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]$λ$6583/H$α$ and [SII]$λ$6717,31/H$α$ versus [OIII]$λ$5007/H$β$ line ratios are consistent with excitation by an AGN continuum rather than a HII region.