HI intensity mapping with MeerKAT: power spectrum detection in cross-correlation with WiggleZ galaxies

TL;DR

This paper reports the first detection of cross-correlation between MeerKAT radio intensity maps and WiggleZ galaxy data, demonstrating the viability of intensity mapping for cosmology and constraining the HI density and bias.

Contribution

It presents the first practical detection of HI intensity mapping through cross-correlation with galaxy surveys using MeerKAT, advancing the methodology for future SKAO cosmology studies.

Findings

7.7 sigma detection of cross-correlation power spectrum

Constraint on the product of HI density fraction, bias, and correlation coefficient

Demonstration of multi-dish auto-correlation intensity mapping for cosmology

Abstract

We present a detection of correlated clustering between MeerKAT radio intensity maps and galaxies from the WiggleZ Dark Energy Survey. We find a $7.7\sigma$ detection of the cross-correlation power spectrum, the amplitude of which is proportional to the product of the HI density fraction ($\Omega_{\rm HI}$), HI bias ($b_{\rm HI}$) and the cross-correlation coefficient ($r$). We therefore obtain the constraint $\Omega_{\rm HI} b_{\rm HI} r\,{=}\,[0.86\,{\pm}\,0.10\,({\rm stat})\,{\pm}\,0.12\,({\rm sys})]\,{\times}\,10^{-3}$, at an effective scale of $k_{\rm eff}\,{\sim}\,0.13\,h\,{\rm Mpc}^{-1}$. The intensity maps were obtained from a pilot survey with the MeerKAT telescope, a 64-dish pathfinder array to the SKA Observatory (SKAO). The data were collected from 10.5 hours of observations using MeerKAT's L-band receivers over six nights covering the 11hr field of WiggleZ, in the frequency range $1015-973\,{\rm MHz}$ (0.400$\,{<}\,z\,{<}\,$0.459 in redshift). This detection is the first practical demonstration of the multi-dish auto-correlation intensity mapping technique for cosmology. This marks an important milestone in the roadmap for the cosmology science case with the full SKAO.