CONERTO probed the long-wavelength emissivity of dust in the Milky Way ISM, constraining how dust properties vary across different environments. The physical properties inferred from dust emission observations (mass, temperature) strongly depend on assumptions about dust emissivity, which is known to vary with environment. CONCERTO at APEX provided a unique opportunity to constrain dust properties in the (sub-)millimeter wavelength domain.

Dust emissivity depends on chemical composition and size distribution, which are poorly constrained. Grain sizes play an important role in determining the available area for grain surface chemistry and electron recombination, influencing the ionisation fraction and coupling to the magnetic field. In dense inner regions, dust grain sizes are expected to increase due to coagulation and ice mantle formation. In outer, less dense regions, no ice mantles coat the grains and their optical properties and sizes differ. By mapping nearby and galactic plane star-forming regions with CONCERTO, as well as diffuse high Galactic latitude clouds, it was possible to constrain variations of the dust emissivity in a broad range of environments, giving important input to Galactic dust models.

Despite the tremendous impact of massive stars on the ISM, no consensus has been reached on their formation mechanism. Numerical and observational studies suggested that, as a result of global cloud collapse, massive stars may accrete gas from a much larger mass reservoir than their low-mass counterparts. Characterising the transition from core-fed to cloud-fed star formation is key for understanding the star formation process. CONCERTO observations of a large area of the galactic plane allowed both determining the frequency and maximum mass of starless dense cores, and better characterising the variations of cloud density structure across the core-fed/cloud-fed transition. Being sensitive to the CO(3-2) line, such observations also separated the dust continuum emission from the CO(3-2) emission in the ATLASGAL 850 μm survey.