SFN #354 65-72
担当：土井 聖明 (総研大D1)

flfi

65. The 30 Doradus Molecular Cloud at 0.4 pc Resolution with the Atacama Large Mil- limeter/submillimeter
Array: Physical Properties and the Boundedness of CO-emitting Structures
66. A new method for direct measurement of isotopologue ratios in protoplanetary disks: a case study of the
12CO/13CO ratio in the TW Hya disk
67. Molecular Gas Structures traced by 13CO Emission in the 18,190 12CO Molecular Clouds from the MWISP
Survey68. Dependence of Molecular Cloud Samples on Angular Resolution, Sensitivity, and Algorithms
69. Two Candidate KH 15D-like Systems from the Zwicky Transient Facility
70. Magnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I. Orion A
71. ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – XI. From in ow to infall
in hub- lament systems
72. The Pre-main Sequence: Challenges and Prospects for Asteroseismology

A new method for direct measurement of isotopologue ratios in protoplanetary disks:a case study of the 12 CO/13 CO ratio in the TW Hya disk

Tomohiro C. Yoshida, Hideko Nomura, Kenji Furuya, Takashi Tsukagoshi, Seokho Lee F Planetary systems
are thought to be born in protoplanetary disks. Isotope ratios are a powerful tool for investigating the material origin andevolution from molecular clouds to planetary systems via protoplanetary disks. However, it is challenging to measure theisotope (isotopologue) ratios, especially in protoplanetary disks, because the emission lines of major species are saturated. We
developed a new method to overcome these challenges by using optically thin line wings induced by thermal broadening. Asa first application of the method, we analyzed two carbon monoxide isotopologue lines, 12 CO 3 2 and 13 CO 3 2, fromarchival observations of a protoplanetary disk around TW Hya with the Atacama Large Millimeter/sub-millimeter Array. The
12
CO/13 CO ratio was estimated to be 20 ± 5 at disk radii of 70 110 au, which is significantly smaller than the value observedin the local interstellar medium, ⇠ 69. It implies that an isotope exchange reaction occurs in a low-temperature environment
with C/O > 1 . In contrast, it is suggested that 12 CO/13 CO is higher than ⇠ 84 in the outer disk (r > 130 au), which can be
explained by the diﬀerence in the binding energy of the isotopologues on dust grains and the CO gas depletion processes. Our
results imply that the gas-phase 12 CO/13 CO can vary by a factor of > 4 even inside a protoplanetary disk, and therefore, canbe used to trace material evolution in disks.

Molecular Gas Structures traced by 13 CO Emission in the 18,190 12 CO Molecular Clouds
from the MWISP Survey
原始惑星系円盤TW
Hyaの炭素同位体(12CO/13CO)を観測的に制限

Lixia Yuan, Ji Yang, Fujun Du, Yang Su, Xunchuan Liu, Shaobo Zhang, Yan Sun, Xin Zhou, Qing-Zeng Yan,
Yuehui Ma F After the morphological classification of the 18,190 12 CO molecular clouds, we further investigate the propertiesof their internal molecular gas structures traced by the 13 CO(J = 1 0) line emissions. Using three diﬀerent methods to extract

分子輝線の端の位置での強度比に着目

・円盤内側(<110 au)でISM(~69)よりも小さく(~21)(=同位体が濃縮)・円盤外側(>130 au)でISM(~69)よりも大きい(>84)(=rare
isotopeが減ってる)20I(ν) = B(ν, T)(1 − e −τ(ν))

背景・同位体は原始惑星系円盤の物質トレーサー
・円盤観測と隕石や彗星などの物質のつながりを明らかに
・同位体比の観測的見積りは難しい
・多い方は光学的に厚くなる
wing

・少ない方は感度が足りない・これまでは観測と、全部入りの物理モデルとの比較から推定

centerwing

吉田くん発表資料より

・モデル依存性のない推定法(=輝線のふちの強度比から見積もる)を提案
・TW Hyaの観測に適応して見積もる

すばる プレスリリースより

手法
・輝線の強度モデルを作って強度比を波長ごとにプロット・thickだと強度比は実際の密度比と相関しない
・thinだと強度比は密度比に対応

situations. 12CO and 13CO 3–2 lines were targeted because they
are the strongest isotopologue lines. The temperature structure
and the ﬁducial 12CO density structure were taken from athermochemical model of the TW Hya disk presented in Lee
et al. (2021), and the 13CO density structure was created suchthat the 12CO/13CO ratios were uniform in the disk. The
radiative transfer equations at r = 100 au for the 12CO and 13CO
lines were solved by assuming LTE and a turbulence of
0.1× the local thermal speed (Flaherty et al. 2018). We notethat the effect of (subsonic) turbulence would be negligible
because such turbulence changes the exponent in Equation (4)only slightly even if we take it into account (Appendix A). The
line-of-sight velocity was input assuming the Keplerianrotation with a stellar mass of 0.81 Me and an inclination of

an interval of 20, and the colto be 0.1, 1, and 10 times
densities correspond to the op
33, and 330. The color scalein the model, and the gray
Equation (7) using the values
from Equation (7), we have
Because the formulation of
geneous slab model, τ0,12 shvalue to approximate the de
Therefore, we ﬁrst speciﬁed t
of the 12CO line becomes ocalculated using the model),結果・内側で13COが多く、外側で13CO減ったモデルで観測を再現

Figure 6. t12 vs. t1229 28 t13 calculated from the stacked line proﬁles fromobservations (points), and models with the ﬁxed isotopologue ratio of 69(dashed lines). Different colors indicate different disk radii.

used. The 13CO density model was created by dividing the 12CO
density by 69 (the local ISM value; Wilson 1999) uniformly.
Also, we adopted the dust distribution described in Lee et al.
(2021). Notably, the effect of the dust continuum on the line
emission is negligible at r > 70 au. We used the RADMC-3D(Dullemond et al. 2012) to create image cubes, assuming the same
parameters, such as the inclination angle of the TW Hya disk, as
described above. The channel maps were convolved with anobservational beam (0 5 × 0 5), and the line proﬁles at eachpixel were smoothed with a 0.06 km s−1 FWHM Gaussian. Then,
we analyzed them in the same manner as the observations. The
colored dashed lines in Figure 6 show the results. In the opticallyMagnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I.
Orion A

Mengke Zhao, Jianjun Zhou, Yue Hu, A. Lazarian, Xindi Tang, Willem A. Baan, Jarken Esimbek, Yuxin He,
Dalei Li, Weiguang Ji, Kadirya Tursun F Magnetic fields play an important role in the evolution of molecular clouds
and star formation. Using the Velocity Gradient Technique (VGT) model, we measured the magnetic field in Orion A using
the 12CO, 13CO, and C18O (1-0) emission lines at a scale of 0.07 pc. The measured B-field shows an east-west orientationthat is perpendicular to the integral shaped filament of Orion A at large scale. The VGT magnetic fields obtained from 13CO
and C18O are in agreement with the B-field that is measured from the Planck 353 GHz dust polarization at a scale of 0.55 pc.
Removal of density eﬀects by using a Velocity Decomposition Algorithm can significantly improve the accuracy of the VGT in
tracing magnetic fields with the 12CO (1-0) line. The magnetic field strength of seven sub-clouds, OMC-1, OMC-2, OMC-3,
OMC-4, OMC-5, L 1641-N, and NGC 1999 has also been estimated with the Davis-Chandrasekhar-Fermi (DCF) and MM2technique, and these are found to be in agreement with previous results obtained from dust polarization at far-infrared andsub-millimeter wavelengths. At smaller scales, the VGT proves a good method to measure magnetic fields.

Velocity Gradient Technique (VGT)を用いたOrion Aの磁場の推定
・分子輝線の勾配から磁場構造を推定する 21
・0.07 pcスケール(=高空間分解)での磁場構造の推定を行なった
・Planckによるダスト偏光と整合的
・Davis-Chandrasekhar-Fermi(DCF)とTwo Mach Numbers Method (MM2)を用いた磁場の強度は赤外-ミリ波の偏光と整合的背景・円盤磁場構造は分子雲の形成・進化や星形成に重要
・近傍大質量星形成領域のOrion Aの磁場構造を解明する

手法

The Astrophysical Journal, 835:41 (11pp), 2017 January 20

doi:10.3847/1538-4357/835/1/41© 2017. The American Astronomical Society. All rights reserved.

VELOCITY GRADIENTS AS A TRACER FOR MAGNETIC FIELDS

・速度勾配が磁場に垂直になる (右の論文)
・MHD乱流が磁場に垂直方向に発達する(Alfven波)
・磁場と垂直方向に速度構造(=速度勾配)を持つDiego F. González-Casanova and A. Lazarian

Astronomy Department, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706-1582, USA; casanova@astro.wisc.edu,
lazarian@astro.wisc.edu
Received 2016 August 19; revised 2016 November 29; accepted 2016 November 29; published 2017 January 17

ABSTRACT
Strong Alfvénic turbulence develops eddy-like motions perpendicular to the local direction of magnetic ﬁelds. This
local alignment induces velocity gradients perpendicular to the local direction of the magnetic ﬁeld. We use thisfact to propose a new technique of studying the direction of magnetic ﬁelds from observations, which we call thevelocity gradient technique. We test our idea by employing the synthetic observations obtained via 3D
magnetohydrodynamical (MHD) numerical simulations for different sonic and Alfvén Mach numbers. We
calculate the velocity gradient, W, using the velocity centroids. We ﬁnd that W traces the projected magnetic ﬁeld
best for the synthetic maps obtained with sub-Alfvénic simulations and provides good point-wise correspondence
between the magnetic ﬁeld direction and the direction of W. The reported alignment is much better than thealignment between the density gradients and the magnetic ﬁeld, and we demonstrate that it can be used to ﬁnd themagnetic ﬁeld strength with an analog of the Chandrasekhar–Fermi method. This new technique does not require
dust polarimetry, and our study opens up a new way of studying magnetic ﬁelds using spectroscopic data.

・しかし、自己重力が効くようになると速度構造が磁場と整列する

Key words: ISM: kinematics and dynamics – ISM: magnetic ﬁelds – magnetohydrodynamics (MHD) – turbulence
1. INTRODUCTION

・ある密度以下では速度勾配 磁場
・ある密度以上では速度勾配//磁場
として磁場構造を推定した
・ここでは 3x10^21 cm^-2 を境界にした

It is well established that the interstellar medium (ISM) is
turbulent, which affects the dynamics of different astrophysicalphenomena such as star formation, cosmic-ray acceleration,
galaxy evolution, and feedback (Ferrière 2001; Elmegreen &Scalo 2004; de Avillez & Breitschwerdt 2005; McKee &Ostriker 2007; Falgarone et al. 2008). Widely used evidence ofthe turbulence in the ISM is seen in the so-called big power law
in the sky (Armstrong et al. 1995; Chepurnov & Lazarian2010), which reﬂects the Kolmogorov spectrum of electron
density ﬂuctuations in nonthermal Doppler broadening (seeDraine 2011), in the power-law scalings of the ﬂuctuations
measured in position–position velocity (PPV) space (seeLazarian & Pogosyan 2000; Stanimirović & Lazarian 2001;
Padoan et al. 2009; Chepurnov et al. 2010, 2015) (see Lazarian
et al. 2009, for a review), and in velocity centroids (see Miesch
et al. 1999; Miville-Deschênes et al. 2003).
The study of the direction and measurements of the intensityof magnetic ﬁelds present a challenging problem. Polarization
arising from grains aligned with longer axes perpendicular to amagnetic ﬁeld allows to estimate the direction of the magnetic
ﬁeld, but the existing uncertainties in grain alignment theory
and the failure of grain alignment at large optical depths limit
the ability of the technique to trace magnetic ﬁelds without
ambiguities (see Lazarian 2007; Lazarian et al. 2015a, for areview). This also affects the Chandrasekhar–Fermi (C–F)
technique, which is used to determine the intensity of magnetic
ﬁelds when the variations in polarization direction and velocity
dispersion are both known.
Other techniques that are used to study magnetic ﬁelds inmolecular clouds, e.g., based on the Zeeman effect or on theGoldreich–Kylaﬁs effect, have their own limitations (seeCrutcher 2012). Faraday rotation is able to measure theintensity of the ﬁeld along the line of sight (LOS) in ionized
media (Padoan et al. 2001; Ostriker 2003, pp. 252–270;
Crutcher 2012). The atomic/ionic alignment technique provides a promising approach for studies of the magnetic ﬁeld,
but the ability of the technique to trace magnetic ﬁeld has not

・Velocity Decomposition Algorithm (VDA)を用いた補正をした(速度勾配と密度勾配を切り分けるらしい?)

yet been demonstrated with observational data (see Yan &Lazarian 2015).
Therefore there is intense interest in developing newtechniques. For instance, the anisotropy analysis of statisticalproperties of variations in the observable Doppler-shifted lines(Lazarian et al. 2002; Heyer & Brunt 2004; Esquivel &Lazarian 2005, 2009; Burkhart et al. 2015) proved to be a
promising way of obtaining the mean magnetic ﬁeld as well as
the media magnetization (see also Esquivel et al. 2015; Kandel
et al. 2016a, 2016b). The difference in the velocities of ionsand neutrals that is caused by the difference in their damping inmagnetohydrodynamic (MHD) turbulence has been suggested
as another way of studying magnetic ﬁelds (Li & Houde 2008).
The quantitative treatment of the technique shows, however,that it has its limitations (see Xu et al. 2015). New approaches
for studying magnetic ﬁelds using synchrotron intensity andpolarization have been suggested in Lazarian & Pogosyan(2012, 2016). All in all, the search of new ways of studying
magnetic ﬁelds is characterized by intensive research; alltechniques have some shortcomings and limitations.
The Chandrasekhar & Fermi (1953, C–F) method candetermine magnetic ﬁeld strengths by estimating the variationsin the directions of the magnetic ﬁeld lines, assuming Alfvénicmotions (Ostriker et al. 2001; Falceta-Gonçalves et al. 2008;
Houde et al. 2009; Novak et al. 2009). The C–F method in its
simplest from estimates the magnetic ﬁeld strength asB»

4QS Ev EG ,(1 )where ρ is the density, Ev is the velocity dispersion, and EG is
the polarization angle dispersion. An improved C–F techniquein (Falceta-Gonçalves et al. 2008) was shown to be able todetermine the intensity of the magnetic ﬁeld with anuncertainty lower than a 20%. In the case when turbulence isinjected on small scales, Cho & Yoo (2016) provide anothermodiﬁcation of the C–F method.
In a strongly magnetized turbulent medium, the turbulent
eddies rotate preferentially about the local direction of the結果・細かい磁場構造がわかった
・本当に磁場構造をトレースしてるのか？
→次ページへ結果・偏光の結果と比較して程度よく一致している
AM：一致度の指標(-1~1)

be used to trace material evolution in disks.

Molecular Gas Structures traced byfrom the MWISP Survey

13

CO Emission in the 18,190

12

CO Molecular Clouds

Lixia Yuan, Ji Yang, Fujun Du, Yang Su, Xunchuan Liu, Shaobo Zhang, Yan Sun, Xin Zhou, Qing-Zeng Yan,
Yuehui Ma F After the morphological classification of the 18,190 12 CO molecular clouds, we further investigate the propertiesof their internal molecular gas structures traced by the 13 CO(J = 1 0) line emissions. Using three diﬀerent methods to extract
the 13 CO gas structures within each 12 CO cloud, we find that ⇠ 15% of 12 CO clouds (2851) have 13 CO gas structures and these12
CO clouds contribute about 93% of the total integrated flux of 12 CO emission. In each of 2851 12 CO clouds with 13 CO gas
structures, the 13 CO emission area generally does not exceed 70% of the 12 CO emission area, and the 13 CO integrated flux does20
12
not exceed 20% of the CO integrated flux. We reveal a strong correlation between the velocity-integrated intensities of 12 COlines and those of 13 CO lines in both 12 CO and 13 CO emission regions. This indicates the H2 column densities of molecular13
13
12
clouds are crucial for the CO lines emission. After linking the CO structure detection rates of the 18,190 CO molecular
clouds to their morphologies, i.e. nonfilaments and filaments, we find that the 13 CO gas structures are primarily detectedin the 12 CO clouds with filamentary morphologies. Moreover, these filaments tend to harbor more than one 13 CO structure.
That demonstrates filaments not only have larger spatial scales, but also have more molecular gas structures traced by 13 COlines, i.e. the local gas density enhancements. Our results favor the turbulent compression scenario for filament formation, in
which dynamical compression of turbulent flows induces the local density enhancements. The nonfilaments tend to be in the
low-pressure and quiescent turbulent environments of the diﬀuse interstellar medium.

Dependence of Molecular Cloud Samples on Angular Resolution, Sensitivity, and Algorithms

Qing-Zeng Yan, Ji Yang, Yang Su, Yan Sun, Xin Zhou, Ye Xu, Hongchi Wang, Shaobo Zhang, Zhiwei Chen
F In this work, we investigate the observational and algorithmic eﬀects on molecular cloud samples identified from positionposition-velocity (PPV) space. By smoothing and cutting oﬀ the high quality data of the Milky Way Imaging Scroll Painting(MWISP) survey, we extract various molecular cloud samples from those altered data with the DBSCAN (density-based spatial
clustering of applications with noise) algorithm. Those molecular cloud samples are subsequently used to gauge the significance of sensitivity, angular/velocity resolution, and DBSCAN parameters. Two additional surveys, the FCRAO Outer Galaxy
Survey (OGS) and the CfA-Chile 1.2 m complete CO (CfA-Chile) survey, are used to verify the MWISP results. We foundthat molecular cloud catalogs are not unique and the boundary and therefore the number shows strong variation with angular背景・分子雲は星間物質の基本的な形態の一つ
低温(~10 K)で高密度(>30 cm^-3)
・Herschelから星形成にはフィラメント構造が重要
・Purple Mountain Observatoryを用いたMWISPサーベイでCOとその同位体の無バイアスサーベイが行われた
・18190個の分子雲が同定
・COで形態分類(フィラメントかそうでないか)が行われた
・フィラメントは数では10%程度だが放射の90%を担っている・フィラメントかそうでないかの空間分布に偏りはある一方、平均的なH2柱密度は空間的に偏りはない
・より高密度のガスのトレーサーである13CO観測から、これらの物理的背景を探る

The Astrophysical Journal Supplement Series, 261:37 (29pp), 2022 August

結果

Table 1The Number Detection Rates, Area Ratios, and Total Flux Ratios between the13
12
CO and CO Line Emission from Three Methods

・13COで同定されたのは右表

Methods

・1つの12CO分子雲中に複数のClipping
DBSCAN
Moment Mask

13COピークを持つものもある(~40%)
・13COで見つかった天体は、より大きく(空間、速度)、

Number Detection Rates

Area Ratios

Flux Ratios

13.5%
15.7%
15%

10.8%
20.3%
20.7%

4.1%
6.3%
7.3%

Note. The number detection rate is the number of 12CO clouds having 13CO
structures divided by the total number of 18,190. The area ratio is the ratio
between the total angular area of the extracted 13CO structures and the total
12
12
CO angular area of the 18,190 CO clouds. The ﬂux ratio is the total
integrated ﬂux of the extracted 13CO line emission divided by that of the 12CO
line emission.

より明るく
より温度が高い傾向が見られた13

molecular clouds are identiﬁed to have CO emission. The
13
moment mask extracts CO line emission in 2735 molecular
clouds. The number detection rates in all of the 18,190
molecular clouds by the three methods are listed in Table 1.

・13COの分子雲は主に12COでの3.3.3. Area Ratios between the
フィラメント構造を持つものの中にある

13

CO and12

12

CO Line Emission

The total angular area for the 18,190 CO molecular clouds
また、多くの場合複数の13COのクランプを持つ
2

3
13

The C
three methcloud belo
12
within a
structures.
structuresof the extr
The mean1
within aof each p
its corresp
S (Vspan (l,grated ﬂux
an individ
0.166 × 0.
13
the CO l
and dv = 0(Tpeak,13 CO )1
extracted
The num
velocity s
intensities
by the thre

clouds, i.e., GMCs represent molecular cloud samples themselves.

Two Candidate KH 15D-like Systems from the Zwicky Transient Facility

Wei Zhu, Klaus Bernhard, Fei Dai, Min Fang, J. J. Zanazzi, Weicheng Zang, Subo Dong, Franz-Josef Hambsch,
Tianjun Gan, Zexuan Wu, Michael Poon F KH 15D contains a circumbinary disk that is tilted relative to the orbital
plane of the central binary. The precession of the disk and the orbital motion of the binary together produce rich phenomena in
the photometric light curve. In this work, we present the discovery and preliminary analysis of two objects that resemble the key
features of KH 15D from the Zwicky Transient Facility. These new objects, Bernhard-1 and Bernhard-2, show large-amplitude(> 1.5 mag), long-duration (more than tens of days), and periodic dimming events. A one-sided screen model is developed
to model the photometric behaviour of these objects, the physical interpretation of which is a tilted, warped circumbinary
disk occulting the inner binary. Changes in the object light curves suggest potential precession periods over timescales longer
than 10 years. Additional photometric and spectroscopic observations are encouraged to better understand the nature of theseinteresting systems.

Magnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I.
Orion A

Mengke Zhao, Jianjun Zhou, Yue Hu, A. Lazarian, Xindi Tang, Willem A. Baan, Jarken Esimbek, Yuxin He,
Dalei Li, Weiguang Ji, Kadirya Tursun F Magnetic fields play an important role in the evolution of molecular clouds
and star formation. Using the Velocity Gradient Technique (VGT) model, we measured the magnetic field in Orion A using
the 12CO, 13CO, and C18O (1-0) emission lines at a scale of 0.07 pc. The measured B-field shows an east-west orientationthat is perpendicular to the integral shaped filament of Orion A at large scale. The VGT magnetic fields obtained from 13CO
and C18O are in agreement with the B-field that is measured from the Planck 353 GHz dust polarization at a scale of 0.55 pc.
Removal of density eﬀects by using a Velocity Decomposition Algorithm can significantly improve the accuracy of the VGT in
tracing magnetic fields with the 12CO (1-0) line. The magnetic field strength of seven sub-clouds, OMC-1, OMC-2, OMC-3,
OMC-4, OMC-5, L 1641-N, and NGC 1999 has also been estimated with the Davis-Chandrasekhar-Fermi (DCF) and MM2technique, and these are found to be in agreement with previous results obtained from dust polarization at far-infrared andsub-millimeter wavelengths. At smaller scales, the VGT proves a good method to measure magnetic fields.

背景

2天体発見したmodels, motivating future careful treatment of this important process.

The 30 Doradus Molecular Cloud at 0.4 pc Resolution with the Atacama Large Millimeter/submillimeter Array: Physical Properties and the Boundedness of CO-emitting
Structures

Tony Wong, Luuk Oudshoorn, Eliyahu Sofovich, Alex Green, Charmi Shah, Rémy Indebetouw, Margaret
Meixner, Alvaro Hacar, Omnarayani Nayak, Kazuki Tokuda, Alberto D. Bolatto, Mélanie Chevance, Guido De
Marchi, Yasuo Fukui, Alec S. Hirschauer, K. E. Jameson, Venu Kalari, Vianney Lebouteiller, Leslie W. Looney,
Suzanne C. Madden, Toshikazu Onishi, Julia Roman-Duval, Mónica Rubio, A. G. G. M. Tielens F We present
results of a wide-field (approximately 60 x 90 pc) ALMA mosaic of CO(2-1) and 13 CO(2-1) emission from the molecular cloud
associated with the 30 Doradus star-forming region. Three main emission complexes, including two forming a bowtie-shaped
structure extending northeast and southwest from the central R136 cluster, are resolved into complex filamentary networks.
Consistent with previous studies, we find that the central region of the cloud has higher line widths at fixed size relative to therest of the molecular cloud and to other LMC clouds, indicating an enhanced level of turbulent motions. However, there is noclear trend in gravitational boundedness (as measured by the virial parameter) with distance from R136. Structures observedin 13 CO are spatially coincident with filaments and are close to a state of virial equilibrium. In contrast, CO structures vary
greatly in virialization, with low CO surface brightness structures outside of the main filamentary network being predominantly
unbound. The low surface brightness structures constitute 10remnants of previously star-forming gas clumps, or alternatively
the CO-emitting parts of more massive, CO-dark structures.

A new method for direct measurement of isotopologue ratios in protoplanetary disks:
12
13
a case study of the CO/ CO ratio in the TW Hya disk

Tomohiro C. Yoshida, Hideko Nomura, Kenji Furuya, Takashi Tsukagoshi, Seokho Lee F Planetary systems
are thought to be born in protoplanetary disks. Isotope ratios are a powerful tool for investigating the material origin andevolution from molecular clouds to planetary systems via protoplanetary disks. However, it is challenging to measure theisotope (isotopologue) ratios, especially in protoplanetary disks, because the emission lines of major species are saturated. We
developed a new method to overcome these challenges by using optically thin line wings induced by thermal broadening. Asa first application of the method, we analyzed two carbon monoxide isotopologue lines, 12 CO 3 2 and 13 CO 3 2, fromarchival observations of a protoplanetary disk around TW Hya with the Atacama Large Millimeter/sub-millimeter Array. The
12
CO/13 CO ratio was estimated to be 20 ± 5 at disk radii of 70 110 au, which is significantly smaller than the value observedlow-pressure and quiescent turbulent environments of the diﬀuse interstellar medium.

Dependence of Molecular Cloud Samples on Angular Resolution, Sensitivity, and Algorithms

Qing-Zeng Yan, Ji Yang, Yang Su, Yan Sun, Xin Zhou, Ye Xu, Hongchi Wang, Shaobo Zhang, Zhiwei Chen
F In this work, we investigate the observational and algorithmic eﬀects on molecular cloud samples identified from positionposition-velocity (PPV) space. By smoothing and cutting oﬀ the high quality data of the Milky Way Imaging Scroll Painting(MWISP) survey, we extract various molecular cloud samples from those altered data with the DBSCAN (density-based spatial
clustering of applications with noise) algorithm. Those molecular cloud samples are subsequently used to gauge the significance of sensitivity, angular/velocity resolution, and DBSCAN parameters. Two additional surveys, the FCRAO Outer Galaxy
Survey (OGS) and the CfA-Chile 1.2 m complete CO (CfA-Chile) survey, are used to verify the MWISP results. We foundthat molecular cloud catalogs are not unique and the boundary and therefore the number shows strong variation with angularresolution and sensitivity. At low angular resolution (large beam sizes), molecular clouds merge together in PPV space, while
low sensitivity (high cutoﬀs) misses small faint molecular clouds and takes bright parts of large molecular clouds as single ones.
At high angular resolution and sensitivity, giant molecular clouds (GMCs) are resolved into individual clouds, and their diﬀuse
components are also revealed. Consequently, GMCs are more appropriately interpreted as clusters or aggregates of molecular
clouds, i.e., GMCs represent molecular cloud samples themselves.

Two Candidate KH 15D-like Systems from the Zwicky Transient Facility

Wei Zhu, Klaus Bernhard, Fei Dai, Min Fang, J. J. Zanazzi, Weicheng Zang, Subo Dong, Franz-Josef Hambsch,
Tianjun Gan, Zexuan Wu, Michael Poon F KH 15D contains a circumbinary disk that is tilted relative to the orbital
plane of the central binary. The precession of the disk and the orbital motion of the binary together produce rich phenomena in
the photometric light curve. In this work, we present the discovery and preliminary analysis of two objects that resemble the key
features of KH 15D from the Zwicky Transient Facility. These new objects, Bernhard-1 and Bernhard-2, show large-amplitude(> 1.5 mag), long-duration (more than tens of days), and periodic dimming events. A one-sided screen model is developed
to model the photometric behaviour of these objects, the physical interpretation of which is a tilted, warped circumbinary
disk occulting the inner binary. Changes in the object light curves suggest potential precession periods over timescales longer
than 10 years. Additional photometric and spectroscopic observations are encouraged to better understand the nature of theseinteresting systems.

ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – XI.
From inflow to infall in hub-filament systems

Jian-Wen Zhou et al. F We investigate the presence of hub-filament systems in a large sample of 146 active proto-clusters,
using H13 CO+ J=1-0 molecular line data obtained from the ATOMS survey. We find that filaments are ubiquitous in protoclusters, and hub-filament systems are very common from dense core scales (⇠0.1 pc) to clump/cloud scales (⇠1-10 pc). The
proportion of proto-clusters containing hub-filament systems decreases with increasing dust temperature (Td ) and luminosityto-mass ratios (L/M ) of clumps, indicating that stellar feedback from Hii regions gradually destroys the hub-filament systems
as proto-clusters evolve. Clear velocity gradients are seen along the longest filaments with a mean velocity gradient of 8.71 km
s 1 pc 1 and a median velocity gradient of 5.54 km s 1 pc 1 . We find that velocity gradients are small for filament lengths larger
than ⇠1 pc, probably hinting at the existence of inertial inflows, although we cannot determine whether the latter are driven bylarge-scale turbulence or large-scale gravitational contraction. In contrast, velocity gradients below ⇠1 pc dramatically increase
as filament lengths decrease, indicating that the gravity of the hubs or cores starts to dominate gas infall at small scales. We
suggest that self-similar hub-filament systems and filamentary accretion at all scales may play a key role in high-mass starformation.

The Pre-main Sequence: Challenges and Prospects for Asteroseismology

Konstanze Zwintz, Thomas Steindl F Stars do not simply pop up on the main sequence. Before the stars arrive on thezero-age main sequence, they form in the collapses of molecular clouds, gain matter through accretion processes, and compress
their cores until hydrogen can burn in full equilibrium. Although this evolutionary phase lasts a relatively short time, it is theimprint of these important physical processes that is often ignored by simplified assumptions. While asteroseismology oﬀers agreat tool to investigate these physical processes, studying pre-MS oscillations in turn has the potential to further advance thefield. Asteroseismology of pre-main sequence stars faces observational and theoretical challenges. The remnants of their birthenvironment which is often still surrounding the young stars causes variability that can interfere with the signal of pulsations.
The lack of long time-base satellite observations in addition limits the applications of the method. Theoretical models of premain sequence stars include several assumptions and simplifications that influence the calculation of pulsation frequencies andexcitation properties of pulsation modes. Keeping all this in mind, the prospects for pre-main sequence asteroseismology are
manifold. An improved understanding of the structure of young stellar objects has the potential to answer some of the open

The Pre-main Sequence: Challenges and Prospects for Asteroseismology

Konstanze Zwintz, Thomas Steindl F Stars do not simply pop up on the main sequence. Before the stars arrive on thezero-age main sequence, they form in the collapses of molecular clouds, gain matter through accretion processes, and compress
their cores until hydrogen can burn in full equilibrium. Although this evolutionary phase lasts a relatively short time, it is theimprint of these important physical processes that is often ignored by simplified assumptions. While asteroseismology oﬀers agreat tool to investigate these physical processes, studying pre-MS oscillations in turn has the potential to further advance thefield. Asteroseismology of pre-main sequence stars faces observational and theoretical challenges. The remnants of their birthenvironment which is often still surrounding the young stars causes variability that can interfere with the signal of pulsations.
The lack of long time-base satellite observations in addition limits the applications of the method. Theoretical models of premain sequence stars include several assumptions and simplifications that influence the calculation of pulsation frequencies andexcitation properties of pulsation modes. Keeping all this in mind, the prospects for pre-main sequence asteroseismology are
manifold. An improved understanding of the structure of young stellar objects has the potential to answer some of the open
questions of stellar evolution, including angular momentum transport and the formation of magnetic fields. While gyrochronology, for example, struggles to determine the ages of the youngest clusters, pulsations in pre-main sequence stars can function as
an independent age indicator yielding higher precision for single stars. The increasing interest of stellar astrophysics in general
to investigate the formation and early evolution of stars and planets illustrates the growing importance of pre-main sequence
asteroseismology.