Submillimeter Array Observationsof the RXJ1633.9-2442 Transition
Disk: Evidence for Multiple Planetsin the Making
Cieza, L.A., et al.
2012, ApJ, 752, 75
担当：塚越

星形成ゼミ@三鷹
2012/11/9 1
12年11月8日木曜日

概要• Transition Disk(TD)天体RXJ1633-2442のSMA観測• 分解能 ~0.3”• OphのTDの中で最も重い• キャビティ構造(Rin=~25AU)を空間分解• SEDからの示唆と異なる(~8AU)• キャビティ内に何かしらの構造•~10AUに光学的に厚いnarrowリング•

5-20AUに光学的に薄いダストが広がる• multiple planetsによるキャビティ構造生成を議論• core accretionモデルのgas accretion phase2
12年11月8日木曜日

内容• イントロダクション• 観測とそれぞれの結果について• 円盤モデルの説明とフィッティング• 議論

3
12年11月8日木曜日

Introduction

4
12年11月8日木曜日

Transition Disk Object• CTTS -> WTTSの遷移段階• 円盤進化・惑星系形成の理解へのキー• 近赤外超過の減少+長波長側での十分な超過• ギャップ形成メカニズムのモデル• ダスト成長・沈殿• photoevaporation• dynamical interaction••

stellar companion
planet formation

5
12年11月8日木曜日

Transition Disk Object

Brown+2009
12年11月8日木曜日

6

AA49CH03-Williams

ARI

14 July 2011

19:21

7.1. Spectral Energy Distribution Diversity and Interpretati

観測による切り分け分け可能[Najita+2007]

12年11月8日木曜日

Figure 10[Williams&Cieza2011]

Decision tree to determine the dominant physical process for transition disks, defined as having
a spectral energy distribution of classical T Tauri stars
2 b at an
flux decrement relative to the median–9
2.2 µmwavelengths. This appears to be an exhaustive set of possibilities for transition disks in Ophiuchu
1
et al. 2010), but there may be rare additional possibilities in other regions.
log λFλ (ergs s–1 cm–2)–10

αIR < 024 µm

0Interestingly, nonaccreting objects with relatively massive disks (!2.5 MJup ) are ab–1
Ophiuchus transition disk sample. Such
objects
are
rare
but
do
exist.
The
cold
disk aro
α>0excessλturn-off = 8 µm
–11is an example (Brown et al. 2007), and its properties could be explained by a–2compani
Icenough to disrupt accretion onto the star. A few accreting binary systems are known–3
for example, DQ Tau (Carr,–12Mathieu & Najita 2001) and CS Cha (Espaillat et al. 20–4implies that a massive companion does10 0not always
stop accretion. The10 2eccentricity
o
10 0
10 1
and the viscosity and scale height of the disk alsoλ(µm)
determine whether accretion 7onto t
continue (Artymowicz & Lubow 1996).
8
Binarity is also knownFigure
to resultin transition disk SEDs. Identifying close compan
αexcess

7-117. Downloaded from www.annualreviews.org
IBRARY on 10/27/11. For personal use only.

• SED形状• 円盤質量• 質量降着率• multiplicity

Annu. Rev. Astro. Astrophys. 2011.49:67-117. Downloaded from www.annualreviews.org
by KOKURITSU-TENMONDAI LIBRARY on 10/27/11. For personal use only.

• 以下のような情報で切りTransition disks present a variety of IR SED morphologies, and theircaptured by the traditional classification scheme of young stellar objects
III system; see Section 2). In order to better describe the shape of tran
et al. (2007) introduced a two-parameter scheme based on the longest
observed flux is dominated by the stellar photosphere, λturn-off , and th
λturn-off to 24 µm (Figure 8a.)αexcess , computed from Accreting?
Because of their diversity, the precise definition of what constitutes
Yes literature is far No
in the disk-evolution
from homogeneous. Transition di
objects with no detectable near-IR excess, steep slopes in the mid-IR,(Muzerolle et al. 2010; Sicilia-Aguilar, Henning & Hartmann 2010). T–3αexcess > 0?one and effectively correspondsLdisk/L star > 10
restrictive
to objects
with?λturn-off ! 4.5
The above definition has been relaxed by some researchers (Brown et al
Yes
Yes
No excesses. T
to includeNo
objects with small, but still detectable,
near-IR
been more broadly defined in terms of a significant decrement relativ
CTTS at any or all IR wavelengths (Najita, Strom & Muzerolle 2007; C
Dynamicalnouns haverecently
emerged in thePhotoliterature to distinguishsubclasses
Grain
growthDebrisclearing
evaporation
et al. 1999). Objects with no detectable near-IR excess and αexcess > 0 h

観測による切り分け• [Cieza+2010: Paper I]• 主にSpitzerの観測がベース• OphのYSOに対してサーベイ• 4/26天体がplanet forming disk candidateに相当•••

sharpなinner edge (SEDより)
重い円盤
降着を示す

• SEDだけでは円盤パラメータが縮退する為、実際にイメージングする事が重要となる
8
12年11月8日木曜日

RXJ1633.9-2442• Oph.にあるTD object candidate• d=120pc• K7 star• ~10-10 Msun/yr• ‘planet forming disk’にカテゴリ• OphのTD candidatesでは最も重い円盤• SEDによるモデリング[Orellana+2012]• Mdisk=17MJ (1.6E-2 Msun)• Rin=7.9AU9
12年11月8日木曜日

Observations & Results
SMA observation [Main]
Spectral energy distribution
Keck aperture masking observation
Magellan optical spectroscopy

10
12年11月8日木曜日

SMA Observations
The Astrophysical Journal, 752:75 (11pp), 2012 June 10

Cieza et al.

• 340 GHz (880mum) 連続波• very extended configuration
While SED modeling can be a powerful tool to estimate thephysical properties of circumstellar disks, it has severe limitations. It is a well known problem that different combinationsof parameters can reproduce the photometry data equally well,even when very well sampled SEDs are available (e.g., see
Cieza et al. 2011 for the T Cha case). Fortunately, resolved(sub)millimeter images can break many of the degeneracies
between model parameters and help constrain disk properties
much better than is possible with the SED alone (Andrews et al.
2009; Brown et al. 2009; Isella et al. 2010).
RX J1633.9-2442 is the most massive of the four “planetforming disk” candidates identified in Paper I. Its SED wasrecently modeled by Orellana et al. (2012) as a 17 MJup disk with
a 7.9 AU radius cavity. Here we present high-resolution (0.!! 3 ∼35 AU) Submillimeter Array (SMA) continuum observations at
340 GHz (880 µm) of RX J1633.9-2442 and use the MCFOST
radiative transfer code (Pinte et al. 2006) to simultaneously
model the entire optical to millimeter wavelength SED and
SMA visibilities in order to constrain the structure of its disk. In
Section 2, we present our SMA data and the photometry fromthe literature that we use to construct to the full SED, as well as
the Keck aperture masking data we have obtained to search for
low-mass companions and the Magellan optical spectroscopy
data we use to better measure the spectral type of the central
star. Our disk model and the degree to which each of the disk
parameters can be constrained are discussed in Section 3. In
Section 4, we analyze our results in the broader context of disk
evolution and planet formation models. A summary of our main
conclusions is presented in Section 5.

• 基線長 120-510m• 分解能~0.3” (=36AU)• Imaging• 東西に目玉構造• 差し渡し~1”(=120AU)• 軸比より、inclination > 45deg (from face-on)
2. OBSERVATIONS
2.1. SMA Observations and Data Reduction

11

SMA Observations• UV-plane• ‘ダイレクトな‘干渉計の出力• deprojection• 円盤のinclinationとP.A.を0とするように変換する=>円盤の構造が見やすくなる• 視野中心にある対称構造円盤
はビジビリティのimaginary
fluxが0になる• real partが0となる部分がinner radiusに対応
12
12年11月8日木曜日

Spectral Energy Distribution
Figure 2. Deprojected visibility profile (visibility flux vs. deprojected baseline length). A null is seen at a baseline length of ∼270–280 kλ (240–250 m), indicating asudden density change at ∼25 AU. The deprojected visibilities of the three models discussed in Section 3.2 are overlaid.
(A color version of this figure is available in the online journal.)√
db = u2 + v 2 cos φ cos i, φ = arctan(v/u)−P.A., and i is theinclination (Lay et al. 1997). A first approximation to the offsets
in R.A. and decl. can be obtained by examining the image itself,
but more accurate numbers can be calculated by assuming radial symmetry and minimizing the imaginary flux components
typical (adiskof the deprojected visibilities
face-on radially symmetric disk
at the center of the field should have zero imaginary flux components at all spatial frequencies). Using this latter approach,
we obtained positional offsets of 0.$$ 17 and −0.$$ 24 in R.A. anddecl., respectively. We estimate the P.A. to be 100◦ ± 5◦ west
of north from the orientation of the continuum image and theinclination to be 50◦ ± 5◦ from the aspect ratio of simulated
images (see Section 3.2.1). The deprojected visibility profile,
shown in Figure 2, has a null characteristic of disks with sharp
inner holes (i.e., a large drop in the surface density over a small
radial distance). The location of this null is set by the spatial
frequency associated with the inner hole and directly constrains
its radius. We binned the data using 40 kλ bins. This bin size
is somewhat arbitrary, but it results in 13 visibility values, anumber similar to that of the SED points. We have verified thatthe shape of the visibility profile and, in particular, the locationof the null are robust to the choice of bin size. In Section 3, wemodel the deprojected visibility profile, together with the SED,
to place constraints on several disk structure parameters.
2.2. Spectral Energy Distribution
We constructed the optical to millimeter wavelength SED
for RX J1633.9-2442 from the following sources. The R-band
flux comes from the USNO-B1 catalog9 (Monet et al. 2003),
and the ground-based near-IR fluxes are from the Two Micron
All Sky Survey (2MASS) survey (Skrutskie et al. 2006). The
12 and 22 µm fluxes come from the Wide-field Infrared Survey
12年11月8日木曜日
Explorer (WISE).10 The Spitzer and 1.3 mm fluxes are from

Table 1
RX J1633.9-2442 Photometry Data
Wavelength
(µm)
0.65
1.2
1.6
2.2
3.6
4.5
5.8
8.0
12
22
24
70
850
1300

Flux
(mJy)

Flux
(mag)

Errora(mJy)

Telescope

Reference

3.53e+00
1.04e+02
1.85e+02
2.02e+02
9.67e+01
7.10e+01
5.12e+01
3.28e+01
2.41e+01
2.54e+02
2.28e+02
7.13e+02
2.10e+02
8.18e+01

14.85
10.46
9.36
8.80
8.66
8.51
8.37
8.23
7.80
3.79
3.74
...
...
...

30%
15%
15%
15%
10%
10%
10%
10%
10%
10%
10%
15%
15%
15%

USNO-B1
2MASS
2MASS
2MASS
Spitzer
Spitzer
Spitzer
Spitzer
WISE
WISE
Spitzer
Spitzer
JCMT
SMA

1
2
2
2
3
3
3
3
4
4
3
3
5
3

Notes. a The optical and near-IR uncertainties are dominated by the extinction
corrections.
References. (1) Monet et al. 2003; (2) Skrutskie et al. 2006; (3) Cieza et al.
2010; (4) Wright et al. 2010; (5) Nutter et al. 2006.

Our target is embedded in the Ophiuchus molecular cloud, andthus is strongly affected by extinction. Taking advantage ofthe lack of near-IR excess, we estimate an extinction AV =5.6 mag from the J − KS color excess, adopting AV = 5.88
× ((J − KS )–(J − KS )o ), where (J − KS )o is the expected colorof a dwarf main-sequence star (Kenyon & Hartmann 1995)
of the same spectral type as RX J1633.9-2442, a K5 star13(see Section 2.4). The extinction at other wavelengths wasestimated from the extinction relations listed in Cieza et al.
(2007). Extinction becomes negligible at 24 µm and beyond, soKeck Aperture Masking Observations• Keck-II 10 m telescope• 近傍companionの存在の調査• K’ filter• AO imager: NIRC2• non-redundant aperture masking (NRM)法• 伴星無し• 2.4-4.8 AU --- >6MJ
• >4.8AU --- >3.5MJ

14
12年11月8日木曜日

Magellan Optical Spectroscopy Observations• 6.5 m Clay telescope• Paper Iで行ったSPtypeとEW(Hα)を再測定• 2.5m Du Pont telescope• SPtype: K7 -> K5• Accretion rate: 10-10 -> 10-10.6 Msun/yr• EW(Ha)=300 -> 230 km/s

The Astrophysical Journal, 752:75 (11pp), 2012 June 10

Cieza et al.

15

Disk Model & Fitting
SED & visibility simultaneous fitting

16
12年11月8日木曜日

Fitting Procedure• モデルSEDと880mumイメージを作成• MCFOST radiative transfer code[Pinte+2006]使用• モデルイメージをフーリエ変換してビジビリティに• CASAを使用• uv samplingを実際のSMAに合わせる• SEDおよびビジビリティのchi-squareを導出• chi-squareを追い込む• IDLルーチンのMPFITを使用• 何度か初期値を変えてbest-fitパラメータを導出、平均値やエラー値を見積もる
17
12年11月8日木曜日

Disk Model• これまでTDを説明してきた円盤構造を採用• 完全な穴あき円盤(CoKu Tau/4)=> empty cavity• 穴内に光学的に薄いダスト(GMAur)=> two-component disk
• 光学的に厚い円盤の一部が光学的に薄いギャップで区切られている(TChaやLkCa15)=> narrow ring within cavity

empty cavity
12年11月8日木曜日

two-component disk

narrow ring within cavity 18

In this prescription, the surface density is proport
discrepancy
disk sizes
continuuminthe innerindisk,
but itobtained
quicklyfrom
becomesdomialine images (Hughesal. 2008;
IsellaΣdust
et al.=2007;
Piét
exponential
taper atet large
radii.
0 with2005),
we follow(2012)radius
and adoptofradiusRcav . Mathews
We set ettheal.outerof thethefoddescription
for the surface
density
profileand isthenotsizev
200
AU. However,
we notethat our
model
disk:
to the exact value of Rout because the exponen$!
! very"−γ low #surface"
the outer disk implies
densitie2−γ
Empty cavity
RRΣdustof(R)=SMA
ΣC observations)exp −for radii #R,C
sensitivity
our• 円盤密度構造
RC is given by aRGaussianC
distribution of the dust
height h = hC RC (R/RC )1+ψ , where hC RC Ciezais theThe Astrophysical Journal,
752:75 (11pp),
2012 June accretion10
eton viscousmodel• based
where
Σ
is
the
surfacedensityatacharacteristic
radiC
at R and ψ is the power
law
describing the fl
Tableof
2 the disk viscosity, νfor each parametercan be used to calculate the mean and an and γC is the radial dependence
ダストサイズ分布•
The dust
content
by a differ
StellarParametersis
and described
Fixed Disk Parameters
associated uncertainty (see Section 4.2 in Mathews et al. 2012 disk.
In this prescription, the surface density is proportional
−p
law
for
the
grain
size
distribution(dn(a)∝
afor a discussion on estimating
theuncertainties).
-pParameter
AdoptedValuedn(a)∝ada•in the inner disk, but it quickly
becomes dominated
12
0.005
µm
and
3900
µm.
We
adopt
porousStellarTeff (K)4350
exponential
taper
at large radii. Σdust= 0thewithin
the
3.2.
Disk
Parameterization
キャビティの大きさ内(Rcav)で•
g
4
Mathis(1989) for the grain compositioof radius&log
RWhiffen
cav . We set the outer radius of the disk, R
Distance (pc)
120
are
those
of
the
best
matchedphotosp
Transition disksΣ=0にする
are complex systems that have been modeled parameters
200 AU. However,
we
note
that
our
model
is
not
Inclination (deg)
50 very s
with a wide range of structures. Some objects such as CoKu (Kurucz
1979,
a p K5 star= 4350t
to the exact
valueof Rforbecausethe (T
exponential
Grainsize 1993)
distribution
slope,
out
eff−3.5
Tau/4 have inner holes that seem to be completely depleted of 4.0)
adisk
(µm)
0.005
min
the outer
implies well
very establishedlow surface distancedensities
(bel
at
the
relativelyof• 放射平衡で円盤温度を決定
IR-emitting grains(D’Alessio et al. 2005), while others such sensitivityaof
(µm)
3900
max
our SMA observations) for radii #R2008). The
as GM Aur have cavities filled with optically thin dust (Calvet Ophiuchus molecular cloud (Loinard et al. C
distributionof andthe dust
is given
by a Gaussian
SEDsvisibility
profilesassumingwith
an i
et al. 2005). Yet other systems, like T Cha and LkCa 15, are best created1+ψ
heightwhere
hCthatRC adopting
isisthescalea◦listedh in=Table
C R3.
C (R/RC )not a, freedescribed as having optically thin gaps separating optically thick 60
Misparameter.
Itobtainedfor the hdisk,
but
found
diskquickly
at Rintegratingψtheis surface
the power
describing
theinner and outer•disk
components (Olofsson et al. 2011; Espaillat ofdensitylaw
profileover withradiusandflaringassum
中間赤外が再現出来ない
50C ◦ andresultedin synthetic
imagesaspectr
et al. 2010). In what follows, we explore all three possibilities disk.
The dustmass
content
is 100.
described by a differential
a gas-to-dust
ratio ofclosertothe
thegrainobserved
image
hence
this
−p
for the structure of theJ1633.9-2442 disk.
For
thisparameterization,
we andran (dn(a)thesearchlaw forsize distribution∝use
aalgorithmda)lab
主にvisibilityからRcavの大きさを制限• RX
12 allallmodels.
Table
lists
the
thatgrainaretimes.
visibility
profileandtheparameters
SED
the overall
b
0.005
µmThe
and
39002µm.
We
adopt
theofporous
できるが、大きいempty
cavityでは
3.2.1. Empty Cavity
fit model
fromall(1989)
fiveruns
in“empty
Figures cavi
2 The
and
model.
The
six freeparameters
for theMathis&Whiffenforaretheindicatedgraincomposition.

Disk Model•

12-24mumの超過を作れない

We begin our modeling by adopting the simplest possible
structure for a transition disk: a disk with an empty cavity.
Motivated by physical models of viscous accretion disks (e.g.,
Hartmann et al. 1998; Lynden-Bell & Pringle 1974) and the
12年11月8日木曜日
discrepancy
in disk sizes obtained from continuum and CO

respectively. The mean and uncertainty for each parameterparameters
are those of the best matched photospheric
listed in Table 3 in the “Empty Cavity” column. While the mo(Kurucz1979,
forprofilea K5verystarwell,(Teffthe=observed4350 K,22l
reproduces
the1993)
visibility
12 Themaximumgrain
size ofisestablishedsomewhatbutcorresp
19 pt4.0)24atµm
thefluxes
relatively
welldistanceof120
arefactors∼2–3(i.e., arbitrary,
∼10σ
–20σ
) highersizeof the longest wavelength
in the SED, etwhich
approximate
Ophiuchus
cloud
al.µm
2008).
We i
predicted molecularby the model.
Since(Loinard
the 22 and 24
measureme
grain sizes the data are sensitive to (Draine 2006).

Disk Model• Two-component disk

• キャビティ内に面密度を低下させたダストを分布させる•••

Σcav=δcav x Σdust : δcavはdepletion factor
Rin < R < Rcavの範囲 (Rin以内はΣ=0)
Rin, δcavが追加パラメータになる• SEDを良く再現出来る
•

Σ
Rcav
Rin

Rin=7AU, δcav~100• Narrow ring within cavity• キャビティ内に細いリング構造を置く••

δcav*Σ

Rring,in~Rring,out

ある程度の密度を持ったリング(optically thick)
Rring,in < R < Rring,out: これらが追加パラメータ• SEDを良く再現出来る•
12年11月8日木曜日

2 AU width ring at 10 AU

20

Synthesis of Modeling Result

Astrophysical Journal, 752:75 (11pp), 2012 June 10

Cieza et al.
Table 3Fitted Disk Parameters and χ 2 Statistics

Parameter

Empty Cavity

Two-component Disk

Ring within Cavity

RC (AU) ≠Rout
Rcav
log(ΣC )(g cm−2 )γhC
ψRin (AU)log(δcav )Rring,in (AU)Rring,width (AU)
Mdisk (MJup )a
χ 2 visibility (range)b
χ 2 SED (range)
χ 2 visibility (adopted)c
χ 2 SED (adopted)
χ 2 total (adopted)

39.7 ± 5.6
22.7 ± 1.6−0.23 ± 0.40
−0.49 ± 0.24
0.014 ± 0.003
0.37 ± 0.04
...
...
...
...
19
14–38
89–10936103
13938.2 ± 5.3
25.6 ± 1.4−0.31 ± 0.31
−0.30 ± 0.41
0.018 ± 0.002
0.30 ± 0.09
6.9 ± 1.6
−2.0 ± 0.4
...
...
13
12–27
24–33
21
24
45

42.7 ± 3.7
27.3 ± 2.1−0.39 ± 0.24
−0.81± 0.16
0.019 ± 0.002
0.22 ± 0.14...
...
10.0 ± 2.3
2.2 ± 0.15
14
26–50
27–33
28
31
59

12年11月8日木曜日 Notes.

21

Synthesis of Modeling Result• 円盤質量は15MJ程度• フラットなgeometryを持つ•

スケールハイト 0.8AU以下 at 40 AU• キャビティ内部構造は不明• two-component disk or ring
within cavity• 円盤構造として3つの領域が存在• inner most region: NIR excess無し, small grainも消失• middle region: ギャップ内のunseen structure, 20mum
あたりを形成• outer most region: SMAでimaging, >25AU
12年11月8日木曜日

22

Discussions
ギャップ形成メカニズムと惑星系形成の可能性について

23
12年11月8日木曜日

Photoevaporation• 各エネルギーに対して異なる振る舞い•

FUV(6eV---13.6eV), EUV(13.6eV---0.1keV),X-ray(>0.1keV)• EUVのみのモデル[Alexander+2006]• 軽い円盤、降着率10-10Msun/yrくらいで有意に• 一度生じると早い円盤散逸を促す(~105yr)• FUV,X-rayを含むモデル[Owen+2011,Corti+2009]• 10-8Msun/yr程度でholeが生成• 重い円盤でのphotoevaporationを説明出来る• ただしキャビティサイズ↗ですぐに降着率↘
24
12年11月8日木曜日

1894

Photoevaporation
J. E. Owen, C. J. Clarke and B. Ercolanossociated accretion. This phase lasts approximately ∼10 per centof the observable disc’s lifetime. Once the inner disc has entirely
drained on to the central star, the inner edge of the outer disc is diectly exposed to X-ray irradiation and the outer disc is then erodedo large radius. During this phase, a centrifugal barrier prevents maerial accreting from the inner-edge on to the star and the disc would
gasがunboundとなる位置はppear as a non-accreting ‘transition’ disc with a large inner hole.
The structural propertiesof observed ‘transition’/‘pre-transition’
Mstarに依存
disc are currently more detailed than the photoevaporation modelan predict. This must
await the development of coupled dust andL
X-ray∝Mstar3/2
gas evolution models that are correct when the dust-to-gas ratios no longer small. Therefore, at this stage we do not distinguishbetween ‘transition’ and ‘pre-transition’ discs. Although discussed
n Section 7.2, the inclusion of ‘thermal sweeping’ significantly
20AU以上のinner
holeは説明出
hanges the accreting
to non-accreting fraction predictedby previous photoevaporation
models, to a population that will be a majority
来ないof accreting transition discs.
The observational data however also contain examples of transiion discs with large inner holes (Rhole ! 20 au) and large accretion
ates (Ṁ ∼ 10−8 M# yr−1 ) that are simply impossible to create
hrough any kind of photoevaporation model. It has been suggested
hat these objects could have their large accretion rates set by FUV
onization and MRI activation at the inner edge of the hole (PerezBecker & Chiang 2011); in this case, the inner hole (or gap) is
reated by the tidal effect of a planet within the hole and dust filration at the inner edge of the outer disc is invoked to reduce the
12年11月8日木曜日
opacityof the inner disc. However, such models are at an early

Owen+2012• Rin,降着率は中心星質量に依存する••• 観測天体はMstar<1Msun

0.3Msun

1Msun•• 複雑な3構造を作るのも難しい

Figure 17. The inner hole radius and accretion rate of low-mass objects
classified
as ‘transition’ discs by varies authors: cyan triangles (Brown et al.
Rinと降着率の測定値と2009); blue filled triangles and squares (Cieza et al. 2010); black open
photoevaporationによる予想
squares (Ercolano et al. 2009a); black filled squares (Espaillat et al. 2008,
影の部分がモデル(Mstar<1.5Msun)で2010); black
open circles (Hughes et al. 2009, 2010); red filled circles(Kim et 形成可能なパラメータスペースを示す
al. 2009); magenta filled diamonds (Merı́n et al. 2010); green filledstar (Najita et al. 2010). Where error bars or ranges are listed, they
25 areshown. Any object classified as non-accreting it is placed on the plot withan accretion rate of 10−11 M# yr−1 . The grey region represents the region

Grain Growth• ダスト成長によるκ変化もinner holeを説明可能• 成長は円盤内側でより進む•

Σが大きく、dynamical timescaleも短い• モデル計算でも似たSEDを生成可能[Dullemond&Dominik2005]• sharpなedge(Rin,Rcav)を説明出来ない• κの動径方向変化はよりsmoothになる•

dust fragmentationとradial drift• κの減少で磁気不安定性が起きやすくなり降着が激しくなる事が期待される => 低い降着率が説明不可
26
12年11月8日木曜日

Dynamical Clearing• sharpなinner edgeを生成可能[Artymowicz&Lubow]• バイナリ円盤の観測でも見られる(e.g.,CoKu Tau4)• いくつかのTDは単一星である事が示されている• 本観測天体:brown dwarf質量まで無し(at 2.4AU)=>少なくとも2つのlow mass objectが必要• inner most region (<8AU)とdepleted region(<25AU)• multiple planetで大きいギャップを生成可能[Dodson-Robinson&Salyk2011,Zhu+2011]•

惑星への降着が起きる為、低い(星への)降着率も説明出来る

27
12年11月8日木曜日

Dynamical Clearing• inner disk構造で近赤外超過を作らないには、5AU以内で104の(Σ)depletionが必要• 降着率は10-12 Msun/yrくらいが期待される (Macc∝Σ)=>観測と合わない• inner diskで(multiple)optically thick tidal stream(数%のfilling factor)を考える

The Astrophysical Journal, 738:131 (15pp), 2011 September 10

Dodson-Robins• 観測を説明出来る•••

NIR excess無し
variability
detectable levelの降着率• hydrodynamic simulationでも予言される構造[Dodson-Robinson&Salyk2011]28

Implications for Planet Formation
The Astrophysical Journal, 745:5 (12pp), 2012 January 20

Kr• LkCa15, TChaとよく似た物
理量を持つ• inner hole内にfaint objectあり• 観測天体は重い円盤だが低降
着率=>accreting objectの存在

Figure 3. Left: the transitional disk around LkCa 15, as seen at a wavelength of 850 µm (Andrews et al. 2011). All of the flux at this wavelength isdust in the disk; the deficit in the center denotes an inner gap with radius of ∼55 AU. Right: an expanded view of the central part of the cleared reg
composite of two reconstructed images (blue: K " or λ = 2.1 µm, from 2010 November; red: L" or λ = 3.7 µm, from all epochs) for LkCa 15. The
central star is also marked. Most of the L" flux appears to come from two peaks that flank a central K " peak, so we model the system as a central sta
point sources.

• 観測天体(+LkCa15など)はrunaway gas accretion phase?
3.2. Orbital, Morphological, and Atmospheric Properties

The observed morphology of LkCa 15’s candidate companion
is more complicated than that of older directly imaged exoplanets, which are seen as unresolved point sources (Marois et al.
2008; Kalas et al. 2008; Lagrange et al. 2009). The flux is mostly
concentrated in a single unresolved location at 2.1 µm, but it isclearly extended at 3.7 µm. The most simple interpretation isthat the central source is therefore a newly formed exoplanet,
which emits significant flux at 2.1 µm due to either a warm
atmospheric temperature or accretion of hot material. The surrounding 3.7 µm dominated emission would then trace extended
circumplanetary material, most likely as it is accreting down tothe planet, though perhaps as it accretes past the planet and onto
the inner disk (e.g., Dodson-Robinson & Salyk 2011). We canextrapolate the orbital radii, absolute magnitudes, and colors ofthese structures from our global fit of all observations (Table 2,bottom section) using the apparent magnitudes, distance, andage for LkCa 15 which we describe further in Appendix.
We converted the observed separation and P.A. for eachsource into a deprojected orbital radius using the observed
disk geometry (i = 49◦ , P.A. = 241◦ ; Andrews et al. 2011):

a spatially resolved region, then it could be sub
uncertainties. Since we are fitting a potentially res
as a point source, model mismatch could cause
astrometric errors. More seriously, if the emission
an extended dusty structure, then the centroid of
itself could change (with respect to that structur
over time. Even if the dust producing the L" emissio
at a Keplerian velocity, the emission from different
structure might wax or wane. A conservative estim
motion should be based on at least several additi
in order to determine the residuals around its app
velocity.
The observed contrasts can be converted inmagnitudes using the observed photometry for(Appendix) and the distance to Taurus–Auriga, 1(Torres et al. 2009); the combined absolute ma
color for all three components are ML" = 6.8 ±K " − L" = 1.7 ± 0.2 mag. Young hot-start planets
SEDs similar to L dwarfs, so assuming an29
approxim
ture of 1500 K and appropriate bolometric correcti
et al. 2002), then the corresponding bolometric l
Lbol = 2 × 10−3 L& , with an uncertainty of at lea• accretion shockで検出可能なluminosityを持つ• ~105yrが期待される。TDのfraction(~20%)と矛盾しない•

12年11月8日木曜日

steepなMIR excessを持つような天体だと更に低くなるImplications for Planet Formation• gravitational instability(GI)はあまり考えにくい• 比較的若い、円盤が重いフェーズ(<1Myr)• 円盤の外側•cooling timeがorbital periodより短い• GIで惑星を作るタイムスケールは~103yr程度• GIのlong time evolutionを調べる必要がある

30
12年11月8日木曜日

Summary• transition disk object RXJ1633.9-2442のSMAによる高分解能観測• inner hole構造を空間分解• SEDとビジビリティの同時フィッティング• 円盤パラメータの導出• sharpなinner edge
• hole内にさらに構造を持つ(空間分解不可)• multiple planetによるlarge gap形成が考えられる• core accretionシナリオのrunaway accretion phase• ALMAの観測へ• dynamics, dust evolution, etc.
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12年11月8日木曜日