Table of Contents

  1. Introduction
  2. GUI - Main Window
  3. Create SSAP VOTables
  4. Analysis Tools
  5. Fitting Utilities
  6. SED Spectra
  7. Photometric services
  8. Simple Line Access
  9. Theoretical Access
  10. Interoperability
  11. VOSpec Guys
  12. References
  13. User Feedback


Fitting Tool



Fitting Utilities 

The Fitting window gives access to different fitting utilities.
They all work by selecting in the main VOSpec display window the region in which we are interested in performing the algorithm (drag right button of mouse over the spectrum region on which the fitting algorithm shall be run) and then clicking in the "Generate" button.

Current fitting algorithms are the following:

Best FitPolynomial_Fitting

Polynomial FittingPolynomial_Fitting

Black Body FittingBlack_Body_Fitting

Gaussian,Lorentzian,Voigth FittingGaussian_Lorentzian_Voigth_Fitting




TSAP Best Fit

Fits a selected Spectral Energy Distribution to a theoretical model (TSAP service) using
a modified version of the iterative Levenberg-Marquardt Chi-square minimization
algorithm. Both the SED and the theoretical models are not described by continuous
functions. SSA and TSAP servers offer a grid of spectra and theoretical models depending
on several parameters respectively. Therefore, the Chi-square function that the Best Fit
must minimize is a discrete function and the Levenberg-Marquardt method is modified for
the discrete case.

To use the TSAP Best Fit, firstly choose the TSAP Service you wish to fit your selected
spectra to:

 


Then choose the initial starting parameters for the model:

     



Once the best fit model has been found, the chi value and best fit parameters are shown
in the Fitting Window:


 


Finally, the user can choose to load and view the best fit model. The spectra used to
find the best fit are also displayed:


 


Polynomial Fitting

Fits selected part of a spectrum to a n-grade polynomial using Least Squares fitting method.

 

                                   

 


Black Body Fitting

Fits selected part of the spectrum to a black-body continuum spectrum using Levenberg Marquardt Chi-Square minimization algorithm

 

Gaussian, Lorentzian and Voight profiles

Fit selected part of the spectrum to a Gaussian, Lorentzian or Voight profile using Levenberg-Marquardt Chi-square minimization algorithm.

 

In the fitting window we can check the resulting function parameters and the Pearson’s Chi-square value:

 

where:

         observed flux value

         expected flux value

         number of considered flux values

 



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