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Astron. Astrophys. 327, 909-920 (1997)

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6. Conclusions

We have studied the possibility that dense matter-bounded clouds are responsible for the emission of the coronal lines in the Circinus galaxy. In our scheme, the clouds emitting the coronal lines have a much higher ionization parameter ([FORMULA]) than those responsible for the rest of the narrow lines. Further, the high values of [FORMULA] implied by the observed [Si IX ]/[Si VI ] ratio implies that radiation pressure exceeds gas pressure. We have incorporated the effects of radiation pressure into our calculations and shown that strong density gradients result. The density gradient is similar to the case [FORMULA] discussed by Binette & Raga (1990). The agreement between our density stratified MB model and the observed coronal line ratios in Circinus is very encouraging, and leads us to suspect that the blueshift characterizing the coronal gas might result from radiative acceleration.

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© European Southern Observatory (ESO) 1997

Online publication: April 6, 1998