Large Scale Structure survey

Galaxy groups and low-mass clusters provide important laboratories in which to study X-ray gas physics and the interplay between galaxy evolution and environmental effects. The X-ray Multi-Mirror (XMM) Large Scale Structure (LSS) survey has currently imaged 5 deg 2 to a nominal extended source flux limit of order 10 −14 ergs s −1 cm −2 and is dominated numerically by low-mass groups and clusters at redshifts 0.2 < z < 0.6. We discuss the generation of the XMM-LSS cluster sample, initial results on the physics of groups and low-mass clusters and the prospects for detailed follow-up studies of these systems. The XMM-LSS survey (Pierre et al. 2004) is a medium-deep X-ray survey undertaken to determine the values of key cosmological parameters on the basis of the observed abundance and correlation statistics of X-ray galaxy clusters. The XMM-LSS consists of a contiguous grid of 10-20 ks XMM pointings currently covering 5 deg 2. Observations extending the X-ray coverage to 10 deg 2 are in progress during 2006. The XMM-LSS field is located at α = 02 h 26 m , δ = −5 • and overlaps with Canada France Hawaii Wide Synoptic Survey (optical), the UKIDSS Deep Extragalactic Survey (NIR), the SWIRE survey (mid-IR), the VIMOS-VLT Deep Survey (VVDS-optical spectra) and is accompanied by additional imaging at radio and SZ wavebands-see Figure 1 for more details. The XMM-LSS currently contains X-ray structures over the redshift interval 0.05 < z < 1.22 (Figure 1) yet is dominated numerically by cooler, lower mass clusters kT < 4 keV at redshifts 0.2 < z < 0.6. The nominal flux limit of XMM-LSS is approximately 10 −14 ergs s −1 cm −2 in the [0.5-2] keV energy band and corresponds to a bolometric X-ray luminosity L X ≈ 10 43