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Session 79 - Star Clusters in Other Galaxies.
Display session, Friday, January 09
Exhibit Hall,

[79.08] WFPC2 Observations of the Small Magellanic Cloud Intermediate-Age Populous Cluster NGC 416

R. S. French (Middle Tennessee State U.), K. J. Mighell (NOAO/KPNO), A. Sarajedini (San Francisco State U.)

We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 observations in F555W (\simV) and F450W (\simB) of the intermediate-age populous star cluster NGC 416 in the Small Magellanic Cloud galaxy. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence of these three star clusters. We determined the following ratios of age_\rmNGC416/age_\rmL1\simeq0.73\pm0.05 and age_\rmL113/age_\rmL1\simeq0.52\pm0.09. These age ratios provide absolute age estimates of 6.6\pm0.5 Gyr and 4.7\pm0.8 Gyr for NGC 416 and Lindsay 113, respectively, assuming that Lindsay 1 is 9 Gyr old. Metallicities of [Fe/H]=-1.44\pm0.12, -1.35\pm0.08, -1.24\pm0.11 dex, and reddenings of E(\bv)=0.08\pm0.03, 0.06\pm0.02, 0.00\pm0.02 mag for NGC 416, Lindsay 1, and Lindsay 113, respectively, were determined simultaneously using the method of Sarajedini amp; Layden [AJ, 113, 264 (1997)]. The determination of accurate (relative) ages for the intermediate-age populous clusters in the Small Magellanic Cloud (e.g. via deep main sequence photometry) would allow the d_(B-V) method of Sarajedini, Lee, amp; Lee [ApJ, 450, 712 (1995)] to be extended to ages significantly younger than 7 Gyr. The extended d_(B-V) method could prove to be a very useful age diagnostic for future studies of the intermediate-age metal-poor stellar populations in nearby Local Group galaxies where accurate main-sequence turnoff photometry at M_V\simeq+4 mag is currently not possible or practical.

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