THE POPULATION OF HIGH REDSHIFT AGNS IN THE CHANDRA COSMOS SURVEY

We present the high redshift (3 3. 81 sources are selected in the 0.5-2 keV band, 14 are selected in the 2-10 keV and 6 in the 0.5-10 keV bands. We sample the high luminosity (log L(2−10keV ) >44.15 erg s −1 ) space density up to z �5 and a fainter luminosity range (43.5 3. We find that the space density of high-luminosity AGNs declines exponentially at all the redshifts, confirming the trend observed for optically selected quasars. At lower luminosity, the measured space density is not conclusive, and a larger sample of faint sources is needed. Comparisons with optical luminosity functions and BH formation models are presented together with prospects for future surveys. Subject headings: Galaxies: active - evolution - surveys - X-rays: galaxies