Which planets trigger longer-lived vortices: low-mass or high-mass?

Abstract

Recent ALMA observations have found many protoplanetary discs with rings that can be explained by gap-opening planets less massive than Jupiter. Meanwhile, recent studies have suggested that protoplanetary discs should have low levels of turbulence. Past computational work on low-viscosity discs has hinted that these two developments might not be self-consistent because even low-mass planets can be accompanied by vortices instead of conventional double rings. We investigate this potential discrepancy by conducting hydrodynamic simulations of growing planetary cores in discs with various aspect ratios (H/r = 0.04, 0.06, 0.08) and viscosities (1.5 × 10 −5 α 3 × 10 −4 ), having these cores accrete their gas mass directly from the disc. With α < 10 −4 , we find that sub-Saturn-mass planets in discs with H/r 0.06 are more likely to be accompanied by dust asymmetries compared to Jupiter-mass planets because they can trigger several generations of vortices in succession. We also find that vortices with H/r = 0.08 survive > 6000 planet orbits regardless of the planet mass or disc mass because they are less affected by the planet's spiral waves. We connect our results to observations and find that the outward migration of vortices with H/r 0.08 may be able to explain the cavity in Oph IRS 48 or the two clumps in MWC 758. Lastly, we show that the lack of observed asymmetries in the disc population in Taurus is unexpected given the long asymmetry lifetimes in our low viscosity simulations (α ∼ 2 × 10 −5 ), a discrepancy we suggest is due to these discs having higher viscosities.

Wide Dust Gaps in Protoplanetary Disks Induced by Eccentric Planets: A Mass-Eccentricity Degeneracy

“…Duffell & Chiang 2015;Li et al 2019a), which disfavors the theoretical prediction on the excitation of Rossby Wave Instability (RWI) and the generation of vortices (Lovelace et al 1999;Li et al 2000Li et al , 2001Li et al , 2005Li et al , 2020. This effect would reconcile the tension between generally-inferred low viscosity in T Tauri disks and the lack of observed asymmetries (van der Marel et al 2021;Hammer et al 2021).…”

“…However, the vortices are smeared out in the eccentric cases, since an eccentric orbit not only quenches the accumulation of corotation materials (since L4 and L5 are no longer stationary points), but also prevents RWI by making gas gaps shallower and less steep. This is a potential solution to reconcile the general low viscosity in PPDs with the lack of observed symmetries in ALMA (Hammer et al 2021;van der Marel et al 2021;Michel et al 2021), although this issue is not the main focus of our paper.…”