Weekly Report 1Apr2011

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RHESSI Albedo Imaging Test

The test below was done with the follwing conditions:

Results

The image below shows the Clean image for a single compact circular Gaussian source. The contours for the original map are overlaid in blue.

Clean image of a single compact circular Gaussian source with contours for the original map.

The Clean image is larger than the 1% contour of the original map. This is due to the noise added by the coarser grids for a source that can be accurately imaged using just detectors 1 to 3.


The images below show the Back Projection for each detector in the case of the compact Circular Gaussian Source.

The Back Projection image for each detector for a single compact circular Gaussian source.

In the finer grids the side lobes due to back projection are present. In the coarser grids. The source gets smeared out until it approaches the size of the Field of View. A discussion of the location of the pixel with the maximum flux follows below the final plot.

The image below shows the Clean image for a compact circular Gaussian source overlaid with a concentric circular extended Gaussian Source. The original map is overlaid in blue contours.

Clean image of a compact circular Gaussian source overlaid with a concentric extended circular Gaussian source. The contours of the original map are overlaid over the image.

Clean creates an image that has a larger FWHM than the compact source alone so it is accounting for additional flux from the extended source, however the 1% contour of the original map on the same color scale as the image for the compact source alone is larger than the image. As the extended source becomes weaker the counts drop off more quickly.

The images below are the Back Projection images for each detector for a map containing a compact source overlaid with an extended source.

The Back Projection image for each detector for a compact circular Gaussian source overlaid with a concentric extended circular Gaussian source.

Once again we observe the same patterns as seen with just a compact source. The finer grids image a compact source with side lobes, while the coarser grids show a smeared out source. It is difficult to observe any difference between these and the images for just a compact source. The results for the maximum pixel location are similar as shown in the final plot.

The Clean image below is for a compact circular Gaussian source and an extended circular Gaussian source offset toward the disk center by 6 arcsec. The contours overlaid are the original map.

Clean image of a compact circular Gaussian source with an offset extended circular Gaussian source. The contours of the original map are overlaid.

The Clean image shows the circular source bleeding into the extended source towards the disk center. The images show the characteristics of the original map, with a small source with concentrated flux and a larger more diffuse source separated from it.

The Back Projection images for each detector are shown below.

The Back Projection image for each detector for a compact Gaussian source with an offset extended Gaussian source.

In this test the differences between the single source and the concentric sources can be seen in detectors 2,3, and 4, clearly. The compact source at the center of the image is no longer circular and the side lobes are not circles. The locations of the maximum pixels are discussed below.

The plot below shows the Heliocentric X location of the maximum pixel for each Back Projection image for a single detector in all three map configurations.

The plot above shows the location of the pixel with the maximum flux in the Heliocentric X direction for each detector, for each of the three map configurations above.

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