Substructures in protoplanetary disks imprinted by compact planetary systems

Current ALMA observations have inferred the presence of Jovian-mass planets using substructures in protoplanetary disks. This mass range is limited in part by the current spatial resolution and the assumption that a density gap is opened by a single planet, although we expect that lower-mass planets would be far more abundant.

In this work, we study the detectable imprints of compact systems composed of Neptune-like planets and show that a prevalent and observable outcome is the formation of dust-trapping and long-lived vortices with a wide range of aspect ratios. Unlike in the single-planet case, these vortices lie inside the (common and shallower) density gap opened by the planets, allowing us to distinguish between a single Jovian from a pair of Neptunes, and suggest that the crescent-shaped structure around HD 163296 is caused by planets near the 3:2 commensurability.

Finally, we show that these prominent vortices between the planets are also expected for a pair of migrating planets with period ratios inside 3:2 (2:1) when the disk aspect ratio is above 0.035 (0.06) and discuss how they may affect the orbital evolution of the planets, including their likelihood to be trapped into mean-motion resonances.