AAS Meeting #193 - Austin, Texas, January 1999
Session 40. Radio Source Surveys
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibits Hall 1

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[40.02] Optical Identification of 700 Radio Sources in Sixteen Square Degrees of the FIRST Survey

D.J. Helfand, I. A. Yadigaroglu, R. Berger (Columbia University), M. Postman, R.L. White (STScI), T. R. Lauer (NOAO), W. R. Oegerle (JHU), R.H. Becker (UC Davis and IGPP/LLNL)

We have used the deep I-band survey of Postman et al. to search for optical counterparts to radio sources from the VLA FIRST survey. A total of 1131 FIRST sources fall within the ~16 deg2 of the optical survey which extends to I~24. The optical astrometry has been calibrated using the FIRST (VLA B configuration) radio positions supplemented by a catalog of sources from A-configuration observations covering a portion of the field; after removal of optical reference frame distortions, CCD frame-to-frame shifts, and intraframe distortions, the absolute astrometric accuracy is better than ~0.3" throughout the survey region. We report here the identification of ~700 radio sources with flux densities ranging from 1 to 750 mJy; fewer than 30 of these sources have been previously identified. We discuss the detected fraction of radio sources as a function of optical magnitude, radio flux, and radio and optical morphology. Spectroscopic identifications have been obtained for a significant fraction of the stellar counterparts; most, as expected, are quasars. We also discuss the galaxy surface density in the vicinity of the radio sources, and comment on the utility of the radio survey in selecting high-redshift galaxy clusters and in exploring larger scale structures.

This work is supported at Columbia University by grants from NASA and the NSF.

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