Papers › A semi-analytic model of pairwise velocity distribution between dark matter halos
A semi-analytic model of pairwise velocity distribution between dark matter halos
Masato Shirasaki, Eric M. Huff, Katarina Markovic, Jason D. Rhodes
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We study the probability distribution function (PDF) of relative velocity between two different dark matter halos (i.e. pairwise velocity) with a set of high-resolution cosmological N-body simulations. We investigate the pairwise velocity PDFs over a wide range of halo masses of 10^(12.5-15) h⁻¹M_⊙ and redshifts of 0<z<1. At a given set of masses, redshift and the separation length between two halos, our model requires three parameters to set the pairwise velocity PDF, whereas previous non-Gaussian models in the literature assume four or more free parameters. At the length scales of r=5-40 [h⁻¹ Mpc], our model predicts the mean and dispersion of the pairwise velocity for dark matter halos with their masses of 10^(12.5-13.5) [h⁻¹M_⊙] at 0.3 < z < 1 with a 5%-level precision, while the model precision reaches a 20% level (mostly a 10% level) for other masses and redshifts explored in the simulations. We demonstrate that our model of the pairwise velocity PDF provides an accurate mapping of the two-point clustering of massive-galaxy-sized halos at the scales of O(10) h⁻¹Mpc between redshift and real space for a given real-space correlation function. For a mass-limited halo sample with their masses greater than 10^(13.5) h⁻¹M_⊙ at z=0.55, our model can explain the monopole and quadropole moments of the redshift-space two-point correlations with a precision better than 5% at the scales of 5-40 and 10-30 h⁻¹Mpc, respectively. Our model of the pairwise velocity PDF will give a detailed explanation of statistics of massive galaxies at the intermediate scales in redshift surveys, including the non-linear redshift-space distortion effect in two-point correlation functions and the measurements of the kinematic Sunyaev-Zel'dovich effect.
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