期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 708, 期 2, 页码 L121-L125出版社
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/708/2/L121
关键词
galaxies: dwarf; galaxies: individual (ESO 294-010, ESO 410-005); galaxies: stellar content; stars: horizontal-branch; stars: variables: other
资金
- ESO DGDF
- Australian National University
We have used Hubble Space Telescope Advanced Camera for Surveys images to generate color-magnitude diagrams that reach below the magnitude of the horizontal branch in the Sculptor Group dwarf galaxies ESO294-010 and ESO410-005. In both diagrams, blue horizontal branch stars are unambiguously present, a signature of the existence of an ancient stellar population whose age is comparable to that of the Galactic halo globular clusters. The result is reinforced by the discovery of numerous RR Lyrae variables in both galaxies. The occurrence of these stars is the first direct confirmation of the existence of ancient stellar populations beyond the Local Group and indicates that star formation can occur at the earliest epochs even in low-density environments.
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