Rui Marques-Chaves
Observatoire de Genève, Université de Genève, Switzerland

Abstract
UV-bright star-forming galaxies were long thought to be extremely rare at any epoch, including during the epoch of cosmic reionization (EoR, at 6 < z < 16). However, James Webb Space Telescope observations are dramatically changing this picture by revealing numerous UV-bright sources, even at redshifts as high as z~14, with volume densities exceeding model predictions for galaxy formation by orders of magnitude. The nature of these “monsters” remains mysterious, but they may fundamentally reshape our understanding of early massive galaxy formation and the sources responsible for reionization.
In this seminar, I will present recent observations, from UV to submm, of a new class of extremely UV-bright star-forming galaxies discovered at intermediate redshifts (z~3), which appear to share many of the physical properties expected for EoR UV-luminous galaxies. These sources exhibit young stellar populations with Very Massive Stars (Mstar>100Msun),  extremely high star formation efficiencies, and huge Lyman continuum leakage. With star formation rates of ~ 500-1000 Msun/yr occurring in remarkably compact regions (~200-500 pc), they closely resemble classical models of monolithic collapse, where most of the stellar mass forms within a very short period (<10 Myr). I will highlight some unique properties observed in these sources, including complex Lyman-alpha profiles, Lyman continuum emission, and extreme stellar populations.  Finally, I will discuss the broader implications of these rare, yet powerful systems for our understanding of galaxy formation and the role such galaxies may have played in cosmic reionization.

2025 May 28, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto