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, $\lambda_{R_{\rm{e}}}$,
drawn from the SAMI Galaxy Survey. We fit a global
$\left[\alpha/\rm{Fe}\right]$-$\sigma$ relation, finding that
$\left[\alpha/\rm{Fe}\right]=(0.395\pm0.010)\rm{log}_{10}\left(\sigma\right)-(0.627\pm0.002)$.
We observe an anti-correlation between the residuals
$\Delta\left[\alpha/\rm{Fe}\right]$ and the inclination-corrected
$\lambda_{\,R_{\rm{e}}}^{\rm{\,eo}}$, which can be expressed as
$\Delta\left[\alpha/\rm{Fe}\right]=(-0.057\pm0.008)\lambda_{\,R_{\rm{e}}}^{\rm{\,eo}}+(0.020\pm0.003)$.
The anti-correlation appears to be driven by star-forming galaxies, with a
gradient of
$\Delta\left[\alpha/\rm{Fe}\right]\sim(-0.121\pm0.015)\lambda_{\,R_{\rm{e}}}^{\rm{\,eo}}$,
although a weak relationship persists for the subsample of galaxies for which
star formation has been quenched. We take this to be confirmation that
disk-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 $\sim$0.5 Gyr to $\sim$1.2 Gyr from low- to
high-$\lambda_{\,R_{\rm{e}}}^{\rm{\,eo}}$ galaxies. Slow rotators do not appear
to fit these trends. Their residual $\alpha$-enhancement is indistinguishable
from other galaxies with $\lambda_{\,R_{\rm{e}}}^{\rm{\,eo}}\lessapprox0.4$,
despite being both larger and more massive. This result shows that galaxies
with $\lambda_{\,R_{\rm{e}}}^{\rm{\,eo}}\lessapprox0.4$ experience a similar
range of star formation histories, despite their different physical structure
and angular momentum.
