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The MPIA conference series
at Ringberg Castle
The MPIA conference series
at Ringberg Castle
 
EPoS 2020 Suggested Contribution
Massive star formation with a new hybrid radiative transfer method

Raphael Mignon-Risse
AIM/CEA Saclay, Paris, FR
Massive stars (> 8 solar masses) still accrete when going onto the main-sequence, hence they start radiating, and at a much higher luminosity as their mass increases. In fact, in a first simple 1D approximation their radiative feedback can stop further accretion. Spherical symmetry has been broken in multidimensional simulations, and disk accretion (2D) then accretion via radiative Rayleigh-Taylor instabilities (3D), have emerged. Hence the radiation processes must be treated accurately. More specifically, the frequency-dependent nature of the radiation has to be captured because the opacity varies on orders of magnitude between the stellar photons and the medium photons, thus it strongly impacts its force and absorption by the surrounding gas. In my thesis, I have been coupling two radiative transfer moment methods in the RAMSES code: the first one is adapted to the direct stellar radiation (RAMSES-RT, M1) and the second one is a correct approximation for absorbed-and-reemitted radiation (Flux-Limited Diffusion). The hybrid approach brings big improvements for the gas temperature, the anisotropy of the radiation field and the radiative force, as I will show. I will present the impact of this approach on the collapse of an isolated massive prestellar core, and particularly the enhancement of radiative outflows. I will use a specific refinement strategy to observe the presence (or not) of Rayleigh-Taylor instabilities, and I will show how this result is of physical (and not numerical) origin. Finally, I will present preliminary outcomes when using this method together with ambipolar diffusion to investigate the origin (radiative and/or magnetic?) of outflows around massive protostars, in a turbulent environment.
Caption: Collapse calculations with the hybrid radiative transfer method. (a) Run without magnetic fields, density slice (disk seen edge-on). Radiative outflows are present, the cavity edges are refined to the finest resolution and there is no radiative Rayleigh-Taylor instability. (b) Run with ambipolar diffusion, volume rendering of the outflow and field lines around a 4 solar masses protostar. Magnetocentrifugal mechanism contributes to launching the outflow.
Collaborators:
M. Gonzalez, AIM, FR
B. Commercon, CRAL, FR
J. Rosdahl, CRAL, FR
Key publication

Suggested Session: High-Mass Star Formation