# Prospects for cosmic magnification measurements using HI intensity mapping

## TL;DR

This paper assesses the potential of using HI intensity mapping from SKA1-MID and HIRAX to measure cosmic magnification by cross-correlating with optical galaxy surveys, forecasting detection capabilities and parameter constraints.

## Contribution

It provides the first detailed forecast of cosmic magnification measurements using HI intensity mapping with SKA1-MID and HIRAX, highlighting their complementarity and potential for constraining HI parameters.

## Key findings

- SKA1-MID can achieve SNR ~15 for multipoles up to 200
- HIRAX can reach SNR ~50 for multipoles between 200 and 2000
- Measurements are feasible up to redshift ~2, especially between 0.6 and 1.3

## 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.