Journal Articles
The collapse of magnetized, rotating Bonnor--Ebert spheres with ambipolar diffusion in 3D
MNRAS (in prep), Duffin & Pudritz 2009.
The Early History of Protostellar Disks, Outflows, and Binary Stars
ApJ Letters (accepted), Duffin & Pudritz 2009 (astro-ph).
Abstract
In star formation, magnetic fields act as a cosmic angular momentum extractor which increases mass accretion rates onto protostars and, in the process, creates spectacular outflows. However, recently it has been argued that this magnetic brake is so strong that early protostellar disks -- the cradles of planet formation -- cannot form. Our three-dimensional numerical simulations of the early 10^5 yr) of overdense star--forming clouds form early out- stages of collapse (flows and have magnetically regulated and rotationally dominated disks (inside 10 AU) with high accretion rates, despite the slip of the field through the mostly neutral gas. We find that in three dimensions magnetic fields suppress gravitationally driven instabilities which would otherwise prevent young, well-ordered disks from forming. Our simulations have surprising consequences for the early formation of disks, their density and temperature structure, the mechanism and structure of early outflows, the flash heating of dust grains through ambipolar diffusion, and the origin of planets and binary stars.
Simulating hydromagnetic processes in star formation: introducing ambipolar diffusion into an adaptive mesh refinement code
MNRAS 391, 1659, Duffin & Pudritz 2008 (astro-ph)
Abstract
Given the importance of simulating hydromagnetic processes that impact star formation, we have earlier developed a 3D adaptive mesh approach that allows us to include hydromagnetic processes during the formation and evolution of cores, discs, and stars in observed regions of star formation. In this paper, we take the next step in this program - namely - to develop a modified version of the 3D adaptive mesh refinement (AMR) code FLASH in which the ambipolar diffusion of the magnetic field in poorly ionized molecular gas is implemented. We approach the problem using a single-fluid approximation to simplify numerical calculations. In this paper, we present a series of test cases including oblique isothermal and non--isothermal C-shocks. We also present a study of the quasi-static collapse of an initial uniform, self-gravitating, magnetized sphere that is initially supported by its magnetic field against collapse (i.e. magnetically subcritical). Applications to the collapse of a pre-stellar Bonnor-Ebert sphere are presented in a companion paper.
coolstuff
Tilted disk
This tilted disk is a snippet from a new paper we're preparing on early protostellar disk formation. In this Bonnor-Ebert sphere collapse, the magnetic field and axis of rotation were misaligned by 15 degrees, leading to a somewhat skewed disk. Grey contours are density, blue contours are temperature and red contours are outward velocity from the protostellar outflow. Yellow lines represent magnetic field lines.
latest news
12 October 2009
New astroph paper is out! Check it out
here.
19 October 2009
New website! Some actual structure!
key words
This tilted disk is a snippet from a new paper we're preparing on early protostellar disk formation. In this Bonnor-Ebert sphere collapse, the magnetic field and axis of rotation were misaligned by 15 degrees, leading to a somewhat skewed disk. Grey contours are density, blue contours are temperature and red contours are outward velocity from the protostellar outflow. Yellow lines represent magnetic field lines.
New astroph paper is out! Check it out here.
New website! Some actual structure!