http://arxiv.org/abs/1312.7029
We suggest a thin (scale height ~80 pc) diffuse component to the Galactic Ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium. The morphology of the scattered component is expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is however incomplete as it is flux-limited and spans the small lifetime of X-ray astronomy (~50 years), compared to the characteristic time of 1000-10000 years that would contribute to the diffuse emission observed today due to time delays. We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross section due to coherence effects in the elastic scattering from multi-electron atoms and molecules. This scattered emission can be distinguished from the contribution of low X-ray luminosity stars by the presence of narrow fluorescent K-$\alpha$ lines of Fe, Si and other abundant elements present in the interstellar medium and by directly resolving the contribution of low X-ray luminosity stars. We find that within $1^o$ latitude of the Galactic plane the scattered emission contributes on average 10-50% of the GRXE flux and can even dominate the stellar emission in the optimistic case. X-rays with energies $\gtrsim 1$ keV from XBs should also penetrate deep inside the HI and molecular clouds, be absorbed and heat the interstellar medium. We find that this heating rate can dominate over the heating by cosmic rays in a significant part of the Galaxy.
Mon, 30 Dec 13
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