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Paper: The Star Formation History and Stellar Population Structures in the Sextans Dwarf Spheroidal Galaxy
Volume: 399, Panoramic Views of Galaxy Formation and Evolution
Page: 469
Authors: Okamoto, S.; Arimoto, N.; Yamada, Y.; Onodera, M.; Tolstoy, E.; Irwin, M.; Helmi, A.; Battaglia, G.; Jablonka, P.; Hill, V.; Venn, K.; Shetrone, M.; Letarte, B.; Primas, F.; Francois, P.; Sadakane, K.; Kaufer, A.; Szeifert, T.; Abel, T.
Abstract: We present V, I CCD photometry of the Sextans dwarf spheroidal galaxy (dSph) in the Local Group. Images of the galaxy were taken by Suprime-Cam on Subaru, covering 26 fields extended to the tidal radius. The colormagnitude diagrams extending two magnitudes below the main-sequence turnoff (MSTO) show a steep red giant branch (RGB), blue and red horizontal branch (HB), blue stragglers, and main-sequence (MS) stars. From the luminosity difference between the HB and the MSTO, we estimate the ages of the galaxy’s stellar populations. We find that the relatively younger stars (∼10Gyr) are more spatially concentrated toward the galaxy center than old stars (∼14Gyr), which indicates that the star formation in the central region continued at least a few Gyr. This is consistent with the different spatial distributions of red and blue HB stars. The long duration of the star-formation period in the central region of the galaxy is possibly related to dissipative gas physics during the epoch of post-reionization evolution, or to the accretion history of satellites.
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