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On the metallicity of open clusters III. Homogenised sample
Masaryk Univ, Dept Theoret Phys & Astrophys, Kotlarska 2, CS-61137 Brno, Czech Republic..
Masaryk Univ, Dept Theoret Phys & Astrophys, Kotlarska 2, CS-61137 Brno, Czech Republic..
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
Univ Bordeaux, CNRS, LAB, UMR 5804, BP 89, F-33270 Floirac, France..
2016 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 585, A150Article in journal (Refereed) PublishedText
Abstract [en]

Context. Open clusters are known as excellent tools for various topics in Galactic research. For example, they allow accurately tracing the chemical structure of the Galactic disc. However, the metallicity is known only for a rather low percentage of the open cluster population, and these values are based on a variety of methods and data. Therefore, a large and homogeneous sample is highly desirable. Aims. In the third part of our series we compile a large sample of homogenised open cluster metallicities using a wide variety of different sources. These data and a sample of Cepheids are used to investigate the radial metallicity gradient, age effects, and to test current models. Methods. We used photometric and spectroscopic data to derive cluster metallicities. The different sources were checked and tested for possible off sets and correlations. Results. In total, metallicities for 172 open cluster were derived. We used the spectroscopic data of 100 objects for a study of the radial metallicity distribution and the age-metallicity relation. We found a possible increase of metallicity with age, which, if confirmed, would provide observational evidence for radial migration. Although a statistical significance is given, more studies are certainly needed to exclude selection effects, for example. The comparison of open clusters and Cepheids with recent Galactic models agrees well in general. However, the models do not reproduce the flat gradient of the open clusters in the outer disc. Thus, the effect of radial migration is either underestimated in the models, or an additional mechanism is at work. Conclusions. Apart from the Cepheids, open clusters are the best tracers for metallicity over large Galactocentric distances in the Milky Way. For a sound statistical analysis, a sufficiently large and homogeneous sample of cluster metallicities is needed. Our compilation is currently by far the largest and provides the basis for several basic studies such as the statistical treatment of the Galactic cluster population, or evolutionary studies of individual star groups in open clusters.

Place, publisher, year, edition, pages
2016. Vol. 585, A150
Keyword [en]
Galaxy: abundances, Galaxy: structure, open clusters and associations: general
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:uu:diva-282005DOI: 10.1051/0004-6361/201526370ISI: 000369710300157OAI: oai:DiVA.org:uu-282005DiVA: diva2:916165
Swedish National Space BoardEU, European Research Council, 291782
Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2016-04-01Bibliographically approved

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Heiter, Ulrike
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