Fit a single component source model to the uv-data. Three models are available: P=point; G=Gaussian; D=Disk. Fitting parameters can be held fixed. The results are given in the CASA log and placed in a components file. More information can be found about uvmodelfit here.

INFO: The Nordic ALMA Regional Center Node has developed tools for fitting multiple components of any shape to the visibilities. Their versatile uvmultifit [1] package is provided on their software tools page.  

Parameter descriptions


Name of input visibility file. Default: none. Examples: vis=''


Select data based on field id(s) or name(s). Default: '' (all). Examples: field='1'; field='0~2', field IDs inclusive from 0 to 2; field='3C*', all field names starting with 3C


Select data based on spectral window. Default: '' (all). Examples: spw='1'; spw='<2' #spectral windows less than 2; spw='>1', spectral windows greater than 1


Select a subset of the visibility using MSSelection. Default: False.  Examples: selectdata=True


Select data based on time range. Default = '' (all). Examples: timerange = 'YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss'

NOTE: YYYY/MM/DD can be dropped as needed.

Further examples: timerange='09:14:0~09:54:0' yields the quoted time range; timerange='09:44:00' yields data within one integration of the specified time; timerange='>10:24:00' yields data after the specified time; timerange='09:44:00+00:13:00' yields data 13 minutes after the specified time


Select data within uvrange (default units kilo-lambda). Default: '' (all). Examples: uvrange='0~1000klambda', uvrange from 0-1000 kilo-lambda; uvrange='>4klambda', uvranges greater than 4 kilo lambda; uvrange='0~1000km', uvrange in kilometers


Select data based on antenna/baseline. Default: '' (all).  Examples: antenna='5&6', baseline 5-6; antenna='5&6;7&8', baselines 5-6 and 7-8; antenna='5', all baselines with antenna 5; antenna='5,6', all baselines with antennas 5 and 6


Select data based on scan number. Default: '' (all). Examples: scan='>3'


Optional data selection (field,spw,time,etc). Default:'' means select all.  Examples: msselect='FIELD_ID==0'; msselect='FIELD_ID IN [0,1,2]' means select fields 0,1 and 2; msselect='FIELD_ID <= 1' means select fields 0, 1; msselect='FIELD_ID==0 && ANTENNA1 IN [0] && ANTENNA2 IN [2:26]' means select field 0 and antennas 0 to 26, except antenna 1. Other msselect fields are: 'DATA_DESC_ID', 'SPECTRAL_WINDOW_ID', 'POLARIZATION_ID', 'SCAN_NUMBER', 'TIME', 'UVW'.


Number of fitting iterations to execute. Default: 5. Examples: niter=20


Component model type. Default: 'P'. Options: 'P' (point source), 'G' (elliptical gaussian), 'D' (elliptical disk)


Starting guess for component parameters. Default: [1,0,0] (for comptype='P').

If comptype = 'P', then sourcepar = [flux,xoff,yoff], where flux = flux (Jy), xoff = offset east (arcsec), yoff = offset north (arcsec).

If comptype = 'G' or 'D', then sourcepar = [flux,xoff,yoff,majax,axrat,pos], where majax = FWHM along the major axis (arcsec), axrat < 1 is the ratio of minor to major axis, pos = position angle (deg)


Control which parameters to let vary in the fit. Default: [ ] (all vary). Examples: varypar=[False,True,True]


Examples with comptype, sourcepar, and varypar

Fit a point: comptype = 'P', sourcepar = [0.4,0.2,-0.3], varypar = [True,True,True]

Fit a circular Gaussian: comptype = 'G', sourcepar = [1.4,0.3,-0.2,0.3, 1, 0], varypar = [ True , True ,  True , True , False, False]



Optional output component list table. Default: ''. Examples: outfile=''

How to get the output values:'')        #open the componentlist ''
fit = cl.getcomponent(0)           #stores component informationof the first component 
fit                                #to see the list
flux = fit['flux']['value']        #to store the I,Q,U,V, flux
print flux
ra = fit['shape']['direction']['m0']['value']
dec =fit['shape']['direction']['m1']['value']
print ra, dec
bmaj = fit['shape']['majoraxis']['value']     #to get major axis
bmin = fit['shape']['minoraxis']['value']     #to get minor axis 


Citation Number 1
Citation Text Marti-Vidal et al. 2014, A&A 563, 136 (arXiv:1401.4984)