Oral Presentation
Polarized dust emission in Young Stellar Objects. Observational and Theoretical approaches.
Presenter: Valeska Valdivia (Département d'Astrophysique/CEA-Saclay)
The interplay between turbulence and the magnetic fields play an important role during the early stages of star formation, when most of the final stellar mass is being built.
In order to study the structure of magnetic fields on 750-2000 AU scales, we have acquired interferometric polarization observations of low-mass protostellar cores with the SMA at 345GHz. Polarization is detected in all objects. We will present results on the distribution of the polarized intensity, polarization fraction and angle, and on the relative orientations between the magnetic field lines and the outflow direction, describing how it compares to observations at other wavelengths and the dependence of the polarization fraction on the environment.
The derived magnetic field morphology obtained from dust polarization rely on the ability of dust grains to align with it. Since the observed mm and sub-mm polarization result from a combination of different local magnetic field, density and temperature conditions along the line-of-sight, it is necessary to use 3D models to constrain the robustness of dust polarized emission as a tracer, especially in highly inhomogeneous environments.
Using the state-of-the-art code RAMSES (that includes the ambipolar diffusion), we simulate the gravitational collapse of a slightly turbulent magnetized core. We use the POLARIS code to produce maps of the Stokes parameters for different assumptions of the dust alignment mechanisms. We compare these results with direct integrations at different depths to obtain the mean magnetic field direction and strength and present synthetic observations including instrumental effects directly comparable to our interferometric observations.
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