The clustering properties of a well-defined sample of 734 H \alpha emitters at z = 0.845 \pm 0.015 , obtained as part of the Hi- z Emission Line Survey ( HiZELS ) , are investigated .
The spatial correlation function of these H \alpha emitters is very well-described by the power law \xi = ( r / r _ { 0 } ) ^ { -1.8 } , with a real-space correlation , r _ { 0 } , of 2.7 \pm 0.3 h ^ { -1 } Mpc .
The correlation length r _ { 0 } increases strongly with H \alpha luminosity ( L _ { H \alpha } ) , from r _ { 0 } \sim 2 h ^ { -1 } Mpc for the most quiescent galaxies ( star-formation rates of \sim 4 M _ { \odot } yr ^ { -1 } ) , up to r _ { 0 } > 5 h ^ { -1 } Mpc for the brightest galaxies in H \alpha .
The correlation length also increases with increasing rest-frame K -band ( M _ { K } ) luminosity , but the r _ { 0 } -L _ { H \alpha } correlation maintains its full statistical significance at fixed M _ { K } .
At z = 0.84 , star-forming galaxies classified as irregulars or mergers are much more clustered than discs and non-mergers , respectively ; however , once the samples are matched in L _ { H \alpha } and M _ { K } , the differences vanish , implying that the clustering is independent of morphological type at z \sim 1 just as in the local Universe .
The typical H \alpha emitters found at z = 0.84 reside in dark-matter haloes of \approx 10 ^ { 12 } M _ { \odot } , but those with the highest SFRs reside in more massive haloes of \approx 10 ^ { 13 } M _ { \odot } .
The results are compared with those of H \alpha surveys at different redshifts : although the break of the H \alpha luminosity function L _ { H \alpha } ^ { * } evolves by a factor of \sim 30 from z = 0.24 to z = 2.23 , if the H \alpha luminosities at each redshift are scaled by L _ { H \alpha } ^ { * } ( z ) then the correlation lengths indicate that , independently of cosmic time , galaxies with the same ( L _ { H \alpha } ) / L _ { H \alpha } ^ { * } ( z ) are found in dark matter haloes of similar masses .
This not only confirms that the star-formation efficiency in high redshift haloes is higher than locally , but also suggests a fundamental connection between the strong negative evolution of L _ { H \alpha } ^ { * } since z = 2.23 and the quenching of star-formation in galaxies residing within dark-matter haloes significantly more massive than 10 ^ { 12 } M _ { \odot } at any given epoch .