Talk abstract

It is established that both radiative transfer and magnetic field have a strong impact on the collapse and the fragmentation of prestellar dense cores. We perform the first Radiation-Magneto-HydroDynamics (RMHD) numerical calculations at a prestellar core scale. I will first briefly discuss the RMHD solver we designed in the RAMSES code. Then I will present original AMR calculations including magnetic field (in the ideal MHD limit) and radiative transfer, within the Flux Limited Diffusion (FLD) approximation, of the collapse of a 1 solar mass dense core. We compare the results with calculations performed with a barotropic EOS. We show that radiative transfer has an important impact on the collapse and the fragmentation, through the cooling or heating of the gas, and is complementary of the magnetic field. A larger field yields a stronger magnetic braking, increasing the accretion rate and thus the effect of the radiative feedback. Even for a strongly magnetized core, where the dynamics of the collapse is dominated by the magnetic field, radiative transfer is crucial to determine the temperature and optical depth distributions, two potentially accessible observational diagnostics. A barotropic EOS cannot account for realistic fragmentation. The diffusivity of the numerical scheme, however, is found to strongly affect the output of the collapse, leading eventually to spurious fragmentation. Finally, I will investigate the effect of the initial angle between magnetic fields and the rotational axis. I will discuss the formation of a disk and present synthetic observational maps of the dust continuum emission (as seen with ALMA) and spectral energy distributions.