The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). VI. The Core-scale CO Depletion
Journal article, 2022
Studying the physical and chemical properties of cold and dense molecular clouds is crucial for the understanding of how stars form. Under the typical conditions of infrared dark clouds, CO is removed from the gas phase and trapped onto the surface of dust grains by the so-called depletion process. This suggests that the CO-depletion factor (f D ) can be a useful chemical indicator for identifying cold and dense regions (i.e., prestellar cores). We have used the 1.3 mm continuum and C18O (2-1) data observed at the resolution of ∼5000 au in the ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES) to construct averaged maps of f D in 12 clumps to characterize the earliest stages of the high-mass star formation process. The average f D determined for 277 of the 294 ASHES cores follows an unexpected increase from the prestellar to the protostellar stage. If we exclude the temperature effect due to the slight variations in the NH3 kinetic temperature among different cores, we explain this result as a dependence primarily on the average gas density, which increases in cores where protostellar conditions prevail. This shows that f D determined in high-mass star-forming regions at the core scale is insufficient to distinguish among prestellar and protostellar conditions for the individual cores and should be complemented by information provided by additional tracers. However, we confirm that the clump-averaged f D values correlate with the luminosity-to-mass ratio of each source, which is known to trace the evolution of the star formation process.
Author
Giovanni Sabatini
Istituto di Radioastronomia
Stefano Bovino
Istituto di Radioastronomia
University of Concepcion
Patricio Sanhueza
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
Kaho Morii
University of Tokyo
National Astronomical Observatory of Japan
Shanghuo Li
Korea Astronomy and Space Science Institute
Elena Redaelli
Max Planck Society
Q. Zhang
Harvard-Smithsonian Center for Astrophysics
X. Lu
Shanghai Astronomical Observatory
S. Feng
Xiamen University
Daniel Tafoya
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Natsuko Izumi
Academia Sinica
T. Sakai
University of Electro-Communications
Ken’ichi Tatematsu
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
David Allingham
University of Newcastle
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 936 1 80Subject Categories
Astronomy, Astrophysics and Cosmology
Geosciences, Multidisciplinary
DOI
10.3847/1538-4357/ac83aa