Portal de Periódicos da CAPES

The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). VI. The Core-scale CO Depletion

2022; IOP Publishing; Volume: 936; Issue: 1 Linguagem: Inglês

10.3847/1538-4357/ac83aa

1538-4357

G. Sabatini, S. Bovino, Patricio Sanhueza, Kaho Morii, Shanghuo Li, E. Redaelli, Qizhou Zhang, Xing Lu, Siyi Feng, Daniel Tafoya, Natsuko Izumi, Takeshi Sakai, Ken’ichi Tatematsu, David Allingham,

Atmospheric Ozone and Climate

Abstract 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 C 18 O (2–1) data observed at the resolution of ∼5000 au in the ALMA Survey of 70 μ m 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 NH 3 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.