The Hα-based star formation rate density of the universe at z=0.84

We present the results of an H alpha near-infrared narrowband survey searching for star-forming galaxies at redshift z = 0.84. This work is an extension of our previous narrowband studies in the optical at lower redshifts. After removal of stars and redshift interlopers ( using spectroscopic and photometric redshifts), we build a complete sample of 165H alpha emitters in the extended Groth strip and GOODS-N fields with L(H alpha) > 10(41) ergs s(-1). We compute the H alpha luminosity function at z 0: 84 after corrections for [N II] flux contamination, extinction, systematic errors, and incompleteness. Our sources present an average dust extinction of A(H alpha) 1.5 mag. Adopting H alpha as a surrogate for the instantaneous SFR, we measure an extinction-corrected SFR density of 0.17(-0.03)(+0.03) M-circle dot yr(-1) Mpc(-3). Combining this result to our prior measurements at z = 0.02, 0.24, and 0.40, we derive an H alpha-based evolution of the SFR density proportional to (1 + z)(beta) with beta = 3.8 +/- 0.5. This evolution is consistent with that derived by other authors using different SFR tracers.