feather – Combine two images using their Fourier transforms – imaging task

Description

This task can be used as one method of combining single-dish and interferometric images after they have been separately made.

The algorithm converts each image to the gridded visibility plane, combines them, and reconverts them into an combined image. Each image must include a well-defined beam shape (clean beam) in order for feathering to work well. The two images must have the same flux density normalization scale.

Parameters

Title

Parameter	Default	Description
imagename	''	Name of output feathered image
highres	''	Name of high resolution (interferometer) image
lowres	''	Name of low resolution (single dish) image
sdfactor	float(1.0)	Scale factor to apply to Single Dish image
effdishdiam	float(-1.0)	New effective SingleDish diameter to use in m
lowpassfiltersd	False	Filter out the high spatial frequencies of the SD image

Parameter Explanations

imagename

''

Name of output feathered image

Default: none

Example: imagename=’orion_combined.im’

highres

''

Name of high resolution (interferometer) image

Default: none

Example: imagename=’orion_vla.im’

lowres

''

Name of low resolution (single dish) image

Default: none

Example: imagename=’orion_gbt.im’

sdfactor

float(1.0)

Value by which to scale the Single Dish image.

Default: 1.0

Basically modifying the flux scale of the SD image

effdishdiam

float(-1.0)

New effective SingleDish diameter to use in m

Default: -1.0 (leave as is)

Obviously one can only reduce the dish effective dish diameter in feathering.

lowpassfiltersd

False

Filter out the high spatial frequencies of the SD image

Default: False

If True the high spatial frequency in the SD image is rejected.

Any data outside the maximum uv distance that the SD has illuminated is filtered out.