SIMBAD references

The origin of the extended soft X-ray emission around nearby highly inclined disk galaxies (often called the X-ray corona) remains uncertain. The emission could arise from volume-filling hot gas and/or its interaction with cool gas. Morphological properties of the X-ray emission can provide additional information to distinguish these different origins. We define model-independent parameters H₅₀, H₇₅, and H₉₅-vertical scales that enclose 50%, 75%, and 95% of the total flux of the emission, respectively. We study the correlation of these parameters with galaxy properties inferred from infrared observations of a sample of nearby highly inclined disk galaxies with high-quality Chandra data. We find weak negative correlations between H₅₀ or H₇₅ and the surface star formation rate (I_SFR), and no correlation for H₉₅. However, we detect strong negative correlations of the vertical concentration of the emission, defined as H₅₀/H₉₅ or H₇₅/H₉₅, with I_SFR. Our findings suggest that the X-ray emission around disk galaxies is likely comprised of two components: the extended, weak emission, characterized by H₉₅, is influenced by the outflowing hot gas entrained in star formation driven winds, whereas the strong emission close to the disk, which is often rich in cool gas characterized by H₅₀ or H₇₅, is largely impacted by cool-hot gas interaction.