1999ApJ...527..545M

We present maps and radial profiles of the gas temperature in the nearby galaxy clusters A2199 and A496, which have the most accurate ASCA spectral data of all hot clusters. X-ray images, temperature maps, and the presence of moderate cooling flows indicate that these clusters are relaxed and therefore can provide reliable X-ray mass measurements under the assumption of hydrostatic equilibrium and thermal pressure support. The average cluster temperatures corrected for the presence of cooling flows are 4.8±0.2 and 4.7±0.2 keV (90% errors), respectively, which are 10% higher than the wide-beam single-temperature fits. Outside the central cooling-flow regions and within r~0.7 h^–1 Mpc covered by ASCA, the radial temperature profiles are similar to those of the majority of nearby relaxed clusters. They are accurately described by polytropic models with γ=1.17±0.07 for A2199 and γ=1.24^+0.08_–0.11 for A496. We use these polytropic models to derive accurate total mass profiles. Within r=0.5 h^–1 Mpc, which corresponds to a radius of overdensity 1000, r₁₀₀₀, for these clusters (estimated from our mass profiles), the total mass values are 1.45±0.15x10¹⁴ and 1.55±0.15x10¹⁴ h^–1 M_☉. These values are 10% lower than those obtained assuming constant temperature. On the other hand, the values inside a gas core radius (0.07-0.13 h^–1 Mpc) are a factor of ≳1.5 higher than the isothermal values. The gas mass fraction increases significantly with radius (by a factor of 3 between the X-ray core radius and r₁₀₀₀) and at r₁₀₀₀ reaches similar values of 0.057±0.005 and 0.056±0.006 h^–3/2 for the two clusters, respectively. Our measured total mass profiles within r₁₀₀₀ are remarkably well approximated by the Navarro, Frenk, & White ``universal'' profile. Since A2199 and A496 are typical relaxed clusters, the above findings should be relevant for most such systems. In particular, the observed similarity of the temperature profiles in nearby clusters appears to reflect the underlying ``universal'' dark matter profile. The upward revision of the mass values at small radii for the observed temperature profile compared with those derived assuming isothermality will resolve most of the discrepancy between the X-ray and strong lensing mass estimates.