Giant Metrewave Radio Telescope observations of neutral atomic hydrogen gas in the COSMOS field at z ~ 0.37

Jonghwan Rhee, P. Lah, J.N. Chengalur, F.H. Briggs, M. Colless

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Abstract

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
We present the results of H I spectral stacking analysis of Giant Metrewave Radio Telescope (GMRT) observations targeting the Cosmological Evolution Survey (COSMOS) field. The GMRT data cube contains 474 field galaxies with redshifts known from the zCOSMOS-bright 10 k catalogue. Spectra for the galaxies are co-added and the stacked spectrum allows us to make a ~3s measurement of the average H I mass. Using this average H I mass, along with the integral optical B-band luminosity of the galaxies and the luminosity density of the COSMOS field, a volume normalization is applied to obtain the cosmic H I mass density (OH I). We find a cosmic H I mass density of OH I = (0.42 ± 0.16) × 10-3 at z ~ 0.37, which is the highest redshift measurement of OH I ever made using H I spectral stacking. The value we obtained for OH I at z ~ 0.37 is consistent with that measured from large blind 21-cm surveys at z = 0, as well as measurements from other H I stacking experiments at lower redshifts. Our measurement, in conjunction with earlier measurements, indicates that there has been no significant evolution of H I gas abundance over the last 4 Gyr. A weighted mean of OH I from all 21-cm measurements at redshifts z ? 0.4 gives OH I = (0.35 ± 0.01) × 10-3. The OH I measured (from H I 21-cm emission measurements) at z ? 0.4 is, however, approximately half that measured from damped Lyman-a absorption (DLA) systems at z ? 2. Deeper surveys with existing and upcoming instruments will be critical to understand the evolution of OH I in the redshift range intermediate between z ~ 0.4 and the range probed by DLA observations.
Original languageEnglish
Pages (from-to)2675-2686
JournalMonthly Notices of the Royal Astronomical Society
Volume460
Issue number3
Early online date10 May 2016
DOIs
Publication statusPublished - Aug 2016

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