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

We explore a sample of 1492 galaxies with measurements of the mean stellar population properties and the spin parameter proxy, lambda(Re), drawn from the SAMI Galaxy Survey. We fit a global [alpha/Fe]-sigma relation, finding that [alpha/Fe] = (0.395 +/- 0.010)log(10)(sigma) - (0.627 +/- 0.002). We observe an anti-correlation between the residuals Delta[alpha/Fe] and the inclination-corrected lambda(eo)(Re), which can be expressed as Delta[alpha/Fe] = (-0.057 +/- 0.008) lambda(eo)(Re) + (0.020 +/- 0.003). The anti-correlation appears to be driven by star-forming galaxies, with a gradient of Delta[alpha/Fe] similar to (-0.121 +/- 0.015) lambda(eo)(Re), 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 similar to 0.5 Gyr to (similar to)1.2 Gyr from low- to high-lambda(eo)(Re) Re galaxies. Slow rotators do not appear to fit these trends. Their residual a-enhancement is indistinguishable from other galaxies with lambda(eo)(Re) (sic) 0.4, despite being both larger and more massive. This result shows that galaxies with lambda(eo)(Re) (sic) 0.4 experience a similar range of star formation histories, despite their different physical structure and angular momentum.