Spectroscopically Identified Emission Line Galaxy Pairs in the WISP Survey

Abstract

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 similar to 0.5 deg(2), we find 413 ELG pair systems, mostly H (alpha) emitters. We then derive reliable star formation rates (SFRs) based on the attenuation-corrected H (alpha) 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(-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 proportional to (1 + z) (alpha) , where the power-law index alpha = 0.58 +/- 0.17 from z similar to 0.2 to similar 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. Show more