SILCC VII -- Gas kinematics and multiphase outflows of the simulated ISM at high gas surface densities

We present magnetohydrodynamic (MHD) simulations of the star-forming multiphase interstellar medium (ISM) in stratified galactic patches with gas surface densities \(\Sigma_\mathrm{gas} =\) 10, 30, 50, and 100 \(\mathrm{M_\odot\,pc^{-2}}\). The SILCC project simulation framework accounts for non-equilibrium thermal and chemical processes in the warm and cold ISM. The sink-based star formation and feedback model includes stellar winds, hydrogen-ionising UV radiation, core-collapse supernovae, and cosmic ray (CR) injection and diffusion. The simulations follow the observed relation between \(\Sigma_\mathrm{gas}\) and the star formation rate surface density \(\Sigma_\mathrm{SFR}\). CRs qualitatively change the outflow phase structure. Without CRs, the outflows transition from a two-phase (warm and hot at 1 kpc) to a single-phase (hot at 2 kpc) structure. With CRs, the outflow always has three phases (cold, warm, and hot), dominated in mass by the warm phase. The impact of CRs on mass loading decreases for higher \(\Sigma_\mathrm{gas}\) and the mass loading factors of the CR-supported outflows are of order unity independent of \(\Sigma_\mathrm{SFR}\). Similar to observations, vertical velocity dispersions of the warm ionised medium (WIM) and the cold neutral medium (CNM) correlate with the star formation rate as \(\sigma_\mathrm{z} \propto \Sigma_\mathrm{SFR}^a\), with \(a \sim 0.20\). In the absence of stellar feedback, we find no correlation. The velocity dispersion of the WIM is a factor \(\sim 2.2\) higher than that of the CNM, in agreement with local observations. For \(\Sigma_\mathrm{SFR} \gtrsim 1.5 \times 10^{-2}\,\mathrm{M}_\odot\,\mathrm{yr}^{-1}\,\mathrm{kpc}^{-2}\) the WIM motions become supersonic.