YCIU Seminar with Meg Urry, Yale Astronomy & Physics

Title: Accretion onto Black Holes: What We Learn from the Eddington Ratio

Abstract: Accretion onto black holes powers emission from X-ray binaries (~10 solar mass BH) and the Active Galactic Nuclei (AGN) that lie at the centers of galaxies (~106-1010 solar mass BH). The black holes themselves are quite similar, apart from mass scale, but in each case our understanding of accretion has been dominated by superficial issues like geometry and wavelength-dependent absorption, unrelated to the underlying accretion flow. After introducing this landscape, I will show that the most important diagnostic of accretion is the Eddington ratio, which is a normalized accretion rate (essentially the bolometric AGN luminosity divided by the black hole mass). Specifically, I will present the first ever intrinsic distributions of Eddington ratios derived for both obscured and unobscured AGN. Differences between these two Eddington Ratio Distribution Functions (ERDFs) offer clues about how accretion rate affects the structure and evolution of AGN.