A WFC3 Grism Emission Line Redshift Catalog in the GOODS-South Field
  We combine HST/WFC3 imaging and G141 grism observations from the 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<lambda<1.7 microns with a resolving power of R~130 for
point sources, thus providing rest-frame optical spectra for galaxies out to
z~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<24 and a CANDELS
photometric redshift z_phot > 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 sigma_NMAD=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 square arcmin 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 < z < 3.456 and have a median redshift of z=1.282. The catalog
contains a total of 234 new redshifts for galaxies at z>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 z~2, nearly
doubling the number of such pairs previously identified.
