A direct detection of neutral hydrogen intensity mapping on mpc scales at z ≈ 0.32 and z ≈ 0.44

Abstract

We report the detection of the cosmological power spectrum using the intensity mapping signal from 21 cm emission of neutral hydrogen (H I), derived from interferometric observations with the L-band receivers of the MeerKAT radio telescope. Intensity mapping is a promising technique to map the three-dimensional matter distribution of the Universe at radio frequencies and probe the underlying cosmology. So far, detections have only been achieved through cross-correlations with galaxy surveys. Here we present independent measurements of the H I power spectrum at redshifts 0.32 and 0.44 with the foreground avoidance method. We utilize two distinct frameworks for mitigating systematics: a conservative baseline-flagging-based approach achieves detections at 3.2σ and 3.5σ, and a power-spectrum-based flagging method enhances the significance to 5.9σ and 9.18σ, respectively. The information contained in the power spectrum measurements allows us to probe the parameters of the H I mass function and H I halo model. These results are a significant step toward precision cosmology with H I intensity mapping using the new generation of radio telescopes. © 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the https://creativecommons.org/licenses/by/4.0/. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.