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
Artikel i vetenskaplig tidskrift, 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.
Infrared dark clouds
Protostars
Massive stars
Protoclusters
Interstellar line emission
Stellar winds
Stellar jets
Interstellar medium
Star formation
Författare
Shanghuo Li
Harvard-Smithsonian Center for Astrophysics
Korea Astronomy and Space Science Institute
Chinese Academy of Sciences
Patricio Sanhueza
The Graduate University for Advanced Studies (SOKENDAI)
National Institutes of Natural Sciences
Qizhou Zhang
Harvard-Smithsonian Center for Astrophysics
Fumitaka Nakamura
National Institutes of Natural Sciences
The Graduate University for Advanced Studies (SOKENDAI)
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
National Aeronautics and Space Administration (NASA)
Andrea Silva
National Institutes of Natural Sciences
Andres E. Guzman
National Institutes of Natural Sciences
Takeshi Sakai
University of Electro-Communications
Natsuko Izumi
Ibaraki University
National Institutes of Natural Sciences
Daniel Tafoya
Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium
Fei Li
Chinese Academy of Sciences
Yanett Contreras
Universiteit Leiden
Kaho Morii
National Institutes of Natural Sciences
University of Tokyo
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 119Ämneskategorier (SSIF 2011)
Meteorologi och atmosfärforskning
Astronomi, astrofysik och kosmologi
Miljövetenskap
DOI
10.3847/1538-4357/abb81f