ALMA SURVEY OF LUPUS PROTOPLANETARY DISKS I: DUST AND GAS MASSES

Abstract

We present the first high-resolution sub-mm survey of both dust and gas for a large population of protoplanetary disks. Characterizing fundamental properties of protoplanetary disks on a statistical level is critical to understanding how disks evolve into the diverse exoplanet population. We use ALMA to survey 89 protoplanetary disks around stars with M ⇤ > 0.1 M in the young (1-3 Myr), nearby (150-200 pc) Lupus complex. Our observations cover the 890 µm continuum and the 13 CO and C 18 O 3-2 lines. We use the sub-mm continuum to constrain M dust to a few Martian masses (0.2-0.4 M) and the CO isotopologue lines to constrain M gas to roughly a Jupiter mass (assuming ISM-like [CO]/[H 2 ] abundance). Of 89 sources, we detect 62 in continuum, 36 in 13 CO, and 11 in C 18 O at > 3 significance. Stacking individually undetected sources limits their average dust mass to. 6 Lunar masses (0.03 M), indicating rapid evolution once disk clearing begins. We find a positive correlation between M dust and M ⇤ , and present the first evidence for a positive correlation between M gas and M ⇤ , which may explain the dependence of giant planet frequency on host star mass. The mean dust mass in Lupus is 3⇥ higher than in Upper Sco, while the dust mass distributions in Lupus and Taurus are statistically indistinguishable. Most detected disks have M gas. 1 M Jup and gas-to-dust ratios < 100, assuming ISM-like [CO]/[H 2 ] abundance; unless CO is very depleted, the inferred gas depletion indicates that planet formation is well underway by a few Myr and may explain the unexpected prevalence of super-Earths in the exoplanet population.