Extended Surface Photometry Toolbox
Profiling a galaxy
- Select the source or sources you wish to have profiled. Do this
using the `Objects' tab. In this panel, press `Add source', and
then drag out a circle on the image to indicate the outer limit
of the profiling process. After you have added a source, you
can adjust the position of a circle by dragging it, or adjust
its size by dragging on the small square grip which appears on
it. You can then move on to the `Ellipse Fit' tab.
- To delete a source, select it in the text list of sources, and
press the `Delete source' button.
- Specify the background on your image. You can do this either by
inserting the values, if you know then, or by pressing the
`Estimate...' button to have the toolbox make an estimate for
- Specify an ARD file, if you want. You can use the `Image
regions...' toolbox to help you here.
- Choose the method you wish to use to obtain the fitted
ellipses. There are three possibilities: `using isophote
contours', which corresponds to the ESP ELLFOU task, and works
by fitting ellipses to isophote contours; `using intensity
analysis', which corresponds to ELLPRO, and uses a simpler
intensity-based method; or use this last method's slow variant,
which should give better results at low radii.
- There are a number of `expert' options in this panel. The use
of these options can reasonably be understood only in
conjunction with the ESP documentation, SUN/180, to which you
should refer for further details.
The toolbox can produce output in two formats. The first is the
more-or-less human-readable format which ESP has traditionally used:
this is sent to the file named in the field `Text output'. The second
is a more structured, but still largely readable, format called STL,
or `small text list' (described in detail in the CAT library
documentation, SUN/181). The library which writes this format
requires that the output filename is restricted to alphanumeric
characters plus underscore, and ends in ".txt". If you do not supply
file names here, the toolbox will supply defaults.