An accurate low-redshift measurement of the cosmic neutral hydrogen density

Wenkai Hu, Laura Hoppmann, Lister Staveley-Smith, Katinka Geréb, Tom Oosterloo, Raffaella Morganti, Barbara Catinella, Luca Cortese, Claudia P. Del Lagos, Martin Meyer

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Using a spectral stacking technique, we measure the neutral hydrogen (H I) properties of a sample of galaxies at z < 0.11 across 35 pointings of the Westerbork Synthesis Radio Telescope. The radio data contain 1895 galaxies with redshifts and positions known from the Sloan Digital Sky Survey. We carefully quantified the effects of sample bias, aperture used to extract spectra, sidelobes and weighting technique and use our data to provide a new estimate for the cosmic HI mass density. We find a cosmic HI mass density of ΩHI = (4.02 ± 0.26) × 10-4h -1 70 at (z) = 0.066, consistent with measurements from blind HI surveys and otherHI stacking experiments at lowredshifts. The combination of the small interferometer beam size and the large survey volume makes our result highly robust against systematic effects due to confusion at small scales and cosmic variance at large scales. Splitting into three subsamples with (z) = 0.038, 0.067, and 0.093 shows no significant evolution of the HI gas content at low redshift.

Original languageEnglish
Pages (from-to)1619-1632
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - 1 Jan 2019


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