We present new measurements of the H \alpha luminosity function ( LF ) and star formation rate ( SFR ) volume density for galaxies at z \sim 0.8 .
Our analysis is based on 1.18 \mu m narrowband data from the NEWFIRM H \alpha ( NewH \alpha ) Survey , a comprehensive program designed to capture deep samples of intermediate redshift emission-line galaxies using narrowband imaging in the near-infrared .
The combination of depth ( \approx 1.9 \times 10 ^ { -17 } erg s ^ { -1 } cm ^ { -2 } in H \alpha at 3 \sigma ) and areal coverage ( 0.82 deg ^ { 2 } ) of the 1.18 \mu m observations complements other recent H \alpha studies at similar redshifts , and enables us to minimize the impact of cosmic variance and place robust constraints on the shape of the LF .
The present sample contains 818 NB118 excess objects , 394 of which are selected as H \alpha emitters .
Optical spectroscopy has been obtained for 62 % of the NB118 excess objects .
Empirical optical broadband color classification is used to sort the remainder of the sample .
A comparison of the LFs constructed for the four individual fields covered by the observations reveals significant cosmic variance , emphasizing that multiple , widely separated observations are required for such analyses .
The dust-corrected LF is well described by a Schechter function with L _ { \star } = 10 ^ { 43.00 \pm 0.52 } erg s ^ { -1 } , \Phi _ { \star } = 10 ^ { -3.20 \pm 0.54 } Mpc ^ { -3 } , and \alpha = -1.6 \pm 0.19 .
We compare our H \alpha LF and SFR density to those at z \lesssim 1 , and find a rise in the SFR density \propto ( 1 + z ) ^ { 3.4 } , which we attribute to significant L _ { \star } evolution .
Our H \alpha SFR density of 10 ^ { -1.00 \pm 0.18 } M _ { \sun } yr ^ { -1 } Mpc ^ { -3 } is consistent with UV and [ O ii ] measurements at z \sim 1 .
We discuss how these results compare to other H \alpha surveys at z \sim 0.8 , and find that the different methods used to determine survey completeness can lead to inconsistent results .
This suggests that future surveys probing fainter luminosities are needed , and more rigorous methods of estimating the completeness should be adopted as standard procedure ( for example , with simulations which try to simultaneously reproduce the observed H \alpha LF and equivalent width distributions ) .