Red giant branch in near-infrared colour-magnitude diagrams - II. The luminosity of the bump and the tip

Abstract

We present new empirical calibrations of the red giant branch (RGB) bump and tip based on a homogeneous near-infrared data base of 24 Galactic globular clusters. The luminosities of the RGB bump and tip in the J, H and K bands and their dependence on the cluster metallicity have been studied, yielding empirical relationships. By using recent transformations between the observational and theoretical planes, we also derived similar calibrations in terms of bolometric luminosity. Direct comparisons between updated theoretical models and observations show an excellent agreement. The empirical calibration of the RGB tip luminosity in the near-infrared passbands presented here is a fundamental tool to derive distances to galaxies far beyond the Local Group, in view of using the new ground-based adaptive optics facilities and, in the near future, the James Webb Space Telescope.