Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1K035

Multi-epoch Spectroimaging of the DG Tauri Outflows with NIFS

White, Marc (The Australian National University)
McGregor, Peter (The Australian National University)
Bicknell, Geoff (The Australian National University)
Salmeron, Raquel (The Australian National University)
Sutherland, Ralph (The Australian National University)
Beck, Tracy (Space Telescope Science Institute)
Wagner, Alex (Tsukuba University)

The outflows driven by young stellar objects provide important clues to the nature of the underlying accretion-ejection mechanism, as well as probing the physical conditions around the object. We present sub-arcsecond-resolution spectroimaging data of the outflows of the young stellar object DG Tauri, obtained from 2005-2013 in four distinct epochs using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. These data allow us to simultaneously probe the kinematics and structure of the outflows. We rigorously separate the two [Fe II] 1.644 µm emission-line components in the approaching outflow for the first time. The high-velocity approaching jet is dominated by moving shock-excited ‘knots’, which emerge with a period of ~5 years and may be linked to observed bursts of accretion activity (see poster by Chou et al). The presence of a stationary recollimation shock implies a jet terminal velocity of 400-700 km s-1 and a jet launch radius of 0.02-0.07 AU. Jet acceleration is observed well beyond the height where magnetocentrifugal acceleration should cease. This is successfully modeled as a form of magnetic acceleration internal to the jet. No jet rotation is observed. The low-velocity approaching component is successfully modeled as a turbulent entrainment layer along the jet boundary, which requires the presence of a ~20-60 mG magnetic field around the jet. The receding outflow takes the form of a large bubble. We determine that this is due to the receding counter-jet being blocked by ambient material. Further analysis of our multi-epoch data set will allow us to track the evolution of the outflows over multiple accretion-ejection events.

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