Forbidden Fe+ emission from active galaxies

We present intermediate-resolution (similar to 400 km s(-1)) near-infrared spectra for eight Seyfert and three starburst galaxies, covering the [Fe II] 1.257-mu m and Pa beta lines. We combine these data with those in the literature to investigate the origin of the forbidden Fe+ emission in active galaxies, which is still under debate. In a study of 26 active galaxies, Forbes & Ward provided evidence that [Fell] emission in starburst galaxies is shock-excited by supernova remnants. Interestingly, the Seyfert galaxies in their sample also appeared to have shock-excited [Fe II] emission, although the radio jets were believed to be responsible. Analysis of our sample of 46 objects provides some support for the finding by Forbes & Ward that [Fe II] is more tightly correlated with radio power than the hydrogen recombination emission. However, we argue that the observed line ratios are inconsistent with the substantial grain destruction that is an inevitable consequence of shocks. Together with the fact that the dispersion in the [Fe II]-radio correlation is still fairly large, we deduce that photoionization of material with normal ISM abundances must be the dominant excitation mechanism, although we suggest that a significant contribution (similar to 20 per cent) of the [Fe II] emission may be shock-excited.