Planet Shadows in Protoplanetary Disks. II: Observable Signatures

TL;DR

This study models observable signatures of small embedded planets in protoplanetary disks across various wavelengths, highlighting potential for future direct imaging with advanced telescopes.

Contribution

It provides simulated images of disk perturbations caused by 10-50 Earth-mass planets, analyzing their appearance in scattered light and thermal emission at different wavelengths.

Findings

Perturbations are most observable in visible to mid-infrared wavelengths.

Shadows and thermal features reveal planet-induced disk structures.

Longer wavelengths diminish perturbation visibility due to optical thinness.

Abstract

We calculate simulated images of disks perturbed by embedded small planets. These 10-50 M_Earth bodies represent the growing cores of giant planets. We examine scattered light and thermal emission from these disks over a range of wavelengths, taking into account the wavelength-dependent opacity of dust in the disk. We also examine the effect of inclination on the observed perturbations. We find that the perturbations are best observed in the visible to mid-infrared. Scattered light images reflect shadows produced at the surface of perturbed disks, while the infrared images follow thermal emission from the surface of the disk, showing cooled/heated material in the shadowed/brightened regions. At still longer wavelengths in the sub-millimeter, the perturbation fades as the disk becomes optically thin and surface features become overwhelmed by emission closer toward the midplane of the disk. With the construction of telescopes such as TMT, GMT and ALMA due in the next decade, there is a real possibility of observing planets forming in disks in the optical and sub-millimeter. However, having the angular resolution to observe the features in the mid-infrared will remain a challenge.