AAS 195th Meeting, January 2000
Session 17. Quasars, QSO's and Their Environments
Display, Wednesday, January 12, 2000, 9:20am-6:30pm, Grand Hall

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[17.01] The FIRST Quasar Survey: Where's the Bimodality in Radio Loudness?

D.J. Helfand (Columbia U.), R.H. Becker (UC Davis and IGPP), M.D. Gregg, S. Laurent-Muehleisen, M. Brotherton (IGPP), R.L. White (STScI)

We have obtained optical spectra for more than 2000 counterparts to FIRST 20cm radio sources that are classified as stellar on the POSS I plates by the Cambridge Automated Plate Machine. Over 1000 quasars have been detected, the large majority for the first time. The primary purpose of the project is to obtain a new sample of optically bright quasars for a variety of projects (lens searches, absorption line studies, etc.). Optical counterpart magnitudes range down to R=19.0, although the majority of objects observed to date have R<17.8. The quasar surface density at the brightest magnitudes (R<16) is comparable to that found in optical surveys, despite the fact that we do not detect all known bright quasars in our survey region at the 1 mJy flux density threshold; thus, it is apparent we are detecting bright quasars missed in optically selected samples. We present the distribution of radio loudness for our survey (defined as a ratio of optical to radio luminosity) and find a result strikingly different from the bimodal distribution derived from radio observations of optically selected samples: the maximum of our distribution falls at the minimum of the bimodal distributions seen in previous studies, indicating that our sample is dominated by radio intermediate objects. We explore the implications of this result for the radio-loud/radio-quiet paradigm.

This work has received support from the NSF, the National Geographic Society, NASA, Sun Microsystems, IGPP, and Columbia University.

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