Iron Emission Lines on the Galactic Ridge Observed with Suzaku

TL;DR

This study uses Suzaku X-ray observations to analyze iron emission lines along the Galactic plane, revealing their distribution and implications for the origin of Galactic Ridge X-ray Emission.

Contribution

It provides detailed spectral analysis of iron lines across the Galactic plane, clarifying their spatial distribution and ionization states, which advances understanding of the Galactic Ridge X-ray Emission origin.

Findings

Detected three narrow Fe lines at ~6.4, 6.7, and 6.97 keV.

The 6.7 keV line is present throughout the Galactic plane.

Flux ratios vary between the Galactic center and plane regions.

Abstract

In order to elucidate origin of the Galactic Ridge X-ray Emission, we analyzed Suzaku data taken at various regions along the Galactic plane and studied their Fe-K emission line features. Suzaku resolved the Fe line complex into three narrow lines at ~6.4 keV,~6.7 keV and ~6.97 keV, which are K-lines from neutral (or low-ionized), He-like, and H-like iron ions, respectively. The 6.7 keV line is clearly seen in all the observed regions and its longitudinal distribution is consistent with that determined from previous observations. The 6.4 keV emission line was also found in various Galactic plane regions (b~0). Differences in flux ratios of the 6.4 keV/6.7 keV and 6.97 keV/6.7 keV lines between the Galactic plane and the Galactic center regions are studied and its implication is discussed.