Multiple Disk Gaps and Rings Generated by a Single Super-Earth

Abstract

We investigate the observational signatures of super-Earths (i.e., planets withEarth-to-Neptunemass), which are the most common type of exoplanet discovered to date, in their natal disks of gas and dust. Combining two-fluid global hydrodynamics simulations with a radiative transfer code, we calculate the distributions of gas and of submillimeter-sized dust in a disk perturbed by a super-Earth, synthesizing images in near-infrared scattered light and the millimeter-wave thermal continuum for direct comparison with observations. In low-viscosity gas (  a -10 4 ), a super-Earth opens two annular gaps to either side of its orbit by the action of Lindblad torques. This double gap and its associated gas pressure gradients cause dust particles to be dragged by gas into three rings: one ring sandwiched between the two gaps, and two rings located at the gap edges farthest from the planet. Depending on thesystem parameters, additional rings may manifest for a single planet. A double gap located at tens of aufrom a host star in Taurus can be detected in the dust continuum by the Atacama Large Millimeter Array (ALMA) at an angular resolution of ∼  0. 03 after two hours of integration. Ring and gap features persist in a variety of background disk profiles, last for thousands of orbits, and change their relative positions and dimensions depending on the speed and direction of planet migration. Candidate double gaps have been observed by ALMA in systems such asHL Tau (D5 and D6) and TW Hya (at 37 and 43 au); we submit that each double gap is carved by one super-Earth in nearly inviscid gas.

A Thermodynamic View of Dusty Protoplanetary Disks

“…We will apply this modified codedPLUTO-to study dusty disk-planet interaction (J.-W. Chen & M.-K. Lin, in preparation). Preliminary results show that our approach reproduces features such as dusty rings associated with planet-induced gaps similar to those obtained from explicit two-fluid simulations (e.g., Dong et al 2017). …”

Spiral Arms in Disks: Planets or Gravitational Instability?

“…More graphically, high-resolution submillimeter continuum images of disks made with ALMA commonly show stunning rings and gaps (ALMA Partnership et al 2015;Andrews et al 2016;Cieza et al 2016Cieza et al , 2017Isella et al 2016;Loomis et al 2017;Dipierro et al 2018;Fedele et al 2018;Huang et al 2018), structures that signal that disk solids have grown beyond centimeter sizes and possibly into planetary-mass objects (e.g., Dipierro et al 2015;Dong et al 2015cDong et al , 2017a). These results exclaim that disks are highly evolved and call into question disk mass estimates made under the usual assumption of simple, unevolved, optically thin disks.…”

Protoplanetary Disks in ρ Ophiuchus as Seen from ALMA

“…The exact details of the gap-opening, including the gap structure's dependence on planetary embryo mass and surrounding disk structure, have not been fully analytically described (Crida et al 2006). In fact, it is uncertain whether a single planet per gap is required for gap formation or if a single planet can carve multiple gaps (Dong et al 2017). It is, however, generally agreed that higher embryo masses carve more substantial gaps.…”