# Tracing the Origins of Hot Halo Gas in Milky Way-Type Galaxies with SMUGGLE

## TL;DR

This study uses high-resolution simulations with the SMUGGLE framework to analyze the properties of hot gaseous halos around Milky Way-like galaxies, comparing results with X-ray observations and identifying key feedback mechanisms.

## Contribution

It demonstrates that stellar feedback models can match observed X-ray luminosities but fail to reproduce the extended surface brightness profile, highlighting the need for additional heating processes.

## Key findings

- Stellar feedback shapes the inner hot atmosphere within 5 kpc.
- Models underpredict extended X-ray emission by 1-2 orders of magnitude.
- Additional mechanisms like AGN feedback are needed for the full hot halo.

## Abstract

Current galaxy formation models predict the existence of X-ray-emitting gaseous halos around Milky Way (MW)-type galaxies. To investigate properties of this coronal gas in MW-like galaxies, we analyze a suite of high-resolution simulations based on the SMUGGLE framework and compare the results with X-ray observations of both the MW and external galaxies. We find that for subgrid models incorporating any form of stellar feedback, e.g., early feedback (including stellar winds and radiation) and/or supernova (SN) explosions, the total 0.5-2 keV luminosity is consistent within uncertainties with X-ray observations of the MW and with scaling relations derived for external disk galaxies. However, all models exhibit an X-ray surface brightness profile that declines too steeply beyond $\sim5$ kpc, underpredicting the extended emission seen in recent eROSITA stacking results. Across all subgrid prescriptions, the simulated surface brightness and emission measure fall below MW observations by at least 1-2 orders of magnitude, with the most severe discrepancy occurring in the no-feedback model. Our results suggest that (i) stellar feedback primarily shapes the innermost hot atmosphere (central $\sim5$ kpc), with comparable contributions from early feedback and SNe to the resulting X-ray luminosity; (ii) additional mechanisms such as gravitational heating, active galactic nuclei feedback, and/or Compton effects of GeV cosmic ray are necessary to generate the extended, volume-filling hot gaseous halo of MW-mass galaxies; (iii) the origins of hot corona in MW-like galaxies are partially distinct from those of the warm ($\sim10^5$ K) gas, by combining our previous finding that the SMUGGLE model successfully reproduces the kinematics and spatial distribution of MW O VI absorbers.