Particle production during inflation: constraints expected from redshifted 21 cm observations from the epoch of reionization

TL;DR

This paper explores how upcoming 21 cm observations from the epoch of reionization can constrain primordial bump-like features in the scalar power spectrum, using simulated data and Bayesian analysis to assess detectability and parameter biases.

Contribution

It demonstrates the potential of SKA-Low 21 cm data to detect and constrain primordial bump features, accounting for astrophysical uncertainties and foreground removal models.

Findings

21 cm power spectra can probe primordial bump features under ideal conditions.

Decreased bump amplitude increases uncertainties and biases in parameter recovery.

Distinct effects of primordial features and astrophysical parameters can be distinguished.

Abstract

We examine a type of features in the primordial scalar power spectrum, namely, the bump-like feature(s) that arise as a result of burst(s) of particle production during inflation. The latest CMB observations by Planck 2018 can accommodate such features. In the near future, observations of redshifted 21 cm signal from the epoch of reionization can put additional constraints on inflation models by exploiting the expected tomographic information across a wide range of co-moving wave-numbers. In this work, we study the potential of upcoming observational data from SKA-Low to constrain the parameters of the primordial power spectrum with bump-like features. We use simulated mock data expected from SKA-Low, with uncertainties estimated from different foreground removal models, and constrain the parameters of primordial features within a Bayesian framework. We study two scenarios: in the first scenario, where the astrophysical parameters relevant to the evolution of the 21 cm signal are known, we find that 21 cm power spectra do have the potential to probe the primordial bump-like features. As the input amplitude of the bump is decreased below roughly 10% of the amplitude of the primordial power spectrum without the bump, the uncertainties in the recovered values for both amplitude and location of the bump are found to increase, and the recovered values of the location of the bump also get increasingly more biased towards higher values. Hence, it becomes harder to constrain these parameters. In the second scenario, we analyze the achievable constraints on primordial features when two of the astrophysical parameters, namely, minimum halo mass and ionizing efficiency are uncertain. We find that the effect of the bump on the shape and the amplitude of the 21 cm power spectrum is distinct from the impact of varying the astrophysical parameters, and hence they may potentially be distinguished.