SIMBAD references

We consider a model in which the narrow-line regions (NLRs) of Seyfert galaxies are photoionized ``in situ'' by fast (300-1000 km.s^–1) radiative shock waves driven into the interstellar medium of the galaxy by radio jets from the active nucleus. Such shocks are powerful sources of soft X-rays. We compute the expected ratio of the count rates in the ROSAT PSPC and Einstein IPC detectors to the [O III] λ5007 flux as a function of shock velocity, and we compare these ratios with observations of type 2 Seyfert galaxies. If most of the observed soft X-ray emission from these galaxies originates in the NLR and the absorbing hydrogen column is similar to that inferred from the reddening of the NLR, a photoionizing shock model with a shock velocity of ≃400-500 km.s^–1 is compatible with the observed ratios. High angular resolution observations with the Advanced X-Ray Astrophysics Facility are needed to isolate the X-ray emission of the NLR and measure its absorbing column, thus providing a more conclusive test. We also calculate the expected coronal iron line emission from the shocks. For most Seyfert 2 galaxies, the [Fe X] λ6374/Hβ ratio is a factor of 2-14 lower than the predictions of 300-500 km.s^–1 shock models, suggesting that less hot gas is present than required by these models.