A Mixed Stirring Mechanism for Debris Discs with Giant and Dwarf Planetary Perturbations

TL;DR

This study combines the effects of dwarf planet self-stirring and giant planet perturbations in debris discs through extensive simulations, revealing that a mixed mechanism more effectively excites disc dynamics than individual processes.

Contribution

It introduces a comprehensive simulation approach combining both stirring mechanisms, demonstrating their joint impact on debris disc evolution over 1 Gyr.

Findings

Mixed stirring mechanisms are more effective than single mechanisms.

Disc eccentricity and inclination depend on giant planet and disc mass.

Efficient stirring occurs even with small disc masses.

Abstract

Debris discs consist of belts of bodies ranging in size from dust grains to planetesimals; these belts are visible markers of planetary systems around other stars that can reveal the influence of extrasolar planets through their shape and structure. Two key stirring mechanisms -- self-stirring by planetesimals and secular perturbation by an external giant planet -- have been identified to explain the dynamics of planetesimal belts; their relative importance has been studied independently, but are yet to be considered in combination. In this work we perform a suite of 286 N-body simulations exploring the evolution of debris discs over 1~Gyr, combining the gravitational perturbations of both dwarf planets embedded in the discs, and an interior giant planet. Our systems were somewhat modeled after the architecture of the outer Solar system: a Solar mass star, a single massive giant planet at 30~au ($M_{\rm GP} =$ 10 to 316~$\mathrm{M}_{\oplus}$), and a debris disc formed by 100 massive dwarf planets and 1000 massless particles ($M_{\rm DD} =$ 3.16 to 31.6~$\mathrm{M}_{\oplus}$). We present the evolution of both the disc and the giant planet after 1~Gyr. The time evolution of the average eccentricity and inclination of the disc is strongly dependent on the giant planet mass as well as on the remaining disc mass. We also found that efficient stirring is achieved even with small disc masses. In general, we find that a mixed mechanism is more efficient in the stirring of cold debris discs than either mechanism acting in isolation.