The Milky Way’s Vestigial Nuclear Jet: Assessing its ISM Interactions at Parsec Radii

A pair of uniquely radial, coherent X-ray and molecular features straddle Sgr A* out to 2 pc in projection. The Chandra feature in Galactic south extends for 0.4 parsec with spectrum characteristic of a nuclear jet that may have entrained gas from a shocked site in the eastern arm of the nuclear mini-spiral. Previously published work indicates a few decade synchrotron lifetime of its electrons, so this is an active collimated nuclear outflow. The molecular counter-feature mapped by ALMA in Galactic north is heavily extinguished (undetected in Paschen-α) and shows cylindrical expansion of >150 solar masses around overall recession velocity +50 km/s wrt LSR. Beyond current ALMA coverage, radio filaments extend toward several radio/ionized fronts that may intersect the extrapolated, putative counter-jet.

I therefore mapped gas kinematics and excitation, and near-IR extinction along these features by taking two dozen, carefully registered SOAR/tSpec λλ1-2.4 micron co-added echelle spectra at R=3500 and arcsecond resolution. These exploratory spectra show several H and He, molecular H, and ionized iron lines. Gas median velocities along the 10 arcsecond-long southern X-ray feature diminish from +160 km/s of that mini-spiral arm interaction (where line width exceeds 300 km/s) to +75 km/s as line widths decline to the instrumental resolution. I obtained a limit on the Brackett-γ brightness of the molecular flow. Both radial features have positive velocities, a pattern that complicates a naive interpretation of interactions with a two-sided recently deactivated jet. I discuss the energetics of this flow, and use extinction and excitation to locate other suggestive nebulae that appear in the HST Paschen-α Survey of the Galactic Center.