Probing the Terrestrial Regions of Planetary Systems: Warm Debris Disks with Emission Features

TL;DR

This study analyzes Spitzer IRS spectra of 22 debris disks with 10 micron silicate features, revealing the presence of warm exozodiacal dust in terrestrial zones, which can inform about planetary system architectures and planet formation.

Contribution

It demonstrates that emission features in debris disks can be used to locate warm dust in terrestrial zones, providing a new method to study planetary system regions without direct planet detection.

Findings

Features indicate exozodiacal dust in terrestrial zones.

Older systems with features are only around A-type stars.

Features may signal terrestrial planet formation processes.

Abstract

Observations of debris disks allow for the study of planetary systems, even where planets have not been detected. However, debris disks are often only characterized by unresolved infrared excesses that resemble featureless blackbodies, and the location of the emitting dust is uncertain due to a degeneracy with the dust grain properties. Here we characterize the Spitzer IRS spectra of 22 debris disks exhibiting 10 micron silicate emission features. Such features arise from small warm dust grains, and their presence can significantly constrain the orbital location of the emitting debris. We find that these features can be explained by the presence of an additional dust component in the terrestrial zones of the planetary systems, i.e. an exozodiacal belt. Aside from possessing exozodiacal dust, these debris disks are not particularly unique; their minimum grain sizes are consistent with the blowout sizes of their systems, and their brightnesses are comparable to those of featureless warm debris disks. These disks are in systems with a range of ages, although the older systems with features are found only around A-type stars. The features in young systems may be signatures of terrestrial planet formation. Analyzing the spectra of unresolved debris disks with emission features may be one of the simplest and most accessible ways to study the terrestrial regions of planetary systems.