Some integrated properties of galactic globular clusters

The luminosities of globular clusters are found to correlate with their half-light radii. The most luminous clusters have radii r(h) similar to 3 pc. Mean cluster luminosities are [M(v)]=-6.64+/-0.26 for r(h)<2.0, [M(v)]=-7.44+/-0.20 for 2.0 less than or equal to r(h)<4.0 pc, and [M(v)]=-6.57+/-0.21 for clusters with r(h) greater than or equal to 4.0 pc. An even fainter value [M(v)]=-5.85+/-0.36 is found for large clusters with r(h) greater than or equal to 8.0 pc. These results possibly weaken confidence in the conclusion that the peak of the globular cluster luminosity distribution is a universal standard candle. In the outer Galactic halo, globular clusters with red horizontal branches are fainter by about a factor of ten than are clusters with blue and intermediate color horizontal branches. Among clusters with R(GC)>10 kpc there appears to be a clear dichotomy between normal clusters (which all have [Fe/H]<-1.2) and the anomalous relatively metal-rich clusters Pal 1, Pal 12, and Ter 7, which are both unusually faint (M(v)>-5) and relatively metal-rich ([Fe/H]>-1.0). This suggests that these relatively metal-rich halo clusters may have had an unusual evolutionary history. (C) 1996 American Astronomical Society.