A WFC3 Grism Emission Line Redshift Catalog in the GOODS-South Field

Abstract

We combine Hubble Space Telescope (HST)/Wide Field Camera3 (WFC3) imaging and G141 grism observations from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and 3D-HST surveys to produce a catalog of grism spectroscopic redshifts for galaxies in the CANDELS/GOODS-South field. The WFC3/G141 grism spectra cover a wavelength range of 1.1≤slant λ ≤slant 1.7 μm with a resolving power of R̃ 130 for point sources, thus providing rest-frame optical spectra for galaxies out to z̃ 3.5. The catalog is selected in the H-band (F160W) and includes both galaxies with and without previously published spectroscopic redshifts. Grism spectra are extracted for all H-band detected galaxies with H ≤slant 24 and a CANDELS photometric redshift {{z}<SUB>phot</SUB>}≥slant 0.6. The resulting spectra are visually inspected to identify emission lines, and redshifts are determined using cross-correlation with empirical spectral templates. To establish the accuracy of our redshifts, we compare our results against high-quality spectroscopic redshifts from the literature. Using a sample of 411 control galaxies, this analysis yields a precision of {{σ }<SUB>NMAD</SUB>}=0.0028 for the grism-derived redshifts, which is consistent with the accuracy reported by the 3D-HST team. Our final catalog covers an area of 153 arcmin<SUP>2</SUP> and contains 1019 redshifts for galaxies in GOODS-S. Roughly 60% (608/1019) of these redshifts are for galaxies with no previously published spectroscopic redshift. These new redshifts span a range of 0.677≤slant z≤slant 3.456 and have a median redshift of z = 1.282. The catalog contains a total of 234 new redshifts for galaxies at z\gt 1.5. In addition, we present 20 galaxy pair candidates identified for the first time using the grism redshifts in our catalog, including four new galaxy pairs at z̃ 2, nearly doubling the number of such pairs previously identified.