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| Main Authors: | , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2502.05261 |
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| _version_ | 1866908276507017216 |
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| author | Oyarzún, Grecco A. Rafelski, Marc Christensen, Lise Ozyurt, Fiona Jorgenson, Regina A. Neeleman, Marcel Fumagalli, Michele Prochaska, J. Xavier Worseck, G. Wisz, M. E. Becker, George D. López, Sebastián |
| author_facet | Oyarzún, Grecco A. Rafelski, Marc Christensen, Lise Ozyurt, Fiona Jorgenson, Regina A. Neeleman, Marcel Fumagalli, Michele Prochaska, J. Xavier Worseck, G. Wisz, M. E. Becker, George D. López, Sebastián |
| contents | We report that the neutral hydrogen (HI) mass density of the Universe ($ρ_{HI}$) increases with cosmic time since $z \sim 5$, peaks at $z \sim 3$, and then decreases toward $z \sim 0$. This is the first result of Qz5, our spectroscopic survey of 63 quasars at $z \gtrsim 5$ with VLT/X-SHOOTER and Keck/ESI aimed at characterizing intervening HI gas absorbers at $z \sim 5$. The main feature of Qz5 is the high resolution ($R \sim 7000 - 9000$) of the spectra, which allows us to (1) accurately detect high column density HI gas absorbers in an increasingly neutral intergalactic medium at $z \sim 5$ and (2) determine the reliability of previous $ρ_{HI}$ measurements derived with lower resolution spectroscopy. We find 5 intervening Damped Ly$α$ absorbers (DLAs) at $z > 4.5$, which corresponds to the lowest DLA incidence rate ($0.034^{0.05}_{0.02}$) at $z \gtrsim 2$. We also measure the lowest $ρ_{HI}$ at $z \gtrsim 2$ from our sample of DLAs and subDLAs, corresponding to $ρ_{HI} = 0.56^{0.82}_{0.31} \times 10^8~$M$_{\odot}~$Mpc$^{-3}$ at $z \sim 5$. Taking into account our measurements at $z \sim 5$ and systematic biases in the DLA detection rate at lower spectral resolutions, we conclude that $ρ_{HI}$ doubles from $z \sim 5$ to $z \sim 3$. From these results emerges a qualitative agreement between how the cosmic densities of HI gas mass, molecular gas mass, and star-formation rate build up with cosmic time. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2502_05261 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The Qz5 Survey (I): How the HI Mass Density of the Universe Evolves With Cosmic Time Oyarzún, Grecco A. Rafelski, Marc Christensen, Lise Ozyurt, Fiona Jorgenson, Regina A. Neeleman, Marcel Fumagalli, Michele Prochaska, J. Xavier Worseck, G. Wisz, M. E. Becker, George D. López, Sebastián Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics We report that the neutral hydrogen (HI) mass density of the Universe ($ρ_{HI}$) increases with cosmic time since $z \sim 5$, peaks at $z \sim 3$, and then decreases toward $z \sim 0$. This is the first result of Qz5, our spectroscopic survey of 63 quasars at $z \gtrsim 5$ with VLT/X-SHOOTER and Keck/ESI aimed at characterizing intervening HI gas absorbers at $z \sim 5$. The main feature of Qz5 is the high resolution ($R \sim 7000 - 9000$) of the spectra, which allows us to (1) accurately detect high column density HI gas absorbers in an increasingly neutral intergalactic medium at $z \sim 5$ and (2) determine the reliability of previous $ρ_{HI}$ measurements derived with lower resolution spectroscopy. We find 5 intervening Damped Ly$α$ absorbers (DLAs) at $z > 4.5$, which corresponds to the lowest DLA incidence rate ($0.034^{0.05}_{0.02}$) at $z \gtrsim 2$. We also measure the lowest $ρ_{HI}$ at $z \gtrsim 2$ from our sample of DLAs and subDLAs, corresponding to $ρ_{HI} = 0.56^{0.82}_{0.31} \times 10^8~$M$_{\odot}~$Mpc$^{-3}$ at $z \sim 5$. Taking into account our measurements at $z \sim 5$ and systematic biases in the DLA detection rate at lower spectral resolutions, we conclude that $ρ_{HI}$ doubles from $z \sim 5$ to $z \sim 3$. From these results emerges a qualitative agreement between how the cosmic densities of HI gas mass, molecular gas mass, and star-formation rate build up with cosmic time. |
| title | The Qz5 Survey (I): How the HI Mass Density of the Universe Evolves With Cosmic Time |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2502.05261 |