Journal Article

The impact of baryonic physics on the shape and radial alignment of substructures in cosmological dark matter haloes

Alexander Knebe, Noam I. Libeskind, Steffen R. Knollmann, Gustavo Yepes, Stefan Gottlöber and Yehuda Hoffman

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 405, issue 2, pages 1119-1128
Published in print June 2010 | ISSN: 0035-8711
Published online June 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16514.x
The impact of baryonic physics on the shape and radial alignment of substructures in cosmological dark matter haloes

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We use two simulations performed within the Constrained Local UniversE Simulation (CLUES) project to study both the shape and radial alignment of (the dark matter component of) subhaloes; one of the simulations is a dark matter only model while the other run includes all the relevant gas physics and star formation recipes. We find that the involvement of gas physics does not have a statistically significant effect on either property – at least not for the most massive subhaloes considered in this study. However, we observe in both simulations including and excluding gas dynamics a (pronounced) evolution of the dark matter shapes of subhaloes as well as of the radial alignment signal since infall time. Further, this evolution is different when positioned in the central and outer regions of the host halo today; while subhaloes tend to become more aspherical in the central 50 per cent of their host’s virial radius, the radial alignment weakens in the central regime while strengthening in the outer parts. We confirm that this is due to tidal torquing and the fact that subhaloes at pericentre move too fast for the alignment signal to respond.

Keywords: methods: N-body simulations; methods: numerical; galaxies: formation; galaxies: haloes

Journal Article.  7898 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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