FAUST. II. Discovery of a Secondary Outflow in IRAS 15398-3359: Variability in Outflow Direction during the Earliest Stage of Star Formation?

Yuki Okoda, Yoko Oya, Logan Francis, Doug Johnstone, Shu Ichiro Inutsuka, Cecilia Ceccarelli, Claudio Codella, Claire Chandler, Nami Sakai, Yuri Aikawa, Felipe O. Alves, Nadia Balucani, Eleonora Bianchi, Mathilde Bouvier, Paola Caselli, Emmanuel Caux, Steven Charnley, Spandan Choudhury, Marta De Simone, Francois DulieuAurora Durán, Lucy Evans, Cécile Favre, Davide Fedele, Siyi Feng, Francesco Fontani, Tetsuya Hama, Tomoyuki Hanawa, Eric Herbst, Tomoya Hirota, Muneaki Imai, Andrea Isella, Izaskun Jímenez-Serra, Claudine Kahane, Bertrand Lefloch, Laurent Loinard, Ana López-Sepulcre, Luke T. Maud, María José Maureira, Francois Menard, Seyma Mercimek, Anna Miotello, George Moellenbrock, Shoji Mori, Nadia M. Murillo, Riouhei Nakatani, Hideko Nomura, Yasuhiro Oba, Ross O'Donoghue, Satoshi Ohashi, Juan Ospina-Zamudio, Jaime E. Pineda, Linda Podio, Albert Rimola, Takeshi Sakai, Dominique Segura-Cox, Yancy Shirley, Brian Svoboda, Vianney Taquet, Leonardo Testi, Charlotte Vastel, Serena Viti, Naoki Watanabe, Yoshimasa Watanabe, Arezu Witzel, Ci Xue, Yichen Zhang, Bo Zhao, Satoshi Yamamoto

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


We have observed the very low-mass Class 0 protostar IRAS 15398-3359 at scales ranging from 50 to 1800 au, as part of the Atacama Large Millimeter/Submillimeter Array Large Program FAUST. We uncover a linear feature, visible in H2CO, SO, and C18O line emission, which extends from the source in a direction almost perpendicular to the known active outflow. Molecular line emission from H2CO, SO, SiO, and CH3OH further reveals an arc-like structure connected to the outer end of the linear feature and separated from the protostar, IRAS 15398-3359, by 1200 au. The arc-like structure is blueshifted with respect to the systemic velocity. A velocity gradient of 1.2 km s-1 over 1200 au along the linear feature seen in the H2CO emission connects the protostar and the arc-like structure kinematically. SO, SiO, and CH3OH are known to trace shocks, and we interpret the arc-like structure as a relic shock region produced by an outflow previously launched by IRAS 15398-3359. The velocity gradient along the linear structure can be explained as relic outflow motion. The origins of the newly observed arc-like structure and extended linear feature are discussed in relation to turbulent motions within the protostellar core and episodic accretion events during the earliest stage of protostellar evolution.

Original languageEnglish (US)
Article number11
JournalAstrophysical Journal
Issue number1
StatePublished - Mar 20 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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