We present our recent measurement of the kinematics of the Milky Way stellar halo (Light Side) and the derived mass of the dark matter halo (Dark Side) using the Jeans analysis. A tangential dip in the velocity anisotropy profile at r ~ 17 kpc (Kafle et al. 2012), and a distinct difference of ~65 kms−1 in the mean azimuthal velocity and the r.m.s dispersion of the most metal-rich and the metal-poor Blue Horizontal Branch stars we find (Kafle et al. 2013) are reported. The implications of this on the current controversial issue of an existence of the two-components in the halo are also discussed.

Aided with the kinematic measurements of the light side, we demonstrate how we infer the dynamical property of the dark side. Considering a realistic three component galaxy model (Hernquist bulge, Miyamoto-Nagai disk and NFW halo), we estimate the virial mass of the Galaxy to be Mvir = 1.2+0.5−0.4 × 1012M⊙ (Kafle et al. 2012). We also show that the rotation curve of the Galaxy has undulations similar to what have also been seen in the studies of the HI gas (Sofue et al. 2009).

I discuss a search for red giant stars in the Galactic halo with light-element abundances similar to second-generation globular cluster stars, and discuss the implications of such a population for globular cluster formation models and the balance between in situ star formation and accretion for the assembly of the Galactic halo.

We have been determining abundances of Th, Pb and other neutron-capture elements in metal-deficient cool giant stars to constrain the enrichment of heavy elements by the r- and s-processes. Our current sample covers the metallicity range between [Fe/H] = −2.5 and −1.0. (1) The abundance ratios of Pb/Fe and Pb/Eu of most of our stars are approximately constant, and no increase of these ratios with increasing metallicity is found. This result suggests that the Pb abundances of our sample are determined by the r-process with no or little contribution of the s-process. (2) The Th/Eu abundance ratios of our sample show no significant scatter, and the average is lower by 0.2 dex in the logarithmic scale than the solar-system value. This result indicates that the actinides production by the r-process does not show large dispersion, even though r-process models suggest high sensitivity of the actinides production to the nucleosynthesis environment.