Very extended ionized gas in radio galaxies-I. A radio, optical and ultraviolet study of PKS 2158-380.
Boksenberg, A.; Penston, M. V.; Snijders, M. A. J.; Wamsteker, W.; Disney, M. J.; Fosbury, R. A. E.; Wilson, A. S.; Goss, W. M.; Danziger, I. J.; Wellington, K. J.
United Kingdom, Germany, Netherlands, Spain, Chile, Australia, United States
Abstract
IUE observations of PKS 2158-380 show gas in a high state of ionization extending out to a radius of 15 kpc, with a spectrum which is inconsistent with local photoionization by hot stars, and a UV point source at the nucleus which can be fitted by a power law with a spectral index of -1.4. If the gas is distributed within the galaxy in such a way as to cover a large fraction of the sky at large distances from the nucleus, the UV source is sufficiently luminous to photoionize the entire emission line region. It is suggested that this sky coverage can be obtained if the gas is in the form of a severely warped disk, which may have resulted from the capture and disruption of a small, gas-rich galaxy's elliptical. The capture of gas by an elliptical galaxy, and the subsequent dissipative evolution, may be responsible for the nuclear activity observed in some radio galaxies.