OBSERVATIONS OF O Ⅵ EMISSION FROM THE DIFFUSE INTERSTELLAR MEDIUM TOWARD l = 113°, b = 71°

摘要

Emission from O Ⅵ (λλ1032,1038) in the diffuse interstellar medium was observed in two, long Far Ultraviolet Spectroscopic Explorer (FUSE) observations at l approx= 113.0° and b approx= 70.7° (near the quasar HS 1307 + 4617). The observed intensities are 2580 +- 380 (random) +- 360 (systematic) and 1100 +- 160 (random) +- 160 (systematic) photons cm~(-2) s~(-1) s~(-1) in the 1032 and 1038 A emission lines, respectively. The electron density, thermal pressure, and depth of the emitting gas are calculated from the observed intensities. The velocity of the emitting material is about +10 km s~(-1) relative to the local standard of rest and less than +30 km s~(-1) relative to the H Ⅰ along the line of sight.The similarity suggests that the highly ionized gas is quiescent and not recently shock heated. Emission from the C Ⅱ 3 s~2 S_(1/2) to 2p~2 P_(3/2) transition at 1037 A is also observed, and upper limits are placed on the intensities of ultraviolet line emission from G Ⅰ, C Ⅲ, N Ⅰ, N Ⅱ, Mg Ⅱ, Si Ⅱ, S Ⅱ, S Ⅲ, S Ⅳ, S Ⅵ, Fe Ⅱ, and Fe Ⅲ.