Faint Images of the Radio Sky at Twenty-Centimeters

Survey

The survey covered 10,575 square degrees, centered on the North and South Galactic poles, chosen to overlap with the Sloan Digital Sky Survey (SDSS) in five optical bands. Its resolution and sensitivity were comparable to the Palomar Observatory Sky Survey. Observations were made in the VLA's B configuration at 20 cm wavelength, with 5 arcsecond angular resolution. FIRST was proposed concurrently with the NRAO VLA Sky Survey; trial observations for both occurred in 1992.

Survey observations of the North Galactic pole began in 1993, with 144 hours of observing time in April and May for test observations and an initial 300-square-degree strip, yielding a catalogue of 28,000 sources. Observations continued until 2004. South Galactic pole observations were made in 2009 and 2011, the latter using the EVLA. Data were processed through an automated pipeline in the Astronomical Image Processing System.

Images and catalogues were released without a proprietary period. The first catalogue was published in 1997; the latest as of 2017 was published in December 2014, containing 946,432 sources. The catalogue includes over 70,000 cross-identifications with SDSS and the Two Micron All Sky Survey (2MASS). Sources are named following the convention "FIRST Jhhmmss.s+ddmmss", registered with the International Astronomical Union.

Science

The survey's resolution was chosen to enable identification of optical counterparts, resolve complex multi-component radio sources, and classify radio morphology such as Fanaroff-Riley types. It aimed to contribute to studies of quasars, active galaxies, galaxy evolution, galactic astronomy, large-scale structure, and dark matter. The survey paper has been referenced by over 1,600 scientific publications. Sources were cross-matched with the Palomar Sky Survey to create the FIRST Bright Quasar Survey (FBQS), yielding quasar candidates followed up with optical spectroscopy; the initial survey found 69 quasars, 51 newly identified.

Broad absorption line quasars and high-redshift quasars were discovered via cross-matching with SDSS. Variability was detected in over 1,600 sources, including stars, pulsars, galaxies, quasars, and unidentified sources. On large scales, the two-point correlation function between radio galaxies was observed.