The interplay between forming planets and photo-evaporating discs I: Forbidden line diagnostics

TL;DR

This study combines models of planet formation and disc photo-evaporation to analyze their interaction effects on observable wind diagnostics, revealing how giant planets influence disc winds and produce detectable spectral signatures.

Contribution

It presents the first 3D radiation-hydrodynamic simulations of giant planet hosting discs undergoing X-ray photo-evaporation, linking planetary gaps to observable wind features.

Findings

Giant planets carve gaps affecting wind structure and kinematics.

Synthetic line profiles show observable signatures of planetary influence.

Asymmetries and temporal variations in line profiles are induced by massive planets.

Abstract

Disc winds and planet formation are considered to be two of the most important mechanisms that drive the evolution and dispersal of protoplanetary discs and in turn define the environment in which planets form and evolve. While both have been studied extensively in the past, we combine them into one model by performing three-dimensional radiation-hydrodynamic simulations of giant planet hosting discs that are undergoing X-ray photo-evaporation, with the goal to analyse the interactions between both mechanisms. In order to study the effect on observational diagnostics, we produce synthetic observations of commonly used wind-tracing forbidden emission lines with detailed radiative transfer and photo-ionisation calculations. We find that a sufficiently massive giant planet carves a gap in the gas disc that is deep enough to affect the structure and kinematics of the pressure-driven photo-evaporative wind significantly. This effect can be strong enough to be visible in the synthetic high-resolution observations of some of our wind diagnostic lines, such as the [OI] 6300 \r{A} or [SII] 6730 \r{A} lines. When the disc is observed at inclinations around 40{\deg} and higher, the spectral line profiles may exhibit a peak in the redshifted part of the spectrum, which cannot easily be explained by simple wind models alone. Moreover, massive planets can induce asymmetric substructures within the disc and the photo-evaporative wind, giving rise to temporal variations of the line profiles that can be strong enough to be observable on timescales of less than a quarter of the planet's orbital period.