The Origin of the Diffuse X-ray Emission from the Galactic Ridge

We propose deep observations of the Galactic ridge in order to determine the origin of the diffuse Xray emission, utilizing the high spectral resolution and sensitivity of XMM instruments to extended emission. Recently a nonthermal component has been detected in the spectrum above 10 keV and there is evidence that it contributes to the emission below 10 keV as well. It has been shown thatthe interaction of low energy cosmic rays with the ambient ISM produces Xray line and continuum emission. However, distinction between thermal vs. nonthermalscenarios has not been possible due to the limited spectral resolution and sensitivity of the current instruments. We show that XMM is the first Xray observatory capable of distinguishing between these two scenarios. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]