We measure Redshift-Space Distortions ( RSD ) in the two-point correlation function of a sample of 63 , 163 spectroscopically identified galaxies with z < 0.2 , an epoch where there are currently only limited measurements , from the Sloan Digital Sky Survey ( SDSS ) Data Release 7 Main Galaxy Sample .
Our sample , which we denote MGS , covers 6,813 deg ^ { 2 } with an effective redshift z _ { eff } = 0.15 and is described in our companion paper ( Paper I ) , which concentrates on BAO measurements .
In order to validate the fitting methods used in both papers , and derive errors , we create and analyse 1000 mock catalogues using a new algorithm called picola to generate accurate dark matter fields .
Haloes are then selected using a friends-of-friends algorithm , and populated with galaxies using a Halo-Occupation Distribution fitted to the data .
Using errors derived from these mocks , we fit a model to the monopole and quadrupole moments of the MGS correlation function .
If we assume no Alcock-Paczynski ( AP ) effect ( valid at z = 0.15 for any smooth model of the expansion history ) , we measure the amplitude of the velocity field , f \sigma _ { 8 } , at z = 0.15 to be 0.49 _ { -0.14 } ^ { +0.15 } .
We also measure f \sigma _ { 8 } including the AP effect .
This latter measurement can be freely combined with recent Cosmic Microwave Background results to constrain the growth index of fluctuations , \gamma .
Assuming a background \Lambda CDM cosmology and combining with current Baryon Acoustic Oscillation data we find \gamma = 0.64 \pm 0.09 , which is consistent with the prediction of General Relativity ( \gamma \approx 0.55 ) , though with a slight preference for higher \gamma and hence models with weaker gravitational interactions .