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], Ly alpha, and Ha wavelengths. Spatially resolved UV an d optical spectra were obtained with Space Telescope Imaging Spectrograph o n the Hubble Space Telescope; the 2 " wide slit was aligned close to the lo ng axis and blue lane of the galaxy and includes all the inner bright featu res seen in Wide Field Planetary Camera 2 images. The Ly alpha is seen in e mission from several bright knots and over an extended region from 4 " nort hwest to 2 " southeast of the nucleus. Three of these knots have detected U V continuum as well. H alpha images were obtained with OSIS at the Canada-F rance-Hawaii Telescope; both H alpha and [O II] show extended emission that roughly trace Ly alpha, primarily to the northwest. Notable differences be tween the spatial distributions of H alpha, Ly alpha, and [O II] emission a nd the blue knots in the galaxy may be the result of nonhomogeneous dust ex tinction or variations in ionization. The Ly alpha emission velocities depe nd on the uncertain identification with features in the undispersed images; there is strong evidence for resolved emission knots to have high velociti es, greater than or similar to 1000 km s(-1), indicative of infall. The Ly alpha spectrum shows a sharp cutoff which may be due to absorption; we ente rtain the possibility that this edge is due to a shell of absorbing gas out flowing at about 5000 km s(-1).