Finding Pebbles in Protoplanetary Disks

We request observations of protoplanetary disks in order to investigate the presence of dust particles up to pebble sizes. Along with our pre-existing 3mm data, these new observations will establish the contributions of various emission mechanisms, e.g. thermal dust versus free-free, by revealing a change in the slope of the spectral energy distribution (SED). These observations will help constrain models of dust growth and planet formation in the disks. Specifically, we propose to (1) monitor the 1.3cm and 1.6cm emission from three sources to check for variability, (2) obtain high-resolution observations of two of these sources at 1.3cm in order to spatially resolve the disks and obtains brightness temperatures, (3) complete our 3mm observations of HD100546 to attempt to resolve the disk and compare with the previously determined 16mm size and to detect molecular emission to probe the disk chemistry and kinematics, and (4) to obtain 7mm fluxes for all three sources to complete their SEDs.