Ellipse fitting galaxy profiles using contour analysis ELLFOU
The output includes the ellipse parameters, the azimuthally-averaged intensity around them, and the Fourier descriptors. The position of the centre of the galaxy (and a number of other parameters) must be specified interactively (using cursor or keyboard) by the user.
If MODE is false, a list containing the location of galaxies within an image, is obtained from an ASCII file. profiles are generated for all these objects.
If MODE is true, a value for the parameter CURSOR is required. If CURSOR is true, then a cursor/mouse is used (in conjunction with the most recent image displayed) to determine information such as proposed galaxy centre and the largest ellipse radius to be used. If CURSOR is false, a keyboard is used for all input required by the application.
Profiles are obtained for the image co-ordinates determined using the cursor/mouse on the DATA image currently displayed on device XWINDOW. The background count value of that image is 6200 with an associated standard deviation of 390. The magnitude scale assumed has a zero point of 27.5, all profiles will be output to text file ELF, the final results will also be plotted on the XWINDOW device and the galaxy centre co-ordinates are allowed to vary.
Profiles are obtained for the current data image on device XWINDOW. The results are output onto device X2WINDOWS. An ARD file definition in ARDFILE.DAT is used to identify parts of the image that may be used in the profiling operation. An attempt will be made to improve the co-ordinates indicated via the cursor/mouse but the galaxy centre co-ordinates will not be allowed to vary from one profile to the next.
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12:36:53.42 62:12:21.8"
rlim=10. imgdev=x2windows
Profiles for the object at the co-ordinates indicated on image P2 are obtained out to a
radius of 10 pixels. The Current co-ordinate frame of P2 is in the ’
SKY’
domain. Pixel
size in arcseconds is determined automatically from the SKY co-ordinates. The results
are output to device X2WINDOWS and to a file text file ELF. The background count is
6200 with an associated standard deviation of 390.
The program is operated in file mode where co-ordinates of the galaxies to be profiled are read from file COORDS. An ARD file ARDFILE.DAT is used to identify parts of the image that can be used. The global value for the background count value is input in case the COORDS file does not contain a third column with local background values in. The image used as the source is JET. During profiling the galaxy centre is allowed to vary from that originally provided in the file. The profiling operation ceases if the ellipse radius reaches 20 pixels.