X-ray Spectroscopy of Galactic Hot Gas along the PKS 2155-304 Sight Line

TL;DR

This study uses X-ray spectroscopy to analyze hot gas in the Galactic halo along the PKS 2155-304 sight line, determining temperature, density, and scale heights through combined absorption and emission data.

Contribution

It provides the first combined analysis of absorption and emission lines to measure the Galactic halo's hot gas properties in this direction.

Findings

Gas temperature at the Galactic plane is approximately 2.5 MK.

Gas density at the Galactic plane is about 1.4 x 10^{-3} cm^{-3}.

Scale heights for temperature and density are roughly 5.6 kpc and 2.3 kpc.

Abstract

We present a detailed spectroscopic study of the hot gas in the Galactic halo toward the direction of a blazer PKS 2155-304 (z=0.117). The OVII and OVIII absorption lines are measured with the Low and High Energy Transmission Grating Spectrographs aboard Chandra, and the OVII, OVIII, and NeIX emission lines produced in the adjacent field of the PKS 2155-304 direction are observed with the X-ray Imaging Spectrometer aboard Suzaku. Assuming vertically exponential distributions of the gas temperature and the density, we perform a combined analysis of the absorption and emission data. The gas temperature and density at the Galactic plane are determined to be 2.5(+0.6,-0.3) MK and 1.4(+0.5,-0.4) x 10^{-3} cm^{-3} and the scale heights of the gas temperature and density are 5.6(+7.4,-4.2) kpc and 2.3(+0.9,-0.8) kpc, respectively. These values are consistent with those obtained in the LMC X-3 direction.