SIMBAD references

2000AJ....119..197R - Astron. J., 119, 197-206 (2000/January-0)

Two groups of nearly coeval star clusters in the Small Magellanic Cloud.


Abstract (from CDS):

We report new photometry and main-sequence turnoff ages for seven populous star clusters in the SMC with MV←6 and age greater than 1 Gyr, using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. In contrast to the accepted picture, these clusters appear to have formed in two brief intervals, the oldest 8±2 Gyr ago and one during a more recent burst 2±0.5 Gyr ago. When the ridgelines of the four clusters (NGC 339, 361, and 416 and Kron 3) in the 8 Gyr burst are aligned, the dispersion in turnoff luminosities is less than 0.2 mag, corresponding to a maximum age spread of ±0.7 Gyr. When the ridgelines of three clusters (NGC 152, 411, and 419) in the 2 Gyr burst are aligned, the maximum dispersion of 0.2 mag in turnoff luminosity corresponds to a permitted age spread of ±0.2 Gyr. Within each group of clusters, the entire cluster loci (including red giant branches and clumps) are nearly identical, consistent with a very small spread in metallicity and age. In contrast to the wide dispersion in ages previously reported in the literature, our sample with more precise photometry and age measurements supports a burst-punctuated rather than a continuous cluster formation history for the oldest SMC clusters.

Abstract Copyright:

Journal keyword(s): Galaxies: Evolution - Galaxies: Star Clusters - Galaxies: Magellanic Clouds

Simbad objects: 15

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