Multi-epoch Spectroimaging of the DG Tauri Outflows with NIFS
Abstract
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.
- Publication:
-
Protostars and Planets VI Posters
- Pub Date:
- July 2013
- Bibcode:
- 2013prpl.conf1K035W