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O. P. Kuhn (JAC)
Rest-frame optical/UV continua of 20 high redshift (z>3), relatively faint (r ~19-21, L>~L*) radio-quiet quasars from the Palomar Transit Grism Survey (Schneider et al 1994, AJ, 107, 1245) are constructed from near-IR and optical photometry obtained at UKIRT and the JKT. An initial search for evolution in the central engine compared rest-frame optical/UV continua of z~.1 quasars with those of z>3 quasars selected to match in L/L*, and found no significant difference in their continuum shapes, which implied little or no evolution in the ratio \dot{m}/MBH (Kuhn et al. 2001, ApJS, 136, 225). These z>3 quasars were necessarily bright, some of the most luminous ones known. A new sample, consisting primarily of radio-selected quasars, extended the z>3 set to lower luminosities. The distribution of rest-frame optical continua for these spans a wider range but is slightly redder than that of the more luminous z>3 quasars. The 3 reddest continua, with optical spectral indices, \alpha < 1, can be attributed to a contribution from a non-thermal component and to dust along the line of sight. This latest study of radio-quiet z>3 quasars eliminates a possible non-thermal contribution, but should still allow a range of colors, since the original selection was from a grism survey. Initial results indicate a narrower distribution of continuum shapes than for the radio-loud quasars, and one more consistent with that for the bright z>3, as well as the low redshift, quasars. The differences between the faint radio-loud and radio-quiet quasars will be examined and future directions towards disentangling the effects on the continua of dust or a non-thermal component from those which reflect intrinsic changes in the central engine outlined.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.