K-Shell Line Distribution of Heavy Elements along the Galactic Plane Observed with Suzaku

Abstract

We report on the global distribution of the intensities of the K-shell lines from He-like and H-like ions of S, Ar, Ca, and Fe along the Galactic plane. From the profiles, we clearly separate the Galactic center X-ray emission (GCXE) and the Galactic ridge X-ray emission (GRXE). The intensity profiles of the He-like K$ \alpha $ lines of S, Ar, Ca, and Fe along the Galactic plane are approximately similar to each other, while not for the H-like Ly$ \alpha $ lines. In particular, the profiles of H-like Ly$ \alpha $ of S and Fe show remarkable contrast: a large excess of Fe, and almost no excess of S lines in GCXE compared to GRXE. Although the prominent K-shell lines are represented by $ \sim$ 1 keV and $ \sim$ 7 keV temperature plasmas, these two temperatures are not equal between GCXE and GRXE. In fact, a spectral analysis of GCXE and GRXE revealed that the $ \sim$ 1 keV plasma in GCXE has a lower temperature than that in GRXE, and vice versa for the $ \sim$ 7 keV plasma.