The Qz5 Survey (I): How the HI Mass Density of the Universe Evolves With Cosmic Time

Grecco A. Oyarzún, Marc Rafelski, Lise Christensen +9

We report that the neutral hydrogen (HI) mass density of the Universe (${\rho }_{HI}$) increases with cosmic time since $z\sim 5$, peaks at $z\sim 3$, and then decreases toward $z \sim…