This paper includes data gathered with the 6.5 Magellan Telescopes, located at Las Campanas Observatory, Chile.
The old open cluster NGC 2112: updated estimates of fundamental parameters based on a membership analysis
Article first published online: 31 MAR 2008
© 2008 The Authors. Journal compilation © 2008 RAS
Monthly Notices of the Royal Astronomical Society
Volume 386, Issue 3, pages 1625–1634, May 2008
How to Cite
Carraro, G., Villanova, S., Demarque, P., Bidin, C. M. and McSwain, M. V. (2008), The old open cluster NGC 2112: updated estimates of fundamental parameters based on a membership analysis. Monthly Notices of the Royal Astronomical Society, 386: 1625–1634. doi: 10.1111/j.1365-2966.2008.13143.x
The data discussed in this paper will be made available at the WEBDA open cluster data base http://www.univie.ac.at/webda, which is maintained by E. Paunzen and J.-C. Mermilliod.
- Issue published online: 16 APR 2008
- Article first published online: 31 MAR 2008
- Accepted 2008 February 21. Received 2008 February 20; in original form 2008 January 17
- open clusters and associations: general;
- open clusters and associations: individual: NGC 2112
We report on a new, wide-field (20 × 20 arcmin2), multicolour (U BV I), photometric campaign in the area of the nearby old open cluster NGC 2112. At the same time, we provide medium-resolution spectroscopy of 35 (and high-resolution of additional 5) red giant and turn-off stars. This material is analysed with the aim to update the fundamental parameters of this traditionally difficult cluster, which is very sparse and suffers from heavy field star contamination. Among the 40 stars with spectra, we identified 21 bona fide radial velocity members which allow us to put more solid constraints on the cluster's metal abundance, long suggested to be as low as the metallicity of globulars. As indicated earlier by us on a purely photometric basis, the cluster [Fe/H] abundance is slightly supersolar ([Fe/H]= 0.16 ± 0.03) and close to the Hyades value, as inferred from a detailed abundance analysis of three of the five stars with higher resolution spectra. Abundance ratios are also marginally supersolar.
Based on this result, we revise the properties of NGC 2112 using stellar models from the Padova and Yale–Yonsei groups.
For this metal abundance, we find that the cluster's age, reddening and distance values are 1.8 Gyr, 0.60 mag and 940 pc, respectively. Both the Yale–Yonsei and Padova models predict the same values for the fundamental parameters within the errors.
Overall, NGC 2112 is a typical solar neighbourhood, thin-disc star cluster, sharing the same chemical properties of F-G stars and open clusters close to the Sun.
This investigation outlines the importance of a detailed membership analysis in the study of disc star clusters.