ELISABETA LUSSO
(Dipartimento di Astronomia-INAF/OABO)
We present a study of the X-ray to optical properties of a large sample
of X-ray selected AGN from the XMM-COSMOS survey. In particular, we discuss the
relationship between UV and X-ray luminosity, as parameterized by the
$\alpha_{ox}$ spectral slope, and its dependence from redshift and luminosity.
The sample used in the analysis consists of 560 Type 1 AGN.
About 60\% of them are spectroscopically identified Type 1 AGN, while
the others are classified as Type 1 AGN on the basis of their multi-band
Spectral Energy Distribution. The inclusion of the photometrically classified Type 1 AGN is necessary to characterize our
sample as purely X-ray selected, with no bias at faint optical magnitudes.
We compare our findings with previous investigations on optically selected
broad line AGN (mostly from SDSS) and discuss the role of band selection in
the determination of the X-ray to UV ratio, its dependence with luminosity
and possibly with redshift and the implications for the AGN luminosity function
and bolometric corrections.