Daniele Sorini - January 20, 2017

Probing CGM and IGM with Lyman-alpha Absorption

Galactic winds driven by supernovae and Active Galactic Nuclei alter the
physical state of gas in the circumgalactic and intergalactic media (CGM
and IGM), although the details of these processes are still poorly
understood.  The study of the statistics of the Lyman-alpha absorption
lines in the spectra of background (b/g) quasars passing at small impact
parameter from foreground (f/g) galaxies has the potential to provide
insight on these processes, constraining the thermal state of CGM and IGM.
I will provide a comparison between observations of Lyman-alpha absorption
both at small and large impact parameters from the f/g object, and the
predictions given by Illustris and Nyx simulations. The simulations do not
produce enough Lyman-alpha absorption, failing at reproducing the data at
small scales. I will show that this discrepancy may be indicative for the
presence of cooler gas in the CGM.