   The XMM large-scale structure survey: an initial sample of galaxy groups and clusters to a redshift z < 0.6; ; et al in Monthly Notices of the Royal Astronomical Society (2005), 363(2), 675-691 We present X-ray and optical spectroscopic observations of 12 galaxy groups and clusters identified within the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey. Groups and clusters are selected ... [more ▼] We present X-ray and optical spectroscopic observations of 12 galaxy groups and clusters identified within the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey. Groups and clusters are selected as extended X-ray sources from a 3.5 deg(2) XMM image mosaic above a flux limit 8 x 10(-15) erg s(-1) cm(-2) in the [0.5-2] keV energy band. Deep BVRI images and multi-object spectroscopy confirm each source as a galaxy concentration located within the redshift interval 0.29 < z < 0.56. We combine line-of-sight velocity dispersions with the X-ray properties of each structure computed from a two-dimensional surface brightness model and a single temperature fit to the XMM spectral data. The resulting distribution of X-ray luminosity, temperature and velocity dispersion indicate that the XMM-LSS survey is detecting low-mass clusters and galaxy groups to redshifts z < 0.6. Confirmed systems display little or no evidence for X-ray luminosity evolution at a given X-ray temperature compared to lower-redshift X-ray group and cluster samples. A more complete understanding of these trends will be possible with the compilation of a statistically complete sample of galaxy groups and clusters anticipated within the continuing XMM-LSS survey. [less ▲] Detailed reference viewed: 16 (6 ULg) The XMM-LSS survey - First high redshift galaxy clusters: Relaxed and collapsing systems; ; et al in Astronomy and Astrophysics (2004), 423(1), 75-85 We present five newly found galaxy clusters at z > 0.6 from the XMM Large-Scale Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the XMM images. For three of them we have ... [more ▼] We present five newly found galaxy clusters at z > 0.6 from the XMM Large-Scale Structure Survey (XMM-LSS). All five objects are extended X-ray sources in the XMM images. For three of them we have sufficient spectroscopically confirmed member galaxies that an estimate of the velocity dispersion is possible: XLSSC 001 at z = 0.613 and sigma(nu) = 867(-60)(+80) km s(-1), XLSSC 002 at z = 0.772 and sigma(nu) = 524(-116)(+267) km s(-1) and XLSSC 003 at z = 0.839 and sigma(V) = 780(-75)(+137) km s(-1). These three clusters have X-ray bolometric luminosities L-X similar to 1-3 x 10(44) erg s(-1) and temperatures 2-4 keV, and consequently are less massive than previously known clusters at similar redshifts, but nevertheless they follow the low redshift scaling relations between L-X, T and sigma(upsilon), within the limits of the measurement errors. One of the clusters, XLSSC 004, is detected independently as an over-density of galaxies of a colour R - z' = 1.4 that matches the redshift of the central galaxy z = 0.87, although it cannot unambiguously be confirmed by the spectroscopic observations alone. The highest redshift candidate cluster pertaining to this paper, XLSSC 005, is most likely a double cluster complex at a redshift around unity, associated with an extended X-ray source with probable substructure. [less ▲] Detailed reference viewed: 33 (1 ULg) |
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