The upper (yellow & white) panel is the plot panel. It starts with the plots of the selected model Total Flux and your data. If you have input Flux per Beam data, then the model interpolated in frequency and beam size to match your data is also plotted. If you add new data (or change old data) in the Data Input Window, the ChiSquared Fit Window will automatically update itself.
Fitting of Total Flux is very fast. Fitting of Flux per Beam takes a little bit longer since the models must be interpolated in both frequency and beam size (essentially interpolating the Flux(freq,beam) plot in the Details Window) to match the frequencies and beam sizes of your data.
As with the Details Window, you can zoom in on any portion of the plot area. To zoom in, press and hold any mouse button and drag the mouse downwards to draw a box. To zoom out, drag the mouse upward to make a box in a similar fashion. Clicking on the 'AutoScale' button rescales the plot so that all the data fits, i.e., it zooms out all the way.
The lower (blue & white) panel is the TalkBack window. The fit results are displayed there, along with the calculated mass (M_{sun}) of the bestfit model. The mass is given as
M = { 4/(3p)} _{ i } r_{i}^{p} {r_{o}^{3p}  r_{i}^{3p} } 
where p is the power law exponent for the density structure of the envelope, r_{o} and r_{i} are the envelope outer and inner radii, respectively, and _{ i } is the density at the inner radius.
Most of the Menus on the ChiSquared Window are selfexplanatory. The Show Menu is especially important and is used to decide what traces should be on the plot. The choices (Data, Selected Model, Best Fit, Chisq vs. Model #) are all toggles. The default is Data and Selected Model toggled on and the others off. Changing a toggle will cause the plot to update. If Chisq vs. Model # is on, a small popup window containing all the chisquared values will appear after a fit is done. The Yaxis is initially scaled to show a moderate range centered around the median chisquared value. The plot is zoomable in the usual way. To popdown this plot, simply deselect Chisq vs. Model #.
The ChiSquared Show Menu, which gives you the choice of what traces to show. 
The ChiSquared vs. Model # popup window. 

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