Exploring the millimetre emission in nearby galaxies: analysis of the
  edge-on galaxy NGC 891
  New observations of the edge-on galaxy NGC 891, at 1.15 and 2 mm obtained
with the IRAM 30-m telescope and the NIKA2 camera, within the framework of the
IMEGIN (Interpreting the Millimetre Emission of Galaxies with IRAM and NIKA2)
Large Program, are presented in this work. By using multiwavelength maps (from
the mid-IR to the cm wavelengths) we perform SED fitting in order to extract
the physical properties of the galaxy on both global and local ($\sim$kpc)
scales. For the interpretation of the observations we make use of a
state-of-the-art SED fitting code, HerBIE (HiERarchical Bayesian Inference for
dust Emission). The observations indicate a galaxy morphology, at mm
wavelengths, similar to that of the cold dust emission traced by sub-mm
observations and to that of the molecular gas. The contribution of the radio
emission at the NIKA2 bands is very small (negligible at 1.15 mm and $\sim10\%$
at 2 mm) while it dominates the total energy budget at longer wavelengths
(beyond 5 mm). On local scales, the distribution of the free-free emission
resembles that of the dust thermal emission while the distribution of the
synchrotron emission shows a deficiency along the major axis of the disc of the
galaxy.
