Recycling and Radiative Cooling in the Formation of super-Earth Envelopes

In the context of core accretion, some physical mechanism must be invoked to prevent super-Earths from undergoing runaway accretion and growing to a gas giant. Recently a hydrodynamic mechanism has been proposed where the background disk continually exchanges gas with the planetary envelope, preventing cooling and stalling atmospheric growth. We present the results of our 3D radiation-hydrodynamic simulations of super-Earth sized cores embedded in a natal protoplanetary disk. We find that gas is efficiently recycled on the scale of the planet’s Bondi radius but recover an interior region where recycling is orders of magnitude less effective. We also present the role of planet mass and opacity in setting this recycling efficiency. Ultimately we find that atmospheric recycling is most effective for planetary cores at ~1 au, largely owing to the high optical depth at that location. Finally, we discuss the implications this has for forming super-Earths and subtleties associated with interpreting these methods of simulation.