Ultraviolet Colors as Age Indicators for LMC Clusters

Abstract

Empirical correlations are found between log ages (logτ) intrinsic ultraviolet colors C(18 - 31)_0_ and C(25 - 31)_0_ for 27 LMC clusters, where log τ is on the uniform age scale of Elson correlations as age indicators for LMC clusters and other stellar populations are discussed. The results are partially based on a new calibration of log τ vs the reddening-corrected S parameter of Elson and Fall (1985). The log τ estimates from UV colors are about as accurate as those using the S parameter. However, the decreased sensitivity of the UV colors to age for the bluest clusters gives little incentive to use these correlations in preference to the S parameter. The nature of this loss in sensitivity is briefly discussed. We have used our correlations to estimate the ages of two LMC clusters of unknown age (NGC 1968 and NGC 1974) and the nuclei of two nearby blue compact dwarf galaxies (NGC 1705 and NGC 5253). For the latter two objects optical- and ultraviolet-based age estimates are in good agreement.