Stellar Kinematics of the Omega Centauri Globular Cluster

We combine proper motion data from Gaia EDR3 and HST with radial velocity data to study the stellar kinematics of the ωcen globular cluster. Using a steady-state, axisymmetric dynamical model, we measure the distribution of both the dark and luminous mass components. Assuming both exponential and NFW mass profiles, depending on the dataset, we measure an integrated mass of 104 − 106M within the ω-cen half-light radius for a dark component that is distinct from the luminous stellar component. Models with a non-luminous mass component are strongly statistically preferred relative to a stellar mass-only model. In comparison to the dark matter distributions around dwarf spheroidal galaxies, the ω-cen dark mass component is much more centrally concentrated. Interpreting the non-luminous mass distribution as particle dark matter, we use these results to obtain the J-factor, which sets the sensitivity to the annihilation cross section. For the datasets considered, the range of median J-factors is ∼ 1022 − 1024 GeV2 cm−5, which is larger than that obtained for any dwarf spheroidal galaxy.