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The Large-Scale Structure of Magnetic Fields Associated with Filamentary Molecular Clouds

Mehrnoosh Tahani
University of Calgary, Canada

We present a new method to find the line-of-sight strength and morphology of magnetic fields in star forming regions using Faraday rotation measurements. We applied this method to four relatively nearby filamentary molecular clouds of Orion A, Orion B, Perseus, and California. In this method we use rotation measure data from the literature, a chemical evolution code, along with extinction maps of each cloud. In California and Orion A, we find clear evidence that the magnetic fields at one side of these filamentary structures are pointing towards us and are pointing away from us at the other side.
The magnetic field morphologies that can explain this change of direction across filaments include toroidal, helical, and bow morphologies. We investigate these three models by combining our results with those of Planck observations in Orion A. Using Monte Carlo simulations and probability values, we find that of the three possible morphologies, toroidal is the least probable one and we suggest that the bow morphology is more likely.
To investigate these morphologies further, we use magnetohydrodynamics simulations to simulate filamentary molecular clouds and their magnetic field evolution. We find that helical fields are not easily generated in our tested scenarios.

2019 September 24, 13:30

Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia