Dark Matter in the Central Region of NGC 3256
  We investigated the central mass distribution of the luminous infrared galaxy
NGC 3256 at a distance of 35 Mpc by using CO(1-0) observations of the Atacama
Large Millimeter and sub-millimeter Array (ALMA) and near-IR data of the Two
Micron Sky Survey (2MASS). We found that there is a huge amount of invisible
dynamical mass ($4.84 \times 10^{10} M_{\odot}$) in the central region of the
galaxy. The invisible mass is likely caused by some dark matter, which might
have a cuspy dark matter profile. We note that this dark matter is difficult to
explain with the conventional Modified Newtonian Dynamics (MOND) model, which
is only applicable at a low acceleration regime, whereas the acceleration at
the central region of the galaxy is relatively strong. Therefore, this
discovery might pose a challenge to the conventional MOND models.
