How the planetary eccentricity influences the pebble isolation mass

Abstract

ABSTRACT We investigate the pebble isolation mass (PIM) for a planet on a fixed eccentric orbit in its protoplanetary disc by conducting a set of two-dimensional (2D) hydrodynamical simulations, including dust turbulent diffusion. A range of planet eccentricities up to e = 0.2 is adopted. Our simulations also cover a range of α-turbulent viscosities, and for each pair {α, e} the PIM is estimated as the minimum planet mass in our simulations such that solids with a Stokes number ≳0.05 do not flow across the planet orbit and remain trapped around a pressure bump outside the planet gap. For α < 10−3, we find that eccentric planets reach a well-defined PIM, which can be smaller than for planets on circular orbits when the eccentricity remains smaller than the disc’s aspect ratio. We provide a fitting formula for how the PIM depends on the planet's eccentricity. However, for α > 10−3, eccentric planets cannot fully stall the pebbles flow and, thus, do not reach a well-defined PIM. Our results suggest that the maximum mass reached by rocky cores should exhibit a dichotomy depending on the disc's turbulent viscosity. While being limited to ${\cal O}(10\, M_\oplus)$ in low-viscosity discs, this maximum mass could reach much larger values in discs with a high turbulent viscosity in the planet vicinity. Our results further highlight that pebble filtering by growing planets might not be as effective as previously thought, especially in high-viscosity discs, with important implications to protoplanetary discs observations.