Chandra survey of nearby highly inclined disk galaxies -- V: emission
  structure and origin of galactic coronae
  The origin of the extended soft X-ray emission around nearby highly inclined
disk galaxies (often called as 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 H50or H75and the surface star
formation rate (ISFR) 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 ISFR. 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.
