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 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
Wide Field Camera Three (WFC3) on the Hubble Space Telescope (HST). From our
search of 419 WISP fields covering an area of ~0.5 deg$^{2}$, we find 413 ELG
pair systems, mostly Halpha emitters. We then derive reliable star formation
rates (SFRs) based on the attenuation-corrected Halpha 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 (Delta_v <
300 km/s). 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 $f \propto (1+z)^\alpha$,
where the power-law index \alpha=0.58$\pm$0.17 from $z\sim$0.2 to $z\sim$1.6.
The fraction of Active galactic Nuclei (AGNs), is found to be the same in the
ELG pairs as compared to isolated ELGs.
