Le 17 janvier 2020
De 10h30 à 12h00
Gabriele Pezzulli
ETH Zurich
Galaxy formation models rely on mechanisms to keep the majority of baryons outside of the main body of galaxies. Different scenarios, however, make different predictions about where these « galactic missing baryons » should be found: relatively close-by in the so-called circumgalactic medium (CGM), or very far away in the diffuse intergalactic medium (IGM). A powerful way to constrain different models is therefore to seek observational determinations of the CGM mass and baryon fraction, especially at high z, where most of feedback processes are expected to take place.
A wealth of information has now become available from direct mapping of the CGM of high-z galaxies in Ly-alpha emission. I will show how MUSE observations of Giant Ly-alpha nebulae around bright QSOs can be used to constrain the total baryon content of the CGM of massive haloes at z~3. Our current results indicate a substantial fraction of baryons to be retained within the virial radius of these haloes, possibly favouring maintenance modes of feedback over models that require a very high efficiency of ejective processes. I will conclude by discussing how remaining uncertainties can be alleviated by future observations and theoretical modelling.