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The S0/Sa galaxy NGC~5548 hosts a Seyfert~1 nucleus. Echo mapping of its broad optical-line-emitting region yields a radial extent R~\lapprox~20~light days $= \frac{1}{60}$~pc, or $70~h$~microarcseonds for $H_0 = 100~h$~km~s$^{-1}$~Mpc$^{-1}$ (Peterson 1993). Using data from larger radii, what boundary conditions can be imposed on the geometry and velocity field of the broad line region?
\noindent {$\bullet$} R~\lapprox~1400~$h^{-1}$~pc: Bipolar radio continuum lobes straddle a central radio component in NGC~5548. These lobes, which emit optically-thin synchrotron radiation with a 4-cm power of $10^{21}~h^{-2}$~W~Hz$^{-1}$, trace bipolar outflow from the nucleus (Wilson \& Ulvestad 1982; Wrobel 1994).
\noindent {$\bullet$} R~\lapprox~720~$h^{-1}$~pc: The radio lobes of NGC~5548 share the elongation position angle of the [OIII] narrow-line gas, with the broadest known line widths occuring NW of the nucleus at these radii (Wilson et al.\ 1989). This hints that some narrow-line gas receives additional mechanical energy from the bipolar outflow feeding the radio lobes, a situation analogous to the narrow-line superbubble in NGC~3079 (Veilleux et al.\ 1994).
\noindent {$\bullet$} R~\lapprox~10~$h^{-1}$~pc: Blueshifted absorption in the broad CIV lines proves that some gas is flowing out of the nucleus of NGC~5548, with observed speeds of 1200~km~s$^{-1}$ relative to systemic (Shull \& Sachs 1993). This absorption line outflow may have, or be able to achieve, a bipolar shape via the disk-focusing scheme proposed for NGC~3079 (Duric \& Seaquist 1988; Veilleux et al.\ 1994).
