# The Radio Scream from Black Holes at Cosmic Dawn: A Semi-Analytic Model for the Impact of Radio Loud Black-Holes on the 21 cm Global Signal

## TL;DR

This paper models how early radio-loud black holes could have significantly affected the 21 cm signal during Cosmic Dawn, suggesting future radio surveys can test these scenarios.

## Contribution

It introduces a semi-analytic model linking radio-loud black hole activity to the 21 cm signal, providing new insights into early black hole impact on cosmic evolution.

## Key findings

- Radio-loud black holes could alter the 21 cm signal by tens to hundreds of percent.
- Certain parameters reproduce EDGES absorption features and predict detectable point sources.
- Future SKA surveys can constrain early black hole activity scenarios.

## Abstract

We use a semi-analytic model to explore the potential impact of a brief and violent period of radio-loud accretion onto black-holes (The Radio Scream) during the Cosmic Dawn on the HI hyperfine 21 cm signal. We find that radio emission from super-massive black hole seeds can impact the global 21 cm signal at the level of tens to hundreds of percent provided that they were as radio loud as $z\approx1$ black holes and obscured by gas with column depths of $N_\text{H}\gtrsim 10^{23}$ cm$^{-2}$. We determine plausible sets of parameters that reproduce some of the striking features of the EDGES absorption feature including its depth, timing, and side steepness while producing radio/X-ray backgrounds and source counts that are consistent with published limits. Scenarios yielding a dramatic 21 cm signature also predict large populations of $\sim \mu$Jy point sources that will be detectable in future deep surveys from the Square Kilometer Array (SKA). Thus, 21 cm measurements, complemented by deep point source surveys, have the potential to constrain optimistic scenarios where super-massive black-hole progenitors were radio-loud.