The Grism Lens-Amplified Survey from Space (GLASS). XIII. G800L optical spectra from the parallel fields

We present a catalogue of 22755 objects with slitless, optical, Hubble Space Telescope (HST) spectroscopy from the Grism Lens-Amplified Survey from Space (GLASS). The data cover $\sim$220 sq. arcmin to 7-orbit ($\sim$10 ks) depth in 20 parallel pointings of the Advanced Camera for Survey's G800L grism. The fields are located 6' away from 10 massive galaxy clusters in the HFF and CLASH footprints. Thirteen of the fields have ancillary HST imaging from these or other programs to facilitate a large number of applications, from studying metal distributions at $z\sim0.5$, to quasars at $z\sim4$, to the star formation histories of hundreds of galaxies in between. The spectroscopic catalogue has a median redshift of $\langle z\rangle=0.6$ with a median uncertainty of $\Delta z / (1+z)\lesssim2\%$ at $\rm F814W\lesssim23$ AB. Robust continuum detections reach a magnitude fainter. The 5 $\sigma$ limiting line flux is $f_{\rm lim}\approx5\times10^{-17}\rm~erg~s^{-1}~cm^{-2}$ and half of all sources have 50% of pixels contaminated at $\lesssim$1%. All sources have 1- and 2-D spectra, line fluxes/uncertainties and identifications, redshift probability distributions, spectral models, and derived narrow-band emission line maps from the Grism Redshift and Line Analysis tool (GRIZLI). We provide other basic sample characterisations, show data examples, and describe sources and potential investigations of interest. All data and products will be available online along with software to facilitate their use.