Journal Article

Shallow dark matter cusps in galaxy clusters

Chervin F. P. Laporte, Simon D. M. White, Thorsten Naab, Mateusz Ruszkowski and Volker Springel

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 424, issue 1, pages 747-753
Published in print July 2012 | ISSN: 0035-8711
Published online July 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21262.x
Shallow dark matter cusps in galaxy clusters

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We study the evolution of the stellar and dark matter components in a galaxy cluster of 1015 M from z= 3 to the present epoch using the high-resolution collisionless simulations of Ruszkowski & Springel. At z= 3 the dominant progenitor haloes were populated with spherical model galaxies with and without accounting for adiabatic contraction. We apply a weighting scheme which allows us to change the relative amount of dark and stellar material assigned to each simulation particle in order to produce luminous properties which agree better with abundance-matching arguments and observed bulge sizes at z= 3. This permits the study of the effect of initial compactness on the evolution of the mass–size relation. We find that for more compact initial stellar distributions the size of the final brightest cluster galaxy grows with mass according to rM2, whereas for more extended initial distributions, rM. Our results show that collisionless mergers in a cosmological context can reduce the strength of inner dark matter cusps with changes in logarithmic slope of 0.3–0.5 at fixed radius. Shallow cusps such as those found recently in several strong lensing clusters thus do not necessarily conflict with cold dark matter, but may rather reflect on the initial structure of the progenitor galaxies, which was shaped at high redshift by their formation process.

Keywords: galaxies: clusters: general; galaxies: elliptical and lenticular, cD; galaxies: evolution; galaxies: formation

Journal Article.  5786 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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