# Gas around galaxy haloes - III: hydrogen absorption signatures around galaxies and QSOs in the Sherwood simulation suite

## TL;DR

This study uses the Sherwood simulations to compare hydrogen absorption signatures around star-forming galaxies and QSOs, revealing different extents of gaseous influence likely due to distinct feedback mechanisms.

## Contribution

It provides a quantitative analysis of hydrogen absorption around galaxies and QSOs, highlighting the role of feedback processes in shaping gaseous environments.

## Key findings

- Hydrogen absorption extends up to 150 kpc around star-forming galaxies.
- Absorption extends up to 300-700 kpc around QSOs.
- Supernova-driven winds explain absorption around star-forming galaxies, but not QSOs.

## Abstract

Modern theories of galaxy formation predict that galaxies impact on their gaseous surroundings, playing the fundamental role of regulating the amount of gas converted into stars. While star-forming galaxies are believed to provide feedback through galactic winds, Quasi-Stellar Objects (QSOs) are believed instead to provide feedback through the heat generated by accretion onto a central supermassive black hole. A quantitative difference in the impact of feedback on the gaseous environments of star-forming galaxies and QSOs has not been established through direct observations. Using the Sherwood cosmological simulations, we demonstrate that measurements of neutral hydrogen in the vicinity of star-forming galaxies and QSOs during the era of peak galaxy formation show excess LyA absorption extending up to comoving radii of about 150 kpc for star-forming galaxies and 300 - 700 kpc for QSOs. Simulations including supernovae-driven winds with the wind velocity scaling like the escape velocity of the halo account for the absorption around star-forming galaxies but not QSOs.