Formation and Evolution of Planetary Systems (FEPS): Properties of Debris Dust around Solar-type Stars

TL;DR

This study uses Spitzer observations to analyze the properties and evolution of circumstellar dust around solar-type stars from 3 million to 3 billion years old, revealing how debris disks change over time.

Contribution

It provides a comprehensive dataset on infrared excesses and debris disk characteristics around solar-type stars, highlighting their evolution and properties over a wide age range.

Findings

15% of young stars (<300 Myr) show significant 24um excess emission.

The fraction of stars with debris disks declines to 2.7% with age.

Debris temperatures range from 60 to 180 K, with no strong age correlation.

Abstract

We present Spitzer photometric (IRAC and MIPS) and spectroscopic (IRS low resolution) observations for 314 stars in the Formation and Evolution of Planetary Systems (FEPS) Legacy program. These data are used to investigate the properties and evolution of circumstellar dust around solar-type stars spanning ages from approximately 3 Myr to 3 Gyr. We identify 46 sources that exhibit excess infrared emission above the stellar photosphere at 24um, and 21 sources with excesses at 70um. Five sources with an infrared excess have characteristics of optically thick primordial disks, while the remaining sources have properties akin to debris systems. The fraction of systems exhibiting a 24um excess greater than 10.2% above the photosphere is 15% for ages < 300 Myr and declines to 2.7% for older ages. The upper envelope to the 70um fractional luminosity appears to decline over a similar age range. The characteristic temperature of the debris inferred from the IRS spectra range between 60 and 180 K, with evidence for the presence of cooler dust to account for the strength of the 70um excess emission. No strong correlation is found between dust temperature and stellar age. Comparison of the observational data with disk models containing a power-law distribution of silicate grains suggest that the typical inner disk radius is > 10 AU. Although the interpretation is not unique, the lack of excess emission shortwards of 16um and the relatively flat distribution of the 24um excess for ages <300~Myr is consistent with steady-state collisional models.