The total mass and dark halo properties of the Small Magellanic Cloud

We discuss the total mass and dark halo properties of the Small Magellanic Cloud (SMC) for reasonable V-band stellar-to-mass-to-light ratios (M(s)/L(V)) based on the high-resolution neutral hydrogen (H I) observations of the SMC. We adopt both the Burkert and the Navarro-Frenk-White (NFW) profiles for the dark matter halo of the SMC in order to model the radial profile of the observed rotation curve. We show that the mass (M(dm)) and the mean density (rho(dm)) of the dark matter halo within the optical radius (similar to 3 kpc) of the SMC can be significantly low for M(s)/L(V) = 2-4 reasonable for a galaxy dominated by older stellar populations. For example, the estimated M(dm) and rho(dm) are 7.5 x 10(7) M(circle dot) and 6.7 x 10(-4) M(circle dot) pc(-3), respectively, for M(s)/L(V) = 3.8. The models with lower M(s)/L(V) (1.0) can show higher M(dm) and rho(dm) yet have difficulties in reproducing the inner rotation curve profile for both the Burkert and the NFW profiles. The Burkert profile with a larger core radius (>1 kpc) (thus a low density) and a large mass (M (dm) > 3 x 10(9) M(circle dot)) can be better fit to the observed slowly rising rotation curve than the NFW one for a reasonable M(s)/L(V) similar to 2. This means that most of the dark halo mass can be initially located outside the optical radius in the SMC and thus that the dark halo would have already lost a significant fraction of its original mass due to the strong tidal interactions with the Galaxy and possibly with the Large Magellanic Cloud. We suggest that the dark mater halo of the SMC is likely to have the initial total mass and core radius as large as, or larger than, 6.5 x 10(9) M(circle dot) and 3.2 kpc, respectively. We discuss limitations of the present model in estimating the total mass of the SMC.