The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). X. Hot Gas Reveals Deeply Embedded Star Formation
Journal article, 2024
Massive infrared dark clouds (IRDCs) are considered to host the earliest stages of high-mass star formation. In particular, 70 μm dark IRDCs are the colder and more quiescent clouds. At a scale of about 5000 au using formaldehyde (H2CO) emission, we investigate the kinetic temperature of dense cores in 12 IRDCs obtained from the pilot Atacama Large Millimeter/submillimeter Array Survey of 70 μm dark High-mass clumps in Early Stages (ASHES). Compared to the 1.3 mm dust continuum and other molecular lines, such as C18O and deuterated species, we find that H2CO is mainly sensitive to low-velocity outflow components rather than to quiescent gas expected in the early phases of star formation. The kinetic temperatures of these components range from 26 to 300 K. The Mach number reaches about 15 with an average value of about 4, suggesting that the velocity distribution of gas traced by H2CO is significantly influenced by a supersonic nonthermal component. In addition, we detect warm line emission from HC3N and OCS in 14 protostellar cores, which requires high excitation temperatures (E u /k ∼ 100 K). These results show that some of the embedded cores in the ASHES fields are in an advanced evolutionary stage, previously unexpected for 70 μm dark IRDCs.
Author
Natsuko Izumi
Academia Sinica
Patricio Sanhueza
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
M. M. Kettenis
Academia Sinica
X. Lu
Shanghai Astronomical Observatory
Shanghuo Li
Max Planck Society
Giovanni Sabatini
Arcetri Astrophysical Observatory
Fernando A. Olguin
National Tsing Hua University
Q. Zhang
Harvard-Smithsonian Center for Astrophysics
Fumitaka Nakamura
The Graduate University for Advanced Studies (SOKENDAI)
University of Tokyo
National Astronomical Observatory of Japan
Ken’ichi Tatematsu
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
Kaho Morii
National Astronomical Observatory of Japan
University of Tokyo
T. Sakai
University of Electro-Communications
Daniel Tafoya
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 963 2 163Subject Categories
Meteorology and Atmospheric Sciences
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Other Physics Topics
DOI
10.3847/1538-4357/ad18c6