Abstract details

The integrated light of galaxies suffers the well-known age-metallicity degeneracy, making a galaxy look redder because it is older or it has higher metallicity. One expects that, rather than colors, spectral information should break this degeneracy, but even the most popular age indicator, the Lick index based on H_{$\beta$}, does depend on metallicity. In spite of the fact that other indicators based on the H_{$\gamma$} feature have shown great metallicity independence, they are unviable for a huge number of projects since their signal-to-noise requierements reach up 300 SN/\AA. Here, we introduce a new spectral H_{$\beta$} definition to explore the real power of this feature at breaking the age-metallicity degeneracy avoiding the high signal-to-noise requiered by others.