An Observation of Diffuse Soft X-Ray Background and Distribution of Hot Interstellar Medium

The diffuse soft X-ray background in 0.07∼ 2.0 keV has been observed along a small circle with the angular width of 10– covering b=—57– ∼ 77– and crossing the galactic plane at l=125– and 283–. Observed spectra are well fitted with models emitted from a thin hot gas with two or multi-temperature components and attenuated by a slab or interspersed neutral gas clouds. However the multi-temperature component model has some difficulties to explain the diffuse component expected from observations of OVI absorption lines. The two temperature component model with interspersed clouds consistently interprets a physical state of the hot interstellar medium. It turned out that the hot interstellar medium interspersed with neutral clouds of a representative hydrogen column density of 1× 10²⁰ cm^-2has two temperature components (10^5.8 K,(1.2-4.5)× 10⁶ K) and a disk-like distribution with the thickness of 580(± 100). {(p/k)/10⁴cm^-3 K} ^-2 pc at the pressure of p/k cm^-3 K along the galactic plane. Its pressure (p/k) is obtained to be 1.4(+0.7,-0.5)× 10⁴cm^-3 K, assuming that hot gases responsible for the diffuse soft X-rays and OVI ions are in pressure equilibrium. This interpretation qualitatively agrees with the theoretical prediction proposed by McKee and Ostriker. This revised version was published online in July 2006 with corrections to the Cover Date.