2000AJ....120.2843H

We present an analysis of the star formation rate in galaxies with redshifts in the range 0.7<z<1.8 using Near Infrared Camera and Multi-Object Spectrograph (NICMOS) grism spectral observations. We detect 163 galaxies in an area of ∼4.4 arcmin², 37 of which show possible Hα emission. We extend the observed Hα luminosity function (LF) in this redshift range to luminosities a factor of 2 fainter than earlier work and are consistent in the region of overlap. Using the Hα LF, we estimate a star formation rate (SFR) density in this redshift range of 0.166 M_☉.yr^–1.Mpc^–3 (H₀=75 km.s^–1.Mpc^–1), consistent with other estimates based on emission lines and supporting the order-of-magnitude increase in SFR density between z=0 and z=1. Our measurement of SFR density is a factor of ~2-3 greater than that estimated from UV data, comparable to the factor observed locally, implying little evolution in the relative extinctions between UV and Hα out to z~1.3.