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arXiv · 2505.08470

Origin of the Shell Structure in the Primary Outflow from IRAS 15398-3359

Tomoyuki Hanawa·Yuki Okoda·Yao-Lun Yang·Nami Sakai
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Abstract

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, H$_2$CO, 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.

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Tomoyuki Hanawa, Yuki Okoda, Yao-Lun Yang, Nami Sakai. 2025-05-13. Origin of the Shell Structure in the Primary Outflow from IRAS 15398-3359. https://arxiv.org/abs/2505.08470

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