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We study the spatial clustering of 538 X-ray selected AGN in the 2?deg2XMM-COSMOS field that are spectroscopically identified with IAB<23 and span the redshift range z=0.2-3.0. The median redshift and X-ray luminosity of the sample are z = 0.98 and L0.5-10=6.3?1043?erg?s-1, respectively. A strong clustering signal is detected at ~18? level, which is the most significant measurement obtained to date for clustering of X-ray selected AGN. By fitting the projected correlation function w(rp) with a power law on scales of rp=0.3-40h-1?Mpc, we derive a best-fit comoving correlation length of r0= 8.6?0.5h-1?Mpc and slope of ?=1.88?0.07 (Poissonian errors; bootstrap errors are about a factor of?2?larger). An excess signal is observed in the range rp?5-15h-1?Mpc, which is due to a large-scale structure at z?0.36 containing about 40 AGN, a feature which is evident over many wavelengths in the COSMOS field. When removing the z?0.36 structure or computing w(rp) in a narrower range around the peak of the redshift distribution (e.g. z=0.4-1.6), the correlation length decreases to r0?5-6h-1?Mpc, which is consistent with what is observed for bright optical QSOs at the same redshift.?We investigate the clustering properties of obscured and unobscured AGN separately, adopting different definitions for the source obscuration. For the first time, we are able to provide a significant measurement for the spatial clustering of obscured AGN at z?1. Within the statistical uncertainties, we do not find evidence that AGN with broad optical lines (BLAGN) cluster differently from AGN without broad optical lines (non-BLAGN). Based on these results, which are limited by object statistics, however, obscured and unobscured AGN are consistent with inhabiting similar environments.?The evolution of AGN clustering with redshift is also investigated. No significant difference is found between the clustering properties of XMM-COSMOS AGN at redshifts below or above z=1.?The correlation length measured for XMM-COSMOS AGN at z?1 is similar to that of massive galaxies (stellar mass M*? 3?1010?M?) at the same redshift. This suggests that AGN at z?1 are preferentially hosted by massive galaxies, as observed both in the local and in the distant (z?2) Universe. According to a simple clustering evolution scenario, we find that the relics of AGN are expected to have a correlation length as large as r0?8h-1?Mpc by z=0, and hence to be hosted by local bright (L?L*) ellipticals.?We make use of dark matter halo catalogs from the Millennium simulation to determine the typical halo hosting moderately luminous z?1?AGN. We find that XMM-COSMOS AGN live in halos with masses M?2.5?1012M?h-1. By combining the number density of XMM-COSMOS AGN to that of the hosting dark matter halos we estimate the AGN duty cycle and lifetimes. We find lifetimes approximately of 1?Gyr for AGN at z?1, which are longer than those estimated for optically bright QSOs at the same redshift. These longer lifetimes mainly reflect the higher number density of AGN selected by X-ray samples.?

The rotational velocity of distant galaxies, when interpreted as a size (luminosity) indicator, may be used as a tool to select high redshift standard rods (candles) and probe world models and galaxy evolution via the classical angular diameter-redshift or Hubble diagram tests. We implement the proposed testing strategy using a sample of 30 rotators spanning the redshift range 0.2 < z < 1 with high resolution spectra and images obtained by the VIMOS/VLT Deep Redshift Survey (VVDS) and the Great Observatories Origins Deep Survey (GOODs). We show that by applying at the same time the angular diameter-redshift and Hubble diagrams to the same sample of objects (i.e. velocity selected galactic discs) one can derive a characteristic chart, the cosmology-evolution diagram, mapping the relation between global cosmological parameters and local structural parameters of discs such as size and luminosity. This chart allows to put constraints on cosmological parameters when general prior information about discs evolution is available. In particular, by assuming that equally rotating large discs cannot be less luminous at z = 1 than at present (M(z=1) ?M(0)), we find that a flat matter dominated cosmology (?m=1) is excluded at a confidence level of 2 ? and an open cosmology with low mass density (?m?0.3) and no dark energy contribution (??) is excluded at a confidence level greater than 1 ?. Inversely, by assuming prior knowledge about the cosmological model, the cosmology-evolution diagram can be used to gain useful insights about the redshift evolution of baryonic discs hosted in dark matter halos of nearly equal masses. In particular, in a ?CDM cosmology, we find evidence for a bimodal evolution where the low-mass discs have undergone significant surface brightness evolution over the last 8.5 Gyr, while more massive systems have not. We suggest that this dichotomy can be explained by the epochs at which these two different populations last assembled.??

Context. Studies of the infrared (IR) emission of cosmic sources have proven essential to constraining the evolutionary history of cosmic star formation and the gravitational accretion of nuclear black holes, because many of these events occur inside heavily dust-extinguished environments. Aims. The Spitzer Space Telescopehas provided a large amount of data to constrain the nature and cosmological evolution of infrared source populations. In the present paper we exploit a large homogeneous dataset to derive a self-consistent picture of IR emission based on the time-dependent $\lambda_{\rm eff}$= 24, 15, 12, and 8 μm monochromatic and bolometric IR luminosity functions (LF) over the full 0 1.5. Based on the multiwavelength information available in these areas, we constrain the LFs at 8, 12, 15, and 24 μm. We also infer the total IR luminosities from our best-fit model of the observed SEDs of each source, and use this to derive the bolometric (8–1000 μm) LF and comoving volume emissivity to z~ 2.5. Results. In the redshift interval 0 1. The mean redshift of the peak in the source number density shifts with luminosity: the brightest IR galaxies appear to form stars at earlier cosmic times (z>1.5), while star formation in the less luminous galaxies continues until more recent epochs (z~ 1 for LIR<1011$L_{\odot}$), in overall agreement with similar analyses in the literature. Conclusions. Our results are indicative of a rapid increase in the galaxy IR comoving volume emissivity up to z~ 1 and a constant average emissivity at z>1. We also appear to measure a difference in the evolutionary rate of the source number densities as a function of luminosity, which is consistent with the downsizingevolutionary patterns reported for other samples of cosmic sources.

Context. Studies of the infrared (IR) emission of cosmic sources have proven essential to constraining the evolutionary history of cosmic star formation and the gravitational accretion of nuclear black holes, because many of these events occur inside heavily dust-extinguished environments.