The Hα-based Star Formation Rate Density of the Universe at z = 0.84

Abstract

We present the results of an Hα 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 165 Hα emitters in the extended Groth strip and GOODS-N fields with L(H α) > 10⁴¹ ergs s^-1. We compute the Hα 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 α) = 1.5 mag. Adopting Hα as a surrogate for the instantaneous SFR, we measure an extinction-corrected SFR density of 0.17^{+ 0.03}_-0.03 M_⊙ yr^-1 Mpc^-3. Combining this result to our prior measurements at z = 0.02, 0.24, and 0.40, we derive an Hα-based evolution of the SFR density proportional to (1 + z)^β with β = 3.8 +/- 0.5. This evolution is consistent with that derived by other authors using different SFR tracers.