Bulk Flow and Shear Moments of the SFI++ Survey

TL;DR

This paper measures bulk flow and shear moments from the SFI++ survey to constrain the shape of the velocity power spectrum, finding results consistent with WMAP data and analyzing differences between galaxy types.

Contribution

It introduces a method to estimate the velocity power spectrum shape parameter using peculiar velocity moments from the SFI++ survey, including noise estimation and comparison between galaxy samples.

Findings

Constrained the shape parameter Γ to 0.15^{+0.18}_{-0.08} for groups

Constrained Γ to 0.09^{+0.04}_{-0.04} for field galaxies

Results are consistent with WMAP measurements

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 $\Gamma$ in linear theory using these moments. A likelihood function for $\Gamma$ was found after marginalizing over the power spectrum amplitude $\sigma_8\Omega_m^{0.6}$ using constraints obtained from comparisons between redshift surveys and peculiar velocity data. We have estimated the velocity noise $\sigma_*$ 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 $\Gamma=0.15^{+0.18}_{-0.08}$ for the groups catalogue and $\Gamma=0.09^{+0.04}_{-0.04}$ for the field galaxy catalogue in fair agreement with the value from WMAP.