Multiple Outflows around the Single Protostar IRAS 15398-3359

Jinshi Sai^1*

¹Astronomy and Astrophysics, ASIAA, Taipei, Taiwan

* Presenter:Jinshi Sai, email:jsai@asiaa.sinica.edu.tw

Understanding evolution of molecular outflows is essential for revealing angular momentum transfer mechanisms in the disk formation process. Previous observations have suggested the presence of the secondary outflow around the single protostar IRAS 15398-3359, which is launched in a direction almost perpendicular to its primary outflow. In this talk, we report a discovery of the third outflow around the protostar. Our mosaic observations with the ACA 7-m array have revealed that the 12CO 2-1 emission shows a bipolar outflow toward the north and south at offsets of ~3000 to 10,000 au from the protostar. The newly uncovered outflow is on a larger scale than the primary and secondary outflows that are less than 1500 au in length, and also tiled from the other two outflows by ~20-70 degree. The estimated dynamical time scales are different between these multiple outflows, suggesting that the outflow direction changes with time. Comparisons of the observed properties of its dense core with numerical simulations suggest that turbulence or misalignment between the magnetic field and the rotational axis of the core is responsible for the time variation of the outflow direction in this source. Considering the moderate turbulence level of the protostellar core and probability of misalignents, the dynamic change of the outflow direction might be a common event at the very early stage of protostellar phase.

Keywords: Protostars, Star formation, Molecular outflow, Disk formation, Radio astronomy