The Baryonic Tully-Fisher relation revisited

Geneva Observatory, University of Geneva, 1290 Sauverny, Switzerland e-mail: yves.revaz@obs.unige.ch

Received: 14 July 2004
Accepted: 11 September 2004

Abstract

The Baryonic Tully-Fisher relation (BTF) can be substantially improved when considering that the galactic baryonic mass is likely to consist not only of the detected baryons, stars and gas, but also of a dark baryonic component proportional to the HI gas. The BTF relation is optimally improved when the HI mass is multiplied by a factor of about 3, but larger factors up to still improve the fit over the original one using only the detected baryons. The strength of this improved relation is quantified with up-to-date statistical tests such as the Akaike Information Criterion or the Bayesian Information Criterion. In particular they allow us to show that supposing a variable ratio instead is much less significant. This result reinforces the suggestion made in several recent works that mass within galactic disks must be a multiple of the HI mass, and that galactic disks are substantially, but not necessarily fully, self-gravitating.