THE DISTANCE TO THE COMA CLUSTER USING THE B-BAND TULLY-FISHER RELATION

The distance to the Coma cluster was estimated using the B-band Tully-Fisher relation. We took all galaxies for which H I line width data are available in a circle of 4-degrees radius centered on the Coma cluster, and carried out photographic surface photometry on them. The sample represents a substantial fraction of all spiral galaxies for m(z) < 15.5 mag inside this circle. We estimated carefully possible errors which would enter in each step to form the Tully-Fisher relation. In particular, a detailed estimate was made of the cluster population incompleteness bias for the distance estimation. We found that the correction for the sample incompleteness, when combined with the dispersion of the Tully-Fisher relation, increases the distance modulus by 0.3 mag, but that it cannot be as large as the value recently suspected by Kraan-Kortweg, Cameron and Tammann. As our best estimate for the Coma cluster we obtained the distance modulus of (m - M)0 = 34.5 +/- 0.4, which corresponds to a Hubble constant H0 = 92(-17)+21 km s-1 Mpc-1.