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NRAO Home > CASA > CASA Task Reference Manual |
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0.1.136 uvmodelfit
Requires:
Synopsis
Fit a single component source model to the uv data
Description
Fit a single component source model to the uv data
Arguments
Inputs |
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vis |
| Name of input visibility file
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| allowed: | string |
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| Default: |
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field |
| Select field using field id(s) or field name(s)
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| allowed: | string |
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| Default: |
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spw |
| Select spectral window/channels
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| allowed: | string |
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| Default: |
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selectdata |
| Other data selection parameters
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| allowed: | bool | |
| Default: | True |
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timerange |
| Select data based on time range
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| allowed: | string |
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| Default: |
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uvrange |
| Select data within uvrange (default units meters)
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| allowed: | any |
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| Default: | variant
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antenna |
| Select data based on antenna/baseline
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| allowed: | string |
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| Default: |
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scan |
| Scan number range
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| allowed: | string |
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| Default: |
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msselect |
| Optional complex data selection (ignore for now)
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| allowed: | string |
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| Default: |
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niter |
| Number of fitting iterations to execute
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| allowed: | int |
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| Default: | 5 |
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comptype |
| component model type: P(oint), G(aussian), or D(isk)
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| allowed: | string |
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| Default: | P |
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sourcepar |
| Starting guess for component parameters (3 values for
type P, 5 for G and D)
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| allowed: | doubleArray |
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| Default: | 1.0 0.0 0.0
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varypar |
| Control which parameters to let vary in the fit
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| allowed: | boolArray |
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| Default: |
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outfile |
| Optional output component list table
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| allowed: | string |
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| Default: |
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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 log and placed in a
components file.
Keyword arguments:
vis -- Name of input visibility file
default: none; example: vis=’ngc5921.ms’
--- Data Selection
field -- Select data based on field id(s) or name(s)
default: ’’ (all); example: field=’1’
field=’0~2’ # field ids inclusive from 0 to 2
field=’3C*’ # all field names starting with 3C
spw -- Select data based on spectral window
default: ’’ (all); example: spw=’1’
spw=’<2’ #spectral windows less than 2
spw=’>1’ #spectral windows greater than 1
selectdata -- Select a subset of the visibility using MSSelection
default: False; example: selectdata=True
timerange -- Select data based on time range:
default = ’’ (all); example,
timerange = ’YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss’
Note: YYYY/MM/DD can be dropped as needed:
timerange=’09:14:0~09:54:0’ # this time range
timerange=’09:44:00’ # data within one integration of time
timerange=’>10:24:00’ # data after this time
timerange=’09:44:00+00:13:00’ #data 13 minutes after time
uvrange -- Select data within uvrange (default units kilo-lambda)
default: ’’ (all); example:
uvrange=’0~1000klambda’; uvrange from 0-1000 kilo-lamgda
uvrange=’>4klambda’;uvranges greater than 4 kilo lambda
uvrange=’0~1000km’; uvrange in kilometers
antenna -- Select data based on antenna/baseline
default: ’’ (all); example: antenna=’5&6’ baseline 5-6
antenna=’5&6;7&8’ #baseline 5-6 and 7-8
antenna=’5’ # all baselines with antenna 5
antenna=’5,6’ # all baselines with antennas 5 and 6
scan -- Select data based on scan number - New, under developement
default: ’’ (all); example: scan=’>3’
msselect -- Optional data selection (field,spw,time,etc)
default:’’ means select all; example: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’
See ccokbook for more details
niter -- Number of fitting iterations to execute
default: 5; example: niter=20
comptype -- component model type
default: ’P’;
Options: ’P’ (point source), ’G’ (elliptical gaussian),
’D’ (elliptical disk)
sourcepar -- Starting guess for component parameters
default: [1,0,0]; (for comptype=’P’)
IF comptype = ’P’ then
sourcepar = [flux,xoff,yoff] where
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=angle in deg
varypar -- Control which parameters to let vary in the fit
default: [] (all vary);
example: vary=[F,T,T]
examples:
fit a point:
comptype = ’P’
sourcepar = [0.4,0.2,-0.3];
varypar = [T,T,T]
fit a circular Gaussian:
comptype = ’G’
sourcepar = [1.4,0.3,-0.2,0.3, 1, 0]
varypar = [ T , T , T , T , F, F]
outfile -- Optional output component list table
default: ’’; example: outfile=’componentlist.cl’
How to get the output values:
cl.open(’componentlist.cl’)
fit = cl.getcompoent() stores component information
fit to see the whole mess
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
More information about CASA may be found at the
CASA web page
Copyright © 2016 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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