Debris Rings From Extrasolar Irregular Satellites

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% of their initial mass over the course of hundreds of Myr. In this paper, we show that circumstellar disks can result from the dust generated by these collisions. Radiation pressure, quantified by the parameter \(\beta\), is the driving force behind the liberation of dust grains from the planetary Hill sphere. Our simulated disks reproduce many of the same features seen in observed debris disks, such as thin ring morphology, a large blowout size, and azimuthal symmetry. By comparing the dust grain collisional timescale with the residence timescale as a function of size, we identify a critical intersection of (\(\beta \approx 0.1, t \approx 10\ years\)) that tells us the minimum size at which dust grains can exit the Hill sphere and how long it will take. Since a relation exists between \(\beta\), dust grain size, and observing wavelength, this also provides a future road map for observers. Due to how short the intersection timescale is, we do not expect to observe any long-lived circumplanetary "irregular satellite disks," since large dust grains will grind down to smaller dust grains, and small dust grains will quickly escape the Hill sphere. We compare our simulated disks' radial profiles to those of Fomalhaut and HR 4796A. We find that all three systems satisfy the definition of a narrow ring put forth by Hughes et al. (2018), \(\dfrac{\Delta R}{R} < 0.5\).