Photometry of Globular Cluster NGC 5466

Previous abstract Next abstract

Session 104 -- Globilar Clusters
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

[104.10] Photometry of Globular Cluster NGC 5466

Kent A. Montgomery (Boston University), James N. Heasley (Institute for Astronomy, University of Hawaii), Kenneth A. Janes (Boston University)

We present photometry of the metal poor globular cluster NGC 5466 and compare it with M92 a cluster of almost identical metallicity. The photometry was obtained using the 3.6 meter Canada France Hawaii telescope, the University of Hawaii 2.2 meter, and the Kitt Peak 0.9 meter. For both the UH and KPNO photometry we used a 2048x2048 CCD allowing the the entire cluster to be imaged within a single frame. The CFHT was equipped with a 1024x1024 CCD hence only a portion of the cluster was imaged. The photometry from the 3 sets was combined to produce a color-magnitude diagram which extends from the tip of the red giant branch at a V magnitude of 13.5 to the main sequence 3.5 magnitudes below the turnoff at 23rd magnitude. NGC 5466 and M92 are both essentially unreddened: the former has [Fe/H]=-2.22 and the latter [Fe/H]=-2.24 (Zinn, 1985, ApJ, 293, 424). However, these two clusters exhibit different horizontal branch types and thus can be used to probe the hypothesis that age is the second parameter affecting horizontal branch type. A direct comparison between the two cluster ridgelines is used to determine the relative ages of the two clusters. In addition, the distributions of stars both on the red giant and horizontal branches is compared in order to investigate differences in cluster parameters such as helium abundance.

Thursday program listing