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

Oñorbe, Jose and Boylan-Kolchin, Michael and Bullock, James S. and Hopkins, Philip F. and Kereš, Dušan and Faucher-Giguère, Claude-André and Quataert, Eliot and Murray, Norman (2015) Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies. Monthly Notices of the Royal Astronomical Society, 454 (2). pp. 2092-2106. ISSN 0035-8711.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Boylan-Kolchin, Michael0000-0002-9604-343X
Bullock, James S.0000-0003-4298-5082
Hopkins, Philip F.0000-0003-3729-1684
Kereš, Dušan0000-0002-1666-7067
Faucher-Giguère, Claude-André0000-0002-4900-6628
Quataert, Eliot0000-0001-9185-5044
Additional Information:© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 September 4. Received 2015 August 27; in original form 2015 February 6. First published online October 13, 2015. This work used computational resources granted by NASA Advanced Supercomputing (NAS) Division, NASA Center for Climate Simulation, Teragrid, and by the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number OCI-1053575. JO and JSB were supported by NSF grant AST-1009999 and NASA grant NNX09AG01G. JO thanks the financial support of the Fulbright/MICINN Program. JO also thanks the PYNBODY team for making this software publicly available. DK was supported by a Hellman Fellowship and NSF grant AST-1412153. C-AF-G was supported by NSF through grant AST-1412836, by NASA through grant NNX15AB22G, and by Northwestern University funds.
Funding AgencyGrant Number
Fulbright CommissionUNSPECIFIED
Ministerio de Ciencia e Innovación (MICINN)UNSPECIFIED
Hellman FellowshipUNSPECIFIED
Northwestern UniversityUNSPECIFIED
Subject Keywords:methods: numerical – galaxies: dwarf – galaxies: evolution – galaxies: formation – cosmology: theory
Issue or Number:2
Record Number:CaltechAUTHORS:20160205-133222970
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Official Citation:Jose Oñorbe, Michael Boylan-Kolchin, James S. Bullock, Philip F. Hopkins, Dušan Kereš, Claude-André Faucher-Giguère, Eliot Quataert, and Norman Murray Forged in FIRE: cusps, cores and baryons in low-mass dwarf galaxies MNRAS (December 01, 2015) Vol. 454 2092-2106 doi:10.1093/mnras/stv2072 First published online October 13, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64282
Deposited By: George Porter
Deposited On:08 Feb 2016 16:43
Last Modified:15 Nov 2019 04:19

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