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Paper: Proper Motions and Structure of the Radio Components Near SGR A*: Evidence for Ionized Gas Falling Into the Massive Black Hole at the Galactic Center
Volume: 186, The Central Parsecs of the Galaxy
Page: 224
Authors: Zhao, J.-H.; Goss, W. M.
Abstract: Proper motions and radio structures of the HII components near Sgr A* have been determined based on high resolution (0.1 arcsec) observations at 13 and 7 mm during the past 7 years (1991-1998). Proper motions up to 30 mas yr-1 (or 1200 km s-1) have been observed for a number of prominent features. These proper motions, measured from compact HII components, can be explained by motions of a clumpy HII gas accelerated by either strong winds and outflows or explosive events at the Galactic Center. Large pattern speeds due to wave or shock motions in the circumnuclear medium at the Galactic Center can also be responsible for some of the observed proper motions. In addition, the HII components near Sgr A* (within the central 2.5 arcsec or 0.1 pc) show filamentary structures suggesting that the HII components are tidally disrupted by tides due to the concentrated mass at the Galactic Center. Based on the proper motion measurements, we also infer that the Minicavity is a transient phenomena (< 500 years old), created by the interactions between the orbiting ionized streamer and the fast moving materials at the Galactic Center. The proper motion of the Tip, NE of the Minicavity, suggests that a portion of the orbiting ionized gas components will lose angular momenta and move towards Sgr A* as a result of these interactions. High precision measurements of the proper motions for the emitting HII components can be used to track the motions of the accreting gas in proximity to the super massive black hole associated with Sgr A*.
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