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  • THE H i CONTENT OF THE UNIV...
    Neeleman, Marcel; Prochaska, J. Xavier; Ribaudo, Joseph; Lehner, Nicolas; Howk, J. Christopher; Rafelski, Marc; Kanekar, Nissim

    The Astrophysical journal, 02/2016, Volume: 818, Issue: 2
    Journal Article

    ABSTRACT We use the Hubble Space Telescope (HST) archive of ultraviolet (UV) quasar spectroscopy to conduct the first blind survey for damped Ly absorbers (DLAs) at low redshift ( ). Our statistical sample includes 463 quasars with spectral coverage spanning a total redshift path or an absorption path . Within this survey path, we identify 4 DLAs defined as absorbers with H i column density cm−2, which implies an incidence per absorption length at a median survey path redshift of z = 0.623. While our estimate of is lower than earlier estimates at from H i 21 cm emission studies, the results are consistent within the measurement uncertainties. Our data set is too small to properly sample the frequency distribution function , but the observed distribution agrees with previous estimates at . Adopting the shape of , we infer an H i mass density at of . This is significantly lower than previous estimates from targeted DLA surveys with the HST, but consistent with results from low-z H i 21 cm observations, and suggests that the neutral gas density of the universe has been decreasing over the past 10 Gyr.