Examinando por Autor "Li, D."

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Acceso Abierto
A Low-mass Cold and Quiescent Core Population in a Massive Star Protocluster
(IOP Science Publishing, 2021-04-29) Li, S.; Lu, X.; Zhang, Q.; Lee, C. W.; Sanhueza, P.; Beuther, H.; Jiménez Serra, I.; Qiu, K.; Palau, A.; Feng, S.; Pillai, T.; Kim, K. T.; Liu, H. L.; Girart, J. M.; Liu, T.; Wang, K.; Liu, H. B.; Li, D.; Lee, J. E.; Li, F.; Li, J.; Kim, S.; Yue, N.; National Natural Science Foundation of China (NSFC); National Research Foundation of Korea (NRF); European Research Council (ERC); Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Li, S. [0000-0003-1275-5251]; Lu, X. [0000-0003-2619-9305]; Zhang, Q. [0000-0003-2384-6589]; Lee, C. W. [0000-0002-3179-6334]; Sanhueza, P. [0000-0002-7125-7685]; Beuther, H. [0000-0002-1700-090X]; Jiménez Serra, I. [0000-0003-4493-8714]; Qiu, K. [0000-0002-5093-5088]; Palau, A. [0000-0002-9569-9234]; Feng, S. [0000-0002-4707-8409]; Pillai, T. [0000-0003-2133-4862]; Kim, K. T. [0000-0003-2412-7092]; Liu, H. L. [0000-0003-3343-9645]; Girart, J. M. [0000-0002-3829-5591]; Liu, T. [0000-0002-5286-2564]; Wang, J. [0000-0001-6106-1171]; Wang, K. [0000-0002-7237-3856]; Liu, H. B. [0000-0003-2300-2626]; Li, D. [0000-0003-3010-7661]; Lee, J. E. [0000-0003-3119-2087]; Li, F. [0000-0002-9832-8295]; Li, J. [0000-0003-3520-6191]; Kim, S. [0000-0001-9333-5608]; Yue, N. [0000-0003-0355-6875]
Pre-stellar cores represent the initial conditions of star formation. Although these initial conditions in nearby low-mass star-forming regions have been investigated in detail, such initial conditions remain vastly unexplored for massive star-forming regions. We report the detection of a cluster of low-mass starless and pre-stellar core candidates in a massive star protocluster-forming cloud, NGC 6334S. With the Atacama Large Millimeter/submillimeter Array (ALMA) observations at a ∼0.02 pc spatial resolution, we identified 17 low-mass starless core candidates that do not show any evidence of protostellar activity. These candidates present small velocity dispersions, high fractional abundances of NH2D, high NH3 deuterium fractionations, and are completely dark in the infrared wavelengths from 3.6 up to 70 μm. Turbulence is significantly dissipated and the gas kinematics are dominated by thermal motions toward these candidates. Nine out of the 17 cores are gravitationally bound, and therefore are identified as pre-stellar core candidates. The embedded cores of NGC 6334S show a wide diversity in masses and evolutionary stages.
Acceso Abierto
The Chemical Structure of Young High-mass Star-forming Clumps. II. Parsec-scale CO Depletion and Deuterium Fraction of HCO+
(The Institute of Physics (IOP), 2020-10-01) Feng, S.; Li, D.; Caselli, P.; Du, F.; Lin, Y.; Sipilä, O.; Beuther, H.; Sanhueza, P.; Tatematsu, K.; Liu, Y.; Zhang, Q.; Wang, Y.; Hogge, T.; Jiménez Serra, I.; Lu, X.; Liu, T.; Wang, K.; Zhang, Y.; Zahorecz, S.; Li, G.; Liu, H. B.; Yuan, J.; National Natural Science Foundation of China (NSFC); Max-Planck-Gesellschaft (MPG); European Research Council (ERC); Chinese Academy of Sciences (CAS); Agencia Estatal de Investigación (AEI); Japan Society for the Promotion of Science (JSPS); Feng, S. [0000-0002-4707-8409]; Li, D. [0000-0003-3010-7661]; Caselli, P. [0000-0003-1481-7911]; Du, F. [0000-0002-7489-0179]; Lin, Y. [0000-0001-9299-5479; Sipilä, O. [0000-0002-9148-1625]; Beuther, H. [0000-0002-1700-090X]; Sanhueza, P. [0000-0002-7125-7685]; Tatematsu, K. [0000-0002-8149-8546]; Liu, S. Y. [0000-0003-4603-7119]; Zhang, Q. [0000-0003-2384-6589]; Wang, Y. [0000-0003-2226-4384]; Hogge, T. [0000-0002-7211-7078]; Jiménez Serra, I. [0000-0003-4493-8714]; Lu, X. [0000-0003-2619-9305]; Liu, T. [0000-0002-5286-2564]; Wang, K. [0000-0002-7237-3856]; Zhang, Z. Y. [0000-0002-7299-2876]; Zahorecz, S. [0000-0001-6149-1278]; Li, G. [0000-0003-3144-1952]; Liu, H. B. [0000-0003-2300-2626]; Yuan, J. [0000-0001-8060-3538]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The physical and chemical properties of cold and dense molecular clouds are key to understanding how stars form. Using the IRAM 30 m and NRO 45 m telescopes, we carried out a Multiwavelength line-Imaging survey of the 70 μm-dArk and bright clOuds (MIAO). At a linear resolution of 0.1–0.5 pc, this work presents a detailed study of parsec-scale CO depletion and HCO+ deuterium (D-) fractionation toward four sources (G11.38+0.81, G15.22–0.43, G14.49–0.13, and G34.74–0.12) included in our full sample. In each source with T < 20 K and nH ~ 104–105 cm−3, we compared pairs of neighboring 70 μm bright and dark clumps and found that (1) the H2 column density and dust temperature of each source show strong spatial anticorrelation; (2) the spatial distribution of CO isotopologue lines and dense gas tracers, such as 1–0 lines of H13CO+ and DCO+, are anticorrelated; (3) the abundance ratio between C18O and DCO+ shows a strong correlation with the source temperature; (4) both the C18O depletion factor and D-fraction of HCO+ show a robust decrease from younger clumps to more evolved clumps by a factor of more than 3; and (5) preliminary chemical modeling indicates that chemical ages of our sources are ~8 × 104 yr, which is comparable to their free-fall timescales and smaller than their contraction timescales, indicating that our sources are likely dynamically and chemically young.