Starts With A Bang #122 - Galaxy evolution and JWST

Oct 11, 2025

Join Dr. Olivia Cooper, a recent PhD and astronomy postdoc at CU Boulder, as she dives into the fascinating evolution of galaxies using data from the James Webb Space Telescope. She shares surprising findings about early, bright galaxies and the rapid maturation processes they undergo. Explore how multi-wavelength observations enhance our understanding and the critical importance of wide-field surveys like COSMOS-Web. Be captivated by the interplay between theory and observation in unveiling the rich diversity of cosmic structures!

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INSIGHT

Early Galaxy Surprises Explained

JWST found far more bright, early galaxies than many models predicted, forcing re-evaluation of assumptions.
Factors include better-than-expected optics, simulation resolution limits, bursty star formation, and AGN boosting brightness.

ADVICE

Test Models Against Data

Use observations to test and refine theoretical models rather than assuming models are complete.
Challenge assumptions and identify tensions between data and simulations to find new physics.

INSIGHT

Power Of Wide-Field JWST Surveys

Wide-but-deep surveys like COSMOS-Web capture rare galaxies and map cosmic environment variation.
This enables statistical studies of dense regions, voids, and reionization structure across cosmic time.

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It's no secret that the Universe and the objects present within it, as we see them all today, have changed over time as the Universe has grown up over the past 13.8 billion years. Galaxies are larger, more massive, more evolved, and are richer in stars but fewer in number than they were back in the early stages of cosmic history. By looking farther and farther away, we can see the Universe as it was at earlier times, but we're going to be limited in many ways: by how deep our telescopes can see, by what wavelengths they're capable of seeing, and by what small fraction of the sky they're capable of observing.

That's why an observing program like COSMOS-Web, the largest, widest-field JWST observing program to date, is so important. It isn't just revealing galaxies as they are nearby (at late times), at a variety of intermediate distances (and earlier times), and at ultra-large distances (and the earliest times of all), but due to its wide-field nature, is revealing galaxy types of varying abundances: the common-type galaxies, galaxies that are representative of more uncommon varieties, and even significant numbers of rare galaxies. And it's this aspect of galaxy evolution that makes me so proud and lucky to welcome Dr. Olivia Cooper to the podcast.

Olivia is a recently-minted PhD who works as part of the COSMOS-Web team, specializing in galaxy evolution and using JWST data — along with data from other world-class observatories — to investigate how the galaxies in our Universe grew up, and what that can teach us about our own cosmic past. It truly is a banger of an episode that you'll want to listen to every minute of, so tune in and dive deep into the depths of the distant Universe on our latest adventure of the Starts With A Bang podcast!

(This image shows a tiny sliver of the COSMOS-Web survey, with galaxies at a variety of distances along with a portion of a rich cluster of galaxies, at right, of this image. Credit: ESA/Webb, NASA & CSA, G. Gozaliasl, A. Koekemoer, M. Franco, and the COSMOS-Web team)