Surface Density Structure in Outer Region of Protoplanetary Disk

Jul. 24th 2014 Nobeyama UMEiji Akiyama (NAOJ)

Munetake Momose, Yoshimi Kitamura, Takashi Tsukagosh, Shota Shimada, Masahiko Hayashi, Shin Koyamatsu

Importance of Outer Region of the Disk• How is disk gas cleared ?• How can planets form at a distant from a central star ?

Kalas et al. 2009

Fomalhaut

r = 119 AU

Power Law Disk Model

Power law description in surface density was introduced in the minimum mass solar nebula. (e.g. Kusaka et al. 1970, Weidenschilling 1977, Hayashi et al. 1985)

Discrepancy between Dust & Gas EmissionDiscrepancy in disk size has emerged between the extent of the dust continuum and molecular gas emission. Dust continuum: smaller size Gas emission: larger sizeExamples・ AB Aur (Pietu et al. 2005)

Continuum (2.8, 1.4mm) : 350±30 AU12CO(J=2-1) :

1050±10 AU

・ HD 163296 (Isella et al. 2007)Continuum (0.87-7mm) : 200±15 AU12CO(J=3-2) etc : 540±40 AU

Is the power law description really appropriate ?

Similarity Solution Disk Model Surface density is based on the theory of viscous evolution

(Lynden-Bell & Pringle 1974, Hartmann et al. 1998)

Radial temperature distribution　 Same as power-law disk model

power-law

similarity

x[AU]

y[A

U]

y[A

U]

x[AU]

log nH2

[1/cc]

Log r [AU]

Log

Σ(r

) [g

cm

-2]

rout

power-law

similarity

distance where Σ(r) starts decreasing exponentially

normalized surface density

C2

Examples of Similarity Solution

velocity [km s-1]

HD163296

R.A.

Dec

.

2 4 6 8 2 4 6 8 2 4 6 8

PowerSimilarity

Hughes et al. 2008

ALMA SVband7

color: CO(3-2)contour: continuum

10 100 1000r [AU]

CO(3-2)continuum

rc = 125 AU

de Gregorio-Monsalvo et al. 2013

10-2

10-3

10-4

10-1

10-1

10-2

10-3

10-0

CO

(3-2) [Jy/beam]

cont

inuu

m [

Jy/b

eam

]

10

8

6

4

2

Vel. [km

/s]

CO(3-2)

2

0

4

6

24

6

offs

et [

arcs

ec]

Gallery of Protoplanetary Disks (Radio)

Andrews et al. 2011 Mathew et al. 2012Brown et al. 2012 Cieza et al. 2012Isella et al. 2010

Object Details

distance [pc] SP type M* [M☉] Mdisk [M☉] inclination [deg.]

140 A2/3 2.3 0.029 38

• MWC 480 is bright Herbig Ae star with primordial disk.• Many people have observed and basic properties are well known.• No complex structures → easy to analyze the structure

Kusakabe et al. 2012 Acke & van den Ancker 2004

No complex structures

log λ[μm]

log

λFλ

[erg

cm

-2s-1

μm

]H-band

Subaru

Observation Details

TelescopeReciever

NRO45, ASTEBEARS, T100H/V, CATS345

Lines 12CO(1-0), 13CO(1-0), C18O(1-0), 12CO(3-2), 13CO(3-2)

Frequency 109 – 115 GHz, 330 – 345 GHz

Spatial res. ~ 15” (~2100 AU), ~ 23”(~3200 AU)

Velocity res. ~ 0.055 – 0.1 km/s

Integ. time 4.2h (2.0h on source)

System temp. 140 -350 K

Model Parameters・ Fixed parameters ： The results obtained by other observations applied

・ Free parameters ： Best fit parameters are searched

・ X （ 12CO) = 10000 ・ Local Thermal Equilibrium (LTE)

・ X （ 12CO) / X （ 13CO) = 60 ・ Hydrostatic Equilibrium

・ X （ 13CO) / X （ C18O) = 5

・ Outer radius 　　 ： rout (C2)・ Temperature 　　 ： T100 ・ Surface density ： Σ100

(C1)

distance [pc]

M* [M☉]

inclination [deg.]

p q

HD163296 140 2.3 38 1.0 0.5

Model Fit Results

Similarity solution shows better fit in multi-CO line observation → It supports viscous evolution

Akiyama et al. 2013

Observation Details

Lines 12CO(2-1), 13CO(2-1), C18O(2-1)

Frequency 219 – 230 GHz

Spatial res. ~ 0.68” x ~ 0.55”

FoV ~ 27”

Proj. baseline 16 – 400 m

Velocity res. 0.3 – 0.66 km/s

Integ. time 4.2h (2.0h on source)

System temp. 60 -180 K (0.8mm water vapor)

ALMA SV band 6

Results (ALMA SV band 6)

12CO(2-1)

13CO(2-1)

C18O(2-1)

0th 1st 2nd

Akiyama et al. submitted

Results (ALMA SV band 6)

12CO(2-1)

13CO(2-1)

C18O(2-1)

0th 1st 2nd

Akiyama et al. submitted

Vlsr [km s-1]

Flu

x D

ensi

ty [

Jy]

12CO(2-1) 13CO(2-1) C18O(2-1)

Successful Example of SS Model 1

Akiyama et al.

submitted

CO (2-1) 13CO (2-1) C18O (2-1)

PL

SS

700

Successful Example of SS Model 2rout = 700AU, p=1.0, θ=45°

T100 [K]

Σ100 [gm s-1] 12CO(J =3-2) 13CO(J =3-2) 12CO(J =1-0) 13CO(J =1-0)

0.001

12CO(J =3-2) 13CO(J =1-0) 13CO(J =3-2)4030

20

100

0

0.15

0.312CO(J =1-0)

1.5

3

0

-100

10

20

30

Tm

b [K

]

3

1.5

0

-1.5

Tm

b [K

]

40

-0.15

0

0.15

0.3

201510

50

-5201510

50

-5-10

0 2 4 6 8 10 12 Vlsr [km s-1]

0 2 4 6 8 10 12 Vlsr [km s-1]

0 2 4 6 8 10 12 Vlsr [km s-1]

0 2 4 6 8 10 12 Vlsr [km s-1]

Summary

1. MWC 480 was selected for its simple disk structure.

2. Similarity solution model is based on the viscous evolution. → Surface density tapers off gradually with distance.

3. Similarity solution reproduces the observation ・ Verified by NRO45/ASTE (single dish) and ALMA SV (interferometry) and data. ・ Similarity solution model is more suitable than power law for describing disks. → The disk evolves via viscous diffusion