The ALMA Survey of 70 mu m Dark High-mass Clumps in Early Stages (ASHES). II. Molecular Outflows in the Extreme Early Stages of Protocluster Formation
Journal article, 2020
We present a study of outflows at extremely early stages of high-mass star formation obtained from the ALMA Survey of 70 mu m dark High-mass clumps in Early Stages (ASHES). Twelve massive 3.6-70 mu m dark prestellar clump candidates were observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. Forty-three outflows are identified toward 41 out of 301 dense cores using the CO and SiO emission lines, yielding a detection rate of 14%. We discover six episodic molecular outflows associated with low- to high-mass cores, indicating that episodic outflows (and therefore episodic accretion) begin at extremely early stages of protostellar evolution for a range of core masses. The time span between consecutive ejection events is much smaller than those found in more evolved stages, which indicates that the ejection episodicity timescale is likely not constant over time. The estimated outflow dynamical timescale appears to increase with core masses, which likely indicates that more massive cores have longer accretion timescales than less massive cores. The lower accretion rates in these 70 mu m dark objects compared to the more evolved protostars indicate that the accretion rates increase with time. The total outflow energy rate is smaller than the turbulent energy dissipation rate, which suggests that outflow-induced turbulence cannot sustain the internal clump turbulence at the current epoch. We often detect thermal SiO emission within these 70 mu m dark clumps that is unrelated to CO outflows. This SiO emission could be produced by collisions, intersection flows, undetected protostars, or other motions.
Massive stars
Protoclusters
Protostars
Star formation
Infrared dark clouds
Interstellar line emission
Interstellar medium
Stellar jets
Stellar winds
Author
Shanghuo Li
Chinese Academy of Sciences
Korea Astronomy and Space Science Institute
Harvard-Smithsonian Center for Astrophysics
Patricio Sanhueza
National Institutes of Natural Sciences
The Graduate University for Advanced Studies (SOKENDAI)
Qizhou Zhang
Harvard-Smithsonian Center for Astrophysics
Fumitaka Nakamura
The Graduate University for Advanced Studies (SOKENDAI)
National Institutes of Natural Sciences
Xing Lu
National Institutes of Natural Sciences
Junzhi Wang
Chinese Academy of Sciences
Tie Liu
Chinese Academy of Sciences
Ken'ichi Tatematsu
National Institutes of Natural Sciences
James M. Jackson
NASA Ames Research Center
Andrea Silva
National Institutes of Natural Sciences
Andres E. Guzman
National Institutes of Natural Sciences
Takeshi Sakai
University of Electro-Communications
Natsuko Izumi
National Institutes of Natural Sciences
Ibaraki University
Daniel Tafoya
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Fei Li
Chinese Academy of Sciences
Yanett Contreras
Leiden University
Kaho Morii
University of Tokyo
National Institutes of Natural Sciences
Kee-Tae Kim
Korea Astronomy and Space Science Institute
University of Science and Technology (UST)
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 903 2 119Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Environmental Sciences
DOI
10.3847/1538-4357/abb81f