1.1.1.0 image.continuumsub

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image.continuumsub - Function

1.1.1 Image plane continuum subtraction
Description

This function packages the relevant image tool functionality for simple specification and application of image plane continuum subtraction. All that is required of the input image is that it have a non-degenerate Spectral axis.

The user specifies region, the region of the input image over which continuum subtraction is desired (otherwise the whole image will be treated); channels, the subset of channels on the spectral axis to use in the continuum estimation, specified as a vector; pol, the desired single polarization to treat (otherwise all pols, if a polarization axis exists, will be treated); fitorder, the polynomial order to use in the estimation. Optionally, output line and continuum images may be written by specifying outline and outcont, respectively. If outline is not specified, a virtual image tool is all that is produced. If outcont is not specified, the output continuum image will be written in ’continuumsub.im’.

Arguments


Inputs
outline	Output line image filename. Default is unset.
	allowed:	string
	Default:
outcont	Output continuum image filename
	allowed:	string
	Default:	continuumsub.im
region	Region over which continuum subtraction is desired. Deafault is whole image.
	allowed:	any
	Default:	record
channels	Channels to use for continuum estimation. Default is all.
	allowed:	intArray
	Default:	-1
pol	Polarization to process. String from ”I Q U V XX RR” etc. Default is unset.
	allowed:	string
	Default:	I Q U V XX RR
fitorder	Polynomial order for continuum estimation
	allowed:	int
	Default:	0
overwrite	Auto-overwrite output files if they exist?
	allowed:	bool
	Default:	false

Returns
casaimage

Example

"""
#
print "\t----\t continuumsub Ex 1 \t----"
ia.fromarray(outfile=’test.data’,
             pixels=ia.makearray(0, [64, 64, 4, 128]), overwrite=true)
#im1csub=ia.continuumsub(region=rg.quarter(),
#                        channels=range(3,9)+range(54,61),fitorder=0);
innerquarter=ia.setboxregion([0.25,0.25],[0.75,0.75],frac=true)
im1csub=ia.continuumsub(region=innerquarter,
                        channels=range(3,9)+range(54,61),fitorder=0);
im1csub.done()      # done the on-the-fly image tool
ia.close()
#
"""

In this first example, the continuum emission in each pixel of the inner quarter of the input image is estimated by averaging (fitorder=0) channels 3-8 and 54-60, inclusive. (Python’s range function includes the lower limit and excludes the upper limit.) im1csub is an image tool containing the result (only the inner quarter of the original image).

"""
#
print "\t----\t continuumsub Ex 2 \t----"
ia.fromarray(outfile=’test.data’,
pixels=ia.makearray(0, [64, 64, 4, 128]), overwrite=true)
im2csub=ia.continuumsub(channels=range(3,9)+range(54,61),pol=’I’,fitorder=2)
im2csub.done()
ia.close()
#
"""

In this second example, the Stokes I continuum emission in each pixel of the whole input image is estimated with a 2nd-order polynomial fit to channels 3-8 and 54-60. The output image tool (im2csub) contains only Stokes I, even if the original image had other stokes planes.

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