A magnetized scenario for the birth of solar-type stars and protoplanetary disks : observations and models

Séminaire IPAG de Anaëlle Maury (CEA Saclay), jeudi 8 avril 2021, 11h00, IPAG seminar room

Understanding the first steps in the formation of stars and protoplanetary disks is a great unsolved problem of modern astrophysics. The key to make progress on this topic is to confront theoretical models and high-resolution studies of the youngest protostars, observed less than 0.1 Myrs after the onset of protostellar formation.
I will present some investigations of solar-type Class 0 protostars that we carried out in the framework of the CALYPSO and MagneticYSOs projects.
Starting from our early results suggesting that the youngest protostellar disks are found to be much smaller than the centrifugal radii expected from simple hydrodynamical models of protostellar formation, I will describe how some of our recent analysis of molecular line emission observed with ALMA and IRAM telescopes, as well as new numerical models, question the widely-accepted paradigm that conservation of the angular momentum associated to rotational motions in cores is responsible for the formation of protostellar disks.
I will discuss how our observations of magnetic fields in protostellar environments may reconcile the disk sizes and envelope kinematics in a scenario of magnetically regulated protostellar accretion and protoplanetary disk formation.
Finally, I will present the new results of an extensive analysis to characterize the fidelity of dust polarized emission to map protostellar magnetic fields, and will show how polarized dust emission can inform us on the dust properties in the disk-forming material around young protostars. Confronting our observations against synthetic observations of protostellar MHD models, we are able to show that large (>10 -100 microns) dust grains should already be formed in pristine protostellar envelopes to (i) produce polarized dust emission at levels similar to those currently observed in at (submillimeter wavelengths, and (ii) explain the variations of dust emissivity observed in a large sample of protostellar envelopes.