Two tasks provide a simple IRAF-style command-line interface for calculating
nebular diagnostics for a single ion. The temden task calculates
N
given T
, or T
given N
, for one of several ions. (See example 1 in
Figure 2 .) Note that a simple algebraic expression can be used
to specify the ratio of the relevant diagnostic lines. The ionic task
computes and displays the line emissivities for all transitions between each
of the five lowest levels. Optionally, this task will display the level
populations and critical densities (see Eq. 4 and Eq. 5 )for these levels.
If the wavelength and flux (on the scale H
) of one of these
lines is also provided, ionic will also compute the H
emissivity (see
Eq. 6 ) and ionic abundance (see Eq. 7 ).
Note that the ionic abundance can be computed from the sum of two or more
line intensities if the wavelength tolerance (i.e., the wv_toler
parameter) is set large enough.