Assessing the accuracy of cosmological parameters estimated from velocity -- density comparisons via simulations

Abstract

A promising method for measuring the cosmological parameter combination fsigma_8 is to compare observed peculiar velocities with peculiar velocities predicted from a galaxy density field using perturbation theory. We use N-body simulations and semi-analytic galaxy formation models to quantify the accuracy and precision of this method. Specifically, we examine a number of technical aspects, including the optimal smoothing length applied to the density field, the use of dark matter halos or galaxies as tracers of the density field, the effect of noise in the halo mass estimates or in the stellar-to-halo mass relation, and the effect of finite survey volumes. We find that for a Gaussian smoothing of 4 Mpc/h, the method has only small systematic biases at the level of 5%. Cosmic variance affects current measurements at the 5% level due to the volume of current redshift data sets.

10 pages, 10 figures. Accepted for publication in MNRAS

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• Peculiar-velocity cosmology with Types Ia and II supernovae
• A local measurement of the growth rate from peculiar velocities and galaxy clustering correlations in the 6dF Galaxy Survey
• Large-scale motions and growth rate from forward-modelling Tully-Fisher peculiar velocities
• Isolating the linear signal when making redshift space distortion measurements
• Peculiar Velocity Reconstruction From Simulations and Observations Using Deep Learning Algorithms
• Biases in velocity reconstruction: investigating the effects on growth rate and expansion measurements in the local universe
• $S_8$ from peculiar velocities: agreement with Planck for Tully--Fisher and supernovae, tension for the fundamental plane