Imaging the Cosmic Matter Distribution using Gravitational Lensing of Pregalactic HI

TL;DR

This paper demonstrates that 21-cm emission lensing can produce high-fidelity maps of cosmic matter distribution, surpassing galaxy lensing in signal-to-noise, and enabling detailed dark matter studies with future radio telescopes like SKA.

Contribution

It compares 21-cm lensing imaging capabilities with galaxy lensing, showing potential for superior high-resolution mass mapping of the universe.

Findings

21-cm lensing can outperform galaxy lensing in signal-to-noise ratio.

High-fidelity mass maps could directly image dark matter halos.

Future radio telescopes like SKA can achieve near-resolution limit imaging.

Abstract

21-cm emission from neutral hydrogen during and before the epoch of cosmic reionisation is gravitationally lensed by material at all lower redshifts. Low-frequency radio observations of this emission can be used to reconstruct the projected mass distribution of foreground material, both light and dark. We compare the potential imaging capabilities of such 21-cm lensing with those of future galaxy lensing surveys. We use the Millennium Simulation to simulate large-area maps of the lensing convergence with the noise, resolution and redshift-weighting achievable with a variety of idealised observation programmes. We find that the signal-to-noise of 21-cm lens maps can far exceed that of any map made using galaxy lensing. If the irreducible noise limit can be reached with a sufficiently large radio telescope, the projected convergence map provides a high-fidelity image of the true matter distribution, allowing the dark matter halos of individual galaxies to be viewed directly, and giving a wealth of statistical and morphological information about the relative distributions of mass and light. For instrumental designs like that planned for the Square Kilometer Array (SKA), high-fidelity mass imaging may be possible near the resolution limit of the core array of the telescope.