We present, for five spiral galaxies, H i data which, along with the Ha rotation curves, are used to derive the distribution of dark matter within th

Aims. We derive the value of the dark matter density at the Sun’s location (ρ ⊙) without fully modeling the mass distribution in the Galaxy.Methods. The proposed method relies on the local equation of centrifugal equilibrium and is independent of i) the shape of the dark matter density profile, ii) knowledge of the rotation curve from the galaxy center out to the virial radius, and iii) the uncertainties and the non-uniqueness of the bulge/disk/dark halo mass decomposition.Results. The result can be obtained in analytic form, and it explicitly includes the dependence on the relevant observational quantities and takes their uncertainties into account. By adopting the reference, state-of-the-art values for these, we find ρ ⊙ = 0.43(11)(10) GeV/cm3, where the quoted uncertainties are respectively due to the uncertainty in the slope of the circular-velocity at the Sun location and the ratio between this radius and the length scale of the stellar exponential thin disk. Conclusions. We obtained a reliable estimate of ρ ⊙, that, in addition has the merit of being ready to take any future change/improvement into account in the measures of the observational quantities it depends on.

We establish the presence of a dark matter core radius, for the first time in a very large number of spiral galaxies of all luminosities. Contrary to common opinion we find that the sizes of these cores and the " DM core problem" are bigger for more massive spirals. As a result the Burkert profile provides an excellent mass model for dark halos around disk galaxies. Moreover, we find that the spiral dark matter core densities $\rho_{0}$ and core radii $r_{0}$ lie in the same scaling relation $\rho_{0}=4.5\times 10^-2 (r_{0}/kpc)^{-2/3} M_{\odot}pc^{-3}$ of dwarf galaxies with core radii upto ten times more smaller.Comment: 4 pages, 4 figures, Accepted for Publication in Apj Let