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S. M. Simkin, B. I. Grimberg (Michigan State University)
There are, very few studies of the EELG in the inner regions of nearby, powerful, double--lobed radio galaxies (FR II objects). Such studies are important because they may allow us to identify those processes which involve the interaction between the galaxy's ISM and the ejected radio plasma close to the nucleus, before the jet plasma has been modified by aging and interaction with multiple clouds of gas.
We have obtained such measurements for the EELG in Pictor A and PKS 349-27. These measurements suggest that there may be significant differences between the gas in the outer regions of these objects (such as the lobes) and that the gas closer to the nucleus may be subject to more powerful disruption. In particular, we find that that the values for [NII] : H\alpha are lower than those usually found for active galaxy nuclei with similar values of [OI] : H\alpha, In addition, there are reports in the literature of other EELG with low [NII] : H\alpha.
Although there are several competing models for calculating the expected emission line ratios from shock heating and/or UV continuum excitation and ionization for the EELR in galaxies as well as the nuclear regions of AGNs, none of these models reproduce the extreme values of the [OI] and [NII] : H\alpha ratios which we find here.
We postulate that he extremely low emisivity for [NII] which we see in the case of Pictor A (and to a lesser extent PKS 349-27) may arise from the way in which the radio jet energized the IS gas in the galaxy.
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The author(s) of this abstract have provided an email address for comments about the abstract: simkin@pa.msu.edu