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FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation

Hopkins, Philip F. and Wetzel, Andrew and Garrison-Kimmel, Shea and Hummels, Cameron and Ma, Xiangcheng and Su, Kung-Yi and Orr, Matthew and Schmitz, Denise and Escala, Ivanna and Sanderson, Robyn and Grudić, Michael Y. and Wheeler, Coral (2018) FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation. Monthly Notices of the Royal Astronomical Society, 480 (1). pp. 800-863. ISSN 0035-8711.

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The Feedback In Realistic Environments (FIRE) project explores feedback in cosmological galaxy formation simulations. Previous FIRE simulations used an identical source code (“FIRE-1”) for consistency. Motivated by the development of more accurate numerics – including hydrodynamic solvers, gravitational softening, and supernova coupling algorithms – and exploration of new physics (e.g. magnetic fields), we introduce “FIRE-2”, an updated numerical implementation of FIRE physics for the GIZMO code. We run a suite of simulations and compare against FIRE-1: overall, FIRE-2 improvements do not qualitatively change galaxy-scale properties. We pursue an extensive study of numerics versus physics. Details of the star-formation algorithm, cooling physics, and chemistry have weak effects, provided that we include metal-line cooling and star formation occurs at higher-than-mean densities. We present new resolution criteria for high-resolution galaxy simulations. Most galaxy-scale properties are robust to numerics we test, provided: (1) Toomre masses are resolved; (2) feedback coupling ensures conservation, and (3) individual supernovae are time-resolved. Stellar masses and profiles are most robust to resolution, followed by metal abundances and morphologies, followed by properties of winds and circum-galactic media (CGM). Central (∼kpc) mass concentrations in massive (>L*) galaxies are sensitive to numerics (via trapping/recycling of winds in hot halos). Multiple feedback mechanisms play key roles: supernovae regulate stellar masses/winds; stellar mass-loss fuels late star formation; radiative feedback suppresses accretion onto dwarfs and instantaneous star formation in disks. We provide all initial conditions and numerical algorithms used.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Hopkins, Philip F.0000-0003-3729-1684
Wetzel, Andrew0000-0003-0603-8942
Garrison-Kimmel, Shea0000-0002-4655-8128
Hummels, Cameron0000-0002-3817-8133
Ma, Xiangcheng0000-0001-8091-2349
Orr, Matthew0000-0003-1053-3081
Schmitz, Denise0000-0001-6297-9312
Sanderson, Robyn0000-0003-3939-3297
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 June 24. Received 2018 June 1; in original form 2017 February 16. Published: 28 June 2018. We thank our editor and referee, Matthieu Schaller, for a number of helpful suggestions. Support for PFH and co-authors was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant #1715847 and CAREER grant #1455342. ARW was supported by a Caltech-Carnegie Fellowship, in part through the Moore Center for Theoretical Cosmology and Physics at Caltech. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, and by NASA through grant NNX15AB22G. The Flatiron Institute is supported by the Simons Foundation. MBK and AF were partially supported by the NSF through grant AST-1517226. MBK also acknowledges support from NASA through HST theory grants (programs AR-12836, AR-13888, AR-13896, and AR-14282) awarded by STScI. DK was supported by NSF Grant AST1412153 and a Cottrell Scholar Award from the Research Corporation for Science Advancement. RF was supported by the Swiss National Science Foundation (grant No. 157591). Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations TG-AST130039 & TG-AST150080 granted by the Extreme Science and Engineering Discovery Environment (XSEDE) and PRAC NSF.1713353 supported by the NSF, and the NASA HEC Program through the NAS Division at Ames Research Center and the NCCS at Goddard Space Flight Center.
Group:TAPIR, Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Caltech-Carnegie FellowshipUNSPECIFIED
Moore Center for Theoretical Cosmology and Physics, CaltechUNSPECIFIED
Simons FoundationUNSPECIFIED
NASA Hubble FellowshipAR-12836
NASA Hubble FellowshipAR-13888
NASA Hubble FellowshipAR-13896
NASA Hubble FellowshipAR-14282
Space Telescope Science InstituteUNSPECIFIED
Research CorporationUNSPECIFIED
Swiss National Science Foundation (SNSF)157591
Subject Keywords:methods: numerical – stars: formation – galaxies: active – galaxies: evolution – galaxies: formation – cosmology: theory
Record Number:CaltechAUTHORS:20180723-104220389
Persistent URL:
Official Citation:Philip F Hopkins, Andrew Wetzel, Dušan Kereš, Claude-André Faucher-Giguère, Eliot Quataert, Michael Boylan-Kolchin, Norman Murray, Christopher C Hayward, Shea Garrison-Kimmel, Cameron Hummels, Robert Feldmann, Paul Torrey, Xiangcheng Ma, Daniel Anglés-Alcázar, Kung-Yi Su, Matthew Orr, Denise Schmitz, Ivanna Escala, Robyn Sanderson, Michael Y Grudić, Zachary Hafen, Ji-Hoon Kim, Alex Fitts, James S Bullock, Coral Wheeler, T K Chan, Oliver D Elbert, Desika Narayanan; FIRE-2 simulations: physics versus numerics in galaxy formation, Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 1, 11 October 2018, Pages 800–863,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88125
Deposited By: Tony Diaz
Deposited On:23 Jul 2018 18:04
Last Modified:13 Aug 2018 22:37

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