PRIMA to test dust alignment theories and measure the properties of dust grains in the dense ISM and star-forming cores

Abstract

Dust plays a key role in the chemistry and the physics of the interstellar medium (ISM) , yet its composition and growth during early star formation remain poorly constrained. Observing the total and polarized submm dust emission, Planck, BLASTPOL and ALMA have shown that the standard dust models clearly need to be revised. Further multi-wavelength observations are crucial to sample the polarized spectral energy distribution (SED) in the Wien regime (in the short- wavelength spectrum for the thermal emission from objects) where dust models can be efficiently discriminated, providing key insights on the dust properties and dust evolution and alignment processes, from the irradiated regions of the ISM to planet-forming disk scales. We propose to use PRIMAger to sample polarized dust emission in both diffuse and dense protostellar environments, testing dust alignment models and constraining grain sizes at the onset of star and planet formation. PRIMAger will allow us to get access to local variations of the total and polarized SED, which can now be confronted against predictions from synthetic observations produced from state-of-the-art MHD models combined with radiative transfer models, to solve some long-standing issues regarding the nature and evolution of dust grains in the ISM and in star-forming cores.