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 $M_{ast}>0.1~M_{odot}$ in the young (1--3~Myr), nearby (150--200~pc) Lupus complex. Our observations cover the 890~$mu$m continuum and the $^{13}$CO and C$^{18}$O 3--2 lines. We use the sub-mm continuum to constrain $M_{rm dust}$ to a few Martian masses (0.2--0.4~$M_{oplus}$) and the CO isotopologue lines to constrain $M_{rm gas}$ to roughly a Jupiter mass (assuming ISM-like $rm {[CO]/[H_2]}$ abundance). Of 89 sources, we detect 62 in continuum, 36 in $^{13}$CO, and 11 in C$^{18}$O at $>3sigma$ significance. Stacking individually undetected sources limits their average dust mass to $lesssim6$ Lunar masses (0.03~$M_{oplus}$), indicating rapid evolution once disk clearing begins. We find a positive correlation between $M_{rm dust}$ and $M_{ast}$, and present the first evidence for a positive correlation between $M_{rm gas}$ and $M_{ast}$, which may explain the dependence of giant planet frequency on host star mass. The mean dust mass in Lupus is 3$times$ higher than in Upper Sco, while the dust mass distributions in Lupus and Taurus are statistically indistinguishable. Most detected disks have $M_{rm gas}lesssim1~M_{rm Jup}$ and gas-to-dust ratios $<100$, assuming ISM-like $rm {[CO]/[H_2]}$ 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.
تحميل البحث