Asymmetries in bipolar jets from young stars

Abstract

While carrying out a survey of T Tauri stars (TTSs) in the Taurus-Auriga (Tau-Aur) dark cloud for extended forbidden emission-line regions by long-slit spectroscopy we have discovered relatively extended bipolar jets emanating from RW Aur, DO Tau, and DP Tau. In the case of the bright TTS RW Aur the bipolar jet can be traced in Ha and [S II] for at least 20″ on either side of the source. For DO Tau and DP Tau the high-velocity jets extend up to approximately 4″ and 10″, respectively. In RW Aur and DO Tau, our radial velocity measurements indicate that the velocities of the blueshifted and redshifted parts of the outflow differ by about a factor of 2. A search through the literature shows that this rather surprising behavior is not unusual and that in about 50% of bipolar optical outflows the flow velocities of the blueshifted and redshifted parts differ by a factor 1.5-2.5. Possible explanations for these unusual results are briefly discussed, and it seems that the source itself or its immediate environment is responsible for the observed behavior.