The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 373 — 31 January 2024
Editor: João Alveswww.starformation.news

Cover image caption
NGC 1566, a face-on galaxy (distance about 6 Mpc), with the image divided diagonally: the observations from the James Webb
Space Telescope (near- and mid-infrared light) are located in the lower right, while those from the Hubble Space Telescope
visible and ultraviolet light) occupy the upper left.
Credits: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), Rupali Chandar (UToledo), Daniela Calzetti(UMass), PHANGS Team

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.

An analysis of the turbulence in the central region of the Orion Nebula (M42) – II.
2. homogeneity and power-spectrum analyses
G. A. Anorve-Zeferino F In this second communication we continue our analysis of the turbulence in the Huygens

Region of the Orion Nebula (M 42). We calculate the associated transverse structure functions up to order 8-th
and find that the higher-order transverse structure functions are almost proportional to the second-order transverse
structure function: we find that after proper normalisation, the higher-order transverse structure functions only differ
by very small deviations from the second-order transverse structure function in a sub-interval of the inertial range.
We demonstrate that this implies that the turbulence in the Huygens Region is quasi-log-homogeneous, or to a better
degree of approximation, binomially weighted log-homogeneous in the statistical sense, this implies that there is some
type of invariant statistical structure in the velocity field of the Huygens Region. We also obtain and analyse thepower-spectrum of the turbulent field and find that it displays a large tail that follows very approximately two powerlaws, one of the form E(k) ∝ k −2.7 for the initial side of the tail, and one of the form E(k) ∝ k −1 for the end of thetail. We find that the power-law with exponent β ∼ −2.7 corresponds to spatial scales of 0.0301–0.6450 pc. We findthat the exponent of the first power-law β ∼ −2.7 is related to the exponent α2 of the second-order structure functionin the inertial range. We interpret the second power-law with exponent β ∼ −1 as an indicator of viscous-dissipative
processes occurring at scales of δr = 1–5 pixels which correspond to spatial scales of 0.00043–0.00215 pc.

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3. Outflows Driven from a Magnetic Pseudodisk
Shantanu Basu, Mahmoud Sharkawi, Masahiro N. Machida F Outflows play a pivotal role in star formation as
one of its most visible markers and a means of transporting mass, momentum, and angular momentum from theinfalling gas into the surrounding molecular cloud. Their wide reach (at least ∼ 1000s of au) is a contrast to typicaldisk sizes (∼ 10 − 100 au). We employ high-resolution three-dimensional nested-grid nonideal magnetohydrodynamic(MHD) simulations to study outflow properties in the Class 0 phase. We find that no disk wind is driven from theextended centrifugal disk that has weak magnetic coupling. The low-velocity winds emerge instead from the infallingmagnetic pseudodisk. Much of the disk actually experiences an infall of matter rather than outflowing gas. Some ofthe pseudodisk wind (PD-wind) moves inward to regions above the disk and either falls onto the disk or proceeds
upward. The upward flow gives the impression of a disk wind above a certain height even if the gas is originally
emerging from the pseudodisk. The PD-wind has the strongest flow coming from a disk interaction zone that lies justoutside the disk and is an interface between the inwardly advected magnetic field of the pseudodisk and the outwardly
diffusing magnetic field of the disk. The low-velocity wind exhibits the features of a flow driven by the magnetic
pressure gradient force in some regions and those of a magnetocentrifugal wind in other regions. We interpret thestructure and dynamics of the outflow zone in terms of the basic physics of gravity, angular momentum, magnetic
fields, and nonideal MHD.

4.

Jets, Outflows, and Explosions in Massive Star Formation
John Bally F Multispectral studies of nearby, forming stars provide insights into all classes of accreting systems.
Objects which have magnetic fields, spin, and accrete produce jets and collimated outflows. Jets are seen in systems
ranging from brown dwarf stars to supermassive black holes. Outflow speeds are typically a few times the escapespeed from the launch region - 100s of km/s for young stars to nearly the speed of light for black-holes. Because many
young stellar objects (YSOs) are nearby, we can see outflow evolution and measure proper motions on times scales ofyears. Because the shocks in YSO outflows emit in atoms, ions, and molecules in addition to the continuum, many
physical properties such as temperatures, densities, and velocities can be measured. Momenta and kinetic energies
can be computed. YSO outflows are a major source of feedback in the self-regulation of star formation. The lessons
learned can be applied to much more distant and energetic cosmic sources such as AGN and galactic nuclear superwinds - systems in which evolution occurs on time-scales of hundreds to millions of years. Some dense star-forming
regions produce powerful explosions. The nearest massive star-forming region, Orion OMC1, powered a ∼ 1048 erg
explosion about 550 years ago (that is when the light from the event would have reached the Solar System). The
OMC1 explosion was likely powered by an N-body interaction which resulted in the formation of a compact, AU-scalebinary or resulted in a protostellar merger. The binary or merger remnant, the ∼15 Msun object known as radiosource I (Src I) was ejected from the core with a speed of ∼10 km/s along with two other stars. The ∼10 Msun BN
object was ejected with ∼30 km/s and a ∼3 Msun star was ejected with ∼55 km/s .

VLTI/GRAVITY Provides Evidence the Young, Substellar Companion HD 136164 Ab
5. formed like a "Failed Star"
William O. Balmer, GRAVITY Collaboration F Young, low-mass Brown Dwarfs orbiting early-type stars, withlow mass ratios (q . 0.01), appear intrinsically rare and present a formation dilemma: could a handful of these objects
be the highest mass outcomes of “planetary" formation channels (bottom up within a protoplanetary disk), or are
they more representative of the lowest mass “failed binaries" (formed via disk fragmentation, or core fragmentation)?
Additionally, their orbits can yield model-independent dynamical masses, and when paired with wide wavelength
coverage and accurate system age estimates, can constrain evolutionary models in a regime where the models have awide dispersion depending on initial conditions. We present new interferometric observations of the 16 Myr substellar
companion HD 136164 Ab (HIP 75056 Ab) with VLTI/GRAVITY and an updated orbit fit including proper motion
measurements from the Hipparcos-Gaia Catalogue of Accelerations. We estimate a dynamical mass of 35 ± 10 MJ(q ∼ 0.02), making HD 136164 Ab the youngest substellar companion with a dynamical mass estimate. The new
mass and newly constrained orbital eccentricity (e = 0.44 ± 0.03) and separation (22.5 ± 1 au) could indicate thatthe companion formed via the low-mass tail of the Initial Mass Function. Our atmospheric fit to the SPHINX Mdwarf model grid suggests a sub-solar C/O ratio of 0.45, and 3× solar metallicity, which could indicate formationin the circumstellar disk via disk fragmentation. Either way, the revised mass estimate likely excludes “bottom-up"
formation via core accretion in the circumstellar disk. HD 136164 Ab joins a select group of young substellar objects
with dynamical mass estimates; epoch astrometry from future Gaia data releases will constrain the dynamical mass3

of this crucial object further.

The GRAVITY young stellar object survey: XI. Imaging the hot gas emission around6. the Herbig Ae star HD 58647
Y. -I. Bouarour, GRAVITY Collaboration F We aim to investigate the origin of the HI Brγ emission in young stars

by using GRAVITY to image the innermost region of circumstellar disks, where important physical processes such as
accretion and winds occur. With high spectral and angular resolution, we focus on studying the continuum and the HI
Brγ-emitting area of the Herbig star HD58647. Using VLTI-GRAVITY, we conducted observations of HD58647 withboth high spectral and high angular resolution. Thanks to the extensive uv coverage, we were able to obtain detailed
images of the circumstellar environment at a sub-au scale, specifically capturing the continuum and the Brγ-emitting
region. Through the analysis of velocity-dispersed images and photocentre shifts, we were able to investigate thekinematics of the HI Brγ-emitting region. The recovered continuum images show extended emission where the diskmajor axis is oriented along a position angle of 14 degrees. The size of the continuum emission at 5-sigma levels is ∼1.5 times more extended than the sizes reported from geometrical fitting (3.69 mas ± 0.02 mas). This result supports
the existence of dust particles close to the stellar surface, screened from the stellar radiation by an optically thickgaseous disk. Moreover, for the first time with GRAVITY, the hot gas component of HD58647 traced by the Brγ ,has
been imaged. This allowed us to constrain the size of the Brγ-emitting region and study the kinematics of the hotgas; we find its velocity field to be roughly consistent with gas that obeys Keplerian motion. The velocity-dispersed
images show that the size of the hot gas emission is from a more compact region than the continuum (2.3 mas ± 0.2mas). Finally, the line phases show that the emission is not entirely consistent with Keplerian rotation, hinting at amore complex structure in the hot gaseous disk.

growth and evolution in protoplanetary disks
7. DustTilman 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.

8. Dynamics of the Beta Pictoris planetary system and its falling evaporating bodies

H. Beust, J. Milli, A. Morbidelli, S. Lacour, A. -M. Lagrange, G. Chauvin, M. Bonnefoy, J. Wang F For decades,

the spectral variations of Beta Pictoris have been modelled as the result of the evaporation of exocomets close to thestar, termed falling evaporating bodies (FEBs). Resonant perturbations by a giant planet have been proposed to
explain the dynamical origin of these stargrazers. The disk is now known to harbour two giant planets, Beta Pic b
and c, orbiting the star at 9.9 au and 2.7 au. While the former almost matches the planet formerly suspected, thediscovery of the latter complicates the picture. We first question the stability of the two-planet system. Then we
investigate the dynamics of a disk of planetesimals orbiting the star with both planets to check the validity of the
FEB generation mechanism. Symplectic N-body simulations are used to determine which regions of the planetesimal
disk are dynamically stable. Then we focus on regions where disk particles are able to reach high eccentricities thanks
to resonant mechanisms. The first result is that the system is dynamically stable. Both planets may temporarily fallin 7:1 mean motion resonance (MMR). Then, simulations reveal that the whole region extending between 1.5 au and
25 au is unstable to planetary perturbations. However, a disk below 1.5 au survives, which appears to constitute an4active source of FEBs via high-order MMRs with Beta Pic c. Beta Pic b acts as a distant perturber that helps sustain
the whole process. These simulations rule out the preceding FEB generation mechanism model, which placed their
origin at around 4-5 au. Conversely, FEBs are likely to originate from a region much further in and related to MMRs
with Beta Pic c. That mechanism also appears to last longer, as new planetesimals are able to continuously enter
the MMRs and evolve towards the FEB state. Subsequently, the physical nature of the FEBs may differ from that
previously thought, and presumably may not be icy.

9. Surveying the Giant HII Regions of the Milky Way with SOFIA: VI. NGC 3603

James M. De Buizer, Wanggi Lim, Nicole Karnath, James T. Radomski F We present our sixth set of resultsfrom our mid-infrared imaging survey of Milky Way Giant HII regions with our detailed analysis of NGC 3603, themost luminous GHII region in the Galaxy. We used imaging data from the FORCAST instrument on the Stratospheric
Observatory For Infrared Astronomy (SOFIA) at 20 and 37 microns which mapped the central 8.5’x8.5’ infraredemitting area of NGC 3603 at a spatial resolution of < 3". Utilizing these SOFIA data in conjunction with multiwavelength observations from the near-infrared to radio, including Spitzer-IRAC and Herschel-PACS archival data, weinvestigate the physical nature of individual infrared sources and sub-components within NGC 3603. For individualcompact sources we used the multi-wavelength photometry data to construct spectral energy distributions (SEDs) and
fit them with massive young stellar object (MYSO) SED models, and find 14 sources that are likely to be MYSOs. We
also detect dust emission from the 3 massive proplyd candidates, as well as from the disk and outflow of the evolved
blue supergiant, Sher 25. Utilizing multi-wavelength data, we derived luminosity-to-mass ratio and virial parameters
for the star-forming clumps within NGC 3603, estimating their relative ages and finding that NGC 3603 is an older
GHII region overall, compared to our previously studied GHII regions. We discuss how NGC 3603, which we categorize
as a ’cavity-type’ GHII region, exhibits a more modest number of MYSOs and molecular clumps when compared tothe ’distributed-type’ GHII regions that share similar Lyman continuum photon rates.

10. Ammonia Observations of Planck Cold Cores
Dilda Berdikhan., Jarken Esimbek., Christian Henkel., Jianjun Zhou., Xindi Tang., Tie Liu., Gang Wu., Dalei
Li., Yuxin He., Toktarkhan Komesh., Kadirya Tursun., Dongdong Zhou., Ernar Imanaly., Qaynar Jandaolet

F Single-pointing observations of NH3 (1,1) and (2,2) were conducted towards 672 Planck Early Release Cold Cores(ECCs) using the Nanshan 26-m radio telescope. Out of these sources, a detection rate of 37% (249 cores) was achieved,with NH3 (1,1) hyperfine structure detected in 187 and NH3 (2,2) emission lines detected in 76 cores. The detection rateof NH3 is positively correlated with the continuum emission fluxes at a frequency of 857 GHz. Among the observed
672 cores, 22% have associated stellar and IR objects within the beam size (about 2 arcmin). This suggests that mostof the cores in our sample may be starless. The kinetic temperatures of the cores range from 8.9 to 20.7 K, with anaverage of 12.3 K, indicating a coupling between gas and dust temperatures. The ammonia column densities range
from 0.36 to 6.07×1015 cm−2 , with a median value of 2.04×1015 cm−2 . The fractional abundances of ammonia range
from 0.3 to 9.7×10−7 , with an average of 2.7 ×10−7 , which is one order of magnitude larger than that of Massive
Star-Forming (MSF) regions and Infrared Dark Clouds (IRDCs). The correlation between thermal and non-thermalvelocity dispersion of the NH3 (1,1) inversion transition indicates the dominance of supersonic non-thermal motionsin the dense gas traced by NH3 , and the relationship between these two parameters in Planck cold cores is weaker,
with lower values observed for both parameters relative to other samples under our examination. The cumulative
distribution shapes of line widths in the Planck cold cores closely resemble those of the dense cores found in regions of
Cepheus, and Orion L1630 and L1641, with higher values compared to Ophiuchus. A comparison of NH3 line-center
velocities with those of 13 CO and C18 O shows small differences (0.13 and 0.12 km s−1 ), suggesting quiescence on
small scales.

11. Formation of the Methyl Cation by Photochemistry in a Protoplanetary Disk

Olivier Berné et al. F Forty years ago it was proposed that gas phase organic chemistry in the interstellar medium

was initiated by the methyl cation CH3+, but hitherto it has not been observed outside the Solar System. Alternativeroutes involving processes on grain surfaces have been invoked. Here we report JWST observations of CH3+ in a
protoplanetary disk in the Orion star forming region. We find that gas-phase organic chemistry is activated by UV
irradiation.

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Jupiter Formation in Dense Star Clusters
12. Hot
Leonard Benkendorff, Francesco Flammini Dotti, Katja Stock, Maxwell Xu Cai, Rainer Spurzem F Hot Jupiters(HJ) are defined as Jupiter-mass exoplanets orbiting around their host star with an orbital period < 10 days. It is
assumed that HJ do not form in-situ but ex-situ. Recent discoveries show that star clusters contribute to the formationof HJ. We present direct N -body simulations of planetary systems in star clusters and analyze the formation of HJ inthem. We combine two direct N -body codes: NBODY6++GPU for the dynamics of dense star clusters with 32 000
and 64 000 stellar members and LonelyPlanets used to follow 200 identical planetary systems around solar mass stars
in those star clusters. We use different sets with 3, 4, or 5 planets and with the innermost planet at a semi-major axisof 5 au or 1 au and follow them for 100 Myr in our simulations. The results indicate that HJs are generated with highefficiency in dense star clusters if the innermost planet is already close to the host star at a semi-major axis of 1 au.
If the innermost planet is initially beyond a semi-major axis of 5 au, the probability of a potential HJ ranges between
1.5 − 4.5 percent. Very dense stellar neighborhoods tend to eject planets rather than forming HJs. A correlation
between HJ formation and angular momentum deficit (AMD) is not witnessed. Young Hot Jupiters (tage < 100 Myrs)
have only been found, in our simulations, in planetary systems with the innermost planet at a semi-major axis of 1
au.

The GRAVITY young stellar object survey XII. The hot gas disk component in Herbig
13. Ae/Be stars
R. Garcia, GRAVITY Collaboration F The region of protoplanetary disks closest to a star (within 1-2 au) is shapedby a number of different processes, from accretion of the disk material onto the central star to ejection in the formof winds and jets. Optical and near-IR emission lines are potentially good tracers of inner disk processes if very highspatial and/or spectral resolution are achieved. In this paper, we exploit the capabilities of the VLTI-GRAVITY nearIR interferometer to determine the location and kinematics of the hydrogen emission line Bracket gamma. We present
VLTI-GRAVITY observations of the Bracket gamma line for a sample of 26 stars of intermediate mass (HAEBE), thelargest sample so far analysed with near-IR interferometry. The Bracket gamma line was detected in 17 objects. The
emission is very compact (in most cases only marginally resolved), with a size of 10-30R* (1-5 mas). About half ofthe total flux comes from even smaller regions, which are unresolved in our data. For eight objects, it was possible
to determine the position angle (PA) of the line-emitting region, which is generally in agreement with that of theinner-dusty disk emitting the K-band continuum. The position-velocity pattern of the Bracket gamma line-emitting
region of the sampled objects is roughly consistent with Keplerian rotation. The exception is HD 45677, which shows
more extended emission and more complex kinematics. The most likely scenario for the Bracket gamma origin isthat the emission comes from an MHD wind launched very close to the central star, in a region well within the dust
sublimation radius. An origin in the bound gas layer at the disk surface cannot be ruled out, while accreting matterprovides only a minor fraction of the total flux. These results show the potential of near-IR spectro-interferometry to
study line emission in young stellar objects.

14. Young, wild and free: the early expansion of star clusters

Alessandro Della Croce, Emanuele Dalessandro, Alexander R. Livernois, Enrico Vesperini F Early expansion

plays a fundamental role in the dynamical evolution of young star clusters. However, until very recently most of ourunderstanding of cluster expansion was based only on indirect evidence or on statistically limited samples of clusters.
Here we present a comprehensive kinematic analysis of virtually all known young (t < 300 Myr) Galactic clusters
based on the improved astrometric quality of the Gaia DR3 data. Such a large sample provides the unprecedented
opportunity to robustly constrain the fraction of clusters and the timescale during which expansion has a prominent
impact on the overall kinematics. We find that a remarkable fraction (up to 80%) of clusters younger than ∼ 30
Myr is currently experiencing significant expansion, whereas older systems are mostly compatible with equilibrium
configurations. We observe a trend where the expansion speed increases with the clustercentric distance, suggestingthat clusters undergoing expansion will likely lose a fraction of their present-day mass. Also, most young expanding
clusters show large sizes, possibly due to the expansion itself. A comparison with a set of N-body simulations ofyoung star clusters shows that the observed expansion pattern is in general qualitative agreement with that found forsystems undergoing violent relaxation and evolving toward a final virial equilibrium state. However, we also note that
additional processes likely associated with residual gas expulsion and mass loss due to stellar evolution are also likely
to play a key role in driving the observed expansion.

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Dynamics in Star-forming Cores (DiSCo): Project Overview and the First Look toward
15. 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.

JWST/NIRCam Imaging of Young Stellar Objects. II. Deep Constraints on Giant
16. Planets and a Planet Candidate Outside of the Spiral Disk Around SAO 206462
Gabriele Cugno, Jarron Leisenring, Kevin R. Wagner, Camryn Mullin, Roubing Dong, Thomas Greene, Doug
Johnstone, Michael R. Meyer, Schuyler G. Wolff, Charles Beichman, Martha Boyer, Scott Horner, Klaus
Hodapp, Doug Kelly, Don McCarthy, Thomas Roellig, George Rieke, Marcia Rieke, John Stansberry, Erick
Young F We present JWST/NIRCam F187N, F200W, F405N and F410M direct imaging data of the disk surrounding

SAO 206462. Previous images show a very structured disk, with a pair of spiral arms thought to be launched by one ormore external perturbers. The spiral features are visible in three of the four filters, with the non-detection in F410M
due to the large detector saturation radius. We detect with a signal-to-noise ratio of 4.4 a companion candidate (CC1)that, if on a coplanar circular orbit, would orbit SAO 206462 at a separation of ∼ 300 au, 2.25σ away from the predicted
separation for the driver of the eastern spiral. According to the BEX models, CC1 has a mass of MCC1 = 0.8 ± 0.3 MJ .
No other companion candidates were detected. At the location predicted by simulations of both spirals generated
by a single massive companion, the NIRCam data exclude objects more massive than ∼ 2.2 MJ assuming the BEX
evolutionary models. In terms of temperatures, the data are sensitive to objects with Teff ∼ 650 − 850 K, whenassuming planets emit like blackbodies (Rp between 1 and 3RJ ). From these results, we conclude that if the spirals
are driven by gas giants, these must be either cold or embedded in circumplanetary material. In addition, the NIRCamdata provide tight constraints on ongoing accretion processes. In the low extinction scenario we are sensitive to massaccretion rates of the order Ṁ ∼ 10−9 MJ yr−1 . Thanks to the longer wavelengths used to search for emission lines,
we reach unprecedented sensitivities to processes with Ṁ ∼ 10−7 MJ yr−1 even towards highly extincted environments(AV ≈ 50 mag).

of Dusty Rings in Protoplanetary Discs
17. Stability
Kevin Chan, Sijme-Jan Paardekooper F Dust rings in protoplanetary discs are often observed in thermal dust
emission and could be favourable environments for planet formation. While dust rings readily form in gas pressure
maxima, their long-term stability is key to both their observability and potential to assist in planet formation. We
investigate the stability of the dust ring generated by interactions of a protoplanetary disc with a Neptune sized planetand consider its possible long term evolution using the FARGO3D Multifluid code. We look at the onset of the Rossby
Wave Instability (RWI) and compare how the addition of dust in a disc can alter the stability of the gas phase. We findthat with the addition of dust, the rings generated by planet disc interactions are more prone to RWI and can cause
the gas phase to become unstable. The instability is shown to occur more easily for higher Stokes number dust, as it
accumulates into a more narrow ring which triggers the RWI, while the initial dust fraction plays a more minor role inthe stability properties. We show that the dusty RWI generates vortices that collect dust in their cores, which could
be sites for further planetesimal formation. We conclude that the addition of dust can cause a ring in a protoplanetary
disc to become more prone to instability leading to a different long term evolution compared to gas only simulationsof the RWI.

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The GRAVITY young stellar object survey XIII. Tracing the time-variable asymmetric
18. disk structure in the inner AU of the Herbig star HD98922
V. Ganci, GRAVITY Collaboration F Temporal variability in the photometric and spectroscopic properties ofprotoplanetary disks is common in YSO. However, evidence pointing toward changes in their morphology over shorttimescales has only been found for a few sources, mainly due to a lack of high cadence observations at mas resolution.
We combine GRAVITY multi-epoch observations of HD98922 at mas resolution with PIONIER archival data coveringa total time span of 11 years. We interpret the interferometric visibilities and spectral energy distribution withgeometrical models and through radiative transfer techniques. We investigated high-spectral-resolution quantities toobtain information on the properties of the HI BrG-line-emitting region. The observations are best fitted by a modelof a crescent-like asymmetric dust feature located at 1 au and accounting for 70% of the NIR emission. The feature hasan almost constant magnitude and orbits the central star with a possible sub-Keplerian period of 12 months, althougha 9 month period is another, albeit less probable, solution. The radiative transfer models show that the emission
originates from a small amount of carbon-rich (25%) silicates, or quantum-heated particles located in a low-density
region. Among different possible scenarios, we favor hydrodynamical instabilities in the inner disk that can create alarge vortex. The high spectral resolution differential phases in the BrG-line show that the hot-gas component is offset
from the star and in some cases is located between the star and the crescent feature. The scale of the emission does
not favor magnetospheric accretion as a driving mechanism. The scenario of an asymmetric disk wind or a massive
accreting substellar or planetary companion is discussed. With this unique observational data set for HD98922, wereveal morphological variability in the innermost 2 au of its disk region.

Deciphering the Hidden Structures of HH 216 and Pillar IV in M16: Results from
19. JWST and HST
L. K. Dewangan, O. R. Jadhav, A. K. Maity, N. K. Bhadari, Saurabh Sharma, M. Padovani, T. Baug, Y. D.
Mayya, Rakesh Pandey F To probe the star formation process, we present an observational investigation of the Pillar

IV and an ionized knot HH 216 in the Eagle Nebula (M16). Pillar IV is known to host a Class I protostar that drives
a bipolar outflow. The outflow has produced the bow shock, HH 216, which is associated with the red-shifted outflow
lobe. The James Webb Space Telescope’s near- and mid-infrared images (resolution ∼0.07 arcsec - 0.7 arcsec) reveal
the protostar as a single, isolated object (below 1000 AU). The outer boundary of Pillar IV is depicted with the 3.3 µm
Polycyclic aromatic hydrocarbon (PAH) emission. HH 216 is traced with the 4.05 µm Brα and the radio continuum
emission, however it is undetected with 4.693 µm H2 emission. HH 216 seems to be associated with both thermal andnon-thermal radio emissions. High-resolution images reveal entangled ionized structures (below 3000 AU) of HH 216,
which appear to be located toward termination shocks. New knots in 4.693 µm H2 emission are detected, and aremainly found on Pillar IV’s northern side. This particular result supports the previously proposed episodic accretionin the powering source of HH 216. One part of the ionized jet (extent ∼0.16 pc) is discovered on the southern side ofthe driving source. Using the 12 CO(J = 1-0), 12 CO(J = 3-2), and 13 CO(J = 1-0) emission, observational signposts ofCloud-Cloud Collision (or interacting clouds) toward Pillar IV are investigated. Overall, our results suggest that theinteraction of molecular cloud components around 23 and 26 km s−1 might have influenced star formation activity in
Pillar IV.

Disentangling CO Chemistry in a Protoplanetary Disk Using Explanatory Machine
20. Learning Techniques

Amina Diop, Ilse Cleeves, Dana Anderson, Jamila Pegues, Adele Plunkett F Molecular abundances in protoplanetary disks are highly sensitive to the local physical conditions, including gas temperature, gas density, radiation field,
and dust properties. Often multiple factors are intertwined, impacting the abundances of both simple and complex
species. We present a new approach to understanding these chemical and physical interdependencies using machinelearning. Specifically we explore the case of CO modeled under the conditions of a generic disk and build an explanatory regression model to study the dependence of CO spatial density on the gas density, gas temperature, cosmic ray
ionization rate, X-ray ionization rate, and UV flux. Our findings indicate that combinations of parameters play asurprisingly powerful role in regulating CO compared to any singular physical parameter. Moreover, in general, we
find the conditions in the disk are destructive toward CO. CO depletion is further enhanced in an increased cosmic
ray environment and in disks with higher initial C/O ratios. These dependencies uncovered by our new approach
are consistent with previous studies, which are more modeling intensive and computationally expensive. Our work
thus shows that machine learning can be a powerful tool not only for creating efficient predictive models, but also for8enabling a deeper understanding of complex chemical processes.

PDRs4All. V. Modelling the dust evolution across the illuminated edge of the Orion
21. BarM. Elyajouri, N. Ysard, A. Abergel, E. Habart, L. Verstraete, A. Jones, M. Juvela, T. Schirmer, R. Meshaka, E.
Dartois, J. Lebourlot, G. Rouille, T. Onaka, E. Peeters, O. Berne, F. Alarcon, J. Bernard-Salas, M. Buragohain,
J. Cami, A. Canin, R. Chown, K. Demyk, K. Gordon, O. Kannavou, M. Kirsanova, S. Madden, R. Paladini, Y.
Pendleton, F. Salama, I. Schroetter, A. Sidhu, M. Rollig, B. Trahin, D. Van De Putte F We study the emissionof dust grains within the Orion Bar - a well-known, highly far-UV (FUV)-irradiated PDR. The Orion Bar because of
its edge-on geometry provides an exceptional benchmark for characterizing dust evolution and the associated driving
processes under varying physical conditions. Our goal is to constrain the local properties of dust by comparing its
emission to models. Taking advantage of the recent JWST PDRs4All data, we follow the dust emission as traced by
JWST NIRCam (at 3.35 and 4.8 micron) and MIRI (at 7.7, 11.3, 15.0, and 25.5 micron), along with NIRSpec and MRS
spectroscopic observations. First, we constrain the minimum size and hydrogen content of carbon nano-grains from acomparison between the observed dust emission spectra and the predictions of the THEMIS dust model coupled to thenumerical code DustEM. Using this dust model, we then perform 3D radiative transfer simulations of dust emission
with the SOC code and compare to data obtained along well chosen profiles across the Orion Bar. The JWST data
allows us, for the first time, to spatially resolve the steep variation of dust emission at the illuminated edge of theOrion Bar PDR. By considering a dust model with carbonaceous nano-grains and submicronic coated silicate grains,
we derive unprecedented constraints on the properties of across the Orion Bar. To explain the observed emission
profiles with our simulations, we find that the nano-grains must be strongly depleted with an abundance (relative tothe gas) 15 times less than in the diffuse ISM. The NIRSpec and MRS spectroscopic observations reveal variationsin the hydrogenation of the carbon nano-grains. The lowest hydrogenation levels are found in the vicinity of theilluminating stars suggesting photo-processing while more hydrogenated nano-grains are found in the cold and dense
molecular region, potentially indicative of larger grains.

Vertical shear instability in two-moment radiation-hydrodynamical simulations of irra22. diated protoplanetary disks I. Angular momentum transport and turbulent heating
Julio David Melon Fuksman, Mario Flock, Hubert Klahr F We studied the linear and nonlinear evolution of

the Vertical Shear Instability (VSI) in axisymmetric models of protoplanetary disks, focusing on the transport ofangular momentum, the produced temperature perturbations, and the applicability of local stability conditions. We
modeled the gas-dust mixture via high-resolution two-moment (M1) radiation-hydrodynamical simulations including
stellar irradiation with frequency-dependent opacities. We found that, given sufficient depletion of small grains (witha dust-to-gas mass ratio of 10% of our nominal value of 10−3 for < 0.25 µm grains), the VSI can operate in surface disk
layers while being inactive close to the midplane, resulting in a suppression of the VSI body modes. The VSI reduces
the initial vertical shear in bands of approximately uniform specific angular momentum, whose formation is likely
favored by the enforced axisymmetry. Similarities with Reynolds stresses and angular momentum distributions in 3D
simulations suggest that the VSI-induced angular momentum mixing in the radial direction may be predominantly
axisymmetric. The stability regions in our models are well explained by local stability criteria, while the employmentof global criteria is still justifiable up to a few scale heights above the midplane, at least as long as VSI modes areradially optically thin. Turbulent heating produces only marginal temperature increases of at most 0.1% and 0.01%
in the nominal and dust-depleted models, respectively, peaking at a few (approximately three) scale heights above themidplane. We conclude that it is unlikely that the VSI can, in general, lead to any significant temperature increasesince that would either require it to efficiently operate in largely optically thick disk regions or to produce larger levelsof turbulence than predicted by models of passive irradiated disks.

The Kinematic and Dynamic Properties of HBC 494’s Wide-Angle Outflows
23. Austen Fourkas, Dary Ruiz-Rodriguez, Lee G. Mundy, Jonathan P. Williams F We present Atacama Large
Millimeter/sub-millimeter Array (ALMA) Cycle-5 observations of HBC 494, as well as calculations of the kinematicand dynamic variables which represent the object’s wide-angle bipolar outflows. HBC 494 is a binary FU Orionis typeobject located in the Orion A molecular cloud. We take advantage of combining the ALMA main array, Atacama
Compact Array (ACA), and Total Power (TP) array in order to map HBC 494’s outflows and thus, estimate their

9kinematic parameters with higher accuracy in comparison to prior publications. We use 12 CO, 13 CO, C18 O and SO
observations to describe the object’s outflows, envelope, and disc, as well as estimate the mass, momentum, and kinetic
energy of the outflows. After correcting for optical opacity near systemic velocities, we estimate a mass of 3.0 × 10−2
M for the southern outflow and 2.8 × 10−2 M for the northern outflow. We report the first detection of a secondary
outflow cavity located approximately 15" north of the central binary system, which could be a remnant of a previous
large-scale accretion outburst. Furthermore, we find CO spatial features in HBC 494’s outflows corresponding toposition angles of ∼ 35◦ and ∼ 145◦ . This suggests that HBC 494’s outflows are most likely a composite of overlapping
outflows from two different sources, i.e., HBC 494a and HBC 494b, the two objects in the binary system.

JOYS: MIRI/MRS spectroscopy of gas-phase molecules from the high-mass star-forming
24. region IRAS 23385+6053
L. Francis, M. L. van Gelder, E. F. van Dishoeck, C. Gieser, H. Beuther, L. Tychoniec, G. Perotti, A. Caratti oGaratti, P. J. Kavanagh, T. Ray, P. Klaassen, K. Justtanont, H. Linnartz, W. R. M. Rocha, K. Slavicinska, M.
Güdel, T. Henning, P. O. Lagage, G. Östlin F Space-based mid-IR spectroscopy provides tracers of warm gas instar-forming regions that are inaccessible from the ground. Past mid-IR spectra of bright high-mass protostars in the
hot-core phase typically showed strong absorption features from molecules such as CO2 , C2 H2 , and HCN. However,
little is known about their fainter counterparts at earlier stages. We thus aim to characterize the gas-phase molecularfeatures in JWST MIRI/MRS observations of the young high-mass star-forming region IRAS 23385+6053. Spectra
were extracted from two mid-IR sources and three H2 bright outflow knots in the MIRI/MRS field of view. Rich
molecular spectra with emission from CO, H2 , HD, H2 O, C2 H2 , HCN, CO2 , and OH are detected towards the two
mid-IR sources. However, only CO and OH are seen towards the brightest H2 knots, suggesting that the majority ofthe observed species are associated with disks or hot core regions rather than outflows. Simple Local thermodynamic
equilibrium (LTE) slab models were used to fit the observed molecular features. The LTE model fits to 12 CO2 , C2 H2 ,and HCN emission suggest warm 120−200 K emission arising from a disk surface around one or both protostars. Weak
∼ 500 K H2 O emission at ∼ 6-7 µm is detected towards one mid-IR source, whereas 250 − 1050 K H2 O absorption
is found in the other. The H2 O absorption may occur in the disk atmosphere due to strong accretion-heating of the
midplane, or in a disk wind viewed at an ideal angle for absorption. CO emission may originate in the hot inner diskor outflow shocks. OH emission is likely excited in a non-LTE manner through water photodissociation or chemical
formation. The observations are consistent with disks having already formed in the young IRAS 23385+6053 system,
but further observations are needed to disentangle the effects of geometry and evolution.

25. On the evolution of the observed Mass-to-Length relationship for star-forming filaments

Jiancheng Feng, Rowan J. Smith, Alvaro Hacar, Susan E. Clark, Daniel Seifried F The interstellar medium isthreaded by a hierarchy of filaments from large scales ( 100 pc) to small scales ( 0.1pc). The masses and lengths of thesenested structures may reveal important constraints for cloud formation and evolution, but it is difficult to investigate
from an evolutionary perspective using single observations. In this work, we extract simulated molecular clouds fromthe Cloud Factory galactic-scale ISM suite in combination with 3D Monte Carlo radiative transfer code POLARIS toinvestigate how filamentary structure evolves over time. We produce synthetic dust continuum observations in three
regions with a series of snapshots and use the Filfinder algorithm to identify filaments in the dust derived column
density maps. When the synthetic filaments mass and length are plotted on an M-L plot, we see a scaling relationof L ∝ M 0.45 similar to that seen in observations, and find that the filaments are thermally supercritical. Projection
effects systematically affect the masses and lengths measured for the filaments, and are particularly severe in crowded
regions. In the filament Mass-Length (M-L) diagram we identify three main evolutionary mechanisms: accretion,
segmentation, and dispersal. In particular we find that the filaments typically evolve from smaller to larger masses
in the observational M-L plane, indicating the dominant role of accretion in filament evolution. Moreover, we find apotential correlation between line mass and filament growth rate. Once filaments are actively star forming they thensegment into smaller sections, or are dispersed by internal or external forces.

1026. The magnetic field in colliding filaments G202.3+2.5
Qi-Lao Gu, Tie Liu, Pak Shing Li, Zhi-Qiang Shen, Xunchuan Liu, Junhao Liu, Xing Lu, Julien Montillaud,
Sihan Jiao, Mika Juvela, Mark G. Rawlings, Qizhou Zhang, Patrick Koch, Isabelle Ristorcelli, Jean-Sébastien
Carriere, David Eden, Zhiyuan Ren, Ken’ichi Tatematsu, Naomi Hirano, Qiu-yi Luo, Xiaofeng Mai, Namitha
Issac F We observe the magnetic field morphology towards a nearby star-forming filamentary cloud, G202.3+2.5,

by the JCMT/POL-2 850 µm thermal dust polarization observation with an angular resolution of 14.4" ( 0.053 pc).
The average magnetic field orientation is found to be perpendicular to the filaments while showing different behaviors
in the four subregions, suggesting various effects from filaments’ collision in these subregions. With the kinematics
obtained by N2H+ observation by IRAM, we estimate the plane-of-sky (POS) magnetic field strength by two methods,
the classical Davis-Chandrasekhar-Fermi (DCF) method and the angular dispersion function (ADF) method, Bpos,dcf
and Bpos,adf are 90 µG and 53 µG. We study the relative importance between the gravity (G), magnetic field (B)and turbulence (T) in the four subregions, find G > T > B, G >= T > B, G T > B and T > G > B in the northtail, west trunk, south root and east wing, respectively. In addition, we investigate the projection effect on the DCF
and ADF methods based on a similar simulation case and find the 3D magnetic field strength may be underestimatedby a factor of 3 if applying the widely-used statistical Bpos -to-B3D factor when using DCF or ADF method, which
may further underestimate/overestimate related parameters.

Photometric Variability of Low Mass Stars and Brown Dwarfs in IC 348 and Taurus
27. Star-Forming Regions
Samrat Ghosh, Soumen Mondal, Santosh Joshi, Sneh Lata, Rajib Kumbhakar F Low-mass stars belonging to the

M spectral type are the most numerous stars in our Galaxy, amounting to about two-thirds in number, and are foundat the bottom of the main sequence in the H-R diagram. star-forming regions help to understand the census of PMS
stars, their formation process, and the interaction of expanding H II regions harboring massive stars with their natal
molecular clouds. Photometric studies of low-mass stars, including brown dwarfs (BDs), provide several important
evolutions of their atmosphere, magnetic flares and chromospheric activity. This paper highlights a few interesting
results from our optical I-band observations of 2MASS J03435638+3209591 in the young star-forming IC 348 region
and three BDs in Taurus star-forming regions using ground-based telescopes as well as a space-based telescope. We
estimated the fast periodicities in the range of 1.5 to 3 hours in Taurus BDs. Furthermore, using the long-term
photometry from the Transiting Exoplanet Survey Satellite (TESS), we have conducted a time-resolved variability
analysis of CFHT-BD-Tau 4. The periodogram analysis of TESS data reveals an orbital period of ∼ 3 days. We found
two flare events in TESS sector 43 data for this BD and estimated the flared energies as 4.59 × 1035 erg and 2.64 × 1036
erg, which sit in the superflare range.

TIPSY: Trajectory of Infalling Particles in Streamers around Young stars. Dynamical
28. analysis of the streamers around S CrA and HL Tau
Aashish Gupta, Anna Miotello, Jonathan P. Williams, Til Birnstiel, Michael Kuffmeier, Hsi-Wei Yen F Context.

Elongated trails of infalling gas, often referred to as "streamers," have recently been observed around young stellar
objects (YSOs) at different evolutionary stages. This asymmetric infall of material can significantly alter star andplanet formation processes, especially in the more evolved YSOs. Aims. In order to ascertain the infalling nature ofobserved streamer-like structures and then systematically characterize their dynamics, we developed the code TIPSY(Trajectory of Infalling Particles in Streamers around Young stars). Methods. Using TIPSY, the streamer molecularline emission is first isolated from the disk emission. Then the streamer emission, which is effectively a point cloudin three-dimensional (3D) position-position-velocity space, is simplified to a curve-like representation. The observed
streamer curve is then compared to the theoretical trajectories of infalling material. The best-fit trajectories are used
to constrain streamer features, such as the specific energy, the specific angular momenta, the infall timescale, andthe 3D morphology. Results. We used TIPSY to fit molecular-line ALMA observations of streamers around a Class
II binary system, S CrA, and a Class I/II protostar, HL Tau. Our results indicate that both of the streamers are
consistent with infalling motion. TIPSY results and mass estimates suggest that S CrA and HL Tau are accreting
material at a rate of & 27 Mjupiter Myr−1 and & 5 Mjupiter Myr−1 , respectively, which can significantly increase
the mass budget available to form planets. Conclusions. TIPSY can be used to assess whether the morphology andkinematics of observed streamers are consistent with infalling motion and to characterize their dynamics, which is
crucial for quantifying their impact on the protostellar systems.

1129. Mapping dust in the giant molecular cloud Orion A

Amery Gration, John Magorrian F The Sun is located close to the Galactic mid-plane, meaning that we observe

the Galaxy through significant quantities of dust. Moreover, the vast majority of the Galaxy’s stars also lie in thedisc, meaning that dust has an enormous impact on the massive astrometric, photometric and spectroscopic surveysof the Galaxy that are currently underway. To exploit the data from these surveys we require good three-dimensional
maps of the Galaxy’s dust. We present a new method for making such maps in which we form the best linear unbiased
predictor of the extinction at an arbitrary point based on the extinctions for a set of observed stars. This method
allows us to avoid the artificial inhomogeneities (so-called ’fingers of God’) and resolution limits that are characteristicof many published dust maps. Moreover, it requires minimal assumptions about the statistical properties of theinterstellar medium. In fact, we require only a model of the first and second moments of the dust density field. The
method is suitable for use with directly measured extinctions, such as those provided by the Rayleigh-Jeans colour
excess method, and inferred extinctions, such as those provided by hierarchical Bayesian models like StarHorse. We
test our method by mapping dust in the region of the giant molecular cloud Orion A. Our results indicate a foregrounddust cloud at a distance of 350 pc, which has been identified in work by another author.

Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from
30. the VVV survey
Zhen Guo, P. W. Lucas, R. Kurtev, J. Borissova, C. Contreras Peña, S. N. Yurchenko, L. C. Smith, D. Minniti,
R. K. Saito, A. Bayo, M. Catelan, J. Alonso-García, A. Caratti o Garatti, C. Morris, D. Froebrich, J. Tennyson,
K. Maucó, A. Aguayo, N. Miller, H. D. S. Muthu F During the pre-main-sequence (pre-MS) evolution stage of astar, significant amounts of stellar mass are accreted during episodic accretion events, such as multi-decade FUor-type
outbursts. Here, we present a near-infrared spectroscopic follow-up study of 33 high-amplitude (most with ∆Ks >4 mag) variable sources discovered by the Vista Variables in the Via Lactea (VVV) survey. Based on the spectralfeatures, 25 sources are classified as eruptive young stellar objects (YSOs), including 15 newly identified FUors, sixwith long-lasting but EXor-like bursts of magnetospheric accretion and four displaying outflow-dominated spectra. By
examining the photometric behaviours of eruptive YSOs, we found most FUor-type outbursts have higher amplitudes(∆Ks and ∆W 2), faster eruptive timescales and bluer infrared colours than the other outburst types. In addition,
we identified seven post-main sequence variables apparently associated with deep dipping events and an eruptive starwith deep AlO absorption bands resembling those seen in the V838 Mon stellar merger.

31. Multi-wavelength detection of an ongoing FUOr-type outburst on a low-mass YSO
Zhen Guo, P. W. Lucas, R. G. Kurtev, J. Borissova, V. Elbakyan, C. Morris, A. Bayo, L. Smith, A. Carattio Garatti, C. Contreras Peña, D. Minniti, J. Jose, M. Ashraf, J. Alonso-García, N. Miller, H. D. S. Muthu

F During the pre-main-sequence evolution, Young Stellar Objects (YSOs) assemble most of their mass during theepisodic accretion process. The rarely seen FUOr-type events (FUOrs) are valuable laboratories to investigate theoutbursting nature of YSOs. Here, we present multi-wavelength detection of a high-amplitude eruptive source inthe young open cluster VdBH 221 with an ongoing outburst, including optical to mid-infrared time series and nearinfrared spectra. The initial outburst has an exceptional amplitude of >6.3 mag in Gaia and 4.6 mag in Ks , witha peak luminosity up to 16 L and a peak mass accretion rate of 1.4 × 10−5 M yr−1 . The optical to infrared
spectral energy distribution (SED) of this object is consistent with a low-mass star (0.2M ) with a modest extinction(AV < 2 mag). A 100-d delay between optical and infrared rising stages is detected, suggesting an outside-in originof the instability. The spectroscopic features of this object reveal a self-luminous accretion disc, very similar to FU
Orionis, with a low line-of-sight extinction. Most recently, there has been a gradual increase in brightness throughout
the wavelength range, possibly suggesting an enhancement of the mass accretion rate.

New insights on the accretion properties of Class 0 protostars from 2 micron spec32. troscopy
Valentin J. M. Le Gouellec, Thomas P. Greene, Lynne A. Hillenbrand, Zoe Yates F Sun-like stars are thoughtto accrete most of their final mass during the protostellar phase, during which the stellar embryo is surrounded by an
infalling dense envelope. We present an analysis of 26 K-band spectra of Class 0 protostars, which are the youngest
protostars. 18 of these are new observations made with the Keck MOSFIRE instrument. HI Brγ , several H2 , and CO∆ v = 2 features are detected and analyzed. We detect Brγ emission in 62%, CO overtone emission in 50%, and H2

12emission in 90% of sources. The HI and CO emission is associated with accretion while the H2 lines are consistent withshock excitation indicating jets/outflows. Six objects exhibit photospheric absorption features, with almost no outflow
activity, and no detection of the accretion-related Brγ emission line. Comparing these results with archival sample ofClass I K-band spectra, we find that the CO and Brγ emission lines are systematically more luminous in Class 0s,
suggesting the accretion is on average more vigorous in the Class 0 phase. Typically associated with the heated inneraccretion disk, the much higher detection rate of CO overtone emission in Class 0s indicate also that episodes of highaccretion activity are more frequent in Class 0 systems. The kinematics of the Class 0 CO overtone emission suggest
either an accretion-heated inner disk, or material directly infalling onto the central region. This could point toward
an accretion mechanism of different nature in Class 0 systems than the typical picture of magnetospheric accretion.

CMZoom IV. Incipient High-Mass Star Formation Throughout the Central Molecular
33. 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 over the next few 105 yr. We calculate upper and lower limits on the CMZ’s
incipient SFR of 0.45 Msun/yr and 0.05 Msun/yr respectively, spanning between roughly equal to and several times
greater than other estimates of CMZ’s recent SFR. Despite substantial uncertainties, our results suggest the incipient
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 in regions
above a column density ratio (NSM A /NHerschel ) of about 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.

34. Shadowing in the protoplanetary disk of ZZ Tau IRS with HST
Jun Hashimoto, Ruobing Dong, Takayuki Muto, Hauyu Baobab Liu, Yuka Terada F An inner component
misaligned from an outer component in a protoplanetary disk can result in the former casting shadows on the latter.
We present a new instance of shadowing on the outer disk around a very low mass star, ZZ Tau IRS. Through theanalysis of near-infrared (NIR) archival data at λ = 1.6 µm acquired with the Wide Field Camera 3 on the Hubble
Space Telescope, we identified brightness asymmetries in the top and bottom halves of the highly inclined outer disk,
separated by a dark lane. The brighter sides in the top and bottom halves are on the opposite sides, which we
attributed to shadows cast by a misaligned inner disk. Radiative transfer modeling of the system with a misaligned
angle of 15 deg between the inner and outer disks well reproduced the observations. Additionally, we found an elevatedbrightness temperature of 12 CO (3-2) at r ∼ 30 au on the brighter side in NIR wavelengths in the top half disk, which
can be explained by the shadowing effect too. While the origin of the misaligned inner disk remains unclear, future
monitoring observations to search for temporal variations in brightness asymmetries will likely provide useful clues.

35. The outflow of the protostar in B335: I
Klaus W. Hodapp, Laurie L. Chu, Thomas Greene, Michael R. Meyer, Doug Johnstone, Marcia J. Rieke,
John Stansberry, Martha Boyer, Charles Beichman, Scott Horner, Tom Roellig, George Rieke, Eric T. Young

F The isolated globule B335 contains a single, low luminosity Class 0 protostar associated with a bipolar nebulaand outflow system seen nearly perpendicular to its axis. We observed the innermost regions of this outflow as partof JWST/NIRCam GTO program 1187, primarily intended for wide-field slitless spectroscopy of background stars
behind the globule. We find a system of expanding shock fronts with kinematic ages of only a few decades emerging
symmetrically from the position of the embedded protostar, which is not directly detected at NIRCam wavelengths.
The innermost and youngest of the shock fronts studied here shows strong emission from CO. The next older shock
front shows less CO and the third shock front shows only H2 emission in our data. This third and most distant of13

these inner shock fronts shows substantial evolution of its shape since it was last observed with high spatial resolution
in 1996 with Keck/NIRC. This may be evidence of a faster internal shock catching up with a slower one and of thetwo shocks merging.

36. Protostellar disk accretion in turbulent filaments

Stefan Heigl, Elena Hoemann, Andreas Burkert F Recent observations of protostellar cores suggest that most of

the material in the protostellar phase is accreted along streamers. Streamers in this context are defined as velocity
coherent funnels of denser material potentially connecting the large scale environment to the small scales of the forming
accretion disk. Using simulations which simultaneously resolve the driving of turbulence on the filament scale as wellas the collapse of the core down to protostellar disk scales, we aim to understand the effect of the turbulent velocity
field on the formation of overdensities in the accretion flow. We perform a three-dimensional numerical study on acore collapse within a turbulent filament using the RAMSES code and analyse the properties of overdensities in theaccretion flow. We find that overdensities are formed naturally by the initial turbulent velocity field inherited from thefilament and subsequent gravitational collimation. This leads to streams which are not really filamentary but show asheet-like morphology. Moreover, they have the same radial infall velocities as the low density material. As a mainconsequence of the turbulent initial condition, the mass accretion onto the disk does not follow the predictions forsolid body rotation. Instead, most of the mass is funneled by the overdensities to intermediate disk radii.

Testing magnetospheric accretion as an Hα emission mechanism of embedded giant
37. planets: The case study for the disk exhibiting meridional flow around HD 163296
Yasuhiro Hasegawa, Taichi Uyama, Jun Hashimoto, Yuhiko Aoyama, Vincent Deo, Olivier Guyon, Julien
Lozi, Barnaby Norris, Motohide Tamura, Sebastien Vievard F Recent high-sensitivity observations reveal that

accreting giant planets embedded in their parental circumstellar disks can emit Hα at their final formation stages.
While the origin of such emission is not determined yet, magnetospheric accretion is currently a most plausible
hypothesis. In order to test this hypothesis further, we develop a simplified, but physical-based model and apply it
to our observations taken toward HD 163296 with Subaru/SCExAO+VAMPIRES. We specify under what conditions,embedded giant planets can undergo magnetospheric accretion and emit hydrogen lines. We find that when stellar
accretion rates are high, magnetospheric accretion becomes energetic enough to self-regulate the resulting emission. On
the other hand, if massive planets are embedded in disks with low accretion rates, earlier formation histories determine
whether magnetospheric accretion occurs. We explore two different origins of hydrogen emission lines (magnetosphericaccretion flow heated by accretion-related processes vs planetary surfaces via accretion shock). The corresponding
relationships between the accretion and line luminosities dictate that emission from accretion flow achieves higher line
flux than that from accretion shock and the flux decreases with increasing wavelengths (i.e., from Hα to Paβ and up
to Brγ). Our observations do not detect any point-like source emitting Hα and are used to derive the 5σ detection
limit. The observations are therefore not sensitive enough, and reliable examination of our model becomes possible if
observational sensitivity will be improved by a factor of ten or more. Multi-band observations increase the possibilityof efficiently detecting embedded giant planets and carefully determining the origin of hydrogen emission lines.

38. Cloudlet Capture Model for the Accretion Streamer onto the disk of DG Tau
Tomoyuki Hanawa, Antonio Garufi, Linda Podio, Claudio Codella, Dominique Segura-Cox F DG Tau is a nearby

T Tauri star associated with a collimated jet, a circumstellar disk and a streamer a few hundred au long. The streamer
connects to the disk at ∼50 au from DG Tau. At this location SO emission is observed, likely due to the release ofsulphur from dust grains caused by the shock of the impact of the accretion streamer onto the disk. We investigate thepossibility that the DG Tau streamer was produced via cloudlet capture on the basis of hydrodynamic simulations,considering a cloudlet initiating infall at 600 au from DG Tau with low angular momentum so that the centrifugal
force is smaller than the gravitational force, even at 50 au. The elongation of the cloudlet into a streamer is caused by
the tidal force when its initial velocity is much less than the free-fall velocity. The elongated cloudlet reaches the disk
and forms a high density gas clump. Our hydrodynamic model reproduces the morphology and line-of-sight velocity
of CS (5 − 4) emission from the Northern streamer observed with ALMA. We discuss the conditions for forming a
streamer based on the simulations. We also show that the streamer should perturb the disk after impact for several
thousands of years.

14The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). X: Hot
39. 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.

40. The 2022-2023 accretion outburst of the young star V1741 SgrMichael A. Kuhn, Lynne A. Hillenbrand, Michael S. Connelley, R. Michael Rich, Bart Staels, Adolfo S.
Carvalho, Philip W. Lucas, Christoffer Fremling, Viraj R. Karambelkar, Ellen Lee, Tomás Ahumada, Emille
E. O. Ishida, Kishalay De, Rafael S. de Souza, Mansi Kasliwal F V1741 Sgr (= SPICY 71482/Gaia22dtk) is aClassical T Tauri star on the outskirts of the Lagoon Nebula. After at least a decade of stability, in mid-2022, theoptical source brightened by 3 mag over two months, remained bright until early 2023, then dimmed erratically overthe next four months. This event was monitored with optical and infrared spectroscopy and photometry. Spectrafrom the peak (October 2022) indicate an EX Lup-type (EXor) accretion outburst, with strong emission from H I,
He I, and Ca II lines and CO bands. At this stage, spectroscopic absorption features indicated a temperature of
T 4750 K with low-gravity lines (e.g., Ba II and Sr II). By April 2023, with the outburst beginning to dim, strong
TiO absorption appeared, indicating a cooler T 3600 K temperature. However, once the source had returned to its
pre-outburst flux in August 2023, the TiO absorption and the CO emission disappeared. When the star went into
outburst, the source’s spectral energy distribution became flatter, leading to bluer colours at wavelengths shorter than
1.6 microns and redder colours at longer wavelengths. The brightening requires a continuum emitting area larger than
the stellar surface, likely from optically thick circumstellar gas with cooler surface layers producing the absorption
features. Additional contributions to the outburst spectrum may include blue excess from hotspots on the stellar
surface, emission lines from diffuse gas, and reprocessed emission from the dust disc. Cooling of the circumstellar
gas would explain the appearance of TiO, which subsequently disappeared once this gas had faded and the stellar
spectrum reemerged.

41. The Initial Mass Function Based on the Full-sky 20-pc Census of ∼3,600 Stars andBrown Dwarfs
J. Davy Kirkpatrick, Planet 9 Collaboration F A complete accounting of nearby objects – from the highest-mass

white dwarf progenitors down to low-mass brown dwarfs – is now possible, thanks to an almost complete set of
trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census
of objects within a Sun-centered sphere of 20-pc radius and check published literature to decompose each binaryor higher-order system into its separate components. The result is a volume-limited census of ∼3,600 individual
star formation products useful in measuring the initial mass function across the stellar (< 8M ) and substellar(& 5MJup ) regimes. Comparing our resulting initial mass function to previous measurements shows good agreement
above 0.8M and a divergence at lower masses. Our 20-pc space densities are best fit with a quadripartite power law,ξ(M ) = dN/dM ∝ M −α with long-established values of α = 2.3 at high masses (0.55 < M < 8.00M ) and α = 1.3 atintermediate masses (0.22 < M < 0.55M ), but at lower masses we find α = 0.25 for 0.05 < M < 0.22M and α = 0.6
for 0.01 < M < 0.05M . This implies that the rate of production as a function of decreasing mass diminishes in the
low-mass star/high-mass brown dwarf regime before increasing again in the low-mass brown dwarf regime. Correcting
for completeness, we find a star to brown dwarf number ratio of, currently, 4:1, and an average mass per object of 0.41
M .

15

42. The CO outflow components ejected by a recent accretion event in B335

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.

Spatially resolving the volatile sulfur abundance in the HD 100546 protoplanetary disk
43. Luke Keyte, Mihkel Kama, Ko-Ju Chuang, L. Ilsedore Cleeves, Maria N. Drozdovskaya, Kenji Furuya, Jonathan
Rawlings, Oliver Shorttle F Volatile elements play a crucial role in the formation of planetary systems. Theirabundance and distribution in protoplanetary disks provide vital insights into the connection between formation
processes and the atmospheric composition of individual planets. Sulfur, being one of the most abundant elements inplanet-forming environments, is of great significance, and now observable in exoplanets with JWST. However, planetary
formation models currently lack vital knowledge regarding sulfur chemistry in protoplanetary disks. Developing a
deeper understanding of the major volatile sulfur carriers in disks is essential to building models that can meaningfully
predict planetary atmospheric composition, and reconstruct planetary formation pathways. In this work, we combine
archival observations with new data from ALMA and APEX, covering a range of sulfur-bearing species/isotopologs.
We interpret this data using the DALI thermo-chemical code, for which our model is highly refined and disk-specific.
We find that volatile sulfur is heavily depleted from the cosmic value by a factor of 1000, with a disk-averaged
abundance of S/H = 1e-8. We show that the gas-phase sulfur abundance varies radially by 3 orders of magnitude,with the highest abundances inside the inner dust ring and coincident with the outer dust ring at 150 to 230 au.
Extracting chemical abundances from our models, we find OCS, H2CS, and CS to be the dominant molecular carriersin the gas phase. We also infer the presence of a substantial OCS ice reservoir. We relate our results to the potential
atmospheric composition of planets in HD 100546, and the wider exoplanet population

44. Mapping the Vertical Gas Structure of the Planet-hosting PDS 70 Disk
Charles J. Law, Myriam Benisty, Stefano Facchini, Richard Teague, Jaehan Bae, Andrea Isella, Inga Kamp,
Karin I. Öberg, Bayron Portilla-Revelo, Luna Rampinelli F PDS 70 hosts two massive, still-accreting planetsand the inclined orientation of its protoplanetary disk presents a unique opportunity to directly probe the verticalgas structure of a planet-hosting disk. Here, we use high-spatial-resolution (≈0."1;10 au) observations in a set of CO
isotopologue lines and HCO+ J=4-3 to map the full 2D (r, z) disk structure from the disk atmosphere, as traced by
12
CO, to closer to the midplane, as probed by less abundant isotopologues and HCO+ . In the PDS 70 disk, 12 CO
traces a height of z/r ≈ 0.3, 13 CO is found at z/r ≈ 0.1, and C18 O originates at, or near, the midplane. The HCO+
surface arises from z/r ≈ 0.2 and is one of the few non-CO emission surfaces constrained with high fidelity in disks
to date. In the 12 CO J=3-2 line, we resolve a vertical dip and steep rise in height at the cavity wall, making PDS 70
the first transition disk where this effect is directly seen in line emitting heights. In the outer disk, the CO emission
heights of PDS 70 appear typical for its stellar mass and disk size and are not substantially altered by the two innerembedded planets. By combining CO isotopologue and HCO+ lines, we derive the 2D gas temperature structure andestimate a midplane CO snowline of ≈56-85 au. This implies that both PDS 70b and 70c are located interior to the
CO snowline and are likely accreting gas with a high C/O ratio of ≈1.0, which provides context for future planetaryatmospheric measurements from, e.g., JWST, and for properly modeling their formation histories.

1646. 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,
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.

Protoplanetary disk size under non-ideal magnetohydrodynamics: A general formalism
47. with inclined magnetic field
Yueh-Ning Lee, Barshan Ray, Pierre Marchand, Patrick Hennebelle F Many mechanisms have been proposed
to alleviate the magnetic catastrophe, which prevents the Keplerian disk from forming inside a collapsing magnetizedcore. Such propositions include inclined field and non-ideal magnetohydrodynamics effects, and have been supportedwith numerical experiments. Models have been formulated for typical disk sizes when a field threads the rotating disk,
parallel to the rotation axis, while observations at the core scales do not seem to show evident correlation between the
directions of angular momentum and the magnetic field. In the present study, we propose a new model that considers
both vertical and horizontal fields and discuss their effects on the protoplanetary disk size.

Can the giant planets of the Solar System form via pebble accretion in a smooth pro48. toplanetary disc?
Tommy Chi Ho Lau, Man Hoi Lee, Ramon Brasser, Soko Matsumura F Prevailing N -body planet formation

models typically start with lunar-mass embryos and show a general trend of rapid migration of massive planetarycores to the inner Solar System in the absence of a migration trap. This setup cannot capture the evolution from aplanetesimal to embryo, which is crucial to the final architecture of the system. We aim to model planet formation
with planet migration starting with planetesimals of ∼ 10−6 – 10−4 M⊕ and reproduce the giant planets of the Solar
System. We simulated a population of 1,000 – 5,000 planetesimals in a smooth protoplanetary disc, which was evolved
under the effects of their mutual gravity, pebble accretion, gas accretion, and planet migration, employing the parallelized N -body code SyMBAp. We find that the dynamical interactions among growing planetesimals are vigorousand can halt pebble accretion for excited bodies. While a set of results without planet migration produces one to two
gas giants and one to two ice giants beyond 6 au, massive planetary cores readily move to the inner Solar System once
planet migration is in effect. Dynamical heating is important in a planetesimal disc and the reduced pebble encounter
time should be considered in similar models. Planet migration remains a challenge to form cold giant planets in asmooth protoplanetary disc, which suggests an alternative mechanism is required to stop them at wide orbits.

49. Formation of flattened planetesimals by gravitational collapse of rotating pebble clouds
Sebastian Lorek, Anders Johansen F Planetesimals are believed to form by the gravitational collapse of aerodynamically concentrated clumps of pebbles. Many properties of the objects in the cold classical Kuiper belt – such as
binarity, rotation, and size distribution – are in agreement with this gravitational collapse model. Further support
comes from the pebble-pile structure inferred for comet nuclei. For this study, we simulated the final assembly of aplanetesimal from the gravitational collapse of a rotating clump of pebbles. We implemented a numerical methodfrom granular dynamics to follow the collapse that includes the transition from a pebble swarm to solid cells at ahigh density. We compared the shapes of the simulated planetesimals with the shapes of the lobes of contact binaries

17and bilobed Solar System objects. We find that the gravitational collapse of slowly rotating pebble clouds naturally
explains the formation of flattened ellipsoidal bodies. This result agrees well with the flattened structure of the bilobed
planetesimal Arrokoth and the shapes of the components of bilobed comets.

51. Observations of high-order multiplicity in a high-mass stellar protocluster

Shanghuo Li, Patricio Sanhueza, Henrik Beuther, Huei-Ru Vivien Chen, Rolf Kuiper, Fernando A. Olguin,
Ralph E. Pudritz, Ian W. Stephens, Qizhou Zhang, Fumitaka Nakamura, Xing Lu, Rajika L. Kuruwita, Takeshi
Sakai, Thomas Henning, Kotomi Taniguchi, Fei Li F The dominant mechanism forming multiple stellar systems in

the high-mass regime (M∗ & 8 M ) remained unknown because direct imaging of multiple protostellar systems at earlyphases of high-mass star formation is very challenging. High-mass stars are expected to form in clustered environments
containing binaries and higher-order multiplicity systems. So far only a few high-mass protobinary systems, and no
definitive higher-order multiples, have been detected. Here we report the discovery of one quintuple, one quadruple, one
triple and four binary protostellar systems simultaneously forming in a single high-mass protocluster, G333.23–0.06,
using Atacama Large Millimeter/submillimeter Array high-resolution observations. We present a new example of agroup of gravitationally bound binary and higher-order multiples during their early formation phases in a protocluster.
This provides the clearest direct measurement of the initial configuration of primordial high-order multiple systems,with implications for the in situ multiplicity and its origin. We find that the binary and higher-order multiple
systems, and their parent cores, show no obvious sign of disk-like kinematic structure. We conclude that the observed
fragmentation into binary and higher-order multiple systems can be explained by core fragmentation, indicating its
crucial role in establishing the multiplicity during high-mass star cluster formation.

52. Multiple Jets in the bursting protostar HOPS 373SW

Seokho Lee, Jeong-Eun Lee, Doug Johnstone, Gregory J. Herczeg, Yuri Aikawa F We present the outflows

detected in HOPS 373SW, a protostar undergoing a MMS 6), one Class I (MMS 7), and one flat-spectrum (MMS 2)
sources in the Orion Molecular Cloud 3 region. The dust disk-like structures and clear CO outflows are detected
towards all sources except for MMS 4. The diameters of these disk-like structures, 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, 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 vectorsaligned 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-like structure, as reported by Takahashi et al.
(2019). The origins of the polarized emission, such as self-scattering and dust alignment due to the magnetic field orradiative torque, are discussed for individual sources. Some disk-like sources exhibit a polarized intensity peak shift
towards the nearside of the disk, which supports that the polarized emission originates from self-scattering.

53. Protoplanetary disk size under non-ideal magnetohydrodynamics: A general formalismwith inclined magnetic field
Yueh-Ning Lee, Barshan Ray, Pierre Marchand, Patrick Hennebelle F Many mechanisms have been proposed
to alleviate the magnetic catastrophe, which prevents the Keplerian disk from forming inside a collapsing magnetizedcore. Such propositions include inclined field and non-ideal magnetohydrodynamics effects, and have been supportedwith numerical experiments. Models have been formulated for typical disk sizes when a field threads the rotating disk,
parallel to the rotation axis, while observations at the core scales do not seem to show evident correlation between the
directions of angular momentum and the magnetic field. In the present study, we propose a new model that considers
both vertical and horizontal fields and discuss their effects on the protoplanetary disk size.

Can the giant planets of the Solar System form via pebble accretion in a smooth pro54. toplanetary disc?
Tommy Chi Ho Lau, Man Hoi Lee, Ramon Brasser, Soko Matsumura F Prevailing N -body planet formation

models typically start with lunar-mass embryos and show a general trend of rapid migration of massive planetarycores to the inner Solar System in the absence of a migration trap. This setup cannot capture the evolution from aplanetesimal to embryo, which is crucial to the final architecture of the system. We aim to model planet formation
18

with planet migration starting with planetesimals of ∼ 10−6 – 10−4 M⊕ and reproduce the giant planets of the Solar
System. We simulated a population of 1,000 – 5,000 planetesimals in a smooth protoplanetary disc, which was evolved
under the effects of their mutual gravity, pebble accretion, gas accretion, and planet migration, employing the parallelized N -body code SyMBAp. We find that the dynamical interactions among growing planetesimals are vigorousand can halt pebble accretion for excited bodies. While a set of results without planet migration produces one to two
gas giants and one to two ice giants beyond 6 au, massive planetary cores readily move to the inner Solar System once
planet migration is in effect. Dynamical heating is important in a planetesimal disc and the reduced pebble encounter
time should be considered in similar models. Planet migration remains a challenge to form cold giant planets in asmooth protoplanetary disc, which suggests an alternative mechanism is required to stop them at wide orbits.

55.

Formation of flattened planetesimals by gravitational collapse of rotating pebble clouds
Sebastian Lorek, Anders Johansen F Planetesimals are believed to form by the gravitational collapse of aerodynamically concentrated clumps of pebbles. Many properties of the objects in the cold classical Kuiper belt – such as
binarity, rotation, and size distribution – are in agreement with this gravitational collapse model. Further support
comes from the pebble-pile structure inferred for comet nuclei. For this study, we simulated the final assembly of aplanetesimal from the gravitational collapse of a rotating clump of pebbles. We implemented a numerical methodfrom granular dynamics to follow the collapse that includes the transition from a pebble swarm to solid cells at ahigh density. We compared the shapes of the simulated planetesimals with the shapes of the lobes of contact binaries
and bilobed Solar System objects. We find that the gravitational collapse of slowly rotating pebble clouds naturally
explains the formation of flattened ellipsoidal bodies. This result agrees well with the flattened structure of the bilobed
planetesimal Arrokoth and the shapes of the components of bilobed comets.

56. Observations of high-order multiplicity in a high-mass stellar protocluster

Shanghuo Li, Patricio Sanhueza, Henrik Beuther, Huei-Ru Vivien Chen, Rolf Kuiper, Fernando A. Olguin,
Ralph E. Pudritz, Ian W. Stephens, Qizhou Zhang, Fumitaka Nakamura, Xing Lu, Rajika L. Kuruwita, Takeshi
Sakai, Thomas Henning, Kotomi Taniguchi, Fei Li F The dominant mechanism forming multiple stellar systems in

the high-mass regime (M∗ & 8 M ) remained unknown because direct imaging of multiple protostellar systems at earlyphases of high-mass star formation is very challenging. High-mass stars are expected to form in clustered environments
containing binaries and higher-order multiplicity systems. So far only a few high-mass protobinary systems, and no
definitive higher-order multiples, have been detected. Here we report the discovery of one quintuple, one quadruple, one
triple and four binary protostellar systems simultaneously forming in a single high-mass protocluster, G333.23–0.06,
using Atacama Large Millimeter/submillimeter Array high-resolution observations. We present a new example of agroup of gravitationally bound binary and higher-order multiples during their early formation phases in a protocluster.
This provides the clearest direct measurement of the initial configuration of primordial high-order multiple systems,with implications for the in situ multiplicity and its origin. We find that the binary and higher-order multiple
systems, and their parent cores, show no obvious sign of disk-like kinematic structure. We conclude that the observed
fragmentation into binary and higher-order multiple systems can be explained by core fragmentation, indicating its
crucial role in establishing the multiplicity during high-mass star cluster formation.

57. Multiple Jets in the bursting protostar HOPS 373SW
Seokho Lee, Jeong-Eun Lee, Doug Johnstone, Gregory J. Herczeg, Yuri Aikawa F We present the outflows

detected in HOPS 373SW, a protostar undergoing a modest 30% brightness increase at 850 µm. Atacama Large
Millimeter/submillimeter Array (ALMA) observations of shock tracers, including SiO 8–7, CH3 OH 7k –6k , and 12 CO
3–2 emission, reveal several outflow features around HOPS 373SW. The knots in the extremely high-velocity SiO
emission reveal the wiggle of the jet, for which a simple model derives a 37◦ inclination angle of the jet to the planeof the sky, a jet velocity of 90 km s−1 , and a period of 50 years. The slow SiO and CH3 OH emission traces U-shaped
bow shocks surrounding the two CO outflows. One outflow is associated with the high-velocity jets, while the otheris observed to be close to the plane of the sky. The misaligned outflows imply that previous episodic accretion events
have either reoriented HOPS 373SW or that it is an unresolved protostellar binary system with misaligned outflows.

1958. The most variable VVV sources: eruptive protostars, dipping giants in the Nuclear Discand others
P. W. Lucas, L. C. Smith, Z. Guo, C. Contreras Peña, D. Minniti, N. Miller, J. Alonso-García, M. Catelan, J.
Borissova, R. K. Saito, R. Kurtev, M. G. Navarro, C. Morris, H. Muthu, D. Froebrich, V. D. Ivanov, A. Bayo,
A. Caratti o Garatti, J. L. Sanders F We have performed a comprehensive search of a VISTA Variables in the

Via Lactea (VVV) database of 9.5 yr light curves for variable sources with ∆Ks ≥ 4 mag, aiming to provide a large
sample of high amplitude eruptive young stellar objects (YSOs) and detect unusual or new types of infrared variable
source. We find 222 variable or transient sources in the Galactic bulge and disc, most of which are new discoveries.
The sample mainly comprises novae, YSOs, microlensing events, Long Period Variable stars (LPVs) and a few rare or
unclassified sources. Additionally, we report the discovery of a significant population of aperiodic late-type giant stars
suffering deep extinction events, strongly clustered in the Nuclear Disc of the Milky Way. We suggest that these aremetal-rich stars in which radiatively driven mass loss has been enhanced by super-solar metallicity. Among the YSOs,
32/40 appear to be undergoing episodic accretion. Long-lasting YSO eruptions have a typical rise time of ∼2 yr,somewhat slower than the 6-12 month timescale seen in the few historical events observed on the rise. The outburst
durations are usually at least 5 yr, somewhat longer than many lower amplitude VVV events detected previously. The
light curves are diverse in nature, suggesting that multiple types of disc instability may occur. Eight long-duration
extinction events are seen wherein the YSO dims for a year or more, attributable to inner disc structure. One binary
YSO in NGC 6530 displays periodic extinction events (P=59 days) similar to KH 15D.

59. Photoevaporation from Inner Protoplanetary Disks Confronted with Observations

Yiren Lin, Lile Wang, Min Fang, Ahmad Nemer, Jeremy Goodman F The decades-long explorations on thedispersal of protoplanetary disks involve many debates about photoevaporation versus magnetized wind launchingmechanisms. This letter argues that the observed winds originating from the inner disk (R . 0.3 AU) cannot be
explained by the photoevaporative mechanism. Energy conservation requires the presumed photoevaporative winds
to be heated to & 105 K when launched from inner disks. However, due to efficient thermal accommodation with dust
grains and cooling processes at high densities, X-ray irradiation at energies above 1 keV cannot efficiently launch winds
in the first place because of its high penetration. Some studies claiming X-ray wind launching have oversimplified thethermochemical couplings. Furthermore, heating the gas to escape velocity will over-ionize it, suppressing the species
responsible for observed forbidden lines (e.g., [OI] 6300 A). Confirmed by semi-analytic integrations of thermochemical
fluid structures, such high ionizations contradict the observed emission of neutral and singly-ionized atoms from thewinds originating from the inner disks.

60. Massive clumps in W43-main: Structure formation in an extensively shocked molecular
cloud
Yuxin Lin, Friedrich Wyrowski, Hauyu Baobab Liu, Yan Gong, Olli Sipilä, Andrés F. Izquierdo, Timea Csengeri,
Adam Ginsburg, Guang-Xing Li, Silvia Spezzano, Jaime E. Pineda, Silvia Leurini, Paola Caselli, Karl M.
Menten F W43-main is a massive molecular complex located at the interaction of the Scutum arm and the Galactic

bar undergoing starburst activities. We aim to investigate the gas dynamics, in particular, the prevailing shock
signatures from the cloud to clump scale and assess the impact of shocks on the formation of dense gas and early-stage
cores. We have carried out NOEMA and IRAM-30m observations at 3 mm with an angular resolution of ∼0.1 pc
towards five massive clumps in W43 main. We use CH3 CCH and H2 CS lines to trace the extended gas temperature andCH3 OH lines to probe the volume density of the dense gas (&105 cm−3 ). The emission of SiO (2-1) is extensive acrossthe region (∼4 pc) and is mostly contained within a low-velocity regime, hinting at a large-scale origin of the shocks.
The position-velocity maps of multiple tracers show systematic spatio-kinematic offsets supporting the cloud-cloud
collision/merging scenario. We identify an additional extended velocity component in CCH emission, which coincides
with one of the velocity components of the larger scale 13 CO (2-1) emission, likely representing an outer, less dense
gas layer in the cloud merging process. We find that the V-shaped, asymmetric SiO wings are tightly correlated withlocalised gas density enhancements, which is direct evidence of dense gas formation and accumulation in shocks. We
resolve two categories of NH2 D cores: ones exhibiting only subsonic to transonic velocity dispersion, and the otherswith an additional supersonic velocity dispersion. The centroid velocities of the latter cores are correlated with theshock front seen by SiO. The kinematics of the ∼0.1 pc NH2 D cores are heavily imprinted by shock activities, andmay represent a population of early-stage cores forming around the shock interface.

20

61. Forming localized dust concentrations in a dust ring? A case study on DM Tau

Hauyu Baobab Liu, Takayuki Muto, Mihoko Konishi, Chia-Ying Chung, Jun Hashimoto, Kiyoaki Doi, Ruobing
Dong, Tomoyuki Kudo, Yasuhiro Hasegawa, Yuka Terada, Akimasa Kataoka F The previous, high angularresolution 225 GHz (∼1.3 mm) continuum observations on the transitional disk DM Tau have resolved an outer ringat 20-120 au radii that is weakly azimuthally asymmetric. We aimed to examine dust growth and filtration in theouter ring. We performed the ∼000 .06 (∼8.7 au) resolution Karl G. Jansky Very Large Array (JVLA) 40-48 GHz(∼7 mm; Q band) continuum observations and the complementary observations at lower frequencies. In addition, we
analyzed the archival JVLA observations that were taken since 2010. Intriguingly, the Q band image resolved theazimuthally highly asymmetric, knotty dust emission sources close to the inner edge of the outer ring. Fitting the
8-700 GHz spectral energy distribution (SED) with two dust components indicates that the maximum grain size inthese knotty dust emission sources is likely &300 µm while it is .50 µm in the rest of the ring. These results may
be explained by trapping of inward migrating grown dust close to the ring inner edge. The exact mechanism fordeveloping the azimuthal asymmetry has not yet been identified, which may be due to planet-disk interaction thatmight also be responsible for the creation of the dust cavity and pressure bump, or the fluid instabilities and vortex
formation due to shear motions. Finally, we remark that the asymmetries in DM Tau are hard to diagnose fromthe &225 GHz observations owing to a high optical depth at the ring. In other words, the apparent symmetric or
asymmetric morphology of the transitional disks may be related to the optical depths of those disks at the observing
frequency.

62. Tracing the layers of Photodissociated gas in Trifid Nebula

Bhaswati Mookerjea, Goeran Sandell F Photodissociated gas bears the signature of the dynamical evolution of theambient interstellar medium impacted by the mechanical and radiative feedback from an expanding HII region. Here
we present an analysis of the kinematics of the young Trifid nebula, based on velocity-resolved observations of the
far-infrared fine-structure lines of [C II] at 158 micron and [O I] at 63 micron. The distribution of the photodissociatedregions (PDRs) surrounding the nebula is consistent with a shell-like structure created by the HII region expanding
with a velocity of 5 km/s. Comparison of ratios of [C II] and [O I] 63 micron intensities for identical velocity components
with PDR models indicate a density of 1e4 cm−3 . The red- and blue-shifted PDR shells with a combined mass of 516
Msun have a kinetic energy of 1e47 erg. This is consistent with the thermal energy of the HII region as well as withthe energy deposited by the stellar wind luminosity from HD 169442A, an O7 V star, over the 0.5 Myr lifetime ofthe star. The observed momentum of the PDR shell is lower than what theoretical calculations predict for the radial
momentum due to the shell being swept up by an expanding HII region, which suggests that significant mass loss has
occurred in M20 due to the dispersal of the surrounding gas by the advancing ionization front.

CN Zeeman Effect Observations of the Envelopes of a Low-Mass Protostellar
63. Modeling
Disk and a Massive Protostar
Renato Mazzei, Zhi-Yun Li, Che-Yu Chen, Yisheng Tu, Laura Fissel, Richard I. Klein F We use the POLARIS

radiative transfer code to produce simulated circular polarization Zeeman emission maps of the CN J = 1−0 molecularline transition for two types of protostellar envelope magnetohydrodynamic simulations. Our first model is a low mass
disk envelope system (box length L = 200 au), and our second model is the envelope of a massive protostar (L = 104 au)with a protostellar wind and a CN enhanced outflow shell. We compute the velocity-integrated Stokes I and V , aswell as the implied V /I polarization percentage, for each detector pixel location in our simulated emission maps. Our
results show that both types of protostellar environment are in principle accessible with current circular polarization
instruments, with each containing swaths of envelope area that yield percentage polarizations that exceed the 1.8%
nominal sensitivity limit for circular polarization experiments with the Atacama Large Millimeter/submillimeter Array(ALMA). In both systems, high polarization (&1.8%) pixels tend to lie at an intermediate distance away from thecentral star and where the line-center opacity of the CN emission is moderately optically thin (τLC ∼ 0.1 − 1).
Furthermore, our computed V /I values scale roughly with the density weighted mean line-of-sight magnetic fieldstrength, indicating that Zeeman observations can effectively diagnose the strength of envelope-scale magnetic fields.
We also find that pixels with large V /I are preferentially co-located where the absolute value of the velocity-integrated
V is also large, suggesting that locations with favorable percentage polarization are also favorable in terms of raw
signal.

21

64. Color measurements of the polarized light scattered by the dust in protoplanetary disksJ. Ma, H. M. Schmid, T. Stolker F Ground-based high-contrast instruments have yielded reflected light images ofprotoplanetary disks. Quantitative measurements of the reflected radiation provide strong constraints on the scattering
dust which can clarify the dust particle evolution in these disks and the composition of the forming planets. This study
aimed to derive the wavelength dependence of polarized reflectivity (Q̂ϕ /I? )λ for 11 disks, constraining dust properties and identifying systematic differences. Using ESO archive data from SPHERE/ZIMPOL and SPHERE/IRDIS
instruments, we obtained accurate intrinsic polarized reflectivity Q̂ϕ /I? values at wavelengths from 0.62µm to 2.2µm.
Polarized reflectivities ranged from Qϕ /I? ≈ 0.1% to 1.0%, with PSF-corrected values averaging 1.6 times higher thanobserved. Accurate PSF calibrations reduced systematic errors to ∆Q̂ϕ /Q̂ϕ ≈ 10% or less. For each disk, we derived apolarized reflectivity color ηV /IR between a visible band λ < 1 µm and a near-IR band λ > 1 µm and other wavelength
combinations. Wavelength gradients η varied significantly among objects. Disks around Herbig stars (HD 169142, HD
135334B, HD 100453, MWC 758, and HD 142527) showed a red color ηV/IR > 0.5, suggesting rather compact dust
grains. T-Tauri star disks (PDS 70, TW Hya, RX J1615, and PDS 66) were predominantly gray −0.5 < ηV/IR < 0.5,
with an absence of blue colors incompatible with porous aggregates. Exceptional red colors for LkCa15 and MWC758
were attributed to potential extra reddening from hot dust near the star. Future studies incorporating parameters likefractional polarization hpϕ i hold promise for advancing our understanding of dust properties within protoplanetarydisks.

The GAPS programme at TNG LII. Spot modeling of V1298 Tau using SpotCCF tool
65. C. Di Maio, A. Petralia, G. Micela, A. F. Lanza, M. Rainer, L. Malavolta, S. Benatti, L. Affer, J. Maldonado,
S. Colombo, M. Damasso, A. Maggio, K. Biazzo, A. Bignamini, F. Borsa, W. Boschin, L. Cabona, M. Cecconi,
R. Claudi, E. Covino, L. Di Fabrizio, R. Gratton, V. Lorenzi, L. Mancini, S. Messina, E. Molinari, M. Molinaro,
D. Nardiello, E. Poretti, A. Sozzetti F The intrinsic variability due to the magnetic activity of young active stars

is one of the main challenges in detecting and characterising exoplanets. We present a method able to model thestellar photosphere and its surface inhomogeneities (starspots) in young/active and fast-rotating stars, based on the
cross-correlation function (CCF) technique, to extract information about the spot configuration of the star. Within
the Global Architecture of Planetary Systems (GAPS) Project at the Telescopio Nazionale Galileo, we analysed morethan 300 spectra of the young planet-hosting star V1298 Tau provided by HARPS-N high-resolution spectrograph. By
applying the SpotCCF model to the CCFs we extracted the spot configuration (latitude, longitude and projected filling
factor) of this star, and also provided the new RVs time series of this target. We find that the features identified in the
CCF profiles of V1298 Tau are modulated by the stellar rotation, supporting our assumption that they are caused bystarspots. The analysis suggests a differential rotation velocity of the star with lower rotation at higher latitudes. Also,
we find that SpotCCF provides an improvement in RVs extraction with a significantly lower dispersion with respect
to the commonly used pipelines, with consequent mitigation of the stellar activity contribution modulated with stellar
rotation. A detection sensitivity test, by the direct injection of a planetary signal into the data, confirmed that the
SpotCCF model improves the sensitivity and ability to recover planetary signals. Our method enables the modellingof the stellar photosphere, extracting the spot configuration of young/active and rapidly rotating stars. It also allows
for the extraction of optimised RV time series, thereby enhancing our detection capabilities for new exoplanets andadvancing our understanding of stellar activity.

66. The JCMT Transient Survey: Six-Year Summary of 450/850 µm Protostellar Variability
and Calibration Pipeline Version 2.0
Steve Mairs, Seonjae Lee, Doug Johnstone, Colton Broughton, Jeong-Eun Lee, Gregory J. Herczeg, Graham S.
Bell, Zhiwei Chen, Carlos Contreras-Peña, Logan Francis, Jennifer Hatchell, Mi-Ryang Kim, Sheng-Yuan Liu,
Geumsook Park, Keping Qiu, Yao-Te Wang, Xu Zhang, The JCMT Transient Team F The JCMT Transient

Survey has been monitoring eight Gould Belt low-mass star-forming regions since December 2015 and six somewhat
more distant intermediate-mass star-forming regions since February 2020 with SCUBA-2 on the JCMT at ShortS andLongS and with an approximately monthly cadence. We introduce our Pipeline v2 relative calibration procedures forimage alignment and flux calibration across epochs, improving on our previous Pipeline v1 by decreasing measurement
uncertainties and providing additional robustness. These new techniques work at both LongS and ShortNS, where v1
only allowed investigation of the LongS data. Pipeline v2 achieves better than 0.500 relative image alignment, less thana tenth of the submillimeter beam widths. The v2 relative flux calibration is found to be 1% at LongS and < 5% at
ShortNS. The improvement in the calibration is demonstrated by comparing the two pipelines over the first four years22

of the survey and recovering additional robust variables with v2. Using the full six years of the Gould Belt survey the
number of robust variables increases by 50 %, and at ShortS we identify four robust variables, all of which are also
robust at LongNS. The multi-wavelength light curves for these sources are investigated and found to be consistent
with the variability being due to dust heating within the envelope in response to accretion luminosity changes fromthe central source.

ALMA-QUARKS survey: Detection of two extremely dense substructures in a
67. Themassive prestellar core
Xiaofeng Mai, Tie Liu, Xunchuan Liu, Lei Zhu, Guido Garay, Paul F. Goldsmith, Mika Juvela, Hongli Liu,
Emma Mannfors, Emma Mannfors, Anandmayee Tej, Patricio Sanhueza, Shanghuo Li, Fengwei Xu, Enrique
Vazquez Semadeni, Wenyu Jiao, Yaping Peng, T. Baug, Aiyuan Yang, Lokesh Dewangan, Leonardo Bronfman,
Gilberto C. Gómez, Aina Palau, Chang Won Lee, Sheng-Li Qin, Ken’ichi Tatematsu, James O. Chibueze,
Dongting Yang, Xing Lu, Qiuyi Luo, Qilao Gu, Namitha Issac, Suinan Zhang, Pak-Shing Li, Bo Zhang, L.
Viktor Tóth F Only a handful of massive starless core candidates have been discovered so far, but none of them havebeen fully confirmed. Within the MM1 clump in the filamentary infrared dark cloud G34.43+0.24 that was covered by
the ALMA-ATOMS survey at Band 3 (∼ arcsec, 6000 au) and the ALMA-QUARKS survey at Band 6 (∼ 0.3 arcsec,
900 au), two prestellar core candidates MM1-C and E1 with masses of 71 and 20 Msun and radii of 2100–4400 au werediscovered. The two cores show no obvious sign of star-formation activities. In particular, MM1-C is a very promisingmassive prestellar core candidate with a total gas mass of 71 Msun. Within MM1-C, we detected two extremely dense
substructures, C1 and C2, as characterized by their high densities of nH2 ∼ 108−9 cm−3 . Moreover, evidence of further
fragmentation in C2 was also revealed. We have detected the primordial fragmentation in the earliest stage of massive
star formation, and we speculate that MM1-C would be the birthplace of a massive multiple system. However, wecannot fully rule out the possibility that the massive prestellar core MM1-C will just form a cluster of low-mass stars
if it undergoes further fragmentation.

Sub-kpc scale gas density histogram of the Galactic molecular gas: a new statistical
68. method to characterise galactic-scale gas structures
Ren Matsusaka, Toshihiro Handa, Yusuke Fujimoto, Takeru Murase, Yushi Hirata, Junya Nishi, Takumi Ito,
Megumi Sasaki, Tomoki Mizoguchi F To understand physical properties of the interstellar medium (ISM) on various

scales, we investigate it at parsec resolution on the kiloparsec scale. Here, we report on the sub-kpc scale Gas Density
Histogram (GDH) of the Milky Way. The GDH is a density probability distribution function (PDF) of the gas
volume density. Using this method, we are free from an identification of individual molecular clouds and their spatial
structures. We use survey data of 12 CO and 13 CO (J=1-0) emission in the Galactic plane (l = 10◦ -50◦ ) obtained
as a part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45m telescope (FUGIN). We
make a GDH for every channel map of 2◦ × 2◦ area, including the blank sky component, and without setting cloudboundaries. This is a different approach from previous works for molecular clouds. The GDH fits well to a single
or double log-normal distribution, which we name the low-density log-normal (L-LN) and high-density log-normal(H-LN) components, respectively. The multi-log-normal components suggest that the L-LN and H-LN components
originate from two different stages of structure formation in the ISM. Moreover, we find that both the volume ratios of
H-LN components to total (fH ) and the width of the L-LN along the gas density axis (σL ) show coherent structure in
the Galactic-plane longitude-velocity diagram. It is possible that these GDH parameters are related to strong galactic
shocks and other weak shocks in the Milky Way.

Evolution of the Angular Momentum of Molecular Cloud Cores in Magnetized Molec69. 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 domi-

23nant 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.

GIARPS High-resolution Observations of T Tauri stars (GHOST) V. New insights into
70. 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(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.

Hunting young stars in the Galactic centre. Hundreds of thousands of solar masses of
71. young stars in the Sagittarius C region
Francisco Nogueras-Lara F The Galactic centre stands out as the most prolific star-forming environment of the

Galaxy when averaged over volume. In the last 30 million years, it has witnessed the formation of ∼ 106 M of stars.
However, crowding and high extinction hamper their detection and, up to now, only a small fraction of the expectedmass of young stars has been identified. We aim to detect hidden young stars at the Galactic centre by analysing
the stellar population in Sagittarius (Sgr) C. This is a region at the western edge of the nuclear stellar disc whose
HII emission makes it a perfect candidate to host young stars. We built dereddened luminosity functions for Sgr
C and a control field in the central region of the nuclear stellar disc, and fitted them with a linear combination oftheoretical models to analyse their stellar population. We find that Sgr C hosts several 105 M of young stars. We
compared our results with the recently discovered young stellar population in Sgr B1, which is situated at the opposite
edge of the nuclear stellar disc. We estimated that the Sgr C young stars are ∼ 20 Myr old, and likely show thenext evolutionary step of the slightly younger stars in Sgr B1. Our findings contribute to addressing the discrepancy
between the expected and the detected number of young stars in the Galactic centre, and shed light on their evolution
in this extreme environment. As a secondary result, we find an intermediate-age stellar population in Sgr C (∼ 50
between 2 and 7 Gyr), which is not present in the innermost regions of the nuclear stellar disc (dominated by stars >7
Gyr). This supports the existence of an age gradient and favours an inside-out formation of the nuclear stellar disc.

24

Hunt for complex cyanides in protostellar ices with JWST: Tentative detection of
72. CH3 CN and C2 H5 CN
P. Nazari, W. R. M. Rocha, A. E. Rubinstein, K. Slavicinska, M. G. Rachid, E. F. van Dishoeck, S. T. Megeath,
R. Gutermuth, H. Tyagi, N. Brunken, M. Narang, P. Manoj, D. M. Watson, N. J. Evans II, S. Federman,
J. Muzerolle Page, G. Anglada, H. Beuther, P. Klaassen, L. W. Looney, M. Osorio, T. Stanke, Y. -L. Yang

F Nitrogen-bearing complex organic molecules have been commonly detected in the gas phase but not yet in interstellar ices. This has led to the long-standing question of whether these molecules form in the gas phase or in ices.
James Webb Space Telescope (JWST) offers the sensitivity, spectral resolution, and wavelength coverage needed todetect them in ices and investigate whether their abundance ratios are similar in gas and ice. We report the firsttentative detection of CH3 CN, C2 H5 CN, and the simple molecule, N2 O, based on the CN-stretch band in interstellar
ices toward three (HOPS 153, HOPS 370, and IRAS 20126+4104) out of the five protostellar systems observed as partof the Investigating Protostellar Accretion (IPA) GO program with JWST-NIRSpec. We also provide upper limits
for the two other sources with smaller luminosities in the sample. We detect OCN− in the ices of all sources withtypical CH3 CN/OCN− ratios of around 1. Ice and gas column density ratios of the nitrogen-bearing species withrespect to each other are better matched than those with respect to methanol, which are a factor of ∼5 larger in
the ices than the gas. We attribute the elevated ice column densities with respect to methanol to the difference insnowline locations of nitrogen-bearing molecules and of methanol, biasing the gas-phase observations toward fewer
nitrogen-bearing molecules. Moreover, we find tentative evidence for enhancement of OCN− , CH3 CN, and C2 H5 CN
in warmer ices, although formation of these molecules likely starts along with methanol in the cold prestellar phase.
Future surveys combining NIRSpec and MIRI, and additional laboratory spectroscopic measurements of C2 H5 CN ice,are necessary for robust detection and conclusions on the formation history of complex cyanides.

Outbursting Protostar: The environment of L1251 VLA 6
73. AnAva Nederlander, Adele Plunkett, Antonio Hales, Ágnes Kóspál, Jacob A. White, Makoto A. Johnstone, Mária
Kun, Péter Ábrahám, Anna G. Hughes F Young protostars that undergo episodic accretion can provide insight

into the impact on their circumstellar environments while matter is accreted from the disk onto the protostar. IRAS
22343+7501 is a four component protostar system with one of those being a fading outbursting protostar referred toas L1251 VLA 6. Given the rarity of YSOs undergoing this type of accretion, L1251 VLA 6 can elucidate the fading
phase of the post-outburst process. Here we examine structure in the disk around L1251 VLA 6 at frequencies of 10
GHz and 33 GHz with the Karl G. Jansky Very Large Array (VLA). We model the disk structure using Markov chain
Monte Carlo (MCMC). This method is then combined with a parametric ray-tracing code to generate synthetic model
images of an axisymmetric disk, allowing us to characterize the radial distribution of dust in the system. The resultsof our MCMC fit show that the most probable values for the mass and radius are consistent with values typical ofClass I objects. We find that the total mass of the disk is 0.070+0.031
Msun and investigate the conditions that could−0.2
cause the accretion outburst. We conclude that the eruption is not caused by gravitational instability and consider
alternative explanations and trigger mechanisms.

Revealing multiple nested molecular outflows with rotating signatures in HH270mms174. A with ALMA
Mitsuki Omura, Kazuki Tokuda, Masahiro N. Machida F We present molecular line observations of the protostellar

outflow associated with HH270mms1 in the Orion B molecular cloud with ALMA. The 12CO(J = 3 - 2) emissions
show that the outflow velocity structure consists of four distinct components of low (& 10 km s-1), intermediate ( 10
- 25 km s-1) and high (& 40 km s-1) velocities in addition to the entrained gas velocity ( 25 - 40 km s-1). The
high- and intermediate-velocity flows have well-collimated structures surrounded by the low-velocity flow. The chainof knots is embedded in the high-velocity flow or jet, which is the evidence of episodic mass ejections induced bytime-variable mass accretion. We could detect the velocity gradients perpendicular to the outflow axis in both thelow- and intermediate-velocity flows. We confirmed the rotation of the envelope and disk in the 13CO and C17O
emission and found that their velocity gradients are the same as those of the outflow. Thus, we concluded that thevelocity gradients in the low- and intermediate-velocity flows are due to the outflow rotation. Using observational
outflow properties, we estimated the outflow launching radii to be 67.1 - 77.1 au for the low-velocity flow and 13.3 20.8 au for the intermediate-velocity flow. Although we could not detect the rotation in the jets due to the limited
spatial resolution, we estimated the jet launching radii to be (2.36 - 3.14) x 10−2 au using the observed velocity of eachknots. Thus, the jet is driven from the inner disk region. We could identify the launching radii of distinct velocity
25components within a single outflow with all the prototypical characteristics expected from recent theoretical works.

75. Multiscale Dynamical Scenario of High-mass Star Formation in an IRDC Filament G34
Sirong Pan, Hong-Li Liu, Sheng-Li Qin F There is growing evidence that high-mass star formation (HMSF) is amultiscale, dynamical process in molecular clouds, where filaments transport gas material between larger and smallerscales. We analyze here multiscale gas dynamics in an HMSF filamentary cloud, G034.43+00.24 (G34), using APEX
observations of the C18O (2-1), HCO+/H13CO+ (3-2), and HCN/H13CN (3-2) lines. We find large-scale, filamentaligned velocity gradients from C18O emission, which drive filamentary gas inflows onto dense clumps in the middle
ridge of G34. The nature of these inflows is gravity driven. We also find clump-scale gas infall in the middle ridge ofthe MM2, MM4, and MM5 clumps from other lines. Their gas infall rates could depend on large-scale filamentary gas
inflows since the infall/inflow rates on these two scales are comparable. We confirm that the multiscale, dynamical
HMSF scenario is at work in G34. It could be driven by gravity up to the filament scale, beyond which turbulence
originating from several sources, including gravity, could be in effect in G34.

76. Low-mass stars: Their Protoplanetary Disc Lifetime Distribution

Susanne Pfalzner, Furkan Dincer F While most protoplanetary discs lose their gas within less than 10 Myr, individual

disc lifetimes vary from < 1 Myr to » 20 Myr, with some discs existing for > 40 Myr. Mean disc half lifetimes hide
this diversity; only a so-far non-existing disc lifetime distribution could capture this fact. The benefit of a disc lifetime
distribution would be twofold. First, it provides a stringent test on disc evolution theories. Second, it can function
as input for planet formation models. Here, we derive such a disc lifetime distribution. We heuristically test different
standard distribution forms for their ability to account for the observed disc fractions at certain ages. Here, weconcentrate on the distribution for low-mass stars (spectral type M3.7 - M6, Ms ≈ 0.1 - 0.24 Msun ) because disc
lifetimes depend on stellar mass. A Weibull-type distribution (k=1.78, λ=9.15) describes the observational data if allstars have a disc at a cluster age tc =0. However, a better match exists for lower initial disc fractions. For f(t=0)= 0.65,
a Weibull distribution (k=2.34, λ=11.22) and a Gauss distribution (σ=9.52, µ=9.52) fit similarly well the data. All
distributions have in common that they are wide, and most discs are dissipated at ages > 5 Myr. The next challenge
is to quantitatively link the diversity of disc lifetimes to the diversity in planets.

Ejection Patterns in the DG Tau Jet Over the Last 40 Years: Insights into Mass Accre77. tion Variability
Tae-Soo Pyo, Masahiko Hayashi, Michihiro Takami, Tracy L. Beck F We aim to clarify the link between massaccretion and ejection by analyzing DG Tau’s jet observations from optical and near-infrared data spanning 1984 to
2019, alongside photometric variations between 1983 and 2015. We classified 12 moving knot groups among 17 total
knot groups based on their constant proper motions and comparable radial velocities. A strong correlation emerges
between deprojected flow velocities of the knots and the photometric magnitudes of DG Tau. From 1983 to 1995, as
the deprojected ejection velocities surged from ∼ 273 ± 15 km s−1 to ∼ 427 ± 16 km s−1 , the photometric magnitudes(V ) concurrently brightened from 12.3 to 11.4. Notably, when DG Tau became brighter than 12.2 in the V band,its (B − V ) color shifted bluer than its intrinsic color range of K5 to M0. During this period, the launching pointof the jet in the protoplanetary disk moved closer to 0.06 AU from the star in 1995. Following a V magnitude dropfrom 11.7 to 13.4 in 1998, the star may have experienced significant extinction due to a dust wall created by the disk
wind during the ejection of the high-velocity knot in 1999. Since then, the magnitude became fainter than 12.2, the(B − V ) and (V − R) colors became redder, and the deprojected velocities consistently remained below 200 km s−1 .
The launching point of the jet then moved away to ∼ 0.45 AU by 2008. The prevailing factor influencing photometricmagnitude appears to be the active mass accretion causing the variable mass ejection velocities.

Deuterium fractionation in cold dense cores in the low-mass star forming region L1688
78. I. V. Petrashkevich, A. F. Punanova, P. Caselli, O. Sipilä, J. E. Pineda, R. K. Friesen, M. G. Korotaeva, A. I.
Vasyunin F In this work, we study deuterium fractionation in four starless cores in the low-mass star-forming region

L1688 in the Ophiuchus molecular cloud. We study how the deuterium fraction (RD ) changes with environment,
compare deuteration of ions and neutrals, core centre and its envelope, and attempt to reproduce the observed resultswith a gas-grain chemical model. We chose high and low gas density tracers to study both core centre and theenvelope. With the IRAM 30m antenna, we mapped N2 H+ (1-0), N2 D+ (1-0), H13 CO+ (1-0) and (2-1), DCO+ (2261), and p-NH2 D(111 -101 ) towards the chosen cores. The missing p-NH3 and N2 H+ (1-0) data were taken from theliterature. To measure the molecular hydrogen column density, dust and gas temperature within the cores, we usedthe Herschel/SPIRE dust continuum emission data, the GAS survey data (ammonia), and the COMPLETE survey
data to estimate the upper limit on CO depletion. We present the deuterium fraction maps for three species towards
four starless cores. Deuterium fraction of the core envelopes traced by DCO+ /H13 CO+ is one order of magnitude lower(∼0.08) than that of the core central parts traced by the nitrogen-bearing species (∼0.5). Deuterium fraction increases
with the gas density as indicated by high deuterium fraction of high gas density tracers and low deuterium fractionof lower gas density tracers and by the decrease of RD with core radii, consistent with the predictions of the chemical
model. Our model results show a good agreement with observations for RD (N2 D+ /N2 H+ ) and RD (DCO+ /HCO+ )and underestimate the RD (NH2 D/NH3 ).

79. On the incidence of episodic accretion in Class I YSOs from VVV

Carlos Contreras Peña, Philip W. Lucas, Zhen Guo, Leigh Smith F Episodic accretion is one of the competingmodels to explain the observed luminosity spread in young stellar clusters. These short-lived high accretion events
could also have a strong impact on planet formation. Observations of high-amplitude variability in young stellar
objects (YSOs) due to large changes in the accretion rate provide direct observational evidence for episodic accretion.
However, there are still uncertainties in the frequency of these events and if episodic accretion is universal among
YSOs. To determine the frequency of outbursts in Class I YSOs, we built a large and robust sample of objects at thisevolutionary stage, and searched for high-amplitude near-infrared (∆KS > 2 mag) variability in the VIRAC2 databaseof the Vista Variables in the Via Lactea (VVV) survey. By complementing with near-IR (2MASS and DENIS) andmid-IR (WISE/Neo-WISE) data, we find that from ∼ 7000 Class I YSOs, 97 objects can be classified as eruptive
variable YSOs. The duration of the outbursts vary from a few months to longer than 9 years, and cover a similar
range of amplitudes. Values of ∆KS > 5 mag, however, are only observed in outbursts with duration longer than 9
years. When considering different effects of completeness and contamination we estimate that the incidence of episodic
accretion in Class I YSOs is between 2% and 3%. Finally, we determine a recurrence timescale of long-term outbursts+1.12(a.k.a FUors) of τ = 1.75−0.87
kyr. The latter value agrees with previous estimates and is in line with the expectationsof higher frequency of FUor outbursts during younger stages of evolution.

80. Accretion and magnetism on young eccentric binaries: DQ Tau and AK Sco

Kim Pouilly, Axel Hahlin, Oleg Kochukhov, Julien Morin, Ágnes Kóspál F The accretion and ejection of massin pre-main sequence (PMS) stars are key processes in stellar evolution as they shape the stellar angular momentum
transport necessary for the stars’ stability. Magnetospheric accretion onto classical T Tauri stars and low-mass PMS
stars has been widely studied in the single-star case. This process can not be directly transferred to PMS binary
systems, as tidal and gravitation effects, and/or accretion from a circumbinary disc (with variable separation of thecomponents in the case of eccentric orbits) are in place. This work examines the accretion process of two PMS
eccentric binaries, DQ Tau and AK Sco, using high-resolution spectropolarimetric time series. We investigate howmagnetospheric accretion can be applied to these systems by studying the accretion-related emission lines and themagnetic field of each system. We discover that both systems are showing signs of magnetospheric accretion, despite
their slightly different configurations, and the weak magnetic field of AK Sco. Furthermore, the magnetic topology
of DQ Tau A shows a change relative to the previous orbital cycle studied: previously dominated by the poloidal
component, it is now dominated by the toroidal component. We also report an increase of the component’s accretionand the absence of an accretion burst at the apastron, suggesting that the component’s magnetic variation might be thecause of the inter-cycle variations of the system’s accretion. We conclude on the presence of magnetospheric accretionfor both systems, together with gravitational effects, especially for AK Sco, composed of more massive components.

81. A Radio Counterpart to a Jupiter-Mass Binary Object in Orion

Luis F. Rodriguez, Laurent Loinard, Luis A. Zapata F Using James Webb Space Telescope near-infrared data of

the inner Orion Nebula, Pearson & McCaughrean (2023) detected 40 Jupiter-Mass Binary Objects (JuMBOS). Thesesystems are not associated with stars and their components have masses of giant Jupiter-like planets and separations in
the plane of the sky of order ∼100 au. The existence of these wide free-floating planetary mass binaries was unexpectedin our current theories of star and planet formation. Here we report the radio continuum (6.1 and 10.0 GHz) Karl
G. Jansky Very Large Array detection of a counterpart to JuMBO 24. The radio emission appears to be steady at a27

level of ∼50 µJy over timescales of days and years. We set an upper limit of ' 15 km s−1 to the velocity of the radiosource in the plane of the sky. As in the near-infrared, the radio emission seems to be coming from both componentsof the binary.

Radio Continuum and Water Maser Observations of the High-Mass Protostar IRAS
82. 19035+0641 A
Tatiana M. Rodriguez, Emmanuel Momjian, Peter Hofner, Anuj P. Sarma, Esteban D. Araya F We present Very
Large Array (VLA) 1.3 cm continuum and 22.2 GHz H2 O maser observations of the high-mass protostellar object IRAS
19035+0641 A. Our observations unveil an elongated bipolar 1.3 cm continuum structure at scales . 500 au which,
together with a rising in-band spectral index, strongly suggests that the radio emission toward IRAS 19035+0641 A
arises from an ionized jet. In addition, eight individual water maser spots well aligned with the jet axis were identified.
The Stokes V spectrum of the brightest H2 O maser line (∼ 100 Jy) shows a possible Zeeman splitting and is well
represented by the derivatives of two Gaussian components fitted to the Stokes I profile. The measured Blos are
123 (±27) and 156 (±8) mG, translating to a pre-shock magnetic field of ≈ 7 mG. Subsequent observations to confirm
the Zeeman splitting showed intense variability in all the water maser spots, with the brightest maser completely
disappearing. The observed variability in a one-year time scale could be the result of an accretion event. Thesefindings strengthen our interpretation of IRAS 19035+0641 A as a high-mass protostar in an early accretion/outflow
evolutionary phase.

83. The dynamic centres of infrared-dark clouds and the formation of cores
Andrew J. Rigby, Nicolas Peretto, Michael Anderson, Sarah E. Ragan, Felix D. Priestley, Gary A. Fuller,
Mark A. Thompson, Alessio Traficante, Elizabeth J. Watkins, Gwenllian M. Williams F High-mass stars havean enormous influence on the evolution of the interstellar medium in galaxies, so it is important that we understandhow they form. We examine the central clumps within a sample of seven infrared-dark clouds (IRDCs) with a rangeof masses and morphologies. We use 1 pc-scale observations from NOEMA and the IRAM 30-m telescope to trace
dense cores with 2.8 mm continuum, and gas kinematics in C18 O, HCO+ , HNC, and N2 H+ (J=1−0). We supplement
our continuum sample with six IRDCs observed at 2.9 mm with ALMA, and examine the relationships between coreand clump-scale properties. We have developed a fully-automated multiple-velocity component hyperfine line-fittingcode called mwydyn which we employ to trace the dense gas kinematics in N2 H+ (1−0), revealing highly complex anddynamic clump interiors. We find that parsec-scale clump mass is the most important factor driving the evolution;
more massive clumps are able to concentrate more mass into their most massive cores - with a log-normally distributed
efficiency of around 9% - in addition to containing the most dynamic gas. Distributions of linewidths within the most
massive cores are similar to the ambient gas, suggesting that they are not dynamically decoupled, but are similarly
chaotic. A number of studies have previously suggested that clumps are globally collapsing; in such a scenario, theobserved kinematics of clump centres would be the direct result of gravity-driven mass inflows that become ever more
complex as the clumps evolve, which in turn leads to the chaotic mass growth of their core populations.

JWST Observations of Young protoStars (JOYS+): Detection of icy complex organic
84. molecules and ions. I. CH4 , SO2 , HCOO− , OCN− , H2 CO, HCOOH, CH3 CH2 OH,
CH3 CHO, CH3 OCHO, CH3 COOH
W. R. M. Rocha, E. F. van Dishoeck, M. E. Ressler, M. L. van Gelder, K. Slavicinska, N. G. C. Brunken, H.
Linnartz, T. P. Ray, H. Beuther, A. Caratti o Garatti, V. Geers, P. J. Kavanagh, P. D. Klaassen, K. Justannont,
Y. Chen, L. Francis, C. Gieser, G. Perotti, Ł. Tychoniec, M. Barsony, L. Majumdar, V. J. M. le Gouellec, L.
E. U. Chu, B. W. P. Lew, Th. Henning, G. Wright F Complex organic molecules (COMs) detected in the gas

phase are thought to be mostly formed on icy grains, but no unambiguous detection of icy COMs larger than CH3OH
has been reported so far. Exploring this matter in more detail has become possible with the JWST the critical 5-10
µm range. In the JOYS+ program, more than 30 protostars are being observed with the MIRI/MRS. This study
explores the COMs ice signatures in the low and high-mass protostar, IRAS 2A and IRAS 23385, respectively. We fit
continuum and silicate subtracted observational data with IR laboratory ice spectra. We use the ENIIGMA fitting
tool to find the best fit between the lab data and the observations and to performs statistical analysis of the solutions.
We report the best fits for the spectral ranges between 6.8 and 8.6 µm in IRAS 2A and IRAS 23385, originating from
simple molecules, COMs, and negative ions. The strongest feature in this range (7.7 µm) is dominated by CH4 and has

28contributions of SO2 and OCN-. Our results indicate that the 7.2 and 7.4 µm bands are mostly dominated by HCOO-.
We find statistically robust detections of COMs based on multiple bands, most notably CH3CHO, CH3CH2OH, andCH3OCHO. The likely detection of CH3COOH is also reported. The ice column density ratios between CH3CH2OH
and CH3CHO of IRAS 2A and IRAS 23385, suggests that these COMs are formed on icy grains. Finally, the derived
ice abundances for IRAS 2A correlate well with those in comet 67P/GC within a factor of 5. Based on the MIRI/MRS
data, we conclude that COMs are present in interstellar ices, thus providing additional proof for a solid-state origin of
these species in star-forming regions. The good correlation between the ice abundances in comet 67P and IRAS 2A isin line with the idea that cometary COMs can be inherited from the early protostellar phases.

85. 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< 10, 000 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.

The Giant Molecular Cloud G148.24+00.41: Gas Properties, Kinematics, and Cluster
86. Formation at the Nexus of Filamentary Flows
Vineet Rawat, M. R. Samal, D. L. Walker, D. K. Ojha, A. Tej, A. Zavagno, C. P. Zhang, Davide Elia, S. Dutta,
J. Jose, C. Eswaraiah, E. Sharma F Filamentary flows toward the centre of molecular clouds have been recognized

as a crucial process in the formation and evolution of stellar clusters. In this paper, we present a comprehensive
observational study that investigates the gas properties and kinematics of the Giant Molecular Cloud G148.24+00.41
using the observations of CO (1-0) isotopologues. We find that the cloud is massive (105 M ) and is one of the most
massive clouds of the outer Galaxy. We identified six likely velocity coherent filaments in the cloud having length,
width, and mass in the range of 14−38 pc, 2.5−4.2 pc, and (1.3−6.9) × 103 M , respectively. We find that thefilaments are converging towards the central area of the cloud, and the longitudinal accretion flows along the filaments
are in the range of ∼ 26−264 M Myr−1 . The cloud has fragmented into 7 clumps having mass in the range of ∼260−2100 M and average size around ∼ 1.4 pc, out of which the most massive clump is located at the hub of thefilamentary structures, near the geometric centre of the cloud. Three filaments are found to be directly connected tothe massive clump and transferring matter at a rate of ∼ 675 M Myr−1 . The clump hosts a near-infrared cluster.
Our results show that large-scale filamentary accretion flows towards the central region of the collapsing cloud is an
important mechanism for supplying the matter necessary to form the central high-mass clump and subsequent stellar
cluster.

87. 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 observation29

of 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.

88. Chemical differences among collapsing low-mass protostellar cores
Jingfei Sun, Xiaohu Li, Fujun Du, Yao Wang, Juan Tuo, Yanan Feng F Organic features lead to two distinct
types of Class 0/I low-mass protostars: hot corino sources, and warm carbon-chain chemistry (WCCC) sources.
Some observations suggest that the chemical variations between WCCC sources and hot corino sources are associatedwith local environments, as well as the luminosity of protostars. We conducted gas-grain chemical simulation incollapsing protostellar cores, and found that the fiducial model predicts abundant carbon-chain molecules and COMs,
and reproduces WCCC and hot corino chemistry in the hybrid source L483. By changing values of some physicalparameters, including the visual extinction of ambient clouds (Aamb
V ), the cosmic-ray ionization rate (ζ), the maximum
temperature during the warm-up phase (Tmax ), and the contraction timescale of protostars (tcont ), we found that UV
photons and cosmic rays can boost WCCC features by accelerating the dissociation of CO and CH4 molecules. On theother hand, UV photons can weaken the hot corino chemistry by photodissociation reactions, while the dependenceof hot corino chemistry on cosmic rays is relatively complex. The Tmax does not affect WCCC features, while it can
influence hot corino chemistry by changing the effective duration of two-body surface reactions for most COMs. Thelong tcont can boost WCCC and hot corino chemistry, by prolonging the effective duration of WCCC reactions in thegas phase and surface formation reactions for COMs, respectively. Subsequently, we ran a model with different physicalparameters to reproduce scarce COMs in prototypical WCCC sources. The scarcity of COMs in prototypical WCCC
sources can be explained by insufficient dust temperature in the inner envelopes to activate hot corino chemistry.
Meanwhile, the High ζ and the long tcont favors the explanation for scarce COMs in these sources.

89. ABYSS II: Identification of young stars in optical SDSS spectra and their properties
Serat Saad, Kaitlyn Lane, Marina Kounkel, Keivan G. Stassun, Ricardo López-Valdivia, Jinyoung Serena Kim,
Karla Peña Ramírez, Guy S. Stringfellow, Carlos G. Román-Zúñiga, Jesús Hernández, Scott J. Wolk, Lynne
A. Hillenbrand F We developed a tool that measures equivalent widths of various lines in low resolution optical

spectra, and it was applied to stellar spectra obtained as part of SDSS-V and LAMOST programs. These lines, suchas Li I which directly indicates stellar youth, or optical H I and Ca II which in emission indicate activity associatedwith stellar youth, are commonly seen in YSOs. We observe several notable differences in the properties of these lines
between YSOs and the field stars. Using these data, we devise a set of criteria through which it is possible to confirm
the youth of stars that have been observed by the ABYSS program, as well as to identify likely young stars that haveserendipitously been observed by other programs. We examine the decrement of H lines seen in emission in CTTSs,
and estimate the properties of the accretion stream that is responsible for the production of these lines. Finally, we
examine the evolution of Li I as a function of age, and characterize the scatter in its abundance that appears to be
intrinsic in young M dwarfs.

90. Formation of the Trappist-1 system in a dry protoplanetary disk

Antoine Schneeberger, Olivier Mousis, Magali Deleuil, Jonathan I. Lunine F A key feature of the Trappist-1
system is its monotonic decrease in bulk density with growing distance from the central star, which indicates an ice
mass fraction that is zero in the innermost planets, b and c, and about 10% in planets d through h. Previous studies
suggest that the density gradient of this system could be due to the growth of planets from icy planetesimals that
progressively lost their volatile content during their inward drift through the protoplanetary disk. Here we investigate
the alternative possibility that the planets formed in a dry protoplanetary disk populated with pebbles made ofphyllosilicates, a class of hydrated minerals with a water fraction possibly exceeding 10 wt%. We show that thedehydration of these minerals in the inner regions of the disk and the outward diffusion of the released vapor up to theice-line location allow the condensation of ice onto grains. Pebbles with water mass fractions consistent with those of30

planets d–h would have formed at the snow-line location. In contrast, planets b and c would have been accreted fromdrier material in regions closer to the star than the phyllosilicate dehydration line.
+
91. Large-Scale Mapping Observations of DCN and DCO toward Orion KL

Kotomi Taniguchi, Prathap Rayalacheruvu, Teppei Yonetsu, Tatsuya Takekoshi, Bunyo Hatsukade, Kotaro
Kohno, Tai Oshima, Yoichi Tamura, Yuki Yoshimura, Víctor Gómez-Rivera, Sergio Rojas-García, Arturo I.
Gómez-Ruiz, David H. Hughes, F. Peter Schloerb, Liton Majumdar, Masao Saito, Ryohei Kawabe F We present

emission maps (1.5’×1.5’ scale, corresponding to 0.18 pc) of the DCN (J = 2 − 1) and DCO+ (J = 2 − 1) lines in the
2 mm band toward the Orion KL region obtained with the 2 mm receiver system named B4R installed on the Large
Millimeter Telescope (LMT). The DCN emission shows a peak at the Orion KL hot core position, whereas no DCO+
emission has been detected there. The DCO+ emission shows enhancement at the west side of the hot core, which iswell shielded from the UV radiation from OB massive stars in the Trapezium cluster. We have derived the abundance
ratio of DCN/DCO+ at three representative positions where both species have been detected. The gas components
with VLSR ≈ 7.5 − 8.7 km/s are associated with low abundance ratios of ∼ 4 − 6, whereas much higher abundance
ratios (∼ 22 − 30) are derived for the gas components with VLSR ≈ 9.2 − 11.6 km/s. We have compared the observed
abundance ratio to our chemical models and found that the observed differences in the DCN/DCO+ abundance ratios
are explained by different densities.

Early Planet Formation in Embedded Disks (eDisk) XIV: Flared Dust Distribution and
92. Viscous Accretion Heating of the Disk around R CrA IRS 7B-a
Shigehisa Takakuwa, Kazuya Saigo, Miyu Kido, Nagayoshi Ohashi, John J. Tobin, Jes K. Jørgensen, Yuri
Aikawa, Yusuke Aso, Sacha Gavino, Ilseung Han, Patrick M. Koch, Woojin Kwon, Chang Won Lee, JeongEun Lee, Zhi-Yun Li, Zhe-Yu Daniel Lin, Leslie W. Looney, Shoji Mori, Jinshi Sai, Rajeeb Sharma, Patrick
Sheehan, Kengo Tomida, Jonathan P. Williams, Yoshihide Yamato, Hsi-Wei Yen F We performed radiativetransfer calculations and observing simulations to reproduce the 1.3-mm dust-continuum and C18 O (2-1) images in
the Class I protostar R CrA IRS7B-a, observed with the ALMA Large Program “Early Planet Formation in Embedded
Disks (eDisk)". We found that the dust disk model passively heated by the central protostar cannot reproduce theobserved peak brightness temperature of the 1.3-mm continuum emission (∼195 K), regardless of the assumptions
about the dust opacity. Our calculation suggests that viscous accretion heating in the disk is required to reproduce
the observed high brightness temperature. The observed intensity profile of the 1.3-mm dust-continuum emission
along the disk minor axis is skewed toward the disk far side. Our modeling reveals that such an asymmetric intensity
distribution requires flaring of the dust along the disk’s vertical direction with the scale-height following h/r ∼ r0.3 asfunction of radius. These results are in sharp contrast to those of Class II disks, which show geometrically flat dust
distributions and lower dust temperatures. From our modeling of the C18 O (2-1) emission, the outermost radius of thegas disk is estimated to be ∼80 au, larger than that of the dust disk (∼62 au), to reproduce the observed distributionof the C18 O (2-1) emission in IRS 7B-a. Our modeling unveils a hot and thick dust disk plus a larger gas disk around
one of the eDisk targets, which could be applicable to other protostellar sources in contrast to more evolved sources.

CD-27 11535: Evidence for a Triple System in the β Pictoris Moving Group
93. Andrew D. Thomas, Eric L. Nielsen, Robert J. De Rosa, Anne E. Peck, Bruce Macintosh, Jeffrey Chilcote,
Paul Kalas, Jason J. Wang, Sarah Blunt, Alexandra Greenbaum, Quinn M. Konopacky, Michael J. Ireland,Peter Tuthill, Kimberly Ward-Duong, Lea A. Hirsch, Ian Czekala, Franck Marchis, Christian Marois, Max A.
Millar-Blanchaer, William Roberson, Adam Smith, Hannah Gallamore, Jessica Klusmeyer F We present new

spatially resolved astrometry and photometry of the CD-27 11535 system, a member of the β Pictoris moving groupconsisting of two resolved K-type stars on a ∼20-year orbit. We fit an orbit to relative astrometry measured from
NIRC2, GPI, and archival NaCo images, in addition to literature measurements. However, the total mass inferred fromthis orbit is significantly discrepant from that inferred from stellar evolutionary models using the luminosity of the twostars. We explore two hypotheses that could explain this discrepant mass sum; a discrepant parallax measurementfrom Gaia due to variability, and the presence of an additional unresolved companion to one of the two components.
We find that the ∼20-year orbit could not bias the parallax measurement, but that variability of the components could
produce a large amplitude astrometric motion, an effect which cannot be quantified exactly without the individualGaia measurements. The discrepancy could also be explained by an additional star in the system. We jointly fit

31the astrometric and photometric measurements of the system to test different binary and triple architectures for thesystem. Depending on the set of evolutionary models used, we find an improved goodness of fit for a triple systemarchitecture that includes a low-mass (M = 0.177 ± 0.055 M ) companion to the primary star. Further studies of thissystem will be required in order to resolve this discrepancy, either by refining the parallax measurement with a more
complex treatment of variability-induced astrometric motion, or by detecting a third companion.

Formation of unipolar outflow and protostellar rocket effect in magnetized turbulent
94. molecular cloud cores
Daisuke Takaishi, Yusuke Tsukamoto, Miyu Kido, Shigehisa Takakuwa, Yoshiaki Misugi, Yuki Kudoh, Yasushi
Suto F Observed protostellar outflows exhibit a variety of asymmetrical features, including remarkable unipolar

outflows and bending outflows. Revealing the formation and early evolution of such asymmetrical protostellar outflows,
especially the unipolar outflows, is essential for a better understanding of the star and planet formation because they candramatically change the mass accretion and angular momentum transport to the protostars and protoplanetary disks.
Here, we perform the three-dimensional non-ideal magnetohydrodynamics simulations to investigate the formation andearly evolution of the asymmetrical protostellar outflows in magnetized turbulent isolated molecular cloud cores. We
find, for the first time to our knowledge, that the unipolar outflow forms even in the single low-mass protostellar system.
The results show that the unipolar outflow is driven in the weakly magnetized cloud cores with the dimensionless massto-flux ratios of µ = 8 and 16. Furthermore, we find the protostellar rocket effect of the unipolar outflow, which issimilar to the launch and propulsion of a rocket. The unipolar outflow ejects the protostellar system from the central
dense region to the outer region of the parent cloud core, and the ram pressure caused by its ejection suppresses thedriving of additional new outflows. In contrast, the bending bipolar outflow is driven in the moderately magnetizedcloud core with µ = 4. The ratio of the magnetic to turbulent energies of a parent cloud core may play a key role in
the formation of asymmetrical protostellar outflows.

95. Chondrule survivability in the solar nebula

Tetsuo Taki, Shigeru Wakita F The lifetime of mm size dust grains, such as chondrules, in the nominal solar nebulamodel is limited to ∼ 105 yr due to an inward drift driven by gas drag. However, isotopic and petrological studies
on primitive meteorites indicate a discrepancy of & 106 yr between the formation time of chondrules and that ofchondritic parent bodies. Therefore chondrules should survive for & 106 yr in the solar nebula against the inward
drift without subsequent growth (i.e., planetesimal formation). Here we investigate the conditions of the solar nebulathat are suitable for the long lifetime of chondrule-sized dust particles. We take the turbulent strength, the radialpressure gradient force, and the disk metallicity of the solar nebula as free parameters. For 1 mm-radius-chondrules
to survive and keep their size for & 106 yr, the suitable condition is a weak turbulence (α ∼ 10−6 ), a flat radial profile(η . 10−3 ), and a high metallicity (Z ∼ 0.1). This condition is qualitatively consistent with the characteristics ofprotoplanetary disks suggested by recent observations. We eventually propose that planetesimal formation may be
induced by the disk evolution, e.g., the inside-out dispersal of the gas component due to the disk wind.

Accuracy of ALMA estimates of young disk radii and masses. Predicted observations
96. from numerical simulations
Ngo-Duy Tung, Leonardo Testi, Ugo Lebreuilly, Patrick Hennebelle, Anaëlle Maury, Ralf S. Klessen, Luca
Cacciapuoti, Matthias González, Giovanni Rosotti, Sergio Molinari F Protoplanetary disks, which are the naturalconsequence of the gravitational collapse of the dense molecular cloud cores, host the formation of the known planetarysystems in our universe. Substantial efforts have been dedicated to investigating the properties of these disks in the
more mature Class II stage, either via numerical simulations of disk evolution from a limited range of initial conditions
or observations of their dust continuum and line emission from specific molecular tracers. The results coming from these
two standpoints have been used to draw comparisons. However, few studies have investigated the main limitations atwork when measuring the embedded Class 0/I disk properties from observations, especially in a statistical fashion. In
this study, we provide a first attempt to compare the accuracy of some critical disk parameters in Class 0/I systems, asderived on real ALMA observational data, with the corresponding physical parameters that can be directly defined bytheoreticians and modellers in numerical simulations. The approach we follow here is to provide full post-processing of
the numerical simulations and apply it to the synthetic observations the same techniques used by observers to derive
the physical parameters. We performed 3D Monte Carlo radiative transfer and mock interferometric observations of the32

disk populations formed in a magnetohydrodynamic (MHD) simulation model of disk formation through the collapseof massive clumps with the tools Radmc-3d and Casa, respectively, to obtain their synthetic observations. With
these observations, we re-employed the techniques commonly used in disk modelling from their continuum emissions
to infer the properties that would most likely be obtained with real interferometers. We then demonstrated how theseproperties may vary with respect to the gas kinematics analyses and dust continuum modelling.

An Extremely Young Protostellar Core, MMS 1/ OMC-3: Episodic Mass Ejection
97. History Traced by the Micro SiO Jet
Satoko Takahashi, Masahiro N. Machida, Mitsuki Omura, Doug Johnstone, Kazuya Saigo, Naoto Harada, Kohji
Tomisaka, Paul T. P. Ho, Luis A. Zapata, Steve Mairs, Gregory J. Herczeg, Kotomi Taniguchi, Yuhua Liu,
Asako Sato F We present ∼0.2 arcsec (∼80 au) resolution observations of the CO (2-1) and SiO (5-4) lines madewith the Atacama large millimeter/submillimeter array toward an extremely young intermediate-mass protostellar
source (tdyn <1000 years), MMS 1 located in the Orion Molecular Cloud-3 region. We have successfully imaged avery compact CO molecular outflow associated with MMS 1, having deprojected lobe sizes of ∼18000 au (red-shiftedlobe) and ∼35000 au (blue-shifted lobe). We have also detected an extremely compact (.1000 au) and collimated
SiO protostellar jet within the CO outflow. The maximum deprojected jet speed is measured to be as high as 93 km
s−1 . The SiO jet wiggles and displays a chain of knots. Our detection of the molecular outflow and jet is the first
direct evidence that MMS 1 already hosts a protostar. The position-velocity diagram obtained from the SiO emission
shows two distinct structures: (i) bow-shocks associated with the tips of the outflow, and (ii) a collimated jet, showing
the jet velocities linearly increasing with the distance from the driving source. Comparisons between the observations
and numerical simulations quantitatively share similarities such as multiple-mass ejection events within the jet andHubble-like flow associated with each mass ejection event. Finally, while there is a weak flux decline seen in the 850µm light curve obtained with JCMT/SCUBA 2 toward MMS 1, no dramatic flux change events are detected. Thissuggests that there has not been a clear burst event within the last 8 years.

Disentangling the association of PAH molecules with star formation : Insights from
98. JWST and UVIT
K. Ujjwal, Sreeja S Kartha, Akhil Krishna R, Blesson Mathew, Smitha Subramanian, Sudheesh T P, Robin
Thomas F Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous complex molecules in the interstellar medium

and are used as an indirect indicator of star-formation. On the other hand the ultraviolet (UV) emission from theyoung massive stars directly traces the star formation activity in a galaxy. The James Webb Space Telescope (JWST),
along with the UltraViolet Imaging Telescope (UVIT), opened up a new window of opportunity to make a better
understanding of the properties of the PAH molecules associated with the star-forming regions. In this study, weinvestigate how the resolved scale properties of PAH molecules in nearby galaxies are affected by star-formation. We
analyze the PAH features observed at 3.3, 7.7, and 11.3 µm using F335M, F770W, and F1130W images obtained from
JWST. Additionally, we utilize UVIT images to assess the star formation associated with these PAH emitting regions.
Our study focuses on three galaxies, namely NGC 628, NGC 1365, and NGC 7496, selected based on the availability ofboth JWST and UVIT images. Based on the resolved scale study on the PAH bright regions using JWST and UVIT
images, we found that the fraction of ionized PAH molecules is high in the star-forming regions with high ΣSFR. We
observed that emission from smaller PAH molecules is more in the star-forming regions with higher ΣSFR. Our study
suggests that the PAH molecules excited by the photons from SF regions with higher ΣSFR are dominantly smaller
and ionized molecules. UV photons from the star-forming regions could be the reason for a higher fraction of theionized PAHs. We suggest that the effect of high temperature in the star-forming regions and the formation of smaller
PAH molecules in the star-forming regions might also be resulting in the higher fraction of emission in the F335MPAH
band.

Dust growth and pebble formation in the initial stages of protoplanetary disk evolution
99. Eduard Vorobyov, Igor Kulikov, Vardan Elbakyan, James McKevitt, Manuel Guedel F Aims. The initial stagesof planet formation may start concurrently with the formation of a gas-dust protoplanetary disk. This makes the studyof the earliest stages of protoplanetary disk formation crucially important. Here we focus on dust growth and pebble
formation in a protoplanetary disk that is still accreting from a parental cloud core. Methods. We have developed
an original three-dimensional numerical hydrodynamics code, which computes the collapse of rotating clouds and33

disk formation on nested meshes using a novel hybrid Coarray Fortran-OpenMP approach for distributed and sharedmemory parallelization. Dust dynamics and growth are also included in the simulations. Results. We found that the
dust growth from ∼ 1 µm to 1-10 mm already occurs in the initial few thousand years of disk evolution but the Stokes
number hardly exceeds 0.1 because of higher disk densities and temperatures compared to the minimum mass Solar
nebular. The ratio of the dust-to-gas vertical scale heights remains rather modest, 0.2–0.5, which may be explained by
the perturbing action of spiral arms that develop in the disk soon after its formation. The dust-to-gas mass ratio in thedisk midplane is highly nonhomogeneous throughout the disk extent and is in general enhanced by a factor of several
compared to the fiducial 1:100 value. Low St hinders strong dust accumulation in the spiral arms compared to the restof the disk and the nonsteady nature of the spirals is also an obstacle. The spatial distribution of pebbles in the disk
midplane exhibits a highly nonhomogeneous and patchy character. The total mass of pebbles in the disk increases
with time and reaches a few tens of Earth masses after a few tens of thousand years of disk evolution. Abridged.

100. Circumstellar disk accretion across the Lagoon Nebula: the influence of environmentand stellar mass
L. Venuti, A. M. Cody, G. Beccari, L. M. Rebull, M. J. Irwin, A. Thanvantri, S. Thanvantri, S. H. P. Alencar,
C. O. Leal, G. Barentsen, J. E. Drew, S. B. Howell F Pre-main sequence disk accretion is pivotal in determining

the final stellar properties and the early conditions for close-in planets. We aim to establish the impact of internal(stellar mass) and external (radiation field) parameters on disk evolution in the Lagoon Nebula massive star-forming
region. We employ simultaneous u, g, r, i, Hα time series photometry, archival infrared data, and high-precision K2
light curves, to derive stellar, disk, and accretion properties for 1012 Lagoon Nebula members. Of all young stars
in the Lagoon Nebula, we estimate 34% − 37% have inner disks traceable down to ∼ 12 µm, while 38% − 41% areactively accreting. We detect disks ∼1.5 times more frequently around G/K/M stars than higher-mass stars, whichappear to deplete their inner disks on shorter timescales. We find tentative evidence for faster disk evolution in thecentral regions of the Lagoon Nebula, where the bulk of the O/B population is located. Conversely, disks appear tolast longer at its outskirts, where the measured fraction of disk-bearing stars tends to exceed those of accreting anddisk-free stars. The derived mass accretion rates show a non-uniform dependence on stellar mass between ∼ 0.2 − 5
M . In addition, the typical accretion rates appear to differ across the Lagoon Nebula extension, with values twotimes lower in the core region than at its periphery. Finally, we detect tentative density gradients in the accretion
shocks, with lags in the appearance of brightness features as a function of wavelength that can amount to ∼ 7% − 30%of the rotation period.

101. Mid-infrared evidence for iron-rich dust in the multi-ringed inner disk of HD 144432

J. Varga, MATISSE, GRAVITY Collaborations F Context. Rocky planets form by the concentration of solid

particles in the inner few au regions of planet-forming disks. Their chemical composition reflects the materials in thedisk available in the solid phase at the time the planets were forming. Aims. We aim to constrain the structure anddust composition of the inner disk of the young star HD 144432, using an extensive set of infrared interferometricdata taken by the Very Large Telescope Interferometer (VLTI), combining PIONIER, GRAVITY, and MATISSE
observations. Methods. We introduced a new physical disk model, TGMdust, to image the interferometric data, andto fit the disk structure and dust composition. We also performed equilibrium condensation calculations with GGchem.
Results. Our best-fit model has three disk zones with ring-like structures at 0.15, 1.3, and 4.1 au. Assuming that thedark regions in the disk at 0.9 au and at 3 au are gaps opened by planets, we estimate the masses of the putative
gap-opening planets to be around a Jupiter mass. We find evidence for an optically thin emission (τ < 0.4) from theinner two disk zones (r < 4 au) at λ > 3 µm. Our silicate compositional fits confirm radial mineralogy gradients.
To identify the dust component responsible for the infrared continuum emission, we explore two cases for the dust
composition, one with a silicate+iron mixture and the other with a silicate+carbon one. We find that the iron-richmodel provides a better fit to the spectral energy distribution. Conclusions. We propose that in the warm inner regions(r < 5 au) of typical planet-forming disks, most if not all carbon is in the gas phase, while iron and iron sulfide grains
are major constituents of the solid mixture along with forsterite and enstatite. Our analysis demonstrates the needfor detailed studies of the dust in inner disks with new mid-infrared instruments such as MATISSE and JWST/MIRI.

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The 3D Kinematics of the Orion Nebula Cluster II: Mass-dependent Kinematics of the102. 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.

Dust Dynamics in Hall-effected Protoplanetary Disks. I. Background Drift Hall Insta103. bility
Yinhao Wu, Min-Kai Lin, Can Cui, Leonardo Krapp, Yueh-Ning Lee, Andrew N. Youdin F Recent studies
have shown that the large-scale gas dynamics of protoplanetary disks (PPDs) are controlled by non-ideal magnetohydrodynamics (MHD), but how this influences dust dynamics is not fully understood. To this end, we investigate
the stability of dusty, magnetized disks subject to the Hall effect, which applies to planet-forming regions of PPDs.
We find a novel Background Drift Hall Instability (BDHI) that may facilitate planetesimal formation in Hall-effecteddisk regions. Through a combination of linear analysis and nonlinear simulations, we demonstrate the viability andcharacteristics of BDHI. We find it can potentially dominate over the classical streaming instability (SI) and standard
MHD instabilities at low dust-to-gas ratios and weak magnetic fields. We also identify magnetized versions of the classic SI, but these are usually subdominant. We highlight the complex interplay between magnetic fields and dust-gas
dynamics in PPDs, underscoring the need to consider non-ideal MHD like the Hall effect in the broader narrative ofplanet formation.

Star-forming environments in smoothed particle magnetohydrodynamics simulations II:
104. Re-simulating isolated clumps to determine equivalence of extracted clumps and parent
simulations
James Wurster, Connar Rowan F What is the numerical reproducibility of a stellar system (including its discs)
when evolving only a sub-set of (partially-evolved) smoothed particle hydrodynamics (SPH) particles? To investigate this, we modelled the evolution of 29 star forming clumps that were extracted from our previous simulations
that investigated the formation and early evolution of low-mass star clusters. These clumps were evolved using athree-dimensional smoothed particle radiation magnetohydrodynamics code, where we included or excluded non-ideal
magnetohydrodynamics to match the cluster simulation. While star formation proceeded as expected, we were unable
to identically reproduce any of the systems present at the end of the cluster simulations. However, the final distributions of stellar mass, stellar system mass, disc mass, and disc radii were reproduced statistically; unfortunately, thedistribution of average magnetic field strengths in the discs was not reproduced statistically, but this may be a resultof our updated algorithms governing the evolution of the magnetic field. Therefore, given that our clumps yield stellar
masses that are statistically similar to those in the original low-mass star clusters, we have demonstrated that we
can statistically reproduce systems (aside from their magnetic field strength) by evolving a subset of SPH particles.
Therefore, clumps such as these can be used as initial conditions to investigate the formation of isolated stars fromless-contrived initial environments.

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On the Scarcity of Dense Cores (n > 105 cm−3 ) in High Latitude Planck Galactic Cold105. Clumps
Fengwei Xu et al. F High-latitude (|b| > 30◦ ) molecular clouds have virial parameters that exceed 1, but whether

these clouds can form stars has not been studied systematically. Using JCMT SCUBA-2 archival data, we surveyed
70 fields that target high-latitude Planck galactic cold clumps (HLPCs) to find dense cores with density of 105 -106cm−3 and size of < 0.1 pc. The sample benefits from both the representativeness of the parent sample and covering
densest clumps at the high column density end (> 1 × 1021 cm−2 ). At an average noise rms of 15 mJy/beam, we
detected Galactic dense cores in only one field, G6.04+36.77 (L183), while also identifying 12 extragalactic objects
and two young stellar objects. Compared to the low-latitude clumps, dense cores are scarce in HLPCs. With synthetic
observations, the densities of cores are constrained to be nc . 105 cm−3 , should they exist in HLPCs. Low-latitude
clumps, Taurus clumps, and HLPCs form a sequence where a higher virial parameter corresponds to a lower dense
core detection rate. If HLPCs were affected by the Local Bubble, the scarcity should favor turbulence-inhibited rather
than supernova-driven star formation. Studies of the formation mechanism of the L183 molecular cloud are warranted.

106. Insights into the first and second hydrostatic core stages from numerical simulations

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 thewarm, 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
107. (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.

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Near-Ultraviolet Radiation toward Molecular Cloud N4 in W 50/SS 433: Evidence for108. Direct Interaction of the Jet with Molecular Cloud
H. Yamamoto, T. Ishikawa, T. T. Takeuchi F We compared the molecular clouds in the western part of SS 433 withnear-ultraviolet radiation data obtained from GALEX. Near-ultraviolet radiation is prominently confirmed toward only
N4, while no near-ultraviolet radiation is detected toward N1, N2, and N3. The radiative region of near-ultraviolet
radiation is nearly the same as the CO-emitting region in N4, and does not extend beyond the jet seen in X-ray
radiation. Near-ultraviolet radiation cannot be explained solely by broadband continuous radiation and may originate
from line emissions. The intensity of near-ultraviolet radiation exhibits an anti-correlation with that of 13CO(J=3-2)
emission. This anti-correlation, along with strong far-infrared radiation in the region with weaker near-ultraviolet
radiation intensity compared to its surroundings, suggests that near-ultraviolet radiation originates from behind themolecular cloud, heating up the interstellar dust in N4. Subsequently, the dust in N4 re-radiates in the far-infrared
band. In the same region, a high peak TM B ratio of 12CO(J=3-2)/12CO(J=1-0) of 0.9, and a high kinetic temperatureof Tk 56 K in the molecular cloud indicate that CO molecules are highly excited, and the molecular cloud is heatedthrough photoelectric heating. This heating results from electrons released due to the photoelectric effect caused by
the phenomenon where interstellar dust absorbs near-ultraviolet radiation. In terms of the timescale of near-ultraviolet
radiation originating from line emissions, near-ultraviolet radiation towards N4 cannot be explained by the shock of
the blast wave from a supernova that created W 50. These findings also suggest that N4 directly interacts with thejet from SS 433. As a result of this direct interaction, near-ultraviolet radiation is emitted from an interacting layer
between the jet and N4.

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