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Discussion

Figure 1 presents our final H$\alpha $ images of MR 2251-178 at each of the two etalon spacings (panels a and b), as well as the I-band continuum image (panel c) and a combined H$\alpha $ image (panel d). The 2-$\sigma$ detection limit of the H$\alpha $ images is $\sim$ 5 $\times $ 10-18 erg s-1 cm-2 arcsec-2, more than an order of magnitude fainter than previously published data on this object. In the discussion that follows, we assume H0 = 50 km s-1 Mpc-1 and a corresponding image scale of 1.9 kpc arcsec-1.


  
Figure 1: Deep H$\alpha $ images of the field surrounding the quasar MR 2251-178. Panels a and b are 1200 second exposures at redshifts of 0.0640 and 0.0645, respectively, panel c is an I-band continuum image of the same field, and panel d is a summed H$\alpha $ image. A bright star (S), a nearby cluster galaxy (G1), and a number of emission-line knots from Macchetto et al. (1990) have been labeled. All panels are $3\arcmin\times2.5\arcmin$ in size, with north up and east to the left. The lowest contour in panels a and b represents a surface brightness level of $1.2 \times 10^{-17}$erg s-1 cm-2 arcsec-2, while that of panel d corresponds to $1.8 \times 10^{-17}$erg s-1 cm-2 arcsec-2.
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Patrick Shopbell
1999-08-26