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AGN feedback and the origin of the α enhancement in early-type galaxies - insights from the GAEA model

Abstract : We take advantage of our recently published model for GAlaxy Evolution and Assembly (GAEA) to study the origin of the observed correlation between [α/Fe] and galaxy stellar mass. In particular, we analyse the role of radio-mode active galactic nuclei (AGN) feedback, which recent work has identified as a crucial ingredient to reproduce observations. In GAEA, this process introduces the observed trend of star formation histories extending over shorter time-scales for more massive galaxies, but does not provide a sufficient condition to reproduce the observed α enhancements of massive galaxies. In the framework of our model, this is possible only by assuming that any residual star formation is truncated for galaxies more massive than 1010.5 M. This results, however, in even shorter star formation time-scales for the most massive galaxies, which translate in total stellar metallicities significantly lower than observed. Our results demonstrate that (I) trends of [α/Fe] ratios cannot be simply converted into relative time-scale indicators; and (II) AGN feedback cannot explain alone the positive correlation between [α/Fe] and galaxy mass/velocity dispersion. Reproducing simultaneously the mass-metallicity relation and the α enhancements observed pose a challenge for hierarchical models, unless more exotic solutions are adopted such as metal-rich winds or a variable initial mass function.
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Submitted on : Monday, August 8, 2022 - 1:38:18 PM
Last modification on : Tuesday, August 9, 2022 - 3:44:59 AM
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Gabriella de Lucia, Fabio Fontanot, Michaela Hirschmann. AGN feedback and the origin of the α enhancement in early-type galaxies - insights from the GAEA model. Monthly Notices of the Royal Astronomical Society: Letters, 2017, 466, pp.L88-L92. ⟨10.1093/mnrasl/slw242⟩. ⟨insu-03747477⟩



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