Star Forma)on Newsle0er#281 6-10本目
麻生 有佑

AN ALMA SEARCH FOR SUBSTRUCTURE, FRAGMENTATION, AND HIDDEN PROTOSTARS IN
STARLESS CORES IN CHAMAELEON I-76d30m00s

Accepted by ApJ

徳田くんが発表済み

ABSTRACT
We present an Atacama Large Millimeter/submillimeter Array (ALMA) 106 GHz (Band 3) continuum survey of the complete population of dense cores in the Chamaeleon I molecular cloud. We
detect a total of 24 continuum sources in 19 diﬀerent target fields. All previously known Class 0 andClass I protostars in Chamaeleon I are detected, whereas all of the 56 starless cores in our sample areundetected. We show that the Spitzer +Herschel census of protostars in Chamaeleon I is complete,with the rate at which protostellar cores have been misclassified as starless cores calculated as <1/56,
or < 2%. We use synthetic observations to show that starless cores collapsing following the turbulent
fragmentation scenario are detectable by our ALMA observations when their central densities exceed∼108 cm−3 , with the exact density dependent on the viewing geometry. Bonnor-Ebert spheres, on
the other hand, remain undetected to central densities at least as high as 1010 cm−3 . Our starlesscore non-detections are used to infer that either the star formation rate is declining in Chamaeleon I
and most of the starless cores are not collapsing, matching the findings of previous studies, or thatthe evolution of starless cores are more accurately described by models that develop less substructure
than predicted by the turbulent fragmentation scenario, such as Bonnor-Ebert spheres. We outline
future work necessary to distinguish between these two possibilities.
Subject headings: ISM: clouds - stars: formation - stars: low-mass - submillimeter: ISM

LABOCA/APEX
870 um 73個

dmDec. (J2000)-77 30 00s-77d00m00s

iv:1604.04027v1 [astro-ph.GA] 14 Apr 2016

Michael M. Dunham1,2 , Stella S. R. Offner3 , Jaime E. Pineda4 , Tyler L. Bourke5 , John J. Tobin6 , Héctor
G. Arce7 , Xuepeng Chen8 , James Di Francesco9 , Doug Johnstone9,10 , Katherine I. Lee1 , Philip C. Myers1 ,Daniel Price11 , Sarah I. Sadavoy12 , & Scott Schnee13

1. INTRODUCTIONdm-78 00 00s

Dense molecular cloud cores are the eventual
birthplaces of stars (e.g., Beichman et al. 1986;
Di Francesco et al. 2007).
Sensitive (sub)millimeterbolometers with large instantaneous fields-of-view haveenabled rapid mapping of entire molecular clouds, and as
a result dense cores are often identified via their dust continuum emission (e.g., Motte et al. 1998; Shirley et al.
2000; Johnstone et al. 2000, 2001; Enoch et al. 2006,
2007; Sadavoy et al. 2010; Pattle et al. 2015; Salji et al.
2015; Könyves et al. 2015; Kirk et al. 2015).
Afteridentification, they are typically classified as protostellar
1 Harvard-Smithsonian Center for Astrophysics, 60 Garden
Street, MS 78, Cambridge, MA 02138, USA2or starless based on the presence or absence, respectively, of a young stellar object (YSO) detected in theinfrared (e.g., Benson et al. 1984; Beichman et al. 1986;
Myers et al. 1987; Jørgensen et al. 2008; Enoch et al.
2009) or a molecular outflow (e.g., Hatchell & Dunham
2009; Chen et al. 2010). Some authors identify a subsetof starless cores as “prestellar cores” if evidence existsthat they are gravitationally bound or unstable (seeDi Francesco et al. 2007; Ward-Thompson et al. 2007,
for reviews of this subject). In this work, we use theterm “starless core” to refer to any core not found to beshassociatedwitha protostar,
to s
11h10m00
11h00mwhere
00s protostar
10refers
50m00
a YSO still embedded in and accreting from its parent(J2000)dense core. We avoid R.A.
the term“prestellar” altogether
since we lack the data to evaluate whether each core is

ALMA FoV

Figure 1. APEX LABOCA 870 µm image of the Chamaeleon I cloud from Belloche et al. (2011b). The image is di

PROTOPLANETARY DISKS IN THE ORION OMC1 REGION IMAGED WITH ALMA
J. A. Eisner1 , J. M. Bally2 , A. Ginsburg3 , P. D. Sheehan1
Draft version April 13, 2016

Ø 太陽系も含め、典型的な星形成は高密度。
ABSTRACTØ ONC (d=400 pc), ALMA cycle 2, Trapezium(<1 My), ~1”, 230 GHz, CO 2-1, C18O 2-1。
We present ALMA observations of the Orion Nebula that cover the OMC1 outflow region. Our focus
ØGeMS~0.06”)も再解析して、HST
proplydsと合わせて1.3mmを調査。
in thispaperNIR
is on(Ks,compact
emission from protoplanetarydisks. We mosaicked a fieldcontaining ⇠ 600
18
near-IR-identified
young 47/593
stars, aroundwhich we can search for sub-mm emission
tracing dusty disks.
Ø 21/100 proplyds,
NIRを>4σ。38個はミリ波で初。CO,C Oは無検出。
Approximately
100sources are known proplyds identified with HST. =20
We detectcontinuum emission
Ø
JVLAで3.6,6cmがあればfree-freeも考慮、なければT
Kで円盤質量。
dust
at 1 mm wavelengths towards ⇠ 20% of the proplyd sample, and ⇠ 8% of the larger 7sample of near-IR
5

-5.33

-5.34

-5.34

-5.35

-5.35

-5.36

-5.36

δ (J2000)δ (J2000)

objects. The noise in our maps allows 4 detection of objects brighter than ⇠ 1.5 mJy, corresponding
to protoplanetary disk masses larger than 1.5 MJ (using standard assumptions about dust opacities
and gas-to-dust ratios). None of these disks are detected in contemporaneous CO(2-1) or C18 O(2-1)
observations, suggesting that the gas-to-dust ratios may be substantially smaller than the canonicalvalue of 100. Furthermore, since dust grains may already be sequestered in large bodies in ONC disks,
the inferred masses of disk solids may be underestimated. Our results suggest that the distribution of
disk masses in this region is compatible with the detection rate of massive planets around M dwarfs,
which are the dominant stellar constituent in the ONC.
Subject headings: Galaxy:Open Clusters and Associations:Individual: Orion, Stars:Planetary Systems:Protoplanetary Disks, Stars: Pre-Main-Sequence
-5.33

-5.37

-5.37

-5.38

-5.38

-5.39

-5.39

-5.40

-5.40

83.83

83.82

83.81
α (J2000)

83.80

83.79

83.78

83.83

83.82

83.81
α (J2000)

83.80

83.79

83.78

— Mosaicked image of the OMC1 region in 1.3 mm continiuum emission, obtained with ALMA. Known near-IR sources detected
are shown with red circles. Blue circles indicate emission detected above 4 towards known HST-imaged proplyds from Ricci
8). All but two of the proplyds in this field have known near-IR counterparts.

ected previously at 3mm (Eisner & Carpenter
undy et al. 1995). We thus detected millimetergth emission for the first time towards 38 starsNC.
the strong ionization field near the Trapeziums in circumstellar disks or outflows can emit freession. Contributions of millimeter-wavelength
emission must be accounted for in order to cortermine the flux arising from dusty disk matter.
ctrum of optically thin free-free emission is relflat compared to that of dust emission, and soions at cm wavelengths can be used to constrain
emission (e.g., Eisner et al. 2008).
ed previous observations of the ONC at cm waverom Felli et al. (1993a,b); Zapata et al. (2004);
et al. (2007) to search for free-free emission
r sample. Nine of the sources detected in ourbservations are also seen in these previous obserHowever previous surveys only constrained free-

free emission at the ⇠ 1 mJy level for most of our targets.
Given the roughly flat spectrum of optically thin free-freeemission, these measurements can only constrain contributions at ALMA wavelengths at approximately thesame level. Since our ALMA observations are sensitive
to emission at < 1 mJy, we need deeper cm-wavelength
observations to constrain the free-free emission well forour sample.
Sheehan et al. (2016) conducted a new survey of the
ONC with the JVLA, reaching sensitivities of . 30 µJy
at cm wavelengths. Their maps of 3.6 and 6 cm continuum emission cover the entire area of the ALMA mosaic
presented here. In addition to the 9 targets with cm emission noted above, the deeper cm-wavelength data reveal
free-free emission from five other sources in our sample.
The 14 objects with cm-wavelength detections are shownin Figure 3.
For these sources, we constructed a model that includes optically thick free-free emission past a turnover

1. INTRODUCTION

oplanetary disks are the birth-sites of planetarys, and the mass distribution of disks relates dito the masses of planets that may potentially
The minimum-mass solar nebula (MMSN) needed
the planets in our Solar System is likely between
d 0.1 M (e.g., Weidenschilling 1977; Desch 2007).
olution of disk mass with time provides a separate,planetary disks is optically thick even for masses
M . Observations at sub-mm and mm wavelengnecessary to measure optically thin dust emissio
hence to determine the total mass of dust in the
While disk masses have been well-studied i
density star forming regions (e.g., Andrews & W
2005, 2007; Andrews et al. 2013; Williams et al
Carpenter et al. 2014; Ansdell et al. 2015), theseSearch for associations containing young stars (SACY)

tions containing young stars (SACY)
VII. New stellar and substellar candidate members in the young associations?,??

Table 1. Summary of the P.
associations
in3thisElliott1,2 , studied
A. Bayo, C.work.
H. F. Melo1 , C. A. O. Torres4 , M. F. Sterzik5 , G. R. Quast4 , D. Montes6 , and R. Brahm7,8Ass.

Ass. ID1

Ø Young associa)onの小質量メンバー検出が目的。
Ø 2MASSのJ,H,Kと固有運動からcompanionを決定。

European Age
Southern
Ageref. Observatory,
No. of objectsAlonso de Cordova 3107, Vitacura Casilla 19001, Santiago 19, Chile

arXiv:1604.03550v1 [astro-ph.SR] 12 Apr 2016

e-mail: pe210@exeter.ac.uk
2School of 2,7
Physics, Universityof Exeter, Stocker Road, Exeter, EX4 4QL
AB DorABD
100-1501053Departamento
Argus
ARG
40-44
1,7 de Fı́sica
77 y Astronomı́a, Facultad de Ciencias, Universidad de Valparaı́so, Av. Gran Bretaña 1111, 5030 Casilla,
Valparaı́so,1,3,4,7
Chile
-Pic
BPC
21-26
69
4
Carina
CAR
35-45
1,3,7
Laboratório
Nacional48
de Astrofı́sica/ MCT, Rua Estados Unidos 154, 37504-364 Itajubá (MG), Brazil
5 35-42
Columba
COL
78
European 1,3,7Southern Observatory,Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany
6 5-10✏-Cha
ECH
1,5,7 de Astrofı́sica
24
Departamentoy Ciencias de la Atmósfera, Facultad de Ciencias Fı́sicas, Universidad Complutense de Madrid, 28040
Octans
OCT
30-40
1,6,7
62
Madrid, Spain
Tuc-Hor
THA
1,3,7
56
7 33-45
Instituto de Astrofı́sica,
Facultad de Fı́sica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul,
TW Hydrae
TWA
10-12
1,3,7
23
Santiago, Chile
8
Millennium
Institute
Astrophysics,
References. 1: Torres et al. (2006),
2: da Silva
et al. of(2009),
3: Bell Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chileet al. (2015), 4: Binks & Je↵ries (2014), 5: Murphy et al. (2013), 6:
Received
Murphy & Lawson (2015), 7: Torres
et al.4inFebruary
prep. 2016; accepted 7 March 2016

Ø 使えれば過去の測光、分光、力学も。
Ø 自分たちで高周波数分解能観測。HERMES/1.2
m Mercatorスペイン R=85000, FEROS/2.2 m
R=48000
ABSTRACT
sample size. However, we are limited in sensitivity to wide com-Ø RV, Na I (8194.8Å), K I (7699Å), Hα, Li I, T を調査。
Context. The young associations o↵er us one of the best opportunities to study the properties of young stellar and substellar objects
eﬀpanions depending on the positionof the source on the sky, its
and to directly image planets thanks to their proximity (<200 pc) and age (⇡5-150 Myr). However, many previous works have been
proper motion, and density oflimited
objects
in
the
field
of
view
(FoV),
to identifying the brighter, more active members (⇡1 M ) owing to photometric survey sensitivities limiting the detections ofas discussed in Section 3. The
targets
make up the sample Ø 既知同士で標準偏差companion間の差
lower
mass that
objects.
and their basic properties areAims.
listedin search
Table D.1.
ある主星We
the field of view of 542 previously identified members of the young associations to identify wide or extremely wide
(1000-100,000 au in physical separation) companions.
companionが14組。
Methods.
We combined 2MASS near-infrared photometry (J, H, K) with proper motion values (from UCAC4, PPMXL, NOMAD)
今回の方法
3. Searching for new members
as
very
wide
to identify companions in the field of view of known members. We collated further photometry and spectroscopy from the literature
速度も距離も一致。
and conducted our own high-resolutionØ
spectroscopic
observations for a subsample of candidate members. This complementarycompanionsで問題ない。
P. Elliott et al.: Search for associations containing young stars (SACY)
information allowed us to assess the efficiency of our method.

To identify very wide companions
weWe
used
the point
Results.
identified
84source
targets cata(45: 0.2-1.3 M , 17: 0.08-0.2 M , 22: <0.08 M ) in our analysis, ten of which have been identified
Tableof targets
theirproperties
for high-resolution
spectraanalysedwork.
fromspectroscopic
analysisin previous
young association
works.
For 33inofthis
these84, we were able to further assess their membership
logue 3.
ofSummary
2MASS (Cutri
et al.and
2003)
forderived
near-infrared
photometry
a varietymotionsof properties
emission, UV excess, H↵ , lithium and K I equivalent widths, radial velocities, and CaH indices).
(J, H, K). We combined this usingwith properfrom (X-ray
the naval
We derivea successrate of the
76–88%
for this technique based on the consistency of these properties.
observatory merged astrometric
dataset(NOMAD),
properConclusions.
Oncetheconfirmed,
thetargets
improveknowledge of the lower mass end
2MASS IDRV
Na I (8194.8)
K I (7699)
H↵identified in this
Li I work wouldTe↵ significantly
SpT
SpT
ref. ourObs.
motionextended catalogue(PPMXL),andUnitedStatesthesetargets
would
an
ideal
new
samplefortheidentificationand study of planets(km s 1 ) of the young(Å) associations.
(Å)Additionally,(Å)(mÅ) make(K)naval observatory (USNO) CCD astrograph catalogue (UCAC4)
around nearby young stars. Given the predicted substellar mass of the majority of these new candidate members and their proximity,(Zacharias
et
al.
2005;
Roeseretal.
2010;
Zacharias
et
al.
2012,
01334282-0701311-14.934±0.003
0.26±0.01
0.17±0.01 would 2.00±0.11
64±3for new
5830
G1planets.
1
HERMEShigh-contrast
imaging techniques
facilitate the search
low-mass
respectively).
01373545-0645375
11.689±0.002
0.329±0.026
0.210±0.003
1.202±0.101101±105200
G6
2HERMES
Keytowords.
data
analysis
open clusters
and associations:general 5900
proper motions
stars:and dynamics stars: low-mass
03281095+0409075
0.146±0.048
0.196±0.044
124±16F6
2 kinematics
HERMESOne aim of this 10.952±0.667
search was
producerobustdetectionlim- 2.727±0.329
04373746-0229282
22.047±0.031
1.052±1.162
0.769±0.034
3750
M1.1
3
HERMES
itsof our entire sample
out to 100,000
au in physicalsepara- -2.142±0.127 61±2301354915-0753470
0.69±0.09
...
3500
M4
4
FEROS
tion
from the known6.487±0.029
member. These1.21±0.08
limits will be0.69±0.05
used in fur- -0.06±0.0203074909-2750467
16.512±0.171
1.21±0.13-12.80±1.11
...
3500
M4
4
FEROS
ther
work as explainedin Introduction
Section 1.0.35±0.03
We first calculated
the an- -0.03±0.01
1.
stars withlatitudes shared similar Galactic kine04515223-4640497
51.188±0.019
0.49±0.05...
4800
K6 high 4Galactic FEROS
gular
query needed 24.339±0.025
to achieve a physicalsearch radius
out to 0.33±0.2207013945-4231370-0.001±0.002
0.45±0.07
...
4300
4
FEROS
matics. K408371456-5517343
0.70±0.10
.
K9
4
FEROS
The veryto firstmembersof 0.001±0.001
theTWparalHydrae
association,. .oneof 4850
100,000
au using the81.314±0.019
distance
the-0.15±0.07
source(eitherfrom
23485048-2807157
7.430±0.032. . .derived..
1.63±0.17140±105200 These
G8 young
2 stars have
HARPS
been identified using a variety of
the youngest(⇡10Myr)kinematicallyand .closest(⇡50
young associations,lax
ESA 1997; van Leeuwen
2007 orus-pc)
02455260+0529240
88.502±0.053...
0.912±0.039-2.462±0.216
...
3100
M1
2
HIRES
were identified
than twoa halfing the convergence method
Torres etmore
al. 2006).
Weand
then
con-decades ago (de la Reza properties (X-ray emission, lithium absorption, H↵ emission,commonGalactic
kinematics,
al. 1989).
Theauthors in
noted
that
handfulenergyof isolated
T Tauri(Bayoverted the 1:
apparent
sources
theVOSA
FoVa into
References.
Gray et magnitude
al.et(2006),
2:ofTany
conversion
fromspectral
distribution
et al. 2008),
3: Shkolnik
et al.visible,(2012), and
4: near-infrared photom-

Search for associations containing young stars (SACY)
VII. New stellar and substellar candidate members in the young associations?,?? の続き
P. Elliott1,2 , A. Bayo3 , C. H. F. Melo1 , C. A. O. Torres4 , M. F. Sterzik5 , G. R. Quast4 , D. Montes6 , and R. Brahm7,8

arXiv:1604.03550v1 [astro-ph.SR] 12 Apr 2016

1

European Southern Observatory, Alonso de Cordova 3107, Vitacura Casilla 19001, Santiago 19, Chilee-mail: pe210@exeter.ac.uk
2School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL
3Departamento de Fı́sica y Astronomı́a, Facultad de Ciencias, Universidad de Valparaı́so, Av. Gran Bretaña 1111, 5030 Casilla,
Valparaı́so, Chile
4
Laboratório Nacional de Astrofı́sica/ MCT, Rua Estados Unidos 154, 37504-364 Itajubá (MG), Brazil
5
European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany
6
Departamento de Astrofı́sica y Ciencias de la Atmósfera, Facultad de Ciencias Fı́sicas, Universidad Complutense de Madrid, 28040
Madrid, Spain
7
Instituto de Astrofı́sica, Facultad de Fı́sica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul,
Santiago, Chile
8
Millennium Institute of Astrophysics, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile

x: spec. binary
o: single spec.

Ø 新検出companionはRVが既知天体に一致。
Ø 小質量星は磁気ダイナモでUV, X線が増加。
à実際、8天体はUVが黒点線(↙︎)の中で、X線も強い。

Ø K IのEWが小さく、若いものが4天体。
ABSTRACTØ 重力を見るCaH2,
CaH3が既知に一致。
Context. The young associations o↵er us one of the best opportunities to study the properties of young stellar and substellar objects
poten)al
and to directly image planets thanksØ
to their(Liの減少やカタログ間の強度の違いにも言及。)
proximity (<200 pc) and age (⇡5-150 Myr). However, many previous works have been
to identifying the brighter, more active members (⇡1 M ) owing to photometric survey sensitivities limiting the detections ofMlimited
dwarfslower mass objects.
Received 4 February 2016; accepted 7 March 2016

Aims. We search the field of view of 542 previously identified members of the young associations to identify wide or extremely wide

(1000-100,000 au in physical separation) companions.
Methods. We combined 2MASS near-infrared photometry (J, H, K) with proper motion values (from UCAC4, PPMXL, NOMAD)
to identify companions in the field of view of known members. We collated further photometry and spectroscopy from the literatureand conducted our own high-resolution spectroscopic observations for a subsample of candidate members. This complementary
information allowed us to assess the efficiency of our method.
Results. We identified 84 targets (45: 0.2-1.3 M , 17: 0.08-0.2 M , 22: <0.08 M ) in our analysis, ten of which have been identified
from spectroscopic analysis in previous young association works. For 33 of these 84, we were able to further assess their membershipusing a variety of properties (X-ray emission, UV excess, H↵ , lithium and K I equivalent widths, radial velocities, and CaH indices).
We derive a success rate of 76–88% for this technique based on the consistency of these properties.
Conclusions. Once confirmed, the targets identified in this work would significantly improve our knowledge of the lower mass endof the young associations. Additionally, these targets would make an ideal new sample for the identification and study of planets
around nearby young stars. Given the predicted substellar mass of the majority of these new candidate members and their proximity,
high-contrast imaging techniques would facilitate the search for new low-mass planets.

Ø 小質量星は近傍の若い星周りの惑星をハイコント
ラストで撮影できる理想的なサンプルだろう。
IMFを更新オリジナル

Key words. data analysis open clusters and associations: general proper motions stars: kinematics and dynamics stars: low-mass

1. Introduction
The very first members of the TW Hydrae association, one of
the youngest (⇡10 Myr) and closest (⇡50 pc) young associations,were identified more than two and a half decades ago (de la Rezaet al. 1989). The authors noted that a handful of isolated T Tauristars with high Galactic latitudes shared similar Galactic kinematics.
These young stars have been identified using a variety ofproperties (X-ray emission, lithium absorption, H↵ emission,common Galactic kinematics, visible, and near-infrared photom-

propermotion)
motion)they
theysharesharewithwiththeir
theirassociatedassociatedprimary.
primary.
is isproper
limitofof100,000
100,000
meansatatthis
thispoipolimit
auaumeansWiththepropermotion,radialvelocityandeitherphoWith the proper motion, radial velocity and either a aphosensitivetoidentifying
wide
companisensitivetoidentifying
wide
companion
tometricororkinematic
kinematicdistance,
distance,thethe3D
3Dkinematics
kinematicscan
canbebetometric
analysisofofthe
theresultant
resultantdistribution
distributionis
analysis
derived.
However,young
movinggroup
membersarealsoderived. However, young moving group members are alsoWe
use
Figure3
todemonstrateWe
use
Figure3
todemonstratethclassifiedononthis
thisbasis,
basis,i.e.
i.e.looking
lookingforforcollections
collectionsofofobjects
objectsclassifiedtwodi↵erent
spatialscales(breakingtwodi↵erent
spatialscales(breakingsharingthesamegalactic
motion.Therefore
Thereforeweweneed
needtotoclarclarsharing
thesamegalactic
motion.
stratedclearlyclearlyininthe
theright
rightpanel.
panel.This
Th
strated
1,2?
3
ify
what
is
a
componentinamultiplesystemandwhat
ify what is a component in a multiple system and what is isP.
ElliottandA.
Bayo
spatialdensityofmembersin
BPMG
spatialdensityofmembersin
BPMG
1 European Southern Observatory, Alonsoanothermovinggroupmember.
member.
de Cordova
3107,
Vitacura
Casilla 19001, Santiago 19, Chile
anothermovinggroup
populationofofidentified
identifiedwide
widecompanicompa
2 School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL
populationTo
investigate
thiswelookedlookedatatthe
thedi↵erentdi↵erentscales
scalesofof
Toinvestigate
thiswe
3 Instituto de Fı́sica y Astronomı́a, Facultad de Ciencias, Universidad de Valparaı́so, Av. Gran Bretaña 1111, 5030 smaller)
smaller)
is
not
just
a
continuation
is
not
just
a
continuationof
Casilla, Valparaı́so, Chilephysicalclustering
clusteringwithin
withinthe
theBPMG.
BPMG.We
Wecannotcannotuse
useproprophysicalsmallerscales.
Thesewidecompanionsmaller scales. These wide companions
jectedseparations
separationsfrom
fromspatial
spatialpositions
positionsforforthis
thisanalysis
analysisasas
jectedulation,their
theirseparation
separationdistribution
distributionisi
ulation,theproximity
proximityofofthe
thestarsstarsmeans
meansthethegroupgrouphashassignificant
significant
theAccepted 2016 April 18. Received 2016 April 14; in original form 2016 March 15
physicalprocess.
physical process.
depth(in(ingalactic
galacticco-ordinates:
co-ordinates:X⇡160,
X⇡160,Y⇡100,
Y⇡100,Z⇡45
Z⇡45
pc).
depth
pc).
Wecan,
can,however,
however,use
usethethederived
derivedphotometricphotometricdistances
distancestotoWe
known
membersandperform
queries
3Dspatial
spatialvolume.
volume.
known
membersandperform
queriesinin
aa
3D
ABSTRACT
6 6 RESULTSRESULTS
analysispresented
ininLarson(1995)
Thisis issimilar
similartotothe
analysispresented
Larson(1995)
TheThis“in-situ”
formation
ofthe
very
wide binaries
is hardto
explainas their physicalseparationswherearebeyondthe typicalsize ofaaabreakcollapsing
cloud
core (⇡5000-10,000au). Here wetheidentified
ofofobwhere
theauthors
authors
identified
breakininthe
thedensity
density
obInInthe
followingthefollowingsection
sectionwewepresent
presentanalan
00 00population
investigate
theformationof separationsuchsystems.
We
computestatistics
jects
a afunction
ininTaurus(58, ,jectsasas
functionofprocessofangular
angularseparation
Taurus(58
plicity
fraction(MF)
definedbyfraction (MF) defined bysuch⇡8000
astheau).
multiplicity
fraction( MF),ofcompanion-star
fraction ( CSF ) plicity
and physicalasasthe⇡8000au).However,
However,thedepth
depthofTaurus
Taurusis issignificantly
significantly
distributionofcompanions
inthe-Pictoris
movinggroup(BPMG).
We
Figure 1. Average detection probabilities (contours from separation
red,lower
BB++T T++Qupc)
Qu++QiQi++Se...
Se...
lower(⇡20(⇡20pc)ananangularangularquery
querywaswassufficient,sufficient,assuming
assuminga a
M
F F==
M
multiplicity
studiesinyoungerandolder
regions
and
show
that
the
100% to white, 0%) and detected companions (white stars) incompare
thefixed previous
S S++BB++T T++Qu++QiQi++Se...
fixeddistancedistancetotoallallsources.
sources.
Qu
Se...
dynamic evolution of a young population with a high degree of primordial multiplicity
physical separation versus mass-ratio space for the 49 systems.
For
ouranalysis
wewequeried
a a3030
pcpcvolume
aroundeachFor
ouranalysis
queriedvolumearoundeach
The solid, dashed and dash-dotted lines encompass areas canwithlead to a processed separation distribution, similar to the field population. The
bona-fide
member
ofof
the
BPMG
using
derived
X,X,Y Yandandbona-fide
memberthe
BPMG
usingthederivedandandthethecompanion-starcompanion-starfraction
fraction(Cof outercomponents
isattributed
tothe
the
dynamical
unfoldingof higher-orderdetection probabilities
90%, 50% and 10%, respectively. evolutionZgalactic
positions.
We
calculated
themagnitudeoftheZ
galactic
positions.
We
calculated
themagnitudeofthe(triple) systems; a naturalWe
ppconsequence of which is the formation of wide binaries.
BB++2T2T++3Qu
3Qu++4Qi
4Qi++5Se...
5Se..
2 2 (Y
2 2 (Z(XwideCSF
1 1 X
2 )2 )+
1 contain
1 or
2
di↵erencefor
(X
X
+to(Y
+ (Z
Z)22)2components
finddistancea distancestrong di↵erence
preference
systemsthree
more(>1000CSF==
1 Y2Y)2 )+
1 Z
S
+
B
+
T
+
Qu
+
Qi
+
Se...
S
+
B
+
T
+
Qu
+
Qi
+
Se..
betweenthe consideredmemberand anyofotherau: 11/ 14, 10,000
au: 6 / 7). bona-fide
We argue thatthe majority
wide binaries identified invalues(4.7< PL /P
We use the mid-value (26) of between the considered bona-fide member and any otherS <6 P.
ElliottandA.47).
Bayoyoung
movingingroups
areprimordial.
Under
the assumptionthat stellarwhere
populations,
S,S,B,B,T,T,Qu,
memberFor
components
that
where
Qu,Qi,
Qi,SeSerepresent
representtmemberinthisthisvolume.
volume.
Forwidewide
components
thatshare
share
this criterion to mask regions of detection probability spacewithinourgalaxy,have
statisticallysimilarprimordial
multiplicity,
we
can
infer
that
binary,triple,quadruple,
quintuple
statisticallysimilarradialvelocities
andpropermotionsandbinary, triple, quadruple, quintupleana
statistically similar radial velocities and proper motions andusing
previously identified companions in the system. For ex-paucityofwidebinariesin thefield
is the magnitude
result of dynamical
evolution.
Table 3. A summary of the type and fraction of multiple systems the without
respectively.
X,
Y
and
Z
values,the
distanceiscomrespectively.
ample,a systemhaswork.
a companion
with represent
a periodsystemof 100 day without X, Y and Z values, the distance magnitude is comsamples ifanalysedin thisS:B:T:Qu:Qi:Se
puted
from
the
angularseparation
ofofthecomponents
andAdditionally
puted
from
the
angularseparation
thecomponents
andAdditionallyweweuse
usethethephysicalphysicalses
Key
words:
binaries:
general–stars:
formation–stars:
pre-main-sequencethen
we maskregioncomponents
from theEquation
1. 4–2600 day. Masking in this casethe
distancetothebona-fide
member.
We
collected
all
of
the
semi-major
axis)versusCSF
the semi-major axis) versus CSFwhichwhicmeans setting a detection probability of 1. This is because the distance to the bona-fide member. We collected all of
thesedistancemagnitudes
togetherandanalysedtheresulgate
thedynamical
evolution
ofofmultip
these
distancemagnitudes
togetherandanalysedtheresulgate
thedynamical
evolution
multi
we use these probabilities to predict wherecoma the missingaarXiv:1604.06094v1 [astro-ph.SR] 20 Apr 2016

The crucial role of higher-order multiplicity in wide binary
formation: A case study using the -Pictoris moving groupØ 大きな固有運動、若くて近いàβ Pic (21-16 Myr, 43 pc)
Ø completenessの影響はない。
Ø 銀河運動(galac)c mo)on)à連星?, moving group?
Ø 距離分布を見ると2成分(近い成分がwide binary?)。

Tokovinin+14
コントア: 10, 50, 90%

連星検出<0.5 pc

raw kernel
raw / 確率SampleRef.

S:B:T:Qu:Qi:Se

Total MF

CSF

Ø BPMGはﬁeldよりClass 0に
wide binaries, i.e. Tokovinin et al. (2006); Tokovinin (2015),
近い。
and compare these with theoretical predictions of di↵erent
formation mechanisms.
Ø PerseusàTaurusàBPMGàIn this work we use the multiplicity census of the
Perseus region (Tobin et al. 2016), the -Pictoris moving
ﬁeldで最長最短が拡張。
group (hereafter, BPMG) and the field population (Raghavan et al. 2010; Tokovinin 2014a,b) to analyse the role ofØ >5000 AUは違う場所で形成。
higher-order multiple systems in the formation of wide binaries and population multiplicity.
Ø disruptedはﬁeldに一致。
Due to the long periods of wide multiple systems

panions would be and we have indirectly probed this space
1 INTRODUCTION
+0.09
with
stability 1arguments.
We repeated
all+0.15
objects
Classour
0 regions
36:43:15:6:0:033
0.64 this for0.91
0.05
0.09
+0.06
+0.27thentoPerseus
create a new set
detection
probability
arrays.
We
2 of 43:23:17:7:7:330
0.57
It is now
accepted
that 1.20
a significant
fraction of stars are
0.11
0.32
+0.04
+0.09
Taurus3
41:43:10:3:0:1
117 over0.59 the mass-ratio
0.78
averagedthese detection
probabilities
inborn in binary
or 0.04higher-ordersystems (Duchêne
0.07multiple
+0.06
+0.14
BPMG
4
35:35:24:6:0:0
0.65
1.02
0.02 evidence
0.06& Kraus
2013;
Reipurth
et +0.12al.
2014).
eachperiod bin because
there
is no49
significant
that However, the forma+0.07
BPMG (10,000 au)
4
44:42:11:3:0:0
57
0.56
0.73
0.05
0.08
tion ofmechanismfor
multiple&systemsthemass-ratio is4 a function
period(Reggiani
Meyeris still not very well un+0.06+0.08
BPMG (1000 au)
52:38:10:0:0:0
63
0.48
0.58
0.07
0.09
derstood.
The
complexinterplayof many physical processes
+0.01
+0.01
2013;
Tokovinin 2014b).
The field
5
56:33:8:3:0:0
454
0.44
0.58
0.02
0.04
leads
to
observed
distributionsofmultiple systems spanning
+0.01
+0.01
TheFigurefield
6
54:33:8:4:1:0
4847
0.46
0.65
2 shows our results based on the0.01
period distribu0.01
many orders of magnitude (Raghavan et al. 2010; Tokovinin
tion of systems in our sample. We used kernel density esti- 0
with periods,
P , spanning101010 day range).
a 1 confidence intervals from 2014b,
1000
bootstrappedsamples.
Note, themations(KDEs) to perform
this
analysis which
reducesthe
In particular, thefrom
formationbootstrapped uncertainties are indistinguishable
those of very wide multiple sysphase
e↵ect
when
binning
data,
see
for
details.with our current theory
calculatedusingbinomial
statistics
for
MFScott
valuesinmajority
tems(>10,000au)(2009)
is thehard
to explainof cases.
The
grey
dottedanddash-dotted
lines
are
the
medianofstarformation
becausecompanions
have separations be1: Chen et al. (2013), 2: Tobin et al. (2016), 3: Kraus et al.

(&30,000 yr) detecting significant orbital motion is not possible on short (<100 yr) time-scales. In fact we cannot directly

MN
M

The crucial role of higher-order multiplicity in wide binary
formation: A case study using the -Pictoris moving group の続き
P.
Elliott1,2? and A. Bayo3
1

European Southern Observatory, Alonso de Cordova 3107, Vitacura Casilla 19001, Santiago 19, Chile

arXiv:1604.06094v1 [astro-ph.SR] 20 Apr 2016☆:BPMG●:ﬁeld2 School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL

Ø Reipurth&Mikkola+12のmigra)on予想
à3重はwide(◯)高離心率(–)軽いものが遠い(◯)。
Ø Ma=Mb=Mc辺りにあって不安定àdecay

3 Instituto de Fı́sica y Astronomı́a, Facultad de Ciencias, Universidad de Valparaı́so, Av. Gran Bretaña 1111, 5030 Casilla, Valparaı́so, Chile

Accepted 2016 April 18. Received 2016 April 14; in original form 2016 March 15

ABSTRACTThe “in-situ” formation of very wide binaries is hard to explain as their physical separations are beyond the typical size of a collapsing cloud core (⇡5000-10,000 au). Here we
investigate the formation process of such systems. We compute population statistics
such as the multiplicity fraction ( MF ), companion-star fraction ( CSF ) and physicalseparation distribution of companions in the -Pictoris moving group (BPMG). We
compare previous multiplicity studies in younger and older regions and show that the
dynamic evolution of a young population with a high degree of primordial multiplicity
can lead to a processed separation distribution, similar to the field population. The
evolution of outer components is attributed to the dynamical unfolding of higher-order(triple) systems; a natural consequence of which is the formation of wide binaries. We
find a strong preference for wide systems to contain three or more components (>1000
au: 11 / 14, 10,000 au: 6 / 7). We argue that the majority of wide binaries identified inyoung moving groups are primordial. Under the assumption that stellar populations,
within our galaxy, have statistically similar primordial multiplicity, we can infer thatthe paucity of wide binaries in the field is the result of dynamical evolution.

Ø 遠い側はﬁeldではないが、近い側は既にﬁeld。à進化。

Key words: binaries: general – stars: formation – stars: pre-main-sequence

定性的なモデル:1 INTRODUCTION
wide binaries, i.e. Tokovinin et al. (2006); Tokovinin (2015),
and compare these with theoretical predictions of di↵erent
1. 円盤分裂とコア分裂
It is now accepted that a significant fraction of stars areformation mechanisms.
born in binary or higher-order multiple systems (Duchêne
In this work we use the multiplicity census of the
2. 角運動量交換で内側、ガスによるdecayで外側。
& Kraus 2013; Reipurth et al. 2014). However, the formaPerseus
region (Tobin et al. 2016), the -Pictoris movingtion mechanism for multiple systems is still not very well ungroup(hereafter,
BPMG) and the field population (Raghaderstood. The complex interplay of many physical processes
3. 外側は完全にdecayすることもあるので少ない。
van
et
al.
2010;
Tokovinin
2014a,b) to analyse the role ofleads to observed distributions of multiple systems spanningmany orders of magnitude (Raghavan et al. 2010; Tokovinin
2014b, with periods, P , spanning the 100 1010 day range).
In particular, the formation of very wide multiple systems (>10,000 au) is hard to explain with our current theoryof star formation because companions have separations be-higher-order multiple systems in the formation of wide binaries and population multiplicity.
Due to the long periods of wide multiple systems(&30,000 yr) detecting significant orbital motion is not possible on short (<100 yr) time-scales. In fact we cannot directly

RADIATION HYDRODYNAMICAL MODELS OF THE INNER RIM IN PROTOPLANETARY DISKS
M. Flock1,2 , S. Fromang2 , N. J. Turner1 , M. Benisty3

1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA

2 Laboratoire AIM, CEA/DSM-CNRS-Université Paris 7, Irfu/Service d’Astrophysique, CEA-Saclay, 91191 Gif-sur-Yvette, France and3 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France(Dated:)Draft version April 18, 2016arXiv:1604.04601v1 [astro-ph.EP] 15 Apr 2016

ABSTRACTØ <1 AU以内の惑星ß円盤の内縁。silicate
sublima)on半径とturbulent front半径。
Many stars host planets orbiting within a few astronomical units (AU). The occurrence rate and distributionsof masses and orbits vary greatly with the host star’s mass. These close planets’ origins are a mystery that
Ø 初めてhydrodynamicsを含めたモデリング。(結局hydrosta)cと変わらない)motivates
investigating
protoplanetarydisks’
Radiationhydrodynamical
models of theinnercentral
rim. regions. A key factor governing
13 the conditions near thestar is the silicate sublimation front, which largely determines where the starlight is absorbed, and which isØ dM/dtàΣ, αはT(~1000K)を境に2層(α~0.02, αmodeling
Radiationofradiation
the innerhydrodynamicalrim.
9 front
often called
theinner hydrodynamicalrim. We
presentmodels
the firstof the sublimationMRI
inout~0.001)。
in the disks around the young intermediate-mass stars called Herbig Ae stars. The models are axisymmetric,
and include starlight heating, silicate grains sublimating and condensing to equilibrium at the local, timedependent temperature and density, and accretion stresses parametrizing the results of MHD magneto-rotational
turbulence models. The results compare well with radiation hydrostatic solutions, and prove to be dynamicallystable. Passing the model disks into Monte Carlo radiative transfer calculations, we show that the models satisfy
observational constraints on the inner rims’s location. A small optically-thin halo of hot dust naturally arises
between the inner rim and the star. The inner rim has a substantial radial extent, corresponding to several disk
scale heights. While the front’s overall position varies with the stellar luminosity, its radial extent depends onthe mass accretion rate. A pressure maximum develops near the location of thermal ionization at temperatures
about 1000 K. The pressure maximum is capable of halting solid pebbles’ radial drift and concentrating themin a zone where temperatures are sufficiently high for annealing to form crystalline silicates.
Keywords: Protoplanetary disks, accretion disks, Magnetohydrodynamics (MHD), radiation transfer, nearinfrared emission, near infrared interferometry

Ø 赤い部分がスケールハ
イトの数倍の長さ。
Ø 内側から1. dust free,
2. dust halo, 3. inner rim,
4. shadow。

The pressure maximum collects solid particles, becausegasoutside the peak orbits slower than Keplerian, giving theThousands of the planets discovered with Kepler and
so We
they
drift theinward,Figure 5. Shape of theirradiation opticaldepth unityorbit
surfacewithinfor di↵erent
mass accretion rates
andstellarparticles
luminositiesa inheadwind
the R-Z plane.
conserve
correct while gas inside
ground-based
telescopes
an astronomical
unitof
aspect ratio to show the true geometry. The vertical thick bars mark the position of Rout
.
the
peak
orbitsfasterthan
Keplerian,yielding
tailwindthat
Radiationhydrodynamical
modelsof atheinner rim.
rim
their low-mass host stars (Benz et al. 2014; Lissauer
et al.
raisesparticles’
orbits(Weidenschilling
1977;
Haghighipour
2014; Johnson et al. 2013). In contrast, intermediate-mass& Boss 2003; Lyra et al. 2008, 2009). In particular, thestars around 2 Solar masses more often host super-Jovian
turbulent front can a↵ect the distribution of planet-forming
planets orbiting outside 1 AU (Bowler et al. 2010), while stars
solidsof ourin radiationintermediate-mass
Figure 13. Schematic structure
of
the
inner
rim
of
the
disk
aroundayoung
intermediate-massstar,summarizingtheresultshydrodynamical Herbig stars’ disks (Kretkeof more than 2.7 Solar masses have few or no super-Jovians
models. This meridional cross-section has the star and the system’s rotation axis at left. Vertical dotted lines divide the disk
from left toTheright,turbulent(1) optically-front’s surface density jump also
et into,al. 2009).
atthesedistances(Re↵ertetal.
2015).
Our
understandingof
thin gas with silicate vapor; (2) the silicate sublimation front, forming the inner rim of the optically-thick, dusty material — the starlight absorbed at the front
providesfavorable
conditions
for the growth of cyclonicheats the rim, making it vertically(3) planetary
the shadow castby the rim;origins
and (4) the
outer ondisk,ourwhoseslightly upward-curving surface lets it too see
the star.
theseextended;diversesystems’reliesknowlvortices,
which
can
further
concentratesolid particles along
The local pressure maximum just beyond the rim is a location where planet-forming solids can accumulate at temperaturesnear 1000 K.
edge of the central regions of the disks aroundyoung andstars.
ACKNOWLEDGMENTS
bastienall
Fromang
Mario Flockreceived funding
from(Bargethethe azimuthal
direction& Sommeria 1995; Lyra &One key location in the disks is theEuropean
silicate Research
sublimation
Council underEuropean
MactheLow
2012; Union’sFaure etSeval. 2014). Concentrating the solid
The authors thank Antonella
Wladbetween
Lyra, Rafael
front, the Natta,
boundarytransparent
rockvapor andan
enth
Framework
Programme(FP7/2007-2013)/grainERC Grant
Millan-Gabet, Gijs Mulders and Satoshi Okuzumi for usematerial
makes
growth efficient (Testi et al. 2014),
opaquedust
cloud,
andthus
betweenhotgas
lit
directlybytheagreement nr. 258729. This research was carried out in partful comments on the manuscript. We thank Andrea Mignone
andCalifornia
it could Institutelead to ofinTechsitu planet formation (Chatterjee &star andwarm
in the shadow& Monnierat the Jet Propulsion
Laboratory,
for supporting and advising
us withthematerial
newest PLUTO
code. (DullemondTan2014),
especiallyatthe inner disk (Boley et al. 2014).
nology, under a contract with the National Aeronautics and2010).
Parallel computations havebeen performed on the Genci suFurthermore,thepressuremaximum can halt young planets’Space
Administration
and
with
the
supportofthe
NASA
ExAnother
key
location,
lying
near
the
sublimation
front
but
percomputer ’curie’at theoutcalculation center of CEA TGCC
in
orbitalmigration(Massetetal. 2006; Matsumura et al. 2009;
oplanetResearch
programvia
grant
14XRP1420153.
Copydistinct fromit, isFor
thethisturbulent
front. This surface separates
and on the zodiac supercomputerat JPL.
work, SeLyra
et
al.
2010;
Kretke&Lin
2012; Bitsch et al. 2014; Hu
right
2015
California
InstituteofTechnology.
Government*
material ionized well enough to undergo magneto-rotationalacknowledged. et al. 2015). The turbulent front thus plays several roles ininstability (MRI) leading to turbulence,sponsorshipfrom neutral
mateplanetary systems’ development.
rial that is laminar or subject to weak turbulence driven by
1. INTRODUCTIONα =α だとpressure
maximumがなくなる。

dM/dtが大きいと長い。

L が大きいと外側。

Figure 8. Radial midplane temperature profile of model MD1e-8 (black solid
Figure 10. Inner dust ring radius over luminosity relation. The square, circle
OF THE INNER RIM IN PROTOPLANETARY DISKSline) and model RHD MD1e-8 (black RADIATION
dashed line). HYDRODYNAMICALThe red lines correspondMODELS
and rectangle symbols represent T Tauri, Herbig Ae and Herbig Be stars,
1,2
2
1 from Dullemondto the optical thin temperature of the gas (red dotted line) and theM.dust(redrespectively,
adapted& Monnier (2010) and Millan-Gabet
Flock, S. Fromang, N. J. Turner, M. Benisty3
1 Jet Propulsion
dashed line). The blue line shows the sublimation temperatureof Laboratory,
the dust. California etal. (2007).
We overplot
ourresults 91109,
by colored
Instituteof Technology,
Pasadena,
California
USA vertical lines, showing the
2 Laboratoire AIM, CEA/DSM-CNRS-Université Paris 7, Irfu/Service d’Astrophysique,out
CEA-Saclay,
91191
Gif-sur-Yvette,
Franceare,and LS11 (red),radial extent Rin
and
R
in
Table
2.
The
di↵erentmodelsrim
3 Université Grenoble Alpes, CNRS, IPAG,rim
38000
Grenoble,
FranceLS21 (green), MDe-9 (yellow), MDe-8 (blue) and MDe-7 (magenta). We note
(Dated:)out
for April
the MDe-X
Draftthatversion18, 2016models, the value of Rrim is similar.

の続き

Ø Herbig Aeの観測SEDと比較(i=45°)。
Ø 2 µmで中央値の半分ß磁気圧でrimが厚くなる？
Ø SEDだけではα =α は排除できない。
Ø T を変えると波長ごとに5-10%変化。

arXiv:1604.04601v1 [astro-ph.EP] 15 Apr 2016

vational
constraints, the models would favor a strong drop of
ABSTRACT↵out but theunits
changesremainsmall rate
andandwedistributions
cannot rule out the
Many stars host planets orbiting within a few astronomical(AU). Theoccurrenceof masses and orbits vary greatly with the hostpossibility
star’s mass. of
These
close planets’
originsa mysterya constant↵out fromtheareSED
alone.that
motivates investigating protoplanetary disks’ central
regions.
A keyTfactor
governingtheconditions
near the of emisFinally
model
=
800K
shows
a
6%
decrease
MRI
star is the silicate sublimation front, which largely
determines
whereasthethestarlight
is absorbed,
and whichis radially
sion
at
4
microns
surfacedensity
jump
in modelingout of the sublimationmoves
often called the inner rim. We present the first radiation hydrodynamical
front
outward,a↵ecting
thestars.
emission
at longer
wavelengths. Modelin the disks around the young intermediate-massstars called
Herbig Ae
The models
are axisymmetric,
TMRI = 1200K
shows toa small
increase
5%timeat 2 microns
and include starlight heating, silicate grainsMRI
sublimating
and condensing
equilibrium
at the oflocal,
dependent temperature and density, and accretionbut
stressesparametrizing
magneto-rotationala largerdecreasetheofresults
10% ofatMHD
5 micronscompared to model
turbulence models. The results compare well withradiationhydrostatic
MD1e-8with
TMRI =solutions,
1000K.and prove to be dynamicallystable. Passing the model disks into Monte Carlo radiative transfer calculations, we show that the models satisfy
observational constraints on the inner rims’s location. A small optically-thin halo of hot dust naturally arises
7.3. corresponding
Rim radius to several disk
between the inner rim and the star. The inner rim has a substantial radial extent,
scale heights. While the front’s overall position varies
the stellar
luminosity,
its radial extent
depends
As with
we haveseen,
the sublimation
front
takesona pointed
the mass accretion rate. A pressure maximum develops near the location of thermal ionization at temperatures
shape spread over several pressure scale heights in radius. It
about 1000 K. The pressure maximum is capable of halting solid pebbles’ radial drift and concentrating themis forthus
not straightforward
tosilicates.
define the exact radial positionk et al.
in a zone where temperatures are sufficiently highannealing
to form crystalline
of
the
rim.
In
this
section,wethe observational
deKeywords: Protoplanetary disks, accretion disks, Magnetohydrodynamics (MHD), compareradiation transfer,
nearFigure 9. SED of the sample of Herbig stars infrared(median emission,
spectral type
A6)
byterminedradii
presented
byMillan-Gabetetal.
(2007)
andnear infrared interferometry
Mulders & Dominik (2012) (black lines) with the upper and lower quartile
Dullemond & Monnier (2010) with the rim radial extent Rinrim(gray shade). The SED of model LS21 is shown with the pure dust component
and Routfromourmodels
(see
Table
2).
As
shown
on
Fig.
10,
(solid blue line) and with including an additional
gas component (dashed
1. INTRODUCTION
The
pressuremaximum
collects
solidparticles,
becauserimline). The blue crosses show the seven individual wavelengths calculated forgas outside
peak orbits slower
thetheoreticalandtheobservational
rim thanradiiKeplerian,comparegivingvery thewell
Thousandsoftheplanets
discovered
withKeplerandour models.
particles
headwindso they wedriftexplored.
inward, while
gascomparinside
forofthe rangeof astars
luminosityThisground-based telescopes orbit within an astronomical unit
the peak once
orbits more
faster thanyieldinga tailwind thatdian, especially at twothe(Benzemission
is lower
theirmicrons,
low-mass where
host stars
et al. 2014;
Lissauer etison
al. highlights
thatKeplerian,
the actual
rim becomesmoreraisesparticles’
orbits(Weidenschilling
1977;
Haghighipour
by a factor of two. The
gas
only
contributesafew
percentof
2014; Johnson et al. 2013). In contrast, intermediate-massradially &extendedwithhighermass
accretion
rate,
as
shown
Boss 2003; Lyra et al. 2008, 2009). In particular, thearound 2 Solar masses more often host super-Jovian
additional flux in thisstars
regime.
bytheverticallengthofa↵ect
the barsin Fig. 10
for the MDe-X
turbulent
front canthe distributionof planet-forming
planets orbiting outside 1 AU (Bowler et al. 2010), while stars
in intermediate-mass
Herbigstars’ disks(Kretkemodels. solids
By contrast,
the actual ring
positionis determinedof morethan 2.7↵Solarand
massesno super-Jovians
7.2. E↵ect of accretion
heating,
T haveonfew
theorSEDout
et al. 2009).
The turbulentand
front’ssurfacedensity
jump also
byofthe central
star luminosity
agree
with
the systematicat these distances (Re↵ert
et MRI
al. 2015). Our understanding
providesfavorable
conditions
the that
growthofdid
cyclonic
diverse planetarysystems’relies on our knowlIn this section wetheseinvestigate
the e↵ectsof origins
the accretion
trend seenin thewhichobservations.
Wefornotewe
notinvortices,canfurther
concentratesolid
particles
alongedge ofcentralregionsof thethediskse↵ects
around allheating, ↵out and TMRI
onthetheSED.
Overallre-young stars.
clude thethee↵ectofaccretion
luminosityasthisremainssmall
azimuthal direction (Barge & Sommeria 1995; Lyra &One key
locationinthe
the hydrostatic
disks is the silicate
sublimation
main small. We compare
the
SED
of
model
for
the
consideredsystems& Concentrating
Dominik 2012).
Mac
Low 2012;
Faure(Mulders
et al. 2014).
the solid
front, the boundary between transparent rock vapor and an
material
makes
grain
growthefficient
et al.our2014),
MD1e-8 with the profile
of cloud,the radiationhydrodynamical
Overall, the SED and the position of the (Testi
rim from
modopaque dust
and thus between
hot gas lit directly by the
and
it
could
lead
to
in
situ
planetformation(Chatterjee&
model RHD MD1e-8,starusing
the simulation
outputwe(Dullemondobtained & Monnierels are in broad agreement with previously published models
and warm
material in the
shadow
Tan2014),
especially
at
the
inner
disk
(Boleyetal.
2014).
at the last timestep. 2010).
The two resulting SEDs are very close,by Dullemond& Monnier(2010); Mulders & Dominik (2012)
the pressure maximum can halt young planets’
Anotherbut doFurthermore,with di↵erences less than
5%.key location, lying near the sublimation frontwhich
notincludethegasthe
rim and ettheal.star.
orbital migration (Massetbetween
et al. 2006;
Matsumura
2009;As
distinct from it, is the turbulent front. This surface
4 separates
Similarly small changes
are
seen
for
model
↵
=
10
,
previous
modelshave
shown,
there
is
still
a
lack
emission
Lyra et al. 2010; Kretke & Lin 2012; Bitsch et al. 2014; Hu atoutmaterial ionized well enough to undergomagneto-rotational
et al.wavelength
2015). The turbulent
front athus
playsofseveralinwhich has a higher dust
density
at
the
outer
rim
position.
For
twomicronby roughly
factortwo. roles
Neither
instability (MRI) leading to turbulence, from neutral mate4
planetarysystems’development.
the case ↵out = 10 rialthethatemission
microns
is greaterby driventhe
is laminarator4 subject
to weakturbulence
bypresence of a small dust halo, the contribution of the gas,AN ALMA SEARCH FOR SUBSTRUCTURE, FRAGMENTATION, AND HIDDEN PROTOSTARS IN
STARLESS CORES IN CHAMAELEON I

arXiv:1604.04027v1 [astro-ph.GA] 14 Apr 2016

Michael M. Dunham1,2 , Stella S. R. Offner3 , Jaime E. Pineda4 , Tyler L. Bourke5 , John J. Tobin6 , Héctor
G. Arce7 , Xuepeng Chen8 , James Di Francesco9 , Doug Johnstone9,10 , Katherine I. Lee1 , Philip C. Myers1 ,Daniel Price11 , Sarah I. Sadavoy12 , & Scott Schnee13
Accepted by ApJ

ABSTRACT
We present an Atacama Large Millimeter/submillimeter Array (ALMA) 106 GHz (Band 3) continuum survey of the complete population of dense cores in the Chamaeleon I molecular cloud. We
detect a total of 24 continuum sources in 19 diﬀerent target fields. All previously known Class 0 andClass I protostars in Chamaeleon I are detected, whereas all of the 56 starless cores in our sample areundetected. We show that the Spitzer +Herschel census of protostars in Chamaeleon I is complete,with the rate at which protostellar cores have been misclassified as starless cores calculated as <1/56,
or < 2%. We use synthetic observations to show that starless cores collapsing following the turbulent
fragmentation scenario are detectable by our ALMA observations when their central densities exceed∼108 cm−3 , with the exact density dependent on the viewing geometry. Bonnor-Ebert spheres, on
the other hand, remain undetected to central densities at least as high as 1010 cm−3 . Our starlesscore non-detections are used to infer that either the star formation rate is declining in Chamaeleon I
and most of the starless cores are not collapsing, matching the findings of previous studies, or thatthe evolution of starless cores are more accurately described by models that develop less substructure
than predicted by the turbulent fragmentation scenario, such as Bonnor-Ebert spheres. We outline
future work necessary to distinguish between these two possibilities.
Subject headings: ISM: clouds - stars: formation - stars: low-mass - submillimeter: ISM
1. INTRODUCTION

Dense molecular cloud cores are the eventual
birthplaces of stars (e.g., Beichman et al. 1986;
Di Francesco et al. 2007).
Sensitive (sub)millimeterbolometers with large instantaneous fields-of-view haveenabled rapid mapping of entire molecular clouds, and as
a result dense cores are often identified via their dust continuum emission (e.g., Motte et al. 1998; Shirley et al.
2000; Johnstone et al. 2000, 2001; Enoch et al. 2006,
2007; Sadavoy et al. 2010; Pattle et al. 2015; Salji et al.
2015; Könyves et al. 2015; Kirk et al. 2015).
Afteridentification, they are typically classified as protostellar
1 Harvard-Smithsonian Center for Astrophysics, 60 Garden
Street, MS 78, Cambridge, MA 02138, USA
2 mdunham@cfa.harvard.edu
3 Department of Astronomy, University of Massachusetts,
Amherst, MA 01002, USA
4 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748, Garching, Germany
5 SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire SK11 9DL, UK
6 Leiden Observatory, Leiden University, P.O. Box 9513, 2300RA Leiden, The Netherlands
7 Department of Astronomy, Yale University, P.O. Box 208101,
New Haven, CT 06520, USAor starless based on the presence or absence, respectively, of a young stellar object (YSO) detected in theinfrared (e.g., Benson et al. 1984; Beichman et al. 1986;
Myers et al. 1987; Jørgensen et al. 2008; Enoch et al.
2009) or a molecular outflow (e.g., Hatchell & Dunham
2009; Chen et al. 2010). Some authors identify a subsetof starless cores as “prestellar cores” if evidence existsthat they are gravitationally bound or unstable (seeDi Francesco et al. 2007; Ward-Thompson et al. 2007,
for reviews of this subject). In this work, we use theterm “starless core” to refer to any core not found to be
associated with a protostar, where protostar refers to
a YSO still embedded in and accreting from its parent
dense core. We avoid the term “prestellar” altogether
since we lack the data to evaluate whether each core isbound or unstable.
While existing (sub)millimeter observations have been
extremely successful at finding cores, these relatively low
angular resolution single-dish continuum surveys havebeen unable to determine the detailed physical structure of starless cores, especially the substructures indicative of fragmentation that will eventually form multiple protostellar systems. Additionally, infrared ob-