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casa
$Rev:20696$
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casa
$Rev:20696$
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Functions | |
| def | pclean |
| def pclean.pclean | ( | vis = '', |
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imagename = '', |
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imsize = [256, |
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cell = ['1.0arcsec', |
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| arcsec, | |||
phasecenter = '', |
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stokes = 'I', |
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mask = '', |
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field = '', |
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spw = '', |
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ftmachine = 'ft', |
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alg = 'clark', |
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scales = [0], |
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cyclefactor = 1.5, |
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majorcycles = 1, |
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niter = 500, |
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gain = 0.1, |
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threshold = '0.0Jy', |
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weighting = 'natural', |
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robust = 0.0, |
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npixels = 0, |
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mode = 'continuum', |
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nterms = 1, |
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start = 0, |
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nchan = 1, |
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width = 1, |
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restfreq = '', |
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interactive = False, |
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npercycle = 100, |
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wprojplanes = 128, |
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facets = 1, |
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overwrite = True, |
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uvtaper = False, |
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outertaper = [''], |
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timerange = '', |
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uvrange = '', |
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antenna = '', |
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scan = '', |
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observation = '', |
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pbcor = False, |
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minpb = 0.2, |
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clusterdef = '' |
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| ) |
Invert and deconvolve images with parallel engines
Keyword arguments:
Invert and deconvolve images with parallel engines
Form images from visibilities. Handles continuum and spectral line
cubes using module pcont and pcube respectively.
vis -- Name of input visibility file
default: none; example: vis='ngc5921.ms'
imagename -- Pre-name of output CASA image. (only the prefix)
default: none;
example: imagename='m2', output images are:
m2.image; cleaned and restored image
With or without primary beam correction
m2.psf; point-spread function (dirty beam)
m2.model; image of clean components
m2.mask; image containing clean regions, when interative=True
imsize -- Image pixel size (x,y). DOES NOT HAVE TO BE A POWER OF 2
default: [256,256];
example: imsize=[350,350]
imsize=500 is equivalent to imsize=[500, 500]
Avoid odd-numbered imsize.
cell -- Cell size (x,y)
default: '1.0arcsec';
example: cell=['0.5arcsec', '0.5arcsec'] or
cell=['1arcmin', '1arcmin']
cell='1arcsec' is equivalent to cell=['1arcsec', '1arcsec']
NOTE:cell=2.0 => cell=['2arcsec', '2arcsec']
phasecenter -- direction measure or fieldid for the mosaic center
default: '' => first field selected;
example: phasecenter=6
or phasecenter='J2000 19h30m00 -40d00m00'
mask -- mask image to be used for CLEANing. As long as the image has
the same shape (size), mask images from a previous
interactive session can be used for a new execution.
Only an image mask is allowed at this stage. Text formats not allowed yet.
field -- Select fields in MS. Use field id(s) or field name(s).
['go listobs' to obtain the list id's or names]
default: ''= all fields
If field string is a non-negative integer, it is assumed to
be a field index otherwise, it is assumed to be a field name
examples:
field='0~2'; field ids 0,1,2
field='0,4,5~7'; field ids 0,4,5,6,7
field='3C286,3C295'; field named 3C286 and 3C295
field = '3,4C*'; field id 3, all names starting with 4C
spw --Select spectral window/channels
NOTE: This selects the data passed as the INPUT to mode
default: ''=all spectral windows and channels
examples:
spw='0~2,4'; spectral windows 0,1,2,4 (all channels)
spw='0:5~61'; spw 0, channels 5 to 61
spw='< 2'; spectral windows less than 2 (i.e. 0,1)
spw='0,10,3:3~45'; spw 0,10 all channels, spw 3,
channels 3 to 45.
spw='0~2:2~6'; spw 0,1,2 with channels 2 through 6 in each.
spw='0:0~10;15~60'; spectral window 0 with channels
0-10,15-60
spw='0:0~10,1:20~30,2:1;2;3'; spw 0, channels 0-10,
spw 1, channels 20-30, and spw 2, channels, 1,2 and 3
ftmachine -- Fourier Transform Engine (Gridding method)
Options:
'ft' (standard interferometric gridding),
'sd' (standard single dish),
'mosaic' (grid using PB as convolution function).
'wproject' (wprojection gridder to correct for widefield 'w' term errors)
default: 'ft'
alg -- Deconvolution algorithm
Options: 'clark', 'hogbom', 'multiscale'
default: 'clark'
cyclefactor -- Controls the threshhold at which the
deconvolution cycle will pause to degrid and subtract the
model from the visibilities (Cotton-Schwab (CS) major cycle).
With poor PSFs, reconcile often (cyclefactor=4 or 5) for
reliability.
With good PSFs, use cyclefactor = 1.5 to 2.0 for speed.
Note: threshold = cyclefactor * max sidelobe * max residual
default: 1.5; example: cyclefactor=4
cyclefactor=0 allows the user to control number of CS major cycle
>>> majorcycles -- integer number of CS major cycles to do
default: 1;
example: majorcycles=10
niter -- Maximum number iterations,
if niter=0, then no CLEANing is done ("invert" only)
default: 500;
example: niter=5000
threshold -- Flux level (residual peak) at which to stop CLEANing
default: '0.0mJy';
example:
threshold='2.3mJy' (always include units)
threshold='0.0023Jy'
threshold='0.0023Jy/beam' (okay also)
weighting -- Weighting to apply to visibilities:
Options: 'natural','uniform','briggs',
'superuniform','radial'
default: 'natural';
example: weighting='uniform';
scales -- list of scales in pixel for multiscale clean
default: [0]
example: scales=[0, 3, 10]
mode -- type of image to be generated
Options: 'continuum', 'cube'
default: 'continuum'
example:
mode='cube'; Use with nchan, start, step to specify
output image cube.
NOTE: mode='velocity' or 'channel' or 'frequency'
are aliased to mode='cube' for backward compatibility
and comfort.
>>> mode='cube' expandable parameters
nchan -- Total number of channels in the output image.
Example: nchan=100.
Default: -1; Automatically selects enough channels to cover
data selected by 'spw' and consistent with 'start' and 'step'
It is often easiest to leave nchan at the default value.
start -- First channel, velocity, or frequency.
if start is an integer pclean will assume it is the a channel index
if start is in units of velocity or frequency it will take it as such
If the user use the the ms channel as starting pclean will assign
the first channel of the image to the data channel frequency in LSRK
of the first
spw selected at the first time seen in the data and the direction of the
source selected.
If the data is not in the LSRK frame the user should be aware that the
data channel indicated may not fall on the first image channel as time goes.
example:start=5
start can be in units of frequency or velocity too
When velocity units is used it is obvious then that it is referring to the line
whose restfrequency is provided by the user or is default one for the source
in the MS/SOURCE table.
examples: start='5.0km/s', or start='22.3GHz'.
width -- Output channel width
should be in the same units as start
default=1; >1 indicates channel averaging
if start is an integer, width has to be an integer defining the image channel
width by the number of channels of first spectral window selected
example: width=4.
when start is in frequency or velocity units then the width has to be in the same units. default='';
examples: width='1.0km/s', or width='24.2kHz'.
interactive -- Create a mask interactively or not.
interactive clean allows the user to build the cleaning
mask interactively using the viewer.
default: False;
example: interactive=True
The viewer will open with the image displayed. Select the
region for the mask and double click in the middle of it.
>>> npercycle -- Number of iteration in between viewer interactions.
default=100
pbcor -- Output primary beam-corrected image
If pbcor=False, the final output image is NOT corrected for
the PB pattern (particularly important for mosaics), and
therefore is not "flux correct". Correction can also be
done after the fact using immath to divide
<imagename>.image by the <imagename>.flux image.
default: pbcor=False; output un-corrected image
example: pbcor=True; output pb-corrected image (masked outside
minpb)
>>> minpb -- Minimum PB level to use for pb-correction and pb-based masking.
default=0.2;
example: minpb=0.01
When ftmachine is *not* 'mosaic' :
minpb is applied to the flux image (sensitivity-weighted pb).
When ftmachine='mosaic' :
minpb is applied to the flux.pbcoverage image
overwrite -- If False use existing model image of same name to continue clean
if True the imagename.model and other associated images are overwitten
if they exist
default: True
timerange -- Select data based on time range:
default: '' (all); examples,
timerange = 'YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss'
Note: if YYYY/MM/DD is missing date defaults to first
day in data set
timerange='09:14:0~09:54:0' picks 40 min on first day
timerange='25:00:00~27:30:00' picks 1 hr to 3 hr
30min on NEXT day
timerange='09:44:00' pick data within one integration
of time
timerange='>10:24:00' data after this time
For multiple MS input, a list of timerange strings can be
used:
uvrange -- Select data within uvrange (default units meters)
default: '' (all); example:
uvrange='0~1000klambda'; uvrange from 0-1000 kilo-lambda
uvrange='>4klambda';uvranges greater than 4 kilo lambda
antenna -- Select data based on antenna/baseline
default: '' (all)
If antenna string is a non-negative integer, it is
assumed to be an antenna index, otherwise, it is
considered an antenna name.
antenna='5&6'; baseline between antenna index 5 and
index 6.
antenna='VA05&VA06'; baseline between VLA antenna 5
and 6.
antenna='5&6;7&8'; baselines 5-6 and 7-8
antenna='5'; all baselines with antenna index 5
antenna='05'; all baselines with antenna number 05
(VLA old name)
antenna='5,6,9'; all baselines with antennas 5,6,9
index number
scan -- Scan number range.
default: '' (all)
example: scan='1~5
observation -- Observation ID range.
default: '' (all)
example: observation='1~5'
clusterdef -- Name of a file that contains the cluster definition.
NOTE: there is a chapter in the cookbook on how to
define this file
If clusterdef='' (the default) then all the cores, if possible,
of the machine on
which casapy is run will be used.
Example of a cube imaging run:
pclean(vis="ngc5921.ms.contsub",imagename="loulou",imsize=[2500, 2500],
cell=['15.0arcsec', '15.0arcsec'],phasecenter="",stokes="I",field="0",spw="*",
ftmachine="ft",alg="hogbom",majorcycles=2, niter=6000,gain=0.1,
threshold="8mJy",weighting="briggs",robust=0.5,npixels=0,mode="cube",
start=5,nchan=46,width=1,interactive=True,overwrite=True,uvtaper=False,
outertaper=[''],pbcor=True)
Example of a continuum run:
pclean(vis='sim100g_4chan15kRows.ms',
imagename='hundredG_cont', imsize=[1500, 1500],
cell=['0.135arcsec', '0.135arcsec'], mode='continuum', phasecenter='0',
field='0', spw='*', ftmachine='wproject', wprojplanes=128,
threshold='0.1mJy',
majorcycles=4, niter=10000, alg='clark',
weighting='natural',
overwrite=True)Definition at line 13 of file pclean.py.
References task_pclean.pclean(), publish_summary.quantity, and vla_uvfits_line_sf.verify.
1.8.0