Abstract
We report the first direct detection of the cosmological power spectrum using
the intensity signal from 21-cm emission of neutral hydrogen (HI), derived from
interferometric observations with the L-band receivers of the new 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 HI power spectrum at redshifts $0.32$ and $0.44$ with high
statistical significance using a foreground avoidance method (at $8.0\sigma$
and $11.5\sigma$ respectively). We constrain the rms of the fluctuations of the
HI distribution to be $\sigma_HI = (0.440.04)\,mK$ and
$\sigma_HI = (0.630.03)\,mK$ respectively at scales of 1.0 Mpc.
The information contained in the power spectrum measurements allows us to probe
the parameters of the HI mass function and HI halo model. These results are a
significant step towards precision cosmology with HI intensity mapping using
the new generation of radio telescopes.
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