Frequency of Debris Disks around Solar‐Type Stars: First Results from aSpitzerMIPS Survey

Abstract

We have searched for infrared excesses around a well-defined sample of 69 FGK main-sequence field stars. These stars were selected without regard to their age, metallicity, or any previous detection of IR excess; they have a median age of ~4 Gyr. We have detected 70 μm excesses around seven stars at the 3 σ confidence level. This extra emission is produced by cool material (L_dust/L ≥ 10^-3 are rare around old FGK stars, we find that the disk frequency increases from 2% ± 2% for L_dust/L ≥ 10^-4 to 12% ± 5% for L_dust/L ≥ 10^-5. This trend in the disk luminosity distribution is consistent with the estimated dust in our solar system being within an order of magnitude greater or less than the typical level around similar nearby stars. Although there is no correlation of IR excess with metallicity or spectral type, there is a weak correlation with stellar age, with stars younger than a gigayear more likely to have excess emission.