IRAS 15398-3359, a Class 0 protostar in Lupus I star forming region, is associated with three generations of outflows. The primary outflow, i.e., the most recent one, shows internal structure named ``shell structure'' in the near infrared emission map. The shell structure is also seen in the emission lines of CO, H2CO, and others species. We find a similar structure in an underexpanded jet produced in aerodynamics and other engineering applications. A high pressure gas ejected through a nozzle expands to form a supersonic flow. When the pressure of the ejected gas becomes lower than that of the ambient gas, the jet is compressed to form a shock wave. The shock heated gas expands again to form substructures along the jet. We examine the similarity between the primary outflow of IRAS 15398-3359 and industrial underexpanded jet and the possibility that the shell structure of the former is due to repeated expansion and compression in the direction perpendicular to the jet propagation.
@article{arxiv.2505.08470,
title = {Origin of the Shell Structure in the Primary Outflow from IRAS 15398-3359},
author = {Tomoyuki Hanawa and Yuki Okoda and Yao-Lun Yang and Nami Sakai},
journal= {arXiv preprint arXiv:2505.08470},
year = {2025}
}
Comments
13 pages, 15 figures to appear in the Astrophysical Journal. (Figures 6, 8, 13, and 15 are associated with animations in the original manuscript.). Acknowledgements are revised