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2001MNRAS.323..965S - Mon. Not. R. Astron. Soc., 323, 965-987 (2001/June-1)
The evidence for jet-cloud interactions in a sample of high-redshift radio galaxies.
SOLORZANO-INARREA C., TADHUNTER C.N. and AXON D.J.
Abstract (from CDS):
While the emission-line kinematics provide strong evidence for shock acceleration, the dominant ionization mechanism for the emission-line gas remains uncertain. We have compared the optical diagnostic line ratios of the galaxies in our sample with various ionization models, including pure-shock ionization, shocks including a photoionized precursor, power-law photoionization, and photoionization including matter-bounded clouds. We find that both pure-shock ionization and power-law photoionization model predictions fail to provide good fits to the data. On the other hand, on individual diagnostic diagrams, models for shocks which include a photoionized precursor are consistent with the results for the majority of the extended emission-line regions (EELR) of the galaxies in our sample, and photoionization including matter-bounded clouds models also give reasonable fits to some of the EELR. However, in terms of the positions of the points relative to the model sequences on the diagnostic diagrams, there is a lack of consistency from diagram to diagram. The diagnostic diagram involving the line ratios [Oiii](4959+5007)/4363 and Heii(4686)/Hβ is particularly problematic in this regard. Overall, our results suggest that, if the EELR are shock-ionized, one or more of the assumptions implicit in the shock models may need to be reconsidered.
In addition, we have investigated the nebular continuum contribution to the UV excess in the galaxies in our sample. We find a substantial nebular emission contribution to the UV continuum in all the cases, in the range ∼10-40 per cent. However, after the subtraction of the nebular component, a significant UV excess remains in the extended nebulae of most of the objects.
Abstract Copyright: The Royal Astronomical Society
Journal keyword(s): galaxies: active - galaxies: jets - galaxies: kinematics and dynamics
Simbad objects: 13
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