Ages of Elliptical Galaxies: Single versus Multi Population Interpretation

TL;DR

This paper presents new calibrations for estimating ages and metallicities of elliptical galaxies using spectrophotometric indices, incorporating complex evolutionary models with multiple parameters and comparing results with single stellar population models.

Contribution

It introduces advanced calibrations based on evolutionary models with a two-phase interstellar medium, infall, and galactic winds, improving age and metallicity estimates for elliptical galaxies.

Findings

Mean stellar ages range from 7 to 12 Gyr.

Metallicities vary from half to three times solar.

Models better fit faint ellipticals in the Hbeta-Mg2 diagram.

Abstract

New calibrations of spectrophotometric indices of elliptical galaxies as functions of spectrophotometric indices are presented, permitting estimates of mean stellar population ages and metallicities. These calibrations are based on evolutionary models including a two-phase interstellar medium, infall and a galactic wind.Free parameters were fixed by requiring that models reproduce the mean trend of data in the color-magnitude diagram as well as in the plane of indices Hbeta-Mg2 and Mg2-<Fe>. To improve the location of faint ellipticals(MB > -20) in the Hbeta-Mg2 diagram, down-sizing was introduced. An application of our calibrations to a sample of ellipticals and a comparison with results derived from single stellar population models is given. Our models indicate that mean population ages span an interval of 7-12 Gyr and are correlated with metallicities, which range from approximately half up to three times solar.