Planck Early Results: Properties of the interstellar medium in the Galactic plane

(abridged) Planck has observed the entire sky from 30 GHz to 857GHz. The observed foreground emission contains contributions from different phases of the interstellar medium (ISM). We have separated the observed Galactic emission into the different gaseous components (atomic, molecular and ionised) as well as into a number of Galactocentric rings. Templates are created for various Galactocentric radii using velocity information from atomic (neutral hydrogen) and molecular (12CO) observations. The ionised template is assumed to be traced by free-free emission as observed by WMAP, and 408 MHz emission is used to trace the synchrotron component. Gas emission not traced by the above templates, namely dark gas, as evidenced using Planck data, is included as an additional template. These templates are then correlated with each of the Planck frequency bands, as well as with higher frequency data from IRAS and DIRBE along with radio data at 1.4GHz. The emission per column density of the gas templates allows us to create distinct spectral energy distributions (SEDs) per Galactocentric ring and in each of the gaseous tracers from 1.4GHz to 25 THz (12 {\mu}m). We find the dust opacity in the solar neighbourhood, \tau/NH = 0.92 +/- 0.05 \times 10^-25cm2 with no significant variation with Galactic radius even though the dust temperature is seen to vary from over 25K to under 14K. Furthermore, we show that anomalous dust emission is present in the atomic, molecular and dark gas phases throughout the Galactic disk. No anomalous emission is detected in the ionised phase where free-free emission is seen to dominate. For all environments, the anomalous emission is consistent with rotation from polycyclic aromatic hydrocarbons (PAHs) and, according to our simple model, accounts for 25 +/- 5%(stat.) of the total emission at 30 GHz.