NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-20 T22:18:05 PDT
Help | Comment | NED Home

For refcode 2016ApJ...818..113N:
Retrieve 869 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
2016ApJ...818..113N The H I Content of the Universe Over the Past 10 GYRS Neeleman, Marcel; Prochaska, J. Xavier; Ribaudo, Joseph; Lehner, Nicolas; Howk, J. Christopher; Rafelski, Marc; Kanekar, Nissim Abstract. We use the Hubble Space Telescope (HST) archive of ultraviolet (UV) quasar spectroscopy to conduct the first blind survey for damped Ly-{alpha} absorbers (DLAs) at low redshift (z\lt 1.6). Our statistical sample includes 463 quasars with spectral coverage spanning a total redshift path {{Delta}}z=123.3 or an absorption path {{Delta}}X=229.7. Within this survey path, we identify 4 DLAs defined as absorbers with H I column density {N}_{{H_}{{I}}} >=slant {10}^20.3^ cm^-2^, which implies an incidence per absorption length {{l}}_{{DLA_}}(X) = {0.017}_-0.008_^+0.014^ at a median survey path redshift of z = 0.623. While our estimate of {{l}}_{{DLA_}}(X) is lower than earlier estimates at z~ 0 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 {N}_{{H_}{{I}}} frequency distribution function f({N}_{{H_}{{I}}},X), but the observed distribution agrees with previous estimates at z\gt 2. Adopting the z\gt 2 shape of f({N}_{{H_}{{I}}},X), we infer an H I mass density at z~ 0.6 of {rho}_{{H_} {{I}}}^{{DLA^}} = {0.25}_-0.12_^+0.20^x {10}^8^{M}_o_ {{{Mpc}}}^-3^. 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. Key words: evolution, galaxies: evolution, galaxies: ISM, intergalactic medium, quasars: absorption lines
Retrieve 869 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home