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Session 43 - Source Surveys.
Display session, Wednesday, June 11
South Main Hall,

[43.04] From 4 pc to z=4: Optical Identification of FIRST Radio Sources

D. J. Helfand (Columbia U.), FIRST Team

Our VLA survey to create Faint Images of the Radio Sky at Twenty-cm has now covered 5000 deg^2 of the North Galacitic Cap and detected over 450,000 radio sources with subarcsecond positions down to the survey threshold of 1 mJy. An extensive program of optical followup observations has begun, and we report here on several of the interesting results obtained to date. Although fewer than 0.1% of the objects in the survey are expected to be associated with nearby stars, FIRST still represents by far the most sensitive unbiased survey for stellar radio emission ever undertaken. We have begun by examining all known stars within 25 pc of the Sun; seven are detected, several for the first time. Since proper motion uncertainties are the principal barrier to stellar identifications, the imminent release of the Hipparchos catalog will greatly expand the FIRST bright-star sample. There are, of course, thousands of faint stellar counterparts to FIRST sources, but the vast majority of these are quasars. The FIRST Bright Quasar Survey has provided spectroscopic followup for a sample of stellar radio counterparts complete over 2500 deg^2 to a POSS I E-magnitude of 17.5. Over 400 new quasars have been detected, including the FIRST radio-loud BAL objects and some remarkably luminous sources such as an E=16.5 qso at z=3.8. A status report on this survey will be presented. Finally, we have used followup optical and IR imaging as well as multislit spectroscopy of fields containing bent double radio sources to identify moderate to high-redshift clusters of galaxies. Keck observations of a sample of ten candidates show that at least eight contain clusters with redshifts ranging from 0.45 to 0.85. The results from recent 2 micron imaging of bent doubles in blank fields will also be presented. The FIRST project is supported by grants from the National Geographic Society, the National Science Foundation, NATO, IGPP, Columbia University, and Sun Microsystems.

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Program listing for Wednesday