Metals in the interstellar medium are key for the formation and evolution of galaxies, stars, molecules, and planets. With absorption-line spectroscopy we probe in great detail the chemical (relative) abundances of several metals in the gas-phase inside/around galaxies. This can be done by targeting stars in the Local Group, or distant quasars and gamma-ray-bursts, out to and beyond the reionisation era. Several processes play a role in determining the observed abundances in the neutral gas: i) the metallicity; ii) the depletion of metals into dust grains; iii) the contribution from nucleosynthesis of specific stellar population (e.g. ⍺-element enhancements). In the past years I developed an effective methodology to disentangle and characterise these aspects. The most exciting findings on metals are that in the Milky Way (and distant galaxies) metals are not uniformly distributed, but there are pockets of low-metallicity gas. In the Magellanic Clouds there are ⍺-element enhancements in the gas out to high metallicities, suggesting a recent burst of star formation. In distant galaxies (Damped Ly-⍺ absorbers) we measure the ⍺-element distribution with metallicity and find that the ⍺-element knee changes with a galaxy mass tracer. In a z=6.3 GRB host galaxy we find strong ⍺-element enhancements and and intriguing overabundance of aluminium. This is a new window into galaxy chemical evolution and the role of massive stars in the chemical enrichment of the early universe.
|
