ALMA Survey of Lupus Protoplanetary Disks. I. Dust and Gas Masses
We present the first high resolution sub millimeter 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 the Atacama Large Millimeter/Submillimeter Array (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 mm continuum and the (13)CO and C^(18)O 3 2 lines. We use the sub millimeter 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 an interstellar medium (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 >3s 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 3x 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 an 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.