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The scale invariance model [10] can be used to derive robust scaling relations between the radio luminosity from accreting black holes and the black hole mass and accretion rate. These relations agree well with the recently found “fundamental plane” of black hole activity [12]. Using these relations and the well known radio luminosity function, we derive estimates of the current and integrated power input by jets from growing black holes. Comparison with the estimated black hole mass density shows that the conversion efficiency from accreted rest mass to jet energy should be about 10% (with rather large uncertainties).

Results of a / survey for resolved high frequency emission from radio bright AGN jets are summarized. The multifrequency mapping and modelling indicates that powerful jets generally remain relativistic up to very large scales (10 cm). The X-ray to radio flux ratios of emission “knots” along the large scale jets are found to decrease systematically, which can be interpreted as moderate deceleration of the bulk flow near the jet end. In two cases the physical parameters and kinetic power at large scales can be compared with those deduced in a consistent way for the blazar emission region (10 cm) suggesting that the propagation is essentially free with little power dissipation between the two scales. Finally, connecting the jet properties with those of the presumed associated accretion disk (10 cm) a unified scenario is suggested whereby the most powerful jets are produced by rapidly spinning black holes with bright, near Eddington accretion disks. Significantly lower accretion rates (in Eddington units) lead to jets of lower absolute power and very underluminous disks (as predicted in ADAF–like models) thus with a higher ratio of jet to disk luminosity.

We discuss the role of feedback via photoionization and Compton heating in the co-evolution of massive black holes at the center of spheroidal galaxies and their stellar and gaseous components. We first assess the energetics of the radiative feedback from a typical quasar on the ambient interstellar gas. We then demonstrate that the observed H– relation could be established at a relatively early epoch in galactic evolution when the formation of the stellar bulge was almost completed and the gas-to-stars mass ratio was reduced to a low level ~0.01 such that cooling could not keep up with radiative heating. A considerable amount of gas was expelled at that time and black hole accretion proceeded at a much lower rate thereafter.

Several observational pieces of evidence and theoretical arguments suggest that feedback from accreting black holes is an unavoidable ingredient in the formation of galaxies. Many of these arguments are very well addressed in this volume; here I only mention the recent result of a dearth of low-luminosity AGN in the GOODS deep fields [1]. Taken together with other datasets, like the recent COMBO17 [3] and SDSS [4] surveys, this result allows to reconstruct the AGN luminosity function at ~4 from =–21 to –28. This is roughly fit by a simple (negative) density evolution of the =3 luminosity function [2]. This fact highlights the apparently “anti-hierarchical” behaviour of AGN (see also A. Merloni, these proceedings), in the sense that the peak of bright quasars aniticipates that of fainter objects, at variance with what is expected if AGN simply followed the assembly of dark matter halos.

We explore the possibility that the K line from the thermal matter may appear at tens of keV due to a high Doppler blue-shift. In the jet comoving frame, the energy density of photons originally emitted by the accretion disk and reflected off the broad line region clouds dominates over that of photons of other origin. We discuss the photoionization states of the thermal matter and find that the irons elements are neutral. The high metallicity in quasars enhances the possibility to detect the thermal matter in the relativistic jet in some radio-loud quasars. A highly Doppler blue-shifted K line may be detected. We make a prediction for 3C 273, in which the K line luminosity might be of the order 3.0× 10erg s with an equivalent width of 2.4 keV. Such a line could be detected in a future mission.

We use medium resolution optical spectra of 3CR radio galaxies to estimate their black hole masses and accretion rates. Black hole masses are found from central stellar velocity dispersions, and accretion rates are derived from narrow emission-line luminosities. The sample covers both Fanaroff-Riley (FR) classes; the more powerful FRIIs and the less powerful FRIs. We find that FRIs and FRIIs separate in diagrams of radio luminosity and narrow-line luminosity versus black hole mass. This suggests that, at a given black hole mass, the FRIIs accrete more efficiently, or accrete more matter, than FRIs.

The X-ray Background has been resolved in the 0.5– band and found to consist mostly of both unabsorbed and absorbed AGN with column densities . This contrasts with the local AGN population where the column density range extends to Compton-thick objects and beyond (). Stacking analysis of the integrated emission of sources detected by XMM-Newton in the Lockman Hole, and by Chandra in the CDF-N and S reveals that the resolved fraction of the X-ray Background drops above and is about 50% above . The missing flux has the spectrum of highly absorbed AGN, making it likely that the range of column density at redshift one is similar to that locally, and that many AGN are as yet undetected in well-studied fields.

Merging the and deep surveys with the previously identified surveys a unique sample of almost 1000 AGN–1 covering five orders of magnitude in 0.5–2 keV flux limit and six orders of magnitude in survey solid angle with ~95% completeness has been constructed. The luminosity–redshift diagram is almost homogeneously filled. AGN–1 are by far the largest contributors to the soft X–ray selected samples. Their evolution is responsible for the break in the total 0.5–2 keV source counts. The soft X–ray AGN–1 luminosity function shows a clear change of shape as a function of redshift, confirming earlier reports of luminosity–dependent density evolution for optical quasars and X–ray AGN. The space density evolution with redshift changes significantly for different luminosity classes, showing a strong positive evolution, i.e. a density increase at low redshifts up to a certain redshift and then a flattening. The redshift, at which the evolution peaks, changes considerably with X–ray luminosity, from ≈0.5–0.7 for luminosities log =42–43 erg s to ≈2 for log =45–46 erg s. The amount of density evolution from redshift zero to the maximum space density also depends strongly on X–ray luminosity, more than a factor of 100 at high luminosities, but less than a factor of 10 for low X–ray luminosities. For the first time, a significant decline of the space density of X–ray selected AGN towards high redshift has been detected in the range log =42–45 erg s, while at higher luminosities the survey volume at high–redshift is still too small to obtain meaningful densities. A comparison between X–ray and optical properties shows now significant evolution of the X–ray to optical spectral index for AGN–1. The constraints from the AGN luminosity function and evolution in comparison with the mass function of massive dark remnants in local galaxies indicates, that the average supermassive black hole has built up its mass through efficient accretion (~10%) and is likely rapidly spinning.

We analysed the optical and infrared properties of X-ray sources in the Great Observatories Origins Deep Survey (GOODS), a deep, multiwavelength survey covering 0.1 square degrees in two fields. The HST ACS data are well explained by a unified AGN scheme that postulates roughly 3 times as many obscured as unobscured AGN, as are the spectroscopic and photometric redshift distributions once selection effects are considered. Our model predicts infrared number counts of AGN that agree well with the preliminary Spitzer data, confirming that large numbers of obscured AGN are present in the early Universe (>1).

A significant fraction of the accreting black holes powering high redshift AGN are obscured by large columns of dust and gas. For this reason, luminous type 2 quasars can be efficiently discovered combining hard X–ray and near–infrared observations. We will briefly discuss the most recent results.