Journal Article

How supernova feedback turns dark matter cusps into cores

Andrew Pontzen and Fabio Governato

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 4, pages 3464-3471
Published in print April 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20571.x
How supernova feedback turns dark matter cusps into cores

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We propose and successfully test against new cosmological simulations a novel analytical description of the physical processes associated with the origin of cored dark matter density profiles. In the simulations, the potential in the central kiloparsec changes on sub‐dynamical time‐scales over the redshift interval 4 > z > 2, as repeated, energetic feedback generates large underdense bubbles of expanding gas from centrally concentrated bursts of star formation. The model demonstrates how fluctuations in the central potential irreversibly transfer energy into collisionless particles, thus generating a dark matter core. A supply of gas undergoing collapse and rapid expansion is therefore the essential ingredient. The framework, based on a novel impulsive approximation, breaks with the reliance on adiabatic approximations which are inappropriate in the rapidly changing limit. It shows that both outflows and galactic fountains can give rise to cusp flattening, even when only a few per cent of the baryons form stars. Dwarf galaxies maintain their core to the present time. The model suggests that constant density dark matter cores will be generated in systems of a wide mass range if central starbursts or active galactic nucleus phases are sufficiently frequent and energetic.

Keywords: galaxies: dwarf; dark matter

Journal Article.  6816 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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