ft – Insert a source model as a visibility set – imaging, calibration task

Description

A source model (souce.model image) or components list is converted into model visibilities that is inserted into the MODEL_DATA column or alternatively is stored in the header of the MS to be served on the fly when requested.

Setjy will automatically make this ft step on the sources currently available, which are 3C48, 3C138, 3C147, 3C286 at 1.4, 5.0, 8.4, 15, 22, 43 GHz. Their location is site dependent. In Charlottesville and Socorro, the models are in /usr/lib(lib64)/casapy/data/nrao/VLA/CalModels.

Parameters

Title

Parameter	Default	Description
vis	''	Name of input visibility file
field	''	Select field using field id(s) or field name(s)
spw	''	Select spectral window/channels
model	''	Name of input model image(s)
nterms	int(1)	Number of terms used to model the sky frequency dependence
reffreq	''	Reference frequency (e.g. '1.5e+9' or '1.5GHz')
complist	''	Name of component list
incremental	False	Add to the existing model visibility?
usescratch	False	If True, predicted visibility is stored in MODEL_DATA column

Parameter Explanations

vis

''

Name of input visibility file

Default: none

Example: vis=’ngc5921.ms’

field

''

Select field using field id(s) or field name(s)

Default: ‘’ (all fields)

BUT, only one source can be specified in a multi-source vis.

Examples: field = ‘1328+307’ specifies source ‘1328+307’ field = ‘4’ specified field with index 4

spw

''

Select spectral window/channels

Default: ‘’ (all spectral windows and channels)

model

''

Name of input model image(s)

Default: ‘’ (none)

Example: model=’/usr/lib/casapy/data/nrao/VLA/CalModels/3C286_X.im’

NOTE: The model visibilities are scaled from the model frequency to the observed frequency of the data.

nterms

int(1)

Number of terms used to model the sky frequency dependence

Default: 1 (one model image is required)

Example: nterms=3 - represents a 2nd order Taylor-polynomial in frequency and should be used in conjuction with coefficient model images as model=[‘xxx.model.tt0’,’xxx.model.tt1’, ‘xxx.model.tt2’]

reffreq

''

Reference-frequency about which this Taylor-expansion is defined.

Default: ‘’ (reads the reference frequency from the model image)

Example: reffreq = ‘1.5GHz’

complist

''

Name of component list

Default: none

Example: complist=’test.cl’

WARNING: component lists are difficult to make

incremental

False

Add model visibility to the existing model visibilties stored in the MS

Default: False Options: False|True

usescratch

False

Story visibilities in MODEL_DATA column?

Default: False Options: False|True

If True, model visibilities will be stored in the scratch column MODEL_DATA; if False, the model visibilities will be generated on the fly (this mode may save some disk space equivalent to the volume of the observed data).