Structual study of Galactic hot gas toward Markarian 421 from X-ray absorption and emission lines

Abstract

Abstract We present a structural study of the hot ISM in the Galactic halo along the sight line toward the bright active galactic nucleus Mkn 421. The O vii and O viii absorption lines were measured with the Low Energy Transmission Grating Spectrograph aboard Chandra toward Mkn 421; the O vii and O viii emission lines were observed in the adjacent fields of the line of sight with the X-ray Imaging Spectrometer aboard Suzaku. We jointly analyzed the absorption and emission spectra while assuming exponential distributions of the gas temperature and density from the Galactic plane, and constrained the temperature and density at the plane to be ($3.2^{+0.6}_{-0.7}$) × 106 K and ($1.2^{+0.5}_{-0.4}$) × 10−3 cm−3, with a scale heights of $1.6^{+1.7}_{-0.7}$ kpc and > 2.8 kpc, respectively. The results are consistent with those obtained in the LMC X-3 direction and the PKS 2155−304 direction, describing a thick disk-like hot gas with its height of a few kpc from the Galactic plane.