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Observations of
Circumstellar Disks
around YSOs
Nagayoshi Ohashi, ASIAA
Kyoto Univ. 09.11.2009
Outline of Talk
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Brief introduction of the SMA Project
Star formation and disk formation/evolution
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Overview
Disks around PMSs; HD 142527
Disks around protostars; B335
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SMA Project
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Joint project of the SAO and ASIAA.
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SMA consists of eight 6-m telescopes operating at
submm wavelengths (1mm to 350 mm) at the top
of Mauna Kea.
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ASIAA joined the project in 1996.
ASIAA has delivered two telescopes with receiver
systems.
Currently 230, 345, and 690 GHz bands are under
regular operation.
The SMA was dedicated in November 2003.
The SMA is the fore-runner to ALMA.
Kyoto Univ. 09.11.2009
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Science using SMA
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Star formation
 Jet/outflow
 Circumstellar disks
 Magnetic field
Extragalactic
 Nearby galaxies/AGN
 High-z galaxies
Evolved stars
Astrochemistry
Solar system
Syfert/AGN
Magnetic field
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Outflow
Solar system
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Star and Planet Formation:
Optically invisible!
Overview
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A low-mass star (protostar) is formed in a dense
molecular cloud core through its gravitational
collapse.
The dense cloud becomes flatted (along the
associated magnetic field). The associated
magnetic field is also dragged inward.
A circumstellar disk is also formed around a
YSO.
A molecular outflow takes place at some point.
Infall is terminated and a dense core is
dispersed. The central star becomes optically
visible (T Tauri star).
Planets are formed in the circumstellar disk?
Takakuwa et al. 2003
Girart et al. 2006
Lada et al. 2003,
Alves et al. 2001
Dense molecular cloud
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Research on Protostellar Disks
and Protoplanetary Disks
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Formation of protostellar/protoplanetary
disks; early phase (class 0 or even
younger protostars)
Evolution of PSD/PPD; intermediate
phase (class I and II)
Dissipation of PPD/Planet formation; late
phase (class II and III)
Disks around massive stars and brown
dwarfs.
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HH211 SiO 8–7 at 0.2” (60 AU) resolution
Lee et al. ApJ in press
A possible velocity gradient across
the innermost pair of knots
~0.5 km /s at ~10 AU
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Dust Polarization & Magnetic Field
NGC1333/IRAS4A
345 GHz
Total Intensity and
Linear Polarization
(B field)
Crutcher (2006),
Girart et al. 2006
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Science, 313, 771
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Protoplanetary Disk:
the site of planet formation
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Protoplanetary disks (PPDs) are most
probable sites for planet formation.
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Important to understand their physical
conditions.
Common characteristics or more variety?
More than 150 extra-solar planets have been
discovered.
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More systems with hot Jupiters and high
eccentricity.
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MM High Resolution Images of PPDs
GM Aur (Dutrey et al. 1998)
1.3 mm cont
0.6” x 0.7”
(~80 AU x 100 AU)
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Geometry: compact, disklike structures
Kinematics: Kepler motions
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Protoplanetary disks with spiral arms
AB Aur @ 1.6 micron
HD 142527 @ 1.6 micron
Fukagawa et al. 2004
Fukagawa et al. 2006
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HD 142527
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Herbig Ae star (F6 IIIe; M* ~ 2Mo)
Subaru observations revealed that the disk
has a spiral arm (Fukagawa et al. 2006)
Subaru observations at MIR revealed a hole
in the disk (Fujiwara et al. 2006).
ASTE observations suggested existence of a
gas disk.
There was no mm interferometric
observations due to its low declination.
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HD142527:
Subaru Infrared Images
1.6 mm CIAO image
24.5 mm COMICS image
(Fukagawa et al. ‘06)
(Fujiwara et al. ‘06)
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SMA Observations of
HD142527
 12CO
3-2 and 340 GHz continuum
simultaneous observations
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One track with the compact configuration
One track with the extended configuration
1.2” x 0.6” for dust continuum
2.1” x 1.1” for 12CO 3-2
Ohashi & Momose (‘09, submitted)
SMA is a joint project between the SAO and the ASIAA.
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SMA Results:
340 GHz Continuum
HD 142527
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340 GHz continuum
distribution resembles to the
1.6 mm scattered emission.
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An arc-like structure enclosing
the central star
two peaks; one at the NE and
the other at the NW.
Peak positions are shifted to the
N as compared to those seen at
1.6 mm.
No clear emission on the
southern side.
Total flux density ~1.2 Jy
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SMA
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Result： CO
3-2
 12CO
also shows a
central hole, with
peak emissions
coincident with the
infrared features.
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SMA Results: Spiral arms in gas?
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12CO
3-2 Mean Velocity
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Clear velocity gradient from
NW to SE, which is probably
due to rotation.
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Additional velocity gradient
suggestive of non-circular
motion.
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Roughly consistent with
Kepler rotation around a 2Mo
star.
Disk axis is from NE to SW?
Any relationship with gas
possibly associated with the
spiral arm?
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12CO
3-2 Channel Maps
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Is 12CO 3-2 emission optically thin?
 12CO
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shows similar
structures to the dust
emission.
Low brightness
temperature (8.5 K).
Chiang & Goldreich ‘97
12CO
3-2 emission may be optically thin.
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HD142527: Disk Mass
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345 GHz total flux ~ 1.2 Jy, corresponding to 4.1E-2 Mo
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Gas/dust mass ratio 100; Tdust = 50K
 12CO
3-2 integrated flux ~ 15 Jy km/s, corresponding
6.6E-6 Mo.
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[H2]/[12CO] = 104; Tex = 50 K
The disk mass derived from 12CO 3-2 is factor of 10000
smaller that that derived from 345 GHz dust.
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CO depletion factor ~10000?
H2 dissipation factor ~10000?
Combination of CO depletion and gas dissipation?
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Unknown factors to estimate mass
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Dust temperature and CO excitation temperature
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b-index (mass opacity)
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Even if we assume Td=Tex=100 K, the mass
difference is still more than three orders of magnitude.
Even if we assume a smaller b-index, the mass derived
from dust becomes just a factor of 2 smaller.
CO depletion factor, f(co)
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Around TTSs, f(CO) has been estimated to be upto
~200. Since Td would be higher around Herbig Ae
stars, f(CO) would be less than 200.
Even if we take into account of these unknown factors, it
still seems to be difficult to explain the mass difference
of 4 orders of magnitude.
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Gas dispersal in disk by
photoevaporation
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Takeuchi et al. (‘05; see also Alexander &
Armitage ‘07) studied disk clearing processes.
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using a model taking into account combined
effects of viscous evolution, photoevaporation,
differential radial motion of dust grains and gas.
Around an Herbig Ae/Be star with more ionizing
photon, a gas-poor dust ring will be formed in 106
yr.
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Takeuchi et al. 2005
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A gap is created at
~17 AU (rg) by
photoevapolation
Inside the gap
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Outside the gap
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Both gas and dust
accrete onto star due
to viscosity.
Gas is gradually
evaporated from the
inner edge, and the
inner edge gets
larger.
Dust accumulates at
the inner edge.
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Protostellar Disks around
Protostars
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L1551 IRS5: Infalling Envelope
P-V diagrams
C18O (1-0) with NMA
(Momose et al. 1998)
A2
B2
0.1 Mo
 700AU km/s
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 r
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V  2GM   1.59M
r
1M   700AU
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1
Vrot  0.24 r
0.5
0.5
A1
B1
Mass ~0.08 M
Radius ~ 1200 AU
Kyoto Univ
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infall
0.5
km/s
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Freely infalling and slowly rotating
with angular momentum conserved
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L1551 IRS5: Formation of a
protostellar disk
SMA CS 7-6 Total Intensity
SMA CS7-6 mean velocity
NMA C18O 1-0
Takakauwa, Ohashi + 2003
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Specific Angular Momenta
around YSOs
Specific angular
momentum seems to
be constant within a
radius of ~6000 AU.
Ohashi et al. 1997
+ new data (Yen, Takakuwa, Ohashi 2009)
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B335 (IRAS 19347+0727)
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Class 0 Protostar
Lbol ~ 1.5 Lo, Tdust ~ 30 K
Associated with a well developed outflow
(e.g., Hirano et al. ‘88, ‘92)
Infall signatures were observed (Zhou et
al. ‘93; Choi et al. ’95; Saito et al. ‘99).
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SMA Observations of B335
 12CO, 13CO,
C18O 2-1 and 230 GHz
continuum simultaneous observations
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One track with the compact configuration
3.9” x 3.3” for dust continuum
3.7” x 3.2” for C18O 2-1
(Yen, Takakuwa, Ohashi ‘09, submitted)
SMA is a joint project between the SAO and the ASIAA.
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B335: 1.3 mm continuum
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Size ~ 740 AU x 350 AU
Mass ~ 0.027 Mo
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B335: C18O 2-1
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Size ~ 1500 AU
Partially affected by the
outflow.
Mass ~ 5.2 x 10-3 Mo
C18O depletion (fd ~10)
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B335:
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C O
2-1 kinematics
Vinfall ~ 0.31-0.44 km/s @ 370 AU, Mstar ~ 0.02-0.04 Mo,
Mass infall rate ~ 4.8-6.9 x 10-6 Mo/yr
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B335:
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C O
2-1 Kinematics (II)
No detectable velocity gradient along the N-S direction;
Vrot < 0.04 km/s @ 370 AU
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Specific Angular Momentum in B335
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4.6 x 10-3 km/s pc @ 20000 AU
5.4 x 10-4 km/s pc @ 1000 AU (Saito et al.’99)
7 x 10-5 km/s pc @ 370 AU (SMA results)
The specific angular momentum is not
conserved outside R ~ 370 AU.
If the specific angular momentum is
conserved within R ~370 AU, Rd ~ 6 AU
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With ALMA?
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Observations with spatially high dynamic
range (10-10000 AU scale)
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Observations with high sensitivity and
resolution
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Kepler disk formation; age estimation based on
the disk size?
Pick up the earliest phase of the disk formation.
Signature of the planet formation/disk dissipation.
Observations with a large sample.
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