Kinematics of the Local Universe. V. The value of H_0_ from the Tully-Fisher B and logD_25_ relations for field galaxies.

We have studied the value of the Hubble constant using the KLUN (Kinematics of the Local Universe) sample of 5171 spiral galaxies having isophotal diameters D25 (and partially B-magnitudes), Hi line widths, and radial velocities. The sample is diameter-limited, complete down to D25 =1 : 6 arcmin. As in the rst similar study, where a much smaller magnitude-limited sample was used (Bottinelli et al. 1986), we pay special attention to the problem of Malmquist bias when photometric distances are derived by the Tully-Fisher diameter or magnitude relations. The bias is revealed and overcome by a more advanced version of the method of normalized distances, now taking into account, in addition to diameter and magnitude limits, also Hubble type effect, inclination effect, and variable galactic extinction. Calibration of the Tully-Fisher relations is primarily per- formed using a sample of 15 galaxies with available Cepheid distances, mostly from the HST programmes. This sample does not show signicant trends with distance and is concluded to be closely distance-limited. Analysis of the logH0 vs. dnormalized diagrams allows us to identify the \unbiased plateaus for both the diameter and mag- nitudeTFdistances.Ausefultoolhereintroducedisthetheoret- ical expectation of the bias in cumulative hlogH0i as a function of the fraction of the sample accepted for the plateau. An iter- ative approach is utilized for determining the TF relations, the plateau, and the value of H0 therefrom. Using the Peebles linear velocity eld model with Virgo and our infall velocities equal to 980 km s 1 and 150 km s 1 , respectively, we derived the following values of H0: H0 =5 3 : 4 5 : 0k m s 1 Mpc 1 (Ngal = 415)