National Radio
Astronomy Observatory

6.13.2.2 Gaussian Multiplets

It is possible to fit a number of Gaussians together, as multiplets with restrictions. All restrictions are relative to a reference Gaussian (the zero’th component of each multiplet). gncomps specifies the number of Gaussians for each multiplets, and, in fact, a number of these multiplets can be fit simultaneously. gncomps=[2,4,3], e.g. fits a 2-component Gaussian, a 4-component Gaussian, and a 3-component Gaussian all at once. The initial parameter estimates can be specified with the gmampest, gmcenterest, and gmfwhmest parameters and the estimates are simply listed in the sequence of gncomps. E.g. if gncomps=[2,4,3] is specified with multiplet G0 consisting of 2 Gaussians a, b, multiplet G1 of 4 Gaussians c, d, e, f, and multiplet G2 of three Gaussians g, h, i, the parameter list in gm*est would be like gm*est=[a,b,c,d,e,f,g,h,i].

Restrictions can be specified via the gmampcon parameter for the amplitude ratio (non-reference to reference), gmcentercon for the offset in pixels (to a reference), and gmfwhmcon for the FWHM ratio (non-reference to reference). A value of 0 will not constrain anything. The reference is always the zero’th component in each multiplet, in our example, Gaussians a, c, and g. They cannot be constrained. So gmncomps=[2, 4, 3], gmampcon= [ 0 , 0.2, 0 , 0.1, 4.5, 0 ], gcentercon=[24.2, 45.6, 92.7, 0 , -22.8, -33.5], and gfwhmcon="" would constrain Gaussians b relative to a with a 24.2 pixel offset, Gaussian d to c with a amplitude ratio of 0.2 and a 45.6 pixel offset, Gaussian e to c with a offset of 92.7 pixels, etc. Restrictions will overrule any estimates.

The parameters goodamprange, goodcenterrange, and goodfwhmrange can be used to limit the range of amplitude, center, and fwhm solutions for all Gaussians.

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