Revisiting the Distance to Radio Loops I and IV Using Gaia and Radio/Optical Polarization Data

  title={Revisiting the Distance to Radio Loops I and IV Using Gaia and Radio/Optical Polarization Data},
  author={Georgia V. Panopoulou and Clive Dickinson and Anthony C. S. Readhead and T. J. Pearson and M. W. Peel},
  journal={The Astrophysical Journal},
Galactic synchrotron emission exhibits large angular scale features known as radio spurs and loops. Determining the physical size of these structures is important for understanding the local interstellar structure and for modeling the Galactic magnetic field. However, the distance to these structures is either under debate or entirely unknown. We revisit a classical method of finding the location of radio spurs by comparing optical polarization angles with those of synchrotron emission as a… 
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North Polar Spur/Loop I: gigantic outskirt of the Northern Fermi bubble or nearby hot gas cavity blown by supernovae?
Radio continuum, microwave and gamma-ray images of the Milky Way reveal a conspicuous, looplike structure that fills almost half of the northern Galactic hemisphere, called Loop I. The interior of


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Using the all-sky ROSAT soft X-ray and 408 MHz radio continuum data, we show that the North Polar Spur (NPS) and its western and southern counterspurs draw a giant dumbbell shape necked at the
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Relationships between X-ray brightness, absorbing column and hardness ratio demonstrate a brightness decrease with latitude governed by increasing absorption, and the comparison with absorption data, local and large-scale dust maps rules out a NPS near side closer than 300 pc.
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The dust-Hi correlation is used to characterize the emission properties of dust in the diffuse interstellar medium (ISM) from far infrared wavelengths to microwave frequencies. The field of this