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A dark matter profile to model diverse feedback-induced core sizes of ΛCDM haloes

Lazar, Alexandres and Bullock, James S. and Boylan-Kolchin, Michael and Chan, T. K. and Hopkins, Philip F. and Graus, Andrew S. and Wetzel, Andrew and El-Badry, Kareem and Wheeler, Coral and Straight, Maria C. and Kereš, Dušan and Faucher-Giguère, Claude-André and Fitts, Alex and Garrison-Kimmel, Shea (2020) A dark matter profile to model diverse feedback-induced core sizes of ΛCDM haloes. Monthly Notices of the Royal Astronomical Society, 497 (2). pp. 2393-2417. ISSN 0035-8711.

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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 per cent of the halo virial radius. These haloes contain galaxies with masses that range from ultrafaint dwarfs (⁠M⋆ ≃ 10^(4.5) M_⊙⁠) to the largest spirals (⁠M⋆ ≃ 10¹¹ M_⊙⁠) 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⋆ ∼ 10⁹ M_⊙⁠, 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 ≳100 pc in galaxies with M⋆/M_(halo) < 5 × 10⁻⁴ or M⋆ ≲ 10⁶ M_⊙⁠. 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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemGIZMO code ItemData
Lazar, Alexandres0000-0002-6852-6282
Bullock, James S.0000-0003-4298-5082
Boylan-Kolchin, Michael0000-0002-9604-343X
Chan, T. K.0000-0003-2544-054X
Hopkins, Philip F.0000-0003-3729-1684
Wetzel, Andrew0000-0003-0603-8942
El-Badry, Kareem0000-0002-6871-1752
Kereš, Dušan0000-0002-1666-7067
Faucher-Giguère, Claude-André0000-0002-4900-6628
Fitts, Alex0000-0002-8928-6011
Garrison-Kimmel, Shea0000-0002-4655-8128
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 July 7. Received 2020 June 16; in original form 2020 April 22. Published: 17 July 2020. This article was worked to completion during the COVID-19 lock-down and would not have been possible without the labors of our essential workers. We would like to thank the referee for helpful comments on the earlier versions of this article. AL and JSB was supported by the National Science Foundation (NSF) grant AST-1910965. MBK acknowledges support from NSF CAREER award AST-1752913, NSF grant AST-1910346, NASA grant NNX17AG29G, and HST-AR-14282,HST-AR-14554, HST-AR-15006, HST-GO-14191, and HST-GO-15658 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. TKC is supported by STFC astronomy consolidated grant ST/T000244. ASG is supported by the McDonald Observatory at the University of Texas at Austin, through the Harlan J. Smith fellowship. AW received support from NASA through ATP grant 80NSSC18K1097 and HST grants GO-14734, AR-15057, AR-15809, and GO-15902 from STScI; the Heising-Simons Foundation; and a fellowship from the Hellman Foundation. KE is supported by an NSF graduate research fellowship. Support for CW was provided by NASA through the NASA Hubble Fellowship grant #10938 awarded by STScI. DK acknowledges support from NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. Simulations presented in this work utilized resources granted by the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by NSF grant OCI-1053575. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST-1652522; by NASA through grant 17-ATP17-0067; and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. The analysis in this paper depended on the PYTHON packages NUMPY (van der Walt, Colbert & Varoquaux 2011), SCIPY (Oliphant 2007), and MATPLOTLIB (Hunter 2007); We are thankful to the developers of these tools. This research has made intensive use of NASA’s Astrophysics Data System ( and the arXiv eprint service ( Data Availability: The data supporting the plots within this article are available on reasonable request to the corresponding author. A public version of the GIZMO code is available at Additional data including simulation snapshots, initial conditions, and derived data products are available at
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)ST/T000244
McDonald ObservatoryUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Hellman FoundationUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
NASA Hubble Fellowship10938
Cottrell Scholar of Research CorporationUNSPECIFIED
Subject Keywords:galaxies: evolution – galaxies: formation – dark matter
Issue or Number:2
Record Number:CaltechAUTHORS:20200626-150123820
Persistent URL:
Official Citation:Alexandres Lazar, James S Bullock, Michael Boylan-Kolchin, T K Chan, Philip F Hopkins, Andrew S Graus, Andrew Wetzel, Kareem El-Badry, Coral Wheeler, Maria C Straight, Dušan Kereš, Claude-André Faucher-Giguère, Alex Fitts, Shea Garrison-Kimmel, A dark matter profile to model diverse feedback-induced core sizes of ΛCDM haloes, Monthly Notices of the Royal Astronomical Society, Volume 497, Issue 2, September 2020, Pages 2393–2417,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104101
Deposited By: George Porter
Deposited On:26 Jun 2020 22:32
Last Modified:23 Oct 2020 20:06

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