Testing the TDE Outflow Model for the Bipolar Sgr A Lobes at the Galactic Center

Sgr A lobes are a pair of 15-pc-sized bipolar bubbles with co-aligned major axes perpendicular to the Galactic plane found in X-ray and radio observations of the Galactic center (GC). Their elusive origin is a vital ingredient in understanding the ongoing high energy processes at the GC. Here we perform a suite of hydrodynamic simulations to explore the tidal disruption event (TDE) outflow model for the origin of the Sgr A lobes. By following the outflow evolution in the circumnuclear medium, we find that TDE outflows naturally produce bipolar lobes delimited by forward shocks, and the dense postshock shell contributes significantly to the lobe's X-ray emission. Our fiducial run reproduces the morphology, density, temperature, and X-ray surface brightness distribution of the observed Sgr A lobes reasonably well. The current lobe age is ~3300 yr. Our model further predicts that the uplifted wake flow breaks through the ejecta-induced shock front, producing a shock-enclosed head region which is relatively dim in X-rays compared to other lobe regions. Both the dim head region and the predicted limb-brightening feature of the lobes are slightly inconsistent with current X-ray observations, and may be used to further test our model with more sensitive future X-ray observations. While light narrow jets and massive wide winds from TDE events usually do not reproduce the observed oval-shaped morphology of the lobes, the TDE outflow in our fiducial run is massive and yet narrow. Whether it is a jet or wind remains uncertain and future simulations covering both the outflow acceleration region and its pc-scale evolution would be very helpful in determining whether the Sgr A lobes indeed originate from a pair of TDE jets or winds.