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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; 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’. Note that the pol parameter is no longer supported; one should use the region parameter if polarization selection is desired, in conformance with other ia tool methods.

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 selection. See ”help par.region” for details. Default is to use the full image.

allowed:

any

Default:

variant

channels

Channels to use for continuum estimation. Default is all.

allowed:

intArray

Default:

-1

pol

THIS PARAMETER IS NO LONGER SUPPORTED. USE THE region PARAMETER TO CHOOSE WHICH POLARIZATIONS YOU WOULD LIKE TO PROCESS

allowed:

string

Default:

fitorder

Polynomial order for continuum estimation

allowed:

int

Default:

0

overwrite

Auto-overwrite output files if they exist?

allowed:

bool

Default:

false

Returns
image

Example

 
 
Fit a second order polynomial (fitorder=2) to channels 3-8 and 54-60 (python’s  
range function includes the lower limit and excludes the upper limit)  
to an RA x Dec x Frequency x Stokes cube.  
 
ia.open("myimage.im")  
 
# select stokes plane 1 on which to perform the fit, as well  
# as a box of pixels with blc=25,25 and trc=75,75 in the direction  
# plane, and channels 0 to 100. This will be the portion of the cube  
# from which the fit is subtracted  
reg = rb.box(blc=[25, 25, 0, 1], trc=[75, 75, 100, 1])  
csub = ia.continuumsub(region=reg, channels=range(3,9)+range(54,61), fitorder=2)  
 
# do stuff with original image (ia) and csub image tools as necessary and  
# finally close them  
ia.done()  
csub.done()  
 

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