SOME INTEGRATED PROPERTIES OF GALACTIC GLOBULAR-CLUSTERS

The luminosities of globular clusters are found to correlate with thei r 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 cl usters with r(h) greater than or equal to 8.0 pc. These results possib ly weaken confidence in the conclusion that the peak of the globular c luster luminosity distribution is a universal standard candle. In the outer Galactic halo, globular clusters with red horizontal branches ar e fainter by about a factor of ten than are clusters with blue and int ermediate color horizontal branches. Among clusters with R(GC)>10 kpc there appears to be a clear dichotomy between normal clusters (which a ll 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 relativ ely metal-rich halo clusters may have had an unusual evolutionary hist ory. (C) 1996 American Astronomical Society.