Issue |
A&A
Volume 511, February 2010
|
|
---|---|---|
Article Number | A56 | |
Number of page(s) | 19 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361/200912965 | |
Published online | 10 March 2010 |
Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682) *,**
1
INAF – Osservatorio Astronomico di Bologna,
via Ranzani 1, 40127 Bologna, Italy e-mail: [elena.pancino;emanuel.rossetti;ricardo.carrera]@oabo.inaf.it
2
Instituto de Astrofisica de Canarias,
via Lactea s/n, 38200, La Laguna, Tenerife, Spain e-mail: [rcarrera;carme]@iac.es
Received:
23
July
2009
Accepted:
28
September
2009
Context. The present number of Galactic open clusters that have high resolution abundance determinations, not only of [Fe/H], but also of other key elements, is largely insufficient to enable a clear modeling of the Galactic disk chemical evolution.
Aims. To increase the number of Galactic open clusters with high quality measurements.
Methods. We obtained high resolution (R ~ 30 000), high quality (S/N ~ 50–100 per pixel), echelle spectra with the fiber spectrograph FOCES, at Calar Alto, Spain, for three red clump stars in each of five Open Clusters. We used the classical equivalent width analysis method to obtain accurate abundances of sixteen elements: Al, Ba, Ca, Co, Cr, Fe, La, Mg, Na, Nd, Ni, Sc, Si, Ti, V, and Y. We also derived the oxygen abundance using spectral synthesis of the 6300 Å forbidden line.
Results. Three of the clusters were never studied previously with high resolution
spectroscopy: we found [Fe/H] = +0.03±0.02
(±0.10) dex for Cr 110;
[Fe/H] = +0.01±0.05 (±0.10) dex for NGC 2099 (M 37), and
[Fe/H] = -0.05±0.03 (±0.10) dex for NGC 2420. This last finding is
higher than typical literature estimates by 0.2–0.3 dex approximately and in
closer agreement with Galactic trends. For the remaining clusters, we find that
[Fe/H] = +0.05±0.02 (±0.10) dex for M 67 and [Fe/H] = +0.04±0.07
(±0.10) dex for NGC 7789. Accurate (to ~0.5 km s-1) radial
velocities were measured for all targets, and we provide the first velocity
estimate derived from high resolution data for Cr 110,
= 41.0±3.8 km s-1.
Conclusions. With our analysis of the new clusters Cr 110, NGC 2099, and NGC 2420, we
increase the sample of clusters with high-resolution-based abundances by 5%.
All our program stars show abundance patterns which are typical of open
clusters, very close to solar with few exceptions. This is true for all the
iron-peak and s-process elements considered, and no significant
α-enhancement is found. No significant (anti-)correlations for Na, Al,
Mg, and O abundances are found. If anticorrelations are present, the involved
spreads must be <0.2 dex. We then compile high resolution data of 57 OC from
the literature and find a gradient of [Fe/H] with Galactocentric radius of
–0.06±0.02 dex kpc-1, in agreement with past work and with results
for Cepheids and B stars in the same range. A change of slope is seen outside
RGC = 12 kpc and [ α/Fe] shows a tendency to increase with
RGC. We also confirm the absence of a significant age-metallicity
relation, finding slopes of –2.6±1.1 10-11 dex Gyr-1 and
1.1±5.0
10-11 dex Gyr-1 for [Fe/H] and [ α/Fe]
respectively.
Key words: stars: abundances / Galaxy: disk / open clusters and associations: general
Based on data collected with the fiber spectrograph FOCES at the 2.2 m Calar Alto Telescope. Also based on data from the 2MASS survey and the WEBDA, VALD, NIST, and GEISA online databases.
Full Table 5 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/A56
© ESO, 2010
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