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Version 1.9 Build 1488 |
|
Package | general | |
Module | images | |
Tool | image |
nmax | in | Maximum number of sources to find | |
Allowed: | Positive Integer | ||
Default: | 20 | ||
cutoff | in | Fractional cutoff level | |
Allowed: | Float | ||
Default: | 0.1 | ||
region | in | The 2-D region of interest to fit | |
Allowed: | Region tool | ||
Default: | Whole image | ||
mask | in | OTF mask | |
Allowed: | Boolean LEL expression or mask region | ||
Default: | None | ||
point | in | Find only point sources ? | |
Allowed: | T or F | ||
Default: | T | ||
width | in | Half-width of fit grid when point=F | |
Allowed: | Integer | ||
Default: | 5 | ||
negfind | in | Find negative sources as well as positive ? | |
Allowed: | T or F | ||
Default: | F |
This function (short-hand name fs) finds strong point sources in the image. The sources are returned as a Componentlist tool.
An efficient method is used to locate sources under the assumption that they are point-like and not too close to the noise. Only sources with a peak greater than the cutoff fraction of the strongest source will be found. Only positive sources will be found, unless the negfind=T whereupon positive and negative sources will be found.
After the list of point sources has been made, you may choose to make a Gaussian fit for each one (point=F) so that shape information can be recovered as well. You can specify the half-width of the fitting grid with argument width which defaults to 5 (fitting grid would then be [11,11] pixels). If you set width=0, this is a signal that you would still like Gaussian components returned, but a default width should be used for the Gaussian shapes. The default is such that the component is circular with a FWHM of width pixels.
Thus, if point=T, the components in the returned Componentlist are Point components. If point=F then Gaussian components are returned.
The region-of-interest must be 2-dimensional and it must hold a region of the sky. Any degenerate trailing dimensions in the region are discarded.
See also the function fitsky (for which findsources can provide an initial estimate) and the Imagefitter tool.
- myim := imagemaketestimage() - cl := myim.findsources(nmax=5, cutoff=0.5) - cl.edit(1)
All sources stronger than 0.5 of the strongest will be found. We use the Componentlist GUI to look at the strongest component.