Thursday, September 17, 2020 - 2:30pm
National Research Council Canada
The origin of the most massive, high-redshift quasars
The discovery of billion solar mass quasars at redshifts of 6–7 challenges our understanding of the early Universe; how did such massive objects form in the first billion years? Observational constraints and numerical simulations increasingly favour the “direct collapse” scenario, in which rapid accretion in a primordial halo leads to the formation of an initially-massive (~100,000 solar mass) black hole from the collapse of a supermassive “seed.” In this talk, I’ll present a systematic study of the lives and deaths of these objects under a variety of formation conditions, and propose observational diagnostics to put the origin of high-z quasars to the test using next generation facilities. In particular, we find a simple relation between the infall rate and the final mass at collapse, rule out the existence of rapidly-rotating supermassive stars, and delineate the regimes for which objects either undergo “truly direct” collapse or survive to long-lived nuclear-burning under differing formation scenarios. I’ll also discuss zero metallicity stellar populations which are intermediate in mass between supermassive seeds and “typical” Pop III stars, as well as further observational prospects for understanding primordial stars in the era of JWST and more.ESO/M. Kornmesser.
An artist’s impression of CR7, a distant galaxy that may contain primordial stars