AAS 207th Meeting, 8-12 January 2006
Session 63 From Here to Eternity: The Spitzer Legacy Programs
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[63.42] Preliminary Results of the Spitzer SWIRE Brown Dwarf Survey

D. L. Padgett (Spitzer Science Center), C. Lonsdale (IPAC), K. R. Stapelfeldt (JPL), J. O'Linger-Luscusk (Spitzer Science Center), SWIRE Legacy Team

SWIRE (The Spitzer Wide-area Infrared Extragalactic survey) is a Spitzer Legacy project which has mapped nearly 50 square degrees in 5 optical (U, g, r, i, z - not yet complete) and 7 infrared bands (3.6, 4.5, 5.8, 8.0, 24, 70, and 160 microns). The survey observed low background sky to a depth of a few microJy at 3.6 and 4.5 microns. While this observing program was designed for extragalactic science, its phenominal depth at the T dwarf SED peak near 4.5 microns makes it ideal for discovering previously unknown field brown dwarfs. Using the current team source catalogs covering about 25 square degrees in three fields, we have identified about 100 sources which fulfill the [4.5] - [3.6] > 0.75 color criteria for brown dwarfs later than T5 (Patten et al. 2005) and are optically invisible down to mr = 26. Careful examination of individual sources to eliminate cosmic rays and extended sources reveal that about 10 are reliable, pointlike, and worthy of spectroscopic followup. Among the false alarms is a class of pointlike optically invisible, but mid-IR bright extragalactic sources which are excluded from the list of brown dwarf candidates by their brightness at 8 and 24 microns. By the time of the January meeting, we will report brown dwarf candidate statistics from nearly the entire SWIRE survey. Further sources may be identified in the already analyzed fields by searching for objects only detected at 4.5 microns.

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