Speaker
Description
With the advent of ALMA, complete surveys of protoplanetary disks are being carried out in different star forming regions with the attempt to simultaneously constrain the gas and dust disk masses as well as the gas/dust mass ratio. More specifically, continuum and CO isotopologues observations are used to trace the bulk of the dust and the gas respectively. The main result from such surveys is that CO-based gas masses are very low, often smaller than one Jupiter Mass. Moreover, gas/dust mass ratios are much lower than the value of 100 found in the ISM. This can be interpreted either as rapid loss of gas, or as a chemical effect removing carbon from CO and locking it into more complex molecules or in larger bodies. Previous data cannot distinguish between the two scenarios. Statistical analysis of the gas and dust contents have been investigated providing some hints on the nature of these low gas/dust ratio values. Observations of [CI] lines and more complex C-bearing molecules could help us measuring the volatile carbon abundance in disks and determining whether carbon depletion, rather than gas depletion, is at play. Hydrocarbons, such as C2H and c-C3H2, are shown to be good tracers of the carbon abundance and C/O ratio in disks, thus they are promising species to calibrate CO-based disk masses and gas/dust ratios.
