Dark and Baryonic Matter in Bright Spiral Galaxies. II. Radial Distributions for 34 Galaxies

We decompose the rotation curves of 34 bright spiral galaxies into baryonicand dark matter components. Stellar mass profiles are created by applyingcolor-M/L relations to near-infrared and optical photometry. We find that theradial profile of the baryonic-to-dark-matter ratio is self-similar for allgalaxies, when scaled to the radius where the contribution of the baryonic massto the rotation curve equals that of the dark matter (R_X). We argue that thisis due to the quasi-exponential nature of disks and rotation curves that arenearly flat after an initial rise. The radius R_X is found to correlate moststrongly with baryonic rotation speed, such that galaxies with R_X measurementsthat lie further out in their disks rotate faster. This quantity alsocorrelates very strongly with stellar mass, Hubble type, and observed rotationspeed; B-band central surface brightness is less related to R_X than theseother galaxy properties. Most of the galaxies in our sample appear to be closeto maximal disk. For these galaxies, we find that maximum observed rotationspeeds are tightly correlated with maximum rotation speeds predicted from thebaryon distributions, such that one can create a Tully-Fisher relation based onsurface photometry and redshifts alone. Finally, we compare our data to the NFWparameterization for dark matter profiles with and without including adiabaticcontraction as it is most commonly implemented. Fits are generally poor, andall but 2 galaxies are better fit if adiabatic contraction is not performed. Inorder to have better fits, and especially to accommodate adiabatic contraction,baryons would need to contribute very little to the total mass in the innerparts of galaxies, seemingly in contrast with other observational constraints.Comment: 39 pages, accepted to Ap