Star Formation Newsletter#350 18-22
Yusuke Aso (KASI)Anisotropic Infall and Substructure formation in Embedded Disks
Aleksandra Kuznetsova,1, ⇤ Jaehan Bae,2 Lee Hartmann,3 and Mordecai-Mark Mac Low

1

1 American Museum of Natural History, 200 Central Park West, New York, New York, 10024, USA
2 Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 USA

2.05301v1 [astro-ph.EP] 10 Feb 2022

3 Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109

Ø 圧⼒バンプで円盤にリングができて惑星形成。
5
Submitted to ApJ
Ø 内部構造のある原始星円盤にガスフローß不均⼀落下が早期の内部構造を作る可能性。
RWI: launch and saturation
ABSTRACTØ 確率的な⾓運動量降着などを考慮し、円盤内輸送とダストトラップを調べる。

Infall Disk Structures

grasubR$/R& W W  W Wre.
The filamentary nature of accretion streams found around embedded sources suggest that protostellar
sure,disks experience heterogenous infall from the star-forming environment, consistent with the accretion
they
d
sun
in

e de stream
behavior onto star-forming cores in top-down star-cluster formation
simulations.
This may produce2
ss raccincdisk substructuresin the form of rings,
gaps, and spirals continuing
to be identified by high-resolution
Ȅ
time.
imagingsurveys in both embedded Class 0/I and later Class II sources. We present a parameter study
Ȅ
those
ep
physof anisotropic infall, informed by the properties of accretion flows onto protostellar cores in numerical
Ȅ
in
sun
d
d
c
d
c
sk in
simulations,and varying the relative specificangular momentumof incoming flows as wellas dtheir flow
Ȅ
er of
geometry. Our results show that anisotropic infall perturbs the disk and readily launches the Rossbyl gas
 sheet
nstielwave
It forms vortices at the inner and outer edge of the infall zone where material
Infall Disk Structures5
φ instability
kep
kep(RWI).

(δΣ/Σ)1!?
(δΣ/Σ)1!?

Ȅ

Ȅ



(δΣ/Σ)1!?
1

able to drive stresses corresponding to a viscosity parameter on the order of ↵ ⇠ 10 2 . The resulting
azimuthal shear forms robust pressure bumps that act as barriers to radial drift of dust grains, as
demonstrated by post-processing calculations of drift-dominated dust evolution. We discuss how aself-consistent model of anisotropic infall can account for the formation of millimeter rings in the outerdisk as well as producing compact dust disks, consistent with observations of embedded sources.

Ȅ R /R
Ȅ



Ȅ

Ȅ
Ȅ
Ȅ

cloud
stream1

gra(14)
subre.
Folsure,ocity
theymarilye dess ratime.
those
(15)
physsk in
nated
er of
ge in
l gas
ocity
nstielocity,

Ø FARGO3D, γ=1の冪exp tail Σ, 温度q=‒0.5、静⽔圧平衡、M =0.07 M , α粘性、R ‒ RcにUCMエンベロープ（R<R なので上下から）, R -R =ΔR, f =ΔR/R 。
Ø インフォールはt =1.5e4 yr続き、さらに2e4 yrまで計算。
Ø 𝑀̇ =1e-6 M /yr、M は~20%増加、初期R に対してR <R なら内円盤で、R >R なら外円盤でインフォール。
Ø 圧⼒勾配η=(u ‒v )/v , ストークス数Stでドリフト。
is deposited. These vortices drive spiral waves and angularインフォール領域（点線）の内と外の端に渦momentum transport, with some models
RWI: launch and saturation

sheet



Keywords: hydrodynamics — instabilities — planetary systems: formation — planetary systems:

ロスビー波不安定
protoplanetary disks




τ-2







1. INTRODUCTION

High-resolution imaging studies of protoplanetary

bedded planets (Bae et al. 2018; Disk Dynamics Collaboration et al. 2020). streamはα<~0.01相当の輸送
While direct detection of pro-

Anisotropic Infall and Substructure formation in Embedded Disks
Aleksandra Kuznetsova

2.05301v1 [astro-ph.EP] 10 Feb 2022

(27)

ties due to(28)

dust volume
tling (Birn-τ [yrs]

106
104
102

τ [yrs]τ [yrs](26)

scale due to

1の続き

3 Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109
Dust evolution timescales: prevs. post- infall(25)

and the visansport due
uced by theibed by the,3 and Mordecai-Mark Mac Low

2 Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 USA

108

he disk has
del in Birnt timescalest transport
he di↵usion,2 Lee Hartmann

1 American Museum of Natural History, 200 Central Park West, New York, New York, 10024, USA

Kuznetsova et al.

nfall models,1, ⇤ Jaehan Bae

t=0
τdiff

t = tep

Submitted to まとめ
ApJ

⼩さい粒⼦はØ 均⼀インフォールだとRc∝t3やダスト成⻑へのABSTRACT
インフォール
影響無し。
The filamentary nature で成⻑が加速。
of accretion streams found around embedded
sources suggest that protostellarØ インフォール領域の内と外に渦ができ、⼩質量

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
惑星のように渦状腕。
108
disk substructures in the form of rings, gaps, and spirals continuing to be identified by high-resolution
106
imaging surveys in both embedded Class 0/I and later Class II sources. We present a parameter study
104
of anisotropic infall, informed by the properties of accretion flows onto protostellar cores in numerical
内側にインフォーτdriftsimulations,andvaryingtherelative
specific
angularmomentumofincoming
flows
as
well
as
their
flow
2
10
100 μmルだとプロファイ
⼤きい粒⼦はイgeometry. Our results showthat anisotropic infall perturbs the disk and readily launches the Rossby
108
ルが急になり、実
wave instability (RWI). Itンフォール領域
forms vortices at the inner and outer edge of the infall zone where material
is deposited. These vortices drive spiral waves and angular momentum transport, with some models
106
効的に⼩さい円盤。
にたまる。
τgrowth
2
able
to
drive
stressescorresponding
toaviscosity
parameter
on
the
order
of
↵
⇠
10
.
The
resulting104
azimuthal shear forms robust pressure bumps that act as barriers to radial drift of dust grains, as
102mm
demonstrated by post-processing calculations of drift-dominated dust evolution. We discuss how a
30 60 90 120self-consistent150
30 60 90model
120 150of anisotropic infall can account for the formation of millimeter rings in the outer
R [au]
R [au]
Ø withダストトラップがsegregationを起こすな
disk as well as producing compact dust disks, consistentobservations of embedded sources.
μm

ど、⻑期の調査は今後。

Figure 10. Di↵usion (magenta), radial drift (orange), andcollisional growth (navy) timescales at t = 0 (left) and t = tep— instabilities — planetary systems: formation — planetary systems:(right) for sheet-like infall Keywords:
with Rc = Rd hydrodynamics
for 1 µm (top),
100 µm (middle), and 1 mm (bottom) dust.protoplanetary
Small particles
disks
initially show long time-scales for drift and di↵usion, but after the infall episode, disk perturbations and infall-induced
turbulence shorten ⌧di↵ , shorten ⌧growth inouter disk for
1.theINTRODUCTION
bedded planets (Bae et al. 2018; Disk Dynamics Colmicron-sized particles, and lengthen ⌧drift within the preslaboration et al. 2020). While direct detection of prosure bump region. Dottedlines show (vertical)
the locations
High-resolution
imagingstudies of protoplanetary

LETTER TO THE EDITOR

The width of Herschel filaments varies with distance
G. V. Panopoulou1,? , S. E. Clark2,3 , A. Hacar4 , F. Heitsch5 , J. Kainulainen6 , E. Ntormousi7 ,D. Seifried8 , and R. J. Smith9
1

California Institute of Technology, Mail Code 350-17, 1200 E. California Blvd, Pasadena, CA 91125, USAe-mail: panopg@caltech.edu
2
Department of Physics, Stanford University, Stanford, California 94305, USA
3
Kavli Institute for Particle Astrophysics & Cosmology, Stanford University, PO Box 2450, Stanford, CA 94305, USA
4
Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
5Department of Physics & Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
6
Chalmers University of Technology, Department of Space, Earth and Environment, 412 93 Gothenburg, Sweden
7
Scuola Normale Superiore di Pisa, Piazza dei Cavalieri, 7, 56126 Pisa, Italy
8
University of Cologne, I. Physical Institute, Zülpicher Str. 77, 50937 Cologne, Germany
9
Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road,
Manchester M13 9PL, UKØ ジーンズ解析ではフィラメント幅は柱密度と負の相関が予想されるが、Herschel観測と⽭盾。
Ø 広い柱密度にわたって統⼀的に説明できる理論はない。
Ø 観測バイアスの指摘：⻑さ⽅向の平均、どの半径までフィットするか、特に空間分解能。
Received 22 September 2021 / Accepted 15 November 2021
ABSTRACTØ Arzoumanian+'19との⽐較。
Filamentary
structures in nearby molecular clouds have been found to exhibit a characteristic width of 0.1 pc, as observedØ Herschel Gould Belt Context.
Survey,8分⼦雲、DisPerseでスケルトンを抽出。
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.
Ø 尾根から同じ距離を集めて強度の中央値を得る。背景と同じになったらrout。
Aims. We investigate how the recovered widths of filaments depend on the distance from the observer by using previously
publishedresults from the Herschel Gould Belt Survey.
Ø 背景を引いた後の半値全幅FWHM
、0.75
FWHM
内をガウス＋背景でobs
Methods. We obtained updated
estimateson the distances
to nearbyobs
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
フィットしたFWHM。
to treating them as a single population. We used these per-cloud filament widths to search for signs of variation amongst the cloudsof the previously published study.
2 of the mean per-cloud2)を使う。HPBW=18.2"。
Results.
find (FWHM
a significant dependence
filament width with distance. The distribution of mean filamentØ deconvolved FWHMdec=We√
obs ‒HPBW
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 e↵ects of resolution by performing a convergence study of a filament profile inØ Gaiaの３次元距離を使って再規格化。
the Herschel image of the Taurus Molecular Cloud. We find that resolution can severely a↵ect the shapes of radial profiles over theobserved range of distances.
Ø 幅が距離とともに増加。右図。
Conclusions. We conclude that the data are inconsistent with 0.1 pc being the universal characteristic width of filaments.
Ø Orion Bに40%あって、平均を上げている。
Key words. ISM: clouds – ISM: structure – stars: formation – local insterstellar matterØ TaurusとOrion BはKS検定でも完全に違う。
1. Introduction
pc with a spread of only a factor of 2 (Arzoumanian et al.
Ø 分散も距離とともに0.026-0.090
pcに渡って増加。 ⇠0.1
2011). This surprising finding has led to the proposition that

The formation of stars appears to occur preferentially within
filamentary structures (André et al. 2014; Könyves et al. 2015).
Special attention has been given to one morphological propertyof these structures: their width. In models of idealized hydrostatic cylinders, the radius is related to the stability of the structure (Ostriker 1964). In particular, the radius of the column

filaments show a characteristic width – one that is universal among clouds with drastically di↵erent properties (e.g.,star formation rate, mean column density, Arzoumanian et al.
2011; André et al. 2014). Recently, Arzoumanian et al. (2019)
extended the analysis of filament widths to a much larger sample of filaments in the Herschel Gould Belt Survey (HGBS),

バーは分布の１σ

LETTER TO THE EDITOR

The width of Herschel filaments varies with distance
G. V. Panopoulou1,? , S. E. Clark2,3 , A. Hacar4 , F. Heitsch5 , J. Kainulainen6 , E. Ntormousi7 ,D. Seifried8 , and R. J. Smith9の続き

1

California Institute of Technology, Mail Code 350-17, 1200 E. California Blvd, Pasadena, CA 91125, USAe-mail: panopg@caltech.edu
2
Department of Physics, Stanford University, Stanford, California 94305, USA
3
Kavli Institute for Particle Astrophysics & Cosmology, Stanford University, PO Box 2450, Stanford, CA 94305, USA
4
Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
5Department of Physics & Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599, USA
6
Chalmers University of Technology, Department of Space, Earth and Environment, 412 93 Gothenburg, Sweden
7
Scuola Normale Superiore di Pisa, Piazza dei Cavalieri, 7, 56126 Pisa, Italy
8
University of Cologne, I. Physical Institute, Zülpicher Str. 77, 50937 Cologne, Germany
9
Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford Road,
Manchester M13 9PL, UK

A&A 657, L13 (20Ø Taurusを遠くに持っていって分解能の効果を検証。
Ø 距離260 pc (分解能0.023pc), 423 pc (0.037 pc), 762 pc(0.067pc)。
Received 22 September 2021 / Accepted 15 November 2021
Ø FWHMobsは実際の観測より急に距離とともに増加。右図。
ABSTRACTØ 他の分⼦雲のフィラメント幅はTaurusとは異なる。
Context. Filamentary structures in nearby molecular clouds have been found to exhibit a characteristic width of 0.1 pc, as observed
Ø 幅の距離に対する増加を⼀部説明。
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.
Ø 距離に依らずFWHM
beamはフィラメントが分解されていobs
Aims. We investigate how
the~4
recoveredwidths of filaments depend on the distance from the observer by using previously publishedresults from the Herschel Gould Belt Survey.
ないことを⽰唆（数ビームの構造が得られやすい）。
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 opposedto treating them as a single population. We used these per-cloud filament widths to search for signs of variation amongst the cloudsof 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 distanceFig.approxi2. Comparison between the observed dependence of FWHMobs on
mately as 4 5 times the beam size. We examine the e↵ects of resolution by performing a convergence study of a filamentin (gray data points, symbols as in Fig. 1) and that of a radial
theprofile
distance
the Herschel image of the Taurus Molecular Cloud. We find that resolution can severely a↵ect the shapes of radial profiles
overthe
profile of a filament in Taurus, after reducing the angular resolution ofobserved range of distances.
the Herschel map to correspond to the physical resolution of a 18.200
Conclusions. We conclude that the data are inconsistent with 0.1 pc being the universal characteristic width of filaments.beam at the observed cloud distances (red diamonds). Dotted lines mark

Ø フィラメントは輝線で内部構造を⽰す。
Ø Herschelより分解能が良い⼲渉計観測では細く⾒える。
Ø 幅⽅向の分布は⼀つのフィラメントでも2-10倍違う。
Key words. ISM: clouds – ISM: structure – stars: formation – local insterstellar matterØ ガウシアンは必ずしもFWHMを復元しない。
Ø ウェーブレット分解など新しい道具に期待。
1. Introduction

The formation of stars appears to occur preferentially within
filamentary structures (André et al. 2014; Könyves et al. 2015).
Special attention has been given to one morphological propertyof these structures: their width. In models of idealized hydrostatic cylinders, the radius is related to the stability of the structure (Ostriker 1964). In particular, the radius of the column

1, 2, 4, and 5 times the beam size.

Taurus to achieve⇠0.1 pc with a spread of only a factor of 2 (Arzoumanian
et al. resolutions equivalent to 0.023 pc, 0.037 pc,
0.067 pc that(corresponding to a beam size of 18.200 at distances
2011). This surprising finding has led to the andproposition
260ispc,univer423 pc, and 762 pc). Using the same filament skelefilaments show a characteristic width – oneofthat
for all images,
sal among clouds with drastically di↵erent ton
properties(e.g., we constructed the filament’s radial profile,
determined etroutal.
, and measured FWHMobs . We refer the reader tostar formation rate, mean column density, Arzoumanian
Appendix
B for more details.
2011; André et al. 2014). Recently, Arzoumanian
et al. (2019)
Fig. 2samwe compare the FWHMobs obtained for this resoextended the analysis of filament widths to a muchInlarger
lution study
with the per-cloud mean FWHMobs , as a function
ple of filaments in the Herschel Gould Belt Survey(HGBS),

of fil
of 0.
or di
work

5. C

We h
(2019
of di
has b
mean
the e
not a
width
away
depe
of 0.1
by A
T
that
River
lution
times
resol
negli
in the
by co
beam
filam
than
linea
the b
the m
O
denc

iﬁcation
cribed incribed in
The vast
try only.

Testing Models of Triggered Star Formation with Young Stellar Objects in Cepheus OB4
1

Abby Mintz1,2, Joseph L. Hora2, and Elaine Winston2

Department of Astronomy, Yale University, 52 Hillhouse Ave., New Haven, CT 06511, USA; abby.mintz@yale.edu
2Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., MS-65, Cambridge, MA 02138, USA
Received 2021 June 18; revised 2021 August 19; accepted 2021 August 24; published 2021 November 11

Ø OB型星は⼩質量星形成を誘発、⾦属を作る、周囲の環境を変えるなど重要だが、埋もれて少な
Abstract
く遠く、観測が難しいので、⼩質量星形成への影響を調べる。
OB associations are home to newly formed massive stars, whose turbulent winds and ionizing ﬂux create H II regions
Ø 星⾵やイオン化フラックスが物質をHII領域の端まで押し、⼩質量星ができるというシナリオ。
rich with star formation. Studying the distribution and abundance of young stellar objects (YSOs) in these ionizedØ イオン化フロントが⾼密度分⼦領域に当たるところ（ピラー）でできるというシナリオ。
bubbles can provide essential insight into the physical processes that shape their formation, allowing us to test
modelsof star formation. In this work, we examined one such OB association, Cepheus OB4 (Cep OB4) pc
Ø Cepheuscompeting
OB4は1.1
kpcで、銀河の⾚道⾯から外れていて、イオン化バブルもあり、半径140—a well-suited region for studying YSOs due to its Galactic location, proximity, and geometry. We created aと⼤きい。早期型星クラスタBerkeley
59を含む。
photometric catalog from Spitzer/Infrared Array Camera (IRAC) mosaics in bands 1 (3.6 μm) and 2 (4.5 μm). We
Ø IRAC 3.6,
4.5 µmの新しいモザイクと2MASS,
supplemented
the catalog with photometry from the WISE
Wide-ﬁeld Infrared Survey Explorer, the Two Micron All Sky
Survey, IRAC bands 3 (5.8 μm) and 4 (8.0 μm), MIPS 24 μm, and MMIRS near-infrared data. We used color–colorからカタログを作る。
selections toMintz,
identify
821 YSOs, which we classiﬁed using the IR slope of the YSOs’ spectral energy distributions,Hora, & Winston
Ø DBSCAN:
隣⼈が多い
ﬁnding 67 Class I, 103 ﬂat spectrum,
569 ClassII, and 82 Class III YSOs. We conducted a clustering analysis of the
ものをクラスタとする。
Cep OB4 YSOs and ﬁt their spectral energy distributions. We found many young Class I objects distributed in thesurrounding shell and pillarsØas well
as a relative age gradient of unclustered sourcesin the bubble surrounding the OB
同じ数同じ⾯積のラン
association, with YSOs generally decreasing in age with distance from the central cluster. Both of these results
ダムとの⽐が最⼤とな
indicate that the expansion of the
H II region may have triggered star formation in CepOB4.
る範囲で隣⼈を探す。
α: ClassUniﬁed
III, ‒1.6,
Class
II,
Astronomy
Thesaurus
concepts: Young stellar objects (1834); Star formation (1569); Star forming regions
Ø ５クラスタ、63%が含(1565);
Protoplanetary disks (1300)‒0.3, Flat,
0.3, Infrared
Class excess
0/I (788);
Supporting material: ﬁgure set,まれる、メンバーはmachine-readable tables
445個から6個。
Ø 最⼤クラスタはBe 59play. The collect and collapse model 22,
12,that3.4µm andpositswinds
1. Introduction
supernovae caused by massive stars Be
can 59から広がるバブル
compress material
Many stars in our Galaxy formed in 領域の中⼼で、原始星OB associations, loose
sufﬁciently to trigger star formation by spurring gravitationalが少ない。
unbound systems of massive O and B stars(Lada 1999; Briceño
The Astronomical Journal, 162:236 (22pp), 2021 December

Mintz, Hora, & Winston

Figure 1. A color image of the Cep OB4 ﬁeld using the WISE 3.4, 12, and 22 μm images (blue: 3.4 μm, green: 12 μm, red: 22 μm). Berkeley 59—the cluster of earlytype stars—can be seen in the southern central region of the image. The shell of the molecular cloud surrounds most of the bright stars in the image. Pillars around theedges of the shell point in toward the OB association.

Infrared Science Archive. We queried the same region describedin Section 2.3 from the 2MASS All-Sky Point Source Catalog.
We obtained a 2MASS data set of 310,956 sources, with
144,065 within the region covered by the IRAC mosaics.

et al. 2007). The environments of OB associations, typicallyembeddedin giant
molecular
clouds (GMCs), are strongly
Figure 8. A histogramof the SED slopes
α of the YSOs.
The black dashed

Archive for Space Telescopes.3 The PanSTARRS archive wassearched for objects within 1″ of the positions of the YSOs
identiﬁed in Section 4. A total of 33 objects were found tomatch the positions of the YSO candidates identiﬁed from the
IRAC data. The r- and i-band optical photometry of thesesources was used in the SED ﬁtting described in Section 6.

collapse (Elmegreen& Lada 1977). This process would lead to the
2.5. MMIRS Near-infrared Imaging
presence
ofimages
YSOs
aroundNear-infrared
were obtainedat J, H, and Kthe
with theoutskirts of the H II regions,
3. Data Reduction
MMT and Magellan Infrared Spectrograph (MMIRS; McLeod

Testing Models of Triggered Star Formation with Young Stellar Objects in Cepheus OB4

he complete set of plots of the YSO SED ﬁts are available in the ﬁgure set). The leftmost SED is a Class I YSO, themost SED is a Class II YSO. The black points represent the photometric data and uncertainty. The black line indicates
all model ﬁts with ∣D 2  D 2best∣  3.

1

ble.)

The Astronomical Journal, 162:236 (22pp), 2021 December

Abby Mintz1,2, Joseph L. Hora2, and Elaine Winston2

Department of Astronomy, Yale University, 52 Hillhouse Ave., New Haven, CT 06511, USA; abby.mintz@yale.edu
2Center for AstrophysicsMintz,| Harvard
Hora, & Winston & Smithsonian, 60 Garden St., MS-65, Cambridge, MA 02138, USA
Astronomical
Journal,162:236(22pp), 2021
Received 2021 June 18; revised 2021 AugustThe19;
accepted
2021
August24;December
published 2021 November 11の続き
Mintz, Hora, & Winston

AbstractØ 衝撃波がガス、ダスト
OB associations areØhome
to newly formed massive stars, whose turbulent winds and ionizing ﬂuxを吐き出したピラーに
create H II regions
クラスタでない
rich with star formation. Studying the distribution and abundance of young stellar objects (YSOs) in these ionized
ものの分布。
原始星。
bubbles can provide essential insight into the physical processes that shape their formation, allowing
us to test
Be59中⼼から遠competing models Øof starformation. In this work, we examined one such OB association, Cepheus
OB4 (Cep OB4)
Ø ピラーから求めた拡⼤—a well-suited regionいほど若い。
for studying YSOs due to its Galactic location, proximity, and geometry. We created a
時間1.6 MyrはBe 59のphotometric catalog from Spitzer/Infrared Array Camera (IRAC) mosaics in bands 1 (3.6 μm) and 2 (4.5 μm). We
ß衝撃波の拡⼤。
年齢2
supplemented the catalog
with photometry from the Wide-ﬁeld Infrared Survey Explorer, the Two
MicronMyrに合う。
All Sky
Survey, IRAC bands 3 (5.8 μm) and 4 (8.0 μm), MIPS 24 μm, and MMIRS near-infrared data. We used color–color
selections to identify 821 YSOs, which we classiﬁed using the IR slope of the YSOs’ spectral energy distributions,ﬁnding 67 Class I, 103 ﬂat spectrum, 569 Class II, and 82 Class III YSOs. We conducted a clustering analysis of the
Cep OB4 YSOs and ﬁt their spectral energy distributions. We found many young Class I objects distributed in thesurrounding shell and pillars as well as a relative age gradient of unclustered sourcesin the bubble surrounding the OB
association, with YSOs generally decreasing in age with distance from the central cluster. Both of these results
regionhave triggered star formation in CepOB4.
indicate that the expansion of the H IIØ
Be may59付近のed by the SED ﬁtting for all of
SOs in the clusters near Be 59.
he histograms are overlapping
Figure a18. Near-infrared (left) and optical (right) color–magnitude diagrams of our YSOs. PMS isochrones of various ages from Siess et al. (2000) are plotted in bothend in each of the samples,evious studies as discussed
ﬁgures.inIn the NIR CMD, we show the positions of stars of various masses on the 2 Myr PMS isochrone—shown as white stars outlined in red. In the optical CMD,

we show the stars’ full evolutionary tracks—shown as solid red curves. A main-sequence isochrone of 2 Gyr from Girardi et al. (2002) is shown in the optical CMD.
The YSOs have been dereddened using the NICER extinction maps from Lombardi & Alves (2001). All of the isochrones and evolutionary tracks have been shifted

the assumed distance to Cep OB4 of 1.1 kpc.
Be 59 and in theusing
regionFigure 16. The distribution of unclustered YSOs. The top panel shows theClass I and ﬂat spectrum
Class I/Class II (CI/CII) ratio of YSOs in annular bins as a function of
the bubble, and many atprojected distance from the center of the Be 59 cluster found in Section 5.1.
ure 12. The exception to
The red horizontal line indicates the CI/CII ratio of sources in the three centralclusters. The value in the rightmost bin—marked by a red square—is undeﬁned
Class I and ﬂat spectrum
as there were no Class II sources in the ﬁnal bin, and it is set to the same valueof these appear to be
as the previous bin. The bottom panel shows the density of the unclusteredebula to the west of the
YSOs, normalized by the area in each annulus covered by the IRAC 3.6 μm
hat the stellar winds andmosaic. Both of these distributions provide evidence that many of theunclustered YSOs in the region’s center may have formed in the central
ispersed. Because of theclusters, and there is an age gradient with a higher fraction of younger YSOs atd the location relative togreater distances from Be 59, as described in Section 5.2.
nd distribution of young
mplicated than a simple
Appendix C on the entire WISE catalog queried as described inm the Be 59 cluster.
Section 2.3. We identiﬁed 169 additional YSOs not found ind evolutionary stages ofthe selection described in Section 4. All of these YSOs wereion, we preliminarily ran
d in Section 4.2 andlocated around the border or beyond the area covered by the

The Astronomical Journal, 162:236 (22pp), 2021 December

Mintz, Hora, & Winston

Uniﬁed Astronomy Thesaurus concepts: Youngobjects (1834); Star formation (1569); Star forming regions
Classstellar
I, Flatもイ(1565); Infrared excess (788); Protoplanetary disks (1300)

15

オン化シェルが残る反射星雲に
ある。

⾚棒が
ピラー

Supporting material: ﬁgure set, machine-readable tables
1. Introduction

play. The collect and collapse model posits that winds andsupernovae caused by massive stars can compress material
Many stars in our Galaxy formed in OB associations, loose
sufﬁciently to trigger star formation by spurring gravitational
unbound systems of massive O and B stars (Lada 1999; Briceño
collapse (Elmegreen & Lada 1977). This process would lead to the
et al. 2007). The environments of OB associations, typicallyFigure 12. Four examplesof identiﬁed YSOs
in moleculararoundpillars. The YSOs
are coloredby evolutionary ofclassiﬁcationa color image ofII overregions,presenceoflocated
YSOs
theoutskirts
the andHplotted
2MASS H band 1.65 μm (blue), IRAC 3.6 μm (green), and IRAC 4.5 μm (red). The legends in the panels on the left also apply to the panels on the right in the sameembedded in giant molecular clouds (GMCs), are strongly
row. Pillars such as the ones visible in these images form when the ionizing winds from Be 59ʼs massive stars evacuate gas and dust around the cluster, leaving only

Figure 19. The spatial distribution of YSOs in Cep OB4 plotted over the IRAC 3.6 μm image. Here, we show the YSOs identiﬁed in Section 4 as well as those
identiﬁed using the larger region queried from the WISE catalog as described in Section 7.2. The YSOs are colored by their spectral type. We see numerous young
Class I and ﬂat spectrum YSOs toward the outskirts of the cluster and fewer inside the dense border of the H II region, indicating that there may have been likely
continuing star formation before the creation of the ionized bubble.

Figure 17. The location and direction of some of the pillars in Cep OB4 plotted over the WISE 12 μm image. The dotted red lines begin at the base of the pillars (asindicated by the perpendicular line segment) and follow the pillar orientation to the center of region. The YSOs (including the WISE-only YSOs discussed in
Section 7.2) are plotted with shapes and colors corresponding to their evolutionary classiﬁcation as in Figure 12. The O stars in the region are plotted as blue x’s
outlined in white. It appears that most of the pillars were exposed by a shock wave originating from Be 59—likely from one or all of the O stars in that region.

arXiv:2202.04264v1 [astro-ph.GA] 9 Feb 2022

Molecular Clouds Associated with H II regions and Candidates
within l = 106.65 to 109.50 and b = 1.85 to 0.95
Chun-Xue Li1,2 , Hong-Chi Wang1,2 , Yue-Hui Ma1 , Miao-Miao Zhang1 , Chong Li3,4 , andYu-Qing Zheng1
Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of
Sciences, 10 Yuanhua Road, Qixia District, Nanjing 210033, P. R. China; hcwang@pmo.ac.cn
2
School of Astronomy and Space Science, University of Science and Technology of China, 96 JinzhaiRoad, Hefei 230026, P. R. China
3
School of Astronomy and Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing 210023,
P. R. China
4
Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of
Education, Nanjing 210023, P. R. China
1

Received 20XX Month Day; accepted 20XX Month Day

Abstract 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,the emission 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 the 13 CO data.
The median excitation temperature, length, line mass, line width, and virial parameter ofthe 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 less than 2, suggesting thatthey are gravitationally bound and can lead to star formation. Nineteen H II regions or
candidates have previously 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
and molecular clouds as evidence for association, and raised temperature and velocity
broadening as signatures of interaction, we propose that 12 H II regions/candidates areassociated with their surrounding molecular clouds. In the case of the H II region of S142,
the energy of the H II region is sufficient to maintain the turbulence in the surrounding
molecular gas.

Purple Mountain Observatory 13.7 m
CO同位体J=1-0銀河⾯サーベイl=107-110°。
４つの分⼦雲。２５個のフィラメント。
８個のフィラメントが束縛。
１９個のHII領域。
形と速度から分⼦雲とHII領域の関連を調べ、温度上昇と速度幅上昇から相互作⽤を調べ、１２個のHII領域は分⼦雲に付随。
S142というHII領域はそれを囲む分⼦雲の乱流を維持できるエネルギーを持つ。

Star Formation Triggered by the Expanding Bubble S111
Bhaswati Mookerjea

Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
Received 2021 September 6; revised 2021 November 29; accepted 2021 November 30; published 2022 February 8

Abstract
This paper investigates the impact of radiative and mechanical feedback from O-type stars on their parent
molecular clouds and the triggering of formation of a future generation of stars. We study the infrared bubble S111
created by the embedded massive stellar cluster G316.80–0.05. A signiﬁcant fraction of gas in shells created due tothe 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 mostdominant species. We have used velocity-resolved maps of the 2P3/2 → 2P1/2 transition of [C II] at 158 μm, theJ = 2–1 transition of 13CO and C18O, and the J = 1–0 transition of HCO+ to study the rim of the bubble S111 thatpartly 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−1, 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 hydrogen ionization and dust-processed radiation. Among the far-infrared sources located incompressed shells, we ﬁnd the core G316.7799–0.0942 to show broad spectral features consistent with outﬂow
activity and conclude 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 triggering the current star formation activity in the region.
Uniﬁed Astronomy Thesaurus concepts: Interstellar medium (847); Stellar-interstellar interactions (1576)

O型星が周囲の分⼦雲での星形成を誘発を調べるためにG316.80-0.05が作った⾚外バブル
S111を研究。シェルがG316.80-0.05からの輻射で光解離。CII 158 µmなどでバブルのリム
1. Introduction
attributed to the inhomogeneous density distribution that causesの⼒学を⾒ると、7km/sで膨張。HII領域の熱エネルギーの0.5-40倍のエネルギーが、⽔素
the ionization front to be distorted and enables leakage ofMassivestars play a dominant role in the injection of UVのイオン化とdust-processed輻射から来ている。シェルにある⾚外線源G316.7799-0.0942
ionizing photons to large distances from the embedded cluster asradiation into the interstellar medium (ISM) and of mechanicalevidenced by the presence of diffuse emission from the ionizedは分⼦流的な広い線幅で星形成を⽰唆。HII領域の年齢を考えると、現在の星形成の原因はenergy through stellar winds and ﬁnally through supernova
gas in S110 and S111 (Samal et al. 2018). The dust temperature
そのHII領域。
explosions.
The photoionization, radiation pressure, and stellar
winds from young O-type stars pump both energy andmomentum into the ambient material and disrupt the parent

distribution derived from the Herschel Hi-GAL (Molinari et al.
2010) continuum observations suggests that while the parental