Speaker:  Yutaka Fujita (Osaka University)
Title:  Fundamental Plane and Scaling relations of Galaxy Clusters
Date and Time:  Wednesday, 30 October, 17:00-
Place:  KMI Science Symposia (ES635)

Abstract: According to the standard cold dark matter (CDM) cosmology, the structure of dark halos including those of galaxy clusters reflects their mass accretion history. Older clusters tend to be more concentrated than younger clusters. Their structure, represented by the characteristic radius rs and mass Ms of the Navarro-Frenk-White (NFW) density profile, is related to their formation time. In this study, we showed that rs, Ms, and the X-ray temperature of the intracluster medium (ICM), TX, form a thin plane in the space of (logrs,logMs,logTX). We show that the plane can be explained by a similarity solution by Bertschinger (1985), which indicates that clusters have not achieved virial equilibrium and they are continuously growing through matter accretion from their outer environments. As an application of the “fundamental plane”, I would like to discuss scaling relations of clusters. For example, the conventional self-similar model of galaxy cluster formation predicts that the X-ray luminosity-temperature (LX-TX) relation of galaxy clusters should have been LX \propto TX^2 in absence of the baryonic physics. However, we show that the actual baseline relation should be LX \propto TX^1.7 using the plane. The confirmation of the shallow slope could be a proof of hierarchical clustering. XRISM will reveal the gas motion in clusters and will prove their growth explicitly.