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arXiv · 2607.00827

Cosmology from HI galaxy surveys with the SKA

Ainulnabilah Nasirudin·Philip Bull·Ziad Sakr·Joël Mayor·Benedict Bahr-Kalus·Hengxing Pan·Stefano Camera·José Fonseca·Liantsoa F. Randrianjanahary·Gabriella De Lucia·Marta Spinelli
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Abstract

The 21cm line from neutral hydrogen is expected to be a ubiquitous (albeit faint) tracer of galaxies in the late Universe. With SKAO-MID, large wide-field surveys of several million HI-containing galaxies will become feasible, resulting in catalogues of sufficient size to measure large-scale structure observables such as baryon acoustic oscillations and redshift-space distortions. While optical galaxy surveys over comparable areas are generally deeper, radio surveys of this kind have a number of other advantages, such as broader sampling of the halo mass function and the possibility of measuring luminosity distances via the Tully-Fisher relation. In this chapter, we provide predictions for the galaxy number counts versus redshift that will be achievable with a wide-field HI galaxy survey on SKAO-MID, along with corresponding forecasts for cosmological observables. Given the substantial uncertainty in the HI mass function with redshift, we bracket our predictions using a handful of different modelling methods.

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Ainulnabilah Nasirudin, Philip Bull, Ziad Sakr, Joël Mayor, Benedict Bahr-Kalus, Hengxing Pan, Stefano Camera, José Fonseca, Liantsoa F. Randrianjanahary, Gabriella De Lucia, Marta Spinelli. 2026-07-01. Cosmology from HI galaxy surveys with the SKA. https://arxiv.org/abs/2607.00827

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