A dark matter profile to model diverse feedback-induced core sizes of ΛCDM haloes. Issue 2 (17th July 2020)

• Record Type: Journal Article
• Authors: Lazar, Alexandres; Bullock, James S; Boylan-Kolchin, Michael; Chan, T K; Hopkins, Philip F; Graus, Andrew S; Wetzel, Andrew; El-Badry, Kareem; Wheeler, Coral; Straight, Maria C; Kereš, Dušan; Faucher-Giguère, Claude-André; Fitts, Alex; Garrison-Kimmel, Shea
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 2(2020)
• Page Start: 2393
• Page End: 2417
• Publication Date: 2020-07-17
• Subjects: galaxies: evolution -- galaxies: formation -- dark matter; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa2101
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We analyse the cold dark matter density profiles of 54 galaxy haloes simulated with Feedback In Realistic Environments (FIRE)-2 galaxy formation physics, each resolved within $0.5{{\ \rm per\ cent}}$ of the halo virial radius. These haloes contain galaxies with masses that range from ultrafaint dwarfs ($M_\star \simeq 10^{4.5}\, \mathrm{M}_{\odot }$ ) to the largest spirals ($M_\star \simeq 10^{11}\, \mathrm{M}_{\odot }$ ) and have density profiles that are both cored and cuspy. We characterize our results using a new, analytic density profile that extends the standard two-parameter Einasto form to allow for a pronounced constant density core in the resolved innermost radius. With one additional core-radius parameter, r c, this three-parameter core-Einasto profile is able to characterize our feedback-impacted dark matter haloes more accurately than other three-parameter profiles proposed in the literature. To enable comparisons with observations, we provide fitting functions for r c and other profile parameters as a function of both M ⋆ and M ⋆ / M halo . In agreement with past studies, we find that dark matter core formation is most efficient at the characteristic stellar-to-halo mass ratio M ⋆ / M halo ≃ 5 × 10 −3, or $M_{\star } \sim 10^9 \, \mathrm{M}_{\odot }$, with cores that are roughly the size of the galaxy half-light radius, r c ≃ 1−5 kpc. Furthermore, we find no evidence for core formation at radii $\gtrsim 100\ \rm pc$ in galaxies with M ⋆ / M halo < 5 × 10 −4 or $M_\star \lesssim 10^6 \, \mathrm{M}_{\odot }$ . For Milky Way-size galaxies, baryonic contraction often makes haloes significantly more concentrated and dense at the stellar half-light radius than DMO runs. However, even at the Milky Way scale, FIRE-2 galaxy formation still produces small dark matter cores of ≃ 0.5−2 kpc in size. Recent evidence for a ∼2 kpc core in the Milky Way's dark matter halo is consistent with this expectation.