Spectroscopically Identified Emission Line Galaxy Pairs in the WISP Survey

December 2021 • 2021ApJ...923..156D

Authors • Dai, Y. Sophia • Malkan, Matthew M. • Teplitz, Harry I. • Scarlata, Claudia • Alavi, Anahita • Atek, Hakim • Bagley, Micaela • Baronchelli, Ivano • Battisti, Andrew • Bunker, Andrew J. • Hathi, Nimish P. • Henry, Alaina • Huang, Jiasheng • Jin, Gaoxiang • Li, Zijian • Martin, Crystal • Mehta, Vihang • Phillips, John • Rafelski, Marc • Rutkowski, Michael • Xu, Hai • Xu, Cong K. • Zanella, Anita

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 ~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.


IPAC Authors


Anahita Alavi

Assistant Scientist


Harry Teplitz

Senior Scientist