A Random Walk Model for Dark Matter Halo Concentrations. (arXiv:2006.15231v1 [astro-ph.GA])

A Random Walk Model for Dark Matter Halo Concentrations. (arXiv:2006.15231v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Johnson_T/0/1/0/all/0/1">Turner Johnson</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Benson_A/0/1/0/all/0/1">Andrew J. Benson</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Grin_D/0/1/0/all/0/1">Daniel Grin</a> (1) ((1) Haverford College, (2) Carnegie Institution for Science)

We describe an algorithm for predicting the concentrations of dark matter
halos via a random walk in energy space. Given a full merger tree for a halo,
the total internal energy of each halo in that tree is determined by summing
the internal and orbital energies of progenitor halos. For halos described by
single-parameter density profiles (such as the NFW profile) the energy can be
directly mapped to a scale radius, and so to a concentration. We show that this
model can accurately reproduce the mean of the concentration mass relation
measured in N-body simulations, and reproduces more of the scatter in that
relation than previous models. However, our model underpredicts the kurtosis of
the distribution of N-body concentrations. We test this model by examining both
the autocorrelation of scale radii across time, and the correlations between
halo concentration and spin, and comparing to results measured from
cosmological N-body simulations. In both cases we find that our model closely
matches the N-body results. Our model is implemented within the open source
Galacticus toolkit.

We describe an algorithm for predicting the concentrations of dark matter
halos via a random walk in energy space. Given a full merger tree for a halo,
the total internal energy of each halo in that tree is determined by summing
the internal and orbital energies of progenitor halos. For halos described by
single-parameter density profiles (such as the NFW profile) the energy can be
directly mapped to a scale radius, and so to a concentration. We show that this
model can accurately reproduce the mean of the concentration mass relation
measured in N-body simulations, and reproduces more of the scatter in that
relation than previous models. However, our model underpredicts the kurtosis of
the distribution of N-body concentrations. We test this model by examining both
the autocorrelation of scale radii across time, and the correlations between
halo concentration and spin, and comparing to results measured from
cosmological N-body simulations. In both cases we find that our model closely
matches the N-body results. Our model is implemented within the open source
Galacticus toolkit.

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