Imaging gaps in disks at mid-IR VLT VISIR image 8.6 PAH 11.3 PAH 19.8  m large grains => gap! Geers et al 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., Spitzer can detect gas-phase lines in spite of low spectral resolution - Gas is hot: 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 IRS43 CRBR T ex ~ 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 C 2 H 2 abundances ~10 -5 w.r.t. H 2 consistent with high-T models=> First probe of organic chemistry in planet-forming zones

Silicate line profiles (continuum subtracted) Bouwman et al Van Boekel et al Przygodda et al  m 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,  m band20  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 20  m data Kessler-Siliacci et al. 2006, 2007 Van Boekel et al. 2003, 2005 Przygodda et al 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 i~85 o => Very weak at mid-IR Scattered radiation 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 Crovisier et al Merin et al Apai 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 Lahuis et al Pascucci et al T Cha - Detected in at least 20% of sources - Fluxes consistent with recent models of X-ray irradiated disks