*Astron. Astrophys. 331, 1-10 (1998)*
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## Kinematics of the local universe
### VI. *B*-band Tully-Fisher relation and mean surface
brightness
**
G. Theureau
**
Observatoire de Paris-Meudon, CNRS URA1757, F-92195
Meudon Principal Cedex, France
*Received 7 May 1997 / Accepted 19 September 1997*
**Abstract**
Continuing our study of the type dependence of the TF relation, we
present a new attempt to reduce the scatter of that relation by using
the observed mean surface brightness of
galaxies. It is shown that the zero-point of the relation is a
continuous function of , well described by a
third or fourth degree polynome. Taking this effect into account, the
TF scatter decreases by 20 percents, and the uncertainty in the
derived TF distances is reduced as well, while the correlation
coefficient increases from 0.67 to 0.84 (diameter relation). This
study is based on the statistical analysis of the KLUN (Kinematics of
the Local Universe) sample of 5271 spiral galaxies, both for diameter
and magnitude, direct and inverse TF relations. The absolute
calibration is performed using two sets of good cepheid distance
measurements: the first one, mostly from the HST programmes, relies on
distance moduli generally agreed in the literature, the second one is
a subset of objects whose cepheid distance moduli are derived from
geometrical distances measured by HIPPARCOS.
The mean surface brightness dependence is first revealed by the
inverse relations, and further studied in the direct way through the
normalized distance method whose principle was first set by Bottinelli
et al. (1986), and a refined form recently applied by Theureau et al.
(1997b). As a consequence of the smaller scatter of the resulting TF
relation, the extracted unbiased subsample is deeper and contains more
objects than in previous studies. The Hubble constant
may thus be estimated from the largest unbiased
sample of field galaxies ever used (577 objects reaching velocities as
large as 6000 km s^{-1}, using the diameter relation). We
obtain km s^{-1} Mpc^{-1} and
km s^{-1} Mpc^{-1} from HST and
HIPPARCOS calibrations respectively.
**Key words:** galaxies:
spiral
galaxies: distances and
redshifts
Cosmology: distance scale
© European Southern Observatory (ESO) 1998
Online publication: February 4, 1998
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