FIRST Science: What Are a Million Radio Sources Good For?
Session 38 -- Digitizing the Sky Part II
Oral presentation, Tuesday, 31, 1994, 2:00-5:30

## [38.07] FIRST Science: What Are a Million Radio Sources Good For?

D.J. Helfand (Columbia U.), R.H. Becker and M.D. Gregg (UC Davis and IGPP), R.L. White (STScI), R.G. McMahon (Cambridge)

The FIRST VLA 20~cm sky survey will produce a catalog of over $10^6$ radio sources down to flux densities of 750 microJanskys and with positions accurate to $\la 1^{\prime\prime}$. Data reduction for the initial 350 deg$^2$ strip passing through the North Galactic Pole is nearing completion, and by the time of the meeting, observing will have begun on the $\sim 1200$ deg$^2$ installment for 1994. We provide here a brief overview of the scientific utility of the FIRST catalog and images, using as an illustration data from the initial survey area. We discuss the optically identifiable fraction at various optical thresholds, demonstrating that unambiguous identifications are derivable for $\sim 12\%$, $\sim 20\%$, and $\ga 50\%$ of the cataloged radio sources at the POSS~I ($m_b\sim 20$), POSS~II ($m_b\sim 21$) and SDSS ($m_b\sim 24$) plate limits, respectively. Comparisons of the radio catalog of the NGP with the APS and APM plate scan catalogs allows us to assess the relative astrometric and source classifcation accuracy of these databases and to compile candidate lists of radio galaxies, moderate-redshift quasars, $z>4$ quasars, and starburst galaxies. We will report on a program of optical spectroscopic followup of these candidates scheduled for mid-May. Use of the images to obtain flux densities and upper limits for the IRAS FSC galaxies and GSC stars will be illustrated. An outline of major projects made possible by the FIRST database such as a definitive determination of the quasar radio luminosity function and an exploration of the evolution of large-scale structure using starburst galaxies will be presented.