Ovi Column Density Distribution in the Local Bubble - Results from 3D Adaptive Mesh Refinement Simulations

Abstract

The Local Bubble (LB) is an X-ray emitting region extending 100 pc in radius in the Galactic plane and 300 pc perpendicular to it, and it is embedded in a somewhat larger H{\sc i} deficient cavity. Its origin and spectral properties in UV, EUV and X-rays are still poorly understood. We have performed 3D high resolution (down to 1.25 pc) hydrodynamic superbubble simulations of the LB and Loop I superbubble in a realistic \emph{inhomogeneous} background ISM, disturbed by supernova (SN) explosions at the Galactic rate. We can reproduce (i) the size of the bubbles (in contrast to similarity solutions), (ii) the interaction shell with Loop I, discovered with ROSAT, (iii) predict the merging of the two bubbles in about 3 Myr, when the interaction shell starts to fragment, and, (iv) the generation of blobs like the Local Cloud as a consequence of a dynamical instability. The \ion{O}{6} column densities are monitored and found to be in excellent agreement with \textsc{Copernicus} and FUSE absorption line data, showing LB column densities $<1.7 \times 10^{13} {\rm cm}^{-2}$, in contrast to other existing models.