Astronomy and Astrophysics, volume 564A, 107-107 (2014/4-2)
A thin diffuse component of the Galactic ridge X-ray emission and heating of the interstellar medium contributed by the radiation of Galactic X-ray binaries.
MOLARO M., KHATRI R. and SUNYAEV R.A.
Abstract (from CDS):
We blackpredict a thin diffuse component blackof the Galactic ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium. blackThis scattered component has the same scale height as that of the gaseous disk (∼80 pc) and is therefore thinner than the GRXE of stellar origin (scale height ∼130 pc). The morphology of the scattered component is blackfurthermore 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 blackincomplete, however, because it is blackflux limited and spans the lifetime of X-ray astronomy (∼50 years)black, blackwhich is very short compared with the characteristic time of 1000-10000 years that blackwould have contributed 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 blackcross-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-α lines of Fe, Siblack, and other abundant elements present in the interstellar medium and by directly resolving the contribution of low X-ray luminosity stars. blackWe find that within 1° latitude of the Galactic plane the scattered emission contributes on average 10-30% of the GRXE flux in the case of known sources and over 50% in the case of simulated sources. In the latter case, the scattered component is found to even dominate the stellar emission in certain parts of the Galactic plane. X-rays with energies > 1 keV from XBs should also penetrate deep inside the HI and molecular clouds, blackwhere they are absorbed and heat the interstellar medium. We find that this heating rate dominates the heating by cosmic rays black(assuming blacka solar neighborhood energy density) in a blackconsiderable part of the Galaxy.
scattering - X-rays: binaries - X-rays: ISM - X-rays: general - atomic processes - X-rays: stars
VizieR on-line data:
<Available at CDS (J/A+A/564/A107): tablea1.dat refs.dat>