SELECT3

Select3 decides if a particular transition matches the selection criteria based on the line strength and line opacity in a given medium. To do that select3 requires a model of the medium (temperature, pressure, node spacing), chemical composition and boundary conditions. Only 1D models are supported at the moment.

Select3 processes one transition at a time working in two modes: opacity and synthesis. In the first mode it computes line opacity, compares it to the reference (e.g. bf and ff opacities Of the medium at the central wavelength of the line).

In second mode, the line depth relative To the continuum level is used for decision. Select3 works as a pipeline filter: it reads line information from standard input and if selected sends to standard output complementing it with the estimated line depth (synthesis mode). Before processing transitions select3 performs initialization consisting of reading the execution parameters, chemical composition and the model of the medium. After this select3 solves the equation of state (molecular and ionization equilibrium) of each model point getting partial number densities of all absorbers present in VALD3.