THE FUNDAMENTAL PLANE CORRELATIONS FOR GLOBULAR-CLUSTERS

In the parameter space whose axes include a radius (core, or half-ligh t), a surface brightness (central, or average within the half-light ra dius), and the central projected velocity dispersion, globular cluster s lie on a two-dimensional surface (a plane, if the logarithmic quanti ties are used). This is analogous to the ''fundamental plane'' of elli ptical galaxies. The implied bivariate correlations are the best now k nown for globular clusters. The derived scaling laws for the core prop erties imply that cluster cores are fully virialized, homologous syste ms, with a constant (M/L) ratio. The corresponding scaling laws on the half-light scale are different, but are nearly identical to those der ived from the ''fundamental plane'' of ellipticals. This may be due to the range of cluster concentrations, which are correlated with other parameters. A similar explanation for elliptical galaxies may be viabl e. These correlations provide new empirical constraints for models of globular cluster formation and evolution, and may also be usable as ro ugh distance-indicator relations for globular clusters.