Observing grain growth in protoplanetary disks

Abstract

In order to understand planet formation, we need to probe the physical conditions of protoplanetary disks to see when and where grains begin to grow in size. Over the past four years we have been conducting a 3mm continuum survey with the Australia Telescope Compact Array of disks around young stars (both T Tauri and Herbig Ae/B stars) in southern molecular clouds to investigate the evolution of protoplanetary disks and grain growth within these disks. The goals of our project are to obtain fluxes and hence determine the millimetre spectral energy indices, which provides information about the grain size distribution. We present results from our successful 2005 millimetre season, in which we observed 15 southern T Tauri sources (10 in Chamaeleon and 5 in Lupus). The opacity indices suggest the presence of mm-sized dust aggregates and hence substantial grain growth in the majority of these disks. We also present preliminary results from our follow-up 2006 observations of three sources (HD100546, WW Cha and RU Lup) are centimetre wavelengths and discuss the possibility of detecting pebble-sized "grains" in these disks.