ASTRONOMY COLLOQUIUM

One of the last great unknowns in our history of the universe is when and how the first galaxies emerged after the Big Bang. These galaxies transformed the cosmos – they illuminated the invisible scaffolding of dark matter that underpins the universe, they ionized the intergalactic reservoirs of hydrogen, and they synthesized the elements that would one day seed life on Earth. Thanks to JWST, these enigmatic galaxies are finally coming into view. In this talk I will discuss new classes of galaxies that JWST is revealing, with a focus on: (i) extremely luminous galaxies at redshifts z>10 whose emergence at such early times is challenging our models of galaxy evolution and perhaps even cosmology, (ii) the ``little red dots" -- a surprisingly abundant population of highly obscured supermassive black holes that may upend our understanding of cosmic reionization, and reveal long-sought stages of supermassive black hole growth. I will end by previewing an upcoming (Nov 2023) program I am leading that seeks to find signatures of Pop III stars aided by gravitational lensing in the Epoch of Reionization.