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.
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