1501.03155
Gusty, gaseous flows of FIRE: galactic winds in cosmological simulations with explicit stellar feedback
Muratov, ... Hopkins, Quataert, Murray
Present an analysis of the galaxy-scale gaseous outflows from the Feedback in Realistic Environments (FIRE) sims. This suite of hydrodynamic cosmological zoom simulations provides a sample of haloes where SF giant molecular clouds are resolved to z=0, and features an explicit stellar feedback model on small scales. In this work, focus on quantifying the gas mass ejected out of galaxies in winds and how this material travels through the halo. Correlate these quantities to star formation in galaxies throughout cosmic history. Simulations reveal that a significant portion of every galaxy's evolution, particularly at high z, is dominated by bursts of SF, which are followed by powerful gusts of galactic outflow that sweep up a large fraction of gas in the ISM and send it through the circumgalactic medium. The dynamical effect of these outflows can significantly limit the amount of SF within the affected galaxy. At low z, however, sufficiently massive glaxies corresponding to L*-progenitors develop stable disks and switch into a continuous and quiescent mode of SF that does not drive outflows into the halo. Find inflow to be more continuous than outflow, although filamentary accretion onto the galaxy can be temporarily disrupted by recently ejected outflows. Using a variety of techniques, measure outflow rates and use them to derive mass-loading factors, and their dependence on circular velocity, halo mass, and stellar mass for a large sample of galaxies in the FIRE simulation suite, spanning four decades in halo mass, six decades in stellar mass, and a range of 4.0 > z > 0. Mass-loading factors for L*-progenitors are eta~=10 at high z, but decrease to eta<<1 at low z.
1501.03280
Solving the puzzle of subhalo spins
Wang, et al
Onions+ suggested, in Investigating the spin parameter distribution of subhaloes in two high resolution isolated halo simulations, that typical subhalo spins are consistently lower than the spin distribution found for field haloes. To further examine this puzzle, analyzed simulations of a cosmo volume with sufficient resolution to resolve a significant subhalo popualtion. Confirm the result of Onions+ and show that the typical spin of a subhalo decreases with decreasing mass and increasing proximity to the host halo center. Interpret this as the growing influence of tidal stripping in removing the outer layers, and hence the higher angular momentum particles, of the subhaloes as they move within the host potential. Investigating the z dependence of this effect, find that the typical subhalo spin is smaller with decreasing z. This indicates a temporal evolution as expected in the tidal stripping scenario.
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