Next: 20.5.3 GAUSS Up: 20.5 MAP_CONTINUUM Previous: 20.5.1 /METHOD Contents Index
Compute the integrated spectrum (over the region specified by CENTER and SIZE variables), and delineate the line-free region by Gaussian fitting 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.