Agns and Clusters in Chandra Deep Fields P. Tozzi and the Cdfs Team

The Chandra X–ray Satellite already observed several deep fields, including the two 1 Megasec exposures of the Chandra Deep Field South (CDFS) and North. We review here the main findings from the CDFS. The LogN–LogS relations show the resolution of the X–ray background into point sources at the level of 83–99% in the 1–2 keV band and 65–98% in the 2–10 keV band, given the uncertainties in the unresolved value. The so called “spectral paradox” is solved by a hard, faint population of sources constituted mostly by nearby (z ≤ 1) absorbed (Type II) AGNs with hard–band luminosities L ≃ 10 − 10 erg s. When comparing these results to other deep fields in the X–ray band, we find that the AGNs detected in 0.1 deg of the CDFS are representative of the AGNs population as a whole. However, we also noticed an excess in the hard counts in two Chandra deep fields. If we include this excess and average it among the observed fields, the total contribution of the XRB can grow of about 7%. Finally, we discuss briefly the properties of the Intra Cluster Medium imaged at high z, showing no evolution in clusters properties up to z ≃ 1.