Gaps in Protoplanetary Disks as Signatures of Planets: I. Methodology and Validation

TL;DR

This paper develops a methodology to identify and analyze gaps in protoplanetary disks caused by planets, using radiative transfer modeling to predict observable signatures that can help detect and estimate planet masses.

Contribution

It introduces a detailed modeling approach incorporating radiative transfer and multiple scattering to interpret observational signatures of planet-induced gaps in disks.

Findings

Gaps by 200 M_Earth planets cause temperature changes up to ±29%.

Gaps are resolvable at 0.01" resolution in Taurus.

Surface brightness can vary by up to an order of magnitude due to gaps.

Abstract

We examine the observational consequences of partial gaps being opened by planets in protoplanetary disks. We model the disk using a static alpha-disk model with detailed radiative transfer, parametrizing the shape and size of the partially cleared gaps based on the results of hydrodynamic simulations. Shadowing and illumination by stellar irradiation at the surface of the gap leads to increased contrast as the gap trough is deepened by shadowing and cooling and the far gap wall is puffed up by illumination and heating. In calculating observables, we find that multiple scattering is important and derive an approximation to include these effects. A gap produced by a 200 M_Earth (70 M_Earth) planet at 10 AU can lower/raise the midplane temperature of the disk by up to ~-25/+29% (~-11/+19%) by shadowing in the gap trough and illumination on the far shoulder of the gap. At the distance of Taurus, this gap would be resolvable with ~0.01" angular resolution. The gap contrast is most significant in scattered light and at thermal continuum wavelengths characteristic of the surface temperature, reducing or raising the surface brightness by up to order of magnitude. Since gaps sizes are correlated to planet mass, this is a promising way of finding and determining the masses of planets embedded in protoplanetary disks.