Evolutionary stellar population synthesis at 2A spectral resolution

Abstract

We present an evolutionary stellar population synthesis model which predicts SED's for simple stellar populations, SSP's, at ~2A resolution in the visible. The input database is composed of ~550 stars, selected from the spectral library of Jones. This is the first time that an evolutionary model employs such an extensive empirical stellar spectral library, at such high resolution. A SSP spectral library with -0.7<[Fe/H]<+0.2 is provided, as well as an extensive discussion about the Lick system of indices at intermediate resolution, showing the advantages of using the new model predictions. It is shown the Rose indices, at higher resolution, as a function of the age and metallicity of the stellar population. The SSP spectra, with flux-calibrated response curve, can be smoothed to the same resolution of the data, or to the galaxy internal velocity dispersion, allowing us to analyze the observed spectrum in its own system. Therefore we are able to utilize all the information contained in the data, at their spectral resolution. After performing this step, the entire observational spectrum can be compared at once, or the analysis can be done measuring a particular set of features in the two, the synthesized and the observational spectrum, rather than trying to correct the latter from broadening or instrumental effects. The SSP spectra were calibrated with two metal-rich GC's, 47Tuc and NGC 6624, providing excellent fits and being able to detect well known spectral peculiarities such as 47Tuc CN anomaly. The model was confronted to an early-type galaxy, NGC 3379, revealing its well known Mg/Fe over-abundance, and showing how appropriate are the new model predictions, as well as the way in which they can be used, for studying elemental ratios in these systems.