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Dark matter cores all the way down

Read, J. I.; Agertz, O. LU and Collins, M. L M (2016) In Monthly Notices of the Royal Astronomical Society 459(3). p.2573-2590
Abstract

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... (More)

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.

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author
organization
publishing date
type
Contribution to journal
publication status
published
keywords
Dark matter, Galaxies: dwarf, Galaxies: haloes, Galaxies: kinematics and dynamics, Methods: numerical
in
Monthly Notices of the Royal Astronomical Society
volume
459
issue
3
pages
18 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:84975092121
ISSN
0035-8711
DOI
10.1093/mnras/stw713
language
English
LU publication?
yes
id
8a1d5525-e4e5-4436-bc3b-83d3f6c2ddb5
date added to LUP
2016-08-16 22:54:43
date last changed
2017-07-23 05:16:51
@article{8a1d5525-e4e5-4436-bc3b-83d3f6c2ddb5,
  abstract     = {<p>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: M<sub>200</sub> = 10<sup>7</sup>-10<sup>9</sup> M<sub>⊙</sub>. We work at a resolution (~4 pc minimum cell size; ~250 M<sub>⊙</sub> 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 r<sub>1/2</sub> always form if star formation proceeds for long enough. Cores fully form in less than 4 Gyr for the M<sub>200</sub> = 10<sup>8</sup> M<sub>⊙</sub> and ~14 Gyr for the 10<sup>9</sup> M<sub>⊙</sub> 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 &gt; r<sub>1/2</sub>; (ii) complete core formation lowers the projected velocity dispersion at r<sub>1/2</sub> 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.</p>},
  author       = {Read, J. I. and Agertz, O. and Collins, M. L M},
  issn         = {0035-8711},
  keyword      = {Dark matter,Galaxies: dwarf,Galaxies: haloes,Galaxies: kinematics and dynamics,Methods: numerical},
  language     = {eng},
  month        = {07},
  number       = {3},
  pages        = {2573--2590},
  publisher    = {Wiley-Blackwell},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Dark matter cores all the way down},
  url          = {http://dx.doi.org/10.1093/mnras/stw713},
  volume       = {459},
  year         = {2016},
}