Saturday, February 18, 2017

Zoom-Simulations of Protoplanetary Disks starting from GMC scales


Kuffmeier et al


We investigate the formation of protoplanetary disks around nine solar mass stars formed in the context of a 40 pc Giant Molecular Cloud model, using \ramses \ adaptive-mesh resolution simulations extending over a scale range of about 4 million, from an outer scale of 40 pc to a smallest cell size of 2 AU. Our most important qualitative result is that the accretion process is heterogeneous in multiple ways; in time, in space, and among protostars of otherwise similar mass. Accretion is heterogeneous in time, in the sense that accretion rates vary in time, with generally decreasing profiles, whose slopes can vary over a wide range, and where accretion can increase again if a protostar enters a region with increased density and low speed. Accretion is heterogeneous in space, because of the distribution of mass in space, with mass approaching the accreting star and disk in filaments and sheets. Finally, accretion is heterogeneous among stars, since the detailed conditions and dynamics in the neighborhood of each star can vary widely. We investigate in particular the sensitivity of disk formation to physical conditions, such as mass-to-flux ratio, and to sink particle recipe parameters. We find that disks frequently form, even when choosing the least favorable sink particle parameters, and that turbulence carried along from larger scales is a main factor in allowing disks to form even when the magnetic field is comparatively strong.

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