Tidal Effects and Globular Clusters.
Abstract
Numerical experiments were conducted to explore how a globular cluster is tidally limited by the galaxy. The results show that the observed tidal radius is close to that predicted by simple dynamical arguments. The tidal cutoff is primarily a function of energy, supporting the use of an energy cutoff of a Maxwellian to build cluster models. The time scale for tidal relaxation of the particle distribution in the outer cluster halo is on the order of 50 to 100 orbital periods. To compare the above results with reality, a large search identified 22 new members of the globular cluster Omega Centauri. All are located further than one half the tidal radius from the cluster center. Accurate radial velocities ((+OR) 1 km/sec) were obtained, and the run of velocity dispersion with radius determined. A single component, isotropic King model fits the observations very well. The central lineofsight velocity dispersion is 16.5 km/sec, the total mass of 2.8 x 10('6) M(,(CIRCLE)). Rotation is dynamically significant, reaching a peak amplitude of 7.7 km/sec at r = 6.5 arcminutes from the center, and falling to zero at the cluster boundary. Observed tidal radii of galactic globular clusters have been analyzed to estimate the distribution of orbital eccentricities. The majority of clusters are on orbits with e greater than 0.5. A correlation was found between e and {Fe/H}: the metal poorest clusters are on the least eccentric orbits.
 Publication:

Ph.D. Thesis
 Pub Date:
 1983
 Bibcode:
 1983PhDT........11S
 Keywords:

 Physics: Astronomy and Astrophysics;
 Galaxies;
 Globular Clusters;
 Tides;
 Mathematical Models;
 Particle Diffusion;
 Radial Velocity;
 Stellar Rotation;
 Astrophysics