Last modified: December 2018

URL: http://cxc.harvard.edu/sherpa/ahelp/shell2d.html
Jump to: · Example · ATTRIBUTES · Notes · Bugs · See Also


AHELP for CIAO 4.11 Sherpa v1

shell2d

Context: models

Synopsis

A homogenous spherical 3D shell projected onto 2D.

Syntax

shell2d

Example

>>> create_model_component("shell2d", "mdl")
>>> print(mdl)

Create a component of the shell2d model and display its default parameters. The output is:

mdl
   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.xpos     thawed            0 -3.40282e+38  3.40282e+38           
   mdl.ypos     thawed            0 -3.40282e+38  3.40282e+38           
   mdl.ampl     thawed            1 -3.40282e+38  3.40282e+38           
   mdl.r0       thawed            1            0  3.40282e+38           
   mdl.width    thawed          0.1            0  3.40282e+38           

ATTRIBUTES

The attributes for this object are:

xpos

The center of the shell on the x0 axis.

ypos

The center of the shell on the x1 axis.

ampl

The amplitude.

r0

The line-of-sight distance.

width

The width of the shell.

Notes

The functional form of the model for points is:

f(x0,x1) = ampl * r(x0,x1)

         = 0     otherwise

r(x0,x1) = ?

For grids, the x0lo,x1lo values are used in the above equation.

It is not correct for very large shells on the sky.

This model was provided by Christoph Deil.


Bugs

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

See Also

models
disk2d