A. Gueguen

The XMM Large-Scale Structure survey: the X-ray pipeline and survey selection function

We present the X-ray pipeline developed for the purpose of the cluster search in the XMM-LSS survey. It is based on a two-stage procedure via a dedicated handling of the Poisson nature of the signal: (1) source detection on multi-resolution wavelet filtered images; (2) source analysis by means of a maximum likelihood fit to the photon images. The source detection efficiency and characterisation are studied through extensive Monte-Carlo simulations. This led us to define two samples of extended sources: the C1 class that is uncontaminated, and the less restrictive C2 class that allows for 50% contamination. The resulting predicted selection function is presented and the comparison to the current XMM-LSS confirmed cluster sample shows very good agreement. We arrive at average predicted source densities of about 7 C1 and 12 C2 per deg 2 , which is higher than any available wide field X-ray survey. We finally notice a substantial deviation of the predicted redshift distribution for our samples from the one obtained using the usual assumption of a flux limited sample.

The XMM-LSS survey: optical assessment and properties of different X-ray selected cluster classes

Context. XMM and Chandra opened a new area for the study of clusters of galaxies not only for cluster physics, but also for the detection of faint and distant clusters that were inaccessible with previous missions. Aims. This article presents 66 spectroscopically confirmed clusters (0.05 \textless= z \textless= 1.5) within an area of 6 deg(2) enclosed in the XMM-LSS survey. Almost two thirds have been confirmed with dedicated spectroscopy only and 10% have been confirmed with dedicated spectroscopy supplemented by literature redshifts. Methods. Sub-samples, or classes, of extended-sources are defined in a two-dimensional X-ray parameter space allowing for various degrees of completeness and contamination. We describe the procedure developed to assess the reality of these cluster candidates using the CFHTLS photometric data and spectroscopic information from our own follow-up campaigns. Results. Most of these objects are low-mass clusters, hence constituting a still poorly studied population. In a second step, we quantify the correlations between the optical properties such as richness or velocity dispersion and the cluster X-ray luminosities. We examine the relation of the clusters to the cosmic web. Finally, we review peculiar compact structures in the surveyed area such as very distant clusters and fossil groups.

The XMM Large-Scale Structure survey: a well-controlled X-ray cluster sample over the D1 CFHTLS area

We present the XMM Large-Scale Structure Survey (XMM-LSS) cluster catalogue corresponding to the Canada-France-Hawaii Telescope Legacy Survey Dl area. The list contains 13 spectroscopically confirmed, X-ray selected galaxy clusters over 0.8 deg 2 to a redshift of unity and so constitutes the highest density sample of clusters to date. Cluster X-ray bolometric luminosities range from 0.03 to 5 x 10 44 erg s -1 . In this study, we describe our catalogue construction procedure: from the detection of X-ray cluster candidates to the compilation of a spectroscopically confirmed cluster sample with an explicit selection function. The procedure further provides basic X-ray products such as cluster temperature, flux and luminosity. We detected slightly more clusters with (0.5-2.0 keV) X-ray fluxes of >2 x 10 -14 erg s -1 cm -2 than we expected based on expectations from deep ROSAT surveys. We also present the luminosity-temperature relation for our nine brightest objects possessing a reliable temperature determination. The slope is in good agreement with the local relation, yet compatible with a luminosity enhancement for the 0.15 < z < 0.35 objects having 1 < T < 2 keV, a population that the XMM-LSS is identifying systematically for the first time. The present study permits the compilation of cluster samples from XMM images whose selection biases are understood. This allows, in addition to studies of large-scale structure, the systematic investigation of cluster scaling law evolution, especially for low mass X-ray groups which constitute the bulk of our observed cluster population. All cluster ancillary data (images, profiles, spectra) are made available in electronic form via the XMM-LSS cluster data base.

The XMM Large Scale Structure Survey: Properties and Two-Point Angular Correlations of Point-like Sources ⋆

We analyze X-ray sources detected over 4.2 pseudo-contiguous sq. deg. in the 0.5–2 keV and 2–10 keV bands down to fluxes of 2 × 10 −15 and 8 × 10 −15 erg s −1 cm −2 respectively, as part of the XMM-Newton Large Scale Structure Survey. The logN–logS in both bands shows a steep slope at bright fluxes, but agrees well with other determinations below ∼2 × 10 −14 erg s −1 cm −2 . The detected sources resolve close to 30 per cent of the X-ray background in the 2–10 keV band. We study the two-point angular clustering of point sources using nearest neighbours and correlation function statistics and find a weak, positive signal for ∼1130 sources in the 0.5–2 keV band, but no correlation for ∼400 sources in the 2–10 keV band below scales of 100 arcsec. A sub-sample of ∼200 faint sources with hard X-ray count ratios, that is likely to be dominated by obscured AGN, does show a positive signal with the data allowing for a large angular correlation length, but only at the ∼ 2( 3)σ level, based on re-sampling (Poisson) statistics. We discuss possible implications and emphasize the importance of wider, complete surveys in order to fully understand the large scale structure of the X-ray sky.

Gaia Data Release 2. The catalogue of radial velocity standard stars

Aims. The Radial Velocity Spectrometer (RVS) on board the ESA satellite mission Gaia has no calibration device. Therefore, the radial velocity zero point needs to be calibrated with stars that are proved to be stable at a level of 300 m/s during the Gaia observations. Methods. We compiled a dataset of ~71000 radial velocity measurements from five high-resolution spectrographs. A catalogue of 4813 stars was built by combining these individual measurements. The zero point was established using asteroids. Results. The resulting catalogue has seven observations per star on average on a typical time baseline of six years, with a median standard deviation of 15 m/s. A subset of the most stable stars fulfilling the RVS requirements was used to establish the radial velocity zero point provided in Gaia Data Release 2. The stars that were not used for calibration are used to validate the RVS data.

The XMM-Large Scale Structure catalogue: X-ray sources and associated optical data. Version I

Following the presentation of the XMM-Large Scale Structure (XMM-LSS) survey X-ray source detection package by Pacaud et al., we provide the source lists for the first surveyed 5.5 deg 2 . The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain in total 3385 point-like or extended sources above a detection likelihood of 15 in either band. The agreement with deep log N- log S is excellent. The main parameters considered are position, count rate, source extent with associated likelihood values. A set of additional quantities such as astrometric corrections and fluxes are further calculated while errors on the position and count rate are deduced from simulations. We describe the construction of the band-merged catalogue allowing rapid subsample selection and easy cross-correlation with external multiwavelength catalogues. A small optical Canada-France-Hawaii Telescope Legacy Survey multiband subset of objects are associated with each source along with an X-ray/optical overlay. We make the full X-ray images available in FITS format. The data are available at the Centre de Donnees de Strasbourg and, in a more extended form, at the Milan XMM-LSS survey data base.

The XMM large-scale structure survey: A well-controlled X-ray cluster sample over the D1 CFHTLS area

We present the XMM Large-Scale Structure Survey (XMM-LSS) cluster catalogue corresponding to the Canada-France-Hawaii Telescope Legacy Survey Dl area. The list contains 13 spectroscopically confirmed, X-ray selected galaxy clusters over 0.8 deg 2 to a redshift of unity and so constitutes the highest density sample of clusters to date. Cluster X-ray bolometric luminosities range from 0.03 to 5 x 10 44 erg s -1 . In this study, we describe our catalogue construction procedure: from the detection of X-ray cluster candidates to the compilation of a spectroscopically confirmed cluster sample with an explicit selection function. The procedure further provides basic X-ray products such as cluster temperature, flux and luminosity. We detected slightly more clusters with (0.5-2.0 keV) X-ray fluxes of >2 x 10 -14 erg s -1 cm -2 than we expected based on expectations from deep ROSAT surveys. We also present the luminosity-temperature relation for our nine brightest objects possessing a reliable temperature determination. The slope is in good agreement with the local relation, yet compatible with a luminosity enhancement for the 0.15 < z < 0.35 objects having 1 < T < 2 keV, a population that the XMM-LSS is identifying systematically for the first time. The present study permits the compilation of cluster samples from XMM images whose selection biases are understood. This allows, in addition to studies of large-scale structure, the systematic investigation of cluster scaling law evolution, especially for low mass X-ray groups which constitute the bulk of our observed cluster population. All cluster ancillary data (images, profiles, spectra) are made available in electronic form via the XMM-LSS cluster data base.

The XMM-LSS catalogue: X-ray sources and associated optical data. Version I

Following the presentation of the XMM-Large Scale Structure (XMM-LSS) survey X-ray source detection package by Pacaud et al., we provide the source lists for the first surveyed 5.5 deg 2 . The catalogues pertain to the [0.5-2] and [2-10] keV bands and contain in total 3385 point-like or extended sources above a detection likelihood of 15 in either band. The agreement with deep log N- log S is excellent. The main parameters considered are position, count rate, source extent with associated likelihood values. A set of additional quantities such as astrometric corrections and fluxes are further calculated while errors on the position and count rate are deduced from simulations. We describe the construction of the band-merged catalogue allowing rapid subsample selection and easy cross-correlation with external multiwavelength catalogues. A small optical Canada-France-Hawaii Telescope Legacy Survey multiband subset of objects are associated with each source along with an X-ray/optical overlay. We make the full X-ray images available in FITS format. The data are available at the Centre de Donnees de Strasbourg and, in a more extended form, at the Milan XMM-LSS survey data base.

The XMM-LSS Survey: A well controlled X-ray cluster sample over the D1 CFHTLS area

We present the XMM Large-Scale Structure Survey (XMM-LSS) cluster catalogue corresponding to the Canada-France-Hawaii Telescope Legacy Survey Dl area. The list contains 13 spectroscopically confirmed, X-ray selected galaxy clusters over 0.8 deg 2 to a redshift of unity and so constitutes the highest density sample of clusters to date. Cluster X-ray bolometric luminosities range from 0.03 to 5 x 10 44 erg s -1 . In this study, we describe our catalogue construction procedure: from the detection of X-ray cluster candidates to the compilation of a spectroscopically confirmed cluster sample with an explicit selection function. The procedure further provides basic X-ray products such as cluster temperature, flux and luminosity. We detected slightly more clusters with (0.5-2.0 keV) X-ray fluxes of >2 x 10 -14 erg s -1 cm -2 than we expected based on expectations from deep ROSAT surveys. We also present the luminosity-temperature relation for our nine brightest objects possessing a reliable temperature determination. The slope is in good agreement with the local relation, yet compatible with a luminosity enhancement for the 0.15 < z < 0.35 objects having 1 < T < 2 keV, a population that the XMM-LSS is identifying systematically for the first time. The present study permits the compilation of cluster samples from XMM images whose selection biases are understood. This allows, in addition to studies of large-scale structure, the systematic investigation of cluster scaling law evolution, especially for low mass X-ray groups which constitute the bulk of our observed cluster population. All cluster ancillary data (images, profiles, spectra) are made available in electronic form via the XMM-LSS cluster data base.