1 UV_FIT

        UV_FIT :  Fit point and centro‐symmetric models to a UV table

    This  task  allows fitting of models directly from the visibilities. The
    models are either simple or linear combinations  of  several  functions.
    The results of the fitting process are the position offsets in R.A.  and
    Dec (arc seconds) of the model source from the phase  reference  center,
    and  its  flux (Janskys).  Depending on the fitting functions additional
    fit results are possible. Currently supported  distributions  and  addi‐
    tional fit parameters are:

    POINT     Point source              : None
    E_GAUSS   Elliptic Gaussian source  : FWHP Axis (Major and Minor), Pos Ang
    C_GAUSS   Circular Gaussian source  : FWHP Axis
    C_DISK    Circular Disk             : Diameter
    E_DISK    Elliptical (inclined) Disk: Axis (Major and Minor), Pos Ang
    RING      Annulus                   : Diameter (Inner and Outer)
    EXPO      Exponential brightness    : FWHP Axis
    POWER‐2   B = 1/r^2                 : FWHP Axis
    POWER‐3   B = 1/r^3                 : FWHP Axis
2 UVTABLE$
        TASK\CHARACTER "Input UV table"  UVTABLE$

    The name of the visibility table. See also CLIC\TABLE for PdB data.
2 CHANNEL$
        TASK\INTEGER "First and Last Channel to fit" CHANNEL$[2]

First and last channel to consider in the fitting process.
2 UV_RANGE$
        TASK\REAL      "UV range (max, min) in meters"       UV_RANGE$[2]
The range (in meters) of UV to be selected. "0 1000" is more than acceptable
    for PBDI.
2 NF$
        The number (defaulted to one) of functions involved in  the  fitting
    process. Each function is parametrized as follows:

    TASK\CHARACTER "function #1"         FUNCTxx$
    TASK\REAL      "parameters"          PARAMxx$[6]
    TASK\REAL      "starting range"      RANGExx$[6]
    TASK\INTEGER   "numb. of starts"     STARTxx$[6]
    where "xx" is the function number (01, 02, etc...).

    Supply these four lines for each defined function. The default input pa‐
    rameter file can accomodate up to 4 functions. If  necessary  the  input
    parameter  file  can be modified to add more functions. However, conver‐
    gence will be very difficult to obtain in such a case...

2 FUNCT01$
        TASK\CHARACTER "Function #1" FUNCT01$

    The type of the distribution required in the fitting process.  Currently
    supported functions are:
            POINT     Point source
            E_GAUSS   Elliptical Gaussian source
            C_GAUSS   Circular Gaussian sources
            C_DISK    Circular Disk
            E_DISK    Elliptical Disk (inclined)
            RING      Annulus
            EXPO      Exponential brightness
            POWER‐2   B = 1/r^2
            POWER‐3   B = 1/r^3

    Remark: See NF$ for additional help
2 PARAM01$
        TASK\REAL      "Parameters"          PARAM01$[6]

    Your guesses as input parameters for the fitting process. Six parameters
    have to be defined for each function. The parameter list used in the fit
    is:
    POINT    : Offset R.A., Offset Dec, Flux
    E_GAUSS  : Offset R.A., Offset Dec, Flux, Maj. diam., Min. diam., Pos Ang
    C_GAUSS  : Offset R.A., Offset Dec, Flux, Diameter
    C_DISK   : Offset R.A., Offset Dec, Flux, Diameter
    E_DISK   : Offset R.A., Offset Dec, Flux, Maj. diam., Min. diam., Pos Ang
    RING     : Offset R.A., Offset Dec, Flux, Inner Diameter, Outer Diameter
    EXPO     : Offset R.A., Offset Dec, Flux, Diameter
    POWER‐2  : Offset R.A., Offset Dec, Flux, Diameter
    POWER‐3  : Offset R.A., Offset Dec, Flux, Diameter
    Note  that  if the guesses are not sufficiently accurate the fit may not
    converge.
2 PARAM02$
     same as PARAM01$
2 PARAM03$
     same as PARAM01$
2 PARAM04$
     same as PARAM01$
2 RANGE01$
        TASK\REAL      "starting range"      RANGE01$[6]

    Your guess for the starting range of the parameters used in the  fitting
    process.
2 RANGE02$
     same as RANGE01$
2 RANGE03$
     same as RANGE01$
2 RANGE04$
     same as RANGE01$
2 START01$
        TASK\INTEGER   "numb. of starts"     START01$[6]

    The  number of starts is related to the accuracy with which the starting
    range is sampled. A rough estimate of the time required for the  fitting
    is given by the time required for a single start scaled by the number of
    starts in each parameter. Defaults to 0. Use ‐1 to FIX parameters.
2 START02$
     same as START01$
2 START03$
     same as START01$
2 START04$
     same as START01$
2 RESULT$
        TASK\CHARACTER "Output file"     RESULT$

    The name of the output table  (GREG\COLUMN,  GRAPHIC\IMAGE)  summarising
    the  fit  results. The file is organized as a MxN matrix, where M is the
    number of channels in the input table (UVTABLE$) and where the organiza‐
    tion in N is the following:

    N:  P1 P2 P3 Vel A1 A2 A3 Par1 Err1 Par2 Err2 ... A1 A2 A3 Par1 Err1 ...

    where P1 = RMS of the fitting process
          P2 = number of supplied functions  (NF$)
          P3 = total number of parameter
         Vel = velocity of the i‐th channel (i lies between 1 and M)
          A1 = 1 (for the first function), = 2 (for the second function)
          A2 = function code (POINT = 1, E_GAUSS = 2, ... , POWER‐3 = 8)
          A3 = number of parameters of the function
        Parx = result of the fit parameter (order of appearance in PARAMxx$)
        Errx = error of the fitting process for the parameter Parx

    Fitting  models  with the functions POINT and C_GAUSS produce files with
    N=24.  A procedure (INPUT PLOTFIT) is available to obtain plots from it.
2 RESIDUALS$
        TASK\CHARACTER "residuals UVtable"   RESIDUALS$

    The name of the residual UV table. The file is obtained from  the  input
    visibility  table (UVTABLE$) upon subtraction of the model determined by
    the fitting process.
2 SUBSF01$
        TASK\LOGICAL   "Subtract function"        SUBSF01$

    Tells if the corresponding function is to be substracted in the residual
    table.
2 SUBSF02$
     same as SUBSF01$
2 SUBSF03$
     same as SUBSF01$
2 SUBSF04$
     same as SUBSF01$
1 END















































