing gas streams vary in anti-phase: an increase of infall is accompanied by a decrease of outflow, andvice versa. These flip-flop oscillations retain phase over several years of observations. We suggest that this may result from
the MHD processes at the disk-magnetosphere boundary in the propeller mode. Another possibility is that a massive planet
modulates some processes in the disc and provides the observed effects. The period, if Keplerian, corresponds to a distance of
0.2 AU, which is close to the dust sublimation radius in this star. The presence of the putative planet may be confirmed byradial velocity measurements: expected amplitude is > 90 m/s if a planet mass is > 2 Mj.

32. Significant interstellar object production by close stellar flybys
Susanne Pfalzner, Luis Aizpuru Vargas, Asmita Bhandare, Dimitri Veras F Within just two years, two interstellar
objects (ISOs) - Oumuamuas and Borisov - have been discovered. Large quantities of planetesimals form as a by-product ofplanet formation. Therefore, it seems likely that ISOs are former planetesimals that became unbound from their parent star.
The discoveries raise the question of the dominant ISO formation process. Here, we concentrate on planetesimals released during
another star’s close flybys. We quantify the amount of planetesimals released during close stellar flybys, their ejection velocity

11and likely composition. We study the dependence of the effect of parabolic flybys on the mass ratio between the perturberand parent star, the periastron distance, inclination, and angle of periastron. Whenever ISOs are produced, they leave theirparent system typically with velocities of 0.5-2 km/s. This ejection velocity is distinctly different to that of ISOs produced byplanet scattering (4-8 km/s) and those shed during the stellar post-main-sequence phase 0.1-0.2 km/s). Using the typical disctruncation radius in various cluster environments, we find that clusters like the Orion nebula cluster are likely to produce theequivalent of 0.85 Earth-masses of ISOs per star. In contrast, clusters like NGC 3603 could produce up to 50 Earth-masses ofISOs per star. Our solar system probably produced the equivalent of 2-3 Earth masses of ISOs, which left our solar system ata mean ejection velocity of 0.7 km/s. Most ISOs produced by flybys should be comet-like, similar to Borisov. ISOs originatingfrom compact long-lived clusters would often show a deficiency in CO. As soon as a statistically significant sample of ISOs
is discovered, the combined information of their observed velocities and composition might help in constraining the dominant
production process (abridged).

33. Thiols in the ISM: first detection of HC(O)SH and confirmation of C2 H5 SH

Lucas F. Rodríguez-Almeida, Izaskun Jiménez-Serra, Víctor M. Rivilla, Jesús Martín-Pintado, Shaoshan Zeng,
Belén Tercero, Pablo de Vicente, Laura Colzi, Fernando Rico-Villas, Sergio Martín, Miguel A. Requena-Torres
F The chemical compounds carrying the thiol group (-SH) have been considered essential in recent prebiotic studies regarding
the polymerization of amino acids. We have searched for this kind of compounds toward the Galactic Centre quiescent cloudG+0.693-0.027. We report the first detection in the interstellar space of the trans-isomer of monothioformic acid (t-HC(O)SH)
with an abundance of ∼ 1 × 10−10 . Additionally, we provide a solid confirmation of the gauche isomer of ethyl mercaptan (gC2 H5 SH) with an abundance of ∼ 3 × 10−10 , and we also detect methyl mercaptan (CH3 SH) with an abundance of ∼ 5 × 10−9 .
Abundance ratios were calculated for the three SH-bearing species and their OH-analogues, revealing similar trends between
alcohols and thiols with increasing complexity. Possible chemical routes for the interstellar synthesis of t-HC(O)SH, CH3 SH
and C2 H5 SH are discussed, as well as the relevance of these compounds in the synthesis of prebiotic proteins in the primitive
Earth.

effect of the streaming instability on protoplanetary disc emission at millimetre
34. Thewavelengths
Chiara E. Scardoni, Richard A. Booth, Cathie J. Clarke F In this paper, we investigate whether overdensity formation
via streaming instability is consistent with recent multi-wavelength ALMA observations in the Lupus star forming region. We
simulate the local action of streaming instability in 2D using the code ATHENA, and examine the radiative properties at mm
wavelengths of the resulting clumpy dust distribution by focusing on two observable quantities: the optically thick fraction f f(in ALMA band 6) and the spectral index α (in bands 3-7). By comparing the simulated distribution in the f f − α plane before
and after the action of streaming instability, we observe that clump formation causes f f to drop, because of the suppression ofemission from grains that end up in optically thick clumps. α, instead, can either increase or decline after the action of streaming
instability; we use a simple toy model to demonstrate that this behaviour depends on the sizes of the grains whose emission issuppressed by being incorporated in optically thick clumps. In particular, the sign of evolution of α depends on whether grainsnear the opacity maximum at a few tenths of a mm end up in clumps. By comparing the simulation distributions before/after
clump formation to the data distribution, we note that the action of streaming instability drives simulations towards the area ofthe plane where the data are located. We furthermore demonstrate that this behaviour is replicated in integrated disc models
provided that the instability is operative over a region of the disc that contributes significantly to the total mm flux.

35. Gaia-EDR3 Parallax Distances to the Great Carina Nebula and its Star Clusters (Trumpler 14, 15, 16)

Michael Shull, Jeremy Darling, Charles Danforth F Using offset-corrected Gaia-EDR3 parallax measurements andspectrophotometric methods, we have determined distances for 69 massive stars in the Carina OB1 association and associatedclusters: Trumpler 16 (21 stars), Trumpler 14 (20 stars), Trumpler 15 (3 stars), Bochum 11 (5 stars), and South Pillars region(20 stars). Past distance estimates to the Carina Nebula range from 2.2 to 3.6 kpc, with uncertainties arising from photometry
and anomalous dust extinction. The EDR3 parallax solutions show considerable improvement over DR2, with typical errors
σ$ /$ ≈ 3-5Great Carina Nebula lie at essentially the same distance (2.35 ± 0.08 kpc), quoting mean and rms variance. The
clusters have distances of 2.32±0.12 kpc (Tr 16), 2.37±0.15 kpc (Tr 14), 2.36±0.09 kpc (Tr 15), and 2.33±0.12 kpc (Bochum 11)
in good agreement with the η Car distance of around 2.3 kpc. O-star proper motions suggest internal (2D) velocity dispersions∼ 4 km/s for Tr 14 and Tr 16. Reliable distances allow estimates of cluster sizes, stellar dynamics, luminosities, and fluxes ofphotoionizing radiation incident on photodissociation regions in the region. We estimate that Tr 14 and Tr 16 have half-mass
radii rh = 1.5 − 1.8 pc, stellar crossing times tcr = rh /vm ≈ 0.7 − 0.8 Myr, and two-body relaxation times trh ≈ 40 − 80 Myr.
+5800
The underlying velocity dispersion for Tr 14, if a bound cluster, would be vm ≈ 2.1+0.7−0.4 km/s for N = 7600−2600 stars. With
the higher dispersions of the O-stars, mass segregation might occur slowly, on times scales of 3-6 Myr.

12

Star-disk interaction in the T Tauri star V2129 Oph: An evolving accretion-ejection

36. structure

A. P. Sousa, J. Bouvier, S. H. P. Alencar, J. -F. Donati, E. Alecian, J. Roquette, K. Perraut, C. Dougados, A.
Carmona, S. Covino, D. Fugazza, E. Molinari, C. Moutou, A. Santerne, K. Grankin, É. Artigau, X. Delfosse,
G. Hebrard, the SPIRou consortium F Classical T Tauri stars are young low-mass systems still accreting material fromtheir disks. These systems are dynamic on timescales of hours to years. The observed variability can help us infer the physicalprocesses that occur in the circumstellar environment. We aim at understanding the dynamics of the magnetic interaction
between the star and the inner accretion disk in young stellar objects. We present the case of the young stellar system V2129
Oph, which is a well-known T Tauri star. We performed a time series analysis of this star using high-resolution spectroscopic
data at optical and infrared wavelengths from CFHT/ESPaDOnS, ESO/HARPS and CFHT/SPIRou. The new data setsallowed us to characterize the accretion-ejection structure in this system and to investigate its evolution over a timescale of adecade via comparisons to previous observational data. We measure radial velocity variations and recover a stellar rotation
period of 6.53d. However, we do not recover the stellar rotation period in the variability of various circumstellar lines, such as
Hα and Hβ in the optical or HeI 1083nm and Paβ in the infrared. Instead, we show that the optical and infrared line profile
variations are consistent with a magnetospheric accretion scenario that shows variability with a period of about 6.0d, shorter
than the stellar rotation period. Additionally, we find a period of 8.5d in Hα and Hβ lines, probably due to a structure locatedbeyond the corotation radius, at a distance of 0.09au. We investigate whether this could be accounted for by a wind component,
twisted or multiple accretion funnel flows, or an external disturbance in the inner disk. We conclude that the dynamics of theaccretion-ejection process can vary significantly on a timescale of just a few years, presumably reflecting the evolving magnetic
field topology at the stellar surface.

Undetected Binary Stars Cause an Observed Mass Dependent Age Gradient in Upper

37. Scorpius

Kendall Sullivan, Adam Kraus F Young stellar associations represent a key site for the study of star formation, but toaccurately compare observations to models of stellar evolution, the age of an association must be determined. The Upper
Scorpius region is the youngest section of the Scorpius-Centaurus OB association, which is the largest collection of nearby,
young, low-mass stars. The true age of Upper Scorpius is not clear, and an observed mass-dependent age gradient in Upper
Scorpius, as well as in other star-forming regions, complicates age measurements. The age gradient may indicate a genuine
astrophysical feature or may be an artifact of unrecognized systematic effects in stellar age measurements. We have conducted
a synthetic red-optical low-resolution spectroscopic survey of a simulated analog to the Upper Scorpius star-forming region toinvestigate the effects of unresolved binary stars (which have mass-dependent demographics) on age measurements of a stellar
population. We find that the observed mass-dependent age gradient in Upper Scorpius can be explained by a population of
undetected binary stars. For a simulated population with an age of 10 (RMS = 2) Myr, we measure an age of 10.5 (RMS =3.5) Myr for F stars, and 7.5 (RMS = 5.8) Myr for M stars. This discrepancy is caused by the mass-dependent mass ratio
distribution and the variable steepness of the mass-luminosity relation. Our results support the previously suggested 10 Myr
age for Upper Scorpius, with a small intrinsic age spread.

38. The C O core mass function toward Orion A: Single-dish observations
18

Hideaki Takemura, Fumitaka Nakamura, Shun Ishii, Yoshito Shimajiri, Patricio Sanhueza, Takashi Tsukagoshi,
Ryohei Kawabe, Tomoya Hirota, Akimasa Kataoka F We have performed an unbiased dense core survey toward theOrion A Giant Molecular Cloud in the C18 O (J=1–0) emission line taken with the Nobeyama Radio Observatory (NRO) 45-m
telescope. The effective angular resolution of the map is 26", which corresponds to ∼ 0.05 pc at a distance of 414 pc. By
using the Herschel-Planck H2 column density map, we calculate the C18 O fractional abundance and find that it is roughly
constant over the column density range of . 5 × 1022 cm−3 , although a trend of C18 O depletion is determined toward higher
column density. Therefore, C18 O intensity can follow the cloud structure reasonably well. The mean C18 O abundance in Orion
A is estimated to be 5.7×10−7 , which is about 3 times larger than the fiducial value. We identified 746 C18 O cores withastrodendro and classified 709 cores as starless cores. We compute the core masses by decomposing the Herschel-Planck dustcolumn density using the relative proportions of the C18 O integrated intensities of line-of-sight components. Applying thisprocedure, we attempt to remove the contribution of the background emission, i.e., the ambient gas outside the cores. Then,
we derived mass function for starless cores and found that it resembles the stellar initial mass function (IMF). The CMF forstarless cores, dN/dM , is fitted with a power-law relation of M α with a power index of α = −2.25± 0.16 at the high-mass slope(& 0.44 M ). We also found that the ratio of each core mass to the total mass integrated along the line of sight is significantly
large. Therefore, in the previous studies, the core masses derived from the dust image are likely to be overestimated at least bya factor of a few. Accordingly, such previous studies may underestimate the star formation efficiency of individual cores.

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Core Mass Function in the Orion Nebula Cluster Region: What Determines the
39. TheFinal Stellar Masses?
Hideaki Takemura, Fumitaka Nakamura, Shuo Kong, Héctor G. Arce, John M. Carpenter, Volker OssenkopfOkada, Ralf Klessen, Patricio Sanhueza, Yoshito Shimajiri, Takashi Tsukagoshi, Ryohei Kawabe, Shun Ishii,
Kazuhito Dobashi, Tomomi Shimoikura, Paul F. Goldsmith, Álvaro Sánchez-Monge, Jens Kauffmann, Thushara
Pillai, Paolo Padoan, Adam Ginsberg, Rowan J. Smith, John Bally, Steve Mairs, Jaime E. Pineda, Dariusz
C. Lis, Blakesley Burkhart, Peter Schilke, Hope How-Huan Chen, Andrea Isella, Rachel K. Friesen, Alyssa
A. Goodman, Doyal A. Harper F Applying dendrogram analysis to the CARMA-NRO C18 O (J=1–0) data having anangular resolution of ∼ 8", we identified 692 dense cores in the Orion Nebula Cluster (ONC) region. Using this core sample,
we compare the core and initial stellar mass functions in the same area to quantify the step from cores to stars. About 22 %of the identified cores are gravitationally bound. The derived core mass function (CMF) for starless cores has a slope similar
to Salpeter’s stellar initial mass function (IMF) for the mass range above 1 M , consistent with previous studies. Our CMF
has a peak at a subsolar mass of ∼ 0.1 M , which is comparable to the peak mass of the IMF derived in the same area. We
also find that the current star formation rate is consistent with the picture in which stars are born only from self-gravitatingstarless cores. However, the cores must gain additional gas from the surroundings to reproduce the current IMF (e.g., its slope
and peak mass), because the core mass cannot be accreted onto the star with a 100% efficiency. Thus, the mass accretion fromthe surroundings may play a crucial role in determining the final stellar masses of stars.

OB4: a new association in Gaia DR2
40. Monoceros
P. S. Teixeira, J. Alves, A. Sicilia-Aguilar, A. Hacar, A. Scholz F We use Gaia DR2 data to survey the classic
Monoceros OB1 region and look for the existence of a dispersed young population, co-moving with the cloud complex. An
analysis of the distribution of proper motions reveals a 20-30 Myr association of young stars, about 300-400 pc away from thefar side of the Mon OB1 complex, along the same general line-of-sight. We characterize the new association, Monoceros OB4,
and estimate it contains between 1400 and 2500 stars, assuming a standard IMF, putting it on par in size with NGC 2264. We
find from the internal proper motions that Mon OB4 is unbound and expanding. Our results seem to unveil a larger and more
complex Monoceros star formation region, suggesting an elongated arrangement that seems to be at least 300 × 60 pc.

41. SOFIA FEEDBACK survey: exploring the dynamics of the stellar wind driven shell of
RCW 49

M. Tiwari, R. Karim, M. W. Pound, M. Wolfire, A. Jacob, C. Buchbender, R. Güsten, C. Guevara, R. D.
Higgins, S. Kabanovic, C. Pabst, O. Ricken, N. Schneider, R. Simon, J. Stutzki, A. G. G. M. Tielens F We unveil
the stellar wind driven shell of the luminous massive star-forming region of RCW 49 using SOFIA FEEDBACK observationsof the [CII] 158 µm line. The complementary dataset of the 12 CO and 13 CO J = 3 - 2 transitions is observed by the APEX
telescope and probes the dense gas toward RCW 49. Using the spatial and spectral resolution provided by the SOFIA and
APEX telescopes, we disentangle the shell from a complex set of individual components of gas centered around RCW 49. We
find that the shell of radius 6 pc is expanding at a velocity of 13 km s−1 toward the observer. Comparing our observed
data with the ancillary data at X-Ray, infrared, sub-millimeter and radio wavelengths, we investigate the morphology of theregion. The shell has a well defined eastern arc, while the western side is blown open and is venting plasma further into thewest. Though the stellar cluster, which is ∼ 2 Myr old gave rise to the shell, it only gained momentum relatively recently as we
calculate the shell’s expansion lifetime ∼ 0.27 Myr, making the Wolf-Rayet star WR20a a likely candidate responsible for theshell’s re-acceleration.

42. The Southern HII Region Discovery Survey. II. The Full Catalog

Trey V. Wenger, J. R. Dawson, John M. Dickey, C. H. Jordan, N. M. McClure-Griffiths, L. D. Anderson, W. P.
Armentrout, Dana S. Balser, T. M. Bania F The Southern HII Region Discovery Survey (SHRDS) is a 900 hour Australia
Telescope Compact Array 4-10 GHz radio continuum and radio recombination line (RRL) survey of Galactic HII regions andinfrared-identified HII region candidates in the southern sky. For this data release, we reprocess all previously published SHRDS
data and include an additional 450 hours of observations. The search for new HII regions is now complete over the range 259
deg < Galactic longitude < 346 deg, |Galactic latitude| < 4 deg for HII region candidates with predicted 6 GHz continuum peakbrightnesses >30 mJy/beam. We detect radio continuum emission toward 730 targets altogether including previously known
nebulae and HII region candidates. By averaging 18 RRL transitions, we detect RRL emission toward 206 previously known
HII regions and 436 HII region candidates. Including the northern sky surveys, over the last decade the HII Region Discovery
Surveys have more than doubled the number of known Galactic HII regions. The census of HII regions in the WISE Catalog
of Galactic HII Regions is now complete for nebulae with 9 GHz continuum flux densities > 250 mJy. We compare the RRL
properties of the newly discovered SHRDS nebulae with those of all previously known HII regions. The median RRL full-widthat half-maximum line width of the entire WISE Catalog HII region population is 23.9 km/s and is consistent between Galactic
quadrants. The observed Galactic longitude-velocity asymmetry in the population of HII regions probably reflects underlying

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spiral structure in the Milky Way.

TMRT K Band Observations towards 26 Infrared Dark Clouds: NH3 , CCS, and
43. TheHC N
3Jinjin Xie, Gary A. Fuller, Di Li, Longfei Chen, Zhiyuan Ren, Jingwen Wu, Yan Duan, Junzhi Wang, Juan
Li, Nicolas Peretto, Tie Liu, Zhiqiang Shen F We present one of the first Shanghai Tian Ma Radio Telescope (TMRT)K Band observations towards a sample of 26 infrared dark clouds (IRDCs). We observed the (1,1), (2,2), (3,3), and (4,4)
transitions of NH3 together with CCS (21 -10 ) and HC3 N J =2-1, simultaneously. The survey dramatically increases the existing
CCS-detected IRDC sample from 8 to 23, enabling a better statistical study of the ratios of carbon-chain molecules (CCM) to
N-bearing molecules in IRDCs. With the newly developed hyperfine group ratio (HFGR) method of fitting NH3 inversion lines,
we found the gas temperature to be between 10 and 18 K. The column density ratios of CCS to NH3 for most of the IRDCs
are less than 10−2 , distinguishing IRDCs from low-mass star-forming regions. We carried out chemical evolution simulations
based on a three-phase chemical model NAUTILUS. Our measurements of the column density ratios between CCM and NH3
are consistent with chemical evolutionary ages of .105 yr in the models. Comparisons of the data and chemical models suggestthat CCS, HC3 N, and NH3 are sensitive to the chemical evolutionary stages of the sources.

Cold Clumps in the lambda Orionis Complex. III. A chemical probe of stellar
44. Planck
feedback on cores in the lambda Orionis cloud
Hee-Weon Yi, Jeong-Eun Lee, Kee-Tae Kim, Tie Liu, Beomdu Lim, Ken’ichi Tatematsu F Massive stars have astrong impact on their local environments. However, how stellar feedback regulates star formation is still under debate. In thiscontext, we studied the chemical properties of 80 dense cores in the Orion molecular cloud complex composed of the Orion A(39 cores), B (26 cores), and lambda Orionis (15 cores) clouds using multiple molecular line data taken with the Korean VeryLong Baseline Interferometry Network (KVN) 21-m telescopes. The lambda Orionis cloud has an H ii bubble surrounding theO-type star lambda Ori, and hence it is exposed to the ultraviolet (UV) radiation field of the massive star. The abundances of
C2H and HCN, which are sensitive to UV radiation, appear to be higher in the cores in the lambda Orionis cloud than those in
the Orion A and B clouds, while the HDCO to H2CO abundance ratios show an opposite trend, indicating a warmer conditionin the lambda Orionis cloud. The detection rates of dense gas tracers such as the N2H+, HCO+, and H13CO+ lines are also
lower in the lambda Orionis cloud. These chemical properties imply that the cores in the lambda Orionis cloud are heated by
UV photons from lambda Ori. Furthermore, the cores in the lambda Orionis cloud do not show any statistically significant
excess in the infall signature of HCO+ (1 - 0), unlike the Orion A and B clouds. Our results support the idea that feedback
from massive stars impacts star formation in a negative way by heating and evaporating dense materials, as in the lambda
Orionis cloud.

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