Galactic Exhaust Vents

Several years ago, Mark Morris and his European colleagues discovered the Galactic center chimneys using X-ray data from the XMM-Newton satellite observatory. The hot, X-ray-emitting plasma is arrayed in two oppositely-directed columns oriented perpendicular to the Galactic plane, each about 100 parsecs (~300 light-years) wide.   The basic interpretation of the chimneys is that plasma has been created near the Galactic center by some combination of energetic outflows resulting from accretion onto the Galactic black hole and supernovae resulting from the continuous formation of massive, short-lived stars in the central molecular zone.  That plasma is then hot enough to expand vertically into the Galactic halo as a portion of the Galactic wind.

In a follow-up paper just completed with former UCLA physics undergraduate, Scott Mackey (now at the University of Chicago), Morris and his colleagues used a very deep Chandra X-ray image of the central portion of the southern chimney to present what they identify as the central cylindrical vent of that chimney.  Its edge-brightened “walls” apparently define the channel along which the hot plasma streams outward from the Galactic center.  This research is now being followed up by two much more extensive X-ray surveys of the central part of the Galaxy, one with XMM and the other with NASA’s Chandra Observatory, with the goal of elucidating the link between the chimneys and the gigantic Fermi Gamma-Ray Bubbles occupying the Galactic halo.