Poster abstract

We present a compositional analysis of the 10mu and 20mu silicate emission features for brown dwarf disks in the Taurus star-forming region. The crystallinity level at larger radii in these brown dwarf disks has not decreased, which indicates efficient diffusion of crystalline material from the warm/inner region to the cold/outer parts in these sub-stellar disks. The grain growth levels do not show any particular trend with the radial distance. Most disks show similar large-grain mass fractions in the inner and outer disk regions. The disk structure in both the inner and outer regions is found to be more effected by the crystallinity level in the disk. The strengths in the 10mu and 20mu features are similar for most disks, except three cases where the disk has flared up at longer wavelengths. For nearly 80% of the disks, the mass fraction of small ISM-like dust grains is negligible (< 5%) in the outer disk region. For most sources, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be a factor of ~2 higher than the median for the higher mass T Tauri stars in Taurus. A (weak) anti-correlation between the X-ray emission strength and the extent of crystallinity in the disk is observed, suggesting X-rays to be an important dust amorphization agent in these disks.