The role of the interstellar magnetic field in the formation of matter structures as seen by Planck

Andrea Bracco (Institut d’Astrophysique Spatiale)

January 19, 2015

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Abstract: What is the role of the magnetic field in the formation of the filamentary structures seen in the interstellar medium (ISM)? This is a debated topic due to the paucity of relevant observations to test existing models. The Planck satellite has recently completed the first all-sky map of polarized thermal dust emission, revealing a new view of the sky that we have started to explore. I will present a statistical study on the relative orientation between the structure of matter and that of the magnetic field traced by interstellar dust. We measure the magnetic field orientation projected on the plane of the sky from the polarization data, and compute the orientation of filamentary structures in the dust intensity map with a dedicated algorithm. We find that the field geometry projected on the plane of the sky is well correlated with the distribution of matter. While in the diffuse ISM, the structures of matter tend to be aligned with the projected magnetic field orientation, in molecular clouds the data reveal coherent structures which perpendicular to the field. I will discuss our results in light of theoretical and numerical scenarios on the formation of structures under the mutual action of turbulence, self-gravity and magnetic fields in the ISM.