The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 346 — 23 October 2021
Editor: João Alveswww.starformation.news

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Cover image caption
3D Visualization of stellar nurseries using numerical simulations, each representing different physical extremes in the interstellar
medium. The bitmap-based 3D printing approach faithfully reproduces the subtle density gradient distribution within molecular
clouds, revealing quasi-planar structures frequently obscured in traditional renderings and animations. Credit Imara et al. 2021,
foto by Saurabh Mhatre.
Note from the Editor
The Star Formation Newsletter is now on the web at www.starformation.news. This PDF file contains the monthly Abstracts
and links to the different Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to the SFN is as simple
as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site. Do not remove the LATEX formatting
when submitting to the arXiv. If you do, your abstract will not look great either at the arXiv (which uses MathJax toconvert LATEX math symbols to the web) or the SFN.

Abstracts
1. Molecules with ALMA at Planet-forming Scales (MAPS) XIII: HCO+ and disk ionization structure

Yuri Aikawa, Gianni Cataldi, Yoshihide Yamato, Ke Zhang, Alice S. Booth, Kenji Furuya, Sean M. Andrews,
Jaehan Bae, Edwin A. Bergin, Jennifer B. Bergner, Arthur D. Bosman, L. Ilsedore Cleeves, Ian Czekala,Viviana V. Guzmán, Jane Huang, John D. Ilee, Charles J. Law, Romane Le Gal, Ryan A. Loomis, Francois
Ménard, Hideko Nomura, Karin I. Öberg, Chunhua Qi, Kamber R. Schwarz, Richard Teague, Takashi Tsukagoshi, Catherine Walsh, David J. Wilner F We observed HCO+ J = 1 − 0 and H13 CO+ J = 1 − 0 emission towards
the five protoplanetary disks around IM Lup, GM Aur, AS 209, HD 163296, and MWC 480 as part of the MAPS project.
HCO+ is detected and mapped at 0.3 arcsec resolution in all five disks, while H13 CO+ is detected (SNR> 6σ) towards GM
Aur and HD 163296 and tentatively detected (SNR> 3σ) towards the other disks by a matched filter analysis. Inside a radiusof R ∼ 100 au, the HCO+ column density is flat or shows a central dip. At outer radii (& 100 au), the HCO+ column density
decreases outwards, while the column density ratio of HCO+ /CO is mostly in the range of ∼ 10−5 − 10−4 . We derived the
HCO+ abundance in the warm CO-rich layer, where HCO+ is expected to be the dominant molecular ion. At R & 100 au,
the HCO+ abundance is ∼ 3 × 10−11 − 3 × 10−10 , which is consistent with a template disk model with X-ray ionization. At
the smaller radii, the abundance decreases inwards, which indicates that the ionization degree is lower in denser gas, especiallyinside the CO snow line, where the CO-rich layer is in the midplane. Comparison of template disk models with the column
densities of HCO+ , N2 H+ , and N2 D+ indicates that the midplane ionization rate is & 10−18 s−1 for the disks around IM Lup,
AS 209, and HD 163296. We also find hints of an increased HCO+ abundance around the location of dust continuum gaps in
AS 209, HD 163296, and MWC 480. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

2. Youth analysis of near infrared spectra of young low-mass stars and brown dwarfs

V. Almendros-Abad, K. Mužić, A. Moitinho, A. Krone-Martins, K. Kubiak F We aim at building a method that
efficiently identifies young low-mass stars and brown dwarfs from low-resolution near-infrared spectra, by studying gravitysensitive features and their evolution with age. We built a dataset composed of all publicly available (∼2800) near-infrared
spectra of dwarfs with spectral types between M0 and L3. First, we investigate methods for the derivation of the spectral typeand extinction using comparison to spectral templates, and various spectral indices. Then, we examine gravity-sensitive spectral
indices and apply machine learning methods, in order to efficiently separate young (.10 Myr) objects from the field. Using a
set of six spectral indices for spectral typing, including two newly defined ones (TLI-J and TLI-K), we are able to achieve a
precision below 1 spectral subtype across the entire spectral type range. We define a new gravity-sensitive spectral index (TLI-g)2

that consistently separates young from field objects, showing a performance superior to other indices from the literature. Even
better separation between the two classes can be achieved through machine learning methods which use the entire NIR spectra
as an input. Moreover, we show that the H- and K-bands alone are enough for this purpose. Finally, we evaluate the relative
importance of different spectral regions for gravity classification as returned by the machine learning models. We find that the
H-band broad-band shape is the most relevant feature, followed by the FeH absorption bands at 1.2 µm and 1.24 µm and the
KI doublet at 1.24 µm.

3. Quantifying stochasticity-driven uncertainties in H II region metallicities
Raghav Arora, Mark R. Krumholz, Christoph Federrath F With the advent of Integral Field Units (IFUs), surveys
can now measure metallicities across the discs of nearby galaxies at scales . 100 pc. At such small scales, many of these regions
contain too few stars to fully sample all possible stellar masses and evolutionary states, leading to stochastic fluctuations in
the ionising continuum. The impact of these fluctuations on the line diagnostics used to infer galaxy metallicities is poorly
understood. In this paper, we quantify this impact for six most commonly-used diagnostics. We generate stochastic stellar
populations for galaxy patches with star formation rates varying over a factor of 1000, compute the nebular emission that
results when these stars ionise gas at a wide range of densities, metallicities, and determine how much inferred metallicities
vary with fluctuations in the driving stellar spectrum. We find that metallicities derived from diagnostics that measure multiple
ionisation states of their target elements (e.g. electron temperature methods) are weakly affected (variation < 0.1 dex), but thatlarger fluctuations (∼ 0.4 dex) occur for diagnostics that depend on a single ionisation state. Scatter in the inferred metallicity
is generally largest at low star formation rate and metallicity, and is larger for more sensitive observations than for shallower
ones. The main cause of the fluctuations is stochastic variation in the ionisation state in the nebula in response to the absenceof Wolf-Rayet stars, which dominate the production of & 2 − 3 Ryd photons. Our results quantify the trade-off between line
brightness and diagnostic accuracy, and can be used to optimise observing strategies for future IFU campaigns.

4. Molecules with ALMA at Planet-forming Scales (MAPS) XI: CN and HCN as Tracersof Photochemistry in Disks

Jennifer B. Bergner, Karin I. Oberg, Viviana V. Guzman, Charles J. Law, Ryan A. Loomis, Gianni Cataldi,
Arthur D. Bosman, Yuri Aikawa, Sean M. Andrews, Edwin A. Bergin, Alice S. Booth, L. Ilsedore Cleeves, Ian
Czekala, Jane Huang, John D. Ilee, Romane Le Gal, Feng Long, Hideko Nomura, Francois Menard, Chunhua
Qi, Kamber R. Schwarz, Richard Teague, Takashi Tsukagoshi, Catherine Walsh, David J. Wilner, Yoshihide
Yamato F UV photochemistry in the surface layers of protoplanetary disks dramatically alters their composition relative toprevious stages of star formation. The abundance ratio CN/HCN has long been proposed to trace the UV field in various
astrophysical objects, however to date the relationship between CN, HCN, and the UV field in disks remains ambiguous. As
part of the ALMA Large Program MAPS (Molecules with ALMA at Planet-forming Scales), we present observations of CN
N=1-0 transitions at 0.3” resolution towards five disk systems. All disks show bright CN emission within ∼50-150 au, along witha diffuse emission shelf extending up to 600 au. In all sources we find that the CN/HCN column density ratio increases with disk
radius from about unity to 100, likely tracing increased UV penetration that enhances selective HCN photodissociation in theouter disk. Additionally, multiple millimeter dust gaps and rings coincide with peaks and troughs, respectively, in the CN/HCN
ratio, implying that some millimeter substructures are accompanied by changes to the UV penetration in more elevated disk
layers. That the CN/HCN ratio is generally high (>1) points to a robust photochemistry shaping disk chemical compositions,and also means that CN is the dominant carrier of the prebiotically interesting nitrile group at most disk radii. We also findthat the local column densities of CN and HCN are positively correlated despite emitting from vertically stratified disk regions,indicating that different disk layers are chemically linked. This paper is part of the MAPS special issue of the AstrophysicalJournal Supplement.

5. Unveiling wide-orbit companions to K-type stars in Sco-Cen with Gaia EDR3

Alexander J. Bohn, Christian Ginski, Matthew A. Kenworthy, Eric E. Mamajek, Tiffany Meshkat, Mark J.
Pecaut, Maddalena Reggiani, Christopher R. Seay, Anthony G. A. Brown, Gabriele Cugno, Thomas Henning,
Ralf Launhardt, Andreas Quirrenbach, Emily L. Rickman, Damien Ségransan F Abbreviated. We aim to identify
new low-mass companions to young stars using the astrometric measurements provided by the Gaia space mission and complementary VLT/SPHERE data. We identify companion candidates from a sample of K-type, pre-main sequence stars in the
Scorpius Centaurus association using the early version of the third data release of the Gaia space mission. Based on the provided
positions, proper motions, and magnitudes, we identify all objects within a predefined radius whose differential proper motions
are consistent with a gravitationally bound system. We derive companion masses through comparison with evolutionary tracks.
For seven identified companion candidates we use additional data collected with VLT/SPHERE and VLT/NACO to assess theaccuracy of the properties of the companions based on Gaia photometry alone. We identify 110 comoving companions that havea companionship likelihood of more than 95 %. We identify ten especially intriguing companions that have masses in the browndwarf regime down to 20 MJup . Our high-contrast imaging data confirm both astrometry and photometric masses derived from3

Gaia alone. We discover a new brown dwarf companion, TYC 8252-533-1 B, with a projected separation of approximately
570 au from its Sun-like primary. SED modeling provides a companion mass of 52+17−11 MJup . We show that the Gaia database
can identify low-mass companions at wide separations from their host stars. For K-type Sco-Cen members Gaia can detectsub-stellar objects at projected separations larger than 300 au and is sensitivity limited beyond 1, 000 au with a lower mass limit
down to 20 MJup . A similar analysis of other star-forming regions could significantly enlarge the sample size of such objects andtest formation and evolution theories of planetary systems.

6. Molecules with ALMA at Planet-forming Scales (MAPS). X. Studying deuteration athigh angular resolution toward protoplanetary disks

Gianni Cataldi, Yoshihide Yamato, Yuri Aikawa, Jennifer B. Bergner, Kenji Furuya, Viviana V. Guzmán, Jane
Huang, Ryan A. Loomis, Chunhua Qi, Sean M. Andrews, Edwin A. Bergin, Alice S. Booth, Arthur D. Bosman,
L. Ilsedore Cleeves, Ian Czekala, John D. Ilee, Charles J. Law, Romane Le Gal, Yao Liu, Feng Long, François
Ménard, Hideko Nomura, Karin I. Öberg, Kamber R. Schwarz, Richard Teague, Takashi Tsukagoshi, Catherine
Walsh, David J. Wilner, Ke Zhang F Deuterium fractionation is dependent on various physical and chemical parameters.
Thus, the formation location and thermal history of material in the solar system is often studied by measuring its D/H ratio.
This requires knowledge about the deuteration processes operating during the planet formation era. We aim to study theseprocesses by radially resolving the DCN/HCN (at 0.3" resolution) and N2 D+ /N2 H+ (0.3 to 0.9") column density ratios toward
the five protoplanetary disks observed by the Molecules with ALMA at Planet-forming scales (MAPS) Large Program. DCN
is detected in all five sources, with one newly reported detection. N2 D+ is detected in four sources, two of which are newly
reported detections. We derive column density profiles that allow us to study the spatial variation of the DCN/HCN andN2 D+ /N2 H+ ratios at high resolution. DCN/HCN varies considerably for different parts of the disks, ranging from 10−3 to10−1 . In particular, the inner disk regions generally show significantly lower HCN deuteration compared with the outer disk.
In addition, our analysis confirms that two deuterium fractionation channels are active, which can alter the D/H ratio within
the pool of organic molecules. N2 D+ is found in the cold outer regions beyond ∼50 au, with N2 D+ /N2 H+ ranging between
10−2 and 1 across the disk sample. This is consistent with the theoretical expectation that N2 H+ deuteration proceeds via the
low-temperature channel only. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

7. The GRAVITY Young Stellar Object survey. VII. The inner dusty disks of T Tauri
stars

The GRAVITY Collaboration, K. Perraut et al. F These protoplanetary disks in T Tauri stars play a central rolein star and planet formation. We spatially resolve at sub-au scales the innermost regions of a sample of T Tauri’s disks tobetter understand their morphology and composition. We extended our homogeneous data set of 27 Herbig stars and collected
near-IR K-band observations of 17 T Tauri stars, spanning effective temperatures and luminosities in the ranges of 4000-6000 K
and 0.4-10 Lsun. We focus on the continuum emission and develop semi-physical geometrical models to fit the interferometricdata and search for trends between the properties of the disk and the central star. The best-fit models of the disk’s inner rimcorrespond to wide rings. We extend the Radius-luminosity relation toward the smallest luminosities (0.4-10 Lsun) and findthe R∼L( 1/2) trend is no longer valid, since the K-band sizes measured with GRAVITY are larger than the predicted sizes
from sublimation radius computation. No clear correlation between the K-band half-flux radius and the mass accretion rate isseen. Having magnetic truncation radii in agreement with the K-band GRAVITY sizes would require magnetic fields as strong
as a few kG, which should have been detected, suggesting that accretion is not the main process governing the location of thehalf-flux radius of the inner dusty disk. Our measurements agree with models that take into account the scattered light. The
N-to-K band size ratio may be a proxy for disentangling disks with silicate features in emission from disks with weak and/orin absorption silicate features. When comparing inclinations and PA of the inner disks to those of the outer disks (ALMA) innine objects of our sample, we detect misalignments for four objects.

accretion in magnetized protoplanetary disks
8. Steady-state
Timmy N. Delage, Satoshi Okuzumi, Mario Flock, Paola Pinilla, Natalia Dzyurkevich F [abridged] We present a
1+1D global magnetically-driven disk accretion model that captures the essence of the MRI-driven accretion, without resortingto 3D global non-ideal MHD simulations. The gas dynamics is assumed to be solely controlled by the MRI and hydrodynamic
instabilities. For given stellar and disk parameters, the Shakura-Sunyaev viscosity parameter α is determined self-consistently
under the framework of viscously-driven accretion from detailed considerations of the MRI with non-ideal MHD effects (Ohmic
resistivity and ambipolar diffusion), accounting for disk heating by stellar irradiation, non-thermal sources of ionization, anddust effects on the ionization chemistry. Additionally, the magnetic field strength is constrained and adopted to maximize
the MRI activity. We demonstrate the use of our framework by investigating steady-state MRI-driven accretion in a fiducial
protoplanetary disk model around a solar-type star. We find that the equilibrium solution displays no pressure maximum at thedead zone outer edge, except if a sufficient amount of dust particles have accumulated there before the disk reaches a steady-state
accretion regime. Furthermore, the steady-state accretion solution describes a disk that displays a spatially extended long-lived

4

inner disk gas reservoir (the dead zone) accreting a few 10−9 M .yr−1 . By conducting a detailed parameter study, we find thatthe extend to which the MRI can drive efficient accretion is primarily determined by the total disk gas mass, the representative
grain size, the vertically-integrated dust-to-gas mass ratio, and the stellar X-ray luminosity. A self-consistent time-dependent
coupling between gas, dust, stellar evolution models and our general framework on million-year timescales is required to fully
understand the formation of dead zones and their potential to trap dust particles.

9. The structure and characteristic scales of the HI gas in galactic disksSami Dib, Jonathan Braine, Maheswar Gopinathan, Maritza A. Lara-López, Valery V. Kravtsov, ArchanaSoam, Ekta Sharma, Svitlana Zhukovska, Charles Aouad, José-Antonio Belinchón, George Helou, Di Li F The
spatial distribution of the HI gas in galaxies holds important clues on the physical processes that shape the structure anddynamics of the interstellar medium (ISM). In this work, we quantify the structure of the HI gas in a sample of 33 nearby
galaxies taken from the THINGS Survey using the delta-variance spectrum. The THINGS galaxies display a large diversity
in their spectra, however, there are a number of recurrent features. In many galaxies, we observe a bump in the spectrum on
scales of a few to several hundred pc. We find the characteristic scales associated with the bump to be correlated with galactic
SFR for values of the SFR > 0.5 Msol yr−1 and also with the median size of the HI shells detected in those galaxies. On
larger scales, we observe the existence of two self-similar regimes. The first one, on intermediate scales is shallow and the powerlaw that describes this regime has an exponent in the range [0.1-1] with a mean value of 0.55 which is compatible with thedensity field being generated by supersonic turbulence in the cold phase of the HI gas. The second power law is steeper, witha range of exponents between [0.5-1.5] and a mean value of 1.5. These values are associated with subsonic turbulence which
is characteristic of the warm phase of the HI gas. The spatial scale at which the transition between the two regimes occurs isfound to be ≈ 0.5R25 which is similar to the size of the molecular disk in the THINGS galaxies. Overall, our results suggestthat on scales < 0.5R25 , the structure of the ISM is affected by the effects of supernova explosions. On larger scales (> 0.5 R25 ),stellar feedback has no significant impact, and the structure of the ISM is determined by large scale processes that govern the
dynamics of the gas in the warm neutral medium such as the flaring of the HI disk and the effects of ram pressure stripping.

10. The statistical properties of protostellar discs and their dependence on metallicity

Daniel Elsender, Matthew R. Bate F We present the analysis of the properties of large samples of protostellar discs formed
in four radiation hydrodynamical simulations of star cluster formation. The four calculations have metallicities of 0.01, 0.1, 1
and 3 times solar metallicity. The calculations treat dust and gas temperatures separately and include a thermochemical modelof the diffuse interstellar medium. We find the radii of discs of bound protostellar systems tend to decrease with decreasing
metallicity, with the median characteristic radius of discs in the 0.01 and 3 times solar metallicity calculations being ≈ 20 and≈ 65 au, respectively. Disc masses and radii of isolated protostars also tend to decrease with decreasing metallicity. We find thatthe circumstellar discs and orbits of bound protostellar pairs, and the two spins of the two protostars are all less well alignedwith each other with lower metallicity than with higher metallicity. These variations with metallicity are due to increased small
scale fragmentation due to lower opacities and greater cooling rates with lower metallicity, which increase the stellar multiplicity
and increase dynamical interactions. We compare the disc masses and radii of protostellar systems from the solar metallicity
calculation with recent surveys of discs around Class 0 and I objects in the Orion and Perseus star-forming regions. The masses
and radii of the simulated discs have similar distributions to the observed Class 0 and I discs.

the traits of massive young stellar objects through a multi-scale survey
11. Unveiling
A. J. Frost, R. D. Oudmaijer, W. J. de Wit, S. L. Lumsden F The rarity and deeply embedded nature of stars with
masses larger than 8 solar masses has limited our understanding of their formation. Previous work has shown that complementing
spectral energy distributions with interferometric and imaging data can probe the circumstellar environments of massive youngstellar objects (MYSOs) well. However, complex studies of single objects often use different approaches in their analysis.
Therefore the results of these studies cannot be directly compared. This work aims to obtain the physical characteristics ofa sample of MYSOs at 0.01" scales, at 0.1" scales, and as a whole, which enables us to compare the characteristics of thesources. We apply the same multi-scale method and analysis to a sample of MYSOs. High-resolution interferometric data,near-diffraction-limited imaging data, and a multi-wavelength spectral energy distribution are combined. By fitting simulated
observables derived from 2.5D radiative transfer models of disk-outflow-envelope systems to our observations, the properties ofthe MYSOs are constrained. We find that the observables of all the MYSOs can be reproduced by models with disk-outflowenvelope geometries, analogous to the Class I geometry associated with low-mass protostars. The characteristics of the envelopes
and the cavities within them are very similar across our sample. On the other hand, the disks seem to differ between the objects,
in particular with regards to what we interpret as evidence of complex structures and inner holes. This is comparable to themorphologies observed for low-mass young stellar objects. A strong correlation is found between the luminosity of the central
MYSO and the size of the transition disk-like inner hole for the MYSOs, implying that photoevaporation or the presence ofbinary companions may be the cause.

5the geometrical traits of massive young stellar objects and their discs to a poten12. Tying
tial evolutionary sequence using infrared observations
A. J. Frost, R. D. Oudmaijer, S. L. Lumsden, W-J de Wit F Young massive stars influence their surroundings fromlocal to galactic scales, but the observational challenges associated with their distance and embedded nature has, until the
recent decade, made high-resolution studies of these objects difficult. In particular, comparative analyses of massive youngstellar object (MYSO) discs are currently lacking and our understanding of their evolution is limited. Here, we combine theresults of two studies with the aim to attribute geometrical features to an evolutionary sequence for a sample of seven MYSOs.
The time evolution is based on a near-IR spectral features, while the geometry is determined from a multi size-scale studyof MYSOs. We find that MYSO discs with determined geometrical substructure turn out to be also spectroscopically more
evolved. This implies that disc evolution and dispersal are occurring within MYSOs, similar to low-mass YSO disc evolution,
despite their faster formation timescales.

Subaru Hyper Suprime-Cam Survey of Cygnus OB2 Complex – I: Introduction, Pho-

13. tometry and Source Catalog

Saumya Gupta, Jessy Jose, Surhud More, Swagat R. Das, Gregory J. Herczeg, Manash R. Samal, Zhen Guo,
Prem Prakash, Belinda Damian, Michihiro Takami, Satoko Takahashi, Katsuo Ogura, Tsuyoshi Terai, Tae-Soo
Pyo F Low mass star formation inside massive clusters is crucial to understand the effect of cluster environment on processes
like circumstellar disk evolution, planet and brown dwarf formation. The young massive association of Cygnus OB2, with astrong feedback from massive stars, is an ideal target to study the effect of extreme environmental conditions on its extensive
low-mass population. We aim to perform deep multi-wavelength studies to understand the role of stellar feedback on the IMF,
brown dwarf fraction and circumstellar disk properties in the region. We introduce here, the deepest and widest optical photometry of 1.5◦ diameter region centred at Cygnus OB2 in r2 , i2 , z and Y-filters using Subaru Hyper Suprime-Cam (HSC). This
work presents the data reduction, source catalog generation, data quality checks and preliminary results about the pre-main
sequence sources. We obtain 713,529 sources in total, with detection down to ∼ 28 mag, 27 mag, 25.5 mag and 24.5 mag in r2 ,i2 , z and Y-band respectively, which is ∼ 3 - 5 mag deeper than the existing Pan-STARRS and GTC/OSIRIS photometry. We
confirm the presence of a distinct pre-main sequence branch by statistical field subtraction of the central 180 region. We findthe median age of the region as ∼ 5 ± 2 Myrs with an average disk fraction of ∼ 9%. At this age, combined with AV ∼ 6 - 8
mag, we detect sources down to a mass range ∼ 0.01 - 0.17 M . The deep HSC catalog will serve as the groundwork for further
studies on this prominent active young cluster.
+Imaging the water snowline around protostars with water and HCO isotopologues
14. Merel
L. R. van ’t Hoff, Daniel Harsono, Martijn L. van Gelder, Tien-Hao Hsieh, John J. Tobin, Sigurd S.
Jensen, Naomi Hirano, Jes K. Jørgensen, Edwin A. Bergin, Ewine F. van Dishoeck F The water snowline locationin protostellar envelopes provides crucial information about the thermal structure and the mass accretion process as it can
inform about the occurrence of recent (.1,000 yr) accretion bursts. In addition, the ability to image water emission makes thesesources excellent laboratories to test indirect snowline tracers such as H13 CO+ . We study the water snowline in five protostellar
envelopes in Perseus using a suite of molecular line observations taken with the Atacama Large Millimeter/submillimeter Array(ALMA) at ∼0.200 −0.700 (60–210 au) resolution. B1-c provides a textbook example of compact H18
2 O (31,3 − 22,0 ) and HDO(31,2 − 22,1 ) emission surrounded by a ring of H13 CO+ (J = 2 − 1) and HC18 O+ (J = 3 − 2). Compact HDO surroundedby H13 CO+ is also detected toward B1-bS. The optically thick main isotopologue HCO+ is not suited to trace the snowline
and HC18 O+ is a better tracer than H13 CO+ due to a lower contribution from the outer envelope. However, since a detailed
analysis is needed to derive a snowline location from H13 CO+ or HC18 O+ emission, their true value as snowline tracer will lie
in the application in sources where water cannot be readily detected. For protostellar envelopes, the most straightforward way
to locate the water snowline is through observations of H18
2 O or HDO. Including all sub-arcsecond resolution water observations
from the literature, we derive an average burst interval of ∼10,000 yr, but high-resolution water observations of a larger numberof protostars is required to better constrain the burst frequency.

Nobeyama 45 m Local Spur CO survey. I. Giant molecular filaments and cluster for-15. mation in the Vulpecula OB association

Mikito Kohno, Atsushi Nishimura, Shinji Fujita, Kengo Tachihara, Toshikazu Onishi, Kazuki Tokuda, Yasuo
Fukui, Yusuke Miyamoto, Shota Ueda, Ryosuke Kiridoshi, Daichi Tsutsumi, Kazufumi Torii, Tetsuhiro Minamidani, Kazuya Saigo, Toshihiro Handa, Hidetoshi Sano F We have performed new large-scale 12 CO, 13 CO, andC18 O J =1-0 observations toward the Vulpecula OB association (l ∼ 60◦ ) as part of the Nobeyama 45 m Local Spur CO survey
project. Molecular clouds are distributed over ∼ 100 pc, with local peaks at the Sh 2-86, Sh 2-87, and Sh 2-88 high-massstar-forming regions in the Vulpecula complex. The molecular gas is associated with the Local Spur, which corresponds to thenearest inter-arm region located between the Local Arm and the Sagittarius Arm. We discovered new giant molecular filaments(GMFs) in Sh 2-86, with a length of ∼ 30 pc, width of ∼ 5 pc, and molecular mass of ∼ 4 × 104 M . We also found that Sh 2-86

6

contains the three velocity components at 22, 27, and 33 km s−1 . These clouds and GMFs are likely to be physically associatedwith Sh 2-86 because they have high 12 CO J = 2-1 to J = 1-0 intensity ratios and coincide with the infrared dust emission.
The open cluster NGC 6823 exists at the common intersection of these clouds. We argue that the multiple cloud interaction
scenario, including GMFs, can explain cluster formation in the Vulpecula OB association.

16. Can High-velocity Protostellar Jets Help to Drive Low-velocity Outflow?

Masahiro N. Machida F Using three-dimensional magnetohydrodynamics simulations, the driving of protostellar jets isinvestigated in different star-forming cores with the parameters of magnetic field strength and mass accretion rate. Powerfulhigh-velocity jets appear in strongly magnetized clouds when the mass accretion rate onto the protostellar system is lower thanṀ . 10−3 M yr−1 . On the other hand, even at this mass accretion rate range, no jets appear for magnetic fields of prestellar
clouds as weak as µ0 & 5–10, where µ0 is the mass-to-flux ratio normalized by the critical value (2πG1/2 )−1 . For Ṁ & 10−3 M
yr−1 , although jets usually appear just after protostar formation independent of the magnetic field strength, they soon weaken
and finally disappear. Thus, they cannot help drive the low-velocity outflow when there is no low-velocity flow just before
protostar formation. As a result, no significant mass ejection occurs during the early mass accretion phase either when theprestellar cloud is weaky magnetized or when the mass accretion rate is very high. Thus, protostars formed in such environments
would trace different evolutionary paths from the normal star formation process.

17. Extinction in the Large Magellanic Cloud Bar around NGC1854, NGC1856, and NGC1858
Guido De Marchi, Nino Panagia, Antonino P. Milone F We report on the extinction properties in the fields around theclusters NGC 1854, NGC 1856, and NGC 1858 in the bar of the Large Magellanic Cloud. The colour-magnitude diagrams of
the stars in all these regions show an elongated red giant clump that reveals a variable amount of extinction across these fields,
ranging from Av 0.2 to Av 1.9, including Galactic foreground extinction. The extinction properties nonetheless are remarkably
uniform. The slope of the reddening vectors measured in the (V-I,V) and (B-I,B) colour-magnitude planes is fully in line with
the Av/E(B-V) 5.5 value found in the outskirts of 30 Dor. This indicates the presence of an additional grey extinction component in the optical requiring big grains to be about twice as abundant as in the diffuse Galactic interstellar medium (ISM).
Areas of higher extinction appear to be systematically associated with regions of more intense star formation, as measured by
the larger number of stars more massive than 8 Msun, thus making injection of big grains into the ISM by SNII explosion thelikely mechanism at the origin of the observed grey extinction component.

Why do M dwarfs have more transiting planets?

18. Gijs D. Mulders, Joanna Drążkowska, Nienke van der Marel, Fred J. Ciesla, Ilaria Pascucci F We propose a planet
formation scenario to explain the elevated occurrence rates of transiting planets around M dwarfs compared to sun-like stars
discovered by Kepler. We use a pebble drift and accretion model to simulate the growth of planet cores inside and outside of thesnow line. A smaller pebble size interior to the snow line delays the growth of super-Earths, allowing giant planet cores in theouter disk to form first. When those giant planets reach pebble isolation mass they cut off the flow of pebbles to the inner disk
and prevent the formation of close-in super-Earths. We apply this model to stars with masses between 0.1 and 2 solar mass andfor a range of initial disk masses. We find that the masses of hot super-Earths and of cold giant planets are anti-correlated. The
fraction of our simulations that form hot super-Earths is higher around lower-mass stars and matches the exoplanet occurrence
rates from Kepler. The fraction of simulations forming cold giant planets is consistent with the stellar mass dependence fromradial velocity surveys. A key testable prediction of the pebble accretion hypothesis is that the occurrence rates of super-Earths
should decrease again for M dwarfs near the sub-stellar boundary like Trappist-1.

19. Small Protoplanetary Disks in the Orion Nebula Cluster and OMC1 with ALMA

Justin Otter, Adam Ginsburg, Nicholas P. Ballering, John Bally, J. A. Eisner, Ciriaco Goddi, Richard Plambeck,
Melvyn Wright F The Orion Nebula Cluster (ONC) is the nearest dense star-forming region at ∼400 pc away, making it an
ideal target to study the impact of high stellar density and proximity to massive stars (the Trapezium) on protoplanetary disk
evolution. The OMC1 molecular cloud is a region of high extinction situated behind the Trapezium in which actively formingstars are shielded from the Trapezium’s strong radiation. In this work, we survey disks at high resolution with ALMA at three
wavelengths with resolutions of 0.095 arcsec (3 mm; Band 3), 0.048 arcsec (1.3 mm; Band 6), and 0.030 arcsec (0.85 mm;
Band 7) centered on radio Source I. We detect 127 sources, including 15 new sources that have not previously been detected
at any wavelength. 72 sources are spatially resolved at 3 mm, with sizes from ∼8 - 100 AU. We classify 76 infrared-detectedsources as foreground ONC disks and the remainder as embedded OMC1 disks. The two samples have similar disk sizes, but the
OMC1 sources have a dense and centrally concentrated spatial distribution, indicating they may constitute a spatially distinct
subcluster. We find smaller disk sizes and a lack of large (>75 AU) disks in both our samples compared to other nearby starforming regions, indicating that environmental disk truncation processes are significant. While photoevaporation from nearby
massive Trapezium stars may account for the smaller disks in the ONC, the embedded sources in OMC1 are hidden from this7

radiation and thus must truncated by some other mechanism, possibly dynamical truncation or accretion-driven contraction.

20. V899 Mon: a peculiar eruptive young star close to the end of its outburst

Sunkyung Park, Ágnes Kóspál, Fernando Cruz-Sáenz de Miera, Michał Siwak, Marek Dróżdż, Bernadett
Ignácz, Daniel T. Jaffe, Réka Könyves-Tóth, Levente Kriskovics, Jae-Joon Lee, Jeong-Eun Lee, Gregory N.
Mace, Waldemar Ogłoza, András Pál, Stephen B. Potter, Zsófia Marianna Szabó, Ramotholo Sefako, Hannah
L. Worters F V899 Mon is an eruptive young star showing characteristics of both FUors and EXors. It reached a peakbrightness in 2010, then briefly faded in 2011, followed by a second outburst. We conducted multi-filter optical photometricmonitoring, as well as optical and near-infrared spectroscopic observations of V899 Mon. The light curves and color-magnitude
diagrams show that V899 Mon has been gradually fading after its second outburst peak in 2018, but smaller accretion bursts
are still happening. Our spectroscopic observations taken with Gemini/IGRINS and VLT/MUSE show a number of emission
lines, unlike during the outbursting stage. We used the emission line fluxes to estimate the accretion rate and found that it has
significantly decreased compared to the outbursting stage. The mass loss rate is also weakening. Our 2D spectro-astrometricanalysis of emission lines recovered jet and disk emission of V899 Mon. We found the emission from permitted metallic lines andthe CO bandheads can be modeled well with a disk in Keplerian rotation, which also gives a tight constraint for the dynamicalstellar mass of 2 M . After a discussion of the physical changes that led to the changes in the observed properties of V899
Mon, we suggest this object is finishing its second outburst.

High- and Low-Mass Star Formation: Observation-Based Continuum Modelling
21. Linking
and Physical Conditions
R. L. Pitts, L. E. Kristensen, J. K. Jørgensen, S. J. van der Walt F Astronomers have yet to establish whether highmass protostars form from high-mass prestellar cores, similar to their lower-mass counterparts, or from lower-mass fragments at
the heart of a pre-protostellar cluster undergoing large-scale collapse. Part of the uncertainty is due to a shortage of envelope
structure data on protostars of a few tens of solar masses, where we expect to see a transition from intermediate-mass starformation to the high-mass process. We sought to derive the masses, luminosities, and envelope density profiles for eight sourcesin Cygnus-X, whose mass estimates in the literature placed them in the sampling gap. Combining these sources with similarly
evolved sources in the literature enabled us to perform a meta-analysis of protostellar envelope parameters over six decades insource luminosity. We performed spectral energy distribution (SED) fitting on archival broadband photometric continuum datafrom 1.2 to 850 µm, to derive bolometric luminosities for our eight sources plus initial mass and radius estimates for modelling
density and temperature profiles with the radiative transfer package Transphere. The envelope masses, densities at 1000 AU,
outer envelope radii, and density power law indices as functions of bolometric luminosity all follow established trends in theliterature spanning six decades in luminosity. Most of our sources occupy an intermediate to moderately high range of masses
and luminosities, which helps to more firmly establish the continuity between low- and high-mass star formation mechanisms.
Our density power law indices are consistent with observed values in literature, which show no discernible trends with luminosity.
Finally, we show that the trends in all of the envelope parameters for high-mass protostars are statistically indistinguishable
from trends in the same variables for low- and intermediate-mass protostars.

the Cygnus OB associations
22. Revisiting
Alexis L. Quintana, Nicholas J. Wright F OB associations play an important role in Galactic evolution, though their
origins and dynamics remain poorly studied, with only a small number of systems analysed in detail. In this paper we revisit
the existence and membership of the Cygnus OB associations. We find that of the historical OB associations only Cyg OB2
and OB3 stand out as real groups. We search for new OB stars using a combination of photometry, astrometry, evolutionarymodels and an SED fitting process, identifying 4680 probable OB stars with a reliability of >90%. From this sample we search
for OB associations using a new and flexible clustering technique, identifying 6 new OB associations. Two of these are similar
to the associations Cyg OB2 and OB3, though the others bear no relationship to any existing systems. We characterize theproperties of the new associations, including their velocity dispersions and total stellar masses, all of which are consistent withtypical values for OB associations. We search for evidence of expansion and find that all are expanding, albeit anistropically,
with stronger and more significant expansion in the direction of Galactic longitude. We also identify two large-scale (160 pc and
25 km s−1 ) kinematic expansion patterns across the Cygnus region, each including three of our new associations, and attribute
this to the effects of feedback from a previous generation of stars. This work highlights the need to revisit the existence andmembership of the historical OB associations, if they are to be used to study their properties and dynamics.

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the evolutionary timescales of the massive star formation process through23. Establishingchemistry
G. Sabatini, S. Bovino, A. Giannetti, T. Grassi, J. Brand, E. Schisano, F. Wyrowski, S. Leurini, K. M. Menten
F (Abridged) Understanding the details of the formation process of massive (i.e. M<8-10M ) stars is a long-standing problem
in astrophysics. [...] We present a method to derive accurate timescales of the different evolutionary phases of the high-massstar formation process. We model a representative number of massive clumps of the ATLASGAL-TOP100 sample which cover
all the evolutionary stages. The models describe an isothermal collapse and the subsequent warm-up phase, for which we follow
their chemical evolution. The timescale of each phase is derived by comparing the results of the models with the properties ofthe sources of the ATLASGAL-TOP100 sample, taking into account the mass and luminosity of the clumps, and the column
densities of methyl acetylene (CH3 CCH), acetonitrile (CH3 CN), formaldehyde (H2 CO) and methanol (CH3 OH). We find thatthe chosen molecular tracers are affected by the thermal evolution of the clumps, showing steep ice evaporation gradients from
103 to 105 AU during the warm-up phase. We succeed in reproducing the observed column densities of CH3 CCH and CH3 CN,
while H2 CO and CH3 OH show a poorer agreement with the observed values. The total (massive) star formation time is foundto be ∼ 5.2 × 105 yr, which is defined by the timescales of the individual evolutionary phases of the ATLASGAL-TOP100
sample: ∼ 5 × 104 yr for 70-µm weak, ∼ 1.2 × 105 yr for mid-IR weak, ∼ 2.4 × 105 yr for mid-IR bright and ∼ 1.1 × 105 yr for
HII-regions phases. Our models, with an appropriate selection of molecular tracers that can act as chemical clocks, allow to getrobust estimates of the duration of the individual phases of the high-mass star formation process, with the advantage of being
capable to include additional tracers aimed at increasing the accuracy of the estimated timescales.

24. Stellar Rotation of T Tauri stars in the Orion Star-Forming Complex

Javier Serna, Jesús Hernández, Marina Kounkel, Ezequiel Manzo-Martínez, Alexandre Roman-Lopes, Carlos
G. Román-Zuñiga, Maria Gracia Batista, Giovanni Pinzón, Nuria Calvet, Cesar Briceño, Mauricio Tapia,
Genaro Suárez, Karla Peña Ramirez, Keivan G. Stassun, Kevin Covey, Jaime Vargas-González, José Gregorio
Fernández-Trincado F We present a large-scale study of stellar rotation for T Tauri stars in the Orion Star-Forming Complex.
We use the projected rotational velocity (v sin(i)) estimations reported by the APOGEE-2 collaboration as well as individual
masses and ages derived from the position of the stars in the HR diagram, considering Gaia-EDR3 parallaxes and photometry
plus diverse evolutionary models. We find an empirical trend for v sin(i) decreasing with age for low-mass stars (0.4M < M∗ <1.2M ). Our results support the existence of a mechanism linking v sin(i) to the presence of accreting protoplanetary disks,
responsible for regulating stellar rotation in timescales of about 6 Myr, which is the timescale in which most of the T Tauristars lose their inner disk. Our results provide important constraints to models of rotation in the early phases of evolution ofyoung stars and their disks.

Revised Description of the Cosmic Ray-Induced Desorption of Interstellar Ices
25. A
O. Sipilä, K. Silsbee, P. Caselli F Non-thermal desorption of ices on interstellar grains is required to explain observationsof molecules that are not synthesized efficiently in the gas phase in cold dense clouds. Perhaps the most important non-thermal
desorption mechanism is one induced by cosmic rays (CRs), which, when passing through a grain, heat it transiently to a hightemperature - the grain cools back to its original equilibrium temperature via the (partial) sublimation of the ice. Current
cosmic-ray-induced desorption (CRD) models assume a fixed grain cooling time. In this work we present a revised descriptionof CRD in which the desorption efficiency depends dynamically on the ice content. We apply the revised desorption scheme
to two-phase and three-phase chemical models in physical conditions corresponding to starless and prestellar cores, and tomolecular cloud envelopes. We find that inside starless and prestellar cores, introducing dynamic CRD can decrease gas-phaseabundances by up to an order of magnitude in two-phase chemical models. In three-phase chemical models our model producesvery similar results to the static cooling scheme - when only one monolayer of ice is considered active. Ice abundances are
generally insensitive to variations in the grain cooling time. Further improved CRD models need to take into account additional
effects in the transient heating of the grains, introduced for example by the adoption of a spectrum of CR energies.

VLA Observations of 9 Extended Green Objects in the Milky Way: Ubiquitous Weak,

26. Compact Continuum Emission, and Multi-Epoch Emission from CH3 OH, H2 O, and NH3
MasersA. P. M. Towner, C. L. Brogan, T. R. Hunter, C. J. Cyganowski F We have observed a sample of 9 Extended
Green Objects (EGOs) at 1.3 and 5 cm with the VLA with sub-arcsecond resolution and 7-14 uJy/beam sensitivities in orderto characterize centimeter continuum emission as it first appears in these massive protoclusters. We find EGO-associatedcontinuum emission - within 1 arcsec of the extended 4.5 um emission - in every field, which is typically faint (order 101 -102uJy) and compact (unresolved at 0.3-0.5 arcsec). The derived spectral indices of our 36 total detections are consistent with awide array of physical processes, including both non-thermal (19% of detections) and thermal free-free processes (e.g. ionizedjets and compact HII regions, 78% of sample), and warm dust (1 source). We also find EGO-associated 6.7 GHz CH3 OH and
22 GHz H2 O maser emission in 100% of the sample, and NH3 (3,3) masers in 45%; we do not detect any NH3 (6,6) masers9

at 5.6 mJy/beam sensitivity. We find statistically-significant correlations between radio-distance and bolometric luminosities
at two physical scales and three frequencies, consistent with thermal emission from ionized jets, but no correlation between
water-maser and radio-distance luminosities for our sample. From these data, we conclude that EGOs likely host multiple
different centimeter continuum-producing processes simultaneously. Additionally, at our 1000 au resolution, we find that all
EGOs except G18.89−0.47 contain 1 to 2 massive sources based on the presence of methanol maser groups, which is consistent
with our previous work suggesting that these are typical massive protoclusters in which only one to a few of the YSOs are
massive.

27. Probing the chemical complexity of amines in the ISM: detection of vinylamine (C2 H3 NH2 )and tentative detection of ethylamine (C2 H5 NH2 )Shaoshan Zeng, Izaskun Jiménez-Serra, Víctor M. Rivilla, Jesús Martín-Pintado, Lucas F. Rodríguez-Almeida,
Belén Tercero, Pablo de Vicente, Fernando Rico-Villas, Laura Colzi, Sergio Martín, Miguel A. Requena-Torres
F Amines, in particular primary amines (R-NH2 ) are closely related to the primordial synthesis of amino acids since they sharethe same structural backbone. However, only limited number of amines has been identified in the ISM which prevents us fromstudying their chemistry as well as their relation to pre-biotic species that could lead to the emergence of life. In this letter, we
report the first interstellar detection of vinylamine (C2 H3 NH2 ) and tentative detection of ethylamine (C2 H5 NH2 ) towards the
Galactic Centre cloud G+0.693-0.027. The derived abundance with respect to H2 is (3.3±0.4)×10−10 and (1.9±0.5)×10−10 ,respectively. The inferred abundance ratios of C2 H3 NH2 and C2 H5 NH2 with respect to methylamine (CH3 NH2 ) are ∼0.02 and∼0.008 respectively. The derived abundance of C2 H3 NH2 , C2 H5 NH2 and several other NH2 -bearing species are compared tothose obtained towards high-mass and low-mass star-forming regions. Based on recent chemical and laboratory studies, possible
chemical routes for the interstellar synthesis of C2 H3 NH2 and C2 H5 NH2 are discussed.

28. On the Three-Dimensional Structure of Local Molecular Clouds

Catherine Zucker, Alyssa Goodman, João Alves, Shmuel Bialy, Eric W. Koch, Joshua S. Speagle, Michael
M. Foley, Douglas Finkbeiner, Reimar Leike, Torsten Enßlin, Joshua E. G. Peek, Gordian Edenhofer F We
leverage the 1 pc spatial resolution of the Leike et al. 2020 3D dust map to characterize the three-dimensional structure of
nearby molecular clouds (d . 400 pc). We start by "skeletonizing" the clouds in 3D volume density space to determine their"spines," which we project on the sky to constrain cloud distances with ≈ 1% uncertainty. For each cloud, we determine anaverage radial volume density profile around its 3D spine and fit the profiles using Gaussian and Plummer functions. The
radial volume density profiles are well-described by a two-component Gaussian function, consistent with clouds having broad,lower-density outer envelopes and narrow, higher-density inner layers. The ratio of the outer to inner envelope widths is ≈ 3 : 1.
We hypothesize that these two components may be tracing a transition between atomic and diffuse molecular gas or between theunstable and cold neutral medium. Plummer-like models can also provide a good fit, with molecular clouds exhibiting shallow
power-law wings with density, n, falling off like n−2 at large radii. Using Bayesian model selection, we find that parameterizing
the clouds’ profiles using a single Gaussian is disfavored. We compare our results with 2D dust extinction maps, finding thatthe 3D dust recovers the total cloud mass from integrated approaches with fidelity, deviating only at higher levels of extinction(AV & 2−3 mag). The 3D cloud structure described here will enable comparisons with synthetic clouds generated in simulations,offering unprecedented insight into the origins and fates of molecular clouds in the interstellar medium.

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