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

• Main Authors: Tescari, E., Cortese, L., Power, C., Wyithe, J. S. B., Ho, I. -T., Crain, R. A., Bland-Hawthorn, J., Croom, S. M., Kewley, L. J., Schaye, J., Bower, R. G., Theuns, T., Schaller, M., Barnes, L., Brough, S., Bryant, J. J., Goodwin, M., Gunawardhana, M. L. P., Lawrence, J. S., Leslie, S. K., López-Sánchez, Á. R., Lorente, N. P. F., Medling, A. M., Richards, S. N., Sweet, S. M., Tonini, C.
• Format: Text
• Language: unknown
• Published: arXiv 2017
• Subjects: Astrophysics of Galaxies astro-ph.GA; FOS Physical sciences; sami
• Online Access: https://dx.doi.org/10.48550/arxiv.1709.01939; https://arxiv.org/abs/1709.01939

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 ($σ$) maps are created and compared to observations of disc galaxies obtained with the Sydney-AAO Multi-object Integral field spectrograph (SAMI), where $σ$-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 ($Σ_{\rm SFR}$), with low-M$_{\star}/$low-$Σ_{\rm SFR}$ galaxies showing a narrow peak at low $σ$ ($\sim30$ km s$^{-1}$) and more active, high-M$_{\star}/$high-$Σ_{\rm SFR}$ galaxies reaching $σ>150$ 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 $σ$-distribution. The following equivalence relations hold in EAGLE: $i)$ low-$σ$ peak $\,\Leftrightarrow\,$ disc of the galaxy $\,\Leftrightarrow\,$ gas with T $<10^5$ K; $ii)$ high-$σ$ tail $\,\Leftrightarrow\,$ galactic winds $\,\Leftrightarrow\,$ gas with T $\ge 10^5$ K. : 18 pages, 12 figures, accepted for publication in MNRAS