A relation between UV excess and the interstellar medium in elliptical galaxies ?

Abstract

We have obtained IUE spectra of the nuclear region of the dust-lane elliptical galaxy NGC 7196, with the intention of investigating a possible relationship between UV excess and the presence of a cool interstellar medium component in elliptical galaxies. This galaxy has a smooth, compact major-axis dust lane and no known nuclear activity. Excess UV emission comparable to that in M87 is present at wavelenghts shortward of λ~2000 A, although the spectrum at longer (λ~2500-3000 A) wavelenghts is redder than that of the 'standard' elliptical galaxy NGC 3379. The observations combined with IRAS data are used to investigate the present day star formation rate, and we discuss a model in which the long wavelength reddening is caused by a diffuse dusty medium rich in small grains. It is pointed out that heating of the dust lane by a hot, low-density atmosphere (common in elliptical galaxies) could provide a significant contribution to the infrared flux.