Formation and Growth of Cosmic Giants: Lensing View of Galaxy Cluster Halos
Keiichi Umetsu1*
1Institute of Astronomy and Astrophysics, Academia SInica, Taipei, Taiwan
* Presenter:Keiichi Umetsu,
I will talk about the discovery of a universal scaling relation governing the evolution of massive dark-matter halos (Fujita, Umetsu, Rasia, Meneghetti, Donahue et al.), based on our gravitational lensing and X-ray observations of high-mass galaxy clusters from the CLASH survey. We show that the observational data of high-mass clusters lie on a plane in the three-dimensional logarithmic space of their characteristic halo radius "rs", mass "Ms" , and X-ray temperature "Tx" with a very small orthogonal scatter. In the context of the standard LCDM cosmology, the tight correlation indicates that the gas temperature was determined at a specific cluster formation time, which is encoded in (rs,Ms), and that the gas was heated when the clusters were in the fast-growing phase. Intriguingly, the plane is significantly tilted with respect to the canonical virial expectation, Tx ∝ Ms /rs. We show that the self-similar solution of Bertschinger (1985) for secondary infall and accretion can explain the observed relation, Tx ∝ Ms^1.5 /rs^2. Numerical simulations reproduce the observed plane and its angle. This result holds independently of the gas physics implemented in the code, revealing the fundamental origin of this plane.

Keywords: Observational Cosmology, Clusters of Galaxies, Gravitational Lensing, Dark Matter, Structure Formation in the Universe