Multi-epoch subarcsecond [Fe II] spectroimaging of the DG Tau outflows with NIFS – II. On the nature of the bipolar outflow asymmetry

White, M. C. and Bicknell, G. V. and McGregor, P. J. and Salmeron, R (2014) Multi-epoch subarcsecond [Fe II] spectroimaging of the DG Tau outflows with NIFS – II. On the nature of the bipolar outflow asymmetry. Monthly Notices of the Royal Astronomical Society, 442 (1). pp. 28-42. ISSN 0035-8711


Abstract

The origin of bipolar outflow asymmetry in young stellar objects (YSOs) remains poorly understood. It may be due to an intrinsically asymmetric outflow launch mechanism, or it may be caused by the effects of the ambient medium surrounding the YSO. Answering this question is an important step in understanding outflow launching. We have investigated the bipolar outflows driven by the T Tauri star DG Tauri on scales of hundreds of astronomical units, using the Near-infrared Integral Field Spectrograph on Gemini-North. The approaching outflow consists of a well-collimated jet, nested within a lower-velocity disc wind. The receding outflow is composed of a single-component bubble-like structure. We analyse the kinematics of the receding outflow using kinetic models, and determine that it is a quasi-stationary bubble with an expanding internal velocity field. We propose that this bubble forms because the receding counterjet from DG Tau is obstructed by a clumpy ambient medium above the circumstellar disc surface, based on similarities between this structure and those found in the modelling of active galactic nuclei outflows. We find evidence of interaction between the obscured counterjet and clumpy ambient material, which we attribute to the large molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown to be consistent with our interpretation. We conclude that the bipolar outflow from DG Tau is intrinsically symmetric, and the observed asymmetries are due to environmental effects. This mechanism can potentially be used to explain the observed bipolar asymmetries in other YSO outflows.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 03 Aug 2021 22:41
Last Modified: 03 Aug 2021 22:41
Uncontrolled Keywords: techniques: high angular resolution, techniques: imaging spectroscopy, stars: individual: DG Tauri, stars: protostars, stars: variables: T Tauri, Herbig Ae/Be, ISM: jets and outflows
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Funding Details:
Identification Number or DOI: https://doi.org/10.1093/mnras/stu788
URI: http://eprints.usq.edu.au/id/eprint/42994

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