The soft diffuse X-ray emission of twelve fields observed with Suzaku are presented together with two additional fields from previous analyses. All have galactic longitudes 65$^\circ $$\lt$$\ell$$\lt$ 295$^\circ $ to avoid contributions from the very bright diffuse source that extends at least 30$^\circ $ from the Galactic center. The surface brightnesses of the Suzaku nine fields for which apparently uncontaminated ROSAT All Sky Survey (RASS) were available were statistically consistent with the RASS values, with an upper limit for differences of 17 $\times$ 10$^{-6}$cs$^{-1}$arcmin$^{-2}$ in R45-band. The OVII and OVIII intensities are well correlated to each other, and OVII emission shows an intensity floor at $\sim$2 photonss$^{-1}$cm$^{-2}$str$^{-1}$ (LU). The high-latitude OVIII emission shows a tight correlation with excess of OVII emission above the floor, with (OVIII intensity) $=$ 0.5 $\times$ [(OVII intensity) $-$ 2LU], suggesting that temperatures averaged over different line-of-sight show a narrow distribution around $\sim$0.2 keV. We consider that the offset intensity of OVII arises from the Heliospheric solar wind charge exchange and perhaps from the local hot bubble, and that the excess OVII (2–7LU) is emission from more distant parts of the Galaxy. The total bolometric luminosity of this galactic emission is estimated to be 4 $\times$ 10$^{39}$ergs$^{-1}$, and its characteristic temperature may be related to the virial temperature of the Galaxy.

We present Suzaku spectra of X-ray emission in the fields just off the LMC X-3 sight line. O VII, O VIII, and Ne IX emission lines are clearly detected, suggesting the presence of an optically thin thermal plasma with an average temperature of 2.4 ×10 6 K. This temperature is significantly higher than that inferred from existing Xray absorption line data obtained with Chandra grating observations of LMC X-3, strongly suggesting that the gas is not isothermal. We then jointly analyze these data to characterize the spatial and temperature distributions of the gas. Assuming a vertical exponential Galactic disk model, we estimate the gas temperature and density at the Galactic plane and their scale heights as 3.6(2.9, 4.7) × 10 6 K and 1.4(0.3, 3.4) × 10 −3 cm −3 and 1.4(0.2, 5.2) kpc and 2.8(1.0, 6.4) kpc, respectively. This characterization can account for all the O VI line absorption, as observed in a FUSE spectrum of LMC X-3, but only predicts less than one tenth of the O VI line emission intensity typically detected at high Galactic latitudes. The bulk of the O VI emission most likely arises at interfaces between cool and hot gases.

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 VII 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$-$304 direction were observed with the X-ray Imaging Spectrometer aboard Suzaku. Assuming vertically exponential distributions of the gas temperature and the density, we performed a combined analysis of the absorption and emission data. The gas temperature and the density at the galactic plane were determined to be (2.5$^{+0.6}_{-0.3}$) $\times$ 10$^{6} $K and ($1.4^{+0.5}_{-0.4}$) $\times$ 10$^{-3} $cm$^{-3} $, and the scale heights of the gas temperature and density were 5.6$^{+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.