Angular momentum of disc galaxies with a lognormal density distribution

الأصل · EN

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 |E| 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 |E| 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 Mdisc∝RmaxVmax² was generated, with a log-log slope of 1.024±0.014 for the 38 galaxies, and a proportionality constant λ*=1.47±0.20×10⁵Mkpc⁻¹km⁻²s². This relationship has less scatter than M∝Vα, and may provide an alternative to the Tully-Fisher relation in determining virial disc masses.