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FIRE-2 simulations: Physics versus numerics in galaxy formation

  • Author(s): Hopkins, PF
  • Wetzel, A
  • Kereš, D
  • Faucher-Giguère, CA
  • Quataert, E
  • Boylan-Kolchin, M
  • Murray, N
  • Hayward, CC
  • Garrison-Kimmel, S
  • Hummels, C
  • Feldmann, R
  • Torrey, P
  • Ma, X
  • Anglés-Alcázar, D
  • Su, KY
  • Orr, M
  • Schmitz, D
  • Escala, I
  • Sanderson, R
  • Grudić, MY
  • Hafen, Z
  • Kim, JH
  • Fitts, A
  • Bullock, JS
  • Wheeler, C
  • Chan, TK
  • Elbert, OD
  • Narayanan, D
  • et al.
Abstract

© 2018 The Author(s). 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. Central (~kpc) mass concentrations in massive (> L*) galaxies are sensitive to numerics (via trapping/recycling of winds in hot haloes). Multiple feedback mechanisms play key roles: supernovae regulate stellar masses/winds; stellar mass-loss fuels late star formation; radiative feedback suppresses accretion on to dwarfs and instantaneous star formation in discs. We provide all initial conditions and numerical algorithms used.

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