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B. Kelly, J. Bechtold (Steward Obs.), A. Siemiginowska, M. Elvis, T. Aldcroft, M. Sobolewska (SAO, CFA)
The existing sample of quasars with X-ray data suffers from selection such that luminosity is artificially correlated with redshift. In our Chandra+XMM survey of radio-quiet z \ge 4 quasars, we found \alphaox and \Gammaox are strong functions of redshift but also weak function of luminosity, whereas other studies suggest that these X-ray parameters depend most strongly on L. So far, only the brightest z > 4 quasars have been targeted with Chandra, so that exposure times would be short (5 ksec); this strategy only strengthens the L-z correlation in the available X-ray sample. To remedy this situation, we observed 7 faint, radio-quiet quasars at z ~4. We investigate how blackhole mass and accretion rate depend on L and z, using new models for accretion disks with hot coronae.
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.