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Disentangling the Stellar Populations of Fornax Dwarf Spheroidal

Published online by Cambridge University Press:  11 July 2011

M. Koleva ,
Ph. Prugniel ,
I. Vauglin ,
M. Cesetti ,
E.V. Held ,
M. Gullieuszik ,
L. Rizzi ,
G. Battaglia ,
A. Cole  and
G. Da Costa
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M. Cesetti*
Affiliation:
Department of Astronomy, University of Padova, Italy Osservatorio Astronomico di Padova – INAF, Padova, Italy
E.V. Held
Affiliation:
Osservatorio Astronomico di Padova – INAF, Padova, Italy
M. Gullieuszik
Affiliation:
Royal Observatory of Belgium, Brussels, Belgium
L. Rizzi
Affiliation:
Joint Astronomy Centre, Hilo, Hawaii, USA
G. Battaglia
Affiliation:
European Southern Observatory, Garching, Germany
A. Cole
Affiliation:
School of Mathematics and Physics, University of Tasmania, Hobart, Australia
G. Da Costa
Affiliation:
Research School of Astronomy and Astrophysics, Australian National University, Australia
M. Mateo
Affiliation:
Department of Astronomy, University of Michigan, Ann Arbor, MI, USA
E. Olszewski
Affiliation:
Steward Observatory, University of Arizona, Tucson, USA
E. Tolstoy
Affiliation:
Kapteyn Astronomical Institute, Groningen, The Netherlands
M. Walker
Affiliation:
Institute of Astronomy, University of Cambridge, UK
*
e-mail: mary.cesetti@unipd.it
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Abstract

We studied the stellar populations of Fornax dwarf spheroidal galaxy using HST/WFPC2 imaging of 7 galaxy fields. Our observations reach the oldest main-sequence turn-off, revealing distinct stars formation episodes and allowing us to address the evolution of this prototype dwarf spheroidal galaxy known to have experienced an extended history of star formation. From our HST data, spatial gradients in the stellar content of Fornax emerge with greater clarity. The outermost fields show only stars with ages between 7–12Gyr, while the intermediate region hosts a stellar population between 4–10Gyr, and stars younger of 2 Gyr are found in the innermost fields. A clearly visible gap in the subgiant branch points to bimodality in the main star formation episode. Our observations also indicate that the inner clump detected by Coleman et al. (2004) is characterized by the presence of young stars with age about 1.8 Gyr.

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 48: CRAL-2010 A Universe of Dwarf Galaxies , 2011 , pp. 69 - 70
Copyright
© EAS, EDP Sciences, 2011

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References

Battaglia, G., et al., 2006, A&A, 459, 423
Coleman, M., et al., 2004, AJ, 127, 832CrossRef
Dolphin, A.E., 2009, PASP, 121, 655CrossRef
Olszewski, E.W., Mateo, M., Harris, J., Walker, M.G., Coleman, M.G. & Da Costa, G.S., 2006, AJ, 131, 912CrossRef