The quest to find the limits of galaxies with Euclid, HST and beyond

by Fernando Buitrago (Universidad de Valladolid, Spain)

Friday Feb 28, 2025, 10:00 AM → 11:30 AM Europe/Madrid

00.303.0 - Aula 13 (Facultad de Ciencias Físicas)

Low Surface Brightness (LSB) images, especially those from the ESA's Euclid space telescope, promise to deliver an unprecedented view of one third of the sky with HST-like spatial resolution. This fact will allow us to have a privileged view not only of dwarf galaxies but also the massive ones. One of the concepts that will be forever changed is the galaxy size, one of the few direct galaxy observables that is related with the continuous galaxy mass assembly. We will explain how dark matter has an impact into the sizes that we determine with baryonic matter, highlighting the difference between traditional indicators (effective radii) and the relevance of utilizing a physically-motivated proxy i.e. the so-called galaxy edges aka truncations. We will also describe our previous results on the evolution of these LSB features at 0 < z < 1 (Buitrago et al. 2024). Our conclusion is that Milky Way-like galaxies decrease their sizes by a factor of 2 up to z = 1, a more dramatic size evolution --that could be parametrized as (1+z)^-1-- than the one derived by using effective radii. The core of our presentation will show the synergy that we are conducting for joining together computer scientists and astronomers to derive galaxy sizes with human-like accuracy applying Machine Learning techniques (Fernandez-Iglesias et al. 2024, Vega-Ferrero et al. 2025), firstly for millions of galaxies in Euclid and later for any dataset/survey with minimum effort via Domain Adaptation. We will end up by showing our predictions for JWST and ARRAKIHS, and discussing their profound implications.