Displays/analyses the results generated using SECTOR, ELLFOU or ELLPRO


Displays galaxy profiles and performs scale length analysis. The data used comes from an ASCII text input file generated by ESP application ELLPRO, ELLFOU or SECTOR.

The application can be operated in two modes; interactive and file.

INTERACTIVE - The user can select whether the radius range used to calculate the scale length values are input via a keyboard (CURSOR=FALSE) or via the mouse/ball (CURSOR=TRUE).

FILE - The user inputs the name of the text file output by ELLPRO, ELLFOU or SECTOR and the radius range over which isophotes will be employed to calculate the galaxy scale length.

In the file mode, graphs are not displayed. Once the input filename has been entered, no further user interaction is required. The input file should contain the contents of a single file output from ELLFOU, ELLPRO, SECTOR, or, alternatively, several such files concatenated together. In both modes, the name of the text file created by GRAPHS to store results in, is supplied by the user.

The X and Y co-ordinates output by SECTOR, ELLFOU and ELLPRO, and hence those plotted by GRAPHS, are in the Base frame coordinate system (units pixels) of the processed NDF images.




Should the profile be displayed/analysed again?
Position angle rotation convention. TRUE=clockwise positive.
Position angle offset. Units degrees.
Whether the radius value range is to be identified using the graphics cursor or the keyboard. Only values within the user defined range will be used to determine the scale length.
Name of the graphics device on which to display the results graph.
The range of radius values over which the scale length ’fits’ are to be calculated. Units arc seconds.
Name of the text file containing the galaxy profile.
The radius below which a profile will not be included in the automatic radius calculation. Units arc seconds.
Is the application to be used interactively or in file mode? TRUE = interactive. FALSE = file mode.
OUT = _CHAR (Read)
File name for the output text file containing the scale length data.
The display mode used for the radius axis of the graphs.
  • Q = quarter power

  • L = logarithmic

  • S = square root

  • R = linear The radius values displayed are the equivalent radius (R) when using ELLPRO/ELLFOU input files and distance from the galaxy origin when using SECTOR derived files.

Should the radius range be selected automatically?
WHATD = _CHAR (Read)
What will be displayed against radius on the graphs.
  • B = Brightness of the profile in terms of sky i.e. (I-Back)/Sigma

  • C = Count value of the profile

  • E = Ellipticity of the profile

  • FC1 = First cosine Fourier descriptor

  • FC2 = First sine Fourier descriptor

  • FC3 = Second cosine Fourier descriptor

  • FC4 = Second sine Fourier descriptor

  • FS1 = Third cosine Fourier descriptor

  • FS2 = Third sine Fourier descriptor

  • FS3 = Fourth cosine Fourier descriptor

  • FS4 = Fourth sine Fourier descriptor

  • P = Position angle of the profile

  • S = Surface brightness of the profile

  • X = X co-ordinate (Base frame)

  • Y = Y co-ordinate (Base frame)


graphs mode=true infile=results.dat out=scales.dat rrange=true cursor=true whatd=s radisp=r device=xwindows

The file RESULTS.DAT is examined and its contents displayed graphically as required. The first display will be of linear radius versus surface brightness and will be shown on device XWINDOWS. The radius range for the isophotes to be employed in the scale length calculation are selected interactively via the mouse/ball.

graphs mode=true infile=profs.dat out=lengths.dat rrange=false fitlim=1,20 cursor=false whatd=p radisp=l device=x2windows

The results stored in file PROFS.DAT are read one after the. other The profiles and ’fits’ may be observed interactively as graphs on device X2WINDOWS. The first display will be of log(radius) versus position angle. The radius range used when calculating the scale length is 1 to 20 arc seconds. results are output to file LENGTHS.DAT.

graphs mode=false infile=elf1.dat out=lengths.dat rrange=true
The profile data required is read in from file ELF1.DAT. Data from isophotes chosen by the application are selected for use in the scale length analysis. The results are output to file LENGTHS.DAT.
graphs mode=false infile=profs.dat out=scales.dat rrange=false fitlim=0.5,7

Profile data read in from file PROFS.DAT is analysed to determine the scale length using isophotes with a radius in the range 0.5 to 7 arc seconds. The results are output into text file SCALES.DAT.


Parameters surrounded by curved brackets may only be adjusted via the command line.

Within ESP the scale lengths are calculated by assuming an exponential brightness profile for spiral galaxies and an exponential modified by a quarter power law for elliptical galaxies. The scale length value given is derived from the decay constant of the exponential functions.