X-ray and Uv Spectroscopy of Galactic Diffuse Hot Gas along the Lmc X–3 Sight Line

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 ×106 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)×106 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. Subject headings: X-rays: diffuse background – Galaxy: halo — X-rays: ISM