The puzzling emergence of galaxies in the first billion years and their cosmological implications
Pratika Dayal
CITA

Galaxy formation in the first billion years marks a time of great upheavalin our cosmic history: the first sources of light in the Universe, thesegalaxies ended the 'cosmic dark ages' and produced the first photons thatcould break apart the hydrogen atoms suffusing all of space startingthe process of 'cosmic reionization'. The past few years have seencutting-edge instruments such as the James Webb Space Telescope (JWST)provide tantalising glimpses of such galaxies assembling in an infantUniverse. Puzzlingly, these observations are also yielding a sample ofunexpectedly numerous and large black holes (up to a 100 million solarmasses) within the first 600 million years, posing an enormous challengefor galaxy formation models. I will show how this data is providingan unprecedented opportunity to pin down the reionization state of theUniverse in addition to providing an unrivalled resource for understandingthe reionization topology in the forthcoming era of 21cm cosmology. Iwill also show how these early systems provide a powerful testbed for DarkMatter models beyond ?Cold Dark Matter?. Finally, I will try to givea flavour of the gravitational wave event rates expected from such earlyblack holes in the Laser Interferometer Space Antenna Array (LISA) era.

Date:	Mardi, le 2 décembre 2025
Heure:	15:30
Lieu:	Université McGill
	Ernest Rutherford Physics, R.E. Bell Conference Room (room 103)