The Giant, Horizontal, and Asymptotic Branches of Galactic Globular Clusters. I. The Catalog, Photometric Observables, and Features

Abstract

A catalog including a set of the most recent Color Magnitude Diagrams (CMDs)\nis presented for a sample of 61 Galactic Globular Clusters (GGCs). We used this\ndata-base to perform an homogeneous systematic analysis of the evolved\nsequences (namely, Red Giant Branch (RGB), Horizontal Branch (HB) and\nAsymptotic Giant Branch (AGB)). Based on this analysis, we present: (1) a new\nprocedure to measure the level of the ZAHB (V_ZAHB) and an homogeneous set of\ndistance moduli obtained adopting the HB as standard candle; (2) an independent\nestimate for RGB metallicity indicators and new calibrations of these\nparameters in terms of both spectroscopic ([Fe/H]_CG97) and global metallicity\n([M/H], including also the alpha-elements enhancement). The set of equations\npresented can be used to simultaneously derive a photometric estimate of the\nmetal abundance and the reddening from the morphology and the location of the\nRGB in the (V,B-V)-CMD. (3) the location of the RGB-Bump (in 47 GGCs) and the\nAGB-Bump (in 9 GGCs). The dependence of these features on the metallicity is\ndiscussed. We find that by using the latest theoretical models and the new\nmetallicity scales the earlier discrepancy between theory and observations\n(~0.4 mag) completely disappears.\n