Tightly Correlated X‐Ray/Hα–emitting Filaments in the Superbubble and Large‐Scale Superwind of NGC 3079

Publisher Website
Google Scholar
Abstract
Using Chandra and HST, we show that X-ray and Hα filaments that form the 1.3 kpc diameter superbubble of NGC 3079 have strikingly similar patterns at ~08 resolution. This tight optical line/X-ray match seems to arise from cool disk gas that has been driven by the wind, with X-rays being emitted from upstream, standoff bow shocks or by conductive cooling at the cloud/wind interfaces. We find that the soft X-ray plasma has thermal and kinetic energies ETH ~ 2 × 1056η ergs and EKE ~ 5 × 1054η ergs, where ηX 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 if ηX is large. Hydrodynamical simulations reproduce the observations well using a disk-mass loaded superwind. X-rays are also seen from the base of the radio counterbubble which is obscured optically by the galaxy disk and from the nucleus (whose spectrum shows the Fe Kα line at 6 keV as well as gas absorbed by a moderate neutral hydrogen column). The superbubble is surrounded by a fainter conical halo of X-ray emission that fills the area delineated by high-angle, Hα-emitting filaments, supporting our previous assertion that these filaments form the contact discontinuity/shock between galaxy gas and shocked wind. This X-ray emission is not significantly edge brightened, indicating a partially filled volume of warm gas within the shocked wind, not a shell of conductively heated gas. About 40'' (3 kpc) above the galaxy disk, an X-ray arc may partially close above the bubble, but the northeast quadrant remains open at the surface brightness attained by Chandra, consistent with the notion that the superwind reaches into at least the galaxy halo.
All Related Versions