2015MNRAS.453.2214M

By postulating that the majority of the mass and angular momentum of a disc galaxy is confined to the disc with a lognormal surface density distribution, and that galactic discs are substantially, if not fully, self-gravitating, it may be shown that the resultant rotation curves (RCs) display a good overall fit to observational data for a wide range of galaxy types. With this hypothesis, the total angular momentum J, and total energy {verbar}E{verbar} of 38 disc galaxies was computed and plotted against the derived disc masses, with best fit slopes for J of 1.683±0.018 and {verbar}E{verbar} of 1.643±0.038, and a universal disc spin parameter λ = 0.423±0.014. Using the disc parameters Vmax and Rmax as surrogates for the virial velocity and radius, a virial mass estimator M_disc ∝R_max V_max^2 was generated, with a log-log slope of 1.024±0.014 for the 38 galaxies, and a proportionality constant λ* = 1.47±0.20x10⁵M_☉kpc- 1km- 2s2. This relationship has less scatter than M∝(Vrot)α, and may provide an alternative to the Tully-Fisher relation in determining virial disc masses.