Dynamical friction with radiative feedback -- II. High resolution study of the subsonic regime

Abstract

Recent work has suggested that the net gravitational force acting on a massive and luminous perturber travelling through a gaseous and opaque medium can have same direction as the perturber's motion (an effect sometimes called negative dynamical friction). Analytic results were obtained using a linear analysis and were later confirmed by means of non-linear numerical simulations which did not resolve the flow within the Bondi sphere of the perturber, hence effectively restricted to weakly perturbed regions of the flow (paper~I). Here we present high resolution simulations, using either 3D Cartesian or 2D cylindrical meshes that resolve the flow within the Bondi sphere. We perform a systematic study of the force as a function of the perturber's mass and luminosity, in the subsonic regime. We find that perturbers with mass $M$ smaller than a few $M_c\sim \chi c_s/G$ are subjected to a thermal force with a magnitude in good agreement with linear theory ($\chi$ being the thermal diffusivity of the medium, $c_s$ the adiabatic sound speed and $G$ the gravitational constant), while for larger masses, the thermal forces are only a fraction of the linear estimate that decays as $M^{-1}$. Our analysis confirms the possibility of negative friction (hence a propulsion) on sufficiently luminous, low-mass embryos embedded in protoplanetary discs. Finally, we give an approximate expression of the total force at low Mach number, valid both for sub-critical ($M<M_c$) and super-critical ($M>M_c$) perturbers.

References in corpus (3)

• The structure of protoplanetary discs around evolving young stars
• Coorbital thermal torques on low-mass protoplanets
• Impact of thermal effects on the evolution of eccentricity and inclination of low-mass planets

Cited by in corpus (5)

• The importance of thermal torques on the migration of planets growing by pebble accretion
• Numerical study of coorbital thermal torques on cold or hot satellites
• On the interaction of pebble accreting embryos with the gaseous disc: importance of thermal forces
• Evolution of the eccentricity and inclination of low-mass planets subjected to thermal forces: a numerical study
• On the evolution of pebble-accreting planets in evolving protoplanetary discs