Events

How Long do Quasars Shine?

Abstract: Luminous quasars are believed to be the progenitors of the supermassive
black holes observed ubiquitously at the centers of all massive galaxies, but we are still
in the dark about how these black holes formed. Our ignorance largely results from the
fact that the expected timescale for supermassive black hole growth of 50 million years
is far longer than the mere fifty years that humans have been observing quasars. A holy
grail would thus be a direct measurement of quasar lifetimes, shedding light on the
physical mechanisms responsible for fueling black hole growth, and how the back-
reaction of this growth might influence how galaxies form.  I will discuss two very
different experiments that allow us to construct cosmic clocks that can accurately time
the duration of luminous quasar activity on timescales of kiloyears to gigayears. One
exploits the clustering pattern of quasars on the sky, which has recently been measured
by JWST. The other uses observations of diffuse intergalactic gas in quasar environs. I
will also touch upon how the latter can be used to constrain the reionization history of
the Universe.

Zoom Link

Monday, December 9, 2024 11:00 AM