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We use the angular two-point correlation function to estimate the spatial correlation length of radio sources taken from the large-area 1.4 GHz NVSS radio survey. At the median survey redshift of z ∼ 1, r[sub 0] is found to be increasing with flux density. This is consistent with a scenario in which powerful (i.e. FRII) radio galaxies probe significantly more massive spatial structures than less powerful radio galaxies. The large spatial correlation length that we derive for FRIIs is remarkably close to that of extremely red objects (EROs). This implies that powerful radio galaxies and EROs trace equally massive structures at z ∼ 1. Moreover, because powerful radio galaxies and EROs are both associated with luminous early-type galaxies we propose that they could be the same objects seen at different evolutionary stages. The correlation length of massive, luminous galaxies at z ∼ 1 is comparable to that of bright ellipticals locally, suggesting that r[sub 0] (comoving) of these massive galaxies has changed little from z ∼ 1 to z ≈ 0. This is in excellent agreement with current ACDM hierarchical model predictions. [ABSTRACT FROM AUTHOR]

We summarize the results of Spitzer IRAC and MIPS observations of 62 brightest cluster galaxies (BCGs) with optical line emission located in the cores of X-ray luminous clusters. We find that at least half of these sources have signs of excess infrared emission. The strength of the mid-IR excess emission correlates with the luminosity of the optical emission lines. Excluding several systems dominated by an AGN, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely powered by star formation. The IR luminosity (and thus star formation) is higher in BCGs with shorter cooling times in the central hot ICM suggesting that the gas which cools from the ICM ultimately forms stars. We find a correlation between mass deposition rates estimated from the X-ray emission and the star formation rate estimated from the infrared luminosity. The star formation rates are 1/10 to 1/100 of the mass deposition rates suggesting that the re-heating of the ICM is generally very effective in reducing the amount of mass cooling from the hot phase but does not eliminate it completely. [ABSTRACT FROM AUTHOR]

Galaxies form out of small fluctuations in a smoothly expanding Universe. However, the initial gravitational collapse phase is accompanied by the formation of supermassive black holes and clusters of massive stars. Black holes and star clusters generate powerful outflows in the form of jets and superwinds that interact with still infalling gas, possibly regulating the galaxy formation process, initiating new sites of star formation, and carrying chemically enriched gas to the intergalactic medium. Unfortunately, beyond this qualitative description our detailed theoretical understanding is poor. New results from 3D simulations of a GPS/CSS galaxy, with gravitational potentials included, shed some new light on the jet driven outflow process in particular. New code capabilites to predict detailed X-ray spectra, from multi-dimensional time-dependent dynamics simulations of Galaxy Feedback, and will be useful for future interpretation of X-ray and radio SEDs of forming galaxies. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Two 200-ks XMM Deep Field observations are planned to probe the faint-source populations that make up the hard X-ray background (2-10 keV). We use a simulated 200-ks XMM EPICPN Deep Field image, as well as simulated EPIC-PN spectra of potential types of faint-source populations, in order to explore the sensitivity of XMM for resolving the contributors to the hard X-ray background. [ABSTRACT FROM AUTHOR]

We discuss the effects of a comptonizing corona on the appearance of the reflection components, and in particular of the reflection hump, in the X-rays spectra of accreting black holes. Indeed, in the framework of a thermal corona model, we expect that part of (or even all, depending on the corona covering factor) the reflection features should cross the hot plasma, and thus suffer Compton scattering, before being observed. We have studied in detail the dependence of these effects on the physical (i.e. the temperature and optical depth) and geometrical (i.e. the inclination angle) parameters of the corona, concentrating on the slab geometry. Due to the smoothing and shifting towards high energies of the comptonized reflection hump, the main effects on the emerging spectra appear mainly above 100 keV. We have also investigated the importance of such effects on the interpretation of the results obtained with the standard fitting procedures. We found that fitting Comptonization models, taking into account comptonized reflection, by the usual cut-off power law + uncomptonized reflection model, may lead to an underestimation of the reflection normalization and an overestimation of the high energy cut-off. We discuss and illustrate the importance of these effects by analyzing recent observational results as those of the galaxy NGC 4258. We also find that the comptonizing corona can produce and/or emphasize correlations between the reflection features characteristics (like the iron line equivalent width or the covering fraction) and the X-ray spectral index similar to those recently reported in the literature. We also underline the importance of these effects when dealing with accurate spectral fitting of the X-ray background. [ABSTRACT FROM AUTHOR]