Deep investigation of neutral gas origins (DINGO): H_I stacking experiments with early science data

We present early science results from Deep Investigation of Neutral Gas Origins (DINGO), an H_I survey using the Australian Square Kilometre Array Pathfinder (ASKAP). Using ASKAP subarrays available during its commissioning phase, DINGO early science data were taken over ∼60 deg² of the Galaxy And Mass Assembly (GAMA) 23 h region with 35.5 h integration time. We make direct detections of six known and one new sources at z < 0.01. Using H_I spectral stacking, we investigate the H_I gas content of galaxies at 0.04 < z < 0.09 for different galaxy colours. The results show that galaxy morphology based on optical colour is strongly linked to H_I gas properties. To examine environmental impacts on the H_I gas content of galaxies, three subsamples are made based on the GAMA group catalogue. The average H_I mass of group central galaxies is larger than those of satellite and isolated galaxies, but with a lower H_I gas fraction. We derive a variety of H_I scaling relations for physical properties of our sample, including stellar mass, stellar mass surface density, NUV − r colour, specific star formation rate, and halo mass. We find that the derived Hi scaling relations are comparable to other published results, with consistent trends also observed to ∼0.5 dex lower limits in stellar mass and stellar surface density. The cosmic H_I densities derived from our data are consistent with other published values at similar redshifts. DINGO early science highlights the power of H_I spectral stacking techniques with ASKAP.