The VLA Low-frequency Sky Survey

The VLA Low- frequency Sky Survey (VLSS) has imaged 95% of the 3 pi sr of sky north of delta=-30 degrees at a frequency of 74MHz ( 4 m wavelength). The resolution is 8000 ( FWHM) throughout, and the typical rms noise level is <sigma >approximate to 0: 1 Jy beam(1.) The typical point- source detection limit is 0.7 Jy beam(1,) and so far nearly 70,000 sources have been cataloged. This survey used the 74MHz system added to the VLA in 1998. It required new imaging algorithms to remove the large ionospheric distortions at this very low frequency throughout the entire similar to 11.9 degrees field of view. This paper describes the observation and data reduction methods used for the VLSS and presents the survey images and source catalog. All of the calibrated images and the source catalog are available from the VLSS Web site for use by the astronomical community.