Optical identification of XMM sources in the CFHTLS
  We present optical spectroscopic identifications of X-ray sources in ~3
square degrees of the XMM-Large Scale Structure survey (XMM-LSS), also covered
by the Canada France Hawaii Telescope Legacy Survey (CFHTLS), obtained with the
AAOmega instrument at the Anglo Australian Telescope. In a flux limited sample
of 829 point like sources in the optical band with g' <~22 mag and the 0.5-2
keV flux > 1x10^{-15}erg/cm^2/s, we observed 695 objects and obtained reliable
spectroscopic identification for 489 sources, ~59% of the overall sample. We
therefore increase the number of identifications in this field by a factor
close to five. Galactic stellar sources represent about 15% of the total
(74/489). About 55% (267/489) are broad-line Active Galactic Nuclei (AGNs)
spanning redshifts between 0.15 and 3.87 with a median value of 1.68. The
optical-to-X-ray spectral index of the broad-line AGNs is 1.47, typical of
optically-selected Type I quasars and is found to correlate with the rest frame
X-ray and optical monochromatic luminosities at 2 keV and 2500 angstroms
respectively. Consistent with previous studies, we find alpha_ox not to be
correlated with z. In addition, 32 and 116 X-ray sources are, respectively
absorption and emission-line galaxies at z<0.76. From a line ratio diagnostic
diagram it is found that in about 50% of these emission line galaxies, the
emission lines are powered significantly by the AGN. Thirty of the XMM sources
are detected at one or more radio frequencies. In addition, 24 sources have
ambiguous identification: in 8 cases, two XMM sources have a single optical
source within 6 arcsecs of each of them, whereas, 2 and 14 XMM sources have,
respectively, 3 and 2 possible optical sources within 6 arcsecs of each of
them.
