The rotation curve (RC) of our Galaxy, the Milky Way, is constructed starting from its very inner regions (few hundred pc) out to a large galactocentric distance of ∼ 200 kpc using kinematical data on a variety of tracer objects moving in the gravitational potential of the Galaxy, without assuming any theoretical models of the visible and dark matter components of the Galaxy. We study the effect on the RC due to the uncertainties in the values of the Galactic Constants (GCs) R 0 and V 0 (these being the sun's distance from and circular rotation speed around the Galactic center, respectively) and the velocity anisotropy parameter β of the halo tracer objects used for deriving the RC at large galactocentric distances. The resulting RC in the disk region is found to depend significantly on the choice of the GCs, while the dominant uncertainty in the RC at large distances beyond the stellar disk comes from the uncertainty in the value of β. In general we find that the mean RC steadily declines at distances beyond ∼ 60 kpc, independently of the value of β. Also, at a given radius, the circular speed is lower for larger values of β (i.e., for more radially biased velocity anisotropy). Considering that the largest possible value of β is unity, which corresponds to stellar orbits being purely radial, our results for the case of β = 1 give a lower limit to the total mass of the Galaxy within ∼ 200 kpc, M (200 kpc) > ∼ (6.8 ± 4.1) × 10 11 M ⊙ , independently of any model of the dark matter halo of the Galaxy.

The velocity distribution function (VDF) of the hypothetical Weakly Interacting Massive Particles (WIMPs), currently the most favored candidate for the Dark Matter (DM) in the Galaxy, is determined directly from the circular speed ("rotation") curve data of the Galaxy assuming isotropic VDF. This is done by "inverting" -using Eddington's method -the Navarro-Frenk-White universal density profile of the DM halo of the Galaxy, the parameters of which are determined, by using Markov Chain Monte Carlo (MCMC) technique, from a recently compiled set of observational data on the Galaxy's rotation curve extended to distances well beyond the visible edge of the disk of the Galaxy. The derived most-likely local isotropic VDF strongly differs from the Maxwellian form assumed in the "Standard Halo Model" (SHM) customarily used in the analysis of the results of WIMP direct-detection experiments. A parametrized (non-Maxwellian) form of the derived mostlikely local VDF is given. The astrophysical "g-factor" that determines the effect of the WIMP VDF on the expected event rate in a direct-detection experiment can be lower for the derived most-likely VDF than that for the best Maxwellian fit to it by as much two orders of magnitude at the lowest WIMP mass threshold of a typical experiment.Several experiments worldwide are currently trying to directly detect the hypothetical Weakly Interacting Massive Particles (WIMPs), thought to constitute the Dark Matter (DM) halo of our Galaxy, by looking for nuclear recoil events due to scattering of WIMPs off nuclei of suitably chosen detector materials in low background underground facilities. The rate of nuclear recoil events depends crucially on the local (i.e., solar neighborhood) density and velocity distribution of the WIMPs in the Galaxy [1], which are a priori unknown. Estimates based on a variety of observational data typically yield values for the local density of DM, ρ DM,⊙ , in the range 0.2 -0.4 GeV cm −3 ((0.527 − 1.0) ×10 −2 M ⊙ pc −3 ) [2]. In contrast, not much knowledge directly based on observational data is available on the likely form of the velocity distribution function (VDF) of the WIMPs in the Galaxy. The standard practice is to use what is often referred to as the "Standard Halo Model" (SHM), in which the DM halo of the Galaxy is described as a single-component isothermal sphere [3], for which the VDF is assumed to be isotropic and of Maxwell-Boltzmann (hereafter simply "Maxwellian") form, f (v) ∝ exp(−|v| 2 / v 0 2 ), with a truncation at an assumed value of the local escape speed, and with v 0 = v c,⊙ , the circular rotation velocity at the location of the Sun. Apart from several theoretical issues (see, e.g., [4]) concerning the self-consistency of the SHM * pijush.bhattacharjee@saha.ac.in † soumini.chaudhury@saha.ac.in ‡ susmita.kundu@saha.ac.in § subha@tifr.res.in as a model of a finite-size, finite-mass DM halo of the Galaxy, high resolution cosmological simulations of DM halos [5] give strong indications of significant departure of the VDF from the Maxwellian...

Upper limits on the spin-independent (SI) as well as spin-dependent (SD) elastic scattering cross sections of low mass (∼ 2 -20 GeV) WIMPs (Weakly Interacting Massive Particles) with protons, imposed by the upper limit on the neutrino flux from WIMP annihilation in the Sun given by the Super-Kamiokande (S-K) experiment, and their compatibility with the "DAMA-compatible" regions of the WIMP parameter space -the regions of the WIMP mass versus cross section parameter space within which the annual modulation signal observed by the DAMA/LIBRA experiment is compatible with the null results of other direct detection experiments -are studied within the frame work of a self-consistent model of the finite-size dark matter (DM) halo of the Galaxy. The halo model includes the gravitational influence of the observed visible matter of the Galaxy on the phase space distribution function of the WIMPs constituting the Galaxy's DM halo in a self-consistent manner. Unlike in the "Standard Halo Model" (SHM) used in earlier analyses, the velocity distribution of the WIMPs in our model is non-Maxwellian, with a high-velocity cutoff determined self-consistently by the model itself. The parameters of the model are determined from a fit to the rotation curve data of the Galaxy. We find that, for our best fit halo model, for SI interaction, while the S-K upper limits do not place additional restrictions on the DAMA-compatible region of the WIMP parameter space if the WIMPs annihilate dominantly tob b and/orc c, portions of the DAMA-compatible region can be excluded if WIMP annihilations to τ + τ − and νν occur at larger than 35% and 0.4% levels, respectively. For SD interaction, on the other hand, the restrictions on the possible annihilation channels are much more stringent: they rule out the entire DAMA region if WIMPs annihilate to τ + τ − and νν final states at greater than ∼ 0.05% and 0.0005% levels, respectively, and/or tob b and c c at greater than ∼ 0.5% levels. The very latest results from the S-K Collaboration [T. Tanaka et al, Astrophys. J. 742:78 (2011)] make the above constraints on the branching fractions of various WIMP annihilation channels even more stringent by roughly a factor of 3-4. * susmita.kundu@saha.ac.in † pijush.bhattacharjee@saha.ac.in