ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Evidence for a Molecular Jet Launched at an Unprecedented Early Phase of Protostellar Evolution

Somnath Dutta, Chin Fei Lee, Naomi Hirano, Tie Liu, Doug Johnstone, Sheng Yuan Liu, Ken’ichi Tatematsu, Paul F. Goldsmith, Dipen Sahu, Neal J. Evans, Patricio Sanhueza, Woojin Kwon, Sheng Li Qin, Manash Ranjan Samal, Qizhou Zhang, Kee Tae Kim, Hsien Shang, Chang Won Lee, Anthony Moraghan, Kai Syun JhanShanghuo Li, Jeong Eun Lee, Alessio Traficante, Mika Juvela, Leonardo Bronfman, David Eden, Archana Soam, Jinhua He, Hong Li Liu, Yi Jehng Kuan, Veli Matti Pelkonen, Qiuyi Luo, Hee Weon Yi, Shih Ying Hsu

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Protostellar outflows and jets play a vital role in star formation as they carry away excess angular momentum from the inner disk surface, allowing the material to be transferred toward the central protostar. Theoretically, low-velocity and poorly collimated outflows appear from the beginning of the collapse at the first hydrostatic core (FHSC) stage. With growing protostellar core mass, high-density jets are launched, entraining an outflow from the infalling envelope. Until now, molecular jets have been observed at high velocity (≳100 km s−1) in early Class 0 protostars. We, for the first time, detect a dense molecular jet in SiO emission with low velocity (∼4.2 km s−1, deprojected ∼24 km s−1) from source G208.89-20.04Walma (hereafter G208Walma) using ALMA Band 6 observations. This object has some characteristics of FHSCs, such as a small outflow/jet velocity, extended 1.3 mm continuum emission, and N 2D+ line emission. Additional characteristics, however, are typical of early protostars: collimated outflow and SiO jet. The full extent of the outflow corresponds to a dynamical timescale of ∼ 930 − 100 + 200 yr. The spectral energy distribution also suggests a very young source having an upper limit of T bol ∼ 31 K and L bol ∼ 0.8 L . We conclude that G208Walma is likely in the transition phase from FHSC to protostar, and the molecular jet has been launched within a few hundred years of initial collapse. Therefore, G208Walma may be the earliest object discovered in the protostellar phase with a molecular jet.

Original languageEnglish
Article number130
JournalAstrophysical Journal
Issue number2
Publication statusPublished - 2022 Jun 1

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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