Tight Constraint on Local Dark Matter Density from a Joint Analysis of Local Kinematics and Rotation Curves

Dark Matter (DM) particles, by their definition, are very weakly interacting and cannot be seen.
They make their presence felt primarily through gravity. In particular, in the Milky Way (MW),
we estimate the distribution of DM (and its velocities) by using visible matter tracers (like lu-
minous compact old stars, extended mass like globular clusters, pulsating variable stars etc.) to
construct rotation curves and mass of Halo. These rotation curves are also dependent on absolute
normalisation given by the Local Standard of Rest (LSR) whose values are again dependent on
visible matter tracers. Moreover, the gravitational potential in which the tracers move depend on
both the distributions of dark and visible matter which are difficult to disentangle. We show that
choice of the LSR, the final rotation curve made out of binning and averaging of individual tracer
velocities as well as any prior on the visible matter distribution crucially influences the estimate
of the DM density. This results in the wide range of values for the local DM density (as diverse
as 0.1 − 0.9GeVcm−3, but with small error bars) quoted in the literature. Precise knowledge of
the distribution of ‘visible’ matter by the ongoing GAIA DR3 survey and the futuristic THEIA
mission is, therefore, of paramount importance in our understanding of DM. We have also analyzed
Mass distribution of our galaxy following NFW profile. This is especially important when using the
astrophysical inferences about DM as inputs in particle DM experiments