Abstract
| Velichko |
|---|
| The alpha-element enrichment of gas in distant galaxies |
| Unlike nearby galaxies, the chemical evolution of distant galaxies cannot be assessed from observations of individual stars. On the other hand, the study of the interstellar medium (ISM) can be an alternative way to reveal important properties of the chemical evolution of distant galaxies. The ISM chemical enrichment is produced by all previous generations of stars. It is possible to determine in great details the metal abundances in the neutral ISM in galaxies. The chemical abundance patterns in the neutral ISM are determined by the gas metallicity, the presence of dust (the depletion of metals into dust grains), and possible deviations due to specific nucleosysnthesis, for example alpha-element enhancements. We constrain for the first time the distribution of the alpha-element enhancement with metallicity in the neutral ISM in distant galaxies. Less massive galaxies show an alpha-element knee at lower metallicities than more massive galaxies. If this collective behaviour can be interpreted as for individual systems, this would suggest that more massive and metal-rich systems evolve to higher metallicities before the contribution of SN-Ia to [alpha/Fe] levels out that of core-collapse SNe, possibly explained by different SFR in galaxies of different masses. Overall, our results add important clues to the study of chemical evolution of small and distant galaxies. |