Extended Neutral Hydrogen Emission in the NGC 5903/5898 Binary Elliptical System: Evidence for a Double-Galaxy Accretion Event

Neutral hydrogen observations made with the VLA are presented of the remarkable binary elliptical system NGC 5898/5903. NGC 5898 has been shown by Bertola and Bettoni to contain ionized gas which counterrotates with respect to the stars suggesting that the gas has been acquired from outside the galaxy. Although no H I was detected from NGC 5898, extended emission, including long filaments, was found in and around the companion NGC 5903. The results suggest that NGC 5903 is currently undergoing a major accretion event which may be linked to a similar event which occurred at an earlier time in NGC 5898. Within NGC 5903 the H I is consistent with the early development of an accretion disk parallel to the minor axis of the optical isophotes. The kinematics of the gas and asymmetry of the H I distribution suggest that the accretion has occurred recently (T = 2 x 10^8^ yr) and the H I is not in a state of equilibrium with the potential of the galaxy. The infalling gas may also be responsible for the usual radio continuum emission which peaks near the center of NGC 5903 but extends outside the optical dimensions of the galaxy.