GOALS

While it had been shown that magnetic fields are theoretically able to significantly contribute to solving the angular momentum problem for star formation, the physics at work to conserve or dissipate angular momentum during the main accretion phase – and therefore the processes allowing star, disk and planet formation – was still surprisingly poorly understood when the project was proposed for ERC funding in 2015. For example, the exact role of magnetic braking in regulating angular momentum during the early phases of star formation still had to be addressed observationally.

The MagneticYSOs project aimed at testing if magnetic fields are the missing piece allowing to solve the angular momentum problem during the Class 0 phase. This major leap forward has been made possible by our novel approach combining unprecedented detailed analysis of a complete set of observational constraints, and their confrontation to comprehensive MHD simulations of protostellar collapse.

• THE FOUR BONES OF MAGNETICYSOS

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    Observations of the protostellar gas and dust

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    Observations of B-fields properties

    
    

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    Comparison to MHD models

    
    

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    Radiative transfer and dust grains physics

    
    

MAGNETICYSOS MAIN CONTRIBUTIONS TO THE FIELD

MagneticYSOs has been a ground-breaking project, led between 2016 and 2022, which has allowed us to :
- interpret the polarized dust emission maps to infer the geometry and strength of the magnetic field,
- characterize magnetic diffusion processes to assess the efficiency of magnetic braking,
- compare the magnetic flux to the angular momentum content of the protostellar envelopes,
- confront this complete set of observational constraints to the predictions of magnetized collapse MHD models.

By thoroughly assessing the properties and roles of magnetic fields in the youngest protostars, we have been able not only to address and partially solve one of the oldest and most challenging question for our understanding of star formation, the angular momentum problem in star formation, but also to address other related astrophysical questions, eg:
- How efficient are the accretion/ejection processes, e.g. how is the prestellar core mass reservoir transforming into a young stellar object and its protoplanetary disk ?
- How are the magnetic and kinematical properties of the parent core transferred to the protostar, in particular which fraction of the magnetic flux and angular momentum is delivered to the protostar and how does it compare to the magnetism and rotation of young stars observed before they reach the main sequence ?
- What are the physical ingredients driving the formation of multiple stellar systems, circumstellar disks, and ultimately the initial conditions of planet formation in those disks?
- We also were able to propose an innovative approach using polarimetry and interferometric observations compared to MHD model, to characterize the properties of dust grains in protostellar environments, a key question for our understanding of early dust evolution towards planetesimals.