Weekly Report 3Sep2010
Visibility Forward Fit - Elliptical Model
For the following tests an eventlist for a simulated point source at disk center was used. The visibility forward fit model used to create the image was an elliptical source. In both cases below the flux was help fixed. In the first case all parameters except for the flux were allowed top vary. In the second case all parameters except for the flux and the eccentricity of the ellipse were allowed to vary. The second case was carried out due to issues with the first case as will be discussed below.
In all cases the measured visibility amplitude is the set shown below. The red curve is the best fit to these visibilities using an elliptical model with all parameters free. In the cases were the flux is fixed the fit to the visibilities is constrained and cannot achieve this optimal fit.
Visibility Forward Fit - Elliptical Model(Flux fixed all other parameters free)
In this case the flux was fixed and the other parameters of the elliptical model were allowed to vary. At the point were the reduced chi2 reached it's lowest value it was recorded along with the total C statistic and the C statistic for each detector from the image object.
The plot below shows the value of the reduced chi2 as a function of the flux.
The reduced chi2 is a well behaved function of the flux. It has a single minimum at approximately 20ph/cm2/sec, around the same point as the the circular gaussian. Once again the reduced chi2 increases rapidly as the flux moves from the value that produces the minimum in the reduced chi2.
The plot below shows the total C statistic as a function of the flux.
The most noticeable feature of the plot are the points where the C statistic drops to approximately -12.
Visibility Forward Fit - Elliptical Model (Flux and Eccentricity fixed all other parameters free)
Difference Plots - Model v. Reconstructed Image
