The metal enrichment of passive galaxies in cosmological simulations of galaxy formation

Okamoto, T.; Nagashima, M.; Lacey, C.G.; Frenk, C.S.

Abstract

Massive early-type galaxies have higher metallicities and higher ratios of α elements to iron than their less massive counterparts. Reproducing these correlations has long been a problem for hierarchical galaxy formation theory, both in semi-analytic models and cosmological hydrodynamic simulations. We show that a simulation in which gas cooling in massive dark haloes is quenched by radio-mode active galactic nuclei (AGNs) feedback naturally reproduces the observed trend between α/Fe and the velocity dispersion of galaxies, σ. The quenching occurs earlier for more massive galaxies. Consequently, these galaxies complete their star formation before α/Fe is diluted by the contribution from Type Ia supernovae. For galaxies more massive than ∼1011 M⊙, whose α/Fe correlates positively with stellar mass, we find an inversely correlated mass–metallicity relation. This is a common problem in simulations in which star formation in massive galaxies is quenched either by quasar- or radio-mode AGN feedback. The early suppression of gas cooling in progenitors of massive galaxies prevents them from recapturing enriched gas ejected as winds. Simultaneously reproducing the [α/Fe]–σ relation and the mass–metallicity relation is, thus, difficult in the current framework of galaxy formation.

Citation

Okamoto, T., Nagashima, M., Lacey, C., & Frenk, C. (2017). The metal enrichment of passive galaxies in cosmological simulations of galaxy formation. Monthly Notices of the Royal Astronomical Society, 464(4), 4866-4874. https://doi.org/10.1093/mnras/stw2729

• Journal Article Type: Article
• Acceptance Date: Oct 20, 2016
• Online Publication Date: Oct 23, 2016
• Publication Date: Feb 1, 2017
• Deposit Date: Feb 27, 2017
• Publicly Available Date: Mar 2, 2017
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 464
• Issue: 4
• Pages: 4866-4874
• DOI: https://doi.org/10.1093/mnras/stw2729
• Public URL: https://durham-repository.worktribe.com/output/1363870