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17th of January 2022
Non-thermal Filaments in the Galactic Centre
by Paré et al.
The centre of our Galaxy contains a population of unique structures that appear as long, bright threads at radio frequencies, known as the Radio Arc. These structures are known as the non-thermal filaments (NTFs) and are highly polarized sources of synchrotron radiation. Their synchrotron nature indicates the presence of relativistic, free electrons however the source and mechanism causing the electrons to accelerate to relativistic velocities remains an active topic of research. Recent observations of the Radio Arc NTFs revealed a magnetic field that alternates between being parallel and rotated with respect to the orientation of the filaments. This pattern is in stark contrast to the predominantly parallel magnetic field orientations observed in other GC NTFs. To help elucidate the origin of this pattern, Paré et al. analyze spectro-polarimetric data of the Radio Arc NTFs using an ATCA data set covering the continuous frequency range from ∼4 to 11 GHz at a spectral resolution of 2 MHz. External Faraday effects are identified as the most likely origin of the rotation observed for the Radio Arc NTFs; however, internal Faraday effects are also found to be likely in regions of parallel magnetic field. Further studies are needed to determine whether this alternating magnetic field pattern is present in other multi-stranded NTFs, or is a unique property resulting from the complex interstellar region local to the Radio Arc NTFs. The image above shows the total intensity distribution of the Radio Arc NTFs at 6750 MHz with a bandwidth of 2 GHz, a resolution of 10.9" x 4.8", and an rms noise level of 7.3 mJy/beam. The beam size is shown in the lower right corner of the figure. The rectangular region marked with dashed yellow lines indicates the field of view considered in more detail in the paper. Notable features discussed in the text are marked and labeled. The paper has been published in the Astrophysical Journal.

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