Do Jet-driven Shocks Ionize the Narrow-Line Regions of Seyfert Galaxies?

We consider a model in which the narrow line regions (NLRs) of Seyfertgalaxies are photoionized ``in situ'' by fast (300 -- 1,000 km/s), radiativeshock waves driven into the interstellar medium of the galaxy by radio jetsfrom the active nucleus. Such shocks are powerful sources of soft X-rays. Wecompute the expected ratio of the count rates in the ROSAT PSPC and EinsteinIPC detectors to the [OIII] \lambda 5007 flux as a function of shock velocity,and compare these ratios with observations of type 2 Seyferts. If most of theobserved soft X-ray emission from these galaxies originates in the NLR and theabsorbing hydrogen column is similar to that inferred from the reddening of theNLR, a photoionizing shock model with shock velocity $\simeq$ 400 -- 500 km/sis compatible with the observed ratios. High angular resolution observationswith AXAF are needed to isolate the X-ray emission of the NLR and measure itsabsorbing column, thus providing a more conclusive test. We also calculate theexpected coronal iron line emission from the shocks. For most Seyfert 2s, the[Fe X] \lambda 6374/H \beta$ ratio is a factor of 2 -- 14 lower than thepredictions of 300 -- 500 km/s shock models, suggesting that less hot gas ispresent than required by these models.Comment: Astrophys J. Letters 1999 March 10 issue, Vol. 51