Journal Article

Properties of dark matter haloes and their correlations: the lesson from principal component analysis

Ramin A. Skibba and Andrea V. Macciò

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 416, issue 3, pages 2388-2400
Published in print September 2011 | ISSN: 0035-8711
Published online September 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19218.x
Properties of dark matter haloes and their correlations: the lesson from principal component analysis

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We study the correlations between the structural parameters of dark matter haloes using principal component analysis. We consider a set of eight parameters, six of which are commonly used to characterize dark matter halo properties: mass, concentration, spin, shape, overdensity and the angle (ΦL) between the major axis and the angular momentum vector. Two additional parameters (xoff and ρrms) are used to describe the degree of ‘relaxedness’ of the halo. We find that we can account for much of the variance of these properties with halo mass and concentration, on the one hand, and halo relaxedness on the other. None the less, three principal components are usually required to account for most of the variance. We argue that halo mass is not as dominant as expected, which is a challenge for halo occupation models and semi-analytic models that assume that mass determines other halo (and galaxy) properties. In addition, we find that the angle ΦL is not significantly correlated with other halo parameters, which may present a difficulty for models in which galaxy discs are oriented in haloes in a particular way. Finally, at fixed mass, we find that a halo’s environment (quantified by the large-scale overdensity) is relatively unimportant.

Keywords: gravitation; methods: numerical; methods: statistical; galaxies: haloes; cosmology: theory; dark matter

Journal Article.  9828 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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