Create a multi-field deconvolved 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, multiscale) clark clark hogbom multiscale entropy Image size in pixels (nx,ny), symmetric for single value 256256 The image cell size in arcseconds [x,y]. 1.01.0 Field Identififier or direction of the image phase center Stokes params to image (I,IV,QU,IQUV,RR,LL,XX,YY,RRLL,XXYY) I I IV QU IQUV RR LL RRLL XX YY XXYY Maximum number of iterations 500 Loop gain for cleaning 0.1 Flux level to stop cleaning (unit mJy assumed) 0.0 Set of mask images used in cleaning clean box regions or file name or \'interactive\' Number of channels in output image 1 Start channel 0 Channel width (value > 1 indicates channel averaging) 1 Field Name Spectral windows:channels: \'\' is all Range of time to select from data rest frequency to use in image Input single dish image to use for model Name of output(/input) model image Weighting to apply to visibilities natural natural uniform briggs radial superuniform Individually weight the fields of the mosaic False Robustness mode (for Briggs weightting) norm none norm abs Briggs robustness parameter 0.0 -2.0 2.0 Gridding method for the image mosaic ft sd both mosaic Change the threshold at which the deconvolution cycle will stop, degrid, and subtract from the visiblities. 1.5 Cycle threshold doubles in this number of iterations -1 Controls scaling of pixels in the image plane SAULT PBCOR SAULT Minimum PB level to use 0.1 Target image sigma 0.001 Target flux for final image 1.0 Constrain image to match target flux False Name of MEM prior images Stop the component search when the largest scale has found this number of negative components 2 resolutions in pixel units 0310 Number of iterations before interactive masking prompt 100 number of pixels to determine cell size for superuniform or briggs weighting 0 noise parameter for briggs weighting when rmode=\'abs\' 0.0 1 0 first channel in image relative to data channels 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 2 0.01Jy 1.0Jy False '' none 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 100 Two 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 mosaic 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='ngc5921.ms' imagename -- Pre-name of output images: default: none; example: imagename='m2' output images are: m2.image; cleaned and restored image m2.flux; relative sky sensitivity over field m2.model; image of clean components m2.residual; image of residuals m2.interactive.mask; image containing clean regions 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, but only channel is complete. 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','multiscale','entropy' 'hogbom' Cleans from the images only. Only inner quarter of image is cleaned 'clark' Cleans from gridded us data. Only inner quarter of image is cleaned 'multiscale' cleans with several resolutions using hobgom clean Currently much slower than single resolution. For extended sources, try single resolution with interactive and 'entropy' Maximum entropy algorithm is still experimental and not recommended for general use >>> multiscale expandable parameter scales -- in pixel numbers; the size of component 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) negcomponent' -- Stop component search when the largest scale has found this number of negative components; -1 means continue component search even if the largest component is negative. default: 2; example: negcomponent=-1 >>> entropy (MEM) expandable parameters (experimental) sigma -- Target image sigma default: '0.001Jy'; example: sigma='0.1Jy' targetflux -- Target flux for final image default: '1.0Jy'; example: targetflux='200Jy' constrainflux -- Constrain image to match target flux; otherwise, targetflux is used to initialize model only. default: False; example: constrainflux=True prior -- Name of MEM prior images default: ['']; example: prior='source_mem.image' imsize -- Image pixel size (x,y) default = [256,256]; example: imsize=[350,350] imsize = 500 is equivalent to [500,500] cell -- Cell size (x,y) default= none; example: cell=['0.5arcsec,'0.5arcsec'] or cell=['1arcmin', '1arcmin'] cell = '1arcsec' is equivalent to ['1arcsec','1arcsec'] NOTE:cell = '2' makes default cell size of 2 radians! phasecenter -- direction measure or fieldid for the mosaic center default: 0 (imply field=0 as center); example: phasecenter=6 or phasecenter='J2000 19h30m00 -40d00m00' stokes -- Stokes parameters to image default='I'; example: stokes='IQUV'; Options: 'I','IV''QU','IQUV','RR','LL','XX','YY','RRLL','XXYY' niter -- Maximum number iterations, set to zero for no CLEANing default: 500; example: niter=500 gain -- Loop gain for CLEANing default: 0.1; example: gain=0.5 threshold -- Flux level at which to stop CLEANing (units=mJy) default: 0.0; example: threshold=0.0 mask -- Name of mask image used for CLEANing default '' means no mask; example: mask='orion.mask'. It is useful to use a mask from a previous interactive mosaic session for a new execution. The mask image shape must be the same as the new mosaic. 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. field -- Select fields in mosaic. 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 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 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 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 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 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' 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' sdimage -- Input Single Dish image to use for model default='' (no image); example: sdimage='n4826_12mchan.im' modelimage -- Name of output(/input) model image default='' (none=imagename.model); modelimage='orion.model' Note: This specifies the output model if a single dish image is input or the output model name from the imaging weighting -- Weighting to apply to visibilities: default='natural'; example: weighting='uniform'; Options: 'natural','uniform','briggs','radial', 'superuniform' >>> Weighting expandable parameters For weighting='briggs' rmode -- Robustness mode (see help mosaic) 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 npixels=7 mosweight -- Individually weight the fields of the mosaic default: False; example: mosweight=True This can be useful if some of your fields are more sensitive than others (i.e. due to time spent on-source); this parameter will give more weight to higher sensitivity fields in the overlap regions. ftmachine -- Gridding method for the image; Options: ft (standard interferometric gridding), sd (standard single dish) both (ft and sd as appropriate), mosaic (gridding use PB as convolution function) default: 'mosaic'; example: ftmachine='ft' cyclefactor -- Change the threshold at which the deconvolution cycle will stop, degrid and subtract from the visibilities. For poor PSFs, reconcile often (cyclefactor=4 or 5); For good PSFs, use cyclefactor 1.5 to 2.0. default: 1.5; example: cyclefactor=4 cycle threshold = cyclefactor * max sidelobe * max residual cyclespeedup -- Cycle threshold doubles in this number of iterations default: -1; example: cyclespeedup=500 scaletype -- Controls scaling of pixels in the image plane. default='SAULT'; example: scaletype='PBCOR' Options: 'PBCOR','SAULT' 'SAULT' scale makes an output image where the noise is constant across the whole mosaic. However, the image is NOT corrected for the PB pattern, and therefore is not "flux correct". Division of the SAULT image_name.image image by the image_name.flux image will produce a "flux correct image". The 'PBCOR' option uses the SAULT scaling scheme for deconvolution, but when interactively cleaning shows the primary beam corrected image; the final PBCOR image is "flux correct" minpb -- Minimum PB level to use default=0.1; example: minpb=0.01 async -- Run asynchronously default = False; do not run asychronously