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

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Watson, Peter J, Davies, Roger L, Brough, Sarah, Croom, Scott M, D’Eugenio, Francesco, Glazebrook, Karl, Groves, Brent, López-Sánchez, Ángel R, van de Sande, Jesse, Scott, Nicholas, Vaughan, Sam P, Walcher, Jakob, Bland-Hawthorn, Joss, Bryant, Julia J, Goodwin, Michael, Lawrence, Jon S, Lorente, Nuria P F, Owers, Matt S, Richards, Samuel
• Other Authors: Australian Research Council, Science and Technology Facilities Council, Horizon 2020 European Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2021
• Subjects: Space and Planetary Science; Astronomy and Astrophysics; Hubble; sami
• Online Access: http://dx.doi.org/10.1093/mnras/stab3477; https://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/stab3477/41429143/stab3477.pdf; https://academic.oup.com/mnras/article-pdf/510/1/1541/41988573/stab3477.pdf

ABSTRACT 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, $[\alpha /\text{Fe}]=(0.378\pm 0.009)\rm {log}_{10}\left(\sigma /100\right)+(0.155\pm 0.003)$. 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.