Deep near-IR photometry of eight metal-poor globular clusters in the Galactic bulge and halo

¹ Department of Astronomy, Institute of Earth Atmosphere Astronomy, Yonsei University, Seoul 120-749, Korea e-mail: sohnyj@yonsei.ac.kr; kjw0704@galaxy.yonsei.ac.kr
² Center for Space Astrophysics, Yonsei University, Seoul 120-749, Korea
³ Korea Astronomy and Space Science Institute, Daejeon 305-348, Korea

Received: 11 February 2006
Accepted: 25 July 2006

Abstract

High quality J, H and K' images are used to investigate the morphological properties of the near-infrared color-magnitude diagrams for five metal-poor bulge globular clusters and three halo clusters. Photometric parameters to describe the RGB shape, i.e., the colors at fixed magnitudes of and , the magnitudes at fixed colors of , and the RGB slope, have been measured from the fiducial normal points of the CMDs. We also measured the near-infrared magnitudes of the RGB bump and tip on the luminosity function of the RGB stars for each cluster. The RGB parameters of the observed metal-poor bulge and halo clusters are consistent with the previous empirical relationships between the RGB parameters and the cluster metallicity for metal-rich bulge clusters and halo clusters. The near-infrared magnitudes of the RGB bump and tip are in good agreement with the theoretical prediction of the Yonsei-Yale isochrone.