log $h_{75}$.

We show in Fig. 4 the T-F relation in the $B$ band for the Hickson compact group galaxies, for the Sb and Sc galaxies in the lower density environments studied by Courteau (1997), and for Sb-Sd galaxies in the Ursa Major cluster studied by Verheijen (2001). The $R$ magnitudes given in Courteau (1996) were transformed to the $B$ magnitudes using the observational relation between morphological type index and the $B-R$ colors (de Jong 1996). The solid line in Fig. 4 represents a linear-squares fit to the Courteau’s data (M$_B$ = –7.05 log (V$_{max}$) – 4.57). The broken lines indicate the $\pm$ one sigma dispersion (rms=0.63) for their data. The dispersion for the HCG galaxies around the solid line is rms=0.82 for the whole sample of 25 galaxies and rms=0.65 (similar to that for the control sample of Courteau 1997) if the outliers HCG 89d, 91c, 96c, 96d are not considered (see section 5.1 for the discussion why these galaxies could have a peculiar location in the T-F relation). The sample of Verheijen (2001) for the Ursa Major cluster spirals presents a [*smaller*]{} dispersion around the solid line of rms=0.43, as expected for [*cluster*]{} galaxies.

Our main result is 