Interstellar Matter in Elliptical Galaxies. II.

Observations are presented of the emission lines resulting from ionized interstellar gas in elliptical galaxies, together with a preliminary account of their interpretation. The strongest line (with respect to the continuous spectrum) is the 0 ii 3727 line, which occurs in different strengths in different , down to vanishingly weak intensity. The profile of this line in NGC 4486, the radio source Virgo A, is broad and double. In NGC 4278, an otherwise typical elliptical galaxy with strong interstellar emission line, estimates of the mass, rotational velocity, and turbulent velocity of the ionized gas are given, as well as relative abundances of the observable ions. The mechanism by which the energy that is radiated in the emission lines is replaced is not known, but it may be either from ultraviolet stellar radiation t)r from the conversion of stellar kinetic energy ultimately into heat. It is probable that all elliptical contain interstellar gas and that the observed relative strength or absence of emission lines is largely an effect of ionization. The similarities and differences between the gas cloud in the nucleus of the elliptical galaxy NGC 4278 and the gas clouds in the nuclei of our Galaxy, of M31, and of M81 are briefly discussed.