A Spitzer IRS Study of Debris Disks Around Planet-Host Stars

TL;DR

This study uses Spitzer IRS data to analyze debris disks around 111 Sun-like stars, revealing 11 disks and providing insights into planet formation regions and the distribution of dust temperatures and orbital distances.

Contribution

First infrared spectrophotometry survey of debris disks around a large sample of planet-hosting stars, identifying new disks and constraining planet formation zones.

Findings

11 debris disks detected, including 2 new discoveries.

Most debris disks have temperatures between 60 and 100 K.

Debris rings orbit between 15 and 240 AU, indicating planet formation within 240 AU.

Abstract

Since giant planets scatter planetesimals within a few tidal radii of their orbits, the locations of existing planetesimal belts indicate regions where giant planet formation failed in bygone protostellar disks. Infrared observations of circumstellar dust produced by colliding planetesimals are therefore powerful probes of the formation histories of known planets. Here we present new Spitzer IRS spectrophotometry of 111 Solar-type stars, including 105 planet hosts. Our observations reveal 11 debris disks, including two previously undetected debris disks orbiting HD 108874 and HD 130322. Combining our 32 micron spectrophotometry with previously published MIPS photometry, we find that the majority of debris disks around planet hosts have temperatures in the range 60 < T < 100 K. Assuming a dust temperature T = 70 K, which is representative of the nine debris disks detected by both IRS and MIPS, we find that debris rings surrounding Sunlike stars orbit between 15 and 240 AU, depending on the mean particle size. Our observations imply that the planets detected by radial-velocity searches formed within 240 AU of their parent stars. If any of the debris disks studied here have mostly large, blackbody emitting grains, their companion giant planets must have formed in a narrow region between the ice line and 15 AU.