Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies

By J. Oñorbe, M. Boylan-Kolchin, James S. Bullock, P. Hopkins, Duvsan Kerves, C. Faucher-Giguére, E. Quataert, N. Murray. 2015

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We present multiple ultrahigh resolution cosmological hydrodynamic simulations of M_★ ≃ 10^(4–6.3) M_⊙ dwarf galaxies that form within two M_(vir) = 10^(9.5–10) M_⊙ dark matter halo initial conditions. Our simulations rely on the Feedback in Realistic Environments (FIRE) implementation of star formation feedback and were run with high enough force and mass resolution to directly resolve structure on the ∼200 pc scales. The resultant galaxies sit on the M_★ versus M_(vir) relation required to match the Local Group stellar mass function via abundance matching. They have bursty star formation histories and also form with half-light radii and metallicities that broadly match those observed for local dwarfs at the same stellar mass. We demonstrate that it is possible to create a large (∼1 kpc) constant-density dark matter core in a cosmological simulation of an M_★ ≃ 10^(6.3) M_⊙ dwarf galaxy within a typical M_(vir) = 10^(10) M_⊙ halo – precisely the scale of interest for resolving the ‘too big to fail’ problem. However, these large cores are not ubiquitous and appear to correlate closely with the star formation histories of the dwarfs: dark matter cores are largest in systems that form their stars late (z ≲ 2), after the early epoch of cusp building mergers has ended. Our M_★ ≃ 10^4 M_⊙ dwarf retains a cuspy dark matter halo density profile that matches that of a dark-matter-only run of the same system. Though ancient, most of the stars in our ultrafaint form after reionization; the ultraviolet field acts mainly to suppress fresh gas accretion, not to boil away gas that is already present in the protodwarf.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c6b5eee46fbc4386dbba32997076587e9db3c013

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Citations in the corpus

Not so lumpy after all: modelling the depletion of dark matter subhaloes by Milky Way-like galaxies (2017, background): “…in this field (e.g. di Cintio et al. 2011; Governato et al. 2012; Pontzen & Governato 2012; Zolotov et al. 2012; Brooks & Zolotov 2014; Arraki et al. 2014; Sawala et al. 2015; Di Cintio et al. 2014; Oñorbe et al. 2015; Chan et al. 2015; Sawala et al. 2016b; Cui et al. 2016; Wetzel et al. 2016).”
Small scale problems of the $\Lambda$CDM model: a short review (2016, methodology): “[298] found similar results, but for M∗ > 106M galaxies (Figure 7 bottom right panel)7.”
(Star)bursts of FIRE: observational signatures of bursty star formation in galaxies (2015, background): “…dark matter halos because SFR variability on timescales less than the local orbital period of dark matter particles can turn dark matter cusps into cores (Pontzen & Governato 2012, see also Garrison-Kimmel et al. 2013; Di Cintio et al. 2014; Oñorbe et al. 2015; Chan et al. 2015; Read et al. 2016).”
The unexpected diversity of dwarf galaxy rotation curves (2015, background): “…2015, and our discussion below), there is growing consensus that the inner dark matter profiles can, in principle, be reshaped during the formation of a galaxy, even a dark-matterdominated one, in a manner that may depend on its merger history (see e.g. Di Cintio et al. 2014; Oñorbe et al. 2015).”
The Local Group on FIRE: dwarf galaxy populations across a suite of hydrodynamic simulations (2018, background): “…Faucher-Giguère 2018) and overall agreement with a variety of galaxy-scale observables, including the star formation histories of dwarf galaxies (Oñorbe et al. 2015; Wetzel et al. 2016; Fitts et al. 2017); the mass–metallicity (Ma et al. 2016), stellar mass–halo mass (Hopkins et al. 2014,…”
NIHAO – IV: core creation and destruction in dark matter density profiles across cosmic time (2015, background): “…shown that baryons are able to alter thedark matter profile and to create substantial cores (up to∼ 1 kpc) in the dark matter distribution (e.g. Governato et al. 2010, Macciò et al. 2012, Martizzi et al. 2013, Munshi et al. 2013, Di Cintio 2014a,b, Trujillo-Gomez et al. 2015, Oñorbe et al. 2015).”
The impact of baryonic physics on the structure of dark matter haloes: the view from the FIRE cosmological simulations (2015, methodology): “However, for the same halo mass Oñorbe et al. (2015) show that a slightly different star formation history can cause a much larger effect and form a central core with a radius of 1-2 %Rvir.”
Dark matter cores all the way down (2015, background): “…of star formation (e.g. Mashchenko et al. 2008; Governato et al. 2010; Teyssier et al. 2013; Di Cintio et al. 2014; Trujillo-Gomez et al. 2015; Oñorbe et al. 2015; and for a review see Pontzen & Governato 2014), while the physics of such cusp-core transformations is now well understood4…”
BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES (2015, methodology): “Recently, a number of studies (for example, Read & Gilmore 2005; Pontzen & Governato 2012; Governato et al. 2012; Di Cintio et al. 2014; Oñorbe et al. 2015; Chan et al. 2015) have shown that including stellar feedback in simulations can significantly alter dwarf galaxies’ density profiles,…”
Gusty, gaseous flows of FIRE: Galactic winds in cosmological simulations with explicit stellar feedback (2015, background): “The isolated dwarf galaxies m09 and m10 are extensively described in Oñorbe et al. (2015).”
The origin and evolution of the galaxy mass–metallicity relation (2015, background): “The m09 is a low-mass c© 0000 RAS, MNRAS 000, 1–15 isolated dwarf galaxy (comparable to the ultra faint dwarfs around the Milky Way), in which star formation has been shut down since z = 3 by cosmic reionization (Oñorbe et al. 2015).”
Stellar and Quasar Feedback in Concert: Effects on AGN Accretion, Obscuration, and Outflows (2015, methodology): “In a series of papers (Hopkins et al. 2014; Muratov et al. 2015; Oñorbe et al. 2015; van de Voort et al. 2015; Ma et al. 2015b,a; Faucher-Giguere et al. 2015), we showed that, on galactic scales, these models produce a quasi-steady ISM in which molecular clouds form and disperse rapidly, with phase…”
FIRE in the field: Simulating the threshold of galaxy formation (2016, methodology): “…the FIRE-1 code was presented in Hopkins et al. (2014); uses a slightly different cosmology, box size, and starting redshift than the remainder of our simulations. b A version of this halo simulated using the FIRE-1 code was presented in Oñorbe et al. (2015); uses a smaller box size than our…”
FIRE-2 simulations: physics versus numerics in galaxy formation (2017, background): “…of Milky Way-mass galaxies (Wetzel et al. 2016); observed satellite mass functions, rotation curves/kinematics, and cusp/core structure of dwarfs (Oñorbe et al. 2015; Chan et al. 2015; Wheeler et al. 2015, 2017; Wetzel et al. 2016); abundance gradients (El-Badry et al. 2016; Ma et al.…”
Understanding the shape and diversity of dwarf galaxy rotation curves in ΛCDM (2016, background): “Yet this is precisely where stellar feedback affects the gravitational potential (R16; and see Oñorbe et al. 2015), making it challenging to obtain a robust estimate of M200.”