rotation curves of the Galaxy for three dark halo models: isothermal, Burkert and NFW dark halo models, by solid lines from top to bottom at $R=30$ kpc. Lower curves show rotation velocities due to dark halos alone, and upper curves are for those including the bulge and disk. The inner and outer dashed lines are for the bulge and disk components, respectively. []{data-label="fig-rcmodels"}](fig-mass.eps "fig:"){width="8cm"}\

![Schematic rotation curves of the Galaxy for three dark halo models: isothermal, Burkert and NFW dark halo models, by solid lines from top to bottom at $R=30$ kpc. Lower curves show rotation velocities due to dark halos alone, and upper curves are for those including the bulge and disk. The inner and outer dashed lines are for the bulge and disk components, respectively. []{data-label="fig-rcmodels"}](fig-rcmodel15.eps "fig:"){width="8cm"}\

According to Sofue et al. (2008), we assume that the Galaxy is composed of three mass components: a bulge, disk and dark halo. The surface mass distribution of a galactic bulge is expressed by the de Vaucouleurs (1958) law, which is decomposed into the volume density distribution for calculating the circular rotational velocity. The surface mass distribution of the disk is given by a thin exponential disk, and the rotation velocity 