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