The extended narrow line region in Mkn79. I.Observations

Abstract

We present deep long slit spectra of Mkn79 in position angles PA=12${}^o$ and PA=50${}^o$ obtained with the WHT. These data prove the existence of an extended narrow line region in PA=12${}^o$, which coincides with the triplet radio structure (Ulvestad \& Wilson 1984) and the observed outflow of material from the nucleus at PA=10${}^o$ (Whittle et al. 1988). The ratios of the high to low ionization lines indicate a higher level of gas excitation in PA=12${}^o$ compared to PA=50${}^o$. The [NII]$\lambda$6583/H$\alpha$ and [SII]$\lambda$6717,31/H$\alpha$ versus [OIII]$\lambda$5007/H$\beta$ line ratios are consistent with excitation by an AGN continuum rather than a HII region.

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