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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