A survey of elliptical galaxy spectra using image-tube spectrograms has been carried out with the result that 40 percent of the galaxies have been found to contain ionized gas. Galaxies with intense nuclear emission also tend to have extended emission that appears to be confined to a plane. Since there is a detectable velocity gradient for the gas in those planes, the gas appears to be in a rotating disk.
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Nelson Caldwell (1984) studied this question.