Census of Black Hole Accretion Structure and Mass

Reliable measurements of black hole mass and accretion-disk structure are critical to understanding the growth history of black holes and galaxy evolution over cosmic time. Beyond the local universe, the gold standard for black hole mass and accretion-disk structure measurement is reverberation mapping, a technique that uses light echoes to measure the distance between the black-hole accretion disk and the gas clouds in the broad-line region. I will present the latest results from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project and show how it has transformed our understanding of supermassive black holes by dramatically expanding the number of quasars with reliable mass and accretion structure at z > 0.3. I will also present a promising new method for reliably measuring mass and accretion structure of early black holes using direct accretion-disk structure measurement from future massive time-domain quasar studies with SDSS-V and the Rubin Observatory's Legacy Survey of Space and Time.