  We report ALMA observations of dust continuum, 13CO J=3--2, and C18O J=3--2
line emission toward a gapped protoplanetary disk around HD 142527. The outer
horseshoe-shaped disk shows the strong azimuthal asymmetry in dust continuum
with the contrast of about 30 at 336 GHz between the northern peak and the
southwestern minimum. In addition, the maximum brightness temperature of 24 K
at its northern area is exceptionally high at 160 AU from a star. To evaluate
the surface density in this region, the grain temperature needs to be
constrained and was estimated from the optically thick 13CO J=3--2 emission.
The lower limit of the peak surface density was then calculated to be 28 g cm-2
by assuming a canonical gas-to-dust mass ratio of 100. This finding implies
that the region is locally too massive to withstand self-gravity since Toomre's
Q <~1--2, and thus, it may collapse into a gaseous protoplanet. Another
possibility is that the gas mass is low enough to be gravitationally stable and
only dust grains are accumulated. In this case, lower gas-to-dust ratio by at
least 1 order of magnitude is required, implying possible formation of a rocky
planetary core.
