Density waves in protoplanetary discs excited by eccentric planets: linear theory

TL;DR

This paper develops a linear theoretical framework to accurately model spiral density waves in protoplanetary discs caused by eccentric planets, matching numerical simulations and capturing complex wave features.

Contribution

It introduces a versatile linear approach that accounts for azimuthal and temporal periodicities, extending the analysis to any periodic perturbing potential.

Findings

Excellent agreement with numerical simulations

Captures complex eccentric features like bifurcations and wave crossings

Improves accuracy over previous heuristic methods

Abstract

Spiral density waves observed in protoplanetary discs have often been used to infer the presence of embedded planets. This inference relies both on simulations as well as the linear theory of planet-disc interaction developed for planets on circular orbits to predict the morphology of the density wake. In this work we develop and implement a linear framework for calculating the structure of the density wave in a gaseous disc driven by an eccentric planet. Our approach takes into account both the essential azimuthal and temporal periodicities of the problem, allowing us to treat any periodic perturbing potential (i.e. not only that of an eccentric planet). We test our framework by calculating the morphology of the density waves excited by an eccentric, low-mass planet embedded in a globally isothermal disc and compare our results to the recent direct numerical simulations (and heuristic wavelet analysis) of the same problem by Zhu and Zhang. We find excellent agreement with the numerical simulations, capturing all the complex eccentric features including spiral bifurcations, wave crossings and planet-wave detachments, with improved accuracy and detail compared with the wavelet method. This illustrates the power of our linear framework in reproducing the morphology of complicated time-dependent density wakes, presenting it as a valuable tool for future studies of eccentric planet-disc interactions.