Deep U- and G-band Imaging of the Spitzer Space Telescope First Look Survey Field: Observations and Source Catalogs

We present deep u-, and g-band images taken with the MegaCam on the 3.6 m Canada-France-Hawaii Telescope (CFHT) to support the extragalactic component of the Spitzer First Look Survey (hereafter, FLS). In this paper we outline the observations, present source catalogs and characterize the completeness, reliability, astrometric accuracy and number counts of this dataset. In the central 1 deg2 region of the FLS, we reach depths of g ∼26.5 mag, and u ∼26.2 mag (AB magnitude, 5σ detection over a 3 aperture) with ∼4 hours of exposure time for each filter. For the entire FLS region (∼5 deg2 coverage), we obtained u-band images to the shallower depth of u =25.0–25.4 mag (5σ, 3 aperture). The average seeing of the observations is 0.85 for the central field, and ∼1.00 for the other fields. Astrometric calibration of the fields yields an absolute astrometric accuracy of 0.15 when matched with the SDSS point sources between 18< g <22. Source catalogs have been created using SExtractor. The catalogs are 50% complete and greater than 99.3% reliable down to g ≃ 26.5 mag and u ≃ 26.2 mag for the central 1 deg2 field. In the shallower u-band images, the catalogs are 50% complete and 98.2% reliable down to 24.8–25.4 mag. These images and source catalogs will serve as a useful resource for studying the galaxy evolution using the FLS data. Subject headings: catalogs—surveys—galaxies:photometry