Revisiting the Mass of the Coma Cluster from X-ray Observations

I re-examine mass estimates of the Coma cluster from pre-ASCA X-ray spectral observations. A large range of model dark matter distributions are examined, under the assumptions of hydrostatic equilibrium and spherical symmetry, to determine the widest possible allowed range on the total mass of the cluster. Within a radius of 1 Mpc, the total cluster mass is tightly constrained to be (6.2 ± 0.9) × 10 M⊙ and the ratio of luminous baryonic matter to total matter lies between 13% and 17%. Within a radius of 3 Mpc the total mass is (1.3 ± 0.5) × 10 M⊙ and the luminous matter fraction is 20%-40%. I find that the “universal” dark matter density profile proposed by Navarro, Frenk, and White, based on N-body simulations of a standard cold-dark-matter dominated Universe, predicts a steep temperature gradient within the core of the cluster that is a poor fit to the Coma data and can be rejected at greater than 99% confidence.