Spitzer Documentation & Tools
VLA Observations

VLA observations of the extragalactic Spitzer First Look Survey (FLS) region were taken during 2001 and 2002. The data represents 240 hours in B-array at 1.4 GHz.

The VLA image is a mosaic of 35 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 average rms noise is about 23 microJy/beam. The pixel size is 1.5 arcsec.

As recommended at the Community Workshop we have undertaken a radio survey with the VLA at 1.4 GHz to 5-sigma sensitivity of ~ 90 micro-Janskys. The survey covers approximately 6 square degrees on the First Look Survey field at J1718+5930. It is composed of 35 pointings, using the B-configuration. The 240 hours of data was taken in two parts. The first half was obtained in early 2001 and the second half was obtained in late 2002.

FLS Exgal Pointing Positions
Map of pointing positions. Click for larger version.

The image above represents the Mosaic with the hundred brightest extracted radio components (with peak intensities ranging from 221 to 5.6 milliJy/beam) shown. The symbols are scaled by peak intensity.

Images and source lists can be retrieved from the InfraRed Sky Archive (IRSA) site.


The radio image and catalog include 3565 radio components brighter than 115 microJy/beam. For a detailed description of the FLS/VLA survey, see Condon, J.J., et al., 2003, AJ, 125, 2411. If you publish results based on the FLS/VLA survey, please reference this paper. 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.

We thank Jim Condon, W.D. Cotton, and Q.F. Yin (NRAO) and the NRAO staff who have carried out the VLA observations and radio data reduction. The National Radio Astronomy Observatory (NRAO) is a facility operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation.