Measuring cosmic density of neutral hydrogen via stacking the DINGO-VLA data

We use the 21-cm emission-line data from the Deep Investigation of Neutral Gas Origin-Very Large Array (DINGO-VLA) project to study the atomic hydrogen gas H I of the Universe at redshifts z < 0.1. Results are obtained using a stacking analysis, combining the H I signals from 3622 galaxies extracted from 267 VLA pointings in the G09 field of the Galaxy and Mass Assembly Survey (GAMA). Rather than using a traditional one-dimensional spectral stacking method, a three-dimensional cubelet stacking method is used to enable deconvolution and the accurate recovery of average galaxy fluxes from this high-resolution interferometric data set. By probing down to galactic scales, this experiment also overcomes confusion corrections that have been necessary to include in previous single-dish studies. After stacking and deconvolution, we obtain a 30σ H I mass measurement from the stacked spectrum, indicating an average H I mass of M_{H I} = (1.67 ± 0.18) × 10⁹ M_⊙. The corresponding cosmic density of neutral atomic hydrogen is Ω_{H I} = (0.38 ± 0.04) × 10⁻³ at redshift of z = 0.051. These values are in good agreement with earlier results, implying there is no significant evolution of Ω_{H I} at lower redshifts.