Chandra Survey of Nearby Highly Inclined Disc Galaxies - II: Correlation Analysis of Galactic Coronal Properties

TL;DR

This study analyzes X-ray data of nearby disc galaxies to understand their coronal properties, revealing correlations with star formation, supernova energy input, and galaxy mass, and comparing these with elliptical galaxies.

Contribution

It provides new insights into the relationships between X-ray luminosity, supernova feedback, and galaxy mass in disc galaxies, expanding understanding beyond elliptical galaxy studies.

Findings

Coronal X-ray luminosity correlates strongly with star formation rate and supernova energy input.

X-ray radiation efficiency averages around 0.4% and depends on galaxy mass and supernova surface density.

Disc galaxy coronae are more luminous and hotter than those of elliptical galaxies of similar mass.

Abstract

X-ray observations provide a key tool for exploring the properties of galactic coronae and their formation processes. In an earlier paper, we have presented a Chandra data analysis of the coronae of 53 nearby highly-inclined disc galaxies. Here we study the correlation of the X-ray measurements with other galaxy properties and compare the results with those obtained for elliptical galaxies. A good correlation is present between the coronal luminosity Lx and the SFR. But we find a better correlation between Lx and the total SN mechanical energy input rate (ESN), including the expected contribution from core collapsed (CC) and Ia SNe. The X-ray radiation efficiency (eta=Lx/ESN) has a mean value of ~0.4% with an rms of ~0.5dex. eta further correlates with MTF/M* (MTF is the baryon mass measured from the rotation velocity and the Tully-Fisher relation, M* is the stellar mass measured from the K-band luminosity) and the CC SN rate surface density (FSN, in units of SN/yr/kpc^2), which can be characterized as: eta=0.41%MTF/M* and eta=1.4%FSN^-0.3. These correlations reflect the roles played by the gravitational mass and energetic feedback concentrations in determining eta. The characteristic temperature of the corona shows little dependence on the total or specific SFR, the cold gas content, or Lx. The coronae of disc galaxies tend to be more X-ray luminous, hotter, and lower in Fe/O abundance ratio than those of elliptical ones of similar masses. Early-type non-starburst disc galaxies tend to be more Fe-rich, while starburst ones have a roughly constant abundance ratio of Fe/O~0.36solar. Our results are consistent with the coronal gas being mainly provided by stellar feedback in a mass range of M*~10^{8.7-11}Msun. In addition, processes such as charge exchange at cool/hot gas interfaces, as well as various environmental effects, are also needed to explain the diversity of coronal properties.