An improved model for the non-linear velocity power spectrum


  • Elise Jennings

    Corresponding author
    1. The Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
    2. The Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA
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The velocity divergence power spectrum is a key ingredient in modelling redshift-space distortion effects on quasi-linear and non-linear scales. We present an improved model for the z= 0 velocity divergence auto and cross power spectrum which was originally suggested by Jennings et al. Using numerical simulations we measure the velocity fields using a Delaunay tessellation and obtain an accurate prediction of the velocity divergence power spectrum on scales k < 1 h Mpc−1. We use this to update the model which is now accurate to 2 per cent for both Pθθ and Pθδ at z= 0 on scales k < 0.65 h Mpc−1 and k < 0.35 h Mpc−1, respectively. We find that the formula for the redshift dependence of the velocity divergence power spectra proposed by Jennings et al. recovers the measured z > 0 P(k) to markedly greater accuracy with the new model. The non-linear Pθθ and Pθδ at z= 1 are recovered accurately to better than 2 per cent on scales k < 0.2 h Mpc−1. Recently, it was shown that the velocity field shows larger differences between modified gravity cosmologies and Λ cold dark matter (ΛCDM) compared to the matter field. An accurate model for the velocity divergence power spectrum, such as the one presented here, is a valuable tool for analysing redshift-space distortion effects in future galaxy surveys and for constraining deviations from general relativity.