Kinematic signatures of a low-mass planet with a moderately inclined orbit in a protoplanetary disk

TL;DR

This study uses 3D hydrodynamic simulations to analyze how a low-mass, inclined-orbit planet influences gas kinematics in protoplanetary disks, revealing distinctive features that help identify planet properties.

Contribution

It demonstrates that inclined low-mass planets can produce observable kinematic signatures similar to massive coplanar planets, with unique dependencies on molecular isotopologues.

Findings

Inclined low-mass planets create prominent kinematic features.

Kinematic features are weaker in rarer CO isotopologues for inclined planets.

Observed kinks in HD 163296 can be explained by inclined and coplanar planets.

Abstract

A planet embedded in a protoplanetary disk produces a gap by disk-planet interaction. It also generates velocity perturbation of gas, which can also be observed as deviations from the Keplerian rotation in the channel map of molecular line emission, called kinematic planetary features. These observed signatures provide clues to determine the mass of the planet. We investigated the features induced by the planet with an inclined orbit through three-dimensional hydrodynamic simulations. We found that a smaller planet, with the inclination being $\sim 10^{\circ}$ -- $20^{\circ}$, can produce kinematic features as prominent as those induced by the massive coplanar planet. Despite the kinematic features being similar, the gap is shallower and narrower as compared with the case in which the kinematic features are formed by the coplanar planet. We also found that the kinematic features induced by the inclined planet were fainter for rarer CO isotopologues because the velocity perturbation is weaker at the position closer to the midplane, which was different in the case with a coplanar massive planet. This dependence on the isotopologues is distinguished if the planet has the inclined orbit. We discussed two observed kinematic features in the disk of HD 163296. We concluded that the kink observed at 220 au can be induced by the inclined planet, while the kink at 67 au is consistent to that induced by the coplanar planet.