The Star Formation Newsletter
A community newsletter on Star and Planet Formation research
No. 350 — 27 February 2022
Editor: João Alveswww.starformation.news

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Cover image caption
The Taurus Molecular Cloud as seen by ESA’s Herschel observatory. Together with Ophiuchus, these are the closest molecular
cloud complexes to Earth (distance 140 pc), found at the opposite sides of the Local Bubble. The resolution of the image isaround 5000 au. The red hue represents denser, colder gas (T ∼10 K), while the blue hue represents more diffuse, warmer gas (T∼15 K). Many benchmark objects in (low-mass) star formation, like young stellar objects, circumstellar disks, jets, outflows, aswell as filaments and dense cores, are part of this region. This four-color image combines Herschel observations at 160 microns(blue), 250 microns (green), 350 microns (split between green and red), and 500 microns (red). Credit: ESA/Herschel. Color
composite by R. Hurt.
Note from the Editor
The Star Formation Newsletter is now on the web at www.starformation.news. This PDF file contains the monthly Abstracts
and links to the different Newsletter sections. Red text in this PDF is a url link. Submitting an abstract to the SFN is as simple
as entering the arXiv ID (e.g., 2006.10139) in a web form on the SFN web site. Do not remove the LATEX formatting
when submitting to the arXiv. If you do, your abstract will not look great either at the arXiv or the SFN.

Abstracts
1. The sharp ALMA view of infall and outflow in the massive protocluster G31.41+0.31

M. T. Beltrán, V. M. Rivilla, R. Cesaroni, D. Galli, L. Moscadelli, A. Ahmadi, H. Beuther, S. Etoka, C. Goddi,
P. D. Klaassen, R. Kuiper, M. S. N. Kumar, A. Lorenzani, T. Peters, Á. Sánchez-Monge, P. Schilke, F. van derTak, S. Vig F Context. To better understand the formation of high-mass stars, it is fundamental to investigate how matteraccretes onto young massive stars, how it is ejected, and how all this differs from the low-mass case. The massive protocluster
G31.41+0.31 is the ideal target to study all these processes because observations at millimeter and centimeter wavelengths
have resolved the emission of the Main core into at least four massive dust continuum sources, named A, B, C, and D, within
1" or 0.018 pc, and have identified signatures of infall and several outflows associated with the core. Aims. We study theinterplay between infall and outflow in G31.41+0.31 by investigating at a spatial resolution of a few 100 au their properties andtheir possible impact on the core. Methods. We carried out molecular line observations of typical high-density tracers, such as
CH3CN or H2CO, and shock and outflow tracers, such as SiO, with ALMA at 1.4 mm that achieved an angular resolution of
0.09" (340 au). Results. The observations have revealed inverse P-Cygni profiles in CH3CN and H2CO toward the four sources
embedded in the Main core, suggesting that all of them are undergoing collapse. The infall rates, estimated from the red-shifted
absorption are on the order of 1E-2 Msun/yr. The individual infall rates imply that the accretion timescale of the Main core isan order of magnitude smaller than its rotation timescale. This confirms that rotating toroids such as the G31 Main core are
non-equilibrium, transient collapsing structures that need to be constantly replenished with fresh material from a large-scale
reservoir. For sources B, C, and D, the infall could be accelerating inside the sources, while for source A, the presence of asecond emission component complicates the interpretation.

2. Gravity or turbulence V: Star forming regions undergoing violent relaxation

Andrea Bonilla-Barroso, J. Ballesteros-Paredes, Jesus Hernández, Luis Aguilar, Manuel Zamora, Lee W. Hartmann, Aleksandra Kuznetsova, Vianey Camacho, Verónica Lora F Using numerical simulations of the formation and2evolution of stellar clusters within molecular clouds, we show that the stars in clusters formed within collapsing molecular cloud
clumps exhibit a constant velocity dispersion regardless of their mass, as expected in a violent relaxation processes. In contrast,
clusters formed in turbulence-dominated environments exhibit an inverse mass segregated velocity dispersion, where massive
stars exhibit larger velocity dispersions than low-mass cores, consistent with massive stars formed in massive clumps, which inturn, are formed through strong shocks. We furthermore use Gaia EDR3 to show that the stars in the Orion Nebula Cluster
exhibit a constant velocity dispersion as a function of mass, suggesting that it has been formed by collapse within one free-falltime of its parental cloud, rather than in a turbulence-dominated environment during many free-fall times of a supported cloud.
Additionally, we have addressed several of the criticisms of models of collapsing star forming regions: namely, the age spreadof the ONC, the comparison of the ages of the stars to the free-fall time of the gas that formed it, the star formation efficiency,
and the mass densities of clouds vs the mass densities of stellar clusters, showing that observational and numerical data areconsistent with clusters forming in clouds undergoing a process of global, hierarchical and chaotic collapse, rather than been
supported by turbulence.

disk rings and winds in CO at 0.01-10 au: a high-resolution M -band spec3. Scanning
troscopy survey with IRTF-iSHELL
Andrea Banzatti, Kirsten M. Abernathy, Sean Brittain, Arthur D. Bosman, Klaus M. Pontoppidan, Adwin
Boogert, Stanley Jensen, John Carr, Joan Najita, Sierra Grant, Rocio M. Sigler, Michael A. Sanchez, Joshua
Kern, John T. Rayner F We present an overview and first results from a M -band spectroscopic survey of planet-forming
disks performed with iSHELL on IRTF, using two slits that provide resolving power R ≈ 60,000-92,000 (5-3.3 km/s). iSHELL
provides a nearly complete coverage at 4.52-5.24 µm in one shot, covering > 50 lines from the R and P branches of 12 CO and13
CO for each of multiple vibrational levels, and providing unprecedented information on the excitation of multiple emission
and absorption components. Some of the most notable new findings of this survey are: 1) the detection of two CO Keplerianrings at < 2 au (in HD 259431), 2) the detection of H2 O ro-vibrational lines at 5 µm (in AS 205 N), and 3) the common kinematic variability of CO lines over timescales of 1-14 years. By homogeneously analyzing this survey together with a previous
VLT-CRIRES survey of cooler stars, we discuss a unified view of CO spectra where emission and absorption components scan
the disk surface across radii from a dust-free region within dust sublimation out to ≈ 10 au. We classify two fundamental typesof CO line shapes interpreted as emission from Keplerian rings (double-peak lines) and a disk surface plus a low-velocity part ofa wind (triangular lines), where CO excitation reflects different emitting regions (and their gas-to-dust ratio) rather than justthe irradiation spectrum. A disk+wind interpretation for the triangular lines naturally explains several properties observed in
CO spectra, including the line blue-shifts, line shapes that turn into narrow absorption at high inclinations, and the frequency
of disk winds as a function of stellar type.
3 CN deuteration in the SVS13-A Class I hot-corino. SOLIS XV
4. CH
Eleonora Bianchi, Cecilia Ceccarelli, Claudio Codella, Ana López-Sepulcre, Satoshi Yamamoto, Nadia Balucani,

Paola Caselli, Linda Podio, Roberto Neri, Rafael Bachiller, Cécile Favre, Francesco Fontani, Bertrand Lefloch,
Nami Sakai, Dominique Segura-Cox F We studied the line emission from CH3CN and its deuterated isotopologue CH2 DCN
towards the prototypical Class I object SVS13-A, where the deuteration of a large number of species has already been reported.
Our goal is to measure the CH3 CN deuteration in a Class I protostar, for the first time, in order to constrain the CH3 CN
formation pathways and the chemical evolution from the early prestellar core and Class 0 to the evolved Class I stages. We
imaged CH2DCN towards SVS13-A using the IRAM NOEMA interferometer at 3mm in the context of the Large Program SOLIS(with a spatial resolution of 1.8"x1.2"). The NOEMA images have been complemented by the CH3 CN and CH2 DCN spectracollected by the IRAM-30m Large Program ASAI, that provided an unbiased spectral survey at 3mm, 2mm, and 1.3mm. The
observed line emission has been analysed using LTE and non-LTE LVG approaches. The NOEMA/SOLIS images of CH2DCN
show that this species emits in an unresolved area centered towards the SVS13-A continuum emission peak, suggesting thatmethyl cyanide and its isotopologues are associated with the hot corino of SVS13-A, previously imaged via other iCOMs. In
addition, we detected 41 and 11 ASAI transitions of CH3 CN and CH2DCN, respectively, which cover upper level energies (Eup)from 13 to 442 K and from 18 K to 200 K, respectively. The derived [CH2DCN]/[CH3CN] ratio is ∼9%. This value is consistent
with those measured towards prestellar cores and a factor 2-3 higher than those measured in Class 0 protostars. Contrarily
to what expected for other molecular species, the CH3CN deuteration does not show a decrease in SVS13-A with respect tomeasurements in younger prestellar cores and Class 0 protostars. Finally, we discuss why our new results suggest that CH3CN
was likely synthesised via gas-phase reactions and frozen onto the dust grain mantles during the cold prestellar phase.

5. Deuterium fractionation as a multi-phase component tracer in the Galactic Centre
L. Colzi, J. Martín-Pintado, V. M. Rivilla, I. Jiménez-Serra, S. Zeng, L. F. Rodríguez-Almeida, F. Rico-Villas,
S. Martín, M. A. Requena-Torres F The Central Molecular Zone (CMZ) contains most of the mass of our Galaxy but its
star formation rate is one order of magnitude lower than in the Galactic disc. This is likely related to the fact that the bulkof the gas in the CMZ is in a warm (>100 K) and turbulent phase with little material in the pre-stellar phase. We present in3

this Letter observations of deuterium fractionation (D/H ratios) of HCN, HNC, HCO+ , and N2 H+ towards the CMZ molecular
cloud G+0.693-0.027. These observations clearly show, for the first time, the presence of a colder, denser, and less turbulent
narrow component, with a line width of ∼9 km s−1 , in addition to the warm, less dense and turbulent broad component with aline width of ∼20 km s−1 . The very low D/H ratio ≤6×10−5 for HCO+ and N2 H+ , close to the cosmic value (∼2.5×10−5 ), andthe high D/H ratios >4×10−4 for HCN and HNC derived for the broad component, confirm the presence of high-temperatures
deuteration routes for nitriles. For the narrow component we have derived D/H ratios >10−4 and excitation temperatures of 7 K
for all molecules, suggesting kinetic temperatures ≤30 K and H2 densities ≥5×104 cm−3 , at least one order of magnitude larger
than for the broad component. The method presented in this Letter allows to identify clouds on the verge of star formation, i.e.
under pre-stellar conditions, towards the CMZ. This method can also be used for the identification of such clouds in external
galaxies.

the Protostellar Luminosity Function in Cygnus-X with SOFIA/FORCAST
6. Completing
Imaging
Yingjie Cheng, Robert A. Gutermuth, Stella Offner, Mark Hemeon-Heyer, Hans Zinnecker, S. Thomas Megeath,
Riwaj Pokhrel F We present a new SOFIA/FORCAST mid-IR survey of luminous protostars and crowded star-forming environments in Cygnus X, the nearest million-solar mass molecular cloud complex. We derive bolometric luminosities for over 1000
sources in the region with these new data in combination with extant Spitzer and UKIDSS photometry, with 63 new luminous
protostar candidates identified by way of the high quality SOFIA/FORCAST data. By including FORCAST data, we constructprotostellar luminosity functions (PLFs) with improved completeness at the high luminosity end. The PLFs are well describedby a power law function with an index of -0.5. Based on the Herschel temperature and column density measurements, we findno obvious dependence of the PLFs on the local gas temperature, but PLFs in regions of high stellar density or gas column
density exhibit some excess at higher luminosities. Through the comparison between our observed PLFs and existing accretion
models, both the turbulent core (TC) and the competitive accretion (CA) models are consistent with our results, while theisothermal sphere (IS) model is disfavored. The implications of these results on the star formation process are discussed.

7. ALMA’s view of the M-dwarf GSC 07396-00759’s edge-on debris disc: AU Mic’s coeval
twin

Patrick F. Cronin-Coltsmann, Grant M. Kennedy, Christian Adam, Quentin Kral, Jean-François Lestrade,
Sebastian Marino, Luca Matrà, Simon J. Murphy, Johan Olofsson, Mark C. Wyatt F We present new ALMA Band
7 observations of the edge-on debris disc around the M1V star GSC 07396-00759. At 20 Myr old and in the beta Pictoris
Moving Group along with AU Mic, GSC 07396-00759 joins it in the handful of low mass M-dwarf discs to be resolved in the
sub-mm. With previous VLT/SPHERE scattered light observations we present a multi-wavelength view of the dust distribution
within the system under the effects of stellar wind forces. We find the mm dust grains to be well described by a Gaussian
torus at 70 au with a FWHM of 48 au and we do not detect the presence of CO in the system. Our ALMA model radius
is significantly smaller than the radius derived from polarimetric scattered light observations, implying complex behaviour inthe scattering phase function. The brightness asymmetry in the disc observed in scattered light is not recovered in the ALMA
observations, implying that the physical mechanism only affects smaller grain sizes. High resolution follow-up observations of
the system would allow investigation into its unique dust features as well as provide a true coeval comparison for its smaller
sibling AU Mic, singularly well observed amongst M-dwarfs systems.

Scattering and sublimation: a multi-scale view of µm-sized dust in the inclined disc of

8. HD 145718

Claire L. Davies, Evan A. Rich, Tim J. Harries, John D. Monnier, Anna S. E. Laws, Sean M. Andrews, Jaehan
Bae, David J. Wilner, Narsireddy Anugu, Jacob Ennis, Tyler Gardner, Stefan Kraus, Aaron Labdon, JeanBaptiste le Bouquin, Cyprien Lanthermann, Gail H. Schaefer, Benjamin R. Setterholm, Theo ten Brummelaar
F We present multi-instrument observations of the disc around the Herbig Ae star, HD 145718, employing geometric and Monte
Carlo radiative transfer models to explore the disc orientation, the vertical and radial extent of the near infrared (NIR) scattering
surface, and the properties of the dust in the disc surface and sublimation rim. The disc appears inclined at 67 − 71◦ , withposition angle, PA = −1.0 − 0.6◦ , consistent with previous estimates. The NIR scattering surface extends out to ∼ 75 au and weinfer an aspect ratio, hscat (r)/r ∼ 0.24 in J-band; ∼ 0.22 in H-band. Our GPI images and VLTI+CHARA NIR interferometry
suggest that the disc surface layers are populated by grains & λ/2π in size, indicating these grains are aerodynamically supported
against settling and/or the density of smaller grains is relatively low. We demonstrate that our geometric analysis provides areasonable assessment of the height of the NIR scattering surface at the outer edge of the disc and, if the inclination can be
independently constrained, has the potential to probe the flaring exponent of the scattering surface in similarly inclined (i & 70◦ )discs. In re-evaluating HD 145718’s stellar properties, we found that the object’s dimming events - previously characterised as
UX Or and dipper variability - are consistent with dust occultation by grains larger, on average, than found in the ISM. Thisocculting dust likely originates close to the inferred dust sublimation radius at 0.17 au.

4

9. Do the majority of stars form as gravitationally unbound?
František Dinnbier, Pavel Kroupa, Richard I. Anderson F Some of the youngest stars (age . 10 Myr) are clustered,
while many others are observed scattered throughout star forming regions or in complete isolation. It has been intensively
debated whether the scattered or isolated stars originate in star clusters, or if they form truly isolated, which could help
constrain the possibilities how massive stars are formed. We adopt the assumption that all stars form in gravitationally boundstar clusters embedded in molecular cloud cores (Γ-1 model), which expel their natal gas, and compare the fraction of stars
found in clusters with observational data. The star clusters are modelled by the code nbody6, which includes stellar andcircumbinary evolution, gas expulsion, and the external gravitational field of their host galaxy. We find that small changes in
the assumptions in the current theoretical model estimating the fraction, Γ, of stars forming in embedded clusters have a large
influence on the results, and we present a counterexample as an illustration. This calls into question theoretical arguments
about Γ in embedded clusters, and it suggests that there is no firm theoretical ground for low Γ in galaxies with lower starformation rates (SFRs). Instead, the assumption that all stars form in embedded clusters is in agreement with observational
data for the youngest stars (age . 10 Myr). In the Γ-1 scenario, the observed fraction of the youngest stars in clusters increases
with the SFR only weakly; the increase is caused by the presence of more massive clusters in galaxies with higher SFRs, which
release fewer stars to the field in proportion to their mass. The Γ-1 model yields a higher fraction of stars in clusters for older
stars (age between 10 and 300 Myr) than what is observed. This discrepancy can be caused by interactions with molecular
clouds.

Successive deuteration in low-mass star-forming regions: the case of D2 -methanol

10. (CHD2 OH) in IRAS 16293-2422

Maria N. Drozdovskaya, Laurent H. Coudert, Laurent Margulès, Audrey Coutens, Jes K. Jørgensen, SébastienManigand F Accurate quantification of the column density of di-deuterated methanol is a key missing puzzle piece in theotherwise thoroughly constrained family of D-bearing methanol in the deeply embedded low-mass protostellar system andastrochemical template source IRAS16293-2422. A spectroscopic dataset for astrophysical purposes is built for CHD2 OH andmade publicly available to facilitate accurate characterization of this species in astrochemical surveys. The newly computed line
list and partition function are used to search for CHD2 OH towards IRAS16293-2422 A and B in data from ALMA-PILS. Only
non-blended, optically thin lines of CHD2 OH are used for the synthetic spectral fitting. The constructed spectroscopic database
contains line frequencies and strengths for 7417 transitions in the 0 to 500 GHz frequency range. ALMA-PILS observations in
the 329-363 GHz range are used to identify 105 unique, non-blended, optically thin line frequencies of CHD2 OH for synthetic
spectral fitting. The derived excitation temperatures and column densities yield high D/H ratios of CHD2 OH in IRAS 162932422 A and B of 7.5±1.1not higher than in other low-mass star-forming regions. Di-deuterated molecules consistently have higher
D/H ratios than their monodeuterated counterparts in all low-mass protostars, which may be a natural consequence of H-D
substitution reactions as seen in laboratory experiments. The Solar System’s natal cloud, as traced by comet 67P/ChuryumovGerasimenko, may have had a lower initial abundance of D, been warmer than the cloud of IRAS16293-2422, or been partially
reprocessed. In combination with accurate spectroscopy, a careful spectral analysis, and a consideration of the underlying
assumptions, successive deuteration is a robust window on the physicochemical provenance of star-forming systems.

11. The impact of cosmic-ray attenuation on the carbon cycle emission in molecular clouds

Brandt A. L. Gaches, Thomas G. Bisbas, Shmuel Bialy F Observations of the emission of the carbon cycle species (C,C+ CO) are commonly used to diagnose gas properties in the interstellar medium but are significantly sensitive to the cosmic-ray
ionization rate. The carbon-cycle chemistry is known to be quite sensitive to the cosmic-ray ionization rate, ζ, controlled by
the flux of low-energy cosmic rays which get attenuated through molecular clouds. However, astrochemical models commonly
assume a constant cosmic-ray ionization rate in the clouds. We investigate the effect of cosmic-ray attenuation on the emission ofcarbon cycle species from molecular clouds, in particular the [CII] 158 µm, [CI] 609 µm and CO (J = 1 - 0) 115.27 GHz lines. We
use a post-processed chemical model of diffuse and dense simulated molecular clouds and quantify the variation in both column
densities and velocity integrated line emission of the carbon cycle with different cosmic-ray ionization rate models. We findthat the abundances and column densities of carbon cycle species is significantly impacted by the chosen cosmic-ray ionization
rate model: no single constant ionization rate can reproduce the abundances modelled with an attenuated cosmic-ray model.
Further, we show that constant ionization rate models fail to simultaneously reproduce the integrated emission of the lines weconsider, and their deviations from a physically derived cosmic-ray attenuation model is too complex to be simply corrected.
We demonstrate that the two clouds we model exhibit a similar average AV,eff – nH relationship, resulting in an averagerelation between the cosmic-ray ionization rate and density ζ(nH ). We conclude by providing a number of implementation
recommendations for CRs in astrochemical models, but emphasize the necessity for column-dependent cosmic-ray ionization
rate prescriptions.

5Importance of source structure on complex organics emission. I. Observations of CH3 OH
12. from
low-mass to high-mass protostars
M. L. van Gelder, P. Nazari, B. Tabone, A. Ahmadi, E. F. van Dishoeck, M. T. Beltrán, G. A. Fuller, N. Sakai,
Á. Sánchez-Monge, P. Schilke, Y. -L. Yang, Y. Zhang F Complex organic molecules (COMs) are often observed towardembedded Class 0 and I protostars. However, not all Class 0 and I protostars exhibit COMs emission. In this work, variations
in methanol (CH3 OH) emission are studied to test if absence of CH3 OH emission can be linked to source properties. Combining
both new and archival observations with ALMA and sources from the literature, a sample of 184 low-mass and high-mass
protostars is investigated. The warm (T > 100 K) gaseous CH3 OH mass, MCH3 OH , is determined for each source using primarily
optically thin isotopologues. On average, Class I protostellar systems seem to have less warm MCH3 OH (< 10−10 M ) than
younger Class 0 sources (∼ 10−7 M ). High-mass sources in our sample show higher warm MCH3 OH up to 10−7 − 10−3 M . To
take into account the effect of the source’s overall mass on MCH3 OH , a normalized CH3 OH mass is defined as MCH3 OH /Mdust,0 ,where Mdust,0 is the cold + warm dust mass within a fixed radius. Excluding upper limits, a simple power-law fit to thenormalized warm CH3 OH masses results in MCH3 OH /Mdust,0 ∝ L0.71±0.05. This is in good agreement with a simple hot corebol
toy model which predicts that the normalized MCH3 OH increases with L0.75
bol due to the snowline moving outward. Sources forwhich the size of the disk is equivalent or smaller than the estimated 100 K radius agree well with the best-fit power-law model,
whereas sources with significantly larger disks show up to two orders of magnitude lower normalized warm CH3 OH masses.
Based on the latter results, we suggest that source structure such as a disk can result in colder gas and thus fewer COMs in thegas phase. Additionally, optically thick dust can hide the emission of COMs.

A new planet candidate detected in a dust gap of the disc around HD 163296 through13. localised kinematic signatures. An observational validation of the Discminer

Andres F. Izquierdo, Stefano Facchini, Giovanni P. Rosotti, Ewine F. van Dishoeck, Leonardo Testi F We report
the robust detection of coherent, localised deviations from Keplerian rotation possibly associated with the presence of two giant
planets embedded in the disc around HD 163296. The analysis is performed using the DISCMINER channel-map modelling
framework on 12 CO J = 2 − 1 DSHARP data. Not only orbital radius, but also azimuth of the planets are retrieved by ourtechnique. One of the candidate planets, detected at R = 94 ± 6 au, φ = 50 ± 3◦ (P94), is near the centre of one of the gaps
in dust continuum emission, and is consistent with a planet mass of 1 MJup . The other planet, located at R = 261 ± 4 au,
φ = 57 ± 1◦ (P261), is in the region where a velocity kink was previously observed in 12 CO channel maps. Also, we provide asimultaneous description of the height and temperature of the upper and lower emitting surfaces of the disc, and propose theline width as a solid observable to track gas substructure. Using azimuthally averaged line width profiles we detect gas gaps at
R = 38 au, R = 88 au, and R = 136 au, closely matching the location of their dust and kinematical counterparts. Furthermore,
we observe strong azimuthal asymmetries in line widths around the gas gap at R = 88 au, possibly linked to turbulent motions
driven by the P94 planet. Our results confirm that the DISCMINER is capable of finding localised, otherwise unseen velocity
perturbations thanks to its robust statistical framework, but also that it is well suited for studies of the gas properties andvertical structure of protoplanetary discs.

A population of transition disks around evolved stars: Fingerprints of planets? Catalog

14. of disks surrounding Galactic post-AGB binaries

Jacques Kluska, Hans Van Winckel, Quentin Coppée, Glenn-Michael Oomen, Devika Kamath, Valentin Bujarrabal, Michiel Min F Post-asymptotic giant branch (post-AGB) binaries are surrounded by massive disks of gas and dustthat are similar to protoplanetary disks around young stars. We assembled a catalog of all known Galactic post-AGB binaries
with disks. We explore the correlations between the different observables with the aim of learning more about potential diskbinary interactions. We compiled spectral energy distributions of 85 Galactic post-AGB binary systems. We built a color-color
diagram to differentiate between the different disk morphologies traced by the infrared excess. We categorized the different
disk types and searched for correlations with other observational characteristics of these systems. Between 8 and 12that is,disks having no or low near-infrared excess. We find a strong link between these transition disks and the depletion of refractoryelements on the surface of the post-AGB star. We interpret this link as evidence of a mechanism that stimulates the dust
and gas separation within the disk and that also produces the transition disk structure. We propose that such a mechanism islikely to be due to a giant planet carving a hole in the disk, effectively trapping the dust in the outer disk parts. We propose
disk evolutionary scenarios, depending on the presence of such a giant planet in the disk. We advocate that giant planets can
successfully explain the link between the transition disks and the observed depletion of refractory materials. If the planetaryscenario is confirmed, disks around post-AGB binaries could be a unique laboratory for testing planet-disk interactions andtheir influence on the late evolution of binary stars. The question of whether such planets are first- or second-generation bodies
remains to be considered. We argue that these disks are ideal for studying planet formation in unprecedented parameter space.

6

mapping observations toward the Galactic massive star-forming region Sh
15. Ammonia
2-255 and Sh 2-257
Mikito Kohno, Toshihiro Omodaka, Toshihiro Handa, James O. Chibueze, Takumi Nagayama, Ross A. Burns,
Takeru Murase, Ren Matsusaka, Makoto Nakano, Kazuyoshi Sunada, Rin I. Yamada, John H. Bieging F We
performed NH3 (J, K) = (1, 1), (2, 2), and (3, 3) mapping observations toward the Galactic massive star-forming region Sh 2-255
and Sh 2-257 using the Nobeyama 45-m telescope as a part of the KAGONMA (KAgoshima Galactic Object survey with theNobeyama 45-metre telescope by Mapping in Ammonia lines) project. NH3 (1,1) has an intensity peak at the cluster S255 N, is
distributed over 3 pc × 2 pc and is located between two HII regions. The kinetic temperature derived from the NH3 (2, 2)/(1, 1)
ratio was ∼ 35 K near the massive cluster S255 IR. These clusters also show emission with a large line width of ∼ 3-4 km
s−1 . Based on the reported data we suggest that NH3 gas in these regions is affected by stellar feedback from embedded YSO
clusters in S255 IR and S255 N. We also detected NH3 (1,1) emission in a region west of the main gas clump at the location ofa concentration of Class II YSOs adjacent to the HII regions Sh 2-254. The presence of Class II YSOs implies ∼ 2 Myr of starformation, younger than Sh 2-254 (∼ 5 Myr), thus we suggest that star formation in the western region could be influenced by
the older HII region Sh 2-254.

16. Dynamics of magnetic flux tubes in accretion disks of Herbig Ae/Be stars

Sergey A. Khaibrakhmanov, Alexander E. Dudorov F The dynamics of magnetic flux tubes (MFTs) in the accretion
disk of typical Herbig Ae/Be star with fossil large-scale magnetic field is modeled taking into account the buoyant and dragforces, radiative heat exchange with the surrounding gas, and the magnetic field of the disk. The structure of the disk issimulated using our magnetohydrodynamic (MHD) model, taking into account the heating of the surface layers of the disk withthe stellar radiation. The simulations show that MFTs periodically rise from the innermost region of the disk with speeds up
to 10 − 12 km s−1 . MFTs experience decaying magnetic oscillations under the action of the external magnetic field near the
disk’s surface. The oscillation period increases with distance from the star and initial plasma beta of the MFT, ranging fromseveral hours at r = 0.012 au up to several months at r = 1 au. The oscillations are characterized by pulsations of the MFT’s
characteristics including its temperature. We argue that the oscillations can produce observed IR-variability of Herbig Ae/Bestars, which would be more intense than in the case of T Tauri stars, since the disks of Herbig Ae/Be stars are hotter, denser
and have stronger magnetic field.

17. Breaking Orion’s Veil bubble with fossil outflows

U Kavak, J. R. Goicoechea, C. H. M. Pabst, J. Bally, F. F. S. van der Tak, A. G. G. M. Tielens F The roleof feedback in the self-regulation of star formation is a fundamental question in astrophysics. The Orion Nebula is the nearest
site of ongoing and recent massive star formation. It is a unique laboratory for the study of stellar feedback. Recent SOFIA[CII] 158 µm observations revealed an expanding bubble, the Veil shell, being powered by stellar winds and ionization feedback.
We have identified a protrusion-like substructure in the Northwest portion of the Orion Veil Shell that may indicate additional
feedback mechanisms that are highly directional. Our goal is to investigate the origin of the protrusion by quantifying its
possible driving mechanisms. We use the [CII] 158 µm map of the Orion Nebula obtained with the upGREAT instrument
onboard SOFIA. The spectral and spatial resolution of the observations are 0.3 km/s and 16 arcsec, respectively. We consider
three possible origins for this protrusion: Fossil outflow cavities created by jets/outflows during the protostellar accretion phase,pre-existing clumpiness in the OMC-1 core, and the stellar wind during the main sequence phase. Based on the energetics andthe morphology, we conclude that the northwestern part of the pre-existing cloud was locally perturbed by outflows ejected frommassive protostars in the Trapezium cluster. This suggests that the protrusion of the Veil is the result of mechanical rather
than radiative feedback. Furthermore, we argue that the location of the protrusion is a suitable place to break the Orion Veilowing to the photo-ablation from the walls of the protrusion. We conclude that the outflows of massive protostars can influence
the morphology of the future HII,region and even cause breakages in the ionization front. Specifically, the interaction of stellar
winds of main-sequence stars with the molecular core pre-processed by the protostellar jet is important.

18. Anisotropic Infall and Substructure formation in Embedded Disks

Aleksandra Kuznetsova, Jaehan Bae, Lee Hartmann, Mordecai-Mark Mac Low F The filamentary nature of accretion streams found around embedded sources suggest that protostellar disks experience heterogenous infall from the star-forming
environment, consistent with the accretion behavior onto star-forming cores in top-down star-cluster formation simulations. This
may produce disk substructures in the form of rings, gaps, and spirals continuing to be identified by high-resolution imaging
surveys in both embedded Class 0/I and later Class II sources. We present a parameter study of anisotropic infall, informedby the properties of accretion flows onto protostellar cores in numerical simulations, and varying the relative specific angularmomentum of incoming flows as well as their flow geometry. Our results show that anisotropic infall perturbs the disk andreadily launches the Rossby wave instability (RWI). It forms vortices at the inner and outer edge of the infall zone wherematerial is deposited. These vortices drive spiral waves and angular momentum transport, with some models able to drivestresses corresponding to a viscosity parameter on the order of α ∼ 10−2 . The resulting azimuthal shear forms robust pressure

7

bumps that act as barriers to radial drift of dust grains, as demonstrated by post-processing calculations of drift-dominateddust evolution. We discuss how a self-consistent model of anisotropic infall can account for the formation of millimeter rings in
the outer disk as well as producing compact dust disks, consistent with observations of embedded sources.

Molecular Clouds Associated with H II regions and Candidates within l = 106.65◦ to

19. 109.50◦ and b = −1.85◦ to 0.95◦

Chun-Xue Liınst1, 2, Hong-Chi Wangınst1, 2, Yue-Hui Maınst1, Miao-Miao Zhangınst1, Chong Li ınst3, 4,
Yu-Qing Zhengınst1 F We present a large-scale simultaneous survey of the CO isotopologues (12 CO, 13 CO, and C18 O) J
= 1 − 0 line emission toward the Galactic plane region of l = 106.65◦ to 109.50◦ and b = −1.85◦ to 0.95◦ using the Purple
Mountain Observatory 13.7 m millimeter-wavelength telescope. Except for the molecular gas in the solar neighborhood, theemission from the molecular gas in this region is concentrated in the velocity range of [−60, −35] km s−1 . The gas in the region
can be divided into four clouds, with mass in the range of ∼ 103 to 104 M . We have identified 25 filaments based on the13
CO data. The median excitation temperature, length, line mass, line width, and virial parameter of the filaments are 10.89
K, 8.49 pc, 146.11 M pc−1 , 1.01 km s−1 , and 3.14, respectively. Among these filaments, eight have virial parameters of lessthan 2, suggesting that they are gravitationally bound and can lead to star formation. Nineteen H II regions or candidates havepreviously been found in the region and we investigate the relationships between these H II regions/candidates and surrounding
molecular clouds in detail. Using morphology similarity and radial velocity consistency between H II regions/candidates andmolecular clouds as evidence for association, and raised temperature and velocity broadening as signatures of interaction, we
propose that 12 H II regions/candidates are associated with their surrounding molecular clouds. In the case of the H II regionof S142, the energy of the H II region is sufficient to maintain the turbulence in the surrounding molecular gas.

Models of Triggered Star Formation with Young Stellar Objects in Cepheus
20. Testing
OB4
Abby Mintz, Joseph L. Hora, Elaine Winston F OB associations are home to newly formed massive stars, whose turbulent
winds and ionizing flux create H II regions rich with star formation. Studying the distribution and abundance of young stellar
objects (YSOs) in these ionized bubbles can provide essential insight into the physical processes that shape their formation,
allowing us to test competing models of star formation. In this work, we examined one such OB association, Cepheus OB4 (CepOB4) - a well-suited region for studying YSOs due to its Galactic location, proximity, and geometry. We created a photometriccatalog from Spitzer/IRAC mosaics in bands 1 (3.6 µm) and 2 (4.5 µm). We supplemented the catalog with photometry from
WISE, 2MASS, IRAC bands 3 (5.8 µm) and 4 (8.0 µm), MIPS 24 µm, and MMIRS near IR data. We used color-color selections
to identify 821 YSOs, which we classified using the IR slope of the YSOs’ spectral energy distributions (SEDs), finding 67 ClassI, 103 flat spectrum, 569 Class II, and 82 Class III YSOs. We conducted a clustering analysis of the Cep OB4 YSOs and fit
their SEDs. We found many young Class I objects distributed in the surrounding shell and pillars as well as a relative age
gradient of unclustered sources, with YSOs generally decreasing in age with distance from the central cluster. Both of theseresults indicate that the expansion of the H II region may have triggered star formation in Cep OB4.

21. Star Formation Triggered by the expanding bubble S111

Bhaswati Mookerjea F This paper investigates the impact of radiative and mechanical feedback from O-type stars on theirparent molecular clouds and the triggering of formation of future generation of stars. We study the infrared bubble S111 createdby the embedded massive stellar cluster G316.80-0.05. A significant fraction of gas in shells created due to the compression of
the ambient medium by expanding bubbles is photodissociated by the stellar radiation. The kinematics of the shells are thus
best studied using spectroscopic observations of singly ionized carbon, the most dominant species. We have used the velocityresolved maps of the 2 P3/2 →2 P1/2 transition of [C II] at 158 micron, the J=2-1 transition of 13CO and C18O, and the J=1-0transition of HCO+ to study the rim of the bubble S111 that partly coincides with the southern part of the infrared dark ridge
G316.75. The [C II] spectra conclusively show evidence of a shell expanding with a moderate velocity of 7 km/s, which amounts
to a kinetic energy that is 0.5-40 times the thermal energy of the H II region. The pressure causing the expansion of the H II
region arises mainly from the hydrogen ionization and the dust-processed radiation. Among the far-infrared sources located in
the compressed shells, we find the core G316.7799-0.0942 to show broad spectral features consistent with outflow activity andconclude that it is a site of active star formation. Based on the age of the H II region we conclude that this expanding H II
region is responsible for the triggering of the current star formation activity in the region.

822. The width of Herschel filaments varies with distance

G. V. Panopoulou, S. E. Clark, A. Hacar, F. Heitsch, J. Kainulainen, E. Ntormousi, D. Seifried, R. J. Smith
F Context: Filamentary structures in nearby molecular clouds have been found to exhibit a characteristic width of 0.1 pc, as
observed in dust emission. Understanding the origin of this universal width has become a topic of central importance in the
study of molecular cloud structure and the early stages of star formation. Aims: We investigate how the recovered widths offilaments depend on the distance from the observer, by using previously published results from the Herschel Gould Belt Survey.
Methods: We obtained updated estimates on the distances to nearby molecular clouds observed with Herschel by using recent
results based on 3D dust extinction mapping and Gaia. We examined the widths of filaments from individual clouds separately,as opposed to treating them as a single population. We used these per-cloud filament widths to search for signs of variation
amongst the clouds of the previously published study. Results: We find a significant dependence of the mean per-cloud filament
width with distance. The distribution of mean filament widths for nearby clouds is incompatible with that of farther away
clouds. The mean per-cloud widths scale with distance approximately as 4–5 times the beam size. We examine the effects ofresolution by performing a convergence study of a filament profile in the Herschel image of the Taurus Molecular Cloud. We findthat resolution can severely affect the shapes of radial profiles over the observed range of distances. Conclusions: We conclude
that the data are inconsistent with 0.1 pc being the universal characteristic width of filaments.

D-type HII region expansion depends on numerical resolution
23. How
J. M. Pittard, M. M. Kupilas, C. J. Wareing F We investigate the resolution dependence of HII regions expanding pasttheir Strömgren spheres. We find that their structure and size, and the radial momentum that they attain at a given time, isin good agreement with analytical expectations if the Strömgren radius is resolved with dr ≤ 0.3 Rst . If this is not satisfied,
the radial momentum may be over- or under-estimated by factors up to 10 or more. Our work has significance for the amountof radial momentum that a HII region can impart to the ambient medium in numerical simulations, and thus on the relative
importance of ionizing feedback from massive stars.

Warping Away Gravitational Instabilities in Protoplanetary Discs

24. Sahl Rowther, Rebecca Nealon, Farzana Meru F We perform 3D SPH simulations of warped, non-coplanar gravitationally unstable discs to show that as the warp propagates through the self-gravitating disc, it heats up the disc rendering it
gravitationally stable. Thus losing their spiral structure and appearing completely axisymmetric. In their youth, protoplanetary
discs are expected to be massive and self-gravitating, which results in non-axisymmetric spiral structures. However recent observations of young protoplanetary discs with ALMA have revealed that discs with large-scale spiral structure are rarely observedin the midplane. Instead, axisymmetric discs with some also having ring & gap structures are more commonly observed. Our
work invloving warps, non-coplanar disc structures that are expected to commonly occur in young discs, potentially resolves thisdiscrepancy between observations and theoretical predictions. We demonstrate that they are able to suppress the large-scale
spiral structure of self-gravitating protoplanetary discs.

CH3 D detection in Class 0/I proto-brown dwarfs: constraints on CH4 abundances
25. First
B. Riaz, W. -F. Thi F We report the first detection in the J = 1 - 0 rotational transition line of CH D towards three Class
K

0

0

3

0/I proto-brown dwarfs (proto-BDs) from IRAM 30 m observations. Assuming a rotational temperature of 25 K, the CH3 D
abundances (relative to H2 ) are in the range of (2.3–14.5) × 10−7 . The CH4 abundances derived from the CH3 D abundances
and assuming the DCO+ /HCO+ ratios are in the range of (0.05–4.8) ×10−5 . The gas-phase formation of CH3 D via CH2 D+
is enhanced at high densities of 108 –1010 cm−3 and our observations are likely probing the innermost dense and warm regionsin proto-BDs. Thermal and/or non-thermal desorption can return the CH3 D and CH4 molecules formed at an early stage on
grain surfaces to the gas-phase. The gas phase abundances are indicative of warm carbon-chain chemistry in proto-BDs wherecarbon-chain molecules are synthesized in a lukewarm (∼20-30 K) region close to the central source.

chemistry and D/H ratios in Class 0/I proto-brown dwarfs
26. Deuterium
B. Riaz, W. -F. Thi F We have conducted the first extensive observational survey of several deuterated species in 16 Class
0/I proto-brown dwarfs (proto-BDs) and 4 Class Flat/Class II brown dwarfs. Observations were obtained with the IRAM
30m telescope in the DCO+ (3-2), DCN (3-2), DNC (3-2), and N2 D+ (3-2) lines. The DCO+ /H13 CO+ , DCN/H13 CN, and
DNC/HN13 C ratios are comparatively higher and show a narrower range than the DCO+ /HCO+ , DCN/HCN, and DNC/HNC
ratios, respectively. The mean D/H ratios for the proto-BDs derived from these molecules are in the range of ∼0.02-3. Both
low-temperature gas-phase ion-molecule deuteron transfer and grain surface reactions are required to explain the enhanced
deuterium fractionation. The very dense and cold (nH2 ≥106 cm−3 , T ≤10 K) interior of the proto-BDs provide the suitableconditions for efficient deuterium fractionation in these cores. There is no correlation between the D/H ratios and the CO
depletion factor, with the exception of the DCN/HCN ratios that show a strong anti-correlation possibly due to the differencein the peak emitting regions of the DCN and HCN molecules. Over a wide range in the bolometric luminosities spanning9∼0.002–40 L , we find a trend of higher DCO+ /HCO+ (r = -0.7) and DCN/HCN (r = -0.6) ratios, nearly constant DNC/HNC(r = -0.4) and DNC/HN13 C (r = -0.1) ratios, lower N2 D+ /N2 H+ ratios (r = 0.6) in the proto-BDs compared to protostars.
Only one Class II brown dwarf shows emission in the DCO+ (3-2) line. No correlation is seen between the D/H ratios and theevolutionary stage.

Connecting Galactic and extragalactic outflows: From the Cygnus-X cluster to active

27. galaxies

I. M. Skretas, L. E. Kristensen F Molecular outflows are often detected originating from both protostellar and extragalactic
sources. Studies of low-mass, isolated high-mass, and extragalactic sources reveal scaling relations connecting the force carriedby an outflow and the properties of the source that drives it. The aim of this work is to examine the effects of clustered starformation on the protostellar outflows and their scaling relations and to explore the possibility that outflows varying greatly
scale and energetics are consistent with being launched by the same physical processes. High-angular resolution CO J = 3-2
observations were used of ten high-mass protostars in the Cygnus-X molecular cloud, obtained at the SMA as part of the
PILS-Cygnus survey. From these data, the outflow force was measured. In addition, an extended sample of protostellar andextragalactic outflow-force measurements was assembled from existing literature to allow for a direct comparison of the scaling
relations of the two types of outflows. Molecular outflows were detected originating from all ten sources of the PILS-Cygnus
survey, and their outflow forces are found in close agreement with measurements from the literature. The comparison of the
protostellar and extragalactic sources reveals, with 95% confidence, that Class 0 protostars and extragalactic sources follow thesame outflow force–bolometric luminosity correlation. The close agreement between the Cygnus-X sources and sources of similarenvelope mass and bolometric luminosity suggests that clustered star formation has no significant effect on protostellar outflows.
We find a strong indication that protostellar and extragalactic outflows are consistent with having a similar launch mechanism.
The existence of such a mechanism would enable the development of a single universal outflow launch model, although more
observations are required in order to verify this connection.

ALMA High-resolution Multiband Analysis for the Protoplanetary Disk around TW

28. HyaTakashi Tsukagoshi, Hideko Nomura, Takayuki Muto, Ryohei Kawabe, Kazuhiro D. Kanagawa, Satoshi Okuzumi,
Shigeru Ida, Catherine Walsh, Tom J. Millar, Sanemichi Z. Takahashi, Jun Hashimoto, Taichi Uyama, Motohide Tamura F We present a high-resolution (2.5 au) multiband analysis of the protoplanetary disk around TW Hya using
ALMA long baseline data at Bands 3, 4, 6, and 7. We aim to reconstruct a high-sensitivity millimeter continuum image
and revisit the spectral index distribution. The imaging is performed by combining new ALMA data at Bands 4 and 6 withavailable archive data. Two methods are employed to reconstruct the images; multi-frequency synthesis (MFS) and the fiducial
image-oriented method, where each band is imaged separately and the frequency dependence is fitted pixel by pixel. We findthat the MFS imaging with the second order of Taylor expansion can reproduce the frequency dependence of the continuum
emission between Bands 3 and 7 in a manner consistent with previous studies and is a reasonable method to reconstruct the
spectral index map. The image-oriented method provides a spectral index map consistent with the MFS imaging, but witha two times lower resolution. Mock observations of an intensity model were conducted to validate the images from the two
methods. We find that the MFS imaging provides a high-resolution spectral index distribution with an uncertainty of < 10 %.
Using the submillimeter spectrum reproduced from our MFS images, we directly calculated the optical depth, power-law index
of the dust opacity coefficient (β), and dust temperature. The derived parameters are consistent with previous works, and theenhancement of β within the intensity gaps is also confirmed, supporting a deficit of millimeter-sized grains within the gaps.

29. A 16 au Binary in the Class 0 Protostar L1157 MMS

John J. Tobin, Erin G. Cox, Leslie W. Looney F We present VLA observations toward the Class 0 protostar L1157
MMS at 6.8 mm and 9 mm with a resolution of 0.04" (14 au). We detect two sources within L1157 MMS and interpret thesesources as a binary protostar with a separation of 16 au. The material directly surrounding the binary system within the inner
50 au radius of the system has an estimated mass of 0.11 M , calculated from the observed dust emission. We interpret theobserved binary system in the context of previous observations of its flattened envelope structure, low rates of envelope rotationfrom 5000 to 200 au scales, and an ordered, poloidal magnetic field aligned with the outflow. Thus, L1157 MMS is a prototype
system for magnetically-regulated collapse and the presence of a compact binary within L1157 MMS demonstrates that multiple
star formation can still occur within envelopes that likely have dynamically important magnetic fields.

10

ALMA observations of the Extended Green Object G19.01−0.03: I. A Keplerian disc30. in a massive protostellar system

Gwenllian M. Williams, Claudia J. Cyganowski, Crystal L. Brogan, Todd R. Hunter, John D. Ilee, Pooneh
Nazari, J. M. Diederik Kruijssen, Rowan J. Smith, Ian A. Bonnell F Using the Atacama Large Millimetre/submillimeter
Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), we observed the Extended Green Object (EGO) G19.01−0.03
with sub-arcsecond resolution from 1.05 mm to 5.01 cm wavelengths. Our ∼ 0.400 ∼ 1600 AU angular resolution ALMA observations reveal a velocity gradient across the millimetre core MM1, oriented perpendicular to the previously known bipolar
molecular outflow, that is consistently traced by 20 lines of 8 molecular species with a range of excitation temperatures, including
complex organic molecules (COMs). Kinematic modelling shows the data are well described by models that include a disc in
Keplerian rotation and infall, with an enclosed mass of 40 − 70M (within a 2000 AU outer radius) for a disc inclination angleof i = 40◦ , of which 5.4 − 7.2M is attributed to the disc. Our new VLA observations show that the 6.7 GHz Class II methanol
masers associated with MM1 form a partial ellipse, consistent with an inclined ring, with a velocity gradient consistent withthat of the thermal gas. The disc-to-star mass ratio suggests the disc is likely to be unstable and may be fragmenting into
as-yet-undetected low mass stellar companions. Modelling the centimetre–millimetre spectral energy distribution of MM1 shows
the ALMA 1.05 mm continuum emission is dominated by dust, whilst a free-free component, interpreted as a hypercompact
HII region, is required to explain the VLA ∼5 cm emission. The high enclosed mass derived for a source with a moderatebolometric luminosity (∼104 L ) suggests that the MM1 disc may feed an unresolved high-mass binary system.

31. Magnetic Spirals in Accretion Flows Originated from Misaligned Magnetic Field

Weixiao Wang, Miikka S. Väisälä, Hsien Shang, Ruben Krasnopolsky, Zhi-Yun Li, Ka Ho Lam, Feng Yuan F
Misalignment between rotation and magnetic field has been suggested to be one type of physical mechanisms which can easen
the effects of magnetic braking during collapse of cloud cores leading to formation of protostellar disks. However, its essential
factors are poorly understood. Therefore, we perform a more detailed analysis of the physics involved. We analyze existing
simulation data to measure the system torques, mass accretion rates and Toomre Q parameters. We also examine the presenceof shocks in the system. While advective torques are generally the strongest, we find that magnetic and gravitational torques
can play substantial roles in how angular momentum is transferred during the disk formation process. Magnetic torques canshape the accretion flows, creating two-armed magnetized inflow spirals aligned with the magnetic field. We find evidence ofan accretion shock that is aligned according to the spiral structure of the system. Inclusion of ambipolar diffusion as exploredin this work has shown a slight influence in the small scale structures but not in the main morphology. We discuss potential
candidate systems where some of these phenomena could be present.

32. Dissecting the different components of the modest accretion bursts of the very young
protostar HOPS 373

Sung-Yong Yoon, Gregory J. Herczeg, Jeong-Eun Lee, Ho-Gyu Lee, Doug Johnstone, Watson Varricatt, John J.
Tobin, Carlos Contreras Peña, Steve Mairs, Klaus Hodapp, P. Manoj, Mayra Osorio, S. Thomas Megeath, theJCMT Transient Team F Observed changes in protostellar brightness can be complicated to interpret. In our JCMT Transient monitoring survey, we discovered that a young binary protostar, HOPS 373, is undergoing a modest 30% brightness increaseat 850 µm, caused by a factor of 1.8−3.3 enhancement in the accretion rate. The initial burst occurred over a few months,
with a sharp rise and then shallower decay. A second rise occurred soon after the decay, and the source is still bright one
year later. The mid-IR emission, the small-scale CO outflow mapped with ALMA, and the location of variable maser emission
indicate that the variability is associated with the SW component. The near-infrared and NEOWISE W 1 and W 2 emission
is located along the blueshifted CO outflow, spatially offset by ∼ 3 to 400 from the SW component. The K-band emission
imaged by UKIRT shows a compact H2 emission source at the edge of the outflow, with a tail tracing the outflow back to thesource. The W 1 emission, likely dominated by scattered light, brightens by 0.7 mag, consistent with expectations based on the
sub-mm lightcurve. The signal of continuum variability in K-band and W 2 is masked by stable H2 emission, as seen in our
Gemini/GNIRS spectrum, and perhaps by CO emission. These differences in emission sources complicate infrared searches forvariability of the youngest protostars.

A large population study of protoplanetary disks: Explaining the millimeter size-luminosity

33. relation with or without sub-structure

Apostolos Zormpas, Tilman Birnstiel, Giovanni P. Rosotti, Sean M. Andrews F Recent sub-arcsecond resolution
surveys of the dust continuum emission from nearby protoplanetary disks showed a strong correlation between the sizes andluminosities of the disks. We aim to explain the origin of the (sub-)millimeter size-luminosity relation (SLR) between the 68%
effective radius (ref f ) of disks with their continuum luminosity (Lmm ), with models of gas and dust evolution in a simple viscousaccretion disk and radiative transfer calculations. We use a large grid of models (105 simulations) with and without planetarygaps, varying the initial conditions of the key parameters. We calculate the disk continuum emission and the effective radius
for all models as a function of time. By selecting those simulations that continuously follow the SLR, we can derive constraints

11

on the input parameters of the models. We confirm previous results that models of smooth disks in the radial drift regime are
2compatible with the observed SLR (Lmm ∝ reff ) but only smooth disks cannot be the reality. We show that the SLR is more
widely populated if planets are present. However they tend to follow a different relation than smooth disks, potentially implying
5/4
that a mixture of smooth and sub-structured disks are present in the observed sample. We derive a SLR (Lmm ∝ ref f ) for diskswith strong sub-structure. To be compatible with the SLR, models need to have an initially high disk mass (≥ 2.5 · 10−2 M? )and low turbulence-parameter α values (≤ 10−3 ). Furthermore, we find that the grain composition and porosity drasticallyaffects the evolution of disks on the size-luminosity diagram where relatively compact grains that include amorphous carbon
are favoured. Moreover, a uniformly optically thick disk with high albedo (0.9) that follows the SLR cannot be formed from an
evolutionary procedure.

formation near the Sun is driven by expansion of the Local Bubble
34. Star
Catherine Zucker, Alyssa A. Goodman, João Alves, Shmuel Bialy, Michael Foley, Joshua S. Speagle, Josefa
Großschedl, Douglas P. Finkbeiner, Andreas Burkert, Diana Khimey, Cameren Swiggum F For decades we have
known that the Sun lies within the Local Bubble, a cavity of low-density, high-temperature plasma surrounded by a shell of
cold, neutral gas and dust. However, the precise shape and extent of this shell, the impetus and timescale for its formation, andits relationship to nearby star formation have remained uncertain, largely due to low-resolution models of the local interstellar
medium. Leveraging new spatial and dynamical constraints from the Gaia space mission, here we report an analysis of the 3D
positions, shapes, and motions of dense gas and young stars within 200 pc of the Sun. We find that nearly all the star-forming
complexes in the solar vicinity lie on the surface of the Local Bubble and that their young stars show outward expansion mainly
perpendicular to the bubble’s surface. Tracebacks of these young stars’ motions support a scenario where the origin of the Local
Bubble was a burst of stellar birth and then death (supernovae) taking place near the bubble’s center beginning 14 Myr ago.
The expansion of the Local Bubble created by the supernovae swept up the ambient interstellar medium into an extended shellthat has now fragmented and collapsed into the most prominent nearby molecular clouds, in turn providing robust observational
support for the theory of supernova-driven star formation.

12