The first false colour image of the HI
velocity field of a spiral galaxy. This is the face-on spiral galaxy M101
- the Pinwheel Galaxy. It was made in Groningen in 1975 following the
methods described in
Ekers, Allen &
Luyten 1973 (see Section 6c). The broadband weak radio continuum is also
included in this image and becomes white while the rainbow colours show the
full range of velocities from blue- to red-shifted. The 21-cm data were
obtained with the Westerbork Synthesis Radio Telescope
(Allen, Goss
& van Woerden 1973).
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