Photoionization Grid Examples
Shown here are three examples of Mappings III photoionization models used to interpret data on diagnostic diagrams. The diagnostic diagrams are based on emission-line flux ratios and may serve many purposes. The grids shown below are used for; (1) classification of starburst galaxies and AGN (Kewley et al. 2001, ApJ, 556, 121), (2) abundance diagnostics for HII regions or star-forming galaxies (Kewley et al. 2002, ApJS, in press) and (3) ionization parameter diagnostics for HII regions or star-forming galaxies
Figure 1 : Photoionization grid of ionization parameter q (cm/s) and metallicity Z (solar units) for the Veilleux & Osterbrock (1987) diagnostic diagram. Galaxies which lie above and to the right of the photoionization grid have flux ratios which can not be reproduced by photoionization alone. Such galaxies require mixing with either a power-law radiation field from an AGN or shock excitation. See Kewley et al. (2001, ApJ, 556, 121) for more details.
Figure 2 : Abundance Diagnostic Grid for the standard abundance-sensitive line ratio R23. This diagram shows the ionization parameter dependence of the R23 diagnostic. R23 is double-valued for most R23 flux ratios. See Kewley et al. (2002, ApJS, in press) for more details.
Figure 3 : Ionization parameter diagnostic grid using the standard ionization-sensitive line ratio [OIII]/[OII]. This diagnostic is very sensitive to abundance. See Kewley et al. (2002, ApJS, in press) for more details.