Star Forma)on Newsle0er#275 46-50本目
麻生 有佑

The VLT/NaCo large program to probe the occurrence of
exoplanets and brown dwarfs at wide orbits⋆

arXiv:1510.08453v1 [astro-ph.EP] 28 Oct 2015

III. The frequency of brown dwarfs and giant planets as companions tosolar-type stars

M. Reggiani1, 2 , M. R. Meyer1 , G. Chauvin3 , A. Vigan4 , S. P. Quanz1 , B. Biller5 , M. Bonavita5, 6 , S. Desidera6 , P.
A&A p
3 , frequency
1 , dwarfs
11 toReggiani
et al.: Theof brown
and giant10
planets
companions
solar-type stars
Delorme3 , J. Hagelberg7, 17 , A.-L. Maire6 , A. Boccaletti8 M.
, J.-L.
BeuzitE. Buenzli
J. Carson, E. asCovino, M.
14 , G. Montagnier4 ,Feldt9 , J. Girard12 , R. Gratton6 , T. Henning9 , M.
Kasper13 , A.-M. Lagrange3 , D. Mesa6 , S. Messina
disk fragmentation) can actually form objects down to a few
1. Introduction
15
3
16
17
1
18,
Jupiter
Star19and planet formation
mechanisms thereplanet-formation
scenarios”
and gave
C. Mordasini , D. Mouillet , J. E. Schlieder, D. Segransan , C. Thalmann “standard, and
A. masses.
Zurlo
Binary systems have been observed and characterized for almost
fore overlap in the planetary-mass regime. Companions in this100 years (see e.g. Aitken 1935). Since the seminal works by mass range could be the lower mass tail of the stellar CMRD
Duquennoy&
Mayor(1991)
andFischer&Marcy(1992),
the1
as well as the higher mass end of the planet CMF, but theyInstitute for Astronomy (IfA), ETH, Zuriche-mail:reggiani@phys.ethz.ch
propertiesof stellar binaries have also been widely studied. One have usually been excluded by the statistical analyses of direct
2
Département d’Astrophysique, Géophysique etofOcéanographie,
Université
17 AlléedumassSix Août,4000 Liège, Belgium
the most interesting
parametersdeof aLiège,
binary systemis theimaging surveys. Diﬀerent features in the frequency of BD com3
ratio q = et
M2d’Astrophysique/M1 , defined as the ratioof the secondaryUJF-Grenoble1/CNRS-INSU, Institut de Planétologie
de Grenoble
UMR(M
5274,
38041
Grenoble,
France2 ) overpanions
and planetsas a function of mass and semi-major axis
4
the primary
mass (M1 ). The dedistributionof q UMR
values fora sample
Aix-Marseille Université, CNRS, LAM (Laboratoired’AstrophysiqueMarseille)
7326,
13388could
Marseille,
France diﬀerent formation mechanisms (see also
help distinguishofbinariesisthecompanion
mass-ratio
distribution(CMRD).
5
Brandt et al. 2014b). Although spectroscopy may help in invesInstitute for Astronomy, University of Edinburgh,Blackford Hill, Edinburgh EH9 3HJ, UK
Several surveys in the past decades focused on the detection of tigating whether a given detected object formed by one process
6
INAF – Osservatorio Astronomico di Padova, Vicolodell
Osservatorio
5,35122
Padova,Italystellar binaries with the purpose of characterizing the occurrence or another, large surveys could contribute in assessing whether a7Institute for Astronomy, University of Hawaii, 2680
Woodlawn
Drive,
Honolulu,
96822
of companions
and their
mass
distributionHI
bothin theUSA
field (e.g. stellar-like or planet-like formation process dominates the CMF
8
al. 2010;
Janson etFrance
al. 2012)
and in star forming re- in a given companion mass range.
LESIA, Observatoire de Paris Meudon, 5 Pl. J. Raghavan
Janssen, et92195
Meudon,
Italy
9
gions
Patience
et al. 2002).
Reggiani & Meyer (2013), as an
Max-Planck Institute for Astronomy, Königstuhl
17,(e.g.
69117
Heidelberg,
Germany
As a project within the VLT/NaCo large program (hearupdate of Reggiani & Meyer (2011), have shown that in the field after NaCo-LP, P.I. J. Beuzit, Desidera et al. 2015; Chauvin et al.
10
Department of Physics and Astronomy, Collegethe
ofCMRD
Charleston,Charleston,SC universal,
29424 , USAisconsistent
with
being
independentof
11
INAF Osservatorio Astronomico di Capodimonte
via Moiarello
16, 80131
Napoli,
Italy by the obser- 2015), the work presented in this paper represents the first atprimary
mass and separationin therange covered
tempt to place some constraints on the full CMF in the substellar
12European Southern Observatory, Casilla 19001,vations,
Santiago
19, beChileand canfit by a single power-law slope dN/dq ∝ qβ , regime. It takes into account both BDs and planets and makes use
13with β =± 0.29. Garching,
In addition, Germany
N-body simulations suggest of the results of most of the direct imaging surveys of solar-type
European Southern Observatory, Karl Schwarzschild
St,0.252, 85748
the CMRD
is onlyCatania,
modestly
by dynamics,
evenin planets
M.
Reggiani etaﬀectedal.: The frequencyof brown dwarfs
and giantas companions to solar-type stars
14
INAF – Catania Astrophysical Observatory, viathat
S. So
a 78, 95123
Italy
primaries
currently available. In Sections 2 and 3 we present ourdense clusters, as opposed to the semi-major axis (SMA) distri- model for the mass distribution of substellar companions and the15
Physikalisches Institut, University of Bern, Sidlerstrasse
5,CH-3012Bern,
Switzerland
obtained by using the COND evolutionary models. Dupuy et al.
bution(Parker&
Reggiani2013).
The
CMRD
therefore
seems
Monte
Carlo
tool that
we developed
to test it. Then,
16(2014) present
evidencefor simulationa substellar luminosity
probleminNASA Ames Research Center, Moﬀett Field, CA,2
to beUSAa good diagnostic for diﬀerent star formation mechanisms.
the predictions
from evolutionarymodels. The
lumi- (logcBD )we describe
the datasets
thatpredicted
we adopted
fora−log
the aanalysis(Sec17
which we estimate planet and BD masses could−in
While
distributions
massesand orbitalparametersnositiesare2 from
Geneva Observatory, University of Geneva, Chemin
destheMailettes
51, of
1290
Versoix,
Switzerland
2
α
2
σ
tion
4)
and
the
results
of
the
Monte
Carlo
simulations
based onBD
fact
be underestimated (Dupuy et al. 2014), which would make
BD
18
quite
well
establishedforstellarcompanions,
the
shape
of
the
BD dataBD 5).
Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago,
Chile
Finally,
discuss
our surveytheseresults
more (Section
constraining
regardlessthe wefrequencyof the results in Section 6
companion mass(CMF) Universidad
and of the SMA
19
mass
objects.
Although
the COND
models2thecloudless,α pl 7.
β pland36-D,summarize
conclusions
in Section
Millennium Nucleus “Protoplanetary Disk”, Departamento
defunction
Astronomía,de distribution
Chile,planetary
CasillaSantiago,
Chile
show
the
smallest
discrepancy
withtheobserved
luminosities
in the substellar and planetary mass regime is still poorly underpl
plcompared
to
the
DUSTY
models(Chabrier
et
al.
2000)
and
the
stood. The over 500 extrasolar planets discovered with theSaumon
ra- &Table
Planetandmodels.
BD distributions:
Marley1.(2008)
hybridThe DUSTY model
models values.
—
dial velocity (RV) method allowed astronomers to fit power-law
might be more appropriate for some of the higher mass (and presumably hotter) browndwarfs that we simulate. Howevertheslopes to the mass and semi-major axis distributions for planets
Parameter
Valueswith both families of evolutionary models lead toa
with masses between 0.3-10 M Jupiter and within ∼3 AU (seesimulations
e.g.
αBD
1.25
consistent results.
ABSTRACT
Fischer & Valenti 2005; Cumming et al. 2008). However, nothα pl-0.31bing guarantees that the same behavior holds at larger separa-BD,placBD pl50 AUc
4. Dataset
tions ortohigher
masses. Direct
imaging is aanddetection
methodContext. In recent years there have been many attempts
characterize
the occurrence
distributionof stellar, σbrowndwarf (BD) 1.68c
BDallowsto characterizelarge-separation
exoplanets.
InThethedatasetthat weusedtest the modelfor the substellar
β pl tovelocity
0.39b
and planetary-mass companions to solar-type stars,that
withtheusaimof constraining
formationmechanisms.
FromradialobserCMF
of thefortargetsof the NaCo-& all separationsc
past decade many direct imaging surveys (e.g. Lowrance etal.described in Section
fBD2 consisted
0.61[q=0.08-1]
vations a dearth of companions with masses between
10-40
M
has
been
noticedatclose
separations,suggestingthepossibility
BD
Jupiter
LP al.
(Chauvin et al. 2015; Desidera et al. 2015), a large observing
2005; Biller et al. 2007; Lafrenière et al. 2007; Chauvin et
f pl in the context
0.0329forVLT/SPHERE[1-13 M J ] & [0.3-2.5 AU]dprogram (ESO: 184.C-0157)
of theof a distinct formation mechanism for objects above
andHeinze
below
range.
2010;
etthisal. 2010;
Vigan
et discontinuity
al. 2012;at Biller
al. 2013;
scientific preparation.mThis
Fig. 1. Combined
substellar
CMF. Thelog M/Met
5 survey
M Jupiter⊙ =-2.3
minBDprogram is a direct imaging
Aims. We present a model for the substellar companion(CMF).
consistsof theofmtheplanet andBDstudy
providing a homogeneous
statisticallysignificant
is duethe opacityWahhaj
limit
for fragmentationthat seta minimum
Rameaumass
etal.tofunction
2013a;
et al.It2013;
Chauvinetmassal.superposition
2015;
80ofMthemaxBD
Jupiterfor objects formed through core fragmentation. The minimum mass is occurrence of giant planets
and BDs in wide (5-500 AU) orbits
Brandtetal.
2014a;
Bowler
et
al.
2015)
have
been
carriedcompanion mass distributions, assuming that we can extrapolate
velocity measured companion
massnearby
functionfor planets to 0.1 AU
aminassumed to thebe 5 Mradial
Jupiter in our model.
around young,stars.
BD It focused on a carefully selected◦outtoevaluatetheoccurrenceofgiant
planets
inwideorwith adeclinations
δ ≤ both
25 , agest ≤ 200
Myr,AU
10000
larger separations and the stellar companion mass-ratio distribution over all separations into the BDsample,
massregime.
ByBD usingthemaxplchosendistancesR-band brightnesses R ≤ 9.5 and with—exbits (10-500 AU). Besides a few planets (e.g. Kuzuhara etal. d ≤100 pc, mminpl theresults of the VLT/NaCo large program (NaCo-LP, 2013;
P.I. J. Rameau
L.interested
Beuzit)andcomplementaryarchivethat probe
occurrence
clusionbinariesandvisual binaries with separawe
run
Nthe
simulations
the survey,
in whichevery datasets
etin,al.
2013b)and ofbrowndwarfs(BDs)(e.g. of spectroscopic
BD,pl
m
0.1
x
M star
max
tion
<6”.
The
samplewas
initially
comprisedof84
targets,none
targetstar
israndomly
assignedanumberofplanets
andanumpl
of planets and BDs on wide orbits around solar-typestars,ber
place
some
constraintsonthe planet
andBD distributions.
Chauvinetweal.
2005b;
et al.
2010;
etPal.
2010;of which had been observedof BDs,based Biller
on Poisson
statistics
withMugrauer
mean P pl andBDamin plbefore in a planet survey. These stars—
werethen observed with
VLT/NaCoin theof
H bandforal.
planets
and Carson
BDs,
In caseprobability
Methods. We developed a Monte Carlo simulation
tool etto
predict
therespectively.
outcomeofthe
aPoissongiven
survey,dependingon
the shapethebetween
Wahhaj2011;
et al. 2013)detected,
many
surveyse
amax
rcutoend
ff
plof 16.5 nights. A complete descripa number
smaller than 0.5,
the nullnumberof planetsor BDsbe 2009
foundeccentricity
no returns
planetarycompanions.
The
results
cannotusedand 2013, for a totalthe
orbital parameter distributions (mass, semi-major axis,
andinclination).
the predictions
resultsof thetion of the samplewith
and its properties(distance,
age, mass) canfor the given staris zero.
However, if theComparing
star turns out to haveto fit are
power-laws
tothecanplanetary
distributions
beyondAU.
found inNotes.
Desidera(a)et Reggianial. (2015). The
summary(2013),
of the programone
or moreplanets(orBDs),
the mass
and semi-major
axis for10 be& Meyer
measured for stellar companobservations, we calculate how likely diﬀerent models
and
which
be ruled
out.
observations
is provided in Chauvinal. (2015).
As a (b) Heinze et al. (2010),
onesuggestof them is arandomly
selectedof
fromthe planet
input planet(or and of the ionsHowevereachtheytruncation
thesemi-major
but extrapolated
to theet BD
regime.

measured CMF but extrapolated to larger separatof course some caveats to these assumptions. ForØ binaryの伴星主星質量比q=M1/M2はM1に依らずstellar massではdN/
not take into account how gravitational instabilidq∝q^(0.25±0.29)。
cretion diﬀer in the distributions of orbital parame
The fact that there are multiple binary formatioØ VLT/NaCo large programなど観測感度の向上により、substellar側がわかってきた。
and that both planets and BDs migrate makes ev
complicated. In this paper we propose a simple,
and test whether it works.
Ø “stellar-like mechanism”でできるものをBD, “standard planet-forma)on
Instead of tryingscenarios”ででto fit the substellar CMF withlaw distribution (see e.g., Brandt et al. 2014b),
きるものを惑星と呼ぶ。
overall frequency of substellar companions to beØ Companion Mass func)onをsingle powerではなくBDと惑星の和と考える。
contributions:Ø モンテカルロで擬似サーベイ。

d N

Ø 検出感度は星からの距離で決まる
contrast curve (距離や年齢も考慮)。
Ø 観測は主にVLT/NaCo LP (δ<25°,
t<200 Myr, d<100 pc, R-band輝度<9.5, sepera)on<6”)で、substellarは47天体中無検出。過去のサーベイも追加して１99天体中3天体検出。

1 Moのとき。

=Cq d log q e
d log a,d N = C m d log m a d log afor BDs and planets, indicated with the “BD ”
scripts, respectively. q is the mass ratio, as defineαand β are the exponents of the power-law
major axis distributions (c.f. Cumming et al. 2008
and σ are the mean and the standard deviation
aration distribution, assuming it is log-normallyfor solar type primaries (see e.g. Raghavan et al.
C are normalization constants that can be obtai
surements of the BD and planet frequency fmasses and semi-major axes.
In this paper we assume values for the para
think are appropriate for solar-type primaries,

Results. Current observations are consistent with the proposedmodelthe2).CMF,
as longas a suﬃciently
smallno outerresult of the campaign,
substellartruncationcompanions were detectedBD) distributions(seeforSectionThe eccentricity
is randomly

The VLT/NaCo large program to probe the occurrence ofの続き
et al.: The frequency of brown dwarfs and giant planets as companions to solar-type stars
exoplanets and brown dwarfs at wide orbitsM.M.⋆Reggiani
Reggiani et al.: The frequency of brown dwarfs and giant planets as companions to solar-type stars

arXiv:1510.08453v1 [astro-ph.EP] 28 Oct 2015

III. The frequency of brown dwarfs and giant planets as companions tosolar-type stars
Ø 惑星のaの最大値を決めるr
cutoﬀを変え
1, 2
1
3
4
1
5
5, 6
6

て、3000回実行。NaCo-LPで無検出の確率は100, 30, 20 AUで、9, 45, 53%。

M. Reggiani , M. R. Meyer , G. Chauvin , A. Vigan , S. P. Quanz , B. Biller , M. Bonavita , S. Desidera , P.
Delorme3 , J. Hagelberg7, 17 , A.-L. Maire6 , A. Boccaletti8 , J.-L. Beuzit3 , E. Buenzli1 , J. Carson10 , E. Covino11 , M.
Feldt9 , J. Girard12 , R. Gratton6 , T. Henning9 , M. Kasper13 , A.-M. Lagrange3 , D. Mesa6 , S. Messina14 , G. Montagnier4 ,C. Mordasini15 , D. Mouillet3 , J. E. Schlieder16 , D. Segransan17 , C. Thalmann1 , and A. Zurlo18, 19
1

Institute for Astronomy (IfA), ETH, Zuriche-mail: reggiani@phys.ethz.ch

Département d’Astrophysique, Géophysique et sampleで3天体
Océanographie, Université de Liège, 17 Allée du Six Août, 4000 Liège, BelgiumØ その他も合わせたfull
UJF-Grenoble1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble UMR 5274, 38041 Grenoble, France
Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France
検出の確率は、2,
19, 25%。
Institute for Astronomy, University of Edinburgh,Blackford Hill, Edinburgh EH9 3HJ, UK
2

Fig. 2. Detection probability for the NaCo-LP observed sample for rcuto f f =100, 30, 20 AU (from left to right).
Fig. 2. Detection probability for the NaCo-LP observed sample for rcuto f f =100, 30, 20 AU (from left to right).

3

4

5

6

INAF – Osservatorio Astronomico di Padova, Vicolo dell Osservatorio 5, 35122 Padova, Italy
Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 USALESIA, Observatoire de Paris Meudon, 5 Pl. J. Janssen, 92195 Meudon, France Italy
9
Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
10
Departmentof Physics and Astronomy, College of Charleston, Charleston, SC 29424 , USA
pl
cutoﬀ
11
INAF Osservatorio Astronomico di Capodimonte via Moiarello 16, 80131 Napoli, Italy
12European Southern Observatory, Casilla 19001, Santiago 19, Chile
13
European Southern Observatory, Karl Schwarzschild St, 2, 85748 Garching, Germany
14
M. ReggianiAstrophysicalet al.: The frequencyof brown dwarfs via
and giantplanets
as companions
to solar-typeItaly
stars
INAF – Catania
Observatory,
S. So
a 78,
95123 Catania,
Fig. 3. Detection probability for the full sample for rcuto f f =100, 30, 20 AU (from left to right).
Fig. 3. Detection probability for the full sample for rcuto f f =100, 30, 20 AU (from left to right).
15
Physikalisches Institut, University of Bern, Sidlerstrasse 5,plCH-3012 Bern, Switzerland
16
NASA Ames Research Center, Moﬀett Field, CA, USA
17
Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland
18
Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
19
Millennium Nucleus “Protoplanetary Disk”, Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile78Ø β とrを変えて、検出が3個以下になる確率が0.3%以下の範囲を調べた。
(Cumming et al. 2008ではβ =0.39)—
ABSTRACT

Context. In recent years there have been many attempts to characterize the occurrence and distribution of stellar, brown dwarf (BD)and planetary-mass companions to solar-type stars, with the aim of constraining formation mechanisms. From radial velocity observations a dearth of companions with masses between 10-40 MJupiter has been noticed at close separations, suggesting the possibilityof a distinct formation mechanism for objects above and below this range.
Aims. We present a model for the substellar companion mass function (CMF). It consists of the superposition of the planet and BD
companion mass distributions, assuming that we can extrapolate the radial velocity measured companion mass function for planets tolarger separations and the stellar companion mass-ratio distribution over all separations into the BD mass regime. By using both theresults of the VLT/NaCo large program (NaCo-LP, P.I. J. L. Beuzit) and the complementary archive datasets that probe the occurrenceof planets and BDs on wide orbits around solar-type stars, we place some constraints on the planet and BD distributions.
Methods. We developed a Monte Carlo simulation tool to predict the outcome of a given survey, depending on the shape of theorbital parameter distributions (mass, semi-major axis, eccentricity and inclination). Comparing the predictions with the results of theobservations, we calculate how likely diﬀerent models are and which can be ruled out.
Results. Current observations are consistent with the proposed model for the CMF, as long as a suﬃciently small outer truncation
radius (!100 AU) is introduced for the planet separation distribution. Some regions of parameter space can be excluded by theobservations.
Conclusions. We conclude that the results of the direct imaging surveys searching for substellar companions around Sun-like stars
are consistent with a combined substellar mass spectrum of planets and BDs. This mass distribution has a minimum between 10 andThe Young Stellar Population of the Cygnus-X DR15 Region–6–

arXiv:1510.02835v1 [astro-ph.SR] 9 Oct 2015

S. Rivera-Gálvez1 , C. G. Román-Zúñiga2,5 , E. Jiménez-Bailón2 , J. E. Ybarra2 , J. F.
Alves3,5 and Elizabeth A. Lada4

Ø Cygnus-Xは数個のOB associa)ons, 数十の星団、数百のHII領域、ABSTRACT40以上の大質量星を含む。その中の南にあるDR15 (d~1.4 kpc)は、
We present a multi-wavelength study of the young stellar population in the
B star, HII領域、PDRを含む。IRDCの先端は可視で見える段階、そCygnus-X DR15 region. We studied young stars forming or recently formed atの隣により若いスポット。
and around the tip of a prominent molecular pillar and an infrared dark cloud.
Using a combination of ground based near-infrared, space based infrared and
X-ray Altodata, weconstructeda point source Spitzer
catalog fromwhich we identified 226
Ø 観測：スペイン Calar
3.5m
JHK seeing~1”,
IRAC&MIPS,
young stellar sources, which we13classified into evolutionary classes. We studied
Chandra ACIS-I X線0.2-7.0
kev, FCRAO CO (1-0)
their spatial distribution across the molecular gas structures and identified several
groups possibly belonging to distinct young star clusters. We obtained samples ofthese groups and constructed K-band luminosity functions that we compared withthose of artificial clusters, allowing us to make first order estimates of the meanages
and age spreads of the groups.
We used a 13
CO(1-0) map to investigate theØ YSOの同定。24µmで受かればClass
I/0。Class
IIはgas kinematics at the prominent gaseous envelope of the central cluster in DR15,
Ybarra et al (2013)に従う。X線源が赤外線源と一致す
and we infer that the removal of this envelope is relatively slow compared to other
るものでJ-H>0,cluster>1.97(K-[4.5]),[3.6]regions, in which[4.5]-[5.8]>0.5,
gas dispersal timescale
could be similar or shorter thanthe circumstellar
disk dissipation timescale. The presence of other groups with
[4.5]>0.7はClass
III。
slightly older ages, associated with much less prominent gaseous structures may
à26 Class 0/I, 155
Class II, 45 Class IIIで、Kryukova et al.
imply that the evolution of young clusters in this part of the complex proceeds(2014)と大体合う。
in periods that last 3 to 5 Myr, perhaps after a slow dissipation of their dense
molecular cloud birthplaces.

Fig. 2.— False RGB (Spitzer MIPS 24 µm, IRAC [8.0], IRAC [4.5]) image of the DR15
region. Images are log-scaled. The DR15 pillar is located at the center. Bright PAH
emission and reflections saturated the pixels at the center of the DR15 cluster shell in the
IRAC [8.0] and MIPS 24 µm channels, thus the cyan-colored region. Other fainter, molecularpillar structures are visible at both flanks of the main pillar. The dark infrared cloud at thenorth shows recent star formation activity and extends westward towards the LBV source– 14 –
G79.29+0.46, located at the center of a bright red shell.

24:00.043

22:00.040

40:20:00.0

36

33

18:00.029

16:00.026

12:00.0

14:00.022Ø 柱密度(Av)が大きいところにClass Iが多い。
Facultad de Ciencias, Universidad Autónoma deØ あるAv以上にいるClass
Iの柱密度は、Avとpower law
Baja California, Ensenada, México(~2.9)にある(Schmidt
type rela)on)。
Instituto de Astronomı́a,
Unidad Académica en Ensenada,
1

2

Universidad Nacional Autónoma de México, Ensenada 22860, México
3

Astronomy Department, University of Vienna, Austria

19

15

1.0 pc12

10.0

20:33:00.0

50.0

40.0

30.0

20.0

10.0

32:00.0
8.4

The Young Stellar Population of the Cygnus-X DR15 Regionの続き

S. Rivera-Gálvez1 , C. G. Román-Zúñiga2,5 , E. Jiménez-Bailón2 , J. E. Ybarra2 , J. F.
Alves3,5 and Elizabeth A. Lada4

Ø Gather algorithm (n番目への距離と等価な円から密度を決める)より、Class IIのクラスターを同定。
ABSTRACT
Ø クラスターごとにK-band luminosity Func)onをモ
デルと比べる。
We present a multi-wavelength study of the young stellar population in the
Cygnus-X DR15 region. We studied young stars forming or recently formed
at From left to right: Color scaled surface density maps, in units of sources per
Fig. 7.—
Ø モデルは、IMFは固定で年齢と年齢の分散を振る。
sq. arcmin, for Class I, II and III candidate YSOs in DR15, constructed with the Gather
and around the tip of a prominent molecular pillar and an infrared dark algorithm.
cloud. Extinction contours are similar to Figures 3 and 5. Yellow circles indicate theàembeddedなC,
Wの方がそうでないSE,
SWより
location
Using a combination of ground based near-infrared, space based infraredandand selected sample extension for clusters and groups identified in the Class II map.
若い。Cは3Myrなのにエンベロープが多い。
X-ray data, we constructeda point source catalog from which we identified 226– 29 –

young stellar sources, which we classified into evolutionary classes. We studied
their spatial distribution across the molecular gas structures and identified several
groups possibly belonging to distinct young star clusters. We obtained samples ofthese groups and constructed K-band luminosity functions that we compared withthose of artificial clusters, allowing us to make first order estimates of the mean
ages and age spreads of the groups. We used a 13 CO(1-0) map to investigate thegas kinematics at the prominent gaseous envelope of the central cluster in DR15,
and we infer that the removal of this envelope is relatively slow compared to othercluster regions, in which gas dispersal timescale could be similar or shorter thanthe circumstellar disk dissipation timescale. The presence of other groups withslightly older ages, associated with much less prominent gaseous structures may
imply that the evolution of young clusters in this part of the complex proceeds
in periods that last 3 to 5 Myr, perhaps after a slow dissipation of their dense
molecular cloud birthplaces.
1

Facultad de Ciencias, Universidad Autónoma deBaja California, Ensenada, México
2

Instituto de Astronomı́a, Unidad Académica en Ensenada,
Universidad Nacional Autónoma de México, Ensenada 22860, México
3

Astronomy Department, University of Vienna, Austria

Table 1. Main Parameters and Age Estimates for Cluster Samples in the DR15 Region

arXiv:1510.05641v1 [astro-ph.GA] 18 Oct 2015

Complex molecules in W51 North region
Jialei Rong1⋆ , Sheng-Li Qin1⋆, Luis A. Zapata2, Yuefang Wu3 ,Tie
Liu4, Chengpeng Zhang3, Yaping Peng1, Li Zhang1 and Ying Liu5
1

Department of Astronomy, Yunnan University, and Key Laboratory of Astroparticle Physics of Yunnan Province,
Kunming, 650091, China
2 Centro de Radiostronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán, México
3 Department of Astronomy, Peking University, Beijing, 100871, China
4 Korea Astronomy and Space Science Institute 776, Daedeokdaero, Yuseong-gu, Daejeon, Republic of Korea 305-348
5 Department of Physics and Hebei Advanced film Laboratory, Hebei Normal University, Shijiazhuang 050024, China

Ø 大質量星は周囲に化学的なインパクトをもたらすß化学種から条件や段階がわかる。
Ø W51 NorthにはH2O, OHメーザー、ダスト連続波、分子流、インフォールが見られ、実際に大質量星を形成している。また、cm波がないので、早期段階。
Ø 観測：SMA, 216.5-218.5 GHz, Δν=0.8
MHz (~1 kms–1), θ~3”, σcont~0.01 Jyb–1, σline~0.1 Jyb–1
ABSTRACT

CH3OH
217.886 GHz

CH2CHCN
227.907 GHz

7CH3COCH 3
227.939 GHz

CH3OCHO
216.966 GHz)Ø 連続波から、粒子半径0.1µm, 密度3 gr cm (=0.2g/cc?), g/
d=100, 温度はCH3OHの回転温度138 KでM ~1348 Mo。

3Intensity (We present Submillimeter Array (SMA) molecular line observations in two 2 GHz-widebands centered at 217.5 and 227.5 GHz, toward the massive star forming region W51
North. We identified 84 molecular line transitions from 17 species and their isotopologues. The molecular gas distribution of these lines mainly peaks in the continuum
IRS2d–3and has a small tail extending to the west, probably associposition of W51 North,ated with W51 d2. In addition to the commonly detected nitrogen and oxygen-bearing
species, we detected a large amount of transitions of the Acetone (CH3 COCH3 ) andKJD3
W51d2
Methyl Formate (CH3 OCHO),
which may suggest that these molecules are present in W51 N
H2
an early evolutionary stage of the massive stars. We also found that W51 North is anethanol-rich source. There is no obvious diﬀerence in the molecular gas distributions
between the oxygen-bearing and nitrogen-bearing molecules. Under the assumptionof Local Thermodynamic Equilibrium (LTE), with the XCLASS tool, the molecular column densities, and rotation temperatures are estimated. We found that theoxygen-bearing molecules have considerable higher column densities and fractional
abundances than the nitrogen-bearing molecules. The rotation temperatures range
from 100 to 200 K, suggesting that the molecular emission could be originated froma warm environment. Finally, based on the gas distributions, fractional abundances
and the rotation temperatures, we conclude that CH3 OH, C2 H5 OH, CH3 COCH3 andCH3 CH2 CN might be synthesized on the grain surface, while gas phase chemistry is
responsible for the production of CH3 OCH3 , CH3 OCHO and CH2 CHCN.

Figure 1. The continuum image at 227 GHz, shown in both contours and grey. The contour levels are 5%, 10%, 20%, 30%, 40%, 50%,
60%, 70%,80%, 90%, 100% of the maximum intensity of ∼3.0 Jy beam−1 . The color scale on the right shows the intensity ranging from0 to 3.5 Jy beam−1 . The synthesized beam is shown in the bottom right corner.

image the corresponding molecular names are labelled,
including oxygen-bearing molecules of CH3 OH, H2 CO,C2 H5 OH, CH3 OCHO, CH3 OCH3 , CH3 COCH3 , nitrogenbearing molecules of CN, CH3 CH2 CN, HC3 N, CH2 CHCN,
sulfur-bearing molecules of SO2 , H2 S, SiS, and deuterated
molecules of DCN and CH3 CCD. The quantum numbers,
frequency, Sij µ2 and Eu of each transition are summarizedin Table 1. Column (1) lists the species and column (2) lists
quantum number, column (3), (4) and (5) give frequency,
Sij µ2 and Eu . The source size θa ×θb , ∆V and I are given
in column (6), (7) and (8), respectively.

CH3CH2CN
218.389 GHz

Key words: ISM:abundances — ISM:individual (W51 North) — ISM:molecules —radio lines: ISM — stars:formation
3.3

Gas distribution

Figure 3 presents a sample of images from the oxygen, nitrogen-, and sulfur-bearing molecules, which can provide spatial distribution of specific molecules. In general, all molecular images show a compact structure.
The peak emission of the oxygen-bearing molecules of
CH3 OH, CH3 COCH3 and CH3 OCHO, and nitrogen-bearing
molecules of CH2 CHCN, CH3 CH2 CN and DCN are coincident with the continuum peak position. The oxygenand nitrogen-bearing molecules are probably well mixed in

1

INTRODUCTION

There are three promising theoretical models to explain theformation of the massive stars: monolithic collapse, competitive accretion, and mergers of low mass stars (see fora review, Zinnecker & Yorke 2007). However, their relativelarge distances (a few parsecs), the clustered formation environments, and their short timescales have made extremely
diﬃcult to discard any of these models (Zapata et al. 2015).
Massive stars have a substantial impact on their sur-space, which imply that they may have same chemical origin (Remijan et al. 2004). While the emission peak of thesulfur-bearing molecules of H2 S, and SO2 are located east of
the continuum peak. Probably the sulfur-bearing molecules
have diﬀerent chemical routes and form in diﬀerent environments when compared with the oxygen- and nitrogenbearing molecules. In addition to the compact source structure, there is an obvious gas extension to the west of thecontinuum traced by the DCN, H2 S, and SiS is observed.

building block to understand massive star formation, sincethese molecules can provide information on the physical conditions and evolutionary phases of massive star formation(Herbst & van Dishoeck 2009).
The W51 North is one of well-studied massive starforming regions within the luminous cluster W51-IRS2 (Zapata, Tang & Leurini 2010). The distance from W51 Northto the Sun is approximately 7 kpc (Imai et al. 2002). However, a more recent and accurate estimation from Xu et al.

4

DATA ANALYSIS

The rotation temperatures and fractional abundances ofcomplex molecules can reflect immediate environments close
to the stars or star-forming cores, but also can provide keyclues in understanding formation mechanism of the specificmolecules. In order to obtain reasonable parameters, we use
the XCLASS to estimate the column densities and rotation
temperatures of the molecules.

Complex molecules in W51 North regionの続き

arXiv:1510.05641v1 [astro-ph.GA] 18 Oct 2015

Jialei Rong1⋆ , Sheng-Li Qin1⋆, Luis A. Zapata2, Yuefang Wu3 ,–7。gas-phaseでは~10–11なので、より多く
4
3
1
1
5
Ø メタノールCH
OH・・・abundaceが最も多く、3.6x10
Tie
Liu
,
Chengpeng
Zhang,
Yaping
Peng
,
Li
Zhang
and
Ying
Liu
3
1
Department of Astronomy, Yunnan University, and Key Laboratory of Astroparticle Physics of Yunnan Province,
生産できるgrainsurfaceの方が合う。
Kunming, 650091, China

2 Centro de Radiostronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán, México

3 Department of Astronomy, Peking University, Beijing, 100871, China
4 Korea Astronomy and Space Science Institute 776, Daedeokdaero, Yuseong-gu, Daejeon, Republic of Korea 305-348–8 Hebei Normal University, Shijiazhuang–11
Department of Physics
and Hebei Advanced film Laboratory,
050024,China
Ø アセトンCH。Orion-KLではhotcoreに集中して3COCH3・・・X~2.0x10 。gas phaseでは~10
いるが、W51 Nでは未発達なのでgrain surface。すぐに壊れるので早期を示唆。
5

ABSTRACT–7)とメタノールに対する比が他の領域より大きØ エタノールCH3CH2OH・・・存在量(X~1.2x10
We present Submillimeter Array (SMA) molecularline observations in two 2 GHz-widebands centered at 217.5 and 227.5 GHz, toward the massive star forming region W51
North. We identified
84 molecular line transitions from 17 species and their isotopoい。上2つと同じ理由でgrainsurface。
logues. The molecular gas distribution of these lines mainly peaks in the continuum
position of W51 North, and has a small tail extending to the west, probably associated with W51 d2. In addition to the commonly detected nitrogen and oxygen-bearing
species,a large amount of transitionsof the Acetone (CH3 COCH3 ) and3 we detected3
3Methyl Formate (CH3 OCHO), which may suggest that these molecules are present inan early evolutionary stage of the massive stars. We also found that W51 North is anethanol-rich source. There is no obvious diﬀerence in the molecular gas distributions–8
between the oxygen-bearing and nitrogen-bearing molecules. Under the assumptionof Local Thermodynamic Equilibrium (LTE), with the XCLASS tool, the molecular column densities, and rotation temperatures are estimated. We found that theoxygen-bearing molecules have considerable higher column densities and fractionalThe
2abundances than the nitrogen-bearing molecules.
3
2 rotation temperatures range
from 100 to 200 K, suggesting that the molecular emission could be originated froma warm environment. Finally, based on the gas distributions, fractional abundances3
and the rotation temperatures, we conclude that CH3 OH, C2 H5 OH, CH3 COCH3 andCH3 CH2 CN might be synthesized on the grain surface, while gas phase chemistry is
responsible for the production of CH3 OCH3 , CH3 OCHO and CH2 CHCN.

Ø ジメチルエーテルCH OCH とギ酸メチルCH OCHO・・・ジメチルエーテルはエタノールの異性体だが、存在量が相関せず、親が違う。ギ酸メチルとは温度、柱密度、分布が似ている。gas phaseでX~4.8x10 を作れる。
Ø シアン化ビニルCH CHCNとシアン化エチルCH CH CN・・・2つの存在量比は他の領域と同じくらい。CH3CH2CN/HC Nに対する比~10はgrain surfaceに合う。
Ø 重水素系・・・DCNは早期を示唆。CH
3CCDは大質量星形成領域では報告が少なく、dark
Key words: ISM:abundances— ISM:individual (W51 North) — ISM:molecules —–8
radiolines:
ISM—
stars:formation
cloudと比較するために重要。X~1x10 はgrain surfaceを支持。
building block to understandmassive star formation,since
1 INTRODUCTIONØ S系・・・H
surfaceでできて、SOàSO
2S/SO2比~0.05は他の領域と同じくらい。H
2Sがgrain2。
these molecules can provide
information on the physical conThere are three promising theoretical models to explain theformation of the massive stars: monolithic collapse, competitive accretion, and mergers of low mass stars (see forditions and evolutionary phases of massive star formation(Herbst & van Dishoeck 2009).

RADIALLY MAGNETIZED PROTOPLANETARY DISK: VERTICAL PROFILEM ATTHEW RUSSO

Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7, Canada.
2

C HRISTOPHER T HOMPSON

Russo &

Canadian Institute for Theoretical Astrophysics, 60 St. George St., Toronto, ON M5S 3H8, Canada.
Astrophysical Journal 2015, in press
Radially Magnetized Protoplanetary Disk: Vertical ProfileB

3and on the stratification of the disk. In the largest simuThe change of sign of Br across the disk plane is mirrored
lations performed to date, an imposed vertical field carryby the toroidal magnetic field that is wound up inside the disk.
ing a non-vanishing flux generates a torque that is about 10
Here a small imbalance in the amplitude of the applied radial
times stronger than a toroidal field of equal strength (Baifield between the two hemispheres has a marked effect on theinternal structure of the disk. The region near the midplane is& Stone 2011), as compared with ⇠ 102 times stronger invery weakly ionized, leading to rapid reconnection of toroidal
the older unstratified simulations of (Hawley et al. 1995).
-1/2
fields of opposing signs. The current sheet sits at the midplane2
The scaling hB i / 0 is obtained in the ideal MHD limit
in the case of perfect reflection symmetry, but otherwise iswhen the plasma parameter of the seed magnetic field isdisplaced to one side.
2
1.
0 = 8⇡P/B0
Now consider now a geometrically thin disk in which a visTo estimate the torque that results when a radial magnetic
cosity given by the second half of Equation (4) is excited. We
field Br0 is imposed at the top of the disk, we write3
move
to cylindrical(Rstar' r, interactingz ' ✓r). ThewithmagnetiF IG . 1.— Poloidal magnetic
fieldcoordinatesof a T-Tauri
the up!
cally active gasthincolumnassumedto be regulated
a characper layers of a geometrically
andisweakly
conducting
PPD.to The
kinetic
B2 0
c2g
teristic
value⌃
byexternal
ionization,
with
a
slow
inward⌫MRI = ↵eMRI.
pressure(2)of the wind exceeds theactpressureofanyverticalfieldremaining
from
-k⌃
8⇡P
⌦
growth
⌃
(R)
/
R
due
to
the
increasing
ionization
rate
act
the first stages of infall from a natal molecular cloud.
and angle of attack of X-rays on the disk near the protostar. In
Here B 0 is the toroidal field that is generated by linear windthe inner disk, where the flaring of the dust absorption layer
2 /R)/d ln R . R /2R, the temperature ofing of the imposed radial field over the vertical diffusion
smaller thanspeedtime
cg and isviscosity
↵cd(h
p
?
g /⌦),
through the disk. The numerical simulations of weakly maga
passively
irradiateddisk scales as T ⇠ R-3/4 . Combining
netized disks ( 01) just described suggest-4 = 1/2.
-2 In the-22Equation
cgVw (4) and (5) with these radial profiles of ⌃act and T ,⇢wstrongVwcalculations performed laterr in this paper, we encounterthe local rate of mass transfer scales as
magnetization (. 1) and use the alternative scaling = 1⇠ ✏w ↵1510.04258v1 [astro-ph.EP] 14 Oct 2015

ABSTRACTThis paper studies the response of a thin accretion disk to
an externalradial magnetic field. Our focus isØ hot Jupiterを説明する原始惑星系円盤内のgas
ﬂow
modelを決定した
on protoplanetary disks (PPDs), which are exposed during their later evolution to an intense,
Star magnetized windい。
from the central star. A radial magnetic field is mixed into a thin surface layer, is wound up by the disk
Disk
shear, and is pushed downward by a combination of turbulent mixing and ambipolar and Ohmic drift. TheØ <1 AUで重要なMRIに基づいたモデルを提案する。
Radially
Protoplanetary Disk:
toroidal field reaches much greater strengths than the seed vertical field that is usually
invokedMagnetizedin PPD models,even becoming superthermal. Linear stability analysis indicates that the disk experiences the magnetorotationalandon the magnetizedstratification
the bothdisk.the In
the oflargest
simuThe cha
instability (MRI) at a higher magnetization thana verticallydiskofwhen
effects
ambipolar
Ø PPDがT-Tauri
windと星からのX線と相互作用する状況で、放射状
lations
performed
to
date,
an
imposedverticalfield
carrybythe toroand Hall drift are taken into account. Steady vertical profiles of density and magnetic field are obtained at
ingtoaa non-vanishing
fluxBgenerates
a torquethat G.
is Careful
about 10Here a sm
several radii between 0.06 and 1 AU in responsewind magnetic field⇠ (10 –10)(r/AU)(radial)の磁場を入れたときのケプラー回転、軸対称円盤の鉛直分布
2P(⌦r)
attention is given to the radial and vertical ionization
structure(Equation
resultingfromirradiationbystellar
X-rays.
The
disk
TABLE 1times stronger
thanatoroidal
field
of
equal
strength
(Bai
field
betw
49).
Ṁ
⇠✓
3⇡⌫
⌃ ◆⇠ R✓◆ ⇣ . (6)1/2
Consider the simplest configuration with B uniform with2⌘
D EFAULT M ODEL PARAMETERS
T
V
r
disk
is
more
stronglymagnetizedcloser
to
the
star,
where
it
can
supportahigherrate
ofmass
transfer.
Asaw
height between
the topof the disk anda reconnection
layer timesを計算する。windとdiskのshearの乱流とMRI乱流。Hall
dri~は無視。
& Stone 2011),
ascomparedwith⇠
10strongerinFirstw,-1
let↵usconsider how thisresult dependsinternalon the rela-. st⇠
0.003✏-1near the midplane. Such a configuration emerges in the verti200 K
400tion (2)betweenaroundstressandkm
the slinearlyAU
ampliresult, the inner ⇠ 1 AU of a PPD is found to theevolvetowardlower
density.
Masstransfer
rates
cal
profiles tosurface
be presented
in
Section 6. Taking
older
unstratified
simulationsof (Hawley
etal.MRI-generated
1995).
fied toroidal
magnetic
field. We take k = 1/4very
from the weakdeDisk Parameters-8-1
tailedmodel
developed
later
in
the
paper.
Equation(6)
gives(1)B = -(3/2)⌦t B ,(3) The evolution of
10 M yr are obtained under conservative assumptions about
the -1/2
MRI-generated
stress.
2⌃g,tot
200 g cm-2
Ṁ/R
in a weakly magnetized disk withfields= 1/2; andof o
The scalinghB/ intimeis⌫ obtained
in
the
ideal
MHD
limit the disk must have aAnypoloidalmagnetic
field
threadingwith idiffusiont ⇠h across the thermal
scale
0the
Ṁ
/R
in
a strongly magnetized disk, for which we
the disk, and the implications for planet migration,
are investigatedaccompanying
paper.
Tbl
5000 K2
in Thenthethecasheight h = c /⌦, one finds
pressure
larger
than
⇢
V
,
or
it
will beswept back.
adopt
= 1.
w
w
when
the plasma
parameterofthemagnetic
seedmagnetic
field
is
µg,bl
1.27 mu✓◆✓◆geometrydiffersfromthat
postulated
byBlandford
Subject
disks —
magnetic
fields—planetsandsatellites:
formation—
proto6 headings: accretion, accretion
Russo & Thompson
B
3
B
displaced
2µg,c2.32 mu=; & Payne (1982) and Pudritz & Norman (1986), and any mag1.
8⇡P
2e
↵
8⇡P
planetary disks — turbulence0 = 8⇡P/B0
acool
5
netocentrifugal
wind
from
the
disk
surface
(Bai
&
Stone
2013;co
Now
✓
◆
0

MRI

r0

MRI

act

(6-8k⌃ -(5+8k⌃ ) )/8(1+2 )⌃0diff r0

2

MRI

-1
2
MRI g

diff

g

MRI

g

2/(1+2 )

0

2
r0

1/32

-1/8

1/(1+2 )MRI⇥⇤
cwhen a radial magneticB
To estimate the⌫ torque= (3/2) ↵e that resultsLesur. et(4)al. 2013) will be quenched. Instead, the T-Tauri wind
8⇡P
⌦
giv
3 surface of the disk, andcosity
interacts
directly
with theits magnetic
field B is imposedat the top of the disk,
wewriteThis demonstrates that a radial seed field can leadto a issubfield
entrained by a thin boundary layer (Figuremove
1).
tocviscousstress compared with an equivathestantiallysignenhancedof thischange.
This paper is devoted to understanding how the magnetic!
lent toroidal seed when B . 8⇡P.
activfield thatin this ofboundarylayercallywill diffuse
The MRI-driven torqueongivenoutpatch
the disk
2 is asheared
B2 acting
2.2. Mass Transfer Induced by a Split-monopolar
Windcg into the disk, and the equilibrium structure that re0 downward
teristicva
Magnetic
Field
depends⌫MRI
on themagnetic
flux
threadingit(Hawley
et
al.
1995;
=↵
eMRI
. care must be taken(2)sults. Particularwith regard to the radial
The magnetized wind that is emitted by
a T-Tauri star may
8⇡P⌦of the ionizationin the disk,
well as the ⌃Sano
et al.
Pessahet bedependenceal.launched2007).This
flux israteusually
as-asgrowth
be sourced
by the2004;
star’s internal
dynamo; or mayfrom the inner regions of the disk itself (Pudritz depletion& Norman of dust in the active layer by the settling of partisumed
tobeoriented
verticallywithrespecttothedisk
plane.
1986). Throughout most of this paper, we approximate
the an outer gas reservoir that feeds the accretion
and angle
cles fromflow
and dust within the disk.The motivation for tackling this first
Wind Parameters
windtoroidal
flow near the disk
plane (✓
= ⇡/2 isin spherical
coorHereB 0 isOur
the
field
that
by linearwind-be dis- the inner-9 M yr-1
poor
understanding
ofgenerated
howverticalflux would
throughṀw
10stepdinates) as steady and spherical, with an embedded
split-the inner ⇠ AU.
has
been
strengthenedwiththediscoveryof
many
planNot surprisingly,
strong magnetizationin our disk
monopole
magnetic
をone
zone
Vw
400 km s-1
tributed
acrossthe disk
surfacehas presented
somethingof sustaineding 初期にBof the imposedradial
field
over
the
verticaldiffusion
time emerges
r0とB
φ0field,
✓ ◆
ets
of
a
substantial
mass
in
close
orbitsaroundnearbysun-like
solutions within the active layer (where it is isassmallerw-2
R
BR✏B (R/0.11AU) Garoadblocktowardbuilding
globaldisk
modB = numericalB(R)
sgn(⇡/2- ✓). thedeterministic(5) of aof
resultbalancebetweenverticaldiffusionandlinearthrough
the
disk.
The
simulations
weaklymagr
stars . In most models of such protoplanetary disks (PPDs)ideal–
MHD
diskに加えたとき✏B
0.01-1winding),of
as geometricallywell as at the top in
the wind-disk
passivelels.(Because
Globalnumerical
simulations
thin
disksofatheboundary
the kinetic
pressuredescribedof the windis much suggest
less than
netized
disks
1)
just
= 1/2.
Inmagnetizationthevariantsofthe‘minimal-mass
Solarnebula’(Hayashi
1981)
0
layer
(where it reflects
the strong
T-Tauri
Turbulence Parameters
the internal hydrostatic pressure of the disk, theprincipal
Equation(h/r. of0.03)
that
resolve
non-ideal
effects
cannotpresentlywind).
In contrast
withthe strong
stronglymagnetized Shakuraquantity
interest islater
the magnetic
flux thatpaper,
threads
it. WeのΣgが減るδの範囲。
calculations
performed
in
this
we
encounterEm↵
eMRI,0 0.1– the surface mass density of the disk increases inward.
consider radial fields up to ⇠ 1 G at 0.1 AU fromSunyaev
the proto- type disk solutions derived by Pariev et al. (2003)
the local r
determine
evolutionofmagnetic
flux. = 1
↵mix,0
1 bedded planets are predicted to drift rapidly toward thestar,
to a surface⇠alternative
10 G atstarmagnetization( corresponding.the1)and dipole
usemagnetic
theverticalscaling

Stellar Parametersr0M⇤M
1. INTRODUCTION
R⇤
2R
RX
10R
Understanding the formation and migration of planets inL⇤L
circumstellar
disks presents several challenges, the first ofLX
2⇥1030 erg s-1
kB TX
1 keV
which is to develop a deterministic model of the flow of gas

Amcrit⇤O,crit

2

MRI

MRI

1/(1+2 )2
r0/(1+2 )

2
g

2
0

w
r

?

?

2

2

F IG . 2.— Radial scaling of the mass transfer rate driven by MRI turbulence,
given an imposed radial magnetic field with a profile -2 > d ln(BR )/d ln R >-2.5. A profile slightly steeper than monopolar near the midplane could result from collimation toward the rotation axis. Black curves label different
dependences of Tr driven by the MRI on seed toroidal magnetic pressure,⌫MRI / (B2 0 /8⇡P) . The vertical disk models constructed in this paper use= 1. The surface density of the inner disk decreases with time between thetwo horizontal red lines. Results plotted here depend mildly on the radial
profile of the X-ray irradiated active column, ⌃act / R-1/4 .

and discussed by Begelman & Pringle (2007), a significant

0(Valenti & Johns-Krull 2004; Daou et al. 2006).
R ⇠ 2R we
Hereare guided by a basic
propertyof protostars:
they by a laminarpart of themagnetic pressure
support is provided(Equation 49).
Throughout the paper we use ↵e to denote the viscosity coefficient
withmagnetic field. Johansen & Levin (2008) have detoroidal
arestronglymagnetizedandaresourcesofintensewinds
durṀMthe dependence on background magnetic pressure factored out.
timescale that is shorter than the observed disk lifetimes. Al-

10(Goldreich & Tremaine 1980; Lin & Papaloizou 1986), on a
100

?

3

velopeda shearing
box model thatis initialized with a strong
Consider the simplest configuration
with
Br0 uniform
withRADIALLY MAGNETIZED PROTOPLANETARY DISK: VERTICAL PROFILEM ATTHEW RUSSO

Radially Magnetized Protoplanetary Disk: Vertical Profile

の続き

15

Department of Physics, University of Toronto, 60 St. George St., Toronto, ON M5S 1A7, Canada.

C HRISTOPHER T HOMPSON

Canadian Institute for Theoretical Astrophysics, 60 St. George St., Toronto, ON M5S 3H8, Canada.
Astrophysical Journal 2015, in press

ABSTRACTThis paper studies the response of a thin accretion disk to an external radial magnetic field. Our focus ison protoplanetary disks (PPDs), which are exposed during their later evolution to an intense, magnetized windfrom the central star. A radial magnetic field is mixed into a thin surface layer, is wound up by the disk
shear, and is pushed downward by a combination of turbulent mixing and ambipolar and Ohmic drift. The
toroidal field reaches much greater strengths than the seed vertical field that is usually invoked in PPD models,even becoming superthermal. Linear stability analysis indicates that the disk experiences the magnetorotational
instability (MRI) at a higher magnetization than a vertically magnetized disk when both the effects of ambipolarand Hall drift are taken into account. Steady vertical profiles of density and magnetic field are obtained atseveral radii between 0.06 and 1 AU in response to a wind magnetic field Br ⇠ (10-4 –10-2 )(r/AU)-2 G. Carefulattention is given to the radial and vertical ionization structure resulting from irradiation by stellar X-rays. The
disk is more strongly magnetized closer to the star, where it can support a higher rate of mass transfer. As aresult, the inner ⇠ 1 AU of a PPD is found to evolve toward lower surface density. Mass transfer rates around10-8 M yr-1 are obtained under conservative assumptions about the MRI-generated stress. The evolution of
the disk, and the implications for planet migration, are investigated in the accompanying paper.
Subject headings: accretion, accretion disks — magnetic fields — planets and satellites: formation — protoplanetary disks — turbulence
1. INTRODUCTION

standing the formation and migration of planets inellar disks presents several challenges, the first of
to develop a deterministic model of the flow of gas
within the disk.The motivation for tackling this firstbeen strengthened with the discovery of many planubstantial mass in close orbits around nearby sun-likemost models of such protoplanetary disks (PPDs) –of the ‘minimal-mass Solar nebula’ (Hayashi 1981)

the sign of this change.
The MRI-driven torque acting on a given patch of the disk
depends on the magnetic flux threading it (Hawley et al. 1995;
Sano et al. 2004; Pessah et al. 2007).This flux is usually assumed to be oriented vertically with respect to the disk plane.
Our poor understanding of how vertical flux would be distributed across the disk surface has presented something ofa roadblock toward building deterministic global disk models. Global numerical simulations of geometrically thin disks

Herschel HIFI observations of the Sgr A +50 km s−1 Cloud ⋆Deep searches for O2 in emission and foreground absorption
Aa. Sandqvist1 , B. Larsson1 , Å. Hjalmarson2 , P. Encrenaz3 , M. Gerin4 , P. F. Goldsmith5 , D. C. Lis3,6 , R. Liseau2 ,L. Pagani3 , E. Roueﬀ7 , and S. Viti8
Stockholm Observatory, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden–7
Ø SWASとOdin衛生によって、Oe-mail: aage@astro.su.se 2分子は予想より100倍少ないとわかった(<1.2x10 @Sgr A)。
Department of Earth and Space Sciences, Chalmers –1
University of Technology, Onsala Space Observatory, SE-429 92 Onsala,Ø Herschel Oxygen
CloudのO2 487と774 GHzを観測(dv~0.5 kms–1)。
SwedenProjectでSgr A +50kms
LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universits, UPMC Univ. Paris 06, F-75014, Paris,
FranceØ 結果、O2輝線はnondetec)on。487 GHzがTmb,3σ<1.06 mK、774 GHzが<2.0 mK。
LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universits, UPMC Univ. Paris 06, cole normale su4 cm–3, ΔV=17.1 kms–1àX(O )<5x10–8, OdinやPDFモデルより小さい。
F-75005,
Paris,
FranceØ RADEXでT=80prieure,
K,
n
=10
H2
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove2 Drive, Pasadena CA 91109, USA

arXiv:1510.06620v1 [astro-ph.GA] 22 Oct 2015

1

bservations of the Sgr A +50 km s−1 Cloud

2
3

4
5

6

California Institute of Technology, Cahill Center for Astronomy and Astrophysics 301-17, Pasadena, CA 91125, USA
LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universits, UPMC Univ. Paris 06, F-92190, Meudon,
France8
Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
7

Received <date>; accepted <date>
ABSTRACT

Context. The Herschel Oxygen Project (HOP) is an Open Time Key Program, awarded 140 hours of observing time to search formolecular oxygen (O2 ) in a number of interstellar sources. To date O2 has definitely been detected in only two sources, namely ρ Oph
A and Orion, reflecting the extremely low abundance of O2 in the interstellar medium.
Aims. One of the sources in the HOP program is the +50 km s−1 Cloud in the Sgr A Complex in the centre of the Milky Way. Its
environment is unique in the Galaxy and this property is investigated to see if it is conducive to the presence of O2 .
Methods. The Herschel Heterodyne Instrument for the Far Infrared (HIFI) is used to search for the 487 and 774 GHz emission linesof O2 .
Results. No O2 emission is detected towards the Sgr A +50 km s−1 Cloud, but a number of strong emission lines of methanol (CH3 OH)
and absorption lines of chloronium (H2 Cl+ ) are observed.
Conclusions. A 3σ upper limit for the fractional abundance ratio of [O2 ]/[H2 ] in the Sgr A +50 km s−1 Cloud is found to be X(O2 )≤ 5 × 10−8 . However, since we can find no other realistic molecular candidate than O2 itself, we very tentatively suggest that two
weak absorption lines at 487.261 and 487.302 GHz may be caused by the 487 GHz line of O2 in two foreground spiral arm clouds.
By considering that the absorption may only be apparent, the estimated upper limit to the O2 abundance of ≤ (10 − 20) × 10−6 inthese foreground clouds is very high, as opposed to the upper limit in the Sgr A +50 km s−1 Cloud itself, but similar to what has beenreached in recent chemical shock models for Orion. This abundance limit was determined also using Odin non-detection limits, andassumes that O2 fills the beam. If the absorption is due to a diﬀerential Herschel OFF-ON emission, the O2 fractional abundance may
be of the order of ≈ (5 − 10) × 10−6 . With the assumption of pure absorption by foreground clouds, the unreasonably high abundanceof (1.4 − 2.8) × 10−4 was obtained. The rotation temperatures for CH3 OH-A and CH3 OH-E lines in the +50 km s−1 Cloud are foundto be ≈ 64 and 79 K, respectively, and the fractional abundance of CH3 OH is approximately 5 × 10−7 .
Key words. Galaxy: centre – ISM: individual objects: Sgr A – ISM: molecules – ISM: clouds

1. Introduction
The core of the Milky Way Galaxy is a region of great complex-

Nuclear Disk (CND). The CND has a mass of 104 to 105 M⊙
and a gas temperature of several hundred degrees. Beyond this,
there exists a large molecular belt, consisting predominantly of