Measuring Cosmic Density of Neutral Hydrogen via Stacking the DINGO-VLA Data

Abstract: We use the 21 cm emission line data from the DINGO-VLA project to study the atomic hydrogen gas H\,{\textsc i} of the Universe at redshifts $z&lt;0.1$. Results are obtained using a stacking analysis, combining the H\,{\textsc 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 dataset. 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 $30\sigma$ H\,{\textsc i} mass measurement from the stacked spectrum, indicating an average H\,{\textsc i} mass of $M_{\rm H\,{\textsc i}}=(1.674\pm 0.183)\times 10<sup>{9}~{\Msun}$. The corresponding cosmic density of neutral atomic hydrogen is $\Omega_{\rm H\,{\textsc i}}=(0.377\pm 0.042)\times 10<sup>{-3}$ at redshift of $z=0.051$. These values are in good agreement with earlier results, implying there is no significant evolution of $\Omega_{\rm H\,{\textsc i}}$ at lower redshifts.