The role of massive stars in galactic chemical evolution

TL;DR

This paper reviews the critical role of massive stars in galactic chemical evolution, highlighting their impact on element production, galactic winds, and the interpretation of observational data across different galaxy types.

Contribution

It provides a comprehensive synthesis of how massive stars influence galactic evolution, including new insights into mass loss, rotation effects, and the connection to gamma-ray bursts.

Findings

Massive stars are key producers of primary nitrogen with rotation.

Galactic winds driven by massive stars shape chemical abundances.

Downsizing in star formation explains [Mg/Fe] trends in ellipticals.

Abstract

I will review the role of massive stars in galactic evolution both from the nucleosynthesis and energetics point of view. In particular, I will highlight some important observational facts explained by means of massive stars in galaxies of different morphological type: the Milky Way, ellipticals and dwarf spheroidals. I will describe first the time-delay model and its interpretation in terms of abundance ratios in galaxies, then I will discuss the importance of mass loss in massive stars to reproduce the data in the Galactic bulge and disk. I will discuss also how massive stars can be important producers of primary nitrogen if rotation in stellar models is taken into account. Concerning elliptical galaxies, I will show that to reproduce the observed [Mg/Fe] versus Mass relation in these galaxies it is necessary to assume a more important role of massive stars in more massive galaxies and that this can be achieved by means of downsizing in star formation. I will discuss how massive stars are responsible in triggering galactic winds both in ellipticals and dwarf spheroidals. These latter systems show a low overabundance of alpha-elements relative to Fe with respect to Galactic stars of the same [Fe/H]: this is interpreted as due to a slow star formation coupled with very efficient galactic winds. Finally, I will show a comparison between the predicted Type Ib/c rates in galaxies and the observed GRB rate and how we can impose constraints on the mechanism of galaxy formation by studying the GRB rate at high redshift.