Colours, star formation rates and environments of star-forming and quiescent galaxies at the cosmic noon

Robert Feldmann, Eliot Quataert, Philip F. Hopkins, Claude André Faucher-Giguére, Dušan Kereš

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65 Scopus citations


We analyse the star formation rates (SFRs), colours and dust extinctions of galaxies in massive (1012.5 - 1013.5 M) haloes at z ∼ 2 in high-resolution, cosmological zoom-in simulations as part of the Feedback In Realistic Environments (FIRE) project. The simulations do not model feedback from active galactic nuclei (AGNs) but reproduce well the observed relations between stellar and halo mass and between stellar mass and SFR. About half (a third) of the simulated massive galaxies (massive central galaxies) at z ∼ 2 have broad-band colours classifying them as 'quiescent', and the fraction of quiescent centrals is steeply decreasing towards higher redshift, in agreement with observations. The progenitors of z ∼ 2 quiescent central galaxies are, on average, more massive, have lower specific SFRs and reside in more massive haloes than the progenitors of similarlymassive star-forming centrals. The simulations further predict a morphological mix of galaxies that includes disc-dominated, irregular and early-type galaxies. However, our simulations do not reproduce the reddest of the quiescent galaxies observed at z ∼ 2. We also do not find evidence for a colour bimodality, but are limited by our modest sample size. In our simulations, the star formation activity of central galaxies of moderate mass (Mstar ∼ 1010 - 1011 M) is affected by a combination of two distinct physical processes. Outflows powered by stellar feedback result in a short-lived (>100 Myr), but almost complete, suppression of star formation activity after which many galaxies quickly recover and continue to form stars at normal rates. In addition, galaxies residing in slowly growing haloes tend to experience a moderate reduction of their SFRs ('cosmological starvation'). The relative importance of these processes and AGN feedback is uncertain and will be explored in future work.

Original languageEnglish (US)
Pages (from-to)1050-1072
Number of pages23
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Sep 1 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: haloes
  • Galaxies: high-redshift
  • Galaxies: star formation


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