A random-walk model for dark matter halo spins. (arXiv:2001.09208v1 [astro-ph.GA])

<a href="http://arxiv.org/find/astro-ph/1/au:+Benson_A/0/1/0/all/0/1">Andrew Benson</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Behrens_C/0/1/0/all/0/1">Christoph Behrens</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Lu_Y/0/1/0/all/0/1">Yu Lu</a> (1) ((1) Carnegie Institution for Science, (2) Institut fur Astrophysik, Georg-August Universitat Gottingen)

We extend the random-walk model of Vitvitska et al. for predicting the spins

of dark matter halos from their merger histories. Using updated merger rates,

orbital parameter distributions, and N-body constraints we show that this model

can accurately reproduce the distribution of spin parameters measured in N-body

simulations when we include a weak correlation between the spins of halos and

the angular momenta of infalling subhalos. We further show that this model is

in approximate agreement with the correlation of the spin magnitude over time

as determined from N-body simulations, while it slightly underpredicts the

correlation in the direction of the spin vector measured from the same

simulations. This model is useful for predicting spins from merger histories

derived from non-N-body sources, thereby circumventing the need for very high

resolution simulations to permit accurate measurements of spins. It may be

particularly relevant to modeling systems which accumulate angular momentum

from halos over time (such as galactic disks)—we show that this model makes

small but significant changes in the distribution of galactic disk sizes

computed using the Galacticus semi-analytic galaxy formation model.

We extend the random-walk model of Vitvitska et al. for predicting the spins

of dark matter halos from their merger histories. Using updated merger rates,

orbital parameter distributions, and N-body constraints we show that this model

can accurately reproduce the distribution of spin parameters measured in N-body

simulations when we include a weak correlation between the spins of halos and

the angular momenta of infalling subhalos. We further show that this model is

in approximate agreement with the correlation of the spin magnitude over time

as determined from N-body simulations, while it slightly underpredicts the

correlation in the direction of the spin vector measured from the same

simulations. This model is useful for predicting spins from merger histories

derived from non-N-body sources, thereby circumventing the need for very high

resolution simulations to permit accurate measurements of spins. It may be

particularly relevant to modeling systems which accumulate angular momentum

from halos over time (such as galactic disks)—we show that this model makes

small but significant changes in the distribution of galactic disk sizes

computed using the Galacticus semi-analytic galaxy formation model.

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