New constraints on the central mass contents of Omega Centauri from combined stellar kinematics and pulsar timing

Abstract

We perform a combined analysis of stellar kinematics and line-of-sight accelerations of millisecond pulsars to investigate the mass contents of Omega Centauri. We consider multiple mass components: the visible photometric distribution, a central cluster of dark remnants, an intermediate-mass black hole, and a distribution of intermediate extension traced by the pulsars. By self-consistently incorporating multiple independent datasets, including the effects of different centers, we obtain significant constraints on these mass distributions. Our results strongly favor an extended central mass of ~ 2 - 3 x 10^5 Msun, emulating a cluster of heavy stellar remnants, over an IMBH, with a 3-sigma upper limit of 6 x 10^3 Msun on its mass. Pulsar timing observations provide significant constraints, favoring a central mass distribution that is ~ 20% more massive and extended. Notably, we observe a clear linear scaling between the pulsar distribution and stellar encounter rates, showing excellent agreement with the expectation from millisecond pulsar formation models and motivating a profile for their distribution, providing the first validation of its kind where positions are linked to their place of formation in globular clusters. Our findings highlight the effectiveness of this novel methodology in exploring the structure of star clusters, setting a promising precedent amid the advent of the rapidly growing number of observations and discoveries currently being experienced in this field.