FORNAX GLOBULAR-CLUSTER-1 AND GLOBULAR-CLUSTER-5 - A CONFIRMED EXTRAGALACTIC SECOND PARAMETER PAIR

We report new color-magnitude diagrams for Fornax globular clusters 1 and 5 where our data reaches V=24, below the horizontal branch. Using the index B-R/(B+V+R), a measure of the horizontal branch color, we fi nd cluster 1 has a red (-0.50+/-0.10) and cluster 5 an intermediate co lor (-0.09+/-0.12) horizontal branch confirming the first extragalacti c second parameter pair. The HE types are markedly redder than the Gal actic globular clusters at [Fe/H]=-2. In globular cluster 1, we find 2 1 possible variable stars out of 41 horizontal branch stars. Cluster 1 has an anomalously low ratio of horizontal branch to red giant stars, which formally gives a helium abundance of 0.16<Y<0.22, depending on the assumptions used. For both clusters 1 and 5, and for the red horiz ontal branch in the field adjacent to cluster 5, V-HB=21.25+/-0.05. We give calibrated surface brightness profiles and measure new core and tidal radii for cluster 1 of 17.6'' and 104'' and for cluster 5 of <2' ' and 91'', respectively. (C) 1996 American Astronomical Society.