The peculiar dip in the outer rotation curve at a distance of 9 kpc , which was recently confirmed by precise measurements with the VERA VLBI array in Japan , suggests donut-like substructures in the dark matter ( DM ) halo , since spherical or elliptical distributions will not cause a dip .
Additionally , such a donut-like DM structure seems to be required by the dip in the gas flaring of the disk .
In this paper we consider the impact of such DM substructure in the disk on the rotation curve , the gas flaring , the local DM density and the local surface density .
A global fit shows that the rotation curve is best described by an NFW DM profile complemented by two donut-like DM substructures at radii of 4.2 and 12.4 kpc , which coincide with the local dust ring and the Monocerus ring of stars , respectively .
Both regions have been suggested as regions with tidal streams from ” shredded ” satellites , thus enhancing the plausibility for additional DM .
If real , the radial extensions of these nearby ringlike structures enhance the local dark matter density by a factor of four to about 1.3 \pm 0.3 GeV/cm ^ { 3 } .
We find that i ) this higher DM density is perfectly consistent with the local gravitational potential determining the surface density and ii ) the s-shaped gas flaring is explained .
Such a possible enhancement of the local DM density is of great interest for direct DM searches and the ringlike structure would change the directional dependence of gamma rays for indirect DM searches .