Do Jet-driven Shocks Ionize the Narrow-Line Regions of Seyfert Galaxies?
Abstract
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1999
- DOI:
- 10.1086/311923
- arXiv:
- arXiv:astro-ph/9901329
- Bibcode:
- 1999ApJ...513L.115W
- Keywords:
-
- GALAXIES: ACTIVE;
- GALAXIES: ISM;
- GALAXIES: JETS;
- GALAXIES: NUCLEI;
- GALAXIES: SEYFERT;
- SHOCK WAVES;
- Galaxies: Active;
- Galaxies: ISM;
- Galaxies: Jets;
- Galaxies: Nuclei;
- Galaxies: Seyfert;
- Shock Waves;
- Astrophysics
- E-Print:
- Astrophys J. Letters 1999 March 10 issue, Vol. 513