What FIREs up star formation: The emergence of the Kennicutt-Schmidt law from feedback

Matthew E. Orr, Christopher C. Hayward, Philip F. Hopkins, T. K. Chan, Claude André Faucher-Giguère, Robert Feldmann, Dušan Kereš, Norman Murray, Eliot Quataert

Research output: Contribution to journalArticlepeer-review

93 Scopus citations


We present an analysis of the global and spatially resolved Kennicutt-Schmidt (KS) star formation relation in the FIRE (Feedback In Realistic Environments) suite of cosmological simulations, including haloes with z = 0 masses ranging from 1010 to 1013 M.We show that the KS relation emerges and is robustly maintained due to the effects of feedback on local scales regulating star-forming gas, independent of the particular small-scale star formation prescriptions employed. We demonstrate that the time-averaged KS relation is relatively independent of redshift and spatial averaging scale, and that the star formation rate surface density is weakly dependent on metallicity and inversely dependent on orbital dynamical time. At constant star formation rate surface density, the 'cold and dense' gas surface density (gas with T < 300 K and n > 10 cm-3, used as a proxy for the molecular gas surface density) of the simulated galaxies is ~0.5 dex less than observed at ~kpc scales. This discrepancymay arise from underestimates of the local column density at the particle-scale for the purposes of shielding in the simulations. Finally, we show that on scales larger than individual giant molecular clouds, the primary condition that determines whether star formation occurs is whether a patch of the galactic disc is thermally Toomre-unstable (not whether it is self-shielding): once a patch can no longer be thermally stabilized against fragmentation, it collapses, becomes self-shielding, cools, and forms stars, regardless of epoch or environment.

Original languageEnglish (US)
Pages (from-to)3653-3673
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Aug 1 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: star formation
  • Instabilities
  • Opacity -methods: numerical


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