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| EPoS Contribution |
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Multi-Physics Feedback Zoom-in Simulations with Realistic Initial Conditions of the Formation of Star Clusters: From Large Scale Magnetized Clouds to Turbulent Clumps to Cores to Stars
Richard Klein UC Berkeley and LLNL, Berkeley, US | |
| At present there have been a few radiation-hydrodynamic simulations, that are capable of reproducing the observed IMF over a ~ 2 decade range in stellar masses. In addition to reproducing the IMF without a prescribed equation of state, these simulations also reproduce a number of other properties of observed young star systems, such as the mass-dependent fraction of stars in binary and multiple systems. However, all simulations of the IMF to date rely on highly-idealized initial conditions (IC's). Existing simulations typically begin with a gas clump density and radius comparable to the typical densities and sizes of nearby newborn star clusters. Current approaches, however, do not properly capture the density and velocity structure that would result from the formation of such a protocluster gas clump within a GMC, during which energy and mass are continually accreted from larger scales - perhaps often along a filament. To address this crucial challenge to the development of a predictive theory of star formation, we will present new simulations of the formation of star clusters starting with turbulence driven on the larger scales of small GMC's and evolving to the formation of turbulent clumps down to molecular cores and to stars that include the fully coupled effects of magnetic fields, protostellar outflows, and radiation transport. To achieve the large dynamical range required, including the multi-physics effects of magnetic fields and the coupled feedback from protostellar outflows, radiative heating and radiation pressure, we employ new zoom-in AMR simulations with our multi-physics AMR code ORION, of selected regions within our new large-scale turbulent MHD simulations of the formation of IRDCs. In the talk I will discuss the different stages of the zoom-in simulations at different scales leading to star formation within these large clouds beginning with the properties and formation of extended massive braided filamentary dark clouds (Figure a, b) with density profile similar to observations. Disk-like cores in Keplerian rotation are formed along the massive filaments (Figure c). I will then discuss and compare the properties of our turbulent clumps with observations of cloud clumps with Zeeman magnetic field measurements. I show that the magnetic properties of the cloud clumps from our simulations match very well with the observations, including the formation of a power law relation between magnetic field strength |B| and volume density n(H) with the power index α very close to the value of 0.65 deduced from a Bayesian analysis of observed cloud clumps as well as the probability distribution function of the observed B/n(H)α. These strong field AMR simulations provide us self-consistent and realistic turbulence ICs of magnetized filamentary molecular clouds for high-resolution zoom-in star cluster formation simulations with radiation feedback and outflows after dense clump cores are formed inside the clouds. Upon collapse of the dense clumps, we perform the next stage of AMR zoom-in simulations on a small segment of the long dark filament. The size of the zoom-in region is large enough for the study of the effects of the radiation and outflow feedback from newly forming young stars (Figure d) and clusters on the dense surrounding molecular cloud environment. I will contrast the formation and feedback effects of these clusters formed with realistic initial conditions with our recent star cluster formation simulations in turbulent magnetized dense clumps performed on a much smaller scale, that were the first to include radiative and outflow feedback. Finally, I will discuss the effect of realistic initial conditions on the formation of the resultant IMF from these large to small-scale simulations. | |
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| Caption: Multi-stage zoom-in simulations from small scale GMC to star formation with feedback. (a) shows a density volume rendering of gas filaments formed in an infrared dark cloud (IRDC) MHD AMR simulation of 3120 solar masses, 800,000 years after the region began gravitational collapse. The main filament depicted between the 2 arrows is ~ 4.5 parsecs in length and 660 solar masses. (b) shows the main filament between the 2 arrows that is studied by further zoom-in simulation. (c) shows an expanded portion of the IRDC selected region of the filament in (b) and the streamlines of the magnetic field piercing through the IRDC with the red color patches representing the dense cores that are forming. The arrow shows the clump/core region to be studied by further zoom-in simulation. (d) shows a density volume rendering of the collapse of an isolated magnetized supersonic core 20,000 years after the formation of a high mass protostar, The turbulent core is representative of the dense cores formed in the vicinity of the arrow in (c). A powerful outflow is ejected from the central 25 solar mass star as shown by the red bipolar structure which represents gas moving outward faster than 10 km/sec. | |
| Collaborators: P.S. Li, UC Berkeley, US C. F. McKee, UC Berkeley, US A. Myers, UC Berkeley, US |
Key publication
Suggested Sessions: Filaments |