| Abstract | Twenty-one relatively large irregular galaxies spread over an absolute magnitude range between -18.9 and -13.7 are mapped with the 100 m radio telescope at Effelsberg at a wavelength of 21 cm to derive global parameters, to search for extended H I envelopes, and to study the influence of the envelope on the integrated profile. A model-fit-technique is used to determine the parameters of the H I distribution, the geometry, and the rotation of the galaxies for objects smaller than 20 arcmin in angular extent. The half power width of the observed H I distribution is similar to the Holmberg diameters, and eight of the galaxies have extended H I envelopes at a low H I surface density of 10 to the 19th atoms per sq cm. |
