The infrared luminosity/H I velocity-width relation and its application to the distance scale.

The Tully-Fisher (1977) relation between absolute blue magnitudes and H I profile widths of galaxies is investigated on the basis of IR photometry (particularly H magnitudes) for 11 spiral galaxies in Virgo and 18 in the Ursa Major cluster. The results confirm the hypothesis that extinction is a major source of scatter in the Tully-Fisher relation. A tighter empirical correlation is discovered in the two clusters by using H magnitudes uncorrected for inclination. The true form of the relationship is found to be a power law whereby luminosity is proportional to the fourth power of rotation velocity. The IR relation is applied to the distance scale, and preliminary results are obtained. These include respective distance moduli of about 31.07 and 31.06 for the Virgo and Ursa Major clusters as well as a Hubble constant of 61 + or - 4 km/s per Mpc.