Tightly Correlated X-ray/H$\alpha$ Emitting Filaments in the Superbubble and Large-Scale Superwind of NGC 3079

Abstract

Using Chandra and HST we show that X-ray and H$\alpha$ filaments that form the 1.3-kpc diameter superbubble of NGC 3079 have strikingly similar patterns at 0."8 resolution. This tight match seems to arise from cool disk gas that has been driven by the wind, with X-rays being emitted from upstream, stand-off bowshocks or by conductive cooling at the cloud/wind interfaces. We find that the soft X-ray plasma has thermal and kinetic energies of $2\times10^{56}\sqrt{\eta_x}$ and $5\times10^{54}\sqrt{\eta_X}$ erg respectively, where $\eta_X$ is the filling factor of the X-ray gas and may be small; these are comparable to the energies of the optical line-emitting gas. X-rays are also seen from the base of the radio counterbubble that is obscured optically by the galaxy disk, and from the nucleus (whose spectrum shows the Fe K$\alpha$ line). Hydrodynamical simulations reproduce the obbservations well using large filling factors within both filament systems; assuming otherwise seriously underestimates the mass loss in the superwind. The superbubble is surrounded by a fainter conical halo of X-rays that fill the area delineated by high angle, H$\alpha$-emitting filaments, supporting our previous assertion that these filaments form the contact discontinuity/shock between galaxy gas and shocked wind. About 40\arcsec (3 kpc) above the disk, an X-ray arc may partially close beyond the bubble, but the north-east quadrant remains open, consistent with the superwind having broken out into at least the galaxy halo.