Episodic Protostellar Outflows: A Proper Motion Study in Serpens South

Serpens South is a notable protostellar cluster with signatures of recent star formation, including a high protostellar fraction. Within the region, several protostars provide important mechanical feedback via outflows. We investigate the molecular outflow driven by the Class 0 protostar known as CARMA-7, which is located in the central hub of Serpens South. Two epochs of observations with the Atacama Large Millimeter/sub-millimeter Array (ALMA) with sub-arcsecond resolution capture the well-collimated, episodic outflow with distinct ejecta knots. This outflow, traced with 12CO J = 3-2 and SiO J = 8-7, appears to be mostly blueshifted to the south and redshifted to the north, with radial velocities up to at least 25 km/s. We present the first proper motion study of this outflow by comparing observations taken in 2017 and 2021. The measured proper motions trace the ejection history and refine the inferred outflow morphology. We find that proper motions of the 12CO J = 3-2 and SiO J = 8-7 knots range between 10 - 40 mas/yr, corresponding to 30-90 km/s. Using radial velocities and proper motions, we determined that the inclinations of the outflow lobes are ~60 -80 degrees relative to the line of sight. Finally, we measure ejection timescales as recent as ~10 to ~120 years, and we discuss this in the context of other known protostars with recent ejecta events.