The star formation timescale of elliptical galaxies -- Fitting [Mg/Fe] and total metallicity simultaneously

Understand

The alpha element to iron peak element ratio, for example [Mg/Fe], is a commonly applied indicator of the galaxy star formation timescale (SFT) since the two groups of elements are mainly produced by different types of supernovae that explode over different timescales.

• However, it is insufficient to consider only [Mg/Fe] when estimating the SFT.
• The [Mg/Fe] yield of a stellar population depends on its metallicity.
• Therefore, it is possible for galaxies with different SFTs and at the same time different total metallicity to have the same [Mg/Fe].