Abstract
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 spatiallyresolved nearby galaxies.
Highlights
Galaxies are complex structures of multiple components: dark matter, stars, interstellar gas and dust
Viaene et al [14] demonstrated that the active galactic nucleus (AGN) in NGC 1068 (M 77) is only important to dust heating within the inner few hundred parsecs from the centre of the galaxy, while most of the FIR emission is powered by star formation
The authors found that for the combined M 51 system, on average, 5.8% of the dust emission is attributed to the dust heating by the old stellar population of M 51b, of which 4.8% occurs in the M 51a subsystem; 23% of the dust heating is supplied by the old stellar population of M 51a, while the remaining 71.2% arises from the heating by the young stellar populations
Summary
Galaxies are complex structures of multiple components: dark matter, stars, interstellar gas and dust. Dust grains are carbonaceous or silicate based particles in the interstellar medium (ISM) of galaxies, and are responsible for the attenuation and reddening effects at ultraviolet (UV) and optical wavelengths. The role of dust does not stop there, since it is involved in several physical and chemical processes, by catalysing the formation of molecular hydrogen, and regulating the heating or cooling of the interstellar gas. The emission in that wavelength regime is often associated and used as a tracer of the star-formation activity in galaxies [5,6,7]. The contribution of stars of age greater than 8 Gyr to the dust heating can be non-negligible [e.g. 8, 9] and needs to be considered while estimating the rate which galaxies form their stars
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