MR 2251-178 : a nearby QSO embedded in a giant H II envelope.
Tarenghi, M.; Boksenberg, A.; Bergeron, J.; Dennefeld, M.
France, United Kingdom, Germany
Abstract
Spectra of MR 2251-178 and surrounding galaxies were obtained and analyzed. The kinematics of the extended region, the spectra of the QSO and nebulosity, and the galaxies of the surrounding cluster are discussed. The QSO lies in the nucleus of a galaxy having a gaseous component of very high ionization, high temperature and relatively low abundance and is surrounded by a giant H II envelope observed in the forbidden O III region. The ionized matter in the envelope extends over a region of at least 230 x 60 kpc and is not associated with any apparent nebulosity; its velocity field resembles those of observed H I envelopes. A clear rotation pattern is seen close to the QSO with a velocity gradient of 17 km/s/kpc out to 6 kpc. An upper limit of 0.2/cu cm is derived for the density in the envelope; the mass of ionized gas is less than 5 x 10 to the 11th solar masses. It is confirmed that the QSO lies in the outskirts of a small cluster of galaxies.