From Rosat data on normal and interacting galaxies we found that two
components are required to explain the ROSAT PSPC spectra of most
ellipticals and that the hot gas component increases with x-ray excess.
From XMM-Newton and Chandra data we showed that youthful ellipticals
(from optical spectroscopy) are X-ray poor, whereas older ellipticals
can possess massive hot gas halos in some cases.
See ISM page for details.
Above is an x-ray image of a normal, isolated elliptical, showing emission from hot gas.