Discrete dynamical models of omega Centauri

作者：Watkins Laura L^*; van de Ven Glenn; den Brok Mark; van den Bosch Remco C E

来源：Monthly Notices of the Royal Astronomical Society, 2013, 436(3): 2598-2615.

DOI：10.1093/mnras/stt1756

• methods: statistical
• stars: kinematics and dynamics
• globular clusters: individual: omega Centauri (NGC 5139)

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 omega Centauri and find a mildly radial velocity anisotropy beta = 0.10 +/- 0.02, an inclination angle i = 50 degrees +/- 1 degrees, a V-band mass-to-light ratio gamma = 2.71 +/- 0.05 M-circle dot/L-circle dot 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.

• 出版日期2013-12