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See detailThe XMM-LSS survey: optical assessment and properties of different X-ray selected cluster classes
Adami, C.; Mazure, A.; Pierre, M. et al

in Astronomy and Astrophysics (2011), 526(A18), 36

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 ... [more ▼]

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. This article presents 66 spectroscopically confirmed clusters (0.05<z<1.5) within an area of 6 deg2 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. 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. Most of these objects are low mass clusters, hence constituting a still poorly studied population. In a second step, we quantify 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 structures in the surveyed area like very distant clusters and fossil groups. [less ▲]

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See detailStructure detection in the D1 CFHTLS deep field using accurate photometric redshifts: a benchmark
Mazure, A.; Adami, C.; Pierre, M. et al

in Astronomy and Astrophysics (2007), 467(1), 49-62

Aims. We investigate structures in the D1 CFHTLS deep field to test the method that will be applied to generate homogeneous samples of clusters and groups of galaxies in order to constrain the cosmology ... [more ▼]

Aims. We investigate structures in the D1 CFHTLS deep field to test the method that will be applied to generate homogeneous samples of clusters and groups of galaxies in order to constrain the cosmology and detailed physics of groups and clusters. Methods. An adaptive kernel technique was applied to galaxy catalogues. This technique needs none of the usual a-priori assumptions ( luminosity function, density profile, colour of galaxies) made with other methods. Its main drawback ( decrease in efficiency with increasing background) is overcome by the use of narrow slices in photometric redshift space. There are two main concerns in structure detection. One is false detection and the second, the evaluation of the selection function in particular if one wants complete samples. We deal with the first concern using random distributions. For the second, comparison with detailed simulations is foreseen but we used a pragmatic approach by comparing our results to GalICS simulations to check that our detection number is not totally at odds with cosmological simulations. We used the XMM-LSS survey and secured VVDS redshifts up to z similar to 1 to check individual detections. Results. We show that our detection method is basically able to recover 100% of the C1 XMM-LSS X-ray detections ( in the regions in common) in the correct redshift range plus several other candidates. Moreover, when spectroscopic data are available, we confirm our detections, even those without X-ray data. [less ▲]

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