THE AGE CALIBRATION OF INTEGRATED ULTRAVIOLET COLORS AND YOUNG STELLAR CLUSTERS IN THE LARGE MAGELLANIC CLOUD

Integrated colors in selected far-UV bands are presented for a large sample of Large Magellanic Cloud (LMC) clusters. Theoretical calculations of these integrated colors are derived and discussed. We show that the location in the two-color diagram C(18-8), C(15-31) is expected to be a sensitive but smooth function of cluster age for ages in the range 5 × 106 to 8 × 108 yr. Theoretical results appear in very good agreement with the observed colors of LMC clusters. From this comparison, we suggest that the gap in the observed colors is caused by the lack of LMC clusters in the range of ages between 2 × 108 to 109 yr. The two-color location of old globulars is finally discussed, also in connection with available data for the M31 clusters.