Volume 585, January 2016
|Number of page(s)||18|
|Section||Galactic structure, stellar clusters and populations|
|Published online||21 December 2015|
Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy⋆
Astrophysics Research Institute, Liverpool John Moores
146 Brownlow Hill,
2 Instituto de Astrofisica de Canarias, 38205, La Laguna, Tenerife, Spain
3 Universidad de la Laguna, Dpto. Astrofisica, 38206, La Laguna, Tenerife, Spain
4 INAF Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
5 ASI Science Data Center, via del Politecnico SNC, 00133 Roma, Italy
6 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
7 Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
8 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, The Netherlands
9 Laboratoire d’ astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), Observatoire, 1290 Versoix, Switzerland
10 GEPI, Observatoire de Paris, CNRS, Université de Paris Diderot, 92195 Meudon, Cedex, France
Received: 17 September 2015
Accepted: 26 October 2015
We present [C/Fe] and [N/Fe] abundance ratios and CH(λ4300) and S(λ3883) index measurements for 94 red giant branch (RGB) stars in the Sculptor dwarf spheroidal galaxy from VLT/VIMOS MOS observations at a resolving power R = 1150 at 4020 Å. This is the first time that [N/Fe] abundances are derived for a large number of stars in a dwarf spheroidal. We found a trend for the [C/Fe] abundance to decrease with increasing luminosity on the RGB across the whole metallicity range, a phenomenon observed in both field and globular cluster giants, which can be interpreted in the framework of evolutionary mixing of partially processed CNO material. Both our measurements of [C/Fe] and [N/Fe] are in good agreement with the theoretical predictions for stars at similar luminosity and metallicity. We detected a dispersion in the carbon abundance at a given [Fe/H], which cannot be ascribed to measurement uncertainties alone. We interpret this observational evidence as the result of the contribution of different nucleosynthesis sources over time to a not well-mixed interstellar medium. We report the discovery of two new carbon-enhanced, metal-poor stars. These are likely the result of pollution from material enriched by asymptotic giant branch stars, as indicated by our estimates of [Ba/Fe] >+1. We also attempted a search for dissolved globular clusters in the field of the galaxy by looking for the distinctive C-N pattern of second population globular clusters stars in a previously detected, very metal-poor, chemodynamical substructure. We do not detect chemical anomalies among this group of stars. However, small number statistics and limited spatial coverage do not allow us to exclude the hypotheses that this substructure forms part of a tidally shredded globular cluster.
Key words: stars: abundances / galaxies: dwarf / galaxies: evolution / Local Group / galaxies: formation
© ESO, 2015
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.