Dark matter cores all the way down

By Justin I. Read, O. Agertz, Michelle L. M. Collins. 2015

218 citations recorded by the source corpus.

We use high-resolution simulations of isolated dwarf galaxies to study the physics of dark matter cusp-core transformations at the edge of galaxy formation: M200 = 107-109 M⊙. We work at a resolution (~4 pc minimum cell size; ~250 M⊙ per particle) at which the impact from individual supernovae explosions can be resolved, becoming insensitive to even large changes in our numerical 'sub-grid' parameters. We find that our dwarf galaxies give a remarkable match to the stellar light profile; star formation history; metallicity distribution function; and star/gas kinematics of isolated dwarf irregular galaxies. Our key result is that dark matter cores of size comparable to the stellar half-mass radius r1/2 always form if star formation proceeds for long enough. Cores fully form in less than 4 Gyr for the M200 = 108 M⊙ and ~14 Gyr for the 109 M⊙ dwarf. We provide a convenient two parameter 'coreNFW' fitting function that captures this dark matter core growth as a function of star formation time and the projected stellar half-mass radius. Our results have several implications: (i) we make a strong prediction that if Λcold dark matter is correct, then 'pristine' dark matter cusps will be found either in systems that have truncated star formation and/or at radii r > r1/2; (ii) complete core formation lowers the projected velocity dispersion at r1/2 by a factor of ~2, which is sufficient to fully explain the 'too-big-to-fail problem'; and (iii) cored dwarfs will be much more susceptible to tides, leading to a dramatic scouring of the sub-halo mass function inside galaxies and groups. (Less)

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/28abe336b25aa4859eb9219401e988b3656f8545

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Citations in the corpus

Understanding the shape and diversity of dwarf galaxy rotation curves in ΛCDM (2016, methodology): “At this resolution, we become insensitive to our ‘sub-grid’ numerical parameters, making the simulations substantially more predictive (Read et al. 2016, hereafter R16).”
NIHAO - XI. Formation of ultra-diffuse galaxies by outflows (2016, background): “…cause expansion not only of the central DM distribution in galaxies (e.g. Governato et al. 2010; Di Cintio et al. 2014a,b; Oñorbe et al. 2015; Tollet et al. 2016; Chan et al. 2015; Read et al. 2016), but also of the stellar one (e.g. Teyssier et al. 2013; ElBadry et al. 2016; Dutton et al. 2016).”
Dark matter heats up in dwarf galaxies (2018, methodology): “As discussed in Read et al. (2016a), early infalling dwarfs have their star formation shut down before they can fully transform their cusp to a core.”
Gravitational probes of dark matter physics (2017, background): “As we will see below, the interpretation of the problem, additional systematic uncertainties, and the necessity of either new baryonic or dark-matter-physics solutions are hotly debated [352, 353, 354, 355, 356, 357].”
The stellar mass-halo mass relation of isolated field dwarfs : a critical test of ΛCDM at the edge of galaxy formation (2016, background): “…that resolve the effect of individual supernovae explosions are substantially more predictive (e.g. Oñorbe et al. 2015; Chan et al. 2015; Read et al. 2016a, hereafter R16a); these demonstrate that dark matter cores are an unavoidable prediction of ΛCDM (with baryons) for all low mass…”
FIRE in the field: Simulating the threshold of galaxy formation (2016, background): “…affect the density structure of low-mass galaxies even if the gravitational potential is dark-matter-dominated (Zolotov et al. 2012; Pontzen & Governato 2012; Madau et al. 2014; Chan et al. 2015; Read et al. 2016a; Tollet et al. 2016; see Navarro et al. 1996a for earlier work on this topic).”
(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).”