Observations

First discovered as a strong and variable X-ray source (Cooke et al. 1978), MR 2251-178 was subsequently identified as a quasar at a redshift of $0.0638$ (Canizares et al. 1978). Optical imagery and spectroscopy have detected two ionized gas components around the quasar: an elongated, highly-ionized circum-nuclear component of diameter $\sim27$ kpc, and an extended envelope of faint H$\alpha$- and [OIII]-emitting filaments out to a radius of $\sim 110$ kpc (e.g., Bergeron et al. 1983; Macchetto et al. 1990). Spectroscopic observations have determined that the extended ionized gas component, while undoubtedly associated with the quasar, is not following its rotation pattern (Nørgaard-Nielsen et al. 1986; Mulder & Valentijn 1992).

Figure 1 presents our H$\alpha$ imagery of MR 2251-178. In the discussion that follows, we assume $H_0 = 50$ km s$^{-1}$ Mpc$^{-1}$ and a corresponding image scale of 1.9 kpc arcsec$^{-1}$.

Figure 1: Deep imagery of the field surrounding the quasar MR 2251-178. Panels $a$ and $b$ are 1200 second exposures of H$\alpha$ at redshifts of 0.0640 and 0.0645, respectively. Panel $c$ is an I-band continuum image of the same field, illustrating a number of galaxies in the cluster. Panel $d$ is a summed H$\alpha$ image. All panels are 3 in size, with north up and east to the left.