ALMA survey of protoplanetary disks in Chamaeleon I: Dust and Gas Masses

Masses of protoplanetary disks limit the formation and future growth of any planet.  We use ALMA to survey 887um emission and CO isotopologue line emission in a near complete sample of protoplanetary disks in the 2 Myr Chamaeleon I star-forming region, to measure the disk dust mass and gas mass simultaneously. In this talk, I will discuss the scaling relation of stellar mass and disk dust mass, as well as its evolution. I will also discuss the low detection rate of 13CO (17 sources) and C18O (1 source) in this survey.  We calculate gas mass by comparing CO line luminosity to chemical model grids which include CO freeze-out and isotope-selective photodissociation.  Under the assumption of a typical ISM CO-to-H2 ratios of 10^-4, the resulting gas masses are implausibly low, with an average gas mass less than 0.1 Mjup, indicating an early start of giant planet formation. The faint CO line emission may instead be explained if disks have much higher gas masses, but freeze-out of CO or complex C-bearing molecules is underestimated in disk models.

Speaker: 
Long Feng
Location: 
1st Seminar Room, KIAA-PKU
Time: 
Wednesday, April 25, 2018 - 5:15pm to 6:15pm