On the Hα faintness of the North Polar Spur

Abstract

The ratio of H$\alpha$ intensity to 1.4 GHz radio continuum intensity in the North Polar Spur (NPS) is measured to be $\lesssim 50$, two orders of magnitude smaller than the values of $\sim 10^4$ observed in the typical shell-type old supernova remnants, Cygnus Loop and S147. The extremely low H$\alpha$-to-radio intensity ratio favours the Galactic-Centre explosion model for NPS, which postulates a giant shock wave at a distance of several kilo parsecs in the hot and low-density Galactic halo with low hydrogen recombination rate, over the local supernova(e) remnant model.

Accepted for MNRAS, 8 pages, 8 figures

References in corpus (15)

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Cited by in corpus (1)

• Discovery of the Goat Horn complex: a $\sim 1000$ deg${}^2$ diffuse X-ray source connected to radio loop XII