We constrain the total mass distribution in the cluster A3571, combining spatially resolved ASCA temperature data with ROSAT imaging data with the assumption that the cluster is in hydrostatic equilibrium. The total mass within r500 (1.7 h Mpc) is M500 = 7.8 × 1014 h M☉ at 90% confidence, 1.1 times smaller than the isothermal estimate. The Navarro, Frenk, & White "universal profile" is a good description of the dark matter density distribution in A3571. The gas density profile is shallower than the dark matter profile, scaling as r-2.1 at large radii, leading to a monotonically increasing gas mass fraction with radius. Within r500 the gas mass fraction reaches a value of fgas = 0.19 h (90% confidence errors). Assuming that this value of fgas is a lower limit for the universal value of the baryon fraction, we estimate the 90% confidence upper limit of the cosmological matter density to be Ωm 0.4.
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