We measure the redshift-space correlation function from a spectroscopic sample of 2783 emission line galaxies from the FastSound survey .
The survey , which uses the Subaru Telescope and covers the redshift ranges of 1.19 < z < 1.55 , is the first cosmological study at such high redshifts .
We detect clear anisotropy due to redshift-space distortions ( RSD ) both in the correlation function as a function of separations parallel and perpendicular to the line of sight and its quadrupole moment .
RSD has been extensively used to test general relativity on cosmological scales at z < 1 .
Adopting a \Lambda CDM cosmology with the fixed expansion history and no velocity dispersion \sigma _ { v } = 0 , and using the RSD measurements on scales above 8 { \hbox { $~ { } h ^ { -1 } $ } { ~ { } Mpc } } , we obtain the first constraint on the growth rate at the redshift , f ( z ) \sigma _ { 8 } ( z ) = 0.482 \pm 0.116 at z \sim 1.4 after marginalizing over the galaxy bias parameter b ( z ) \sigma _ { 8 } ( z ) .
This corresponds to 4.2 \sigma detection of RSD .
Our constraint is consistent with the prediction of general relativity f \sigma _ { 8 } \sim 0.392 within the 1 - \sigma confidence level .
When we allow \sigma _ { v } to vary and marginalize it over , the growth rate constraint becomes f \sigma _ { 8 } = 0.494 ^ { +0.126 } _ { -0.120 } .
We also demonstrate that by combining with the low- z constraints on f \sigma _ { 8 } , high- z galaxy surveys like the FastSound can be useful to distinguish modified gravity models without relying on CMB anisotropy experiments .