# Radiation-pressure-driven dust transport to galaxy halos at $z\sim 10$

## TL;DR

This study investigates how radiation pressure in early high-redshift galaxies can transport dust grains to galaxy halos, highlighting the conditions under which dust can escape the galactic disc and enrich the circum-galactic medium.

## Contribution

It presents a detailed model of dust grain dynamics considering radiation pressure, gas drag, and gravity, revealing the specific conditions for dust escape at $z\,\sim 10$.

## Key findings

- Dust grains of radius ~0.1 μm can escape if star formation exceeds 15% baryon conversion.
- Grains larger or smaller than 0.1 μm are trapped by gravity or gas drag.
- Optimal dust-to-gas ratio is ~10^{-3} for effective dust transport.

## Abstract

The origin of dust in galaxy halos or in the circum-galactic medium (CGM) is still a mystery. We investigate if the radiation pressure in high-redshift ($z\sim 10$) galaxies can efficiently transport dust to halos. To clarify the first dust enrichment of galaxy halos in the early Universe, we solve the motion of a dust grain considering radiation pressure, gas drag, and gravity in the vertical direction of the galactic disc. Radiation pressure is estimated in a consistent manner with the stellar spectra and dust extinction. As a consequence, we find that dust grains with radii $a\sim 0.1~\mu$m successfully escape from the galactic disc if the ongoing star formation episode converts more than 15 per cent of the baryon content into stars and lasts $\gtrsim 30$ Myr, while larger and smaller grains are trapped in the disc because of gravity and gas drag, respectively. We also show that grain charge significantly enhances gas drag at a few--10 scale heights of the galactic disc, where the grain velocities are suppressed to $\sim 1$ km s$^{-1}$. There is an optimum dust-to-gas ratio ($\sim 10^{-3}$) in the galactic disc and an optimum virial mass $\sim 10^{10}$--$10^{11}$ M$_{\odot}$ for the transport of $a\sim 0.1~\mu$m grains to the halo. We conclude that early dust enrichment of galaxy halos at $z\gtrsim 10$ is important for the origin of dust in the CGM.