The Neutral Hydrogen Cosmological Mass Density at z = 5

Neil H. M. Crighton, Michael T. Murphy, J. Xavier Prochaska, Gábor Worseck, Marc Rafelski, George D. Becker, Sara L. Ellison, Michele Fumagalli, Sebastian Lopez, Avery Meiksin, John M. O'Meara

Research output: Contribution to conferencePaperpeer-review


We present the largest homogeneous survey of redshift > 4.4 damped Lyα systems (DLAs) using the spectra of 163 quasars that comprise the Giant Gemini GMOS (GGG) survey. With this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, ΩHI. After correcting for systematic effects using a combination of mock and higher-resolution spectra, we find ΩHI= 0.98+0.20 -0.18 × 10-3 at = 4.9, assuming a 20% contribution from lower column density systems below the DLA threshold. By comparing to literature measurements at lower redshifts, we show that ΩHI can be described by the functional form ΩHI(z) ~ (1 + z)0.4. This gradual decrease from z = 5 to 0 suggests that in the galaxies which dominate the cosmic star formation rate, Hi is a transitory gas phase fuelling star formation which must be continually replenished by more highly-ionized gas from the intergalactic medium, and from recycled galactic winds.
Original languageEnglish
Publication statusPublished - 1 Mar 2017


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