+==========================
 README_irsa_18_09_2014
 heikki.salo@oulu.fi
===========================


S4G PIPELINE 4 decomposition files:


Stored for each galaxy (IDE):
=============================


1) Input data for GALFIT decompositions 
---------------------------------------

fits-files:

  IDE.phot.1_nonan.fits     = 3.6 micron image used in decompositions,
                              Bad pixel values (NaN's) removed
                              header modified to make sure GALFIT works correctly

  IDE.1.finmask_nonan.fits  = corresponding mask-file

  IDE.phot.1_sigma.fits_ns  = -"- sigma-image

  PSF-1.composite.fits      = PSF-image  (common for all images)


2) Output from GALFIT decompositions
------------------------------------

a) ascii-files:

  IDE_onecomp.outgal    =    Automatic best fit parameters for 1-component Sersic model

  IDE_twocomp.outgal    =    -"-  for 2-component sersic+expo (or sersic-edgedisk) fit

  IDE_MODEL.outgal      =    Final decomposition model with up to 4 different components

                             MODEL-string identifies the components of the fit (see below) 
                              'b'    indicates bulge-component
                              'd'    indicates disk -"-
                              'bar'  indicates non-axisymmetric structure, mainly bars
                                     ('barf' indicates that bar truncation radius was fixed)                
                              'n'    indicates nucleus (or nonresolved bulge)
                              'z'    indicates edge-on disk


  These outgal-files contain the decomposition output parameters (see the GALFIT manual)
  Together with the input fits-files, the user can immediately repeat/refine the decompositions
  starting from the outgal-file 


b) fits-file (for the FINAL model)

  IDE_MODEL.outgal_subcomps.fits      Final decomposition output images: total model, 
                                      model components in various fits-extensions (see the GALFIT manual)
                                      File header contains also final decomposition parameters.

c) jpg-files (for the FINAL MODEL)

   IDE_MODEL.outgal_profile.jpg        Decomposition model compared with observations:
                                       - shows surface brightness at each image pixel vs distance from galaxy center
                                         Observed image, model image, and model components displayed separately
                                       - Collects also decomposition input & output parameters
                                         Labels indicate relative contribution of model components  

   IDE_MODEL.outgal_residual.jpg       Model-observation comparisons:
                                         upper row: clipped 3.6 micron image, masked image
                                         lower row: model image, OBS-MODEL residual
                                            
   IDE_MODEL.outgal_1dprof.jpg         Decomposition model profiles compared with observations: 
                                       - shows surface brightness as a function of isophotal semi-major axis,
                                         comparing IRAF ellipse fits to the observed image and to the
                                         model image (using isophotes of the observed image)
                                        

   IDE_MODEL.outgal_components.jpg     Schematic plot of model components:
                                       -  Upper row: Observed image and model image, with different model
                                          components marked: colors correspond to profile plots, and the semimajor-axis
                                          of the ellipse is 2 times the effective radius of the components
                                       -  Lower row: same as upper row, except projected to the disk plane
                                         (assuming zero-thickness). Empty in case on edge-on final model.


====================================================================================================================
  The final decomposition models, as well as various intermediate steps involved, are illustrated in the web-page
  http://www.oulu.fi/astronomy/S4G_PIPELINE4/MAIN
====================================================================================================================