AHELP for CIAO 4.15 Sherpa
Gaussian function for modeling absorption (optical depth).
This model is intended to be used to modify another model (e.g. by multiplying the two together). It is for use when the independent axis is in Angstroms.
>>> create_model_component("opticalgaussian", "mdl") >>> print(mdl)
Create a component of the opticalgaussian model and display its default parameters. The output is:
mdl Param Type Value Min Max Units ----- ---- ----- --- --- ----- mdl.fwhm thawed 100 1.17549e-38 3.40282e+38 km/s mdl.pos frozen 5000 1.17549e-38 3.40282e+38 angstroms mdl.tau thawed 0.5 -3.40282e+38 3.40282e+38
The attributes for this object are:
|fwhm||The full-width half-maximum of the model in km/s.|
|pos||The center of the gaussian, in Angstroms.|
|tau||The optical depth of the model.|
|limit||The model is only evaluated for points that lie within limit sigma of pos. It is a hidden parameter, with a value fixed at 4.|
The functional form of the model for points is:
f(x) = exp(-tau * g(x)) g(x) = exp(-0.5 * ((x - pos) / sigma)^2) sigma = pos * fwhm / (2.9979e5 * 2.354820044)
and for integrated data sets the low-edge of the grid is used. The calculation is only done for those points that are in the range:
|x - pos| < limit * sigma
Outside this range the model is set to 1.
See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.