Presentation on theme: "Dust emission from Haebes: Disks and Envelopes A. Miroshnichenko (Pulkovo/Toledo) Z. Ivezic (Princeton) D. Vinkovic (UK) M. Elitzur (UK) ApJ 475, L41 (1997;"— Presentation transcript:
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 < M c PMS STARS MS STARS M > M c MS STARS
Envelope evolves on free-fall time scale: t ff = 2x10 5 (10 4 cm -3 /n) 1/2 years Hydrostatic PMS low-mass (M 3M ) core evolution: t pms ~ 3x10 7 (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: I = B (T), need temperature distribution
Illuminated Disk Heating: Cooling: F em = T 4 Balance: T r -3/4 (accretion too!) yields: 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
St eady-state accretion to point source: Free fall: i.e. v r -½ so
SCALING Ivezic & 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/
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?
Implications: Disk + Envelope resolves all discrepancies 2 distributions: Disk: compact mm emission Envelope: IR emission Disk heating ~ 10 -8 M yr –1, L acc ~ 0.1 L v ~ 0.1 no molecules SED + multi- imaging essential for finding disks
??? Uniqueness ??? Disk surface layer may mimic shell Equivalent envelope: V R * /R sub However: V ~ 0.1, R * /R sub ~ 0.01 Chiang & Goldreich 97: