The impact of baryonic physics on the structure of dark matter haloes: the view from the FIRE cosmological simulations

Abstract

We study the distribution of cold dark matter (CDM) in cosmological simulations from the FIRE (Feedback In Realistic Environments) project, for M * ∼ 10 4−11 M galaxies in M h ∼ 10 9−12 M halos. FIRE incorporates explicit stellar feedback in the multi-phase ISM, with energetics from stellar population models. We find that stellar feedback, without "fine-tuned" parameters, greatly alleviates small-scale problems in CDM. Feedback causes bursts of star formation and outflows, altering the DM distribution. As a result, the inner slope of the DM halo profile (α) shows a strong mass dependence: profiles are shallow at M h ∼ 10 10 − 10 11 M and steepen at higher/lower masses. The resulting core sizes and slopes are consistent with observations. This is broadly consistent with previous work using simpler feedback schemes, but we find steeper mass dependence of α, and relatively late growth of cores. Because the star formation efficiency M * /M h is strongly halo mass dependent, a rapid change in α occurs around M h ∼ 10 10 M (M * ∼ 10 6 − 10 7 M ), as sufficient feedback energy becomes available to perturb the DM. Large cores are not established during the period of rapid growth of halos because of ongoing DM mass accumulation. Instead, cores require several bursts of star formation after the rapid buildup has completed. Stellar feedback dramatically reduces circular velocities in the inner kpc of massive dwarfs; this could be sufficient to explain the "Too Big To Fail" problem without invoking non-standard DM. Finally, feedback and baryonic contraction in Milky Way-mass halos produce DM profiles slightly shallower than the Navarro-Frenk-White profile, consistent with the normalization of the observed Tully-Fisher relation.

NIHAO – IV: core creation and destruction in dark matter density profiles across cosmic time

“…1 and its scatter. The parameters of the fitting are reported in Table 3. A similar agreement is also found when comparing our rusults with recent simulations presented by the FIRE collaboration in Chan et al (2015). For example there is a quite remarkable similarity in the peak of the core formation and in the non monotonic response of DM to galaxy formation.…”

NIHAO IX: the role of gas inflows and outflows in driving the contraction and expansion of cold dark matter haloes

“…They found a non-linear dependence between the inner slope and stellar to halo mass. This result has been confirmed with a larger sample of galaxies from NIHAO (Tollet et al 2016), and a small sample of higher resolution galaxies from FIRE (Chan et al 2015). Since we use the same simulations our results are consistent with Di Cintio et al (2014a) and Tollet et al (2016).…”

“…A lower threshold is expected to result in a more uniform star formation history, with fewer starbursts, and hence fewer outflow events with high fout, and thus weaker expansion. However, Dutton et al (2015) found halo expansion that follows the NIHAO results in the progenitors of massive elliptical galaxies using a threshold of n th ∼ 1 cm −3 , and the FIRE simulations (Chan et al 2015) are also consistent with NIHAO (from dwarfs to MW mass haloes) and use a higher threshold of n th > 10 − 100 cm −3 . Thus the halo response does not seem strongly sensitive to the star formation threshold, at least for n th > 1 cm −3 .…”

“…On the scale of dwarf galaxies (M200 ∼ 10 10−11 M⊙), a number of different groups have presented fully cosmological hydrodynamical simulations in which the dark matter halo expands (Mashchenko et al 2008;Governato et al 2012;Trujillo-Gomez et al 2015;Chan et al 2015;Tollet et al 2016). In these simulations stellar feedback was found to drive rapid (sub-dynamical) time variability of the potential.…”

Metal flows of the circumgalactic medium, and the metal budget in galactic haloes

“…Table 1 describes the simulations used in this paper. Our sample includes most of the initial FIRE runs (Hopkins et al 2014) (m09, m10, m11, m12i, m12q, m12v), as well as the z2h runs first introduced in Faucher-Giguère et al (2015) which simulate lowmass Lyman-break galaxies to z = 2, four additional dwarf galaxies run to z = 0 first presented in Chan et al (2015) (m10h1297, m10h1146, m10h573, and m11h383) , and two additional L*-like galaxies (m11.4a and m11.9a) presented in Hafen et al (2016). In this work, we primarily consider the central, most massive galaxy in each simulation, though we use additional galaxies that meet inclusion criteria in Section 3.1.…”