The SAMI Galaxy Survey: the link between [α/Fe] and kinematic morphology

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Watson, PJ, Davies, RL, van de Sande, J, Brough, S, Croom, SM, D'Eugenio, F, Glazebrook, K, Groves, B, López-Sánchez, AR, Scott, N, Vaughan, SP, Walcher, CJ, Bland-Hawthorn, J, Bryant, JJ, Goodwin, M, Lawrence, JS, Lorente, NPF, Owers, MS, Richards, S
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2022
• Subjects: sami
• Online Access: https://doi.org/10.1093/mnras/stac1221; https://ora.ox.ac.uk/objects/uuid:095e778d-37fd-4b77-9662-7fc1b04658e2

We explore a sample of 1492 galaxies with measurements of the mean stellar population properties and the spin parameter proxy, λRe, drawn from the SAMI Galaxy Survey. We fit a global [α/Fe]–σ relation, finding that [α/Fe]=(0.395±0.010)log10(σ)−(0.627±0.002). We observe an anti-correlation between the residuals Δ[α/Fe] and the inclination-corrected λeoRe, which can be expressed as Δ[α/Fe]=(−0.057±0.008)λeoRe+(0.020±0.003). The anti-correlation appears to be driven by star-forming galaxies, with a gradient of Δ[α/Fe]∼(−0.121±0.015)λeoRe, although a weak relationship persists for the subsample of galaxies for which star formation has been quenched. We take this to be confirmation that disc-dominated galaxies have an extended duration of star formation. At a reference velocity dispersion of 200 km s−1, we estimate an increase in half-mass formation time from ∼0.5 Gyr to ∼1.2 Gyr from low- to high-λeoRe galaxies. Slow rotators do not appear to fit these trends. Their residual α-enhancement is indistinguishable from other galaxies with λeoRe⪅0.4, despite being both larger and more massive. This result shows that galaxies with λeoRe⪅0.4 experience a similar range of star formation histories, despite their different physical structure and angular momentum.