Bulk flow and shear moments of the SFI++ survey

Abstract

We find the nine bulk flow and shear moments from the SFI++ survey, as well as for subsamples of group and field galaxies. We constrain the velocity power spectrum shape parameter Γ in linear theory using these moments. A likelihood function for Γ was found after marginalizing over the power spectrum amplitude σ8Ω0.6m using constraints obtained from comparisons between redshift surveys and peculiar velocity data. We have estimated the velocity noise σ* from the data since without it our results may be biased. We also performed a statistical analysis of the difference between the field and group catalogues and found that the results from each reflect the same underlying large-scale flows. We found that we can constrain the power spectrum shape parameter to be Γ = 0.15+0.18-0.08 for the groups catalogue and Γ = 0.09+0.04-0.04 for the field galaxy catalogue in fair agreement with the value from Wilkinson Microwave Anisotropy Probe. © 2008 The Authors.