) imaging of the
ionized gas surrounding the low-redshift (
) quasar MR 2251-178 using the Taurus Tunable Filter on the AAT telescope. Our
observations detect ionized gas out to a radius of 120 kpc, the
deepest detection yet in this system. The total mass of ionized gas
is
M
(upper limit). The large and symmetric
extent of the gaseous envelope favors a model in which the filamentary
and diffuse emission arises from a large cloud complex, photo-excited
by the bright quasar. A crude kinematic analysis does not support an
origin for the gas in an interaction with the nearby galaxy G1. We
conclude that significant quantities of ionized gas in the galactic
environment may go undetected with current observational techniques.