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arXiv · 1709.01939

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

E. Tescari·L. Cortese·C. Power·J. S. B. Wyithe·I. -T. Ho·R. A. Crain·J. Bland-Hawthorn·S. M. Croom·L. J. Kewley·J. Schaye·R. G. Bower·T. Theuns·M. Schaller·L. Barnes·S. Brough·J. J. Bryant·M. Goodwin·M. L. P. Gunawardhana·J. S. Lawrence·S. K. Leslie·Á. R. López-Sánchez·N. P. F. Lorente·A. M. Medling·S. N. Richards·S. M. Sweet·C. Tonini
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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$_{\odot} \le 5.7\times10^{10}$ 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.

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E. Tescari, L. Cortese, C. Power, J. S. B. Wyithe, I. -T. Ho, R. A. Crain, J. Bland-Hawthorn, S. M. Croom, L. J. Kewley, J. Schaye, R. G. Bower, T. Theuns, M. Schaller, L. Barnes, S. Brough, J. J. Bryant, M. Goodwin, M. L. P. Gunawardhana, J. S. Lawrence, S. K. Leslie, Á. R. López-Sánchez, N. P. F. Lorente, A. M. Medling, S. N. Richards, S. M. Sweet, C. Tonini. 2017-09-06. The SAMI Galaxy Survey: understanding observations of large-scale outflows at low redshift with EAGLE simulations. https://doi.org/10.1093/mnras%2Fstx2315

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