The output files generated by the applications SECTOR, ELLFOU, ELLPRO, GAUFIT and GRAPHS are created in a simple ASCII text format. Examples of the output from each of the applications are shown as Appendix F
The structure of ELLPRO and ELLFOU output files are very similar. Each has as its first line a title identifying the format version of the rest of the file together with the name of the application that generated it. This is then followed by lines of text that define the source image that was used, its background value (and its associated standard deviation), the pixel size in arc seconds, the galaxy co-ordinates in both Current and Base frames, the zero point of the surface brightness magnitude scale (magnitudes per arc seconds) and the number of points present. Essentially every piece of data required for subsequent calculation of scale length, display of results or reconstruction of a synthetic galaxy are retained for later use. Below all this comes the ellipse parameter data arranged in columns preceeded by a heading. The ellipse parameter data is followed by the associated Fourier descriptor values for each profile.
The SECTOR output file format is slightly different. It again identifies values such as pixel size on the original image but includes also the estimates of the scale length determined when SECTOR was run. These are not employed by GRAPHS but are retained for your convenience and later reference. Unsurprisingly, the file does not contain any ellipse parameters or Fourier descriptors since SECTOR does not derive these. It instead contains columns of radii and mean pixel values together with estimates of surface brightness.
The GRAPHS output file is (unless ELLPRO or ELLFOU has been used to examine examined several galaxies found on a given image in one go) a much smaller affair. It again has an identifying format header but this is followed simply by the name of the image and information on the galaxy image co-ordinates, scale lengths calculated and the estimates for the central surface brightness.
LOBACK output files are similar in layout to those described above. The first part of the file describes the file format version, the application name and the image that was examined. After this it give a table showing the local background estimates. Clearly, the number of rows in this table is defined by the number of entries that were in the co-ordinate text file input to LOBACK.
It can be seen that all the lines beginning ‘##’ describe what is on the next line (or subsequent lines) of text. If the program GRAPHS encounters such a start to a line, it then examines the remainder of the line to determine exactly what type follows.
You can easily construct your own files for analysis or display by GRAPHS. The important considerations are that the file must contain all the data and that each piece of data must be preceeded by a line beginning with ‘##’ that correctly identifies it. The actual position of these within the file is otherwise unimportant, thereby making things easier. It is hoped that you will find the file reading parts of GRAPHS fairly robust and tolerant.
Lines beginning with the ‘!’ character are ignored by the software and are merely contain helpful comments.
The GAUFIT output file is a very simple affair and only a slight variation on those seen above. As before the file contains a header to allow the file source to be identified. It also contains the background value and the standard deviation of that value for the source image. The table following the header contains location of the object on the image (column 1 and 2) and the position angle, Sa, Sb and source peak value in columns 3 to 6. This structure has been adopted so that, if the header is removed, the output file could be used as the basis of the text file input for another minimisation run. If the parameter FWHM was set true, then the results will be written as FWHM here rather than standard deviations, and when a source-position file is read in, the entries in the corresponding columns will be interpreted as FWHM.
GAUFIT writes the parameter uncertainties after the parameter values. Note that you will need to remove or comment these out if you wish to use this GAUFIT output file as a later GAUFIT input file – if you do not, the uncertainties will be interpreted as specifying new sources, to your (and GAUFIT’s) considerable confusion.