Imaging gaps in disks at mid-IRVLT VISIR image
8.6 PAH 11.3 PAH 19.8 m large grains => gap!
Geers et al. 2007
IRS48
-Gap seen in large grains, but NOT in PAHs => separation small and large grains
A big surprise:Gas-phase lines toward IRS46 disk
Low-mass: IRS46
Lahuis et al., 2006
- Spitzer can detect gas-phase lines in spite of low spectral resolution- Gas is hot: 400-700 K- Abundances factor 1000 larger than in cold clouds - Must arise within inner 11 AU => inner disk- Potential blue-shift by 20 km/s => disk wind?
IRS46
IRS44
IRS43CRBR2422.8
Tex~400-700 K
10’’
Hot chemistry in inner 10 AU of disks
- Line of sight through puffed-up inner rim produces large enough column and T- HCN and C2H2 abundances ~10-5 w.r.t. H2 consistent with high-T models=>
First probe of organic chemistry in planet-forming zones
Silicate line profiles(continuum subtracted)
Bouwman et al. 2001Van Boekel et al. 2003Przygodda et al. 2003
0.1m
2.0 m
- Ratio of 11.3/9.7 m fluxes is measure of flatness of profile
Large fraction of T Tauri disks shows evidence for grain growth
Models
Data
Kessler-Silacci et al. 2006,2007
10 m band 20 m band
Obs
Model
- No correlation grain growth with age, Ha (accretion rate)- Trend for more grain growth around M-type stars
Statistical analysis 10 m band
- Large fraction of disks shows evidence for grain growth to a few m (first step in planet formation process)- Similar conclusion from 20m data
Kessler-Siliacci et al. 2006,2007
Van Boekel et al. 2003, 2005 Przygodda et al. 2003
Large Small
Evidence for grain growth– edge-on disks
Shape and depth of mid-IR “valley” very sensitive to grain size. For this source, grains at least ten m in size are inferred.
“Flying Saucer” in Oph
Pontoppidan et al. 2007
i~85o
=> Very weak at mid-IR
Scatteredradiation
Thermal radiation
Crystallinity
ISO: Herbig stars Spitzer: T Tauri stars and Brown Dwarfs
- Crystallinity seen in large fraction of T Tauri + BD disks (>50%)- Interstellar silicates amorphous => crystallization at > 800 K must have occurred in inner disk => provides constraints on efficiency of heating and mixing processes- Also seen in comets => mixing in our solar system was more significant than thought before
Malfait, Waelkens et al. 1998Crovisier et al. 1997
Merin et al. 2007Apai et al. 2005
Spitzer results on PAHs 3/ 37 T Tauri stars show PAH
Mostly G stars detected, not K PAHs as tracers of stellar
radiation and disk shape Enhanced UV compared with stellar
BB for some objects => accretion? chromosphere?
Absence in majority objects due to low PAH abundance
7.7 and 8.6 m bands sometimes masked by silicate emission
RR Tau
Optical, UV PAH
Geers et al. 2006
[Ne II] in disks: tracer of X-ray/EUV radiation?
Geers et al. 2006Lahuis et al. 2007Pascucci et al. 2007
T Cha
- Detected in at least 20% of sources- Fluxes consistent with recent models of X-ray irradiated disks