event
Thursday 17 Sep 2009: Coagulation and crystallization of silicates in protoplanetary disks: a c2d Spitzer/IRS survey
Johan Olofsson - Laboratoire d'Astrophysique de Grenoble, France
Physics, 4th Floor interaction area 12:00-13:00
The dust grains in the planet forming regions around young stars are expected to be heavily processed due to coagulation, fragmentation and crystallization, and mixed both radially and vertically due to turbulence. As part of the Cores to Disks (c2d) Legacy Program, I obtained more than a hundred Spitzer/IRS spectra of TTauri stars, over a spectral range of 5-35 micron where many silicate solid-state features are present. During this seminar, I will present the results of a study of the crystalline silicate grains in protoplanetary disks, for a statistically significant number of TTauri stars (96). I will show that the IRS spectra essentially probe two independent disk regions: a warm zone emitting at 10 micron and a much colder region emitting at 20 micron, and that grains have grown in both disk regions. I also identify a 'crystallinity paradox', as crystalline silicate features are 3.5 times more frequently detected in colder regions than the crystalline features arising from much warmer disk regions, suggesting that the disk has an inhomogeneous dust composition within 10 AU. I will then discuss the implications for our understanding of the dynamical processes at play in planet forming regions about young stars.
