Spectroscopically Identified Emission Line Galaxy Pairs in the WISP Survey

We identify a sample of spectroscopically measured emission line galaxy (ELG) Pairs up to z = 1.6 from the Wide Field Camera 3 (WFC3) Infrared Spectroscopic Parallels (WISP) survey. WISP obtained slitless, near-infrared grism spectroscopy along with direct imaging in the J and H bands by observing in the pure-parallel mode with the WFC3 on board the Hubble Space Telescope. From our search of 419 WISP fields covering an area of ~0.5 deg², we find 413 ELG pair systems, mostly H _α emitters. We then derive reliable star formation rates (SFRs) based on the attenuation-corrected H _α fluxes. Compared to isolated galaxies, we find an average SFR enhancement of 40%-65%, which is stronger for major Pairs and Pairs with smaller velocity separations (Δ _v < 300 km s^-1). Based on the stacked spectra from various subsamples, we study the trends of emission line ratios in pairs, and find a general consistency with enhanced lower ionization lines. We study the pair fraction among ELGs, and find a marginally significant increase with redshift f ∝ (1 + z) ^α , where the power-law index α = 0.58 ± 0.17 from z ~ 0.2 to ~1.6. The fraction of active galactic nuclei is found to be the same in the ELG Pairs as compared to the isolated ELGs. ^* 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. These observations are associated with programs 11696, 12283, 12568, 12092, 13352, 13517, and 14178.