Model SEDs of Massive YSOs
Barbara Whitney, Tom Robitaille, Remy Indebetouw, Kenny
Wood, and Jon Bjorkman
Do we need 2-D, 3-D models?
>100 m: no<100 m: yesExtremely young sources: maybe not (Osorio et al. 1999)
(van der Tak et al. 2000)
Outline• 2-D SED models
– Rotationally flattened envelopes, disks, bipolar cavities
• 3-D SED models– Clumpy molecular clouds
• Model grid and fitter • Focus on NIR/MIR spectra
– Lots of new data in this region (Spitzer)– 1-D models work fine for FIR/submm (Hatchell et
al. 2000, Buether et al. 2002, Mueller et al. 2002, Hatchell & van der Tak 2003, Williams et al. 2005)
Radiative Transfer Models
• Monte Carlo method• 3-D spherical polar grid• Calculates radiative equilibrium of dust
(Bjorkman & Wood 2001)• Non-isotropic scattering + polarization• Output: images + SEDs (+ polarization)• Not included: PAHs, stochastic heating
of small grains, optically thick gas emission
(Whitney et al. 2003a,b, 2004)
2-D YSO Model Geometry• Rotationally-flattened infalling envelope
(Ulrich 1976)• Flared disk• Partially evacuated outflow cavity
L*=40000T*=4000M*=17.5M=10-4
Md=1
Embedded Massive YSO
i Av
0 6
60 53
90 3e4
.
Embedded Massive YSO - No Cavity
i Av
0 45
60 68
90 3e4
L*=40000T*=4000M*=17.5M=10-4
Md=1
.
Massive Star+Disk
i Av
0 0
60 0.1
90 3e3
L*=40000T*=30000M*=17.5Md=0.1
Low-Mass Star + Disk
i Av
0 0
60 0.1
90 3e5
L*=40000T*=4000M*=17.5Md=0.01
Color-color plots (Spitzer IRAC)
o High-mass YSO
o High-mass YSO
X High-mass disk o Low-mass YSO
x Low-mass Disk
Allen et al (2004) disk domain
T*=30000 KT*=4000 KReddening
Vectors:AV=30
Summary of 2-D models
• Central star + disk spectrum contributes to SED, even in young embedded sources in 2-D geometries.
• Massive sources are redder in 3-8 m region than low-mass even for the same envelope Av.
3-D models
• Motivation– UCHII regions: 1-D models of mid-IR
spectra give too deep 10 m absorption for a given FIR flux, and too steeply rising SED in NIR/MIR (Faison et al. 1998, van der Tak et al. 2000)
Model Ingredients
• O star in a molecular cloud
• Use fractal ISM structure, D=2.6 (Elmegreen 1997)
• Average radial density profile is varied from r0 to r-2.5
• Smooth-to-clumpy ratio is varied from 3% to 100%
(Indebetouw et al. 2005)
Courtesy of Remy Indebetouw
IRAC MIPS
Images & SpectraNIR
Color-color plots
Smooth model
200 sightlines from 1 clumpy model
Fits to Data: G5.89-0.39
Best smooth modelBest clumpy modelGrey lines show other sight lines
Mid-IR data: Faison et al. (1998)
G5.89 Model parametersTstar 41000 K
L 2.54x105
Rin 0.0001 pc
Rout 2.5 pc
Menv 50000
Av_ave 131
Smooth/Clumpy 10%
Radial density ave~r0
Fractal dimension 2.6
All the UCHII Observations
Grey lines: G5.89 best model
Mid-IR data: Faison et al. (1998)
3-D Model summary
• UCHII regions may be O-B stars still embedded in their natal molecular clouds but not surrounded by infalling envelopes.
• Bolometric flux of clumpy models varies by a factor of 2 lower and higher than the true luminosity depending of viewing angle
(Indebetouw et al. 2005)
2-D/3-D Model grid + Data fitter
• Motivation: fitting GLIMPSE/2MASS data (7 bands from 1-8 m) of the inner galactic plane. (see Indebetouw talk). GLIMPSE has observed hundreds of massive star formation regions.– 24 m data will be available in the future
(Robitaille et al. 2005)
Grid Parameters (current)Stellar Mass 0.1-40 Msun
Stellar Age 104-107 yrs
Envelope Infall Rate 10-4-10-9 Msun/yr*Mstar
Disk Mass 10-1-10-8 Msun*Mstar
Disk Radius 10-1000 AU
Cavity Size 10-50 degrees
Aperture 1000, 5000, 20000 AU
Viewing Angles 10
1600 models completed in 2 weeks on 8 Mac G5 processors
Model grid: All Embedded YSOs
< 2 Msun2 < Msun < 5 > 5 Msun
All Disk (opaque) Sources
< 2 Msun2 < Msun < 5 > 5 Msun
Disks with Inner holes
Allen et al.Disk domain
All Disk (optically thin) Sources
< 2 Msun2 < Msun < 5 > 5 Msun
Disks with Inner holes
Allen et al.Disk domain
Embedded YSOs - 4 kpc*
< 2 Msun2 < Msun < 5 > 5 Msun
*AssumingGLIMPSEsensitivities
Opaque Disks - 4 kpc
< 2 Msun2 < Msun < 5 > 5 Msun
Inner holes
Allen et al.Disk domain
Optically thin disks - 4 kpc
< 2 Msun2 < Msun < 5 > 5 Msun
Inner holes
Allen et al.Disk domain
All Sources - 4 kpc
Embedded YSOOpaque disksThin disks
High massYSOs; and disks with inner holes
High mass(opaque and thin)Disks with inner holes
Embedded YSOand disks with noinner holes
Embedded YSOsand reddenedDisks
Fitter Description
• Uses linear regression to determine best fit to data
• Convolves models with any desired filter functions
• Distance and extinction range can be specified• Designed to work with large numbers of sources
– Fits 100 sources per second
• Produces statistics on quality and fit parameters
(Robitaille et al. 2005)
Tests on M16
data
Embedded Disk Embedded or disk
Future work• Expand grid
– More variations in model parameters– Add 3-D clumpy models– Use info from recent work (e.g., disks: Beuther et
al. 2004, Beltran et al. 2005 theory: McKee & Tan 2003), this meeting, and models of individual sources
• More testing of Model Fitter• Make grid & fitter publicly accessible with
batch jobs (web access)• RT:
– add PAHs and stochastic heating of small grains– Multiple emission sources