Planck intermediate results. XXIII. Galactic plane emission components
  derived from Planck with ancillary data
  Planck data when combined with ancillary data provide a unique opportunity to
separate the diffuse emission components of the inner Galaxy. The purpose of
the paper is to elucidate the morphology of the various emission components in
the strong star-formation region lying inside the solar radius and to clarify
the relationship between the various components. The region of the Galactic
plane covered is l=300-0-60deg where star-formation is highest and the emission
is strong enough to make meaningful component separation. The latitude widths
in this longitude range lie between 1deg and 2deg, which correspond to FWHM
z-widths of 100-200pc at a typical distance of 6kpc. The four emission
components studied here are synchrotron, free-free, anomalous microwave
emission (AME), and thermal (vibrational) dust emission. These components are
identified by constructing spectral energy distributions (SEDs) at positions
along the Galactic plane using the wide frequency coverage of Planck
(28.4-857GHz) in combination with low-frequency radio data at 0.408-2.3GHz plus
WMAP data at 23-94GHz, along with far-infrared (FIR) data from DIRBE and IRAS.
The free-free component is determined from radio recombination line (RRL) data.
AME is found to be comparable in brightness to the free-free emission on the
Galactic plane in the frequency range 20-40GHz with a width in latitude similar
to that of the thermal dust; it comprises 45+/-1% of the total 28.4GHz emission
in the longitude range l=300-0-60deg. The free-free component is the narrowest,
reflecting the fact that it is produced by current star-formation as traced by
the narrow distribution of OB stars. It is the dominant emission on the plane
between 60 and 100GHz. RRLs from this ionized gas are used to assess its
distance, leading to a free-free z-width of FWHM ~100pc...(abridged)
