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VLT spectroscopy of NGC 3115 globular clusters

Kuntschner, H.; Ziegler, B.L.; Sharples, R.M.; Worthey, G.; Fricke, K.J.

VLT spectroscopy of NGC 3115 globular clusters Thumbnail


H. Kuntschner

B.L. Ziegler

G. Worthey

K.J. Fricke


We present results derived from VLT-FORS2 spectra of 24 different globular clusters associated with the lenticular galaxy NGC 3115. A subsample of 17 globular clusters have sufficiently high signal-to-noise to allow precision measurements of absorption line-strengths. Comparing these indices to new stellar population models by Thomas et al. we determine ages, metallicities and element abundance ratios. For the first time these stellar population models explicitly take abundance ratio biases in the Lick/IDS stellar library into account. Our data are also compared with the Lick/IDS observations of Milky Way and M 31 globular clusters. Unpublished higher order Balmer lines (HgammaA ,F and HdeltaA ,F) from the Lick/IDS observations are given in the Appendix. Our best age estimates show that the observed clusters which sample the bimodal colour distribution of NGC 3115 are coeval within our observational errors (2-3 Gyr). Our best calibrated age/metallicity diagnostic diagram (Hbeta / vs. [MgFe]) indicates an absolute age of 11-12 Gyr consistent with the luminosity weighted age for the central part of NGC 3115. We confirm with our accurate line-strength measurements that the (V-I) colour is a good metallicity indicator within the probed metallicity range (-1.5 < [Fe/H] < 0.0). The abundance ratios for globular clusters in NGC 3115 give an inhomogeneous picture. We find a range from solar to super-solar ratios for both blue and red clusters. This is similar to the data for M 31 while the Milky Way seems to harbour clusters which are mainly consistent with [alpha / Fe] =~ 0.3. From our accurate recession velocities we detect, independent of metallicity, clear rotation in the sample of globular clusters. In order to explain the metallicity and abundance ratio pattern, particularly the range in abundance ratios for the metal rich globular clusters in NGC 3115, we favour a formation picture with more than two distinct formation episodes. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile (ESO No. 66.B-0131).


Kuntschner, H., Ziegler, B., Sharples, R., Worthey, G., & Fricke, K. (2002). VLT spectroscopy of NGC 3115 globular clusters. Astronomy & Astrophysics, 395(3), 761-777.

Journal Article Type Article
Publication Date Dec 1, 2002
Deposit Date May 29, 2008
Publicly Available Date May 29, 2008
Journal Astronomy and astrophysics.
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 395
Issue 3
Pages 761-777
Keywords Galaxies, Abundances, Star clusters, Stellar content, Global clusters.


Published Journal Article (535 Kb)

Copyright Statement
Reproduced with permission from Astronomy & Astrophysics, © ESO

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