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Dana Alina

On the relative orientation between magnetic fields, filaments and Cold Clumps in the Galaxy

mercredi 4 décembre 2019, 10h30

salle de conférences de l’observatoire

Dana Alina

Département de Physique, School of Science and Technology, Université Nazarbayev, Astana (Kazakhstan)

Mots-clés :
Astrophysique ; milieu interstellaire : poussière, extinction ; champs magnétiques ; polarisation

Résumé :

It is now commonly accepted that the interstellar magnetic field is one of the principal actors in the evolution of interstellar filaments and in the process of star formation along with gravity and turbulence. Polarimetric data of dust emission polarization is well suited to probe magnetic field’s structure in dense, cold interstellar medium and to provide hints on dust physics through the efficiency of grains alignment with respect to the magnetic field lines.

Analysis of relative orientation between filamentary structures and magnetic fields is one of the methods to reveal the role of the magnetic field in the evolution of these structures.

I will present a statistical analysis of the relative orientation between the plane-of-sky magnetic field and the filaments associated with the Galactic Cold Clumps. We extracted 90 filaments from the Planck 353 GHz data all over the sky using the Rolling Hough Transform – a pattern detection algorithm. We inferred magnetic field orientations within filaments using optically thin medium assumption and compared the orientation of the hosting filaments and embedded clumps with respect to both the background and inner magnetic fields and compared background and inner magnetic field orientations. We find different behaviours in terms of relative orientation depending on the environment density, and on the density contrast between the filaments and their environment. In particular, filaments located in high background column density regions do not exhibit preferential orientation with respect to background magnetic field while those located in low background column density regions are aligned parallel to the field with the exception of highly contrasted filaments that are mostly perpendicular to it. We also reveal differences in the alignment of the clumps with respect to the filaments’ magnetic field depending on the column density contrast of the hosting filaments : we observe a bimodal distribution of the relative orientations in highly contrasted filaments.

I will discuss these findings in the frame of evolution and environment of the filaments (Alina et al. 2019).