Increased isolation mass for pebble accreting planetary cores in pressure maxima of protoplanetary discs

Abstract

The growth of a pebble accreting planetary core is stopped when reaching its isolation mass that is due to a pressure maximum emerging at the outer edge of the gap opened in gas. This pressure maximum traps the inward drifting pebbles stopping the accretion of solids on to the core. On the other hand, a large amount of pebbles should flow through the orbit of the core until reaching its isolation mass. The efficiency of pebble accretion increases if the core grows in a dust trap of the protoplanetary disc. Dust traps are observed as ring-like structures by ALMA suggesting the existence of global pressure maxima in discs that can also act as planet migration traps. This work aims to reveal how large a planetary core can grow in such a pressure maximum by pebble accretion. In our hydrodynamic simulations, pebbles are treated as a pressureless fluid mutually coupled to the gas via drag force. Our results show that in a global pressure maximum the pebble isolation mass for a planetary core is significantly larger than in discs with power-law surface density profile. An increased isolation mass shortens the formation time of giant planets.