Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-05-18
Astrophys.J.520:L33,1999
Astronomy and Astrophysics
Astrophysics
15 pages, 4 figures, LaTeX, uses aastex. Accepted by ApJ Letters
Scientific paper
10.1086/312133
We present BV photometry of the Sculptor dwarf galaxy to V=22. These data give evidence for a bimodality in Sculptor's metallicity distribution based on a discontinuity in the luminosities of horizontal branch (HB) stars and by the presence of two distinct red giant branch (RGB) bumps. A consistent picture of the evolved stars in Sculptor is given by the presence of (1) a metal-poor population of [Fe/H] ~ -2.3 with an exclusively blue HB and that corresponds to the blueward side of the Sculptor RGB and the more luminous RGB bump, and (2) a less metal-poor population of [Fe/H] ~ -1.5 required to explain the less luminous red HB, the red side of the RGB, and a second, less luminous RGB bump. Best fits to the HB populations are obtained with enhanced oxygen abundances, [O/Fe] ~ +0.5. Variations in the global HB and RGB morphology of Sculptor can be explained by differences in the radial distribution of these two populations. The presence of these two populations shows that the Sculptor dwarf galaxy has an internal second parameter problem.
Majewski Steven R.
Patterson Richard J.
Rood Robert T.
Siegel Michael Hiram
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