Evidence for a correlation between mass accretion rates onto young stars and the mass of their protoplanetary disks

¹ Scientific Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
e-mail: cmanara@cosmos.esa.int
² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB30HA, UK
³ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
⁴ INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁵ Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching bei München, Germany
⁶ School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliams Place, 2 Dublin, Ireland
⁷ INAF/Osservatorio Astronomico di Capodimonte, Salita Moiariello, 16 80131 Napoli, Italy
⁸ Institute for Astronomy, University of Hawai’i at Mänoa, Honolulu, HI, USA
⁹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
¹⁰ California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125, USA
¹¹ University of Hawaii, Department of Physics and Astronomy, 2505 Correa Rd. Honolulu, HI 96822, USA
¹² Observatório Nacional/MCTI, 20921-400, Rio de Janeiro, Brazil
¹³ Max-Plank-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany

Received: 18 March 2016
Accepted: 18 May 2016

Abstract

A relation between the mass accretion rate onto the central young star and the mass of the surrounding protoplanetary disk has long been theoretically predicted and observationally sought. For the first time, we have accurately and homogeneously determined the photospheric parameters, mass accretion rate, and disk mass for an essentially complete sample of young stars with disks in the Lupus clouds. Our work combines the results of surveys conducted with VLT/X-Shooter and ALMA. With this dataset we are able to test a basic prediction of viscous accretion theory, the existence of a linear relation between the mass accretion rate onto the central star and the total disk mass. We find a correlation between the mass accretion rate and the disk dust mass, with a ratio that is roughly consistent with the expected viscous timescale when assuming an interstellar medium gas-to-dust ratio. This confirms that mass accretion rates are related to the properties of the outer disk. We find no correlation between mass accretion rates and the disk mass measured by CO isotopologues emission lines, possibly owing to the small number of measured disk gas masses. This suggests that the mm-sized dust mass better traces the total disk mass and that masses derived from CO may be underestimated, at least in some cases.