NBIA Junior Colloquium: Anne Katharina Hutter

Title: The Cosmic Reionisation Puzzle: Unveiling the Nature of the First Galaxies

Abstract: The radiation emitted by the first galaxies in our Universe ionised the hydrogen in the intergalactic medium (IGM) during the first billion years, ushering in the Epoch of Reionisation. How did this last major phase transition that governed the evolution of the galaxies we see today happen? Was it driven by the few bright or numerous faint galaxies? These questions hinge on understanding the first galaxies’ nature, specifically their stellar populations generating ionising radiation, the fraction of this radiation escaping into the IGM, and how these characteristics depend on the galaxies' properties. Observations with optical to infrared telescopes, especially the James Webb Space Telescope (JWST), are beginning to unravel these questions and challenge standard theoretical models, revealing an unexpectedly high abundance of bright galaxy candidates in the first 400 million years after the Big Bang. I will discuss the physical processes governing the radiation emerging from the first galaxies and explore how these - and particularly a higher abundance of massive stars - might explain the high abundance of bright z>10 galaxies observed with JWST.

Short Bio: Anne Hutter is a DAWN fellow at the Niels Bohr Institute, focusing on modelling the Universe during its first billion years. She received her PhD from the Leibniz-Institute for Astrophysics in Potsdam and joined the Cosmic Dawn Center in 2022, following postdoctoral positions at the University of Groningen and Swinburne University of Technology in Melbourne.