Bachelor’s Thesis Project in Astronomy

The whereabouts of the missing baryons (15 hp)

A substantial fraction of the baryons (protons and neutrons) of the Universe remain unidentified at low redshifts. We know that these baryons must be hiding out there somewhere – but not exactly where or in what form. Simulations of galaxy formation indicate that most of these dark baryons should be hiding in the warm/hot intergalactic medium or in the form of hot gaseous halos of galaxies. While some observations lend support to this idea, other data point in an alternative directions, suggesting that some fraction of the baryons may be able to cool and collapse on subgalactic scales without being detected through standard tracers of neutral hydrogen, molecular gas or star formation. If dark baryons were to pile up on small scales, this could have a profound impact on our understanding of galaxy formation and the dark matter content of galaxies. Here, various observational results will be combined to constrain the redshift evolution of the dark baryons and to set upper limits on the fraction of the missing baryons that can plausibly be hiding on subgalactic scales.

Supervisor: Erik Zackrisson

Please contact Erik Zackrisson, ez(at)astro.su.se, for more information!