X-ray spectroscopy of galactic hot gas along the PKS 2155-304 sight line

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 O vil and O vIII absorption lines were measured with the Low and High Energy Transmission Grating Spectrographs aboard Chandra, and the O VII, O vIII, and Ne IX emission lines produced in an adjacent field of the PKS 2155-304 direction were observed with the X-ray Imaging Spectrometer aboard Suzaku. Assuming vertically exponential distributions of the gas temperature and the density, we performed a combined analysis of the absorption and emission data. The gas temperature and the density at the galactic plane were determined to be (2.5+0.3+0.6) × 106K and (1.4-0.4+0.5) × 10-3cm-3, and the scale heights of the gas temperature and density were 5.6-4.2+7.4 kpc and 2.3 -0.8+0.9kpc, respectively. These values are consistent with those obtained in the LMC X-3 direction. © 2010. Astronomical Society of Japan.