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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2006

The DART imaging and CaT survey of the Fornax dwarf spheroidal galaxy

Résumé

Aims.As part of the DART project we have used the ESO/2.2m Wide Field Imager in conjunction with the VLT/FLAMES GIRAFFE spectrograph to study the detailed properties of the resolved stellar population of the Fornax dwarf spheroidal galaxy out to and beyond its tidal radius. Fornax dwarf spheroidal galaxy has had a complicated evolution and contains significant numbers of young, intermediate age and old stars. We investigate the relation between these different components by studying their photometric, kinematic and abundance distributions.
Methods: . We re-derived the structural parameters of the Fornax dwarf spheroidal using our wide field imaging covering the galaxy out to its tidal radius, and analysed the spatial distribution of the Fornax stars of different ages as selected from colour-magnitude diagram analysis. We have obtained accurate velocities and metallicities from spectra in the Ca II triplet wavelength region for 562 Red Giant Branch stars which have velocities consistent with membership of the Fornax dwarf spheroidal.
Results: .We have found evidence for the presence of at least three distinct stellar components: a young population (few 100 Myr old) concentrated in the centre of the galaxy, visible as a Main Sequence in the colour-magnitude diagram; an intermediate age population (2-8 Gyr old); and an ancient population (>10 Gyr), which are distinguishable from each other kinematically, from the metallicity distribution and in the spatial distribution of stars found in the colour-magnitude diagram.
Conclusions: . From our spectroscopic analysis we find that the "metal rich" stars ([Fe/H]> -1.3) show a less extended and more concentrated spatial distribution, and display colder kinematics than the "metal poor" stars ([Fe/H]

Dates et versions

hal-03742741 , version 1 (02-08-2022)

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Giuseppina Battaglia, Eline Tolstoy, Amina Helmi, Michael J. Irwin, Bruno Letarte, et al.. The DART imaging and CaT survey of the Fornax dwarf spheroidal galaxy. Astronomy and Astrophysics - A&A, 2006, 459, pp.423-440. ⟨10.1051/0004-6361:20065720⟩. ⟨hal-03742741⟩
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