Influence of planetary gas accretion on the shape and depth of gaps in protoplanetary discs

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
e-mail: bergez@mpia.de
² Laboratoire d’Astrophysique de Bordeaux, CNRS and Université de Bordeaux, Allée Geoffroy St. Hilaire, 33165 Pessac, France
³ Université Côte d’Azur / Observatoire de la Côte d’Azur - Lagrange (UMR 7293), Boulevard de l’Observatoire, CS 34229, 06300 Nice, France

Received: 30 April 2020
Accepted: 30 September 2020

Abstract

It is widely known that giant planets have the capacity to open deep gaps in their natal gaseous protoplanetary discs. It is unclear, however, how gas accretion onto growing planets influences the shape and depth of their growing gaps. We performed isothermal hydrodynamical simulations with the Fargo-2D1D code, which assumes planets accreting gas within full discs that range from 0.1 to 260 AU. The gas accretion routine uses a sink cell approach, in which different accretion rates are used to cope with the broad range of gas accretion rates cited in the literature. We find that the planetary gas accretion rate increases for larger disc aspect ratios and greater viscosities. Our main results show that gas accretion has an important impact on the gap-opening mass: we find that when the disc responds slowly to a change in planetary mass (i.e., at low viscosity), the gap-opening mass scales with the planetary accretion rate, with a higher gas accretion rate resulting in a larger gap-opening mass. On the other hand, if the disc response time is short (i.e., at high viscosity), then gas accretion helps the planet carve a deep gap. As a consequence, higher planetary gas accretion rates result in smaller gap-opening masses. Our results have important implications for the derivation of planet masses from disc observations: depending on the planetary gas accretion rate, the derived masses from ALMA observations might be off by up to a factor of two. We discuss the consequences of the change in the gap-opening mass on the evolution of planetary systems based on the example of the grand tack scenario. Planetary gas accretion also impacts stellar gas accretion, where the influence is minimal due to the presence of a gas-accreting planet.