ALMA Detection of Extreme Blueshifted Ionized Gas within 0.2 pc of Sgr A* from −480 to −300 km s−1

Abstract

Abstract We have used the capabilities of the Atacama Large Millimeter/Submillimeter Array to probe the ionized gas toward the Galactic center with the H30α mm hydrogen recombination line within 30″ of the Galaxy’s dynamical center. The observations are made with spatial and spectral resolutions of 0.″46 × 0.″35 and 3 km s−1, respectively. Multiple compact and extended sources are detected in the minicavity region with extreme negative radial velocities ranging from −480 to −300 km s−1 2″–3″ (0.08–0.12 pc) from Sgr A*. These are the highest radial velocities of ionized gas detected beyond the inner 1″ of Sgr A*. This new component is kinematically isolated from the orbiting ionized gas. The detected gas has a velocity gradient ranging from −50 to −200 km s−1 arcsec−1 located to the southwest of Sgr A* at a position angle of ∼−160°. Previous proper-motion measurements in the immediate vicinity of these extreme high-velocity ionized components have been made, and they show transverse velocities that range from 313 to 865 km s−1. If we assume that they are associated with one another, then the total velocity implies these components are gravitationally unbound. In addition, we report the kinematics of cometary radio and infrared sources. These sources are diagonally distributed with a position angle of ∼50° within 14″ of Sgr A*. We interpret the highly blueshifted features to the southwest where the minicavity is located, and the redshifted cometary sources to the northeast in terms of the interaction of a collimated outflow with an opening angle of ∼30°. An expected mass outflow rate of 2 × 10−7 or 4 × 10−5 M ⊙ yr−1 is estimated by a relativistic jet-driven outflow or collimated stellar winds, respectively.