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Published March 2009 | Published
Journal Article Open

Formation and evolution of planetary systems : properties of debris dust around solar-type stars


We present Spitzer photometric (IRAC and MIPS) and spectroscopic (IRS low resolution) observations for 314 stars in the Formation and Evolution of Planetary Systems 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-3 Gyr. We identify 46 sources that exhibit excess infrared emission above the stellar photosphere at 24 μm, and 21 sources with excesses at 70 μm. 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 24 μm 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 70 μm 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 70 μm 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 suggests that the typical inner-disk radius is ≳10 AU. Although the interpretation is not unique, the lack of excess emission shortward of 16 μm and the relatively flat distribution of the 24 μm excess for ages ≾300 Myr is consistent with steady-state collisional models.

Additional Information

© 2009 American Astronomical Society. Print publication: Issue 1 (2009 March) Received 2008 June 22, accepted for publication 2008 September 30; published 2009 March 5. J.M.C. thanks Dave Frayer and the Spitzer Science Center staff for patiently answering numerous questions regarding Spitzer data. We are grateful to the anonymous referee for their extensive comments on the paper. We would also like to thank all members of the FEPS team for their contributions over the years. This work is based on observations made with the Spitzer Space Telescope, which is operated by JPL/Caltech under a contract with NASA. The program made use of data and resources from the FEPS project, which receives support from NASA contracts 1224768, 1224634, and 1224566 administered through JPL. This research made use of the SIMBAD database, operated at CDS, Strasbourg, France, and data products from the 2MASS, which is a joint project of the U. Massachusetts and the Infrared Processing and Analysis Center/Caltech, funded by NASA and the NSF. S.W. was supported by the German Research Foundation (DFG) through the Emmy Noether grant WO 857/2. M.R.M. is grateful for support from the NASA Astrobiology Institute.

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