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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 [FORMULA] of galaxies. It is shown that the zero-point of the relation is a continuous function of [FORMULA], 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 [FORMULA] 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 [FORMULA] km s-1 Mpc-1 and [FORMULA] 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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