The SAMI Galaxy Survey: understanding observations of large-scale
  outflows at low redshift with EAGLE simulations
  This work presents a study of galactic outflows driven by stellar feedback.
We extract main sequence disc galaxies with stellar mass $10^9\le$
M$_{\star}/$M$_{\odot} \le 5.7\times10^{10}$ at redshift $z=0$ from the highest
resolution cosmological simulation of the Evolution and Assembly of GaLaxies
and their Environments (EAGLE) set. Synthetic gas rotation velocity and
velocity dispersion ($\sigma$) maps are created and compared to observations of
disc galaxies obtained with the Sydney-AAO Multi-object Integral field
spectrograph (SAMI), where $\sigma$-values greater than $150$ km s$^{-1}$ are
most naturally explained by bipolar outflows powered by starburst activity. We
find that the extension of the simulated edge-on (pixelated) velocity
dispersion probability distribution depends on stellar mass and star formation
rate surface density ($\Sigma_{\rm SFR}$), with
low-M$_{\star}/$low-$\Sigma_{\rm SFR}$ galaxies showing a narrow peak at low
$\sigma$ ($\sim30$ km s$^{-1}$) and more active,
high-M$_{\star}/$high-$\Sigma_{\rm SFR}$ galaxies reaching $\sigma>150$ km
s$^{-1}$. Although supernova-driven galactic winds in the EAGLE simulations may
not entrain enough gas with T $<10^5$ K compared to observed galaxies, we find
that gas temperature is a good proxy for the presence of outflows. There is a
direct correlation between the thermal state of the gas and its state of motion
as described by the $\sigma$-distribution. The following equivalence relations
hold in EAGLE: $i)$ low-$\sigma$ peak $\,\Leftrightarrow\,$ disc of the galaxy
$\,\Leftrightarrow\,$ gas with T $<10^5$ K; $ii)$ high-$\sigma$ tail
$\,\Leftrightarrow\,$ galactic winds $\,\Leftrightarrow\,$ gas with T $\ge
10^5$ K.
