We present optical spectroscopic identifications of X-ray sources in \sim 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 ^ { \prime } \leq 22 mag and the 0.5 - 2 keV flux ( f _ { 0.5 - 2 keV } ) > 1 \times 10 ^ { -15 } erg cm ^ { -2 } s ^ { -1 } , we observed 695 objects and obtained reliable spectroscopic identification for 489 sources , \sim 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 ( \alpha _ { ox } ) of the broad-line AGNs is 1.47 \pm 0.03 , 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 Å 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 ^ { \prime \prime } of each of them , whereas , 2 and 14 XMM sources have , respectively , 3 and 2 possible optical sources within 6 ^ { \prime \prime } of each of them .
Spectra of multiple possible counterparts were obtained in such ambiguous cases .