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Clean Component files       CCdsssvv


A. Overview

Function: CLEAN components are stored in this table by APCLN (or other
Clean programs) during the deconvolution process.  CLEAN components
represent a set of point sources which when convolved with the dirty
beam and added to the residual map gives the original dirty map.  The
Fourier transform of these POINT components should, after CLEAN
converges, reproduce the observed data.
     Other tasks write CC files containing Gaussian (or other model)
fits to images or UV data.

Details: CC files are extension tables, separate from but associated with
an image or uv data file.  CC tables use the TABINI-TABIO table
structure.


Names: The file name is CCdsssvv, where d is the update code and sss is
the sequential position of the image header in the catalog file for
that disk and vv is the version number.


B. File Structure

     Logical records consist of a single model component.  If only three
columns are present then the file contains only point components.

     CC tables headers contain no KEYWORDs.

   Table entries:

       Title          Units   code      Description
  ----------------- --------- ---- -------------------------------------------
    FLUX               Jy      1E  Flux density of component.
    DELTAX           degrees   1E  Offset from reference pixel in X direction
                                   (RA for unrotated images)
    DELTAY           degrees   1E  Offset from reference pixel in Y direction
                                   (Dec for unrotated images)

   The following are optional:

    MAJOR AX         degrees   1E  Gaussians: Major axis size (FWHM)
                                   Spheres: Radius
    MINOR AX         degrees   1E  Gaussian: Minor axis size.
    POSANGLE         degrees   1E  Gaussian: position angle (from N thru E)
    TYPE OBJ                   1E  Model type:
                                     0 => point model.
                                     1 => gaussian on sky.
                                     2 => gaussian convolved by observation.
                                     3 => uniform, optically thin sphere.

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C.  User notes
  The "code" column is element_count + basic type code.
basic type codes: D=Double precision, E=single precision,
   A=character, J=long integer, L=logical, I=short integer, X=bit.
     The positions given are those projected onto the same plane as
the original image ie. the number of pixels from the reference pixel
times the pixel spacing.  If accurate positions are desired the
appropriate transformation must be made.


D.  Routines for writing CC files - CCINI, TABINI, TABIO

     The tasks APCLN, SDCLN and MX (regular cleaning), IMFIT, JMFIT
and UVFIT may write in CC files.  Chapter 13 of "Going AIPS"
describes the routines to access tables files.

E. Routine to access CLEAN component file: CCINI, TABINI, TABIO

     The tasks PRTCC and PRTAB will print the contents of CC tables.
