A recent re-determination of the global Galactic emission
in the 20 keV - 8 MeV energy domain with the SPI telescope
on INTEGRAL observatory shows the transition from a source-dominated
to a diffuse-emission dominated sky.
It thus confirms that individual sources determine the observed emission
of the Galaxy between 20 keV and 200 keV, and that the positron-annihilation
emission dominates above 300 keV to peak with the bulge-dominated 511 keV
line emission.
However, with subtraction of these two components, residual diffuse emission
is detected, with a weak surface brightness but a broad spatial extent.
This additional, diffuse emission constitutes a significant fraction of
the total emission here, and plays the major part from 600 keV up to 2 MeV.
Its spatial distribution appears elongated along the plane of the Galaxy.
(Bouchet et al., 2008, accepted for publication in ApJ; astro-ph:0801.2086).
Upgraded theoretical models are now able to explain the observed continuum
in terms of interstellar processes, thus solving a long-standing mystery
of the origin of this emission.
