Astrophys. J., 803, 29 (2015/April-2)
Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular cluster. II. Kinematic profiles and maps.
WATKINS L.L., VAN DER MAREL R.P., BELLINI A. and ANDERSON J.
Abstract (from CDS):
We present kinematical analyses of 22 Galactic globular clusters using the Hubble Space Telescope proper motion catalogs recently presented in Bellini et al. For most clusters, this is the first proper-motion study ever performed, and, for many, this is the most detailed kinematic study of any kind. We use cleaned samples of bright stars to determine binned velocity-dispersion and velocity-anisotropy radial profiles and two-dimensional velocity-dispersion spatial maps. Using these profiles, we search for correlations between cluster kinematics and structural properties. We find the following: (1) more centrally concentrated clusters have steeper radial velocity-dispersion profiles; (2) on average, at 1σ confidence in two dimensions, the photometric and kinematic centers of globular clusters agree to within ∼1", with a cluster-to-cluster rms of 4"(including observational uncertainties); (3) on average, the cores of globular clusters have isotropic velocity distributions to within 1% (σt/σr = 0.992± 0.0005), with a cluster-to-cluster rms of 2% (including observational uncertainties); (4) clusters generally have mildly radially anisotropic velocity distributions (σt/σr ≈ 0.8 - 1.0) near the half-mass-radius, with bigger deviations from isotropy for clusters with longer relaxation times; and (5) there is a relation between σminor/σmajor and ellipticity, such that the more flattened clusters in the sample tend to be more anisotropic, with σminor/σmajor ≈ 0.9 -1.0. Aside from these general results and correlations, the profiles and maps presented here can provide a basis for detailed dynamical modeling of individual globular clusters. Given the quality of the data, this is likely to provide new insights into a range of topics concerning globular cluster mass profiles, structure, and dynamics.
globular clusters: individual - proper motions - stars: kinematics and dynamics
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<Available at CDS (J/ApJ/803/29): table1.dat tablea1.dat>
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