The SAMI Galaxy Survey: understanding observations of large-scale outflows at low redshift with EAGLE simulations

Abstract

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${}_{\odot }\le 5.7\times 10^{10}$ 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 (${\Sigma }_{\mathrm{SFR}}$), with low-M${}_{\star }/$low-${\Sigma }_{\mathrm{SFR}}$ galaxies showing a narrow peak at low $\sigma$ ($\sim 30$ km s${}^{-1}$) and more active, high-M${}_{\star }/$high-${\Sigma }_{\mathrm{SFR}}$ 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 $\iff$ disc of the galaxy $\iff$ gas with T $<10^5$ K; $ii)$ high-$\sigma$ tail $\iff$ galactic winds $\iff$ gas with T $\ge 10^5$ K.

18 pages, 12 figures, accepted for publication in MNRAS

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Cited by in corpus (3)

• A Review of Recent Observations of Galactic Winds Driven by Star Formation
• An evolving and mass dependent ${\sigma }_{\text{sSFR}}$-${\mathrm{M}}_{\star }$ relation for galaxies
• Spatially resolved mock observations of stellar kinematics: full radiative transfer treatment of simulated galaxies