8. Discussion and conclusions
In the present paper we have shown that there is a type dependence in the zero-points of the diameter and also B - magnitude TF-relations. The new knowledge of the zero-point differences will have direct impact on our future attempt to use the TF-relation in the study of the kinematics of the local galaxy universe. The type dependences in both the diameter and magnitude relations were shown to be expected from simple disc + bulge + dark halo models, where the de Vaucouleurs disc determines the photometric diameter. This discussion of the origin of the type dependence should form a useful starting point for more detailed investigations of such models, including the fraction of dark mass needed, using large galaxy samples and the TF-relations. It is also clear that improved knowledge of the total gas fractions is important for the present kind of analysis of the dark mass fraction within the radius that usual TF-relations refer to. Our present calculations gave for values in the range 0.5-0.8 .
A concise summary of the main conclusions:
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998