Source code for casatasks.imaging.ft

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# stub function definition file for docstring parsing
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[docs]def ft(vis, field='', spw='', model='', nterms=1, reffreq='', complist='', incremental=False, usescratch=False): r""" Insert a source model as a visibility set [`Description`_] [`Examples`_] [`Development`_] [`Details`_] Parameters - vis_ (string) - Name of input visibility file - field_ (string='') - Select field using field id(s) or field name(s) - spw_ (string='') - Select spectral window/channels - model_ (variant='') - Name of input model image(s) - nterms_ (int=1) - Number of terms used to model the sky frequency dependence .. raw:: html <details><summary><i> nterms != 1 </i></summary> - reffreq_ (string='') - Reference frequency (e.g. \'1.5e+9\' or \'1.5GHz\') .. raw:: html </details> - complist_ (string='') - Name of component list - incremental_ (bool=False) - Add to the existing model visibility? - usescratch_ (bool=False) - If True, predicted visibility is stored in MODEL_DATA column .. _Description: Description **ft** converts a source model or a components list into model visibilities that is inserted into the MODEL_DATA column of the MS. Alternatively (*usescratch=False*) it can be stored in the header of the MS to be served on the fly when requested. The function of **ft** is needed to use more complicated sources, or to attach models to be subtracted later from the visibilities with **uvsub**. The source model should be in units of Jy/pixel, usually a \*.model image that **tclean** saves as a result of deconvolution. **ft** only uses a standard gridder (a prolate spheroidal) but supports multi-term images (see **tclean** help). Other gridders, like *mosaic* or *widefield*, are currently not supported. If you need one of the non-standard gridders, attach the model to the MS with the task **tclean, ** setting ** ** *savemodel=True,* and *gridder* to the requested algorithm. The default is to replace any current MODEL in the MS by the model specified in the *model* or *complist* parameters. The parameter *incremental=True* will add the specified model to the current MODEL in the MS. This can be useful, e.g., when new point sources are identified that need to be added to the model in the MS. When both, a *model* and a component list (in *complist)* are specified, **ft** will only use the model image in the *model* parameter. **ft** is strict in its frequency interpretation. Only frequencies that the model covers are inserted into the MS. If the model has a different frequency range, it needs to be modified to span the MS spws that are to be associated. Otherwise, the frequency ranges that are not covered by the model will be unaltered in the model column, or filled with zeros in the case that a MODEL_DATA column is added because none previously existed. In addition to **tclean**, another alternative to **ft** is **setjy**, which attaches a model and also scales the flux of the model to a flux value calculated from a standard or to a provided value. .. note:: **NOTE**: Model images for standard VLA calibrators 3C48, 3C138, 3C147, and 3C286 for the VLA bands are provided with the release. The location inside the package is dependent on the operating system; **setjy** *(listmodels=True)* will show all available models. .. _Examples: Examples **Example 1:** Add a multi-term model (image.model from clean) to an MS ('myMS.ms'), spectral window 3, writing directly to the MODEL column: :: ft(vis='myMS.ms', spw=3, nterms=2, model=['image.model.tt0','image.model.tt1'], usescratch=True) **Example 2:** Create a component list with a point source at position J2000 12h33m45.3s -23d01m11.2s with a spectral index of -0.8 and a flux of 13.4 Jy at a reference frequency of 1.25GHz; insert it into 'myMS.ms' as a virtual model for field 3: :: # first create the component list cl.addcomponent(shape='point', flux='13.4Jy', spectrum type='spectral index', index=-0.8, freq'1.25GHz', dir='J2000 12h33m45.3s -23d01m11.2s') # save the component list under the name 'mycomplist.cl' cl.rename('mycomplist.cl') cl.close() # now insert the component list into myMS.ms as a virtual MODEL ft(vis='myMS.ms', field='3', complist='mycomplist.cl', usescratch=True) .. _Development: Development No additional development details .. _Details: Parameter Details Detailed descriptions of each function parameter .. _vis: | ``vis (string)`` - Name of input visibility file | Default: none | Example: vis='ngc5921.ms' .. _field: | ``field (string='')`` - 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: | ``spw (string='')`` - Select spectral window/channels | Default: '' (all spectral windows and channels) .. _model: | ``model (variant='')`` - 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: | ``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: | ``reffreq (string='')`` - Reference-frequency about which this Taylor-expansion is | defined. | Default: '' (reads the reference frequency from | the model image) | Example: reffreq = '1.5GHz' .. _complist: | ``complist (string='')`` - Name of component list | Default: none | Example: complist='test.cl' | WARNING: component lists are difficult to make .. _incremental: | ``incremental (bool=False)`` - Add model visibility to the existing model visibilties | stored in the MS | Default: False | Options: False|True .. _usescratch: | ``usescratch (bool=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). """ pass