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

TL;DR

This study maps the distribution of K-shell line emissions from heavy elements along the Galactic plane, distinguishing between the Galactic center and ridge X-ray emissions, revealing differences in plasma temperatures and element intensities.

Contribution

It provides the first detailed comparison of K-shell line distributions and plasma temperatures between the Galactic center and ridge X-ray emissions using Suzaku data.

Findings

Distinct intensity profiles for He-like and H-like lines of S, Ar, Ca, Fe.

Significant excess of Fe lines in the Galactic center compared to the ridge.

Different plasma temperatures for the 1 keV and 7 keV components between GCXE and GRXE.

Abstract

We report the global distribution of the intensities of the K-shell lines from the 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 with 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 the GCXE compared to the 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 the GCXE and GRXE. In fact, the spectral analysis of the GCXE and GRXE revealed that the $\sim$1 keV plasma in the GCXE has lower temperature than that in the GRXE, and vice versa for the $\sim$7 keV plasma.