2008ApJ...681.1310S

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/cm2/s/sr along this ``shadowed'' sight line, and I<sub>unshad</sub>=10,800±1200 photons cm2/s/sr along the other sight line. Given these results, very little (≲ 800 photons/cm2/s/sr) of the emission arises from the near side of the interaction zone, which likely has an H I column density of about 4x10<sup>20</sup>/cm2 along the ``shadowed'' sight line. The O VI emission arising within Loop I (∼10⁴ photons/cm2/s/sr) is probably associated with gas of n_e∼0.1/cm3 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 III emission is similar along both sight lines, indicating that much of the emission likely arises on the near side of the interaction zone.