Gusty, gaseous flows of FIRE: galactic winds in cosmological simulations with explicit stellar feedback
We present an analysis of the galaxy-scale gaseous outflows from the Feedback in Realistic Environments (FIRE) simulations. This suite of hydrodynamic cosmological zoom simulations resolves formation of star-forming giant molecular clouds to z = 0, and features an explicit stellar feedback model on small scales. Our simulations reveal that high-redshift galaxies undergo bursts of star formation followed by powerful gusts of galactic outflows that eject much of the interstellar medium and temporarily suppress star formation. At low redshift, however, sufficiently massive galaxies corresponding to L* progenitors develop stable discs and switch into a continuous and quiescent mode of star formation that does not drive outflows far into the halo. Mass-loading factors for winds in L* progenitors are η ≈ 10 at high redshift, but decrease to η ≪ 1 at low redshift. Although lower values of η are expected as haloes grow in mass over time, we show that the strong suppression of outflows with decreasing redshift cannot be explained by mass evolution alone. Circumgalactic outflow velocities are variable and broadly distributed, but typically range between one and three times the circular velocity of the halo. Much of the ejected material builds a reservoir of enriched gas within the circumgalactic medium, some of which could be later recycled to fuel further star formation. However, a fraction of the gas that leaves the virial radius through galactic winds is never regained, causing most haloes with mass M_h ≤ 10^(12) M_⊙ to be deficient in baryons compared to the cosmic mean by z = 0.
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 September 11. Received 2015 September 10; in original form 2015 January 12. First published online October 13, 2015. We thank Tsang-Keung Chan, Xiangcheng Ma, Daniel Anglés-Alcázar, Freeke van de Voort, Robert Feldmann, Chris Hayward, and Michael Anderson for various constructive suggestions. We thank Romeel Davé for providing details on wind implementation for our simulation comparison section. We thank the anonymous referee for providing suggestions that improved this work. DK was supported by a Hellman Fellowship and NSF grant AST-1412153, and by funds from the University of California San Diego. Support for PFH was provided by the Gordon and Betty Moore Foundation through Grant 776 to the Caltech Moore Center for Theoretical Cosmology and Physics, by the Alfred P. Sloan Foundation through Sloan Research Fellowship BR2014-022, and by NSF through grant AST-1411920. C-AF-G was supported by NSF through grant AST-1412836, by NASA through grant NNX15AB22G, and by Northwestern University funds. EQ was supported by NASA ATP grant 12-APT12-0183, a Simons Investigator award from the Simons Foundation, the David and Lucile Packard Foundation, and the Thomas Alison Schneider Chair in Physics at UC Berkeley. The simulations analysed in this paper were run on XSEDE computational resources (allocations TG-AST120025, TG-AST130039, and TG-AST140023). We would like to thank the Simons Foundation and the participants of the Galactic Super Winds symposium for stimulating discussions. We would also like to thank the Kavli Institute for Theoretical Physics and the participants of the Physics of Star Formation Feedback program for interactions that improved this work.
Published - MNRAS-2015-Muratov-2691-713.pdf