Yu Zhang, Zhanwen Han, Jinzhong Liu, Fenghui Zhang, Xiaoyu Kang
The number of methods used to study the properties of galaxies is increased,
and testing these methods is very important. Galactic globular clusters (GCs)
provide an excellent medium for such test, because they can be considered as
simple stellar populations. We present ages and metallicities for 40 Galactic
GCs as determined from three publicly available techniques, including colour,
Lick-index and spectrum-fitting methods, based on Bruzual & Charlot
evolutionary population synthesis (EPS) models. By comparing with the ages
obtained from colour-magnitude diagrams (CMDs) and metallicities obtained from
spectra of stars, we are able to estimate the ability of 'these methods on
determination of GCs parameters, which is absolutely necessary. As a result, we
find that: (i) for the metallicity, our derived metallicities agree with those
derived from the spectra of stars, Lick-index method is suitable to study
metallicity for the stellar population systems in the range of
-1.5=<[Fe/H]=<-0.7 and spectrum- fitting method is suitable to study
metallicity for the stellar population systems in the range of
-2.3=<[Fe/H]=<-1.5; (ii) for the age, these three methods have difficulties in
age determination, our derived ages are smaller (about 2.0 Gyr, on average)
than the results of CMDs for all these three methods. We use Vazdekis and
Maraston models to analyze whether our results are dependent on EPS models, and
find that the tendency of these two models is the same as that of Bruzual &
Charlot models. Our results are independent of the EPS models. In addition, our
test is based on the old GCs and our conclusions may hold for old stellar
population systems. The whole abstract can be found in my PDF version.
View original:
http://arxiv.org/abs/1112.6214
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