Year: 2013
Type: article
Abstract: We present a new framework for modelling discrete kinematic data. Current techniques typically involve binning. Our approach works directly with the discrete data and uses maximum-likelihood methods to assess the probability of the data set given model predictions. We avoid making hard cuts on the data sets by allowing for a contaminating population in our models. We apply our models to discrete proper motion and line-of-sight velocity data of Galactic globular cluster ω Centauri and find a mildly radial velocity anisotropy β = 0.10 ± 0.02, an inclination angle i = 50° ± 1°, a V-band mass-to-light ratio |$\Upsilon = 2.71 \pm 0.05 \; \rm M_{\odot }/ \rm L_{\odot }$| and a distance d = 4.59 ± 0.08 kpc. All parameters are in agreement with previous studies, demonstrating the feasibility of our methods. We find that the models return lower distances and higher mass-to-light ratios than expected when we include proper motion stars with high errors or for which there is some blending. We believe this not a fault of our models but is instead due to underestimates or missing systematic uncertainties in the provided errors.
Institutions: Max Planck Institute for Astronomy, University of Utah
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1485008513