The intrinsic X-ray luminosity distribution of an optically selected SDSS quasar population.

In active galactic nuclei, the relationship between UV and X-ray luminosity is well studied (often characterised by αox) but often with heterogeneous samples. We have parametrized the intrinsic distribution of X-ray luminosity, L X, for the optically selected sample of SDSS quasars in the Stripe 82 and XXL fields across redshifts 0.5–3.5. We make use of the available XMM observations and a custom pipeline to produce Bayesian sensitivity curves that are used to derive the intrinsic X-ray distribution in a hierarchical Bayesian framework. We find that the X-ray luminosity distribution is well described by a Gaussian function in log10  L X space with a mean that is dependent on the monochromatic 2500 Å UV luminosity, L 2500. We also observe some redshift dependence of the distribution. The mean of the L X distribution increases with redshift while the width decreases. This weak but significant redshift dependence leads to L 2500– L X and L 2500–αox relations that evolve with redshift, and we produce a redshift- and L 2500-dependent αox equation. Neither black hole mass nor Eddington ratio appear to be potential drivers of the redshift evolution. [ABSTRACT FROM AUTHOR]