METHOD

FIT\METHOD Arg [Parameters ...] Select the line profile for fits. Five type of profiles are available. - GAUSS Select gaussian profiles. Up to 5 Gaussian, dependent or independent can be fitted in a spec- trum, according to command lines. Variables are Area Velocity and Width (FWHM). - SHELL Horn-type profiles for Circumstellar Shells. Variables are 1) Area [K.MHz] 2) Center offset [in MHz] 3) Full Width at zero level, and 4) Horn-to-center ratio (-1 for parabolic optically thick lines, 0 for flat-topped lines, Infinity for per- fectly double peaked lines). Profiles are symmetric. Up to 5 depen- dent or independent lines may be fitted. X axis must be frequency. - NH3(1,1) or NH3(2,2) or NH3(3,3) Compute ammonia line profiles, with the assumptions of gaussian ve- locity distribution and equal excitation temperatures. Variables are 1) Main group opacity times ( Excitation temperature minus Back- ground temperature), 2) Velocity, 3) Width (FWHM = sqrt(8.0*alog(2.0)) * line 2nd order moment), and 4) Main group opacity. Up to 3 independent lines may be fitted, but it may be slow... - HFS FileName for HyperFine Structure This is very similar to the NH3 method, but the coefficient to de- scribe the hyperfine structure are read in the file FileName. The first line of this file must contain the number of hyperfine compo- nents (< 40). The other lines must contain, for each component, the velocity offset and the relative intensity. The parameters are the same as for NH3 method. - CONTINUUM for Continuum drifts. Fit a single gaussian and a linear baseline at the same time, with automatic determination of the parameters. Uses beam-switched infor- mation for two-component fitting if required. The command METHOD CONTINUUM accept additional arguments, which can be used to cus- tomize the fit. METHOD CONTINUUM [Width [Area_Ratio [Width_Ratio]]] where - Width is the width of the beam in arc seconds. By default, Width is a free parameter. - Area_Ratio is the reference to main beam area ratio, used for beam- switch observing. By default, Area_Ratio is 1. - Width_Ratio is the reference to main beam width ratio, used for beam-switch observing. By default, Width_Ratio is 1. A * can be used instead of a numerical value for each parameter, and in- dicates that the parameter is free. Note that in command LINES, one enters the peak line antenna temperature instead of the first variable in the guesses, except for SHELL method. Command LINES has no effect for CONTINUUM. CONTINUUM and GAUSS methods only are relevant for continuum data, while GAUSS, SHELL, NH3 and HFS methods can be used for spectroscopic data.

Gildas manager 2014-07-01