The relation between bulge velocity dispersion and disk circular velocity in galaxies

We investigate the relation between the central velocity dispersion, σ_c, and the circular velocity, V_circ, in galaxies, which could be interpreted as a relation between the masses of central black holes and dark matter halos. We consider an observationally homogeneous sample of 52 high surface brightness (HSB) spiral galaxies and 11 low surface brightness (LSB) spiral galaxies in addition to HSB literature data. We performed a straight line regression analysis in a linear scale, finding a good fit, also for low σ_c galaxies, always rejected in the previous studies. LSB galaxies, for the first time considered for this purpose, seem to behave differently, showing either higher values of V_circ or lower values of σ_c with respect to their HSB counterparts.