2020/04/30 by Alexandres Lazar, James S. Bullock, Michael Boylan-Kolchin +14 · 1 citation
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Core (optical fiber) #Dark Matter and Cosmic Phenomena #Dark matter #Galaxies: Formation, Evolution, Phenomena #Optics #Physics #astro-ph.GA
paper · pdf · doi:10.1093/mnras/staa2101
27 pages; 19 figures; Accepted by MNRAS
arxiv created 2020/07/08 · openalex publication_date 2020/07/15 · arxiv updated 2020/07/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
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_⋆ ≃ 104.5 M\odot ) to the largest spirals (M_⋆ ≃ 1011 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, rc, 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 rc and other profile parameters as a function of both M⋆ and M⋆/Mhalo. In agreement with past studies, we find that dark matter core formation is most efficient at the characteristic stellar-to-halo mass ratio M⋆/Mhalo ≃ 5 × 10−3, or M⋆ ∼ 109 M\odot , with cores that are roughly the size of the galaxy half-light radius, rc ≃ 1−5 kpc. Furthermore, we find no evidence for core formation at radii \gtrsim 100 \rm pc in galaxies with M⋆/Mhalo < 5 × 10−4 or M_⋆ \lesssim 106 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.