Prospects for cosmic magnification measurements using HI intensity mapping

Abstract

We investigate the prospects of measuring the cosmic magnification effect by cross-correlating neutral hydrogen intensity mapping (HI IM) maps with background optical galaxies. We forecast the signal-to-noise ratio for HI IM data from SKA1-MID and HIRAX, combined with LSST photometric galaxy samples. We find that, thanks to their different resolutions, SKA1-MID and HIRAX are highly complementary in such an analysis. We predict that SKA1-MID can achieve a detection with a signal-to-noise ratio of $\sim 15$ on a multipole range of $\ell \lesssim 200$, while HIRAX can reach a signal-to-noise ratio of $\sim 50$ on $200<\ell <2000$. We conclude that measurements of the cosmic magnification signal will be possible on a wide redshift range with foreground HI intensity maps up to $z\lesssim 2$, while optimal results are obtained when $0.6\lesssim z\lesssim 1.3$. Finally, we perform a signal to noise analysis that shows how these measurements can constrain the HI parameters across a wide redshift range.

Accepted version. 9 pages, 7 figures, 2 tables