Ricerc@Sapienza

The existence of Dark Matter (DM) in the Universe is inferred indirectly by its gravitational effect. Several observations of the motions of stars and gas in galaxies, cluster galaxy radial velocities, hot gas properties inside clusters of galaxies, and gravitational lensing of distant galaxies by foreground galaxy clusters suggest the presence of large amounts of DM. Currently we know that DM makes up 23% of the total mass-energy density of the Universe.
Among the different targets to trace and to infer the presence of DM, in this Project we focus on 1) clusters of galaxies, giving us some of the strongest clues as to the nature of this component of the Universe and 2) gravitational lensing and cosmic shear tomography, the most promising tools to both investigate the nature of DM and dark energy.
The observed radial velocities of cluster galaxies suggest dynamically based cluster masses that are factors of 10, or even more, higher than that deduced by adding up the observed cluster mass (stars, IntraCluster Medium (ICM) and dust) content. Similar inference derives from gravitational lensing approach.
In this Project we plan to deeply study the amount and radial distribution of DM inside clusters of galaxies. Indeed, the clusters total mass can be inferred by different observables and with different methods. The importance of this study is because inaccurate cluster masses could induce biased cosmological results, see as an example by possible wrong cluster number counts. Multi-probe observations of clusters (by X-ray emission, in optical bands and by Sunyaev-Zel¿dovich (SZ) effect) are useful to calibrate the mass budget and to better tuning the mass bias existing between the total mass (unknown) and the mass inferred by X-ray or SZ observations under the assumption of ICM satisfying hydrostatic equilibrium in the gravitational potential well.
This is among the hot topics of current cosmological studies.