CONSTRAINTS ON THE DECOMPOSITION OF THE ROTATION CURVES OF SPIRAL GALAXIES

I discuss anew how arguments about the internal dynamics of galactic disks set constraints on the otherwise ambiguous decomposition of the rotation curves of spiral galaxies into the contributions by the various constituents of the galaxies. Analyzing the two sample galaxies NGC3198 and NGC2985 I conclude from the multiplicities of the spiral arms and the values of the Q disk stability parameters that the disks of both galaxies are ‘maximum disks’.