The VLA Low-frequency Sky Survey

TL;DR

The VLSS provides a comprehensive low-frequency sky map at 74 MHz, cataloging nearly 70,000 sources with high resolution and sensitivity, enabling new insights into the radio universe.

Contribution

This paper introduces the VLSS, a large-scale low-frequency sky survey at 74 MHz, with novel imaging algorithms to correct ionospheric distortions and a publicly available source catalog.

Findings

Imaged 95% of the northern sky at 74 MHz

Cataloged nearly 70,000 radio sources

Achieved a typical RMS noise level of 0.1 Jy/beam

Abstract

The Very Large Array (VLA) Low-frequency Sky Survey (VLSS) has imaged 95% of the 3*pi sr of sky north of declination = -30 degrees at a frequency of 74 MHz (4 meter wavelength). The resolution is 80" (FWHM) throughout, and the typical RMS noise level is ~0.1 Jy/beam. The typical point-source detection limit is 0.7 Jy/beam and so far nearly 70,000 sources have been catalogued. This survey used the 74 MHz 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 ~11.9 degree 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 online (http://lwa.nrl.navy.mil/VLSS) for use by the astronomical community.