The core functionality of the original FIVEL program published by DDH was to
access the appropriate atomic data, to employ an iterative technique
(geometric bisection) to solve for T
given N (or vice versa), and to
calculate the level populations and line emissivities given T and N ;
all for a single ion. We revised the FIVEL subroutines to isolate the data
I/O and error handling, so that any number of applications can be layered
upon them. The tasks that we built for nebular are summarized in
Table 5 . The following subsections summarize the capabilities
of these tasks, including illustrative examples. Since this package, like
most software, can be expected to evolve, detailed descriptions of the task
interfaces and the various task parameters are left to the extensive on-line
documentation.
