J/A+A/557/A10 Metallicities of open clusters (Netopil+, 2013)
Towards a photometric metallicity scale for open clusters.
Netopil M., Paunzen E.
<Astron. Astrophys. 557, A10 (2013)>
=2013A&A...557A..10N 2013A&A...557A..10N
ADC_Keywords: Clusters, open ; Reddening ; Abundances, [Fe/H]
Keywords: Hertzsprung-Russell and C-M diagrams -
open clusters and associations: general - galaxy: abundances -
stars: abundances - stars: evolution
Abstract:
Open clusters are a useful tool when investigating several topics
connected with stellar evolution; for example the age or distance can
be more accurately determined than for field stars. However, one
important parameter, the metallicity, is only known for a marginal
percentage of open clusters.
We aim at a consistent set of parameters for the open clusters
investigated in our photometric Delta-a survey of chemically peculiar
stars. Special attention is paid to expanding our knowledge of cluster
metallicities and verifying their scale.
Making use of a previously developed method based on normalised
evolutionary grids and photometric data, the distance, age, reddening,
and metallicity of open clusters were derived. To transform
photometric measurements into effective temperatures to use as input
for our method, a set of temperature calibrations for the most
commonly used colour indices and photometric systems was compiled.
We analysed 58 open clusters in total. Our derived metallicity values
were in excellent agreement with about 30 spectroscopically studied
targets. The mean value of the absolute deviations was found to be
0.03dex, with no noticeable offset or gradient. The method was also
applied using recent evolutionary models based on the currently
accepted lower solar abundance value Z∼0.014. No significant
differences were found compared to grids using the former adopted
solar value Z=0.02. Furthermore, some divergent photometric datasets
were identified and discussed.
The method provides an accurate way of obtaining properly scaled
metallicity values for open clusters. In light of present and future
homogeneous photometric sky surveys, the sample of stellar clusters
can be extended to the outskirts of the Milky Way, where spectroscopic
studies are almost impossible. This will help for determining galactic
metallicity gradients in more detail.
Description:
The fundamental parameters (age, distance, reddening, and metallicity)
for 58 galactic open clusters determined using photometric data and
the method by Poehnl & Paunzen (2010A&A...514A..81P 2010A&A...514A..81P)
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 68 58 Parameters for 58 open clusters
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See also:
B/ocl : Optically visible open clusters and Candidates (Dias+ 2002-2013)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Cluster name
15- 24 A10 --- OName ? Other cluster ID (IAU number)
26- 29 F4.2 [yr] log(t) [7.3/9] Age (log scale)
31- 35 F5.2 mag DM0 True cluster distance modulus
37- 40 F4.2 mag E(B-V) Cluster reddening
42- 45 F4.2 mag e_E(B-V) ? Standard error on E(B-V) (1)
47- 51 F5.3 --- Z [0.014/0.031] Overall cluster metallicity
53- 57 F5.3 --- e_Z Error on Z
59- 63 F5.2 [Sun] [Fe/H] [-0.16/0.24] Iron abundance (2)
65- 68 F4.2 [Sun] e_[Fe/H] Error on iron abundance
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Note (1): If reddening was determined for individual stars via photometric
calibrations, otherwise empty.
Note (2): Iron abundance relative to the Sun, calculated from Z using
Zsun=0.019 and Y=0.23+2.25Z.
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Acknowledgements:
Martin Netopil, martin.netopil(at)univie.ac.at
(End) Patricia Vannier [CDS] 20-Sep-2013