CONFIRMATION OF A CORRELATION BETWEEN THE X-RAY LUMINOSITY AND SPECTRAL SLOPE OF AGNs IN THE CHANDRA DEEP FIELDS.
Cristian Saez (PSU) , C. Saez (PSU), G. Chartas (PSU), W. N. Brandt (PSU), B. D. Lehmer (PSU), F. E. Bauer (Columbia), X. Dai (OSU), and G. P. Garmire (PSU).
We present results from a statistical analysis of 173 bright radio-quiet AGNs selected from the Chandra Deep Field-North and Chandra Deep Field-South surveys (hereafter, CDFs) in the redshift range of 0.1<z<4. We find that the X-ray power-law photon index of radio-quiet AGNs is correlated with their 2–10 keV rest-frame X-ray luminosity at the > 99.5 onfidence level in two redshift bins, 0.3<z<0.96, and 1.5<z<3.3 and slightly less significant in the redshift bin 0.96<z<1.5. The X-ray spectral slope steepens as the X-ray luminosity increases for AGNs in the luminosity range 10^42 to 10^45 erg s^-1. Combining our results from the CDFs with those from previous studies in the redshift range 1.5<z<3.3, we find that he Gamma−Lx correlation has a null-hypothesis probability of 1.6×10^-9. We investigate the redshift evolution of the correlation between the power-law photon index (Gamma) and the hard X-ray luminosity (LX) and find that the slope and offset of a linear fit to the correlation changes significantly (at the > 99.9 onfidence level) between redshift bins with 0.3<z<0.96 and 1.5<z <3.3. We explore possible physical scenarios explaining the origin of this correlation and its possible evolution with redshift in the context of steady corona models focusing on its dependency on variations of the properties of the hot corona with redshift.