UV_PREVIEW computes for Ntapers different tapers the spectrum to-
wards the phase center. The taper ranges are determined from the avail-
able baseline lengths and telescope diameter. Ntapes is controlled by
the value of Key TAPER.
These spectra are then smoothed by averaging several channels (1,4,16
and 64) to be sensitive to different linewdiths. The nummber of smoothed
spectra per taper is controlled by the value of Key SMOOTH.
For each spectrum, UV_PREVIEW then attempts to figure out if there is
line emission and the line-free channels to define the continuum level.
This is based on the histogram of the intensity distribution of all
channels. The most likely value and the noise level is derived from this
histogram. An iterative scheme, blanking out of range (presumably line
emission) channels, is used for this to converge towards a Gaussian his-
togram, which normally represents the noise distribution around the con-
tinuum level.
As a last step, blanked channels are accumulated in a list of channels,
which thus contain possible line emission at any of the Ntapers angular
scales and Nsmooth spectral resolutions.
Gildas manager
2023-06-01