Post on 17-Jan-2016
description
Molecular Hydrogen Emission
from Protoplanetary
DisksHideko Nomura (Kobe Univ.), Tom Millar (UMIST)
Modeling the structure, chemistry and appearance of protoplanetary disks
§1 Introduction
106yr 107yr
Obs. of Protoplanetary Disks
SED of TTS + disk
(Chiang & Goldreich 1997)
CentralStar
Disk
StarDisk
(Andre et al. 1994)
CTTS WTTS
Observations of H2 Line Emission
NIR GG Tau, TW Hya, LkCa 15, DoAr25 (v,J)=(1,3)-(0,1) by NOAO (Bary et al. 2003)
MIR GG Tau, GO Tau, LkCa 15 J=2-0, J=3-1 by ISO (Thi et al. 2001)
UV TW Hya 146 Lyman-band H2 lines by HST, FUSE (Herczeg et al. 2002) etc.
H2 Transition Lines UV pumping
UV fluorescentline emission
Infraredquandrapolar
cascades
v=0
UVpumping
continuousfluorescenc
e(UV)H+H
radiativecascade (IR)
collisionalexcitation,
de-excitation
(Shull & Beckwith 1982)
UV radiation fieldTemperature
profile
Collisional process level populations
Irradiation from central star
H2 level transitions via UV
pumpingHeat gas & dust
in disks
Irradiation from Central Star
(Chiang & Goldreich 1997)
CentralStar
Disk
Radiative transfer process Global physical disk structure (gas & dust temperature, and density profiles) H2 level populations & line emission
§2 Disk Model
Gas Density & TemperatureHydrostatic equilibrium in z-direction
zρΩρgdz
dρc 2
z2s
★
z
xcs
2=2kT/mp
(x)=1.4x10-7 s-1(x/1AU)-3/2 (M*=0.5 Ms )Macc=10-8Ms/yr (=const.)
・
Thermal equilibrium (pe+Lgr-line=0) pe : Grain photoelectric heating by FUV line :Cooling by OI, CII & CO line excitation Lgr : Energy exchange by collisions between gas and dust particles
Dust TemperatureLocal radiative equi. (abs.=reemission)
0 grνν0 νν )(TB κdν4dΩI κdν
2D radiative transfer equationShort characteristic
method in spherical coordinate(Dullemond & Turoulla 2000)
Heating sources:(A) viscous heating at equatorial plane(B) radiation from central star
Stellar blackbody(T*=4000K)
+ Thermal bremsstrahlung
(Tbr=2.5 x 104K)
UV Radiation from Central Star
UV excess
(Costa et al. 2000)
TW Hya
Resulting Temperature Profile
R=0.1AU
1AU
10AU
with UV excess without UV excessR=0.1AU
1AU
10AU
Disk surface heated up by photoelectric heatingMidplane & Outer disk (without UV excess) gas temp. = dust temp.
§3 H2 Level Populations
H2 Level PopulationsStatistical Equilibrium
lform,lm s
smlmlml2m
ldiss,lm s
slmlm2l
n(H)Rn(s)CβA)(Hn
Rn(s)Cβ)(Hn
u, B1u+ , C1u
m, X1g+
l, X1g+
UVlm
UV ml
Aml CmlClm
H+HRdiss,l
H+H
Rform,lEm>El
Resulting Level Populations
R=0.1AU
10AU
with UV excess without UV excess
with UV excess or Inner disk (hot) : LTE collisional process, nupper: largeOuter disk without UV excess (cold) : non-LTE UV pump. & cascade, nupper: small
R=0.1AU
10AUv=0v=1 v=2 v=3v=4
v=0 v=1 v=2 v=3 v=4
v=1-0 S(1) (@2.12m) Obs.(Bary et al.’03) with UVe without UVe (1.0 - 15) x 10-15 9.3 x 10-15 3.3 x 10-18
ObserverIul
Sul
§4 Resulting H2 Line Emission
IR
)S(Iαdz
dIululul
ul 4π
hνΦAn
α
1S ul
ululuul
ul
[erg/cm-2/s]
e.g., v=1-7 R(3) (@1489.6A) Obs.(Herczeg with with UVe without et al.’02) UVe + LyUVe 4.8 x 10-14 1.4 x 10-14 1.3 x 10-16 4.0 x 10-22
UV with UV excess:UV: nu: Iul:
with UV excess:Tgas: nu: Iul:
[erg/cm-2/s]
§5 Discussion
Dustless Disk ModelPlanet formation
Dustless disk model
ISgas
dust small4
gas
dust small
n
n10
n
n
Dustless disk :no infrared excess
Conserv. of dust mass& dust size growth
amount of small dust
SED
Resulting Temperature Profile
R=0.1AU
1AU
10AU
R=0.1AU
1AU
10AU
Dusty Dustless
Dustless (ndust/ngas: small) grain photoelectric heating Tgas
with UV excess
Resulting Level Populations
R=0.1AU
10AUv=0v=1 v=2 v=3v=4
Dusty Dustlesswith UV excess
Outer region of dustless disk (cold) : non-LTE UV pump. & cascadenupper: large UV radiation fields dust absorption
R=0.1AU
10AU
v=0v=1 v=2 v=3 v=4
Resulting H2 Line Emission
v=1-0 S(1) (@2.12m): Obs.(Bary et al.’03) Dusty Dustless (1.0 - 15) x 10-15 9.3 x 10-15 6.5 x 10-16
S(0) (@28.2m), S(1) (@17.0m): Obs.(Thi et al.’01) Dusty Dustless S(0) (2.5 – 5.7) x 10-14 4.2 x 10-17 9.3 x 10-17
S(1) (2.8 – 8.1) x 10-14 8.5 x 10-16 5.0 x 10-16
UV (@900A-2900A) Obs.(Herczeg et al.’02) Dusty Dustless (1.2 - 73) x 10-15 3.8 x 10-15 1.2 x 10-14
[erg/cm-2/s]
Obs. possibility to detect H2 emission from dustless disks in NIR
& UV
§6 SummaryUV excess + Radiative transfer processGas & dust temperature, density profiles
Gas temperature@disk surface: ~2,000K Grain photoelectric heating
H2 level populations : LTE, nupper: large
Strong NIR H2 lines : consistent with obs. collisional excitation (hot gas) Strong UV H2 lines : consistent with obs. pumping by Ly emission
H2 emission from dustless disks