First Look Survey Ancillary VLA Data


VLA observations of the Spitzer Space Telescope FIRST Look Survey (FLS) were made during two successive B-configuration sessions, 2001 February through May and 2002 June through August. The dataset  represents about 240 hours in B-array at 1.4 GHz. The observations cover approximately 4.5 square degrees of the FLS field J1718+5930. 

The VLA image is a mosaic of thirty-five VLA pointings  . The image is fully calibrated and corrected for primary-beam attenuation and sky-curvature distortion. The 1.4 GHz data have been convolved with a Gaussian to yield a 5.0 arcsec FWHM circular beam. The rms noise at the center of most pointings is 21.5 microJy/beam; the average over the entire image is 23 microJy/beam. The image is about 7000x7000 pixels (including blanked regions), with a pixel size of 1.5 arcsec.

Work is still progressing on the source catalog, but there are about 3500 sources stronger than about 100 microJy. Most of the microJy radio sources are expected to be distant starburst galaxies, but there are a few prominent double-lobed radio sources visible in the field. The total radio source count density is about 800 per square deg, which corresponds to about one source per 35 Spitzer beam areas at 70 microns (close to the confusion limit) and one source per 6 Spitzer beam areas at 160 microns (well below the confusion limit). Assuming most sources are starburst systems that obey the FIR/radio correlation, this VLA image will contain many, if not the majority, of the sources that Spitzer will be able to detect at 70 and 160 micron bands.