Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - MagneticYSOs (Interpreting Dust Polarization Maps to Characterize the Role of the Magnetic Field in Star Formation Processes)
Teaser
\"The MagneticYSOs project adresses the modern challenges in our quest to build a complete understanding of star and planet formation. More specifically, the role of magnetic fields in building the stars and planets that we observe in our own Galaxy.The interstellar medium...
Summary
\"The MagneticYSOs project adresses the modern challenges in our quest to build a complete understanding of star and planet formation. More specifically, the role of magnetic fields in building the stars and planets that we observe in our own Galaxy.
The interstellar medium, where stars are born, is permeated by large-scale magnetic fields. These magnetic fields were suggested to have a crucial role in supporting the high density gas against its own gravity, that ultimately triggers the formation of low mass stars as our own Sun.
Star formation models suggest that these magnetic fields could also significantly affect the motions in the star-forming cores, ultimately affecting the formation of the youngest circumstellar disks, and thus the formation of planets in these disks.
Unfortunately the magnetic field cannot be observed directly. In the presence of a magnetic field, however, the dust grains contained in an astrophysical object asee their long axes partially align perpendicularly to the magnetic field lines. Their radiation is then emitted in a preferred direction and the light emitted is then called \"\"polarized\"\". It is this polarized light which is widely used to trace magnetic fields in star-forming cores, however the validity of these observations to produce robust constraints on the role of magnetic fields while stars and planets form, remains yet very few tested.
The MagneticYSOs project aims at investigating novel approaches, combining unprecedented detailed analysis of complete set of observational constraints and their confrontation to comprehensive MHD simulations of protostellar collapse, to ultimately understand if magnetic fields can be characterized in the youngest cores that form stars, and the youngest disks that form planets.\"
Work performed
By exploring a sample of 16 of the youngest protostars in our Galaxy, thanks to the interferometric array of the Institute of millimetric radio astronomy (IRAM), we have shown that a majority of disks where planets will be formed are born much smaller than expected (Maury et al. 2019). The size of these disks around young stars, currently being formed, could be limited by the influence of the magnetic field, the effects of which have so far been underestimated.
The MAGNETICYSOs team has analyzed observations the polarized light (emission of light in a preferred direction) from dust continuum emission for a large sample of 12 of the youngest protostars, and shows that all these cores, progenitors of solar-type stars, are magnetized to some levels (Galametz et al. 2018).
Our team has also been able to show for the first time that the magnetic field plays a fundamental role in the collapse of protostars. Based on observations from the Atacama Large Millimeter Array (ALMA) in Chile, we measured the polarization of dust in the B335 protostar (Maury et al. 2018). This polarization, results from the alignment of the dust grains under the influence of the magnetic field. In B335, this influence is exerted on a very large area around the collapsing protostar. These observations have been compared to the expected output of MHD numerical simulations and provide the first proof that the influence of the magnetic field is preponderant in the process of formation of solar-type stars, and more specifically in the formation of future protoplanetary disks.
Final results
Our work has globally highlighted the cornerstone role of the magnetic field during the early phases of the star and disk formation, thanks to an unprecedented combination of observational data and physical models of the protostellar collapse.
Our work so far has been performed under the assumption that dust polarized emission is a good tracer of magnetic field structure in the conditions in which we seek for it: we are now exploring avenues to consolidate this hypothesis, by tackling issues related to the nature of the dust itself, and the interpretation of its polarized emission. Our new observations, and their comparison to our improved models of protostellar formation, should enable us to establish a robust and constraining methodology for the community to evaluate the magnetic field properties in large sample of solar-type star-forming cores.