A New Color-Magnitude Diagram for Palomar 11

We present new photometry for the Galactic thick disk globular clusterPalomar 11 extending well past the main sequence turn-off in the V and I bands.This photometry shows noticeable red giant and subgiant branches. Thedifference in magnitude between the red horizontal branch (red clump) and thesubgiant branch is used to determine that Palomar 11 has an age of 10.4+/-0.5Gyr. The red clump is used to derive a distance d_\sun=14.3+/-0.4 kpc, and amean cluster reddening of E(V-I)=0.40+/-0.03. There is differential reddeningacross the cluster, of order \delta E(V-I)~0.07. The colour magnitude diagramof Palomar 11 is virtually identically to that of the thick disk globularcluster NGC 5927, implying that these two clusters have a similar age andmetallicity. Palomar 11 has a slightly redder red giant branch than 47 Tuc,implying that Palomar 11 is 0.15 dex more metal-rich, or 1 Gyr older than 47Tuc. Ca II triplet observations (Rutledge et al. 1997) favour the hypothesisthat Palomar 11 is the same age as 47 Tuc, but slightly more metal-rich.Comment: to appear in AJ (19 pages, 4 B&W figures, 1 colour figure