Debris rings from extrasolar irregular satellites

Abstract

ABSTRACT Irregular satellites are the minor bodies found orbiting all four Solar system giant planets, with large semimajor axes, eccentricities, and inclinations. Previous studies have determined that the Solar system’s irregular satellites are extremely collisionally evolved populations today, having lost ∼99 per cent of their initial mass over the course of hundreds of Myr. Such an evolution implies that the irregular satellites must have produced a population of dusty collisional debris in the past, which is potentially observable due to the resulting reprocessing of stellar light. In this paper, we examine the signatures of the debris discs produced by extrasolar analogues of this process. Radiation pressure, quantified by the parameter β, is the driving force behind the liberation of dust grains from the planetary Hill sphere, and results in the formation of circumstellar dust rings, even in the absence of an underlying belt of asteroids in the system. Our simulated discs reproduce many of the same features seen in some classes of observed debris discs, such as thin ring morphology, a large blowout size, and azimuthal symmetry. We compare our simulated discs’ radial profiles to those of the narrow dust rings observed around Fomalhaut and HR 4796A, and show that they can broadly reproduce the observed radial distribution of dust.