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Dark matter heats up in dwarf galaxies

Read, J I, Walker, M G and Steger, P (2019) Dark matter heats up in dwarf galaxies Monthly Notices of the Royal Astronomical Society, 484 (1). pp. 1401-1420.

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Abstract

Gravitational potential fluctuations driven by bursty star formation can kinematically ‘heat up’ dark matter at the centres of dwarf galaxies. A key prediction of such models is that, at a fixed dark matter halo mass, dwarfs with a higher stellar mass will have a lower central dark matter density. We use stellar kinematics and HI gas rotation curves to infer the inner dark matter densities of eight dwarf spheroidal and eight dwarf irregular galaxies with a wide range of star formation histories. For all galaxies, we estimate the dark matter density at a common radius of 150 pc, <sub>ρDM</sub>(150pc)⁠. We find that our sample of dwarfs falls into two distinct classes. Those that stopped forming stars over 6 Gyr ago favour central densities ρDM(150pc)>10<sup>8</sup> M⊙ kpc−3, consistent with cold dark matter cusps, while those with more extended star formation favour ρDM(150pc)<10<sup>8</sup> M⊙ kpc−3, consistent with shallower dark matter cores. Using abundance matching to infer pre-infall halo masses, M200, we show that this dichotomy is in excellent agreement with models in which dark matter is heated up by bursty star formation. In particular, we find that ρDM(150pc) steadily decreases with increasing stellar mass-to-halo mass ratio, M*/M<sub>200</sub>. Our results suggest that, to leading order, dark matter is a cold, collisionless, fluid that can be kinematically ‘heated up’ and moved around.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
Read, J Ij.read@surrey.ac.uk
Walker, M G
Steger, P
Date : March 2019
DOI : 10.1093/mnras/sty3404
Copyright Disclaimer : © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record - J I Read, M G Walker, P Steger; Dark matter heats up in dwarf galaxies, Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 1, 21 March 2019, Pages 1401–1420 - is available online at: https://doi.org/10.1093/mnras/sty3404
Uncontrolled Keywords : Galaxies: dwarf. Galaxies: haloes. Galaxies: kinematics and dynamics. Galaxies: star formation. Cosmology: observations. Dark matter.
Depositing User : Clive Harris
Date Deposited : 31 Jan 2019 15:54
Last Modified : 31 Jan 2019 15:54
URI: http://epubs.surrey.ac.uk/id/eprint/850337

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