2014ApJ...784...26O

This work presents high-precision measurements of the specific baryon angular momentum j_b contained in stars, atomic gas, and molecular gas, out to ≳ 10 scale radii, in 16 nearby spiral galaxies of the THINGS sample. The accuracy of these measurements improves on existing studies by an order of magnitude, leading to the discovery of a strong correlation between the baryon mass M_b, j_b, and the bulge mass fraction β, fitted by β = -(0.34 ± 0.03)lg(j_bM_b^–1/[10^–7 kpc.km/s/M_☉]) - (0.04± 0.01) on the full sample range of 0 ≤ β ≲ 0.3 and 10⁹ M_☉< M_b< 10¹¹ M_☉. The corresponding relation for the stellar quantities M_*and j_*is identical within the uncertainties. These M-j-β relations likely originate from the proportionality between jM.^–1 and the surface density of the disk that dictates its stability against (pseudo-)bulge formation. Using a cold dark matter model, we can approximately explain classical scaling relations, such as the fundamental plane of spiral galaxies, the Tully-Fisher relation, and the mass-size relation, in terms of the M-j(-β) relation. These results advocate the use of mass and angular momentum as the most fundamental quantities of spiral galaxies.