Characterizing the Variable Dust Permeability of Planet-induced Gaps

Abstract

Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can alter the dust dynamics significantly. In this paper, we carry out a systematic study employing long-term numerical simulations aimed at characterizing the critical particle-size for retention outside a gap as a function of particle size and for various key parameters defining the protoplanetary disk model. To this end, we perform multifluid hydrodynamical simulations in two dimensions, including different dust species, which we treat as pressureless fluids. We initialize the dust outside of the planet's orbit and study under which conditions dust grains are able to cross the gap carved by the planet. In agreement with previous work, we find that the permeability of the gap depends both on dust dynamical properties and the gas disk structure: while small dust follows the viscously accreting gas through the gap, dust grains approaching a critical size are progressively filtered out. Moreover, we introduce and compute a depletion factor that enables us to quantify the way in which higher viscosity, smaller planet mass, or a more massive disk can shift this critical size to larger values. Our results indicate that gap-opening planets may act to deplete the inner reaches of protoplanetary disks of large dust grains -potentially limiting the accretion of solids onto forming terrestrial planets.

The role of Bells in the continuous accretion between the CM and CR chondrite reservoirs

“…), dust filtration is found to be more efficient when the gap is deep and narrow, resulting in a higher pressure gradient at the outer edge of the gap (Weber et al. ). In general, the more massive a planet is, the smaller the particles that can reach the inner edge of the gap (Weber et al.…”

“…In general, the more massive a planet is, the smaller the particles that can reach the inner edge of the gap (Weber et al. ). Hence, a growing planet is expected to filter more particles over time, a trend opposite to expectations brought forward by our data.…”

“…Furthermore, this filter becomes more effective when the stellar accretion rate and surface density of the gas decrease during the aging of the disk (Weber et al. ). However, as we discuss below, the profile of a planetary gap can be affected in multiple ways to accommodate changes in dust filtration efficiency.…”

“…With increasing viscosity in the disk, more gas is able to refill the planet‐carved gap, and consequently, the steepness of the density profile becomes less pronounced, allowing for more efficient dust transitions (Weber et al. ). Similarly, it is found that high‐viscosity disks have a higher pebble isolation mass (PIM: the mass needed for a planet to exclude pebbles from the gap area, Ataiee et al.…”

Gas and multispecies dust dynamics in viscous protoplanetary discs: the importance of the dust back-reaction

“…In addition, our solutions make a number of symmetry assumptions (most notably azimuthal symmetry) and full 3D calculations will be required to understand the dynamics induced by the back-reaction. This however requires sophisticated gas and dust simulations, the tools for which have only recently begun to be developed (Gonzalez et al 2017;Ricci et al 2018;Humphries & Nayakshin 2018;Hutchison et al 2018;Weber et al 2018).…”