We present results from near-infrared spectroscopy of 26 emission-line galaxies at z ∼ 2.2 and z ∼ 1.5 obtained with the Folded-port InfraRed Echellette (FIRE) spectrometer on the 6.5-meter Magellan Baade telescope. The sample was selected from the WFC3 Infrared Spectroscopic Parallels (WISP) survey, which uses the near-infrared grism of the Hubble Space Telescope Wide Field Camera 3 to detect emission-line galaxies over 0.3 z 2.3. Our FIRE follow-up spectroscopy (R∼5000) over 1.0-2.5 µm permits detailed measurements of physical properties of the z ∼ 2 emission-line galaxies. Dust-corrected star formation rates for the sample range from ∼5-100 M ⊙ yr −1 with a mean of 29 M ⊙ yr −1 . We derive a median metallicity for the sample of 12 + log(O/H) = 8.34 or ∼0.45 Z ⊙ . The estimated stellar masses range from ∼10 8.5 − 10 9.5 M ⊙ , and a clear positive correlation between metallicity and stellar mass is observed. The average ionization parameter measured for the sample, log U ≈ −2.5, is significantly higher than what is found for most star-forming galaxies in the local universe, but similar to the values found for other star-forming galaxies at high redshift. We derive composite spectra from the FIRE sample, from which we infer typical nebular electron densities of ∼100-400 cm −3 . Based on the location of the galaxies and composite spectra on BPT diagrams, we do not find evidence for significant AGN activity in the sample. Most of the galaxies as well as the composites are offset in the BPT diagram toward higher [O iii]/Hβ at a given [N ii]/Hα, in agreement with other observations of z 1 star-forming galaxies, but composite spectra derived from the sample do not show an appreciable offset from the local star-forming sequence on the [O iii]/Hβ versus [S ii]/Hα diagram. We infer a high nitrogen-to-oxygen abundance ratio from the composite spectrum, which may contribute to the offset of the high-redshift galaxies from the local star-forming sequence in the [O iii]/Hβ versus [N ii]/Hα diagram. We speculate that the elevated nitrogen abundance could result from substantial numbers of Wolf-Rayet stars in starbursting galaxies at z ∼ 2.

We present near-infrared emission line counts and luminosity functions from the HST WFC3 Infrared Spectroscopic Parallels (WISP) program for 29 fields (0.037 deg 2 ) observed using both the G102 and G141 grism. Altogether we identify 1048 emission line galaxies with observed equivalent widths greater than 40Å, 467 of which have multiple detected emission lines. We use simulations to correct for significant (>20%) incompleteness introduced in part by the non-dithered, non-rotated nature of the grism parallels. The WISP survey is sensitive to fainter flux levels (3-5×10 −17 ergs s −1 cm −2 ) than the future space near-infrared grism missions aimed at baryonic acoustic oscillation cosmology (1-4 ×10 −16 ergs s −1 cm −2 ), allowing us to probe the fainter emission line galaxies that the shallower future surveys may miss. Cumulative number counts of 0.7

Spectroscopic observations of Hα and Hβ emission lines of 128 star-forming galaxies in the redshift range 0.75 ≤ z ≤ 1.5 are presented. These data were taken with slitless spectroscopy using the G102 and G141 grisms of the Wide-Field-Camera 3 (WFC3) on board the Hubble Space Telescope as part of the WFC3 Infrared Spectroscopic Parallel (WISP) survey. Interstellar dust extinction is measured from stacked spectra that cover the Balmer decrement (Hα/Hβ). We present dust extinction as a function of Hα luminosity (down to 3 × 10 41 erg s −1 ), galaxy stellar mass (reaching 4 × 10 8 M ), and rest-frame Hα equivalent width. The faintest galaxies are two times fainter in Hα luminosity than galaxies previously studied at z ∼ 1.5. An evolution is observed where galaxies of the same Hα luminosity have lower extinction at higher redshifts, whereas no evolution is found within our error bars with stellar mass. The lower Hα luminosity galaxies in our sample are found to be consistent with no dust extinction. We find an anti-correlation of the [O III]λ5007/Hα flux ratio as a function of luminosity where galaxies with L Hα < 5 × 10 41 erg s −1 are brighter in [O III]λ5007 than Hα. This trend is evident even after extinction correction, suggesting that the increased [O III]λ5007/Hα ratio in low luminosity galaxies is likely due to lower metallicity and/or higher ionization parameters.

We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10 8 M/M ⊙ 10 10 , obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 z 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R 23 metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10 9.8 M ⊙ , to 12+log(O/H)= 8.2 at M = 10 8.2 M ⊙ . After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M 10 9.5 M ⊙ and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M * relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high SFRs. Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation. * Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.