Aims. Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sources detected serendipitously in each field. This paper describes the creation and characteristics of the 2XMM catalogue. Methods. The 2XMM catalogue has been compiled from a new processing of the XMM-Newton EPIC camera data. The main features of the processing pipeline are described in detail. Results. The catalogue, the largest ever made at X-ray wavelengths, contains 246 897 detections drawn from 3491 public XMM-Newton observations over a 7-year interval, which relate to 191 870 unique sources. The catalogue fields cover a sky area of more than 500 deg 2 . The non-overlapping sky area is ∼360 deg 2 (∼1% of the sky) as many regions of the sky are observed more than once by XMM-Newton. The catalogue probes a large sky area at the flux limit where the bulk of the objects that contribute to the X-ray background lie and provides a major resource for generating large, well-defined X-ray selected source samples, studying the X-ray source population and identifying rare object types. The main characteristics of the catalogue are presented, including its photometric and astrometric properties

The COSMOS-Legacy survey is a 4.6 Ms Chandra program that has imaged 2.2 deg2 of the COSMOS field with an effective exposure of

Abstract. We report on the first deep X-ray survey with the XMM-Newton observatory during the performance verification phase. The field of the Lockman Hole, one of the best studied sky areas over a very wide range of wavelengths, has been observed. A total of ∼100 ksec good exposure time has been accumulated. Combining the images of the European Photon Imaging Camera (EPIC) detectors we reach a flux limit of 0.31, 1.4 and 2.4 10 −15 erg cm −2 s −1 , respectively in the 0.5-2, 2-10, and 5-10 keV band. Within an off-axis angle of 10 arcmin we detect 148, 112 and 61 sources, respectively. The log(N)-log(S) relation in the three bands is compared with previous results. In particular in the 5-10 keV band these observations present the deepest X-ray survey ever, about a factor 20 more sensitive than the previous BeppoSAX observations. Using X-ray spectral diagnostics and the set of previously known, spectroscopically identified ROSAT sources in the field, the new sources can be classified. XMM-Newton detects a significant number (∼40%) of X-ray sources with hard, probably intrinsically absorbed X-ray spectra, confirming a prediction of the population synthesis models for the X-ray background.

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.5 sq.deg of the COSMOS field (centered at 10 h , +02 o ) with an effective exposure of ∼160 ksec, and an outer 0.4 sq.deg. area with an effective exposure of ∼80 ksec. The limiting source detection depths are 1.9×10 −16 erg cm −2 s −1 in the Soft (0.5-2 keV) band, 7.3×10 −16 erg cm −2 s −1 in the Hard (2-10 keV) band, and 5.7×10 −16 erg cm −2 s −1 in the Full (0.5-10 keV) band. Here we describe the strategy, design and execution of the C-COSMOS survey, and present the catalog of 1761 point sources detected at a probability of being spurious of <2×10 −5 (1655 in the Full, 1340 in the Soft, and 1017 in the Hard bands). By using a grid of 36 heavily (∼50%) overlapping pointing positions with the ACIS-I imager, a remarkably uniform (±12%) exposure across the inner 0.5 sq.deg field was obtained, leading to a sharply defined lower flux limit. The widely different PSFs obtained in each exposure at each point in the field required a novel source detection method, because of the overlapping tiling strategy, which is described in a companion paper. This method produced reliable sources down to a 7-12 counts, as verified by the resulting logN-logS curve, with sub-arcsecond positions, enabling optical and infrared identifications of virtually all sources, as reported in a second companion paper. The full catalog is described here in detail and is available on-line.

Context. The COSMOS survey is a multiwavelength survey aimed to study the evolution of galaxies, AGN and large scale structures. Within this survey XMM-COSMOS a powerful tool to detect AGN and galaxy clusters. The XMM-COSMOS is a deep X-ray survey over the full 2 deg 2 of the COSMOS area. It consists of 55 XMM-Newton pointings for a total exposure of ∼1.5 Ms with an average vignetting-corrected depth of 40 ks across the field of view and a sky coverage of 2.13 deg 2 . Aims. We present the catalogue of point-like X-ray sources detected with the EPIC CCD cameras, the log N − log S relations and the X-ray colour-colour diagrams. Methods. The analysis was performed using the XMM-SAS data analysis package in the 0.5-2 keV, 2-10 keV and 5-10 keV energy bands. Source detection has been performed using a maximum likelihood technique especially designed for raster scan surveys. The completeness of the catalogue as well as log N − log S and source density maps have been calibrated using Monte Carlo simulations. Results. The catalogs contains a total of 1887 unique sources detected in at least one band with likelihood parameter det_ml > 10. The survey, which shows unprecedented homogeneity, has a flux limit of ∼1.7×10 −15 erg cm −2 s −1 , ∼9.3×10 −15 erg cm −2 s −1 and ∼1.3×10 −14 erg cm −2 s −1 over 90% of the area (1.92 deg 2 ) in the 0.5-2 keV, 2-10 keV and 5-10 keV energy band, respectively. Thanks to the rather homogeneous exposure over a large area, the derived log N − log S relations are very well determined over the flux range sampled by XMM-COSMOS. These relations have been compared with XRB synthesis models, which reproduce the observations with an agreement of ∼10% in the 5-10 keV and 2-10 keV band, while in the 0.5-2 keV band the agreement is of the order of ∼20%. The hard X-ray colors confirmed that the majority of the extragalactic sources in a bright subsample are actually type I or type II AGN. About 20% of the sources have a X-ray luminosity typical of AGN (L X > 10 42 erg/s) although they do not show any clear signature of nuclear activity in the optical spectrum.

A large population of heavily obscured, Compton-thick AGN is predicted by AGN synthesis models for the cosmic X-ray background and by the "relic" super-massive black-hole mass function measured from local bulges. However, even the deepest X-ray surveys are inefficient to search for these elusive AGN. Alternative selection criteria, combining mid-infrared with near-infrared and optical photometry, have instead been successful to pin-point a large population of Compton thick AGN. We take advantage of the deep Chandra and Spitzer coverage of a large area (more than 10 times the area covered by the Chandra deep fields, CDFs) in the COSMOS field, to extend the search of highly obscured, Compton-thick active nuclei to higher luminosity. These sources have low surface density and large samples can be provided only through large area surveys, like the COSMOS survey. We analyze the X-ray properties of COSMOS MIPS sources with 24µm fluxes higher than 550µJy. For the MIPS sources not directly detected in the Chandra images we produce stacked images in soft and hard X-rays bands. To estimate the fraction of Compton-thick AGN in the MIPS source population we compare the observed stacked count rates and hardness ratios to those predicted by detailed Monte Carlo simulations including both obscured AGN and star-forming galaxies. The volume density of Compton thick QSOs (logL(2-10keV)=44-45 ergs s −1 , or logλL λ (5.8µm)=44.79-46.18 ergs s −1 for a typical infrared to X-ray luminosity ratio) evaluated in this way is (4.8 ± 1.1) × 10 −6 Mpc −3 in the redshift bin 1.2-2.2. This density is ∼ 44% of that of all X-ray selected QSOs in the same redshift and luminosity bin, and it is consistent with the expectation of most up-to-date AGN synthesis models for the Cosmic X-ray background ). The density of lower luminosity Compton-thick AGN (logL(2-10keV)=43.5-44) at z=0.7-1.2 is (3.7 ± 1.1) × 10 −5 Mpc −3 , corresponding to ∼ 67% of that of X-ray selected AGN. The comparison between the fraction of infrared selected, Compton thick AGN to the X-ray selected, unobscured and moderately obscured AGN at high and low luminosity suggests that Compton-thick AGN follow a luminosity dependence similar to that discovered for Compton-thin AGN, becoming relatively rarer at high luminosities. We estimate that the fraction of AGN (unobscured, moderately obscured and Compton thick) to the total MIPS source population is 49 ± 10%, a value significantly higher than that previously estimated at similar 24µm fluxes. We discuss how our findings can constrain AGN feedback models.

We present a study of the host galaxies of AGN selected from the zCOSMOS survey to establish if accretion onto Supermassive Black Holes (SMBHs) and star formation are explicitly linked up to z ∼ 1. We identify 152 galaxies that harbor AGN, based on their X-ray emission (L 0.5−10 keV > 10 42 erg s −1 ) detected by XM M −N ewton observations of 7543 galaxies (i acs < 22.5). Star formation rates (SFRs), including those weighted by stellar mass, of a subsample are determined using the [OII]λ3727 emissionline luminosity, corrected for an AGN contribution based on the observed [OIII]λ5007 strength or that inferred by their hard (2-10 keV) X-ray luminosity. We find that an overwhelming majority of AGN host galaxies have significant levels of star formation with a distribution spanning ∼ 1 − 100 M ⊙ yr −1 ; their average SFR is higher than that of galaxies with equivalent stellar mass (M * > 4 × 10 10 M ⊙ ). The close association between AGN activity and star formation is further substantiated by an increase in the fraction of galaxies hosting AGN with the youthfulness of their stars as indicated by the rest-frame color (U-V) and spectral index D n (4000); we demonstrate that a mass-selected sample is required to alleviate an artifical peak in the AGN fraction falling in the transition region due to the fact that many 'blue cloud' galaxies have low mass-to-light ratios in luminosity-limited samples. We also find that the SFRs of AGN hosts evolve with cosmic time in a manner that closely mirrors the overall galaxy population and naturally explains the low SFRs in AGNs (z < 0.3) from the SDSS. We conclude that the conditions most conducive for AGN activity are a massive host galaxy and a large reservoir of gas. Furthermore, a direct correlation between mass accretion rate onto SMBHs and SFR is shown to be weak although the average ratio (∼ 10 −2 ) is constant with redshift, effectively shifting the evidence for a co-evolution scenario in a statistical manner to smaller physical scales (i.e., within the same galaxies). The order-of-magnitude increase in this ratio compared to the locally measured value of M BH /M bulge , is consistent with an AGN lifetime substantially shorter than that of star formation. Our findings illustrate an intermittent scenario with underlying complexities regarding fueling over vastly different physical (and temporal) scales yet to be firmly determined.

We extend our earlier work on X‐ray source stacking in the deep XMM–Newton observation of the Lockman Hole, to the 2‐Ms Chandra Deep Field North (CDF‐N) and the 1‐Ms Chandra Deep Field South (CDF‐S). The XMM–Newton work showed the resolved fraction of the X‐ray background (XRB) to be ∼80–100 per cent at ≲ 2 keV but this decreased to only ∼50 per cent above ∼8 keV. The CDF‐N and CDF‐S probe deeper, and are able to fill in some of the missing fraction in the 4–6 keV range, but the resolved fraction in the 6–8 keV band remains only ∼60 per cent, confirming the trend seen with XMM–Newton. The missing XRB component has a spectral shape that is consistent with a population of highly obscured active galactic nuclei (AGN) at redshifts ∼0.5–1.5 and with absorption column densities of ∼1023–1024 cm−2.