Luminosity-line width relations and the extragalactic distance scale. I - Absolute calibration

Multicolor CCD photometry is presented for a sample of 15 spiral and irregular members of the Local, Sculptor, and M81 groups with M B ≤ -16.0 and relevant as potential calibrators of the luminosity-line width relations. The sample contains those galaxies for which a ground-based study of Cepheid variables could provide accurate distances and hence an absolute calibration for the relations. Unfortunately, only six of the systems presently have reliable independent distance estimates, but this number is sufficient to provide a reasonable calibration