The<i>Spitzer Space Telescope</i>Extragalactic First Look Survey: 24 μm Data Reduction, Catalog, and Source Identification

We present the reduction of the 24µm data obtained during the first cosmological survey performed by the Spitzer Space Telescope (First Look Survey, FLS). Images of a region of sky at moderately high galactic latitude (l=88.3, b=+34.9) were obtained on 9-11 December 2003. The survey consists of a shallow observation of 2.5 o ×2 o centered at 17 h 18 m +59 o 30 ′ (main survey) and a deeper observation of 1 o ×0.5 o centered at 17 h 17 m +59 o 45 ′ (verification survey). Issues with the reduction of the 24µm MIPS data are discussed and solutions to attenuate instrumental effects are proposed and applied to the data. Approximately 17000 sources are extracted with a signalto-noise ratio (SNR) greater than five. The photometry of the point sources is evaluated through PSF fitting using an empirical PSF derived from the data. Aperture corrections and the absolute calibration have been checked using stars in the field. Astrometric and photometric errors depend on the SNR of the source varying between 0.35 – 1 arcsec and 5 % – 15%, respectively, for sources detected at 20 – 5 σ.The flux of the 123 extended sources have been estimated through aperture photometry. The extended sources cover less than 0.3 % of the total area of the survey. Based on simulations, the main and verification surveys are 50 % complete at 0.3 and 0.15 mJy, respectively.