edge of, but inside, the eastern half of the shell, and the other similarly positioned on the western half. Note that the radius of the shell in this fit is 8% larger than that obtained by fitting to a shell alone. The resulting model, image and residual are all shown in the second row of Figure \[fig\_models\]. The image corresponding to the model now reasonably approximates the morphology seen in the real data, and the residuals are greatly reduced (maximum fractional residual of $\sim$5%) when compared to the case of a shell alone.

We can further improve the fit between the model and the data by increasing the number of point sources in the model. In the bottom row of Figure \[fig\_models\], we show a fit to the 1998.0 data involving a spherical shell plus seven point sources. The large number of free parameters (25 in this case) makes finding an absolute minimum in $\chi^2$ very difficult — thus the “best fit” we have shown was found by trial-and-error. The shell has flux density 11.4 mJy and radius 072 (2% smaller than in the case of a shell alone); the point sources range in flux density between 0.3 and 3.5 