Projected Constraints on Modified Gravity Cosmologies from 21 cm Intensity Mapping

TL;DR

This paper forecasts how 21 cm intensity mapping can constrain modified gravity models, demonstrating its potential to distinguish between theories like DGP and f(R) by analyzing cosmic structure and lensing effects.

Contribution

It provides the first projected constraints on modified gravity models using 21 cm intensity mapping, highlighting its sensitivity to both expansion history and structure growth.

Findings

A 200m x 200m telescope can distinguish DGP from dark energy models.

Constraints on Hu & Sawicki f(R) model reach |f_{R0}| < 9*10^(-6).

Intensity mapping is a rapid, economical method for probing gravity modifications.

Abstract

We present projected constraints on modified gravity models from the observational technique known as 21 cm intensity mapping, where cosmic structure is detected without resolving individual galaxies. The resulting map is sensitive to both BAO and weak lensing, two of the most powerful cosmological probes. It is found that a 200 m x 200 m cylindrical telescope, sensitive out to z=2.5, would be able to distinguish DGP from most dark energy models, and constrain the Hu & Sawicki f(R) model to |f_{R0}| < 9*10^(-6) at 95% confidence. The latter constraint makes extensive use of the lensing spectrum in the nonlinear regime. These results show that 21 cm intensity mapping is not only sensitive to modifications of the standard model's expansion history, but also to structure growth. This makes intensity mapping a powerful and economical technique, achievable on much shorter time scales than optical experiments that would probe the same era.