next up previous contents index
Next: UV_PREVIEW Limitations Up: UV_PREVIEW Previous: UV_PREVIEW /FILE   Contents   Index


UV_PREVIEW Algorithm

        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