... The high angular resolution CGPS images of atomic hydrogen emission reveal a wide-spread, cold atomic hydrogen component of the interstellar medium in the form of dark self-absorption cloud complexes. These clouds resemble molecular cloud complexes in structure and trace the spiral arm structure of the Galaxy. ... Nevertheless, continuum absorption studies show that some of the cold atomic hydrogen clouds have temperatures as low as 15 - 20 K --- similar to dense molecular clouds. ...

... 2.3 Data acquisition Spectra generated by the Multibeam correlator contain the usual structure seen in spectra from other H i instruments: a bandpass spectrum which is the sum of the sky , ground and receiver temperatures multiplied by the product of the filters in the receiver chain; superimposed on this is a noise ... Note also that sources extended much beyond ,40 arcmin can be imaged poorly in HIPASS images because of the bandpass sidelobe effect described in Section 3.3. ...