FIRE in the field: Simulating the threshold of galaxy formation

Alex Fitts, Michael Boylan-Kolchin, Oliver D. Elbert, James S. Bullock, Philip F. Hopkins, Jose Oñorbe, Andrew Wetzel, Coral Wheeler, Claude André Faucher-Giguère, Dušan Kereš, Evan D. Skillman, Daniel R. Weisz

Research output: Contribution to journalArticlepeer-review

121 Scopus citations


We present a suite of 15 cosmological zoom-in simulations of isolated dark matter haloes, all with masses of Mhalo ≈ 1010M at z = 0, in order to understand the relationship among halo assembly, galaxy formation and feedback's effects on the central density structure in dwarf galaxies. These simulations are part of the Feedback in Realistic Environments (FIRE) project and are performed at extremely high resolution (mbaryon = 500M, mdm = 2500M). The resultant galaxies have stellar masses that are consistent with rough abundance matching estimates, coinciding with the faintest galaxies that can be seen beyond the virial radius of the Milky Way (M*/M ≈ 105 - 107). This non-negligible spread in stellar mass at z = 0 in haloes within a narrow range of virial masses is strongly correlated with central halo density or maximum circular velocity Vmax, both of which are tightly linked to halo formation time. Much of this dependence of M* on a second parameter (beyond Mhalo) is a direct consequence of the Mhalo ~ 1010M mass scale coinciding with the threshold for strong reionization suppression: the densest, earliest-forming haloes remain above the UV-suppression scale throughout their histories while late-forming systems fall below the UV-suppression scale over longer periods and form fewer stars as a result. In fact, the latest-forming, lowest-concentration halo in our suite fails to form any stars. Haloes that form galaxies with M ≳ 2 × 106 M have reduced central densities relative to dark-matter-only simulations, and the radial extent of the density modifications is well-approximated by the galaxy half-mass radius r1/2. Lower-mass galaxies do not modify their host dark matter haloes at the mass scale studied here. This apparent stellar mass threshold of M ≈ 2 × 106-2 × 10-4 Mhalo is broadly consistent with previous work and provides a testable prediction of FIRE feedback models in Λcold dark matter.

Original languageEnglish (US)
Pages (from-to)3547-3562
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Nov 1 2017

Bibliographical note

Funding Information:
MBK and AF acknowledge support from the National Science Foundation (grant AST-1517226). MBK was also partially supported by NASA through HST theory grants (programmes AR-12836, AR-13888, AR-13896, and AR-14282) awarded by the Space Telescope Science Institute (STScI), which is operated by theAssociation ofUniversities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. JSB and ODE were supported byNSF AST-1518291, HST-AR-14282 andHST-AR-13888. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant 1411920 and CAREER grant 1455342. AW was supported by a Caltech-Carnegie Fellowship, in part through the Moore Center for Theoretical Cosmology and Physics at Caltech, and by NASA through grant HST-GO-14734 from STScI. DK was supported by NSF grant AST-1412153, a Cottrell Scholar award, and funds from the University of California, San Diego. CAFG was supported by NSF through grants AST-1412836 and AST-1517491, by NASA through grant NNX15AB22G, and by STScI through grant HST-AR-14293.001-A. This work used computational resources of the University of Maryland, The University of Texas at Austin and the Texas Advanced Computing Center (TACC;, the NASA Advanced Supercomputing (NAS) Division and the NASA Center for Climate Simulation (NCCS) through allocations SMD-15-5902, SMD-15-5904, SMD-16-7043 and SMD-16-6991, and the Extreme Science and Engineering Discovery Environment (XSEDE, via allocations TG-AST110035, TG-AST130039 and TG-AST140080), which is supported by National Science Foundation grant number OCI-1053575

Publisher Copyright:
© 2017 The Authors.


  • Dark matter
  • Galaxies: dwarf
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: star formation
  • Galaxies: structure


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