The Carina Project: VIII. the α-element abundances

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DOI	Resolve DOI: https://doi.org/10.1051/0004-6361/201525753
Author	Search for: Fabrizio, M.; Search for: Nonino, M.; Search for: Bono, G.; Search for: Primas, F.; Search for: Thévenin, F.; Search for: Stetson, P. B.¹; Search for: Cassisi, S.; Search for: Buonanno, R.; Search for: Coppola, G.; Search for: Da Silva, R. O.; Search for: Dall’ora, M.; Search for: Ferraro, I.; Search for: Genovali, K.; Search for: Gilmozzi, R.; Search for: Iannicola, G.; Search for: Marconi, M.; Search for: Monelli, M.; Search for: Romaniello, M.; Search for: Walker, A. R.
Name affiliation	National Research Council of Canada. Herzberg Astronomy and Astrophysics
Format	Text, Article
Journal title	Astronomy & Astrophysics
ISSN	0004-6361 1432-0746
Volume	580
Article number	A18
Subject	galaxies: dwarf; galaxies: stellar content; stars: fundamental parameters; galaxies: individual: Carina; stars: abundances
Abstract	We have performed a new abundance analysis of Carina red giant (RG) stars from spectroscopic data collected with UVES (high spectral resolution) and FLAMES/GIRAFFE (high and medium resolution) at ESO/VLT. The former sample includes 44 RGs, while the latter consists of 65 (high-resolution) and ~800 (medium-resolution) RGs, covering a significant fraction of the galaxy’s RG branch, and red clump stars. To improve the abundance analysis at the faint magnitude limit, the FLAMES/GIRAFFE data were divided into ten surface gravity and effective temperature bins. The spectra of the stars belonging to the same gravity and temperature bin were stacked. This approach allowed us to increase the signal-to-noise ratio in the faint magnitude limit (V≥ 20.5 mag) by at least a factor of five. We took advantage of the new photometry index cU,B,I introduced recently as an age and probably a metallicity indicator to split stars along the red giant branch. These two stellar populations display distinct [Fe/H] and [Mg/H] distributions: their mean iron abundances are −2.15 ± 0.06 dex (σ = 0.28), and −1.75 ± 0.03 dex (σ = 0.21), respectively. The two iron distributions differ at the 75% level. This supports preliminary results. Moreover, we found that the old and intermediate-age stellar populations have mean [Mg/H] abundances of −1.91 ± 0.05 dex (σ = 0.22) and −1.35 ± 0.03 dex (σ = 0.22); these differ at the 83% level. Carina’s α-element abundances agree, within 1σ, with similar abundances for field halo stars and for cluster (Galactic and Magellanic) stars. The same outcome applies to nearby dwarf spheroidals and ultra-faint dwarf galaxies in the iron range covered by Carina stars. Finally, we found evidence of a clear correlation between Na and O abundances, thus suggesting that Carina’s chemical enrichment history is quite different from that in the globular clusters.
Publication date	2015-07-22
Publisher	EDP Sciences
Language	English
Peer reviewed	Yes
NPARC number	23001643
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Record identifier	be23b8d0-f9c0-4080-97cf-ddcecfa09b7a
Record created	2017-03-14
Record modified	2020-05-30

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Date modified:: 2020-07-08