Beta Lusso
Thursday January 19th 2023 1:30PM – 2:30PM
Room U2-2016
Abstract
What quasars can tell us on the accelerating Universe.
I will present the latest results on our analysis of the non-linear X-ray to ultraviolet luminosity relation in a sample of optically selected quasars from SDSS, cross-matched with the most recent XMM-Newton and Chandra catalogues. I will show that this correlation is very tight, implying that the observed relation is the manifestation of an ubiquitous (but still unknown) physical mechanism, that regulates the energy transfer from the accretion disc to the X-ray emitting corona in quasars. I will then discuss what the perspectives of quasars in the context of observational cosmology are and present new measurements of the expansion rate of the Universe in the redshift range z=0.5-7.5 based on a Hubble diagram of quasars.