impbcor – Construct a primary beam corrected image from an image and a primary beam pattern. – analysis task

Description

Correct an image for primary beam attenuation using an image of the primary beam pattern. The primary beam pattern can be provided as an image, in which case 1. it must have the same shape as the input image and its coordinate system must be the same, or 2. it must be a 2-D image in which case its coordinate system must consist of a (2-D) direction coordinate which is the same as the direction coordinate in the input image and its direction plane must be the same shape as that of the input image. Alternatively, pbimage can be an array of pixel values in which case the same dimensionality and shape constraints apply.

One can choose between dividing the image by the primary beam pattern (mode=”divide”) or multiplying the image by the primary beam pattern (mode=”multiply”). One can also choose to specify a cutoff limit for the primary beam pattern. For mode=”divide”, for all pixels below this cutoff in the primary beam pattern, the output image will be masked. In the case of mode=”multiply”, all pixels in the output will be masked corresponding to pixels with values greater than the cutoff in the primary beam pattern. A negative value for cutoff means that no cutoff will be applied, which is the default.

Parameters

Title
Parameter	Default	Description
imagename	`''`	Name of the input image
pbimage	`[ ]`	Name of the primary beam image which must exist or array of values for the pb response.
outfile	`''`	Output image name. If empty, no image is written.
overwrite	`False`	Overwrite the output if it exists?
box	`''`	Rectangular region to select in direction plane. Default is to use the entire direction plane.
region	`''`	Region selection.
chans	`''`	Channels to use.
stokes	`''`	Stokes planes to use.
mask	`''`	Mask to use.
mode	`'divide'`	Divide or multiply the image by the primary beam image. Minimal match supported.
cutoff	`float(-1.0)`	PB cutoff. If mode is “d”, all values less than this will be masked. If “m”, all values greater will be masked. Less than 0, no cutoff.
stretch	`False`	Stretch the mask if necessary and possible?

Parameter Explanations

imagename

''

Name of the input (CASA, FITS, MIRIAD) image

pbimage

[ ]

Name of the image (CASA, FITS, MIRIAD) of the primary beam pattern or an array of pixel values.

Default: ‘’

outfile

''

Name of output CASA image.: Default: none. Must be specified.

overwrite

False

If output file is specified, controls if an already existing file by the same name can be overwritten.

Default: True Options: True|False

If true, the user is not prompted, the file if it exists is automatically overwritten.

box

''

Rectangular region to select in direction plane.: Default: ‘’ (use the entire direction plane)

region

''

Region selection.: Default: ‘’ (use the full image)

chans

''

Channels to use.: Default: ‘’ (use all channels)

stokes

''

Stokes planes to use.: Default: ‘’ (use all Stokes planes)

mask

''

Mask to use.: Default: none

mode

'divide'

Divide or multiply the image by the primary beam image.

Default: ‘divide’

Minimal match supported.

cutoff

float(-1.0)

Primary beam cutoff.

Default: -1.0 (no cutoff)

If mode is “d”, all values less than this will be masked. If “m”, all values greater will be masked. Less than 0, no cutoff (default)

stretch

False

Stretch the mask if necessary and possible?: Default: False Options: False|True