K.C. Freeman, PASA, 14 (1), 4.
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Detection Limits
First some estimates of the likely detection limits for the multibeam system. If we take the present Parkes HI system as a guide to the sensitivity of the multibeam system, the empirical detection limit on the integrated HI emission from an unresolved galaxy (from my own experience) is about 
where 
is the velocity width of the HI distribution in km 
and t is the integration time in minutes. This corresponds to an HI mass 
where d is the galaxy's distance in Mpc. For example:
- small HI objects in the nearest group of galaxies: d = 2.5 Mpc,
km , t = 5 min, and the detection limit is M
M
. - large objects at the redshift limit of the survey (about 14,000 km ): d = 200 Mpc,
km , t = 5 min, M
M.
(Mpc) kpc (e.g. 200 kpc at a redshift of about 3000 km ), so galaxy-sized objects will be unresolved over most of the redshift range for the multibeam survey. This is also the case for the known intergalactic clouds, which are described briefly in the next section.
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