Kinematics of the circumgalactic medium in early-type galaxies

A fundamental role in galaxy formation and evolution is played by the CircumGalactic Medium (CGM), a very diffuse and ionized multiphase gas that constitutes the interface between galaxies and the intergalactic medium (IGM). In this thesis, we focus on the cold ionized phase, with the aim to understand its kinematics and physical state, in particular for early-type galaxies. Our goal is to reproduce, using kinematic models, the two main constraints given by the COS-Halos observations: the velocity dispersion and the hydrogen column density. We create a wide variety of models, with very different assumptions, and we investigate the equilibrium and the non-equilibrium state of the absorbers. First, we study the physical state of the cold clouds and we find that they cannot survive in the internal regions of the halos, where the interactions with the hot dense coronal gas would likely destroy them. These interactions are instead weak in the outer regions, where the hot gas is more diffuse, and the clouds have a nearly ballistic motion. We describe then the kinematics of the clouds with collisionless equilibrium models, solving the Jeans equation with very different assumptions for the cloud density distribution and the radial velocity dispersion profile, exploring various parametrizations. We find that we can reproduce both the observational constraints only if the clouds are confined to the external regions of the halos by tangentially biased orbits, in agreement with our findings for the cloud survival. Finally, we investigate models that describe a global inflow of the CGM clouds towards the galaxy, assuming that they are accreted from the IGM or created at large radii by the condensation of the hot corona due to thermal instabilities. We find successfull models with clouds coming from the IGM, slowed down by the drag force acted by the corona and disrupted by the hydrodynamical interaction with the hot gas at a given internal radius.