The SAMI Galaxy Survey: trends in [α/Fe] as a function of morphology and environment

Journal article

We present a new set of index-based measurements of [α/Fe] for a sample of 2093 galaxies in the SAMI Galaxy Survey. Following earlier work, we fit a global relation between [α/Fe] and the galaxy velocity dispersion σ for red sequence galaxies, [α/Fe]=(0.378±0.009)log10(σ/100)+(0.155±0.003)⁠. We observe a correlation between the residuals and the local environmental surface density, whereas no such relation exists for blue cloud galaxies. In the full sample, we find that elliptical galaxies in high-density environments are α-enhanced by up to 0.057 ± 0.014 dex at velocity dispersions σ < 100 km s−1, compared with those in low-density environments. This α-enhancement is morphology-dependent, with the offset decreasing along the Hubble sequence towards spirals, which have an offset of 0.019 ± 0.014 dex. At low velocity dispersion and controlling for morphology, we estimate that star formation in high-density environments is truncated ∼1 Gyr earlier than in low-density environments. For elliptical galaxies only, we find support for a parabolic relationship between [α/Fe] and σ, with an environmental α-enhancement of at least 0.03 dex. This suggests strong contributions from both environment and mass-based quenching mechanisms. However, there is no evidence for this behaviour in later morphological types.

Authors: Watson, PJ; Davies, RL; Brough, S; Croom, SM; D'Eugenio, F

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 510
• Issue: 1
• Pages: 1541-1556
• Publication date: 2021-12-01
• Acceptance date: 2021-11-19
• DOI: 10.1093/mnras/stab3477
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: galaxies: stellar content; FFR; galaxies: evolution; galaxies: formation