Dust emission from Haebes: Disks and Envelopes

A. Miroshnichenko (Pulkovo/Toledo)

Z. Ivezic (Princeton)

D. Vinkovic (UK)

M. Elitzur (UK)

• ApJ 475, L41 (1997; MIE)• ApJ 520, L115 (1999; MIVE)• in progress (VMIE)

CLOUD COMPRESSION

COLLAPSE

FRAGMENTATION

PROTOSTRAS

M < Mc

PMS STARS

MS STARS

M > Mc

MS STARS

• Envelope evolves on free-fall time scale:

tff = 2x105 (104 cm-3/n)1/2 years

• Hydrostatic PMS low-mass (M 3M) core

evolution:

tpms ~ 3x107(M/M)3 years

M 2 M T-Tauri

2 M M 10 M Herbig Ae/Be

M 10–15 M no PMS

Protostellar Accretion Disks

• R ~ 10 — 100 AU

• M ~ .01 — .1 M

Evidence in pre-main-sequence:

T Tau stars (M 2 M)

? Herbig Ae/Be stars (2 M M 10 – 15 M)

IR ?

Required properties:

Emission from constant-T dust:I = B(T)[1 - exp(-)]

• Optically thick: I = B(T)

• Optically thin: I = B(T)

Protostellar Accretion Disks

Geometrically thin, optically thick:

22

3

R

M~

R

nRnR~

I = B(T), need temperature distribution

Illuminated Disk

• Heating:

• Cooling: Fem = T4

• Balance: T r -3/4 (accretion too!)

yields:

FL

rrabs * sin

4 23

F -4/3

r

Hillenbrand et al ‘92

• Group 1 (30):

F -4/3, disks

• Group 2 (11):

flat or rising SED,

star/disk with

additional shell

• Group 3 (6):

small IR excess

Problems:

• Hartman et al ’93: accretion rates are excessive

• Di Francesco et al ’94: group 1 IR emission is extended!

Spherical, optically thin shell:

T r -1/2

with

r -p, -

get

F -(p - 1)( + 4)/2

Since ~ 1–2, p ~ 3/2 gives

F -4/3

Steady-state accretion to point source:

vr4M 2

Free fall:

rGM2

v2

i.e. v r-½

so

2/32

rvr4

M

SCALINGIvezic & Elitzur ’95,’97

Depends mostly on• type of dust grains• overall optical depth• density profile

DOES NOT depend on• dimensions• density scale• luminosity

The emission from radiatively heated dust

DUSTY: http://www.pa.uky.edu/~moshe/dusty/

MIE ’97:

r -3/2

Mannings & Saregnt ’97:

2.6 mm incompatible with MIE:

V ~ 102–103 — nonsense!

In particular

MWC480 MWC683

MS V > 103 600

MIE V = 0.4 0.3

Conclusion: DISKS!

indeed:

However…

• IR best explained with optically thin shells, inconsistent with mm

• mm emission best explained with optically thick disks, inconsistent with IR

Extrapolate from 2.6 mm with F 1/3 — too little 2.2 m!

Also, MWC 137 imaging:

(50 m) = 66” 2”

(100 m) = 58” 2”

How can that be?

Disk Imbedded in Envelope:

Disk Imbedded in Envelope:

envelope ( -1.5):

T r –0.36

“standard” disk:

T r –0.75

• At the same radius, disk is cooler than envelope

• Smaller disk still contains cooler material

envelope

disk

MIVE ‘99

f = f,disk + (1 - )f,env

Implications:

• Disk + Envelope resolves all discrepancies

• 2 distributions: Disk: compact mm emission Envelope:

• IR emission• Disk heating

• ~ 10-8 M yr –1, Lacc ~ 0.1 L

v ~ 0.1— no molecules

• SED + multi- imaging — essential for finding disks

exM

??? Uniqueness ???

• Disk surface layer may mimic shell

• Equivalent envelope: V R*/Rsub

• However: V ~ 0.1, R*/Rsub ~ 0.01

Chiang & Goldreich ’97:

AB Aur:

Images:

Grady et al ‘97 Mannings & Sargent ‘97

NICMOS

Marsh et al ‘95VMIE, in progress

Herbig, 1960:

15 min exposure:

60 min exposure:

3’

AB Aur

SU Aur