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|Title:||On the α-element gradients of the Galactic thin disk using Cepheids||Authors:||Genovali, K.
Oliveira Da Silva, Ronaldo
Laney, C. D.
Kudritzki, R. -P.
Urbaneja, M. A.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||580||First Page:||A17||Abstract:||We present new homogeneous measurements of Na, Al, and three α-elements (Mg, Si, Ca) for 75 Galactic Cepheids. The abundances are based on high spectral resolution (R~ 38 000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT. The current measurements were complemented with Cepheid abundances provided by our group (75) or available in the literature, for a total of 439 Galactic Cepheids. Special attention was given to providing a homogeneous abundance scale for these five elements plus iron. In addition, accurate Galactocentric distances based on near-infrared photometry are also available for all the Cepheids in the sample. They cover a large section of the Galactic thin disk (4.1 ≤R<SUB>G</SUB>≤ 18.4 kpc). We found that these five elements display well-defined linear radial gradients and modest standard deviations over the entire range of R<SUB>G</SUB>. Moreover, the [element/Fe] abundance ratios are constant across the entire thin disk; only the Ca radial distribution shows marginal evidence of a positive slope. These results indicate that the chemical enrichment history of iron and of the quoted five elements has been quite similar across the four quadrants of the Galactic thin disk. The [element/Fe] ratios are also constant over the entire period range. This empirical evidence indicates that the chemical enrichment of Galactic Cepheids has also been very homogenous within the range in age that they cover (~10-300 Myr). Once again, [Ca/Fe] vs. log P shows a (negative) gradient, since it is underabundant among the youngest Cepheids. Finally, we also find that Cepheid abundances agree quite well with similar abundances for thin and thick disk dwarf stars, and they follow the typical Mg-Al and Na-O correlations.Based on spectra collected with the UVES spectrograph available at the ESO Very Large Telescope (VLT), Cerro Paranal, Chile (ESO Proposals: 081.D-0928(A), PI: S. Pedicelli; 082.D-0901(A), PI: S. Pedicelli; 089.D-0767(C), PI: K. Genovali).Tables 1, 2, and 5 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://184.108.40.206) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A17">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A17||Acknowledgments:||This work was partially supported by PRIN-MIUR (2010 LY5N2T) “Chemical and dynamical evolution of the Milky Way and Local Group galaxies” (P.I.: F. Matteucci). M.F. acknowledges the financial support from the PO FSE Abruzzo 2007-2013 through the grant “Spectro-photometric characterization of stellar populations in Local Group dwarf galaxies” prot. 89/2014/OACTe/D (P.I.: S. Cassisi). We also acknowledge an anonymous referee for the positive opinions concerning this experiment and for the very pertinent suggestions that improved the content and the readability of the paper.||URI:||http://hdl.handle.net/20.500.12386/24096||URL:||https://www.aanda.org/articles/aa/abs/2015/08/aa25894-15/aa25894-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201525894||Bibcode ADS:||2015A&A...580A..17G||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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