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Deep wide-field imaging down to the oldest main sequence turn-offs in the Sculptor dwarf spheroidal galaxy


de Boer, TJL and Tolstoy, E and Saha, A and Olsen, K and Irwin, MJ and Battaglia, G and Hill, V and Shetrone, MD and Fiorentino, G and Cole, A, Deep wide-field imaging down to the oldest main sequence turn-offs in the Sculptor dwarf spheroidal galaxy, Astronomy and Astrophysics, 528, (Apr) Article A119. ISSN 0004-6361 (2011) [Refereed Article]

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Copyright EDP Sciences,

DOI: doi:10.1051/0004-6361/201016398


We present wide-field photometry of resolved stars in the nearby Sculptor dwarf spheroidal galaxy using CTIO/MOSAIC, going down to the oldest main sequence turn-off. The accurately flux calibrated wide field colour-magnitude diagrams can be used to constrain the ages of different stellar populations, and also their spatial distribution. The Sculptor dSph contains a predominantly ancient stellar population (>10 Gyr old) which can be easily resolved into individual stars. A galaxy dominated by an old population provides a clear view of ancient processes of galaxy formation unimpeded by overlying younger populations. By using spectroscopic metallicities of RGB stars in combination with our deep main sequence turn-off photometry we can constrain the ages of different stellar populations with particular accuracy. We find that the known metallicity gradient in Sculptor is well matched to an age gradient. This is the first time that this link with age has been directly quantified. This gradient has been previously observed as a variation in horizontal branch properties and is now confirmed to exist for main sequence turn-offs as well. It is likely the Sculptor dSph first formed an extended metal-poor population at the oldest times, and subsequent more metal-rich, younger stars were formed more towards the centre until the gas was depleted or lost roughly 7 Gyr ago. The fact that these clear radial gradients have been preserved up to the present day is consistent with the apparent lack of signs of recent tidal interactions.

Item Details

Item Type:Refereed Article
Keywords:galaxies: dwarf galaxies: evolution galaxies: stellar content Local Group Hertzsprung-Russell and C-M diagrams
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Cole, A (Associate Professor Andrew Cole)
ID Code:69721
Year Published:2011
Web of Science® Times Cited:37
Deposited By:Mathematics and Physics
Deposited On:2011-05-16
Last Modified:2017-11-06

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