# Radio Emission from Accreting Isolated Black Holes in Our Galaxy

## TL;DR

This paper investigates radio emissions from isolated black holes in our galaxy caused by accretion-induced shocks, estimating their detectability with SKA surveys and potential for revealing black hole properties.

## Contribution

It models electron acceleration and radio emission from isolated black holes, providing estimates for their detectability with upcoming radio surveys like SKA.

## Key findings

- Approximately 30 IBHs detectable by SKA1-mid in optimistic scenarios.
- Around 700 IBHs could be detected by SKA2.
- Parallax measurements can determine distances and properties of these black holes.

## Abstract

Apart from the few tens of stellar-mass black holes discovered in binary systems, an order of $10^8$ isolated black holes (IBHs) are believed to be lurking in our Galaxy. Although some IBHs are able to accrete matter from the interstellar medium, the accretion flow is usually weak and thus radiatively inefficient, which results in significant material outflow. We study electron acceleration generated by the shock formed between this outflow and the surrounding material, and the subsequent radio synchrotron emission from accelerated electrons. By numerically calculating orbits of IBHs to obtain their spatial and velocity distributions, we estimate the number of IBHs detectable by surveys using SKA1-mid (SKA2) as $\sim 30$ ($\sim 700$) for the most optimistic case. The SKA's parallax measurements may accurately give their distances, possibly shedding light on the properties of the black holes in our Galaxy.