Galaxy gas-phase abundances and their connection to star-formation historiesRecording
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Gas-phase abundances in galaxies are the products of those galaxies’ evolutionary histories. The star-formation history (SFH) of a region might therefore be expected to influence that region’s present day gaseous abundances. Here, I will describe a recent MaNGA spectroscopic study exploring how local gas metallicities relate to star-formation histories of galaxy regions. We combined MaNGA emission line measurements with SFH classifications from absorption line spectra, to compare gas-phase abundances in star-forming regions with those in regions classified as starburst, post-starburst and green valley. We found that starburst regions contain gas that is more pristine than in normal star-forming regions, in terms of O/H and N/O; we further found that post-starburst regions (which have experienced stochastic SFHs) behave very similarly to ordinary star-forming regions (which have experienced far smoother SFHs) in O/H–N/O space. We argued from this that gas is diluted significantly by pristine infall but is then re-enriched rapidly after a starburst event, making gas-phase abundances insensitive to the precise form of the SFH at late times. We also found that green-valley regions typically possess elevated N/O abundances at a given O/H; this is potentially due to a reduced star-formation efficiency in such regions, but it could also point to late-time rejuvenation of green valley regions in our sample. In the final few minutes, I will describe a subsequent MaNGA study on galaxy N/O abundances across the mass-size plane. I will show a particularly tight correlation between N/O and approximate gravitational potential M*/Re, which appears to be even stronger than the potential-metallicity relations reported in other recent works.
Enrica Bellocchi