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 μm 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 >3σ 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 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.
© 2016 The American Astronomical Society. Received 2016 February 16; revised 2016 May 5; accepted 2016 May 15; published 2016 August 29. M.C.A. and J.P.W, were supported by NSF and NASA grants AST-1208911 and NNX15AC92G, respectively. M.C.A. acknowledges student observing support from NRAO. N.M. is supported in part by the Beatrice W. Parrent Fellowship in Astronomy at the University of Hawaii. Leiden is supported by the European Union A-ERC grant 291141 CHEMPLAN, by the Netherlands Research School for Astronomy (NOVA), and by grant 614.001.352 from the Netherlands Organization for Scientific Research (NWO). C.F.M. gratefully acknowledges an ESA Research Fellowship. We thank J.M. Alcalá for providing VLT/X-Shooter spectra for deriving stellar parameters, Ilse Cleeves for providing ALMA continuum and integrated line fluxes for Sz 82 (IM Lup), and Scott Barenfeld for providing ALMA continuum fluxes for Upper Sco sources in advance of publication. We also thank Sean Andrews for his extremely useful comments. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2013.1.00220.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
Submitted - 1604.05719v4.pdf
Published - apj_828_1_46.pdf