The XMM-LSS project: a short presentation of the survey and of the first results

We (Pierre et al. 2003) have designed a medium deep large area X-ray survey with XMM - the XMM Large Scale Structure survey, XMM-LSS - with the scope of extending the cosmological tests attempted using ROSAT cluster samples to two redshift bins between 0<z<1 while maintaining the precision of earlier studies. The optimal survey design was found to be an 8x8 deg2 area, paved with 10 ks XMM pointing separated by 20 arcmin. This area is the target of several complementary surveys, from the ultraviolet to the radio wavelengths, allowing, beside cosmological studies, detailed studies of the objects included in our area.