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Optical spectra of 14 emission-line galaxies representative of the 1999NICMOS parallel grism Ha survey of McCarthy et al. are presented. Of the 14, 9have emission lines confirming the redshifts found in the grism survey. Thehigher resolution of our optical spectra improves the redshift accuracy by afactor of 5. The [O II]/Ha values of our sample are found to be more than twotimes lower than expected from Jansen et al. This [O II]/Ha ratio discrepancyis most likely explained by additional reddening in our Ha-selected sample [onaverage, as much as an extra E(B-V) = 0.6], as well as to a possible strongerdependence of the [O II]/Ha ratio on galaxy luminosity than is found in localgalaxies. The result is that star formation rates (SFRs) calculated from [OII]3727 emission, uncorrected for extinction, are found to be on average 4 +/-2 times lower than the SFRs calculated from Ha emission. Classification ofemission-line galaxies as starburst or Seyfert galaxies based on comparison ofthe ratios [O II]/Hb and [Ne III]3869/Hb is discussed. New Seyfert 1diagnostics using the Ha line luminosity, H-band absolute magnitude, and Haequivalent widths are also presented. One galaxy is classified as a Seyfert 1based on its broad emission lines, implying a comoving number density forSeyfert 1s of 2.5{+5.9, -2.1} times 10^{-5} Mpc^{-3}. This commoving numberdensity is a factor of 2.4{+5.5,-2.0} times higher than estimated by othersurveys.Comment: 51 pages, 18 figures; Accepted for publication in the Astrophysical  Journal; Revised version with minor changes and an additional reference which  gives further support to our conclusion

Star Formation in Emission‐Line Galaxies between Redshifts of 0.8 and 1.6