8th HEAD Meeting, 8-11 September, 2004
Session 26 AGN/Galactic Nuclei
Poster, Friday, September 10, 2004, 9:00am-10:00pm

## [26.18] Destroying Degeneracy: Chandra Observations of Faint Radio-Quiet Quasars at z=4

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.

Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.