ANCIENT STARS BEYOND THE LOCAL GROUP: RR LYRAE VARIABLES AND BLUE HORIZONTAL BRANCH STARS IN SCULPTOR GROUP DWARF GALAXIES

Journal Article · Sun Jan 10 00:00:00 EST 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/708/2/L121; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21301408

Da Costa, G S; Jerjen, H ^[1]; Rejkuba, M ^[2]; Grebel, E K ^[3]

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1. Research School of Astronomy and Astrophysics, The Australian National University, Mt Stromlo Observatory, via Cotter Rd, Weston, ACT 2611 (Australia)
2. European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen (Germany)
3. Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany)

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.

• OSTI ID: 21301408
• Journal Information: Astrophysical Journal Letters, Vol. 708, Issue 2; Other Information: DOI: 10.1088/2041-8205/708/2/L121; Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
CAMERAS
COLOR
DENSITY
GALAXIES
IMAGES
STARS
TELESCOPES