The Impact of Wind Scalings on Stellar Growth and the Baryon Cycle in Cosmological Simulations

Abstract

Many phenomenologically successful cosmological galaxy formation simulations employ kinetic winds to model galactic outflows, a crucial ingredient in obtaining predictions that agree with various observations. Yet systematic studies of how variations in kinetic wind scalings might alter observable galaxy properties are rare. Here we employ GADGET-3 simulations to study how the baryon cycle, stellar mass function, and other galaxy and CGM predictions vary as a function of the assumed outflow speed $v_w$ and the scaling of the mass loading factor $\eta$ with velocity dispersion $\sigma$. We design our fiducial model to reproduce the measured wind properties at 25% of the virial radius from the Feedback In Realistic Environments (FIRE) simulations. We find that a strong dependence of $\eta \sim {\sigma }^5$ in low mass haloes with $\sigma <106\mathrm{km}{\mathrm{s}}^{-1}$ is required to match the faint end of the stellar mass functions at $z>1$. The wind speed also has a major impact, with faster winds significantly reducing wind recycling and heating more halo gas. Both effects result in less stellar mass growth in massive haloes and impact high ionization absorption in halo gas. We cannot simultaneously match the stellar content at $z=2$ and $z=0$ within a single model, suggesting that an additional feedback source such as AGN might be required in massive galaxies at lower redshifts, but the amount needed depends strongly on assumptions regarding the outflow properties. We run a 50 $Mpc/h$, $2\times 576^3$ simulation with our fiducial parameters and show that it matches a range of star-forming galaxy properties at $z\sim 0-2$. In closing, the results from simulations of galaxy formation are much more sensitive to small changes in the feedback implementation than to the hydrodynamic technique.

31 pages, 19 figures, accepted by MNRAS

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Cited by in corpus (6)

• Characterizing mass, momentum, energy and metal outflow rates of multi-phase galactic winds in the FIRE-2 cosmological simulations
• Galactic inflow and wind recycling rates in the EAGLE simulations
• A New Model For Including Galactic Winds in Simulations of Galaxy Formation I: Introducing the Physically Evolved Winds (PhEW) Model
• ELUCID VII: Using Constrained Hydro Simulations to Explore the Gas Component of the Cosmic Web
• Massive Galaxies Impede Massive Outflows
• A New Model For Including Galactic Winds in Simulations of Galaxy Formation II: Implementation of PhEW in Cosmological Simulations