Modelling the cold dust in nearby spiral galaxies with radiative transfer.

Cosmic dust grains are one of the fundamental ingredients of the interstellar medium (ISM). In spite of their small contribution to the total mass budget, dust grains play a significant role in the physical and chemical evolution of galaxies. Over the past decades, a plethora of multi-wavelength data, from UV to far-infrared, has increased substantially our knowledge on the dust properties of nearby galaxies. Nevertheless, one regime of the spectrum, the mm range, remains relatively unexplored. Thanks to the new, high-resolution data in the mm range observed with the NIKA2 instrument and our radiative transfer framework, we aim to firmly characterise the physical properties of the very cold dust (<15K), and to quantify the importance of different emission mechanisms in the mm. So far, we have developed a methodology to use dust radiative transfer modelling and applied it to a small group of face-on spiral galaxies. The combination of the new NIKA2 data with our radiative transfer techniques would provide the right conditions to generate an accurate model of the interplay between starlight and dust in a sizeable sample of spatially-resolved nearby galaxies.