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

In Webseminar by admin

Wednesday 8 July 2020 11AMAnaëlle Maury (CEA-Saclay & Harvard-Smithsonian CfA)
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 the recent work carried in the MagneticYSOs team, starting from our earlier results suggesting that >75% of the youngest protostellar disks are only found at very small radii <60 au (Maury+ 2019). I will also describe our kinematic analysis of envelope rotation (Gaudel+ 2020), which conservation of angular momentum is traditionally blamed for the formation of disks, and present how these observations and new numerical models (Verliat+ 2020) question this well-established paradigm.  I will discuss how these observations, coupled to our detection of magnetic fields (Maury+ 2018, Galametz+ 2018, Le Gouellec+ 2019, Galametz+ sub.) favor a scenario of magnetically regulated protostellar disk formation.
Finally, since magnetic fields are routinely mapped thanks to dust polarized emission, we have also investigated the dust properties in young protostars to shed light on the mechanisms responsible for the polarization (Guillet et al. 2020, Le Gouellec et al. sub.). Confronting our observations against synthetic observations of protostellar MHD models, we were able to show that large (>10 -100 microns) dust grains are required to (i) produce polarized dust emission at levels similar to those currently observed in solar-type protostars at millimeter wavelengths (Valdivia+ 2019), and (ii) explain the variations of dust emissivity observed in protostellar envelopes (Galametz+ 2019).