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Version 1.9 Build 1488 |
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Package | general | |
Module | images | |
Tool | imagepol |
infile | in | Other image | |
Allowed: | String or Image tool | ||
debias | in | Debias the linearly polarized intensity ? | |
Allowed: | T or F | ||
Default: | F | ||
clip | in | Clip level for auto-sigma determination | |
Allowed: | Float | ||
Default: | 10 | ||
sigma | in | Standard deviation of thermal noise | |
Allowed: | Float | ||
Default: | Auto determined | ||
outfile | in | Output image file name | |
Allowed: | String | ||
Default: | Unset |
This function (short-hand name edr) returns the error in the linear depolarization ratio computed from two frequencies; this is the ratio of the fractional linear polarization at the two frequencies. Generally this is done when you have generated two images, each at a different frequency (continuum work). Thus if the fractional linear polarzation images are m1 and m2 then the depolarization ratio is m1/m2.
This function operates with two images; the first is that with which you constructed your Imagepol tool. The second is supplied via the argument infile, which can be an Image tool, or a String holding the name of the image file.
In generating the depolarization ratio, and hence its error, you may optionally debias the linearly polarized intensity. This requires the standard deviation of the thermal noise. You can either supply it if you know it, or it will be worked out for you with outliers from the mean clipped at the specified level.
You can get the depolarization ratio image with function depolratio.
- im1 := image('stokes.4800') - im2 := image('stokes.8300') - p := imagepol(im1) - dpr := p.depolratio(im2); - edpr := p.sigmadepolratio(im2);