Star Formation in Galaxies between 0.7

We present an analysis of the star formation rate in galaxies between 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 square arcminutes, 37 of which show possible H α emission. We extend the observed H α luminosity function (LF) in this redshift range to luminosities a factor of two fainter than earlier work, and are consistent in the region of overlap. Using the H α LF, we estimate a star formation rate (SFR) density in this redshift range of 0.166M ⊙ yr − 1 Mpc − 3 ( H 0 = 75 kms − 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 H α out to z ≈ 1 . 3.