Fast radio bursts as probes of feedback from active galactic nuclei

TL;DR

Fast Radio Bursts can be used to probe the effects of Active Galactic Nuclei feedback on the intergalactic medium by analyzing dispersion measure scatter, with upcoming surveys promising significant insights.

Contribution

This study demonstrates that FRB dispersion measure scatter can distinguish different AGN feedback models, providing a new observational method to study galaxy evolution.

Findings

DM-redshift relation is robust against feedback variations

Scatter in DM is larger with weaker AGN feedback

Approximately 10,000 localized FRBs are needed to differentiate feedback models

Abstract

Fast Radio Bursts (FRBs) are a promising tool for studying the low-density universe as their dispersion measures (DM) are extremely sensitive probes of electron column density. Active Galactic Nuclei (AGN) inject energy into the intergalactic medium, affecting the DM and its scatter. To determine the effectiveness of FRBs as a probe of AGN feedback, we analysed three different AGN models from the EAGLE simulation series. We measured the mean DM-redshift relation, and the scatter around it, using $2.56 \times 10^8$ sightlines at 131 redshift ($z$) bins between $0 \leq z \leq 3$. While the DM-redshift relation itself is highly robust against different AGN feedback models, significant differences are detected in the scatter around the mean: weaker feedback leads to more scatter. We find $\sim 10^4$ localised FRBs are needed to discriminate between the scatter in standard feedback and stronger, more intermittent feedback models. The number of FRBs required is dependent on the redshift distribution of the detected population. A log-normal redshift distribution at $z=0.5$ requires approximately 50% fewer localised FRBs than a distribution centred at $z=1$. With the Square Kilometre Array expected to detect $>10^3$ FRBs per day, in the future, FRBs will be able to provide constraints on AGN feedback.