20.16 UV_FIT

[ADVANCED\]UV_FIT [Func1 .. FuncN] [/CONTINUUM [Field]] [/INDEX SpIndex [Frequency]] [/OUTPUT [File]] [/QUIET] [/RANGE Min Max TYPE]] [/SAVE File] [/UVRANGE Min Max [Unit]] [/WIDGET N]

Fit UV data with a few simple functions. Func1 to FuncN (currently N < 5) are the names of the functions to be fitted. If not specified, the last names (or those attributed by the /WIDGET options) are used.

The models are either simple functions or linear combinations of simple functions. Input parameters and results of the fitting process are (in sequential order) the position offsets in R.A. and Dec (in arc second) of the model source from the phase reference center, and its flux (Jansky). Depending on the fitting functions additional parameters and fit results are possible. Currently supported distributions and additional fit parameters (in order) are:

 POINT     Point source		    : None 	
 E_GAUSS   Elliptic Gaussian source  : FWHM Axes (Major and Minor), Pos Ang
 C_GAUSS   Circular Gaussian source  : FWHM 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    : FWHM Axis
 POWER-2   B = 1/r^2		    : FWHM Axis
 POWER-3   B = 1/r^3		    : FWHM Axis
 U_RING    Unresolved Annulus         : Radius
 E_RING    Inclined Annulus          : Inner, Outer, Pos Ang, Ratio
 E_EXPO    Elliptic exponential       : FWHM Axes (Major and Minor), Pos Ang
 SPERGEL   Spergel brightness profile : FWHM Axis, nu
 E_SPERGEL Elliptic Spergel profile   : FWHM Axes (Maj. and Min.), Pos Ang, nu

The function parameters are found in a SIC structure named UVF% under names UVF%PARi%PAR[7] (starting values), UVF%PARi%RANGE[7] (starting ranges) and UVF%PARi%START[7] (number of starts). The /WIDGET option is a convenient way to set these variables.

UV_RESIDUAL will compute the fit residual when used after UV_FIT, while it computes the residual from the Clean component list if used after CLEAN.

WRITE UV_FIT file[.uvfit] will save the fit results in a GILDAS table, in the same format than that of the UV_FIT task.

The Pos Ang (PA) are the Position Angles of the major axis of the distribution. To deproject the elliptical shapes, one should use the Position Angle of the rotational axis, PA-90 (see commands UV_CIRCLE, UV_DEPROJECT and UV_RADIAL)