Interstellar Matter in Elliptical Galaxies. II.

Abstract

Observations are presented of the emission lines resulting from ionizedinterstellar gas in elliptical galaxies, together with a preliminaryaccount of their interpretation. The strongest line (with respect to thecontinuous spectrum) is the [0 ii] 3727 line, which occurs in differentstrengths in different , down to vanishingly weak intensity. The profileof this line in NGC 4486, the radio source Virgo A, is broad and double.In NGC 4278, an otherwise typical elliptical galaxy with stronginterstellar emission line, estimates of the mass, rotational velocity,and turbulent velocity of the ionized gas are given, as well as relativeabundances of the observable ions. The mechanism by which the energythat is radiated in the emission lines is replaced is not known, but itmay be either from ultraviolet stellar radiation t)r from the conversionof stellar kinetic energy ultimately into heat. It is probable that allelliptical contain interstellar gas and that the observed relativestrength or absence of emission lines is largely an effect ofionization. The similarities and differences between the gas cloud inthe nucleus of the elliptical galaxy NGC 4278 and the gas clouds in thenuclei of our Galaxy, of M31, and of M81 are briefly discussed.