Complex Extended Line Emission in the cD Galaxy in Abell 2390

This paper reports maps of the cD galaxy in the rich z = 0.23 cluster Abell 2390 at UV, [O II], Lyα, and Hα wavelengths. Spatially resolved UV and optical spectra were obtained with Space Telescope Imaging Spectrograph on the Hubble Space Telescope; the 2″ wide slit was aligned close to the long axis and blue lane of the galaxy and includes all the inner bright features seen in Wide Field Planetary Camera 2 images. The Lyα is seen in emission from several bright knots and over an extended region from 4″ northwest to 2″ southeast of the nucleus. Three of these knots have detected UV continuum as well. Hα images were obtained with OSIS at the Canada-France-Hawaii Telescope; both Hα and [O II] show extended emission that roughly trace Lyα, primarily to the northwest. Notable differences between the spatial distributions of Hα, Lyα, and [O II] emission and the blue knots in the galaxy may be the result of nonhomogeneous dust extinction or variations in ionization. The Lyα emission velocities depend on the uncertain identification with features in the undispersed images; there is strong evidence for resolved emission knots to have high velocities, ≳1000 km s-1, indicative of infall. The Lyα spectrum shows a sharp cutoff which may be due to absorption; we entertain the possibility that this edge is due to a shell of absorbing gas outflowing at about 5000 km s-1.