The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 372 — 31 December 2023
Editor: João Alveswww.starformation.news

Cover image caption
JWST MIRI instrument image of Beta Pictoris debris disk. The image reveals a curvy branch of dust resembling a cat’s tail,extending from the southwest part of the secondary debris disk. This feature spans about 100 au and is visible only in the
MIRI data. The dust in the tail may be similar to the matter found on comets and asteroids in our solar system, suggesting a
possible dust production event like a collision between asteroids, comets, or planetesimals.
Credits: NASA, ESA, CSA, STScI, Christopher Stark (NASA-GSFC), Kellen Lawson (NASA-GSFC), Jens Kammerer (ESO),
Marshall Perrin (STScI)

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. 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 whensubmitting to the arXiv. If you do, your abstract will not look great either at the arXiv or the SFN.

Abstracts
1. An outburst and FU Ori-type disk of a former low luminosity protostar
Mizna Ashraf, Jessy Jose, Ho-Gyu Lee, Carlos Contreras Peña, Gregory J Herczeg, Hanpu Liu, Doug Johnstone, Jeong-Eun Lee F Strong accretion outbursts onto protostars are associated with emission dominated by aviscously heated disk, which is characterized by high luminosities. We report the discovery and characterizationof a strong mid-IR (3.4, 4.6 µm) outburst in the embedded protostar SSTgbs J21470601+4739394 (hereafter SSTgbsJ214706). SSTgbsJ214706 has steadily brightened in the mid-infrared by ∼ 2 magnitudes over the past decade, as
observed by NEOWISE. Follow-up investigations with the Gemini near-IR spectrograph reveal that SSTgbsJ214706 isa binary system with a spatially extended outflow. The outburst is occurring on the more embedded southeast (SE)component, which dominates the mid- and far-infrared emission from the source. The outbursting component exhibitsa spectrum consistent with an FU Ori-type outburst, including the presence of enhanced absorption observed in themolecular bands of CO. The luminosity of the SE component is estimated to be ∼ 0.23 L before the outburst and∼ 0.95 L during the outburst, which is 1 to 2 orders of magnitude fainter than bonafide FU Ori outbursts. We interpret this eruption as an FU Ori-type outburst, although the possibility of brightening following an extinction episodecannot be ruled out. We discuss the implications and potential explanations for such a low-luminosity eruption.

2. Sub-mm wave polarimetry of IRC+10216
B-G Andersson, Janik Karoly, Pierre Bastien, Archana Soam, Simon Coudé, Mehrnoosh Tahani, Michael S.
Gordon, Sydney Fox-Middleton F We present SCUBA-2/POL-2 850 µm polarimetric observations of the circum-

stellar envelope (CSE) of the carbon-rich asymptotic giant branch (AGB) star IRC+10216. Both FIR and opticalpolarization data indicate grains aligned with their long axis in the radial direction relative to the central star. The
850 µm polarization does not show this simple structure. The 850 µm data are indicative, albeit not conclusive, ofa magnetic dipole geometry. Assuming such a simple dipole geometry, the resulting 850 µm polarization geometry
is consistent with both Zeeman observations and small-scale structure in the CSE. While there is significant spectralline polarization contained within the SCUBA-2 850 µm pass-band for the source, it is unlikely that our broadband
polarization results are dominated by line polarization. To explain the required grain alignment, grain mineralogy
effects, due to either fossil silicate grains from the earlier oxygen-rich AGB phase of the star, or due to the incorporation of ferromagnetic inclusions in the largest grains, may play a role. We argue that the most likely explanation isdue to a new alignment mechanism (arXiv:2009.11304) wherein a charged grain, moving relative to the magnetic field,
precesses around the induced electric field and therefore aligns with the magnetic field. This mechanism is particularly
attractive as the optical, FIR, and sub-mm wave polarization of the carbon dust can then be explained in a consistentway, differing simply due to the charge state of the grains.

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3. α-enhanced Astrochemistry: the Carbon cycle in extreme galactic conditions
Thomas G. Bisbas, Zhi-Yu Zhang, Eda Gjergo, Ying-He Zhao, Gan Luo, Donghui Quan, Xue-Jian Jiang,
Yichen Sun, Theodoros Topkaras, Di Li, Ziyi Guo F Astrochemistry has been widely developed as a power

tool to probe physical properties of the interstellar medium (ISM) in various conditions of the Milky Way (MW)Galaxy, and in near and distant galaxies. Most current studies conventionally apply linear scaling to all elemental
abundances based on the gas-phase metallicity. However, these elements, including carbon and oxygen, are enricheddifferentially by stellar nucleosynthesis and the overall galactic chemical evolution, evident from α-enhancement in
multiple galactic observations such as starbursts, high-redshift star-forming galaxies, and low-metallicity dwarfs. We
perform astrochemical modeling to simulate the impact of an α-enhanced ISM gas cloud on the abundances of the threephases of carbon (C+ , C, CO) dubbed as ‘the carbon cycle’. The ISM environmental parameters considered include two
cosmic-ray ionization rates (ζCR = 10−17 and 10−15 s−1 ), two isotropic FUV radiation field strengths (χ/χ0 = 1 and102 ), and (sub-)linear dust-to-gas relations against metallicity, mimicking the ISM conditions of different galaxy types.
In galaxies with [C/O] < 0, CO, C and C+ all decrease in both abundances and emission, though with differential
biases. The low-J CO emission is found to be the most stable tracer for the molecular gas, while C and C+ trace H2
gas only under limited conditions, in line with recent discoveries of [CI]-dark galaxies. We call for caution when using[CII] 158µm and [CI](1-0) as alternative H2 -gas tracers for both diffuse and dense gas with non-zero [C/O] ratios.

4. Dust growth and evolution in protoplanetary disks

Tilman Birnstiel F Over the past decade, advancement of observational capabilities, specifically the Atacama Large

Millimeter/submillimeter Array (ALMA) and SPHERE instrument, alongside theoretical innovations like pebble accretion, have reshaped our understanding of planet formation and the physics of protoplanetary disks. Despite thisprogress, mysteries persist along the winded path of micrometer-sized dust, from the interstellar medium, throughtransport and growth in the protoplanetary disk, to becoming gravitationally bound bodies. This review outlines ourcurrent knowledge of dust evolution in circumstellar disks, yielding the following insights: • Theoretical and laboratory
studies have accurately predicted the growth of dust particles to sizes that are susceptible to accumulation throughtransport processes like radial drift and settling. • Critical uncertainties in that process remain the level of turbulence, the threshold collision velocities at which dust growth stalls, and the evolution of dust porosity. • Symmetricand asymmetric substructure are widespread. Dust traps appear to be solving several long-standing issues in planet
formation models, and they are observationally consistent with being sites of active planetesimal formation. • In someinstances, planets have been identified as the causes behind substructures. This underlines the need to study earlier
stages of disks to understand how planets can form so rapidly. In the future, better probes of the physical conditionsin optically thick regions, including densities, turbulence strength, kinematics, and particle properties will be essential
for unraveling the physical processes at play.

Dynamics in Star-forming Cores (DiSCo): Project Overview and the First Look toward
5. the B1 and NGC 1333 Regions in Perseus
Che-Yu Chen, Rachel Friesen, Jialu Li, Anika Schmiedeke, David Frayer, Zhi-Yun Li, John Tobin, Leslie W.
Looney, Stella Offner, Lee G. Mundy, Andrew I. Harris, Sarah Church, Eve C. Ostriker, Jaime E. Pineda,
Tien-Hao Hsieh, Ka Ho Lam F The internal velocity structure within dense gaseous cores plays a crucial role inproviding the initial conditions for star formation in molecular clouds. However, the kinematic properties of dense gas
at core scales ( 0.01 - 0.1 pc) has not been extensively characterized because of instrument limitations until the uniquecapabilities of GBT-Argus became available. The ongoing GBT-Argus Large Program, Dynamics in Star-forming
Cores (DiSCo) thus aims to investigate the origin and distribution of angular momenta of star-forming cores. DiSCo
will survey all starless cores and Class 0 protostellar cores in the Perseus molecular complex down to 0.01 pc scaleswith < 0.05 km/s velocity resolution using the dense gas tracer N2 H+ . Here, we present the first datasets from DiSCo
toward the B1 and NGC 1333 regions in Perseus. Our results suggest that a dense core’s internal velocity structure
has little correlation with other core-scale properties, indicating these gas motions may be originated externally fromcloud-scale turbulence. These first datasets also reaffirm the ability of GBT-Argus for studying dense core velocity
structure and provided an empirical basis for future studies that address the angular momentum problem with astatistically broad sample.

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6.

Galaxy to cloud scales
Clare Dobbs F Simulations from the scales of isolated galaxies to clouds have been instrumental in informing us aboutmolecular cloud formation and evolution. Simulations are able to investigate the roles of gravity, feedback, turbulence,heating and cooling, and magnetic fields on the physics of the interstellar medium, and star formation. Compared tosimulations of individual clouds, galactic and sub-galactic scale simulations can include larger galactic scale processes
such as spiral arms, bars, and larger supernovae bubbles, which may influence star formation. Simulations show cloudproperties and lifetimes in broad agreement with observations. Gravity and spiral arms are required to produce more
massive GMCs, whilst stellar feedback, likely photoionisation, leads to relatively short cloud lifetimes. On larger
scales, supernovae may be more dominant in driving the structure and dynamics, but photoionisation may still have arole. In terms of the dynamics, feedback is probably the main driver of velocity dispersions, but large scale processes
such as gravity and spiral arms may also be significant. Magnetic fields are generally found to decrease star formation
on galaxy or cloud scales, and simulations are ongoing to study whether clouds are sub or supercritical on different
scales in galaxy scale simulations. Simulations on subgalactic scales, or zoom in simulations, allow better resolutionof feedback processes, filamentary structure within clouds, and the study of stellar clusters.

7.

Does God play dice with star clusters?
Michael Y. Grudić, Stella S. R. Offner, Dávid Guszejnov, Claude-André Faucher-Giguère, Philip F. Hopkins

F When a detailed model of a stellar population is unavailable, it is most common to assume that stellar masses are
independently and identically distributed according to some distribution: the universal initial mass function (IMF).
However, stellar masses resulting from causal, long-ranged physics cannot be truly random and independent, andthe IMF may vary with environment. To compare stochastic sampling with a physical model, we run a suite of 100
STARFORGE radiation magnetohydrodynamics simulations of low-mass star cluster formation in 2000M clouds thatform ∼ 200 stars each on average. The stacked IMF from the simulated clouds has a sharp truncation at ∼ 28M ,well below the typically-assumed maximum stellar mass Mup ∼ 100 − 150M and the total cluster mass. The sequenceof star formation is not totally random: massive stars tend to start accreting sooner and finish later than the averagestar. However, final cluster properties such as maximum stellar mass and total luminosity have a similar amountof cloud-to-cloud scatter to random sampling. Therefore stochastic sampling does not generally model the stellar
demographics of a star cluster as it is forming, but may describe the end result fairly well, if the correct IMF – andits environment-dependent upper cutoff – are known.

8.

JWST reveals widespread CO ice and gas absorption in the Galactic Center cloudG0.253+0.016
Adam Ginsburg, Ashley T. Barnes, Cara D. Battersby, Alyssa Bulatek, Savannah Gramze, Jonathan D. Henshaw, Desmond Jeff, Xing Lu, E. A. C. Mills, Daniel L. Walker F We report JWST NIRCam observations of

G0.253+0.016, the molecular cloud in the Central Molecular Zone known as The Brick, with the F182M, F187N,
F212N, F410M, F405N, and F466N filters. We catalog 56,146 stars detected in all 6 filters using the crowdsource
package. Stars within and behind The Brick exhibit prodigious absorption in the F466N filter that is produced by a
combination of CO ice and gas. In support of this conclusion, and as a general resource, we present models of CO gas
and ice and CO2 ice in the F466N, F470N, and F410M filters. Both CO gas and ice may contribute to the observed
stellar colors. We show, however, that CO gas does not absorb the Pfβ and Hu lines in F466N, but that these lines
show excess absorption, indicating that CO ice is also present and contributes to observed F466N absorption. The
most strongly absorbed stars in F466N are extincted by ∼ 2 magnitudes, corresponding to > 80% flux loss. Thishigh observed absorption requires very high column densities of CO, requiring total CO column that is in tension withstandard CO abundance and/or gas-to-dust ratios. There is therefore likely to be a greater CO/H2 ratio (XCO > 10−4 )and more dust per H2 molecule (> 0.01) in the Galactic Center than the Galactic disk. Ice and/or gas absorption isobserved even in the cloud outskirts, implying that additional caution is needed when interpreting stellar photometry
in filters that overlap with ice bands throughout our Galactic Center. The widespread CO absorption in our Galactic
Center hints that significant ice absorption is likely present in other galactic centers.

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JOYS+: mid-infrared detection of gas-phase SO2 emission in a low-mass protostar. The
9. case of NGC 1333 IRAS2A: hot core or accretion shock?
M. L. van Gelder, M. E. Ressler, E. F. van Dishoeck, P. Nazari, B. Tabone, J. H. Black, Ł. Tychoniec, L. Francis,
M. Barsony, H. Beuther, A. Caratti o Garatti, Y. Chen, C. Gieser, V. J. M. le Gouellec, P. J. Kavanagh, P. D.
Klaassen, B. W. P. Lew, H. Linnartz, L. Majumdar, G. Perotti, W. R. M. Rocha F JWST/MIRI has sharpened

our infrared eyes toward the star formation process. This paper presents the first mid-infrared detection of gaseous SO2
emission in an embedded low-mass protostellar system. MIRI-MRS observations of the low-mass protostellar binary
NGC 1333 IRAS2A are presented from the JWST Observations of Young protoStars (JOYS+) program, revealing
emission from the SO2 ν3 asymmetric stretching mode at 7.35 micron. The results are compared to those derived fromhigh-angular resolution SO2 data obtained with ALMA. The SO2 emission from the ν3 band is predominantly locatedon ∼ 50 − 100 au scales around the main component of the binary, IRAS2A1. A rotational temperature of 92 ± 8 K
is derived from the ν3 lines. This is in good agreement with the rotational temperature derived from pure rotationallines in the vibrational ground state (i.e., ν = 0) with ALMA (104 ± 5 K). However, the emission of the ν3 lines is
not in LTE given that the total number of molecules predicted by a LTE model is found to be a factor 2 × 104 higher
than what is derived for the ν = 0 state. This difference can be explained by a vibrational temperature that is ∼ 100
K higher than the derived rotational temperature of the ν = 0 state. The brightness temperature derived from thecontinuum around the ν3 band of SO2 is ∼ 180 K, which confirms that the ν3 = 1 level is not collisionally populated
but rather infrared pumped by scattered radiation. This is also consistent with the non-detection of the ν2 bending
mode at 18-20 micron. Given the rotational temperature, the extent of the emission (∼ 100 au in radius), and thenarrow line widths in the ALMA data (3.5 km/s), the SO2 in IRAS2A likely originates from ice sublimation in thecentral hot core around the protostar rather than from an accretion shock at the disk-envelope boundary.

10. The influence of accretion bursts on methanol and water in massive young stellar objects
Rodrigo Guadarrama, Eduard Vorobyov, Christian Rab, Manuel Güdel, Alessio Caratti o Garatti, Andrej
Sobolev F The effect of accretion bursts on massive young stellar objects (MYSOs) represents a new research fieldin the study of young stars and their environment. We aim to investigate the impact of an accretion burst on massive
disks with different types of envelopes and to study the effects of an accretion burst on the temperature structure andthe chemistry of the disk. We focus on water and methanol as chemical species for this paper. The thermochemicalcode of PRODIMO (PROtoplanetary DIsk MOdel) is used to perform simulation of high mass protoplanetary disk
models with different types of envelopes under the presence of an accretion burst. The models in question represent
different evolutionary stages of protostellar objects. We calculate and show the chemical abundances in three phasesof the simulation (pre-burst, burst, and post-burst). More heavily embedded disks show higher temperatures. The
impact of the accretion burst is mainly characterized by the desorption of chemical species present in the disk andenvelope from the dust grains to the gas phase. When the post-burst phase starts, the sublimated species freeze out
again. The degree of sublimation depends strongly on the type of envelope the disk is embedded in. An accretion burst
in more massive envelopes produces stronger desorption of the chemical species. However, our models show that thetimescale for the chemistry to reach the pre-burst state is independent of the type of envelope. The study shows thatthe disk’s temperature increases with a more massive envelope enclosing it. Thus, the chemistry of MYSOs in earlier
stages of their evolution reacts stronger to an accretion burst than at later stages where the envelope has lost mostof its mass or has been dissipated. The study of the impact of accretion bursts could also provide helpful theoreticalcontext to the observation of methanol masers in massive disks.

CMZoom IV. Incipient High-Mass Star Formation Throughout the Central Molecular
11. Zone
H Perry Hatchfield, Cara Battersby, Ashley T. Barnes, Natalie Butterfield, Adam Ginsburg, Jonathan D.
Henshaw, Steven N. Longmore, Xing Lu, Brian Svoboda, Daniel Walker, Daniel Callanan, Elisabeth A. C.
Mills, Luis C. Ho, Jens Kauffmann, J. M. Diederik Kruijssen, Jürgen Ott, Thushara Pillai, Qizhou Zhang F

In this work, we constrain the star-forming properties of all possible sites of incipient high-mass star formation in
the Milky Way’s Galactic Center. We identify dense structures using the CMZoom 1.3mm dust continuum catalog
of objects with typical radii of ∼0.1pc, and measure their association with tracers of high-mass star formation. We
incorporate compact emission at 8, 21, 24, 25, and 70um from MSX, Spitzer, Herschel, and SOFIA, catalogued youngstellar objects, and water and methanol masers to characterize each source. We find an incipient star formation rate(SFR) for the CMZ of 0.08 Msun yr−1 over the next few 105 yr. We calculate upper and lower limits on the CMZ’s
5incipient SFR of 0.45 Msun yr−1 and 0.05 Msun yr−1 respectively, spanning between roughly equal to and several
times greater than other estimates of CMZ’s recent SFR. Despite substantial uncertainties, our results suggest theincipient SFR in the CMZ may be higher than previously estimated. We find that the prevalence of star formation
tracers does not correlate with source volume density, but instead 75% of high-mass star formation is found inregions above a column density ratio (NSM A /NHerschel ) of 1.5. Finally, we highlight the detection of “atoll sources”,
a reoccurring morphology of cold dust encircling evolved infrared sources, possibly representing HII regions in theprocess of destroying their envelopes.

The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). X: Hot
12. Gas Reveals Deeply Embedded Star Formation
Natsuko Izumi, Patricio Sanhueza, Patrick M. Koch, Xing Lu, Shanghuo Li, Giovanni Sabatini, Fernando A.
Olguin, Qizhou Zhang, Fumitaka Nakamura, Ken’ichi Tatematsu, Kaho Morii, Takeshi Sakai, Daniel Tafoya

F Massive infrared dark clouds (IRDCs) are considered to host the earliest stages of high-mass star formation. In
particular, 70 µm dark IRDCs are the colder and more quiescent clouds. At a scale of about 5000 au using formaldehyde(H2CO) emission, we investigate the kinetic temperature of dense cores in 12 IRDCs obtained from the pilot ALMA
Survey of 70 µm dark High-mass clumps in Early Stages (ASHES). Compared to 1.3 mm dust continuum and othermolecular lines, such as C18O and deuterated species, we find that H2CO is mainly sensitive to low-velocity outflow
components rather than to quiescent gas expected in the early phases of star formation. The kinetic temperaturesof these components range from 26 to 300 K. The Mach number reaches about 15 with an average value of about 4,
suggesting that the velocity distribution of gas traced by H2CO is significantly influenced by a supersonic non-thermal
component. In addition, we detect warm line emission from HC3N and OCS in 14 protostellar cores, which requires
high excitation temperatures (Eu/k 100 K). These results show that some of the embedded cores in the ASHES fields
are in an advanced evolutionary stage, previously unexpected for 70 µm dark IRDCs.

13. Spectroastrometric Survey of Protoplanetary Disks with Inner Dust Cavities
Stanley K. Jensen Jr, Sean D. Brittain, Andrea Banzatti, Joan R. Najita, John S. Carr, Joshua Kern, Janus
Kozdon, Jonathan Zrake, Jeffrey Fung F We present high-resolution spectra and spectroastrometric (SA) measure-ments of fundamental rovibrational CO emission from nine nearby (.300 pc) protoplanetary disks where large innerdust cavities have been observed. The emission line profiles and SA signals are fit with a slab disk model that allows
the eccentricity of the disk and intensity of the emission to vary as power laws. Six of the sources are well fit with ourmodel, and three of these sources show asymmetric line profiles that can be fit by adopting a non-zero eccentricity.
The three other sources have components in either their line profile or SA signal that are not captured by our disk
model. Two of these sources (V892 Tau, CQ Tau) have multi-epoch observations that reveal significant variability.
CQ Tau and AB Aur have CO line profiles with centrally-peaked components that are similar to line profiles thathave been interpreted as evidence of molecular gas arising from a wide-angle disk wind. Alternatively, emission froma circumplanetary disk (CPD) could also account for this component. The interpretations of these results can beclarified in the future with additional epochs that will test the variability timescale of these SA signals. We discuss
the utility of using high-resolution spectroscopy for probing the dynamics of gas in the disk and the scenarios that cangive rise to profiles that are not fit with a simple disk model.

Improving Monte Carlo radiative transfer simulations: A shift of framework
14. Anton Krieger, Sebastian Wolf F Monte Carlo radiative transfer (MCRT) simulations are a powerful tool for
determining the appearance of astrophysical objects, analyzing the prevalent physical conditions within them, andinferring their properties on the basis of real observations. Consequently, a broad variety of codes has been implemented
and optimized with the goal of solving this task efficiently. To that end, two distinct frameworks have emerged, namely,
the extinction and the scattering framework, which form the basis of the path determination procedures of those codes.
These procedures affect the step length of simulated photon packages and are used for determining flux estimates.
Despite the fact that these simulations play an important role at present and thus require significant computational
resources, little attention has been paid to the benefits and the drawbacks of both frameworks so far. In this study, weinvestigate their differences and assess their performance with regard to the quality of thereby obtained flux estimates,with a particular focus on the required computational demand. To that end, we use a testbed composed of an infinite
plane-parallel slab, illuminated from one side, and we determine transmitted intensity using MCRT simulations for6both frameworks. We find that there are vast differences between the frameworks with regard to their convergence
speed. The scattering framework outperforms the extinction framework across all considered optical depths andalbedos when solving this task, particularly in the regime of high optical depths. Its implementation can therefore
greatly benefit all modern MCRT codes as it has the potential to significantly reduce required computation times.
Thus, we highly recommend its consideration for various tasks that require MCRT simulations.

Improving Monte Carlo radiative transfer in the regime of high optical depths: The
15. minimum scattering order
Anton Krieger, Sebastian Wolf F Radiative transfer (RT) simulations are a powerful tool that enables the calculationof synthetic images of a wide range of astrophysical objects. These simulations are often based on the Monte Carlo(MC) method, as it provides the needed versatility that allows the consideration of the diverse and often complex
conditions found in those objects. However, this method faces fundamental problems in the regime of high opticaldepths which may result in noisy images and underestimated flux values. In this study, we propose an advanced MCRT
method, i.e., an enforced minimum scattering order that is aimed at providing a minimum quality of determined flux
estimates. For that purpose, we extended our investigations of the scattering order problem and derived an analytic
expression for the minimum number of interactions that depends on the albedo and optical depth of the system, whichneeds to be considered to achieve a certain coverage of the scattering order distribution. The method is based on
the utilization of this estimated minimum scattering order and enforces the consideration of a sufficient number ofinteractions during a simulation. Moreover, we identified two notably distinct cases that shape the kind of complexitythat arises in MCRT simulations: the albedo-dominated and the optical depth-dominated case. Based on that, weanalyzed implications regarding the best usage of a stretching method as a means to alleviate the scattering orderproblem. We find that its most suitable application requires taking into account the albedo and the optical depth.
Then, we argue that the derived minimum scattering order can be used to assess the performance of a stretching
method with regard to the scattering orders its usage promotes. Finally, we stress the need for developing advanced
pathfinding techniques to fully solve the problem of MCRT simulations in the regime of high optical depths.

The CO outflow components ejected by a recent accretion event in B335
16. Chul-Hwan Kim, Jeong-Eun Lee, Carlos Contreras Peña, Doug Johnstone, Gregory J. Herczeg, John J. Tobin,
Neal J. Evans II F Protostellar outflows often present a knotty appearance, providing evidence of sporadic accretionin stellar mass growth. To understand the direct relation between mass accretion and ejection, we analyze thecontemporaneous accretion activity and associated ejection components in B335. B335 has brightened in the mid-IR
by 2.5 mag since 2010, indicating increased luminosity, presumably due to increased mass accretion rate onto theprotostar. ALMA observations of 12CO emission in the outflow reveal high-velocity emission, estimated to have beenejected 4.6 - 2 years before the ALMA observation and consistent with the jump in mid-IR brightness. The consistency
in timing suggests that the detected high-velocity ejection components are directly linked to the most recent accretion
activity. We calculated the kinetic energy, momentum, and force for the ejection component associated with themost recent accretion activity and found that at least, about 1.0% of accreted mass has been ejected. More accurate
information on the jet inclination and the temperature of the ejected gas components will better constrain the ejectedmass induced by the recently enhanced accretion event.

Impact of discontinuous grain size distributions on the spectral energy distribution of
17. debris disks
Minjae Kim, Sebastian Wolf F The collisional evolution of debris disks is expected to result in a characteristic

wavy pattern of the grain size distributions, i.e., an under/overabundance of particles of specific sizes. This perturbed
grain size distribution potentially leaves characteristic patterns in the spectral energy distribution (SED) of the disk
system. We aim to quantify and understand the specific influence of discontinuous particle size distributions on theappearance of debris disks. For this purpose, we consider dust emission models based on two different grain size
distributions, i.e., once with a single and once with a broken power law. We compare the spectral index α (Fν ∝ ν α )in the case of a continuous grain size distribution with that of a discontinuous grain size distribution. We perform
this comparison for central stars with different spectral types and two different disk structures (e.g., slim and broad
debris dust rings). Within the considered parameter space, we find a characteristic difference between the spectral
slopes of the SED in the different scenarios. More specifically, the overabundance of small grains leads to a steeper

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slope in the far-infrared/submillimeter regime, while the spectral index in the mm regime is hardly affected. On theother hand, the underabundance of medium-sized grains results in a slight steepening of the far-infrared slope of SED,
while its primary effect is on the mm slope of SED, causing it to become shallower. We also find that the impactof an overabundance of small dust particles is more pronounced than that of an underabundance of medium-sized
dust particles. Furthermore, we find that the difference between the spectral indices for the two different grain size
distributions is largest for debris disks around brighter central stars and broader disks.

Magnetic Fields in the Central Molecular Zone Influenced by Feedback and Weakly
18. Correlated with Star Formation
Xing Lu, Junhao Liu, Thushara Pillai, Qizhou Zhang, Tie Liu, Qilao Gu, Tetsuo Hasegawa, Pak Shing Li, Xindi
Tang, H Perry Hatchfield, Namitha Issac, Xunchuan Liu, Qiuyi Luo, Xiaofeng Mai, Zhiqiang Shen F Magnetic

fields of molecular clouds in the Central Molecular Zone (CMZ) have been relatively underobserved at sub-parsec
resolution. Here we report JCMT/POL2 observations of polarized dust emission in the CMZ, which reveal magnetic
field structures in dense gas at 0.5 pc resolution. The eleven molecular clouds in our sample including two in thewestern part of the CMZ (Sgr C and a far-side cloud candidate), four around the Galactic longitude 0 (the 50 km
s-1 cloud, CO0.02-0.02, the ‘Stone’ and the ‘Sticks & Straw’ among the Three Little Pigs), and five along the Dust
Ridge (G0.253+0.016, clouds b, c, d, and e/f), for each of which we estimate the magnetic field strength using theangular dispersion function method. The morphologies of magnetic fields in the clouds suggest potential imprints offeedback from expanding H II regions and young massive star clusters. A moderate correlation between the total
viral parameter versus the star formation rate and the dense gas fraction of the clouds is found. A weak correlation
between the mass-to-flux ratio and the star formation rate, and a weak anti-correlation between the magnetic field
and the dense gas fraction are also found. Comparisons between magnetic fields and other dynamic components inclouds suggest a more dominant role of self-gravity and turbulence in determining the dynamical states of the clouds
and affecting star formation at the studied scales.

19. Mid-Infrared Variability of Young Stellar Objects on Timescales of Days to Years
Sieun Lee, Jeong-Eun Lee, Carlos Contreras Peña, Doug Johnstone, Gregory Herczeg, Seonjae Lee F Variability
in the brightness of Young Stellar Objects (YSOs) is a common phenomenon that can be caused by changes in various
factors, including accretion, extinction, disk morphology, interactions between the disk and the stellar photosphere,
and the rotation of hot or cold magnetic spots on the stellar photosphere. Analyzing the variability on different
timescales gives insight into the mechanisms driving the brightness changes in YSOs. We investigate the variabilityof YSOs on both long and short timescales using two mid-infrared datasets: the NEOWISE 7.5-year W2 (4.6µm)
data and the YSOVAR 40-day Spitzer/IRAC2 (4.5µm) data, respectively. We classify the variability types in eachtimescale following Park et al (2021). We find a higher detection rate of variable sources in the short-term (77.6%)
compared to the long-term (43.0%) due to the higher sensitivity of the Spitzer observations. In addition, the higher
cadence of the YSOVAR data results in the weeks-long short-term variability being mostly secular, while the years-long
long-term variability explored with the coarsely sampled NEOWISE data is mostly stochastic. By cross-matching thetwo catalogs, we statistically analyze the variability types exhibited by YSOs across both timescales. The long-term
variability amplitude is mostly three times (up to ten times) greater than the short-term variability. Furthermore, we
evaluate variability on very short (1-2 days) timescales and recover a trend of the increasing amplitude of variability as
the timescales increase. By comprehensively analyzing the variability of YSOs over various timescales, we contributeto a deeper understanding of the underlying mechanisms driving their variability.

20. Dust Polarization of Prestellar and Protostellar Sources in OMC-3

Yuhua Liu, Satoko Takahashi, Masahiro Machida, Kohji Tomisaka, Josep Miquel Girart, Paul T. P. Ho,
Kouichiro Nakanishi, Asako Sato F We present the Atacama Large Millimeter/submillimeter Array (ALMA) ob-

servations of linearly polarized 1.1 mm continuum emission at ∼0.14" (55 au) resolution and CO (J=2−1) emission
at ∼1.5" (590 au) resolution towards one prestellar (MMS 4), four Class 0 (MMS 1, MMS 3, MMS 5, and MMS 6), one
Class I (MMS 7), and one flat-spectrum (MMS 2) sources in the Orion Molecular Cloud 3 region. The dust disk-likestructures and clear CO outflows are detected towards all sources except for MMS 4. The diameters of these disk-likestructures, ranging from 16 au to 97 au, are estimated based on the deconvolved full width half maximum (FWHM)
values obtained from the multi-Gaussian fitting. Polarized emissions are detected towards MMS 2, MMS 5, MMS 6,

8

and MMS 7, while no polarized emission is detected towards MMS 1, MMS 3, and MMS 4. MMS 2, MMS 5, and MMS 7
show organized polarization vectors aligned with the minor axes of the disk-like structures, with mean polarization
fractions ranging from 0.6% to 1.2%. The strongest millimeter source, MMS 6, exhibits complex polarization orientations and a remarkably high polarization fraction of ∼10% around the Stokes I peak, and 15−20% on the arm-likestructure, as reported by Takahashi et al. (2019). The origins of the polarized emission, such as self-scattering anddust alignment due to the magnetic field or radiative torque, are discussed for individual sources. Some disk-likesources exhibit a polarized intensity peak shift towards the nearside of the disk, which supports that the polarized
emission originates from self-scattering.

21. Most-Likely DCF Estimates of Magnetic Field Strength
Philip C. Myers, Ian W. Stephens, Simon Coudé F The Davis-Chandrasekhar-Fermi (DCF) method is widelyused to evaluate magnetic fields in star-forming regions. Yet it remains unclear how well DCF equations estimate themean plane-of-the-sky field strength in a map region. To address this question, five DCF equations are applied to an
idealized cloud map. Its polarization angles have a normal distribution with dispersion σθ ,and its density and velocity
dispersion have negligible variation. Each DCF equation specifies a global field strength BDCF and a distribution of
local DCF estimates. The "most-likely" DCF field strength Bml is the distribution mode (Chen et al. 2022), for whicha correction factor βml = Bml /BDCF is calculated analytically. For each equation βml < 1, indicating that BDCF is abiased estimator of Bml . The values of βml are βml ≈ 0.7 when BDCF ∝ σθ −1 due to turbulent excitation of Afvénic
MHD waves, and βml ≈ 0.9 when BDCF ∝ σθ −1/2 due to non-Alfvénic MHD waves. These statistical correction factors
βml have partial agreement with correction factors βsim obtained from MHD simulations. The relative importance ofthe statistical correction is estimated by assuming that each simulation correction has both a statistical and a physicalcomponent. Then the standard, structure function, and original DCF equations appear most accurate because theyrequire the least physical correction. Their relative physical correction factors are 0.1, 0.3, and 0.4 on a scale from 0
to 1. In contrast the large-angle and parallel-δB equations have physical correction factors 0.6 and 0.7. These results
may be useful in selecting DCF equations, within model limitations.

Evolution of the Angular Momentum of Molecular Cloud Cores in Magnetized Molec22. ular Filaments
Yoshiaki Misugi, Shu-ichiro Inutsuka, Doris Arzoumanian, Yusuke Tsukamoto F The angular momentum of

molecular cloud cores plays a key role in the star formation process. However, the evolution of the angular momentum of molecular cloud cores formed in magnetized molecular filaments is still unclear. In this paper, we perform
three-dimensional magnetohydrodynamics simulations to reveal the effect of the magnetic field on the evolution of theangular momentum of molecular cloud cores formed through filament fragmentation. As a result, we find that theangular momentum decreases by 30% and 50% at the mass scale of 1Msun in the case of weak and strong magnetic
field, respectively. By analyzing the torques exerted on fluid elements, we identify the magnetic tension as the dominant process for angular momentum transfer for mass scales < 3Msun for the strong magnetic field case. This criticalmass scale can be understood semi-analytically as the timescale of magnetic braking. We show that the anisotropy of
the angular momentum transfer due to the presence of strong magnetic field changes the resultant angular momentumof the core only by a factor of two. We also find that the distribution of the angle between the rotation axis andthe magnetic field does not show strong alignment even just before the first core formation. Our results also indicatethat the variety of the angular momentum of the cores are inherited from the difference of the phase of the initial
turbulent velocity field. The variety could contribute to the diversity in size and other properties of protoplanetarydisks recently reported by observations.

23. GIARPS High-resolution Observations of T Tauri stars (GHOST) V. New insights into
disk winds from 3 km/s resolution observations
Brunella Nisini, Manuele Gangi, Teresa Giannini, Simone Antoniucci, Katia Biazzo, Antonio Frasca, Juan M.
Alcala’, Carlo F. Manara, Michael L. Weber F This paper aims at revisit the physical and dynamical properties of

the warm atomic gas in the inner disk region of classical T Tauri stars (CTTs) and relate them to the properties of theouter dusty disk. We used the high resolution (R=115,000) spectra of 36 CTTs observed as part of the GHOsT project
and analysed the profile and luminosity of the brightest optical forbidden lines, namely [OI]630 and 557nm, [SII]406
and 673nm, and [NII]658nm. We find that in about 40% of sources the so-called narrow low-velocity component

9

(NLVC) display a peak velocity compatible with the stellar velocity. In these sources, that typically show lower massaccretion rates and the absence of a jet, the [OI]630nm profiles are well fitted by a simple Keplerian disk model,
indicating that the emission from the disk is dominant with respect to the wind contribution. For transitional disks(TD), no correlation is found between Rkep , derived from the line HWHM, and the size of the dust cavity. We also seean anti-correlation between the [OI] 557/630 nm ratio and Rkep , which suggests that the [OI] emitting region expands
as the gas cools and becomes less dense. We confirmed previous findings on the density and temperature ranges impliedby the line ratios, and additionally constrained the ionisation fraction in the NLVC to be < 0.1. We however discuss
the limits of applying this diagnostic to winds that are not spatially resolved. For the outflow component, we estimatedthe mass-loss for both the disk winds and jets and compared the results with X-ray photoevaporative models. We
conclude that without better knowledge of the wind geometry, and given the limitation of the diagnostics, the mass-loss
in the wind traced by the LVC cannot be constrained better than a factor of 100, with a mass-loss/mass-accretion
ratio spanning between 0.01 and more than 1.

Dust survival in harsh environments – Is photo-evaporation an important destruction
24. mechanism?
Ambra Nanni, Sergio Cristallo, Darko Donevski, Michał J. Michałowski, Michael Romano, Prasad Sawant

F Aims. We investigate the role of photo-evaporation of dust exposed to the radiation field from hot young stars
and planetary nebulae (PNe) as a possible destruction mechanism of dust grains in the interstellar medium (ISM).
Methods. We estimate photo-evaporation induced by the feedback of individual or clustered young stars, of PNe andin the presence of a variable radiation field scaled with the interstellar radiation field. For PNe we investigate dust
photo-evaporation of both dust grains already present in the ISM as well as those formed in the last phases of theevolution of thermally pulsing asymptotic giant branch (TP-AGB) stars. We include dust photo-evaporation rate inmodels of dust evolution in galaxies for different assumptions of the dust growth scenario, dust-to-gas ratios, starformation histories, and initial mass functions of the stars. Results. For all the cases considered, we find that bothphoto-evaporation from young stars and from PNe are negligible with respect to other dust removal processes suchas destruction from supernovae shocks, astration and possibly outflow. Grains are stable against photo-evaporation if
they are exposed to a radiation field which is up to 107 times the interstellar radiation field. Conclusions. Dust grainsof size >= 0.01 microns are not efficiently destroyed by photo-evaporation also in the presence of a strong radiation
field.

25. New Eruptive YSOs from SPICY and WISE

C. Contreras Peña, M. Ashraf, J. E. Lee, G. Herczeg, P. W. Lucas, Z. Guo, D. Johnstone, H. G. Lee, J. JoseF This work presents four high-amplitude variable YSOs (' 3 mag at near- or mid-IR wavelengths) arising from the
SPICY catalog. Three outbursts show a duration that is longer than 1 year, and are still ongoing. And additional
YSO brightened over the last two epochs of NEOWISE observations and the duration of the outburst is thus unclear.
Analysis of the spectra of the four sources confirms them as new members of the eruptive variable class. We find two
YSOs that can be firmly classified as bona fide FUors and one object that falls in the V1647 Ori-like class. Given theuncertainty in the duration of its outburst, an additional YSO can only be classified as a candidate FUor. Continued
monitoring and follow-up of these particular sources is important to better understand the accretion process of YSOs.

Ultraviolet H luminescence in molecular clouds induced by cosmic rays
26. Marco Padovani, 2Daniele Galli, Liam H. Scarlett, Tommaso Grassi, Una S. Rehill, Mark C. Zammit, Igor Bray,
Dmitry V. Fursa F Galactic cosmic rays (CRs) play a crucial role in ionisation, dissociation, and excitation processes

within dense cloud regions where UV radiation is absorbed by dust grains and gas species. CRs regulate the abundanceof ions and radicals, leading to the formation of more and more complex molecular species, and determine the charge
distribution on dust grains. A quantitative analysis of these effects is essential for understanding the dynamical andchemical evolution of star-forming regions. The CR-induced photon flux has a significant impact on the evolution of
the dense molecular medium in its gas and dust components. This study is intended to evaluate the flux of UV photons
generated by CRs to calculate the photon-induced dissociation and ionisation rates of a vast number of atomic andmolecular species, as well as the integrated UV photon flux. Our study takes advantage of recent developments in thedetermination of the spectra of secondary electrons, in the calculation of state-resolved excitation cross sections of H2
by electron impact, and of photodissociation and photoionisation cross sections. We calculate the H2 level population10

of each rovibrational level of the X, B, C, B 0 , D, B 00 , D0 and a states. We then compute the UV photon spectrum of
H2 in its line and continuum components between 72 and 700 nm, with unprecedented accuracy as a function of the CR
spectrum incident on a molecular cloud, the H2 column density, the isomeric H2 composition, and the dust properties.
The resulting photodissociation and photoionisation rates are, on average, smaller than previous determinations bya factor of about 2, with deviations up to a factor of 5. A special focus is given to the photoionisation rates of H2 ,HF, and H2 , as well as to the photodissociation of H2 , which we find to be orders of magnitude higher than previous
estimates.

27. Ultraviolet H2 luminescence in molecular clouds induced by cosmic rays

Marco Padovani, Daniele Galli, Liam H. Scarlett, Tommaso Grassi, Una S. Rehill, Mark C. Zammit, Igor Bray,
Dmitry V. Fursa F Galactic cosmic rays (CRs) play a crucial role in ionisation, dissociation, and excitation processes

within dense cloud regions where UV radiation is absorbed by dust grains and gas species. CRs regulate the abundanceof ions and radicals, leading to the formation of more and more complex molecular species, and determine the charge
distribution on dust grains. A quantitative analysis of these effects is essential for understanding the dynamical andchemical evolution of star-forming regions. The CR-induced photon flux has a significant impact on the evolution of
the dense molecular medium in its gas and dust components. This study is intended to evaluate the flux of UV photons
generated by CRs to calculate the photon-induced dissociation and ionisation rates of a vast number of atomic andmolecular species, as well as the integrated UV photon flux. Our study takes advantage of recent developments in thedetermination of the spectra of secondary electrons, in the calculation of state-resolved excitation cross sections of H2
by electron impact, and of photodissociation and photoionisation cross sections. We calculate the H2 level populationof each rovibrational level of the X, B, C, B 0 , D, B 00 , D0 and a states. We then compute the UV photon spectrum of
H2 in its line and continuum components between 72 and 700 nm, with unprecedented accuracy as a function of the CR
spectrum incident on a molecular cloud, the H2 column density, the isomeric H2 composition, and the dust properties.
The resulting photodissociation and photoionisation rates are, on average, smaller than previous determinations bya factor of about 2, with deviations up to a factor of 5. A special focus is given to the photoionisation rates of H2 ,HF, and H2 , as well as to the photodissociation of H2 , which we find to be orders of magnitude higher than previous
estimates.

28. JWST Reveals Star Formation Across a Spiral Arm in M33

Joshua Peltonen, Erik Rosolowsky, Thomas G. Williams, Eric W. Koch, Andrew Dolphin, Jeremy Chastenet,
Julianne J. Dalcanton, Adam Ginsburg, L. Clifton Johnson, Adam K. Leroy, Theo Richardson, Karin M.
Sandstrom, Sumit K. Sarbadhicary, Adam Smercina, Tobin Wainer, Benjamin F. Williams F Young stellar

objects (YSOs) are the gold standard for tracing star formation in galaxies but have been unobservable beyond theMilky Way and Magellanic Clouds. But that all changed when the James Webb Space Telescope was launched, which
we use to identify YSOs in the Local Group galaxy M33, marking the first time that individual YSOs have been
identified at these large distances. We present MIRI imaging mosaics at 5.6 and 21 microns that cover a significant
portion of one of M33’s spiral arms that has existing panchromatic imaging from the Hubble Space Telescope anddeep ALMA CO measurements. Using these MIRI and Hubble Space Telescope images, we identify point sources
using the new DOLPHOT MIRI module. We identify 793 candidate YSOs from cuts based on colour, proximity togiant molecular clouds (GMCs), and visual inspection. Similar to Milky Way GMCs, we find that higher mass GMCs
contain more YSOs and YSO emission, which further shows YSOs identify star formation better than most tracersthat cannot capture this relationship at cloud scales. We find evidence of enhanced star formation efficiency in thesouthern spiral arm by comparing the YSOs to the molecular gas mass.

29. Surveys of clumps, cores, and condensations in Cygnus-X:Searching for circumstellar
disks
Xing Pan, Keping Qiu, Kai Yang, Yue Cao, Xu Zhang F To investigate whether disk-mediated accretion is theprimary mechanism in high-mass star formation, we have established a survey of a large sample of massive dense
cores within a giant molecular cloud. We used high angular resolution (∼ 1.800 ) observations with SMA to study
the dust emission and molecular line emission of about 50 massive dense cores in Cygnus-X. At a typical distanceof 1.4 kpc for Cygnus-X, these massive dense cores are resolved into ∼ 2000 au condensations. We combined the
CO outflow emission and gas kinematics traced by several high-density tracers to search for disk candidates. We

11extracted hundreds of dust condensations from the SMA 1.3 mm dust continuum emission. The CO data show bipolaror unipolar outflow signatures toward 49 dust condensations. Among them, only 27 sources are detected in dense
gas tracers, which reveals the gas kinematics, and nine sources show evidence of rotating envelopes, suggesting theexistence of embedded accretion disks. The position-velocity diagrams along the velocity gradient of all rotatingcondensations suggest that four condensations are possible to host Keplerian-like disks. A detailed investigation of
the 27 sources detected in dense gas tracers suggests that the nine disk candidates are at earlier evolutionary stages
compared to the remaining 18 sources. Non-detection of rotating disks in our sample may be due to several factors,
including an unknown inclination angle of the rotation axis and an early evolutionary stage of the central source, andthe latter could be important, considering that young and powerful outflows could confuse the observational evidence
for rotation. The detection rate of disk candidates in our sample is 1/3, which confirms that disk accretion is a viablemechanism for high-mass star formation, although it may not be the only one.

AB Aur, a Rosetta stone for studies of planet formation (III): continuum observations
30. at 2 and 7 mm
Pablo Rivière-Marichalar, Enrique Macías, Clément Baruteau, Asunción Fuente, Roberto Neri, Álvaro Ribas,
Gisela Esplugues, David Navarro-Almaida, Mayra Osorio, Guillem Anglada F Observational constraints on dust

properties in protoplanetary disks are key to better understanding disks’ evolution. We continue our exploration of
the protoplanetary disk around AB Aur by characterizing its dust properties. We present ALMA observations at 2.2mm and VLA observations at 6.8 mm. Together with previous ALMA and NOEMA observations at 0.87 and 1.1
mm, these observations are used to compute global spectral index profiles as well as spectral index maps. On theinterpretation side, we present the results of a simple isothermal slab model to help constrain dust properties along
the ring of continuum emission. We also present results of dust radiative transfer calculations based on a disc-planet
hydrodynamical simulation to explain how the azimuthal contrast ratio of the ring emission varies with millimeter
wavelength. The spectral energy distribution and the radial profiles of the spectral index indicate that the radiationfrom the compact source towards the center is not dominated by dust thermal emission, but most likely by free-freeemission originating in the radio jet: it constitutes 93% of the emission at 6.8 mm, and 37% at 0.87 mm. The
protoplanetary disk has a typical spectral index of 2.3. We estimate a dust disk mass of 8×10−5 M which, assuming
a mean gas-to-dust ratio of 40, gives a total disk mass of 3.2×10−3 M . The azimuthal contrast ratio of the ringoutside the millimeter cavity is smaller at 2.2 mm than at 1.1 mm, in agreement with previous findings. The VLA
image shows several knots of 5σ emission all along the ring, which are consistent with the ring emission being nearly
axisymmetric at that wavelength. The decrease in the azimuthal contrast ratio of the ring emission from 0.87 to 6.8mm can be explained by a dust-losing decaying vortex at the outer edge of a planet gap.

31.

The Disk Orientations of Perseus Protostellar Multiples at 8 au Resolution
Nickalas K. Reynolds, John J. Tobin, Patrick D. Sheehan, Sarah I. Sadavoy, Leslie W. Looney, Kaitlin M.
Kratter, Zhi-Yun Li, Dominique M. Segura-Cox, Nathan A. Kaib F We present a statistical characterizationof circumstellar disk orientations toward 12 protostellar multiple systems in the Perseus molecular cloud using the
Atacama Large Millimeter/submillimeter Array at Band 6 (1.3 mm) with a resolution of 25 mas (8 au). This exquisite
resolution enabled us to resolve the compact inner disk structures surrounding the components of each multiple systemand to determine the projected 3-D orientation of the disks (position angle and inclination) to high precision. We
performed a statistical analysis on the relative alignment of disk pairs to determine whether the disks are preferentiallyaligned or randomly distributed. We considered three subsamples of the observations selected by the companion
separations, a <100 au, a >500 au, and a < 10,000 au. We found for the compact (< 100 au) subsample, thedistribution of orientation angles is best described by an underlying distribution of preferentially aligned sources(within 30deg) but does not rule out distributions with 40% misaligned sources. The wide companion (>500 au)
subsample appears to be consistent with a distribution of 40%-80% preferentially aligned sources. Similarly, thefull sample of systems with companions (a< 10000 au) is most consistent with a fractional ratio of at most 80%
preferentially aligned source and rules out purely randomly aligned distributions. Thus our results imply the compact
sources (<100 au) and the wide companions (>500 au) are statistically different.

1232. Ring Gap Structure around Class I Protostar WL 17

Ayumu Shoshi, Naoto Harada, Kazuki Tokuda, Yoshihiro Kawasaki, Hayao Yamasaki, Asako Sato, Mitsuki
Omura, Masayuki Yamaguchi, Kengo Tachihara, Masahiro N. Machida F WL 17 is a Class I object and wasconsidered to have a ring-hole structure. We analyzed the structure around WL 17 to investigate the detailed properties
of WL 17. We used ALMA archival data, which have a higher angular resolution than previous observations. We
investigated the WL 17 system with the 1.3 mm dust continuum and 12CO and C18O (J = 2-1) line emissions. The
dust continuum emission showed a clear ring structure with inner and outer edges of 11 and 21 au, respectively. In
addition, we detected an inner disk of < 5 au radius enclosing the central star within the ring, the first observationof this structure. Thus, WL 17 has a ring-gap structure, not a ring-hole structure. We did not detect any marked
emission in either the gap or inner disk, indicating that there is no sign of a planet, circumplanetary disk, or binary
companion. We identified the base of both blue-shifted and red-shifted outflows based on the 12CO emission, which
is clearly associated with the disk around WL 17. The outflow mass ejection rate is 3.6x10− 7 Msun/yr and the
dynamical timescale is as short as 104 yr. The C18O emission showed that an inhomogeneous infalling envelope,which can induce episodic mass accretion, is distributed in the region within 1000 au from the central protostar. With
these new findings, we can constrain the planet formation and dust growth scenarios in the accretion phase of starformation.

33. Cluster Formation in a Filamentary Cloud: The Case of the Stellar Cluster NGC 2316
Saurabh Sharma, Aayushi Verma, Kshitiz Mallick, Lokesh K. Dewangan, Harmeen Kaur, Ram Kesh Yadav,
Neelam Panwar, Devendra K. Ojha, Tarak Chand, Mamta Agarwal F We present a multi-wavelength analysisof the star cluster NGC 2316 and its surroundings. We estimated the physical parameters of the NGC 2316 cluster,
including its shape (elongated), size (Rcluster = 0.4 pc), distance (1.3 +/- 0.3 kpc), and minimum reddening (AV =1.55 mag). We discovered two massive stars (B2.0V-B1.5V, age 12 Myr) embedded (AV = 4 mag) within this cluster.
The cluster region still forms young stars even though the most massive star was born 12 Myr ago. We also foundevidence of positive feedback from these massive stars. We identified a cold gas/dust lane extending westward from thecluster. The western end of the dust lane seems to favor low-mass star formation, whereas the cluster’s end favors bit
massive star formation, which seems to have started earlier than the western end. We found an elongated molecular
cloud in this region, characterized by numerous filamentary structures. The morphology of the filaments, along withposition-velocity (pv) maps, velocity dispersion maps, channel maps, etc., indicate a coalescence of filaments and apotential longitudinal flow of matter toward the cluster through the western end of the gas/dust lane. This entire
region seems to be a Hub-filamentary system (HFS), in which the NGC 2316 cluster is probably the hub and the darklane is the main filamentary structure. Being the gravity well of this HFS, star formation started first in the NGC
2316 region and went on to the other filamentary nodes.

The Role of Low-energy (< 20 eV) Secondary Electrons in the Extraterrestrial Synthesis
34. of Prebiotic Molecules
Qin Tong Wu, Hannah Anderson, Aurland K. Watkins, Devyani Arora, Kennedy Barnes, Marco Padovani,
Christopher N. Shingledecker, Christopher R. Arumainayagam, James B. R. Battat F We demonstrate for the

first time that Galactic cosmic rays with energies as high as 1e10 eV can trigger a cascade of low-energy (< 20 eV)
secondary electrons that could be a significant contributor to the interstellar synthesis of prebiotic molecules whose
delivery by comets, meteorites, and interplanetary dust particles may have kick-started life on Earth. We explore therelative importance of low-energy (< 20 eV) secondary electrons–agents of radiation chemistry–and low-energy (< 10eV), non-ionizing photons–instigators of photochemistry. Our calculations indicate fluxes of 100 electrons/cm2/s for
low-energy secondary electrons produced within interstellar ices due to incident attenuated Galactic cosmic-ray (CR)
protons. Consequently, in certain star-forming regions where internal high-energy radiation sources produce ionization
rates that are observed to be a thousand times greater than the typical interstellar Galactic ionization rate, the fluxof low-energy secondary electrons should far exceed that of non-ionizing photons. Because reaction cross-sections canbe several orders of magnitude larger for electrons than for photons, even in the absence of such enhancement our
calculations indicate that secondary low-energy electrons are at least as significant as low-energy (< 10 eV) non-ionizing
photons in the interstellar synthesis of prebiotic molecules. Most importantly, our results demonstrate the pressing
need for explicitly incorporating low-energy electrons in current and future astrochemical simulations of cosmic ices.
Such models are critically important for interpreting James Webb Space Telescope infrared measurements, which are
currently being used to probe the origins of life by studying complex organic molecules found in ices near star-forming
13

regions.

The 3D Kinematics of the Orion Nebula Cluster II: Mass-dependent Kinematics of the
35. Inner Cluster
Lingfeng Wei, Christopher A. Theissen, Quinn M. Konopacky, Jessica R. Lu, Chih-Chun Hsu, Dongwon Kim

F We present the kinematic anaylsis of 246 stars within 40 from the center of Orion Nebula Cluster (ONC), the closest
massive star cluster with active star formation across the full mass range, which provides valuable insights in thethe formation and evolution of star cluster on an individual-star basis. High-precision radial velocities and surface
temperatures are retrieved from spectra acquired by the NIRSPEC instrument used with adaptive optics (NIRSPAO)
on the Keck II 10-m telescope. A three-dimensional kinematic map is then constructed by combining with the propermotions previously measured by the Hubble Space Telescope (HST) ACS/WFPC2/WFC3IR and Keck II NIRC2. The
measured root-mean-squared velocity dispersion is 2.26 ± 0.08 km s−1 , significantly higher than the virial equilibrium’s
requirement of 1.73 km s−1 , suggesting that the ONC core is supervirial, consistent with previous findings. Energy
equipartition is not detected in the cluster. Most notably, the velocity of each star relative to its neighbors is found tobe negatively correlated with stellar mass. Low-mass stars moving faster than their surrounding stars in a supervirial
cluster suggests that the initial masses of forming stars may be related to their initial kinematic states. Additionally,a clockwise rotation preference is detected. A weak sign of inverse mass segregation is also identified among stars
excluding the Trapezium stars, though it could be a sample bias. Finally, this study reports the discovery of four new
candidate spectroscopic binary systems.

36. Chemistry of Complex Organic Molecules in the V883 Ori Disk Revealed by ALMABand 3 Observations
Yoshihide Yamato, Shota Notsu, Yuri Aikawa, Yuki Okoda, Hideko Nomura, Nami Sakai F Complex organic

molecules (COMs) in protoplanetary disks are key to understanding the origin of volatiles in comets in our solar
system, yet the chemistry of COMs in protoplanetary disks remains poorly understood. Here we present Atacama
Large Millimeter/submillimeter Array (ALMA) Band 3 observations of the disk around the young outbursting star
V883 Ori, where the COMs sublimate from ices and are thus observable thanks to the warm condition of the disk.
We have robustly identified ten oxygen-bearing COMs including 13 C-isotopologues in the disk-integrated spectra. The
radial distributions of the COM emission, revealed by the detailed analyses of the line profiles, show the inner emission
cavity, similar to the previous observations in Band 6 and Band 7. We found that the COMs abundance ratios withrespect to methanol are significantly higher than those in the warm protostellar envelopes of IRAS 16293-2422 andsimilar to the ratios in the solar system comet 67P/Churyumov-Gerasimenko, suggesting the efficient (re-)formationof COMs in protoplanetary disks. We also constrained the 12 C/13 C and D/H ratios of COMs in protoplanetary disks
for the first time. The 12 C/13 C ratios of acetaldehyde, methyl formate, and dimethyl ether are consistently lower (∼20-30) than the canonical ratio in the interstellar medium (∼ 69), indicating the efficient 13 C-fractionation of CO.
The D/H ratios of methyl formate are slightly lower than the values in IRAS 16293-2422, possibly pointing to thedestruction and reformation of COMs in disks. We also discuss the implications for nitrogen and sulfur chemistry inprotoplanetary disks.

Insights into the first and second hydrostatic core stages from numerical simulations
37. Alison K. Young F The theory of how low mass stars form from the collapse of a dense molecular cloud core has
been well-established for decades. Thanks to significant progress in computing and numerical modelling, more physicalmodels have been developed and a wider parameter space explored to understand the early stages of star formation
more fully. In this review, I describe the expected physical properties of the first and second core stages and how
the inclusion of different physics affects those predicted characteristics. I provide an overview of chemical models andsynthetic observations, looking towards the positive identification of the first core in nature, which remains elusive.
However, there are a few likely candidate first cores, which are listed, and I briefly discuss the recent progress incharacterising the youngest protostellar sources. Chemistry will be instrumental in the firm identification of the firstcore so we require robust theoretical predictions of the chemical evolution of protostellar cores, especially of the firstand second core outflows. Looking ahead, simulations can shed light on how the protostellar collapse phase shapes
the evolution of the protostellar disc. Simulations of dust evolution during protostellar core collapse show there issignificant enhancement in grain size and abundance towards the centre of the core. Chemical models show that the14

warm, dense conditions of the first core drive chemical evolution. There is a wide scope for further study of the rolethat the first and second core stages play in determining the structure and composition of the protostellar disc andenvelope and, of course, the eventual influence on the formation of planets.

Surveys of clumps, cores, and condensations in Cygnus-X: SMA observations of SiO
38. (5−4)
Kai Yang, Keping Qiu, Xing Pan F The SiO emissions are usually used to trace high-velocity outflow shocks in star-

forming regions. However, several studies have found low-velocity and widespread SiO emissions not associated with
outflows in molecular clouds. We aim to detect and characterize the SiO emissions in massive dense cores (MDCs), andexplore the properties of the central sources of SiO emission. We present high-angular-resolution (∼1.500 ) observationsof the SiO (5−4) line made with the Submillimeter Array towards a sample of 48 MDCs in the Cygnus-X star-forming
complex. We studied the SiO emission structures, including their morphologies, kinematics, and energetics, andinvestigated their relationship with the evolution of the central sources. The SiO (5−4) emission is detected in 16
out of 48 MDCs. We identify 14 bipolar and 18 unipolar SiO (5−4) outflows associated with 29 dust condensations.
Most outflows (24 out of 32) are associated with excess Spitzer 4.5 µm emissions. We also find diffuse low-velocity(∆v ≤ 1.2 km s−1 ) SiO (5−4) emission closely surrounding the dust condensations in two MDCs, and suggest thatit may originate from decelerated outflow shocks or large-scale shocks from global cloud collapse. We find that the
SMA SiO (5−4) emission in MDCs is mostly associated with outflows. Probably due to the relatively high excitationof SiO (5−4) compared to SiO (2−1) and due to the spatial filtering effect, we do not detect large-scale low-velocity
SiO (5−4) emission, but detect more compact low-velocity emission in close proximity to the dust condensations. We
group the sources into different evolutionary stages based on the infrared emission, radio continuum emission, andgas temperature properties of the outflow central sources, and find that the 24 µm luminosity tends to increase withevolution.

15