The millimetre part of the spectrum is one of the least explored parts of a galaxy’s spectral energy distribution (SED), yet it contains emissions from three fundamentally important physical processes. These processes are thermal emission from dust, free-free emission from ionized gas and synchrotron emission from relativistic charged particles moving in the galactic magnetic field. The NIKA2 camera (IRAM-30m telescope), observing at 1.15 mm and 2 mm, provides additional data points for input into the comprehensive SED models and allows us to:

1. disentangle spatially resolved galaxy SEDs from dust contribution, free-free and synchrotron emission;
2. constrain the evolution of the dust-to-gas mass ratio within galaxies, which provides a direct link to the chemical evolution of galaxies and the reservoirs for dust production;
3. study the microscopic properties of dust, i.e. constraints on millimetric opacity;
4. study the sub-millimetre excess in galaxies, whose origin is still unknown.

These are some of the main objectives of the IMEGIN Large Program (Interpreting the Millimetre Emission of Galaxies with IRAM-NIKA2; PI S. Madden), targeting 22 nearby galaxies in the millimetre continuum regime with the NIKA2 camera. The millimetre data, combined with a suite of observations at other wavelengths, allow us to model the IR-to-radio SED and to put constraints on interstellar medium and dust grains properties of galaxies. We perform the galaxy SED analysis using the hierarchical bayesian fitting code HerBIE (Galliano et al. 2018), which includes the prescriptions from the dust evolution model THEMIS (Jones et al. 2017), anchored to the laboratory-measured properties of inter-stellar dust analogues.

During my presentation, I will focus on the major challenges linked with data processing, uncertainty propagation, and large-scale emission filtering in NIKA2 maps (due to atmosphere removal during the data reduction process). I will show and discuss the latest significant results on NGC891 (Katsioli et al. 2023); NGC4254 (Pantoni et al. in prep.); NGC2976 and NGC2146 (Ejlali et al. in prep.); millimetre morphology (Nersesian et al. in prep.); future perspectives/applications.

Local contact : Thierry FOGLIZZO

Organisateur : Frédéric GALLIANO