AAS 201st Meeting, January, 2003
Session 114. Quasars
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[114.19] Probing the faint end of the z>3 quasar luminosity function

O. Kuhn (Joint Astronomy Centre, Hilo)

Rest-frame optical continua of 20 high redshift radio-loud quasars are constructed from near-IR data obtained at UKIRT. The sample consists of all z>3 quasars with radio detections that were listed in the NASA Extragalactic Database or the Véron-Cetty & Véron catalog (9th edition), with RA = 22h-08h30m and DEC = -20 - +60, and not noted as lensed. 16 of the 20 are radio-selected, while 4 were selected from grism or objective prism surveys. It expands on and extends to lower luminosity a previous z>3 sample used in a search for signs of evolution in quasar central engines (Kuhn et al. 2001, ApJS, 136, 225).

Single power law fits were made to the data: for the sample redshift range, z=3-4.1, the JHK photometry span rest wavelengths between 3125-5500Å(z=3) and 2450-4350Å(z=4.1). The distribution of optical spectral indices, \alpha, ranges from +0.4 to -1.7. As a whole it is slightly redder than that for the previously studied set of optically bright z>3 radio-quiet and radio-loud quasars, which does not extend below \alpha=-1. Of the 4 quasars with \alpha < -1, 2 are radio-selected and 2 are optically selected. The radio-selected ones have relatively high radio to optical flux ratios, RL>4, consistent with their having a beamed synchrotron component which may contribute to the red end of the optical continuum, while there is evidence that the 2 optically-selected quasars are reddened by dust. One of these, the reddest, has a particularly rich and interesting field for which optical photometry or optical/IR spectroscopy are needed to determine the redshift distribution.

The author(s) of this abstract have provided an email address for comments about the abstract: kuhn@jach.hawaii.edu

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