Speaker
Description
Measuring cosmic distances accurately is a critical challenge in astrophysics, pivotal for our understanding of the Universe expansion history and for testing cosmological models. In this talk, I will explore two innovative methods for using Active Galactic Nuclei (AGN) as tools for distance measurement. AGN, notable for their extreme luminosity, can be observed even at high redshifts; however, their variable emission precludes straightforward distance estimations based on flux measurements alone. I will describe two techniques developed to standardize AGN and use them for distances. Firstly, I will examine the X-ray – UV luminosity relation in quasars—the most luminous types of AGN. I will discuss recent advancements in enhancing the reliability and precision of distance estimates obtained with this relation and how they challenge the standard ΛCDM cosmological model's predictions when implemented with SNe in the Hubble Diagram. Secondly, I will explore the correlation between AGN X-ray variability and black hole mass, utilizing the BASS dataset at low redshifts to characterize it. Additionally, I will discuss the potential impacts of forthcoming data from the Euclid, LSST, and Athena missions.
