A Catalog of Emission-Line Galaxies from the Faint Infrared Grism
  Survey: Studying Environmental Influence on Star Formation
  We present a catalog of 208 $0.3 < z < 2.1$ Emission Line Galaxies (ELG)
selected from 1D slitless spectroscopy obtained using Hubble's WFC3 G102 grism,
as part of the Faint Infrared Grism Survey (FIGS). We identify ELG candidates
by searching for significant peaks in all continuum-subtracted G102 spectra,
and, where possible, confirm candidates by identifying consistent emission
lines in other available spectra or with published spectroscopic redshifts. We
provide derived emission line fluxes and errors, redshifts, and equivalent
widths (EW) for H$\alpha$ $\lambda6563$, [OIII]$\lambda\lambda4959,5007$, and
[OII]$\lambda\lambda3727$ emission lines, for emission line galaxies down to
AB(F105W) $ > 28$ and $> 10^{-17}$ erg cm$^{-2}$ s$^{-1}$ line flux. We use the
resulting line catalog to investigate a possible relationship between line
emission and a galaxy's environment. We use 7th-nearest-neighbor distances to
investigate the typical surroundings of ELGs compared to non-ELGs, and we find
that [OIII] emitters are preferentially found at intermediate galaxy densities
near galaxy groups. We characterize these ELGs in terms of the galaxy specific
star formation rate (SSFR) versus stellar mass, and find no significant
influence of environment on that relation. We calculate star formation rates
(SFR), and find no dependence of SFR on local galaxy surface density for $0.3 <
z < 0.8$ H$\alpha$ emitters and for $0.8<z<1.3$ [OIII] emitters. We find
similar rates of close-pair interaction between ELGs and non-ELGs. For galaxy
surface densities $\Sigma \leq 30$ Mpc$^{-2}$, we find no consistent effect of
environment on star formation.
