Utilizing ASCA archival data of about 300 objects of elliptical galaxies , groups , and clusters of galaxies , we performed systematic measurements of the X-ray properties of hot gas in their systems , and compiled them in this paper .
The steepness of the luminosity–temperature ( LT ) relation , L _ { X } \propto ( kT ) ^ { \alpha } , in the range of kT = 1.5–15 keV is \alpha = 3.17 \pm 0.15 , consistent with previous measurements .
In the relation , we find two breaks at around ICM temperatures of 1 keV and 4 keV : \alpha = 2.34 \pm 0.29 above 4 keV , 3.74 \pm 0.32 in 1.5–5 keV , and 4.03 \pm 1.07 below 1.5 keV .
Such two breaks are also evident in the temperature and size relation .
The steepness in the LT relation at kT > 4 keV is consistent with the scale-relation derived from the CDM model , indicating that the gravitational effect is dominant in richer clusters , while poorer clusters suffer non-gravity effects .
The steep LT relation below 1 keV is almost attributed to X-ray faint systems of elliptical galaxies and galaxy groups .
We found that the ICM mass within the scaling radius R _ { 1500 } follows the relation of M _ { gas } \propto T ^ { 2.33 \pm 0.07 } from X-ray faint galaxies to rich clusters .
Therefore , we speculate that even such X-ray faint systems contain a large-scale hot gas , which is too faint to detect .