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
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: galaxies: evolution; galaxies: formation; galaxies: stellar content; Hubble; sami
• Online Access: https://researchers.mq.edu.au/en/publications/a7c1c73f-a227-4502-8e6f-f28fe62747a0; https://doi.org/10.1093/mnras/stab3477; https://research-management.mq.edu.au/ws/files/200625860/198584095.pdf; http://www.scopus.com/inward/record.url?scp=85126725583&partnerID=8YFLogxK; http://purl.org/au-research/grants/arc/FT140100255; http://purl.org/au-research/grants/arc/CE170100013; http://purl.org/au-research/grants/arc/CE110001020

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)log 10 (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.