Neutral Hydrogen Observations: Techniques and Cosmological Insights
A special issue of Universe (ISSN 2218-1997). This special issue belongs to the section "Cosmology".
Deadline for manuscript submissions: 31 August 2026 | Viewed by 44
Special Issue Editors
Interests: neutral hydrogen intensity mapping; large-scale structure; galaxy dynamics; galaxy and galaxy clusters
Special Issue Information
Dear Colleagues,
Hydrogen is the most abundant baryonic element in the universe. The neutral hydrogen 21-cm spectral line serves as a crucial probe for revealing the formation and evolution of cosmic structures, primarily in two contexts:
At the galactic scale, precise measurements of the 21-cm emission line from nearby to mid/high-redshift galaxies enable direct tracking of the distribution and dynamics of cosmic matter. This "21-cm galaxy" approach can resolve the spatial distribution of gas, rotation curves, and environmental effects in individual galaxies. These observations provide key constraints on the gravitational potential field of dark matter halos and, furthermore, limit the properties of dark matter (both hot and cold) through the neutral hydrogen mass function.
At the cosmological scale, the neutral hydrogen intensity mapping technique statistically correlates the accumulated 21-cm signals from numerous unresolved galaxies, facilitating efficient surveys of large-scale structures. Although it sacrifices the spatial resolution of individual galaxies, this innovative method traces the evolution of dark energy from the epoch of reionization to the nearby universe via the three-dimensional power spectrum of neutral hydrogen distribution. It thereby opens a new observational window for understanding the physical origin of the late-time cosmic acceleration—whether it arises from a dark energy component or a modification of gravitational theory on large scales.
Currently, sky surveys conducted with next-generation radio telescopes, such as the Square Kilometre Array (SKA), are organically integrating these two research paradigms to advance the systematic exploration of frontier topics, including dark matter, dark energy, and cosmic reionization.
Prof. Dr. Yougang Wang
Dr. Yichao Li
Guest Editors
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Keywords
- neutral hydrogen intensity mapping
- neutral hydrogen galaxy
- neutral hydrogen absorber
- large-scale structure
- galaxy dynamics
- galaxy and galaxy clusters
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