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We present a three-dimensional study of the local ( 100 h À1 kpc) and the large-scale ( 1 h À1 Mpc) environment of the two main types of Seyfert AGN galaxies. For this purpose we use 48 Seyfert 1 galaxies (with redshifts in the range 0:007 z 0:036) and 56 Seyfert 2 galaxies (with 0:004 z 0:020), located at high galactic latitudes, as well as two control samples of nonactive galaxies having the same morphological, redshift, and diameter size distributions as the corresponding Seyfert samples. Using the Center for Astrophysics (CfA2) and Southern Sky Redshift Survey (SSRS) galaxy catalogs (m B $ 15:5) and our own spectroscopic observations (m B $ 18:5), we find that within a projected distance of 100 h À1 kpc and a radial velocity separation of v P 600 km s À1 around each of our AGNs, the fraction of Seyfert 2 galaxies with a close neighbor is significantly higher than that of their control (especially within 75 h À1 kpc) and Seyfert 1 galaxy samples, confirming a previous two-dimensional analysis of Dultzin-Hacyan et al. We also find that the large-scale environment around the two types of Seyfert galaxies does not vary with respect to their control sample galaxies. However, the Seyfert 2 and control galaxy samples do differ significantly when compared to the corresponding Seyfert 1 samples. Since the main difference between these samples is their morphological type distribution, we argue that the large-scale environmental difference cannot be attributed to differences in nuclear activity but rather to their different type of host galaxies.

Context. The XXL Survey is the largest survey carried out by the XMM-Newton satellite and covers a total area of 50 square degrees distributed over two fields. It primarily aims at investigating the large-scale structures of the Universe using the distribution of galaxy clusters and active galactic nuclei as tracers of the matter distribution. The survey will ultimately uncover several hundreds of galaxy clusters out to a redshift of ∼2 at a sensitivity of ∼10 −14 erg s −1 cm −2 in the [0.5-2] keV band. Aims. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3 × 10 −14 erg s −1 cm −2 on the source flux within a 1 aperture. Methods. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. Results. The bright cluster sample consists of systems with masses between M 500 = 7 × 10 13 and 3 × 10 14 M , mostly located between z = 0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of σ 8 and/or Ω M appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z ∼ 1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters.

Context. The quest for the cosmological parameters that describe our universe continues to motivate the scientific community to undertake very large survey initiatives across the electromagnetic spectrum. Over the past two decades, the Chandra and XMM-Newton observatories have supported numerous studies of X-ray-selected clusters of galaxies, active galactic nuclei (AGNs), and the X-ray background. The present paper is the first in a series reporting results of the XXL-XMM survey; it comes at a time when the Planck mission results are being finalised. Aims. We present the XXL Survey, the largest XMM programme totaling some 6.9 Ms to date and involving an international consortium of roughly 100 members. The XXL Survey covers two extragalactic areas of 25 deg 2 each at a point-source sensitivity of ∼5 × 10 −15 erg s −1 cm −2 in the [0.5−2] keV band (completeness limit). The survey's main goals are to provide constraints on the dark energy equation of state from the spacetime distribution of clusters of galaxies and to serve as a pathfinder for future, wide-area X-ray missions. We review science objectives, including cluster studies, AGN evolution, and large-scale structure, that are being conducted with the support of approximately 30 follow-up programmes. Methods. We describe the 542 XMM observations along with the associated multi-λ and numerical simulation programmes. We give a detailed account of the X-ray processing steps and describe innovative tools being developed for the cosmological analysis. Results. The paper provides a thorough evaluation of the X-ray data, including quality controls, photon statistics, exposure and background maps, and sky coverage. Source catalogue construction and multi-λ associations are briefly described. This material will be the basis for the calculation of the cluster and AGN selection functions, critical elements of the cosmological and science analyses. Conclusions. The XXL multi-λ data set will have a unique lasting legacy value for cosmological and extragalactic studies and will serve as a calibration resource for future dark energy studies with clusters and other X-ray selected sources. With the present article, we release the XMM XXL photon and smoothed images along with the corresponding exposure maps.

This paper uses the first XMM–Newton Serendipitous Source Catalog compiled by the XMM–Newton Science Centre to identify low‐z X‐ray selected normal galaxy candidates. Our sample covers a total area of ≈6 deg2 to the 0.5–2 keV limit ≈10−15 erg s−1 cm−2. A total of 23 sources are selected on the basis of low X‐ray to optical flux ratio log fX/fopt < −2, soft X‐ray spectral properties and optical spectra, when available, consistent with stellar formation rather than active galactic nucleus (AGN) processes. This sample is combined with similarly selected systems from the Needles in the Haystack Survey to provide a total of 46 unique (z≲ 0.2) X‐ray detected normal galaxies, the largest low‐z sample yet available. This is first used to constrain the normal galaxy log N–log S at bright fluxes (10−15–10−13 erg s−1 cm−2). We estimate a slope of −1.46 ± 0.13 for the cumulative number counts consistent with the Euclidean prediction. We further combine our sample with 23 local (z≲ 0.2) galaxies from the Chandra Deep Field‐North and ‐South surveys to construct the local X‐ray luminosity function of normal galaxies. A Schechter form provides a good fit to the data with a break at log L★= 41.02+0.14−0.12 erg s−1 and a slope of α=−1.76 ± 0.10. Finally, for the sample of 46 systems, we explore the association between X‐ray luminosity and host galaxy properties, such as star formation rate (SFR) and stellar mass. We find that the LX of the emission‐line systems correlates with Hα luminosity and 1.4‐GHz radio power, both providing an estimate of the current SFR. In the case of early‐type galaxies with absorption‐line optical spectra, we use the K band as an approximation of stellar mass and find a correlation of the form LX∝L1.5K. This is flatter than the LX–LB relation for local ellipticals. This may be due to either LK providing a better approximation of galaxy mass or selection effects biasing our sample against very luminous early‐type galaxies, LX > 1042 erg s−1.

In this paper we estimate the local (z < 0.22) X‐ray luminosity function of ‘normal’ galaxies derived from the XMM–Newton Needles in the Haystack Survey. This is an on‐going project that aims to identify X‐ray‐selected normal galaxies (i.e. non‐AGN dominated) in the local Universe. We are using a total of 70 XMM–Newton fields covering an area of 11 deg2 which overlap with the Sloan Digital Sky Survey Data Release 2. Normal galaxies are selected on the basis of their resolved optical light profile, their low X‐ray‐to‐optical flux ratio [log (fx/fo) < − 2] and soft X‐ray colours. We find a total of 28 candidate normal galaxies to the 0.5–8 keV band flux limit of ≈2 × 10−15 erg cm−2 s−1. Optical spectra are available for most sources in our sample (82 per cent). These provide additional evidence that our sources are bona fide normal galaxies with X‐ray emission coming from diffuse hot gas emission and/or X‐ray binaries rather than a supermassive black hole. 16 of our galaxies have narrow emission lines or a late‐type spectral energy distribution (SED) while the remaining 12 present only absorption lines or an early‐type SED. Combining our XMM–Newton sample with 18 local (z < 0.22) galaxies from the Chandra Deep Field North and South surveys, we construct the local X‐ray luminosity function of normal galaxies. This can be represented with a Schechter form with a break at L★≈ 3+1.4−1.0× 1041 erg s−1 and a slope of α≈ 1.78 ± 0.12. Using this luminosity function and assuming pure luminosity evolution of the form ∝(1 +z)3.3 we estimate a contribution to the X‐ray background from normal galaxies of ∼10–20 per cent (0.5–8 keV). Finally, we derive, for the first time, the luminosity functions for early‐ and late‐type systems separately.

Context. In the currently debated context of using clusters of galaxies as cosmological probes, the need for well-defined cluster samples is critical. Aims. The XXL Survey has been specifically designed to provide a well characterised sample of some 500 X-ray detected clusters suitable for cosmological studies. The main goal of present article is to make public and describe the properties of the cluster catalogue in its present state, as well as of associated catalogues of more specific objects such as super-clusters and fossil groups. Methods. Following from the publication of the hundred brightest XXL clusters, we now release a sample containing 365 clusters in total, down to a flux of a few 10−15 erg s−1 cm−2 in the [0.5–2] keV band and in a 1′ aperture. This release contains the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. In this paper, we give the details of the follow-up observations and explain the procedure adopted to validate the cluster spectroscopic redshifts. Considering the whole XXL cluster sample, we have provided two types of selection, both complete in a particular sense: one based on flux-morphology criteria, and an alternative based on the [0.5–2] keV flux within 1 arcmin of the cluster centre. We have also provided X-ray temperature measurements for 80% of the clusters having a flux larger than 9 × 10−15 erg s−1 cm−2. Results. Our cluster sample extends from z ~ 0 to z ~ 1.2, with one cluster at z ~ 2. Clusters were identified through a mean number of six spectroscopically confirmed cluster members. The largest number of confirmed spectroscopic members in a cluster is 41. Our updated luminosity function and luminosity–temperature relation are compatible with our previous determinations based on the 100 brightest clusters, but show smaller uncertainties. We also present an enlarged list of super-clusters and a sample of 18 possible fossil groups. Conclusions. This intermediate publication is the last before the final release of the complete XXL cluster catalogue when the ongoing C2 cluster spectroscopic follow-up is complete. It provides a unique inventory of medium-mass clusters over a 50 deg2 area out to z ~ 1.

Scaling relations trace the formation and evolution of galaxy clusters. We exploited multiwavelength surveys -the XXL survey at XMM-Newton in the X-ray band, and the Hyper Suprime-Cam Subaru Strategic Program for optical weak lensing -to study an X-ray selected, complete sample of clusters and groups. The scalings of gas mass, temperature, and soft-band X-ray luminosity with the weak lensing mass show imprints of radiative cooling and AGN feedback in groups. From the multi-variate analysis, we found some evidence for steeper than self-similar slopes for gas mass (β mg|m = 1.73 ± 0.80) and luminosity (β l|m = 1.91 ± 0.94) and a nearly self-similar slope for the temperature (β t|m = 0.78 ± 0.43). Intrinsic scatters of X-ray properties appear to be positively correlated at a fixed mass (median correlation factor ρ X1X2|m ∼ 0.34) due to dynamical state and merger history of the halos. Positive correlations with the weak lensing mass (median correlation factor ρ mwlX|m ∼ 0.35) can be connected to triaxiality and orientation. Comparison of weak lensing and hydrostatic masses suggests a small role played by non-thermal pressure support (9 ± 17%).