Peculiar velocities into the next generation: cosmological parameters
  from the SFI++ survey
  We present cosmological parameter constraints from the SFI++ galaxy peculiar
velocity survey, the largest galaxy peculiar velocity sample to date. The
analysis is performed by using the gridding method developed in Abate et al.
(2008). We concentrate on constraining parameters which are affected by the
clustering of matter: sigma_8 and the growth index gamma. Assuming a
concordance LCDM model we find sigma_8=0.91+0.22-0.18 and gamma=0.55+0.13-0.14
after marginalising over Omega_m. These constraints are consistent with, and
have similar constraining power to, the same constraints from other current
data sets which use different methods. Recently there have been several claims
that the peculiar velocity measurements do not agree with LCDM. We find instead
although a higher value of sigma_8 and a lower value of Omega_m are preferred,
the values are still consistent when compared with WMAP5. We note that although
our analysis probes a variety of scales, the constraints will be dominated by
the smaller scales, which have the smallest uncertainties. These results show
that peculiar velocity analysis is a vital probe of cosmology, providing
competitive constraints on parameters such as sigma_8. Its sensitivity to the
derivative of growth function, particularly down to redshift zero, means it can
provide a vital low redshift anchor on the evolution of structure formation.
The importance of utilising different probes with varying systematics is also
an essential requirement for providing a consistency check on the best-fitting
cosmological model.
