First Look Survey: NOAO R-band Mosaic

While both these fields were in early plans for the FLS, only a single deep-pointing test observation was made at the ELAIS-N1 location. The larger Legacy program SWIRE will include this region among its surveyed areas. The data products of our KPNO imaging (images and object catalogs) are made available to the community through the World Wide Web (via the Spitzer Science Center and NOAO Science Archive, ssc.spitzer.caltech.edu/fls/).

The overall quality of the images is high. The measured positions of sources detected in the images have rms uncertainties in their absolute positions on the order of 0.35" with possible systematic offsets on the order of 0.1", depending on the reference frame of comparison. The relative astrometric accuracy is much better than 1/10 of an arcsecond.

Typical delivered image quality in the images is 1.1" full width at half-maximum. The images are relatively deep, since they reach a median 5{sigma} depth limiting magnitude of R=25.5 (Vega) as measured within a 1.35 FWHM aperture, for which the signal-to-noise ratio (S/N) is maximal. Catalogs have been extracted with SExtractor, using thresholds in area and flux for which the number of false detections is below 1% at R=25.

Only sources with S/N>3 have been retained in the final catalogs. Comparing the galaxy number counts from our images with those of deeper R-band surveys, we estimate that our observations are 50% complete at R=24.5. These limits in depth are sufficient to identify a substantial fraction of the infrared sources that will be detected by Spitzer.

Use of the data: Use of these data must be accompanied by citation of the paper and acknowledgment: "The National Optical Astronomy Observatory (NOAO) is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation."