  The ionized core in the Sgr B2 Main star-forming region was imaged using the
Submillimeter Array archival data observed for the H26$\alpha$ line and
continuum emission at 0.86 millimeter with an angular resolution 0.3\arcsec.
Eight hyper-compact H26$\alpha$ emission sources were detected with a typical
size in the range of 1.6--20$\times10^2$ AU and electron density of
0.3--3$\times10^7$ cm$^{-3}$, corresponding to the emission measure
0.4--8.4$\times10^{10}$ cm$^{-6}$ pc. The H26$\alpha$ line fluxes from the
eight hyper-compact HII sources imply that the ionization for each of the
sources must be powered by a Lyman continuum flux from an O star or a cluster
of B stars. The most luminous H26$\alpha$ source among the eight detected
requires an O6 star that appears to be embedded in the ultra-compact HII region
F3. In addition, $\sim$ 23 compact continuum emission sources were also
detected within the central 5\arcsec$\times$3\arcsec\,($\sim0.2$ pc) region. In
the assumption of a power-law distribution for the dust temperature, with the
observed brightness temperature of the dust emission we determined the physical
properties of the submillimeter emission sources showing that the molecular
densities are in the range of 1--10$\times10^8$ cm$^{-3}$, surface densities
between 13 to 150 $g$ cm$^{-2}$, and total gas masses in the range from 5 to
$\gtrsim$ 200 $M_\odot$ which are 1 or 2 orders of magnitude greater than the
corresponding values of the Bonnor-Ebert mass. With a mean free-fall time scale
of 2$\times10^3$ y, each of the massive protostellar cores are undergoing
gravitational collapse to form new massive stars in the Sgr B2 Main core.
