The evolution of the red giant clump and the structure of the Small Magellanic Cloud

Extract

The evolution of the red giant clump as a function of age has been investigated by analyzing the color-magnitude diagrams of a number of intermediate-age star clusters in the LMC. We find that the luminosity of the clump decreases systematically until about 1 Gyr. Thereafter, the mean apparent magnitude of the clump in LMC clusters remains constant at V ~ 19.0 ±0.1, although with significant scatter about this value in clusters with ages between 1 and 2 Gyr. The luminosity width of the clump also varies systematically with cluster age, being largest for clusters with ages near 1-1.5 Gyr. For six clusters older than 2 Gyr, the clump shows an intrinsic luminosity spread (defined as the FWHM of the best-fitting Gaussian) of 0.30 ± 0.07 mag. The systematic behavior of the color of the clump as a function of age was studied in detail by Hatzidimitriou (1991, M. N. R. A. S., 251, 545).