Cluster Mass Estimate and a Cusp of the Mass Density Distribution in Clusters of Galaxies

Abstract

We study density cusps in the center of clusters of galaxies to reconcile X-ray mass estimates with gravitational lensing masses. For various mass density models with cusps we compute X-ray surface brightness distribution, and fit them to observations to measure the range of parameters in the density models. The Einstein radii estimated from these density models are compared with Einstein radii derived from the observed arcs for Abell 2163, Abell 2218, and RX J1347.5-1145. The X-ray masses and lensing masses corresponding to these Einstein radii are also compared. While steeper cusps give smaller ratios of lensing mass to X-ray mass, the X-ray surface brightnesses estimated from flatter cusps are better fits to the observations. For Abell 2163 and Abell 2218, although the isothermal sphere with a finite core cannot produce giant arc images, a density model with a central cusp can produce a finite Einstein radius, which is smaller than the observed radii. We find that a total mass density profile which declines as $\sim r^{-1.4}$ produces the largest radius in models which are consistent with the X-ray surface brightness profile. As the result, the extremely large ratio of the lensing mass to the X-ray mass is improved from 2.2 to 1.4 for Abell 2163, and from 3 to 2.4 for Abell 2218. For RX J1347.5-1145, which is a cooling flow cluster, we cannot reduce the mass discrepancy.

23 pages, 10 figures, Latex, uses aasms4.sty, accepted for publication in ApJ, Part 1

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Cited by in corpus (11)

• Gravitational Lensing
• Why Do Only Some Galaxy Clusters Have Cool Cores?
• The Sensitivity of Harassment to Orbit: Mass Loss from Early-Type Dwarfs in Galaxy Clusters
• Gas density and X-ray surface brightness profiles of clusters of galaxies from dark matter halo potentials: beyond the isothermal beta model
• The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87
• Arc Statistics
• A combined analysis of cluster mass estimates from strong lensing, X-ray measurement and the universal density profile
• Strong lensing as a test for Conformal Weyl Gravity
• On the radial density profile of intracluster gas tracing the isothermal dark halo with a finite core
• Exploiting magnification bias in ultradeep submillimetre-wave surveys using ALMA
• The effect of a cusped matter distribution on the formation of brightest cluster members