Hot Gaseous Coronae around Spiral Galaxies: Probing the Illustris Simulation

TL;DR

This study uses Chandra X-ray observations to set limits on hot gaseous coronae around lower mass spiral galaxies and compares these limits with predictions from the Illustris simulation, finding broad agreement in some properties.

Contribution

It provides observational constraints on hot coronae around lower mass spirals and evaluates the Illustris simulation's accuracy in modeling these features.

Findings

Observed upper limits on X-ray luminosity and gas mass are consistent with model predictions.

Gas temperatures, metal abundances, and electron density profiles broadly agree with Illustris.

Illustris physics modules are generally consistent with observed properties of spiral galaxy coronae.

Abstract

The presence of hot gaseous coronae around present-day massive spiral galaxies is a fundamental prediction of galaxy formation models. However, our observational knowledge remains scarce, since to date only four gaseous coronae were detected around spirals with massive stellar bodies ($\gtrsim2\times10^{11} \ \rm{M_{\odot}}$). To explore the hot coronae around lower mass spiral galaxies, we utilized Chandra X-ray observations of a sample of eight normal spiral galaxies with stellar masses of $(0.7-2.0)\times10^{11} \ \rm{M_{\odot}}$. Although statistically significant diffuse X-ray emission is not detected beyond the optical radii ($\sim20$ kpc) of the galaxies, we derive $3\sigma$ limits on the characteristics of the coronae. These limits, complemented with previous detections of NGC 1961 and NGC 6753, are used to probe the Illustris Simulation. The observed $3\sigma$ upper limits on the X-ray luminosities and gas masses exceed or are at the upper end of the model predictions. For NGC 1961 and NGC 6753 the observed gas temperatures, metal abundances, and electron density profiles broadly agree with those predicted by Illustris. These results hint that the physics modules of Illustris are broadly consistent with the observed properties of hot coronae around spiral galaxies. However, a shortcoming of Illustris is that massive black holes, mostly residing in giant ellipticals, give rise to powerful radio-mode AGN feedback, which results in under luminous coronae for ellipticals.