The Relation between Near-infrared Luminosity of Red Giant Branch Bumps and Metallicity of Galactic Globular Clusters

Using photometric data from the 2MASS second incremental release point sourcecatalog we constructed Ks vs. (J-Ks) color-magnitude diagrams (CMDs) ofGalactic globular clusters (GGCs) for which the JKs photometric data have beenmade available up to now. On the CMDs of 13 GGCs we identified RGB bumpfeatures and derived luminosities of bumps in Ks and in absolute Ks for 11 ofthem. We reconfirm the relation between abolute Ks magnitude of bump andmetallicity [Fe/H]CG97 or [M/H] such that the luminosity of bump becomesbrighter as metallicity [Fe/H]CG97 or [M/H] decreases. This result is similarto that obtained by Ferraro et al. (1999) for the relation between abolute Vmagnitude of bump and [M/H] based on observations of 47 GGCs which wereconducted in the optical region (V vs. (B-V) CMDs). Our results show the sametrend as those found by Ferraro et al. (2000) for the relations between aboluteKs magnitude of bump and metallicity [Fe/H]CG97 and [M/H] derived fromobservations of 8 GGCs in the same near-infrared (K vs. (J-K) CMDs). Combiningwith the data of Ferraro et al. (2000), we derive a robust relation for themetal-dependent luminosities of the bumps.Comment: 20 pages with 6 figures, submitted to AJ, 5 pages including 1 figure added, revised according to referee's comment