S187 : SCP 1 (H2): A Curved Molecular Hydrogen Outflow

Details S187 : SCP 1 (H2): A Curved Molecular Hydrogen Outflow S187 : SCP 1 (H2): A Curved Molecular Hydrogen Outflow

Jun 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...500..853s&link_type=abstract

Astrophysical Journal v.500, p.853

Astronomy and Astrophysics

Astronomy

14

Ism: Jets And Outflows, Ism: Individual Alphanumeric: S187, Ism: Molecules, Stars: Pre-Main-Sequence

Scientific paper

We imaged in the near-infrared the region associated with IRAS 01202+6133, which lies to the southeast of the Sharpless H II region S187, designated as S187 IR. We report the discovery of a curved molecular hydrogen outflow that extends over a region of 76" (0.38 pc at D = 1 kpc), identified as S187:SCP 1 (H2). The outflow changes direction by more than 90 deg in a continuous way and is the most dramatic example of direction variability in a jet source known to date. The outflow-driving source is probably an extreme T Tauri star identified as NIRS 1 located at the apex of the curved structure. The curved jetlike structure shows a sinuous chain of several emission knots located along an extended H2 nebulosity. The similarity with the properties of optical Herbig-Haro jets observed in the near-IR allows us to conclude that S187:SCP 1 (H2) is a Herbig-Haro object. We discuss whether the supersonic side-wind model proposed by Canto & Raga provides the best physical scenario for the curved outflow seen in S187 IR. According to this model, the initial angle of the jet is nearly opposite to the wind direction, and the wind action turns the jet through 150 deg, resulting in a minimum radius of curvature of 0.14 pc. Assuming typical values for T Tauri stars in molecular environments ( M dot =10^{-7} M&sun; yr-1, vjet = 150 km s-1, vsound = s = 10 km s-1, na = 104 cm-3), the required wind velocity is 10 km s-1, which is of the same order of magnitude as the typical velocities of T Tauri stars relative to their surrounding molecular clouds. Furthermore, the predicted position of the stagnation point, where the hydrostatic pressure in the jet equals the ram pressure of the wind, coincides with an observed H2 emission maximum along the curved part of the outflow. The predicted curve extends to a bow-shock-like H2 nebulosity located 2' (0.46 pc at D = 1 kpc) away from the curved outflow.

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