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