Impact of B field in building clouds filaments and their hosted high-mass stars
Star formation is a key process in astrophysics. At large scale, it regulates the energy budget of galaxies (especially massive stars) while at a small scale it sets the initial conditions for planet formation. It has been shown that the formation of stars, and the nature of the stars that will be formed, is very sensitive to the physical conditions at the cloud scale. Hence, star formation is a multi-scale process, whose comprehension requires a global view from the molecular cloud scale (tens of parsec) down to the accretion onto the proto-stellar embryo (a few au). The theoretical and numerical models that best reproduce the observational constraints (mass segregation and gas dynamics) all stand on the play of the magnetic field. Indeed magnetic fields were put forward to explain for the formation of filamentary structures, for the fragmentation of these structures into cores, for the collapse of these cores (magnetic braking), or for the accretion processes in the disks. To put observational constraints on these processes the community needs performant instruments to measure the magnetic fields: SPICA/B-BOP to study the largest scales, IRAM/NIKA2-POL to study the intermediate scales - from the molecular clouds down to the cores - and ALMA/NOEMA-POL to study the smallest scales (cf the Figure hereinafter). Getting the intermediate-scale magnetic field with NIKA2-POL is crucial to determine if small-scale magnetic fields are inherited from the larger scales, and build a coherent view of the effect of the magnetic fields for all processes of star formation. I will present new ALMA data and projects with NIKA2-POL in the framework of high-mass star formation.