Orateur
Description
High resolution observations of nearby galaxies at mm wavelengths allow us to study emission from interstellar medium in great detail. In the framework of the IMEGIN Large program, the NIKA2 camera on the IRAM 30-m telescope is used to map 22 nearby galaxies at 1.15 and 2 mm and at resolutions of 11.1" and 17.6", respectively. At these wavelengths we are able to trace the emission from very cold dust (< 15 K) as well as additional emission from Bremsstrahlung and synchrotron radiation. In our pilot study, NIKA2 observations of the edge-on galaxy NGC 891 are combined with observations at other wavelengths to examine the physical properties of this galaxy using the HerBIE SED fitting code. Our analyses indicate an excess of cold dust emission towards the outer parts of the galactic disk. Furthermore, emission originating from warm dust in compact HII regions is only detected at mid-IR wavelengths with, practically, no emission at submm/mm wavelengths. However, emission from the dust in the spiral arms is measured at all wavelengths from mid-IR to mm wavelengths. The SED fitting modelling provides the fraction of the mass of the small (< 15 Å) dust grains to the total dust mass which, for NGC 891, is found to be 9.5%, on average, but it increases, up to $\sim20$% at large distances (|z| > 3 kpc) beyond the galactic plane and in dense environments in the disk. Finally decomposing the mm/cm wavelength range into dust, free-free, and synchrotron emission we detect enhanced free-free emission at the regions where dust concentrations exist along the plane of the disk.
