## On the derivation of the Tully-Fisher relations## II. Field galaxies, the inverse TF slope and the Hubble constant
The Hubble constant should not show distance-dependence. An inappropriate use of the direct Tully-Fisher relation may lead to a conclusion that is dependent on the distance. This paper tries to answer the question: is it possible to avoid the caveats of the direct relation by applying the inverse Tully-Fisher relation. Under ideal conditions it is possible simultaneously to determine the inverse slope precisely and to find the Hubble constant next to calibration. Ideal conditions are, however, rarely met. Two particular sources of error in the resulting average Hubble constant are considered. A progressive measurement error in angular diameters (apparent magnitudes) causes overestimation of . An asymmetry in the -distribution in the sense of a tail of small rotational velocities tends to shift upwards.
## Contents- 1. Introduction
- 2. The Hubble ratios from the inverse slope
- 3. Fine-tuning the slope and determining
- 4. Measurement errors
- 5. The inverse Spaenhauer diagram
- 6. Implications of an asymmetric -distribution
- 7. Summary
- Acknowledgements
- References
© European Southern Observatory (ESO) 1997 Online publication: May 5, 1998 |