Callum Witten

Postdoctoral Researcher · Kavli Institute for Cosmology, University of Cambridge

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I’m a postdoctoral researcher at the Kavli Institute for Cosmology, University of Cambridge, working with the Extragalactic Astrophysics Group of Roberto Maiolino and Sandro Tacchella. I study galaxies in the first billion years of the Universe, combining observations from the James Webb Space Telescope and ESO’s Very Large Telescope with large-scale cosmological simulations.

My research studies how the first galaxies and black holes formed and grew, and how their surroundings shaped them, from galaxy mergers to the densest overdensities that will go on to become today’s galaxy clusters.

I’m PI of JWST programme 4043 and of several VLT programmes using KMOS and X-shooter.

Before starting my postdoc in Cambridge in 2026, I was a postdoctoral researcher at the University of Geneva in Pascal Oesch’s Galaxy Build-up at Cosmic Dawn group. I did my PhD at the Institute of Astronomy in Cambridge (2021–2024), supervised by Debora Sijacki and Nicolas Laporte, with a thesis titled New insights into primeval galaxies in the era of JWST, and was awarded the 2025 Murdin Prize for the best publication by a PhD student. Before that, I studied for an MPhys in Physics with Astrophysics at the University of Bath.

See my research, publications or CV.

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