Galaxies on FIRE (Feedback In Realistic Environments): stellar feedback explains cosmologically inefficient star formation

Abstract

We present a series of high-resolution cosmological simulations 1 of galaxy formation to z = 0, spanning halo masses ∼ 10 8 − 10 13 M , and stellar masses ∼ 10 4 − 10 11 M . Our simulations include fully explicit treatment of the multi-phase ISM & stellar feedback. The stellar feedback inputs (energy, momentum, mass, and metal fluxes) are taken directly from stellar population models. These sources of feedback, with zero adjusted parameters, reproduce the observed relation between stellar and halo mass up to M halo ∼ 10 12 M . We predict weak redshift evolution in the M * − M halo relation, consistent with current constraints to z > 6. We find that the M * − M halo relation is insensitive to numerical details, but is sensitive to feedback physics. Simulations with only supernova feedback fail to reproduce observed stellar masses, particularly in dwarf and high-redshift galaxies: radiative feedback (photo-heating and radiation pressure) is necessary to destroy GMCs and enable efficient coupling of later supernovae to the gas. Star formation rates agree well with the observed Kennicutt relation at all redshifts. The galaxy-averaged Kennicutt relation is very different from the numerically imposed law for converting gas into stars, and is determined by self-regulation via stellar feedback. Feedback reduces star formation rates and produces reservoirs of gas that lead to rising late-time star formation histories, significantly different from halo accretion histories. Feedback also produces large short-timescale variability in galactic SFRs, especially in dwarfs. These properties are not captured by common "sub-grid" wind models.

Galactic r-process enrichment by neutron star mergers in cosmological simulations of a Milky Way-mass galaxy

“…This work is part of the Feedback in Realistic Environments (FIRE) project 1 (Hopkins et al 2013b), which consists of several cosmological 'zoom-in' simulations. Here we make use of galaxy m12i, a galaxy with mass similar to the Milky Way at z = 0.…”

“…62 on average. The FIRE simulations include an implementation of stellar feedback by supernovae, radiation pressure, stellar winds, and photo-ionization and photo-electric heating (see Hopkins et al 2013b and references therein for details). For the purposes of the present paper, we emphasize that these simulations produce galaxies with stellar masses reasonably consistent with observations over a wide range of dark matter halo masses.…”

“…Measured within the central 20 kpc at z = 0, the star formation rate is about 3 M⊙yr −1 , the stellar mass is 3 × 10 10 M⊙, the total gas mass is 9 × 10 9 M⊙, and the mass of the star-forming gas is 9 × 10 8 M⊙. We have repeated our analysis for more disc-dominated as well as for more bulge-dominated galaxies within the FIRE sample (Hopkins et al 2013b) and found our results for the r-process abundances to be very similar.…”

Star formation sustained by gas accretion

“…This paper gives an overview of this rapidly evolving field, emphasizing the role of metal-poor gas accretion to sustain star formation in the local universe. We limit ourselves to the global picture, leaving aside details about star-formation processes Gnedin et al 2014), stellar and active galactic nucleus (AGN) feedback (Silich et al 2010;Hopkins et al 2013a;Trujillo-Gomez et al 2013), secular evolution (Binney 2013;Kormendy 2013), dense cluster environments (Santini 2011;Kravtsov and Borgani 2012), and the growth of black holes (BH) through cosmic gas accretion (Husemann et al 2011;Chen et al 2013). Other recent reviews covering cosmic gas accretion from different perspectives are in Sancisi et al (2008), Fig.…”

Spatially adaptive radiation-hydrodynamical simulations of galaxy formation during cosmological reionization

“…However, the ejection of gas may open additional low-density channels through which ionizing photons may escape the ISM more easily, thus making it easier for galaxies to reionize the IGM (e.g., Yajima et al 2009;Wise & Cen 2009;Paardekooper et al 2011;. The suppression of star formation by SNe may be amplified in a nonlinear manner by the feedback from photoheating Finlator, Davé,Özel 2011;Hopkins et al 2013). Locally, SNe may also increase the rates at which stars form as interstellar gas is compressed to star-forming densities in colliding SN shocks (e.g., Geen, Slyz, & Devriendt 2013).…”