The I-band Tully-Fisher relation for Sc galaxies: 21 centimeter HI line data

A compilation of 21 cm line spectral parameters specifically designed for a pplication of the Tully-Fisher (TF) distance method is presented for 1201 s piral galaxies, primarily field Sc galaxies, for which optical I-band photo metric imaging is also available. New H I line spectra have been obtained f or 881 galaxies. For an additional 320 galaxies, spectra available in a dig ital archive have been reexamined to allow application of a single algorith m for the derivation of the TF velocity width parameter. A velocity width a lgorithm is used that provides a robust measurement of rotational velocity and permits an estimate of the error on that width taking into account the effects of instrumental broadening and signal-to-noise. The digital data ar e used to establish regression relations between measurements of velocity w idths using other common prescriptions so that comparable widths can be der ived through conversion of values published in the literature. The uniform H I line widths presented here provide the rotational velocity measurement to be used in deriving peculiar velocities via the TF method.