but the measurement of $\beta$ is a 4-$\sigma$ result. The precession period of the jet is $T=2 \pi \theta_m/(\alpha v)$, which for a precession opening angle of 30$^\circ$, would be about 5500 years. Since the range in PA among the components is about 25$^{\circ}$ (see Fig. 7), the jet travel time to outer components is about 300 years.

We might expect that the sources excited by the passing jet would persist after the jet moves on. However, there is no evidence (see Fig. 8) of structure in the transverse direction in any of the sources. This absence of “trails” suggests that the decay times for emission must be less than $\sim~100$ years, which would produce an extension of 1.5$''$ at the radius of sources N-1 and S-1. The recombination time for an H II region with electron density $n_e$ is estimated as $$\left(\frac{t}{\mbox{yr}}\right)=1.2\times10^5\left(\frac{n_e}{\mbox{cm}^{-3}}\right)^{-1}.~~~~~~(11)$$

The spectral index of N-1 indicates it is probably a thermal optically thin HII region (Rodriguez et al. 2005). Using the values for the flux density and size in Table 1 we estimate a emission measure of $1.8\times10^6$ cm$^{-6}$ pc$^{-1}$ and the electron density as $n_e=1.1\times10^4$ cm$^{-3}$. Using this value for the electron density in eqn. (10) 