Fuse Observations Of The Loop I/local Bubble Interaction Region

摘要

We used the FUSE (Far Ultraviolet Spectroscopic Explorer ) satellite to observe O VI emission along two sight lines toward the edge of the interaction zone (IZ) between the Loop I superbubble and the Local Bubble. One sight line was chosen because material in the interaction zone blocks distant X-ray emission, and should thus do the same for nonlocal O vi emission. We measured an O vi intensity of I_(shad) = 2750 ± 550 photons cm~(-2) s~(-1) sr~(-1) along this "shadowed" sight line, and I_(unshad) = 10,800 ± 1200 photons cm~(-2)s~(-1)sr~(-1) along the other sight line. Given these results, very little (approx< 800 photons cm~(-2)s~(-1)sr~(-1)) of the emission arises from the near side of the interaction zone, which likely has an H I column density of about 4 × 10~(20) cm~(-2) along the "shadowed" sight line. The O vi emission arising within Loop I (～10~4 photons cm~(-2) s~(-1) sr~(-1)) is probably associated with gas of n_e ～ 0.1 cm~(-3) and an emitting path length of ～2.5 pc, suggesting it arises at interfaces rather than from gas filling Loop I. In contrast, the C hi emission is similar along both sight lines, indicating that much of the emission likely arises on the near side of the interaction zone.