Star formation in nuclei of SO/E galaxies.

Abstract

Spectra of nuclei for some lenticular and elliptical galaxies observed from the IUE satellite in the far-UV light are analyzed with the help of the IUE spectral atlases using an almost similar resolution for galaxies and stars, down to about 8A for a significant signal/noise ratio. In the 2500A-3150A wavelength range, all gas-poor galaxies show 'recent' star formation, up to F5-F8 stars and a similar mean spectral type F8/G2, estimated from a fit in the continuum as well as in the Mg lines. The corresponding 5 Gyr age of these F8 stars indicates star formation more recent than previously thought about the turn-off point of the classical models of early-type galaxies. The spectral distribution of the gas-rich S0 galaxy NGC 5102 is dominated by an A2 spectral type with contribution of B stars. This confirms the previous results in visible light implying a high star formation rate for this typical 'E + A' galaxy.