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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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