Deconvolve an image with selected algorithm Form images from visibilities. Handles continuum and spectral line cubes. name of input visibility file Pre-name of output images Type of selection (mfs, channel, velocity, frequency) mfs channel velocity frequency Algorithm to use (clark, hogbom, csclean, multiscale) clark clark hogbom csclean multiscale Maximum number of iterations 500 Loop gain for cleaning 0.1 Flux level (+units) to stop cleaning 0.0 Name of mask image used in cleaning clean box regions or file name or \'interactive\' Number of channels (planes) in output image 1 First channel in input to use 0 Number of input channels to average 1 x and y image size in pixels, symmetric for single value 256256 x and y cell size. default unit radians 1.01.0 Stokes params to image (eg I,IV, QU,IQUV) I I IV QU IQUV RR LL RRLL XX YY XXYY Field Name Spectral windows:channels: \'\' is all Weighting to apply to visibilities natural natural uniform briggs radial superuniform Robustness mode (see help clean) norm none norm abs Briggs robustness parameter 0.0 -2.0 2.0 Apply additional filtering/uv tapering of the visibilities. False Major axis of filter (arcseconds) 1.0 Minor axis of filter (arcseconds) 1.0 Position angle of filter (arcseconds) 0.0 Range of time to select from data rest frequency to assign to image (see help) noise parameter for briggs weighting when rmode=\'abs\' 0.0 number of pixels for superuniform or briggs weighting 0 resolutions in pixel units 0310 Number of iterations before interactive prompt 100 Image phase center: position or field index 1 0 first input channel to use 1 1 0.0km/s Velocity of first image channel: e.g \'0.0km/s\' 1km/s image channel width in velocity units: e.g \'-1.0km/s\' 1 1.4GHz Frequency of first image channel: e.q. \'1.4GHz\' 10kHz Image channel width in frequency units: e.g \'1.0kHz\' 0 310 norm 0.0 0.0Jy 0 number of pixels to determine uv-cell size 0=> field of view 0 number of pixels to determine uv-cell size 0=> +/-3pixels 1.0 1.0 0.0 100 Three types of point-source deconvolution, as well as multi-scale deconvolution, are available. A continuum image (mfs) is produced by gridding together all spectral data. Individual channels or groups of channels can also be images and then placed in an output image cube. The cleaning regions can be specified by an input mask image, from a file containing rectangular regions, or interactively as the deconvolution progresses. The clean task only uses the "corrected" datacolumn which is made from the "data" data column using applycal with the appropriate calibration tables. Many Stokes combinations are available. Keyword arguments: vis -- Name of input visibility file: default: none; example: vis='n5921.ms' imagename -- Pre-name of output images: default: none; example: imagename='m2' output images are: m2.image; cleaned and restored image, NOT corrected for pb m2.model; image of clean components m2.residual; image of residuals m2.interactive.mask; image containing interactive mask or m2.cleanbox.mask; image containing cleanbox mask mode -- Frequency Specification: NOTE: See examples below: default: 'mfs' mode = 'mfs' means produce one image from all specified data. mode = 'channel'; Use with nchan, start, width to specify output image cube. See examples below mode = 'velocity', means channels are specified in velocity. mode = 'frequency', means channels are specified in frequency. >>> mode expandable parameters (for modes other than 'mfs') Start, width are given in units of channels, frequency or velocity as indicated by mode. nchan -- Number of channels (planes) in output image default: 1; example: nchan=3 start -- Start input channel (relative-0) default=0; example: start=5 width -- Output channel width (>1 indicates channel averaging) default=1; example: width=4 examples: spw = '0,1'; mode = 'mfs' will produce one image made from all channels in spw 0 and 1 spw='0:5~28^2'; mode = 'mfs' will produce one image made with channels (5,7,9,...,25,27) spw = '0'; mode = 'channel': nchan=3; start=5; width=4 will produce an image with 3 output planes plane 1 contains data from channels (5+6+7+8) plane 2 contains data from channels (9+10+11+12) plane 3 contains data from channels (13+14+15+16) spw = '0:0~63^3'; mode=chann; nchan=21; start = 0; width = 1 will produce an image with 20 output planes Plane 1 contains data from channel 0 Plane 2 contains date from channel 2 Plane 21 contains data from channel 61 spw = '0:0~40^2'; mode = 'channel'; nchan = 3; start = 5; width = 4 will produce an image with three output planes plane 1 contains channels (5,7) plane 2 contains channels (13,15) plane 3 contains channels (21,23) alg -- Algorithm to use (expandable): default: 'clark': Options: 'clark','hogbom','csclean','multiscale' 'hogbom' Image based clean. Does not go back to uv data Only inner quarter of image is cleaned 'clark' Cleans using gridded uv data. Only inner quarter of image is cleaned 'csclean' is Cotton-Schwab and can clean most of image area. 'multiscale' cleans with several resolutions using hobgom clean. Currently much slower than single resolution clean and not recommended. For extended sources, try single resolution clean with tight interactive mask and clean very deeply. >>> Multiscale expandable parameter scales -- in pixel numbers; the size of components to deconvolve default = [0,3,10] recommended sizes are 0 (point), 3 (points per clean beam), and 10 (about a factor of three lower resolution) niter -- Maximum number of clean components: default: 500; example: niter=2500 niter = 0 provides dirty image Note: You can restart a clean by simply using the same inputs. The clean will continue for niter more iterations. All files are overwritten. gain -- Loop gain for cleaning: default: 0.1; example: gain=0.5 threshold -- Level (default in Jy) to stop cleaning: default: 0.0; example: threshold='0.02mJy'. Cleaning will end when the largest residual point in the mask region becomes less than threshold. mask -- Name of mask image used for CLEANing default '' means no mask; example: mask='orion.mask'. It is often useful to provide a mask from a previous interactive clean session for a new clean. The mask image shape must be the same for the new clean. cleanbox -- Cleaning region: default: [] defaults to inner quarter of image Three specification types: (a) 'interactive' allows the user to build the cleaning mask interactively using the viewer. The viewer will appear every npercycle interation, but modify as needed The final interactive maks is saved in the file imagename_interactive.mask. (b) Explicit pixel ranges example: cleanbox=[110,110,150,145] clean region with blc=110,100; trc=150,145 (pixel values) Only one clean region can be given this way. (c) Filename with pixel values with ascii format: <fieldindex blc-x blc-y trc-x trc-y> on each line 1 45 66 123 124 2 23 100 300 340 >>> 'interactive' expandable parameter npercycle -- this is the number of iterations between each clean to update mask interactively. Set to about niter/5, can also be changed interactively. imsize -- Image size in pixels (x,y) default = [256,256]; example: imsize=[350,350] imsize = 500 is equivalent to [500,500] cell -- Cell angular size (x,y) default= none; example: cell=['0.5arcsec,'0.5arcsec'] or cell=['1arcmin', '1arcmin'] cell = '1arcsec' is equivalent to ['1arcsec','1arcsec'] cell = '2' makes default cell size of 2 radians! stokes -- Stokes parameters to image default='I'; example: stokes='IQUV'; Options: 'I','IV','QU','IQUV','RR','LL','RRLL','XX','YY','XXYY' field -- Select field using field id(s) or field name(s). ['go listobs' to obtain the list id's or names] default: '':all fields (watch out for multisource data sets!) 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 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 phasecenter -- direction measure or fieldid for the image center default: ''; =>center is the direction of the first field specified in field in the field list. example: phasecenter='6' or phasecenter='J2000 19h30m00.0 -40d00m00.0' spw -- Select spectral window/channels type 'help par.selection' for more examples. NOTE: This selects the data passed as the INPUT to mode default: ''=all spectral windows and channels This parameter interacts with mode='channel' See examples under mode. spw='0~2,4'; spectral windows 0,1,2,4 (all channels) spw='<2'; spectral windows less than 2 (i.e. 0,1) spw='0:5~61'; spw 0, channels 5 to 61, INCLUSIVE spw='*:5~61'; all spw with channels 5 to 61 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 NOTE ';' to separate channel selections spw='0:0~10^2,1:20~30^5'; spw 0, channels 0,2,4,6,8,10, spw 1, channels 20,25,30 weighting -- Weighting to apply to visibilities: default='natural'; example: weighting='uniform'; Options: 'natural','uniform','briggs','radial', 'superuniform' >>> Weighting expandable parameters For weighting='briggs' SEE Reference Manual--imager--imager.weight. rmode -- Robustness mode (for use with Brigg's weighting) default='norm'; example='abs'; Options: 'norm','abs','none' robust -- Brigg's robustness parameter default=0.0; example: robust=0.5; Options: -2.0 to 2.0; -2 (uniform)/+2 (natural) noise -- noise parameter to use for rmode='abs' in briggs weighting example noise='1.0mJy For superuniform/briggs weighting npixels -- number of pixels to determine uv-cell size for weight calculation example noise='1.0mJy uvfilter -- Apply additional filtering/uv tapering of the visibilities. defalt=False; example: uvfilter=True >>> uvfilter expandable parameters uvfilterbmaj -- Major axis of filter (arcseconds) default=1.; example: uvfilterbmaj=12. uvfilterbmin -- Minor axis of filter (arcseconds) default=1.; example: uvfilterbmin=12. uvfilterbpa -- Position angle of filter (degrees) default=0.' example: uvfilterbpa=57. NOTE: taper in (klambda) is roughly (uvfilterbmaj/200) timerange -- Time range: default = '' (all); examples, selectime = 'YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss' Note: if YYYY/MM/DD is missing datr 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' data within one integration of time timerange='>10:24:00' data after this time restfreq -- Specify rest frequency to use for image default='' Occasionally it is necessary to set this (for example some VLA spectral line data). For example for NH_3 (1,1) put restfreq='23.694496GHz' async -- Run asynchronously default = false; do not run asychronously \end{verbatim}