[ADVANCED\]MAP_CONTINUUM [DIRTY|CLEAN|Other] /METHOD GLOBAL [Thresh-
old [Nhisto]]
Compute the integrated spectrum (over the region specified by CENTER
and SIZE variables), and delineate the line-free region by Gaussian fit-
ting the histogram of the spectrum intensity.
The optional arguments control the algorithm. Threshold is clipping
level in sigma units: values in range 2.5 - 5 are usable (default 3.5).
Nhisto is the number of histogram bins. The default is to adjust this
number depending on the number of channels in the data. This is the same
algorithm as used in UV_CONTINUUM, or in a per pixel mode by the GAUSS
method.
The continuum is then derived by integrating in the line-free regions.
This method is fast, and gives a uniform noise since the same channels
are used for all pixels. It may be inaccurate into several ways:
- Regions with strong broad line may still be contaminated by emission
from the line wings
- The same applies to regions with line confusion.
- Continuum emission in regions with no line emission is not derived to
the maximum sensitivity. This can be an issue in case of line confusion
at some positions.
Gildas manager
2023-06-01