Seeking Multiwavelength Signs of Rapid Accretion in Active Galactic Nuclei

The existence of active galactic nuclei (AGNs) hosting supermassive black holes at high redshift (z > 6) suggests that soon after the Big Bang, some black holes grew quickly through mergers and/or accretion. Growth through the latter likely required episodes of extremely rapid accretion undeterred by radiation pressure slowing the rate at which material flows through the event horizon. To understand how efficiently seed black holes can accrete to supermassive sizes, better constraints are needed on the observational characteristics of rapid accretion, especially its impact on the structure and radiative output of the AGN central engine and surrounding regions. In this talk, I summarize results and ongoing work performed in support of my PhD dissertation. Using new and archival observations across radio, optical, ultraviolet, and X-ray bands, we test an existing hypothesis in which radiative inefficiency may allow extremely high accretion rates, and we find support for such in samples of both supermassive and intermediate-mass AGNs. We conclude by suggesting new observational signatures for finding rapidly accreting AGNs. Such samples will improve our understanding of the interaction of AGN emission mechanisms and the efficiency of black hole growth through accretion.