The growth rate of cosmic structure from peculiar velocities at low and high redshifts

Understand

Peculiar velocities are an important probe of the growth rate of mass density fluctuations in the Universe.

• Most previous studies have focussed exclusively on measuring peculiar velocities at intermediate ($0.2 < z < 1$) redshifts using statistical redshift-space distortions.
• Here we emphasize the power of peculiar velocities obtained directly from distance measurements at low redshift ($z \lesssim 0.05$), and show that these data break the usual degeneracies in the \Omega_{m,0} -- $\sigma_{8,0}$ parameter space.
• Using only peculiar velocity data, we find $\Omega_{m,0} = 0.259\pm0.045$ and $\sigma_{8,0} = 0.748\pm0.035$.