The formation and evolution of galaxies is considered one of the hottest topics in Modern Astronomy. Studies on their stellar content have provided severe restrictions on their formation processes. A key result is that galaxies show abundances element ratios that differ from those found in the solar neighborhood. The abundance patterns are intimately linked to the Star Formation History of these galaxies. This is because the stars, when dying, release chemical elements synthesized in its interiors on time scales that depend on the initial mass. Massive elliptical galaxies show a pattern enriched in Magnesium over Iron, indicating that their stars formed on a scale shorter than a Gigayear. Recent observations show the existence of a wide variety of galaxies, from massive elliptical to ultra diffuse, characterized by patterns that differ from the solar neighborhood of the Milky Way. Estimating these abundances allow us to constrain their time scales and thus elucidate their possible routes of formation. It is the perfect time to develop a new generation of stellar populations models to interpret the spectra of galaxies obtained with large telescopes in earth and space, as well as those from extensive galaxy surveys being carried out in present days. The main ingredient of these models is the empirical libraries of stellar spectra, among which MILES stands out, obtained by our group in Observatorio de el Roque de Los Muchachos. This library, which has recently been expanded, is recognized as the first reference in the field of stellar populations.
This project aims at building a set of semi-empirical stellar spectral libraries with variable abundance element ratios and wide spectral coverage, from Ultra Violet to Near Infrared. The necessary codes to synthesize stellar spectra with varying key elements, such as Magnesium, Carbon, Sodium, among others, which provide us with a set of chemical clocks suitable for different time scales, are already developed at the IAC. From these libraries theoretical differential responses will be extracted by varying these abundances to correct the real stars and thus generate the semi-empirical libraries with variable abundances. These libraries will be implemented in our E-MILES stellar populations models to compute the spectra of galaxies with varying abundances. E-MILES constitutes a standard reference in the field and are widely used by the community and also in other areas of research.
Finally, with these models, new key diagnostics will be designed to provide chemical clocks to constrain the formation time scales of galaxies with precision unprecedented in the literature, thus maintaining our recognized leadership in the field.
