The Age-dependent Luminosities of the Red Giant Branch Bump, Asymptotic Giant Branch Bump, and Horizontal Branch Red Clump
- Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)
- San Francisco State University, San Francisco, CA 94132 (United States)
Color-magnitude diagrams of globular clusters usually exhibit a prominent horizontal branch (HB) and may also show features such as the red giant branch (RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory predicts that the luminosities of these features will depend on the metallicity and {ital age} of the cluster. We calculate theoretical lines of 2{endash}12 Gyr constant age RGB bumps and AGB bumps in the {Delta}V{sup HB} {sub Bump}-[Fe/H] diagram, which shows the brightness difference between the bump and the HB as a function of metallicity. In order to test the predictions, we identify giant branch bumps in new {ital Hubble Space Telescope} color-magnitude diagrams for eight SMC clusters. First, we conclude that the SMC cluster bumps are RGB bumps. The data for clusters younger than {approximately}6 Gyr are in fair agreement with our predictions for the relative age-dependent luminosities of the HB and RGB bump. The {Delta}V{sup HB} {sub Bump} data for clusters older than {approximately}6 Gyr demonstrate a less satisfactory agreement with our calculations. We conclude that {approximately}6 Gyr is the lower bound to the age of clusters for which the Galactic globular cluster, age-independent {Delta}V{sup HB} {sub Bump}-[Fe/H] calibration is valid. Application of the {Delta}V{sup HB} {sub Bump}-[Fe/H] diagram to stellar population studies is discussed. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}
- OSTI ID:
- 340412
- Journal Information:
- Astrophysical Journal, Vol. 511, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
REVEALING PROBABLE UNIVERSAL FEATURES IN THE LOWER RED GIANT BRANCH LUMINOSITY FUNCTIONS OF GALACTIC GLOBULAR CLUSTERS
THE ASYMPTOTIC GIANT BRANCH AND THE TIP OF THE RED GIANT BRANCH AS PROBES OF STAR FORMATION HISTORY: THE NEARBY DWARF IRREGULAR GALAXY KKH 98