Speaker
Description
Understanding the relationship between the UV/optical emission from the accretion disc and the X-ray emission associated with the corona is vital to understand differing AGN accretion states and thus the growth phases of black holes. The optical-to-X-ray spectral slope describes the relative strength of the hard X-rays to the accretion disc emission which peaks in the UV. The well-established anti-correlation between alpha_ox and UV luminosity has long suggested that the more luminous the quasar, the weaker the corona and the weaker the hard ionising radiation. However, this observational alpha_ox relation is subject to selection effects and biases. Utilising the optically-selected sample (from SDSS-IV) of AGN in the XXL field and Stripe 82 region (0.5 < z < 4), alongside their XMM X-ray observations, we have carefully controlled for the X-ray incompleteness, by way of maximum likelihood fitting, to derive the distribution of X-ray and UV luminosities and the intrinsic alpha_ox relation, while accounting for any possible redshift evolution. The next step in the project will be to utilise the quasar sample from SDSS-V in order to characterise the optical properties of an X-ray selected sample. As a result, we can evaluate our understanding of the connection between the accretion disc and corona.
