Line-ratio diagram of log ([Fe   ii] /Paβ) over log (H₂/Brγ). The flux values are taken from a 05 radius aperture centered on the main emission-line region to the south west of the continuum emission (see Table 1). The line flux of [Fe ii] λ1.257   μm was calculated from the line ratio [Fe ii]λ1.644/[Fe ii]λ1.257   μm = 0.74 (Nussbaumer & Storey 1988). Paβ was evaluated by assuming the case B line ratio Paα/Paβ = 2.05. Symbols represent literature data: rhombus symbols are from Dale et al. (2004) and representing starburst galaxies, circles represent LINERs and asterisks supernovae from Larkin et al. (1998), left hand triangles represent Seyfert 1 galaxies taken from Rodríguez-Ardila et al. (2004), and horizontally pointing triangles represent Seyfert 2s from Rodríguez-Ardila et al. (2005). The diagram shows the transition from pure photoionization (lower left corner) to pure shock ionization (upper right corner) (Rodríguez-Ardila et al. 2005). The dotted line represents a linear fit to the literature data where the 1-σ prediction band of the fit is shown in dashed lines (Zuther et al. 2007). The fit assumption is a linear relationship between the two line ratios.