Getting Started Documentation Glish Learn More Programming Contact Us
Version 1.9 Build 1488
News FAQ
Search Home


next up previous contents index
Next: image.fitallprofiles - Function Up: image - Tool Previous: image.fft - Function


image.findsources - Function



Package general
Module images
Tool image


Find point sources in the sky


Synopsis
findsources(nmax, cutoff, region, mask, point, width, negfind)


Arguments

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


Returns
Componentlist tool or fail



Description

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.



Example
- 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.





next up previous contents index
Next: image.fitallprofiles - Function Up: image - Tool Previous: image.fft - Function   Contents   Index
Please send questions or comments about AIPS++ to aips2-request@nrao.edu.
Copyright © 1995-2000 Associated Universities Inc., Washington, D.C.

Return to AIPS++ Home Page
2006-08-01