opticalgaussian

Context: models

Synopsis

Gaussian function for modeling absorption (optical depth).

Syntax

opticalgaussian

Description

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.

Example

>>> 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

ATTRIBUTES

The attributes for this object are:

Attribute	Definition
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.

Notes

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.

Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.