The image sideband equivalent of the rest frequency ImagFreq
The value is calculated by first transforming the rest frequency (given by the RestFreq
attribute) from the standard of rest of the source (given by the SourceVel and
SourceVRF attributes) to the standard of rest of the observer (i.e. the topocentric
standard of rest). The resulting topocentric frequency is assumed to be in the same
sideband as the value given for the DSBCentre attribute (the "
observed"
sideband), and
is transformed to the other sideband (the "
image"
sideband). The new frequency is
converted back to the standard of rest of the source, and the resulting value is
returned as the attribute value, in units of GHz.