Envelopes of embedded super-Earths I. Two-dimensional simulations

Abstract

Measurements of exoplanetary masses and radii have revealed a population of massive super-Earths --- planets sufficiently large that, according to one dimensional models, they should have turned into gas giants. To better understand the origin of these objects, we carry out hydrodynamical simulations of planetary cores embedded in a nascent protoplanetary disk. In this first paper of a series, to gain intuition as well as to develop useful diagnostics, we focus on two-dimensional simulations of the flow around protoplanetary cores. We use the pluto code to study isothermal and adiabatic envelopes around cores of sub- to super-thermal masses, fully resolving the envelope properties down to the core surface. Owing to the conservation of vortensity, envelopes acquire a substantial degree of rotational support when the core mass increases beyond the thermal mass, suggesting a limited applicability of one-dimensional models for describing the envelope structure. The finite size of the core (relatively large for super-Earths) also controls the amount of rotational support in the entire envelope. Steady non-axisymmetric shocks develop in the supersonic envelopes of high-mass cores, triggering mass accretion and turbulent mixing in their interiors. We also examine the influence of the gas self-gravity on the envelope structure. Although it only weakly alters the properties of the envelopes, the gas gravity has significant effect on the properties of the density waves triggered by the core in the protoplanetary disk.

17 pages, 24 figures; accepted for publication in MNRAS Published by Oxford University Press

References in corpus (8)

• PLUTO: a Numerical Code for Computational Astrophysics
• Most 1.6 Earth-Radius Planets are not Rocky
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• Hydrodynamics of Embedded Planets' First Atmospheres. II. A Rapid Recycling of Atmospheric Gas
• On corotation torques, horseshoe drag and the possibility of sustained stalled or outward protoplanetary migration
• Treating gravity in thin disk simulations
• Hydrodynamics of Embedded Planets' First Atmospheres. I. A Centrifugal Growth Barrier for 2D Flows
• Tidal Heating of Young Super-Earth Atmospheres

Cited by in corpus (5)

• The effects of disk self-gravity and radiative cooling on the formation of gaps and spirals by young planets
• Envelopes of embedded super-Earths II. Three-dimensional isothermal simulations
• Self-gravitating planetary envelopes and the core-nucleated instability
• The Critical Core Mass of Rotating Planets
• Effects of Self-gravity on Mass-loss of the Post-impact Super-Earths