Astrochemistry

ALMA Observations of Massive Clouds in the Central Molecular Zone: External-Pressure-Confined Dense Cores and Salpeter-like Core Mass Functions

By Keith Cowing

Status Report

astro-ph.GA

December 3, 2024

Filed under ALMA, astro-ph.GA, astrochemistry, astronomy, biochemistry, central molecular zone, Dust Ridge cloud e, Interstellar, molecular cloud, organic chemistry, Sgr C

ALMA Observations of Massive Clouds in the Central Molecular Zone: External-Pressure-Confined Dense Cores and Salpeter-like Core Mass Functions — The integrated intensity (0th moment) maps of the H2CO and CH3CN line emission toward the three clouds. The inner and outer red dashed loops in the left panels show the ALMA primary-beam responses at 50% and 30%, respectively. The left panels show the integrated intensities of H2CO 30,3–20,2 and CH3CN 120–110/ 121–111, while the right panels are the zoomed-in views of the dashed boxes in the left panels. The blue contours show the 1.3 mm dust continuum at levels of 5 and 20 ×σ, where σ = 40 µJy beam−1 . The green ‘+’ symbols illustrate the peak positions of the cores identified from the 1.3 mm continuum. (The complete figure set (7 images) is available in the online journal.) — astro-ph.GA

We present Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 (1.3 mm) observations of dense cores in three massive molecular clouds within the Central Molecular Zone (CMZ) of the Milky Way, including the Dust Ridge cloud e, Sgr C, and the 20 km s^-1 cloud, at a spatial resolution of 2000 au.

Among the 834 cores identified from the 1.3 mm continuum, we constrain temperatures and linewidths of 253 cores using local thermodynamic equilibrium (LTE) methods to fit the H₂CO and/or CH₃CN spectra. We determine their masses using the 1.3 mm dust continuum and derived temperatures, and then evaluate their virial parameters using the H₂CO and/or CH₃CN linewidths and construct the core mass functions (CMFs).

We find that the contribution of external pressure is crucial for the virial equilibrium of the dense cores in the three clouds, which contrasts with the environment in the Galactic disk where dense cores are already bound even without the contribution of external pressure.

We also find that the CMFs show a Salpeter-like slope in the high-mass (>~3-6 Msun) end, a change from previous works with our new temperature estimates. Combined with the possible top-heavy initial mass functions (IMFs) in the CMZ, our result suggests that gas accretion and further fragmentation may play important roles in transforming the CMF to the IMF.

Zhenying Zhang, Xing Lu, Tie Liu, Sheng-Li Qin, Adam Ginsburg, Yu Cheng, Hauyu Baobab Liu, Daniel L. Walker, Xindi Tang, Shanghuo Li, Qizhou Zhang, Thushara Pillai, Jens Kauffmann, Cara Battersby, Siyi Feng, Suinan Zhang, Qi-Lao Gu, Fengwei Xu, Wenyu Jiao, Xunchuan Liu, Li Chen, Qiu-yi Luo, Xiaofeng Mai, Zi-yang Li, Dongting Yang, Xianjin Shen, Meizhu Liu, Zhiqiang Shen

Comments: ApJ accepted. The 4 figure sets with numerous panels will be published on the AAS journal website
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2412.01593 [astro-ph.GA] (or arXiv:2412.01593v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2412.01593
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Submission history
From: Xing Lu
[v1] Mon, 2 Dec 2024 15:09:54 UTC (7,692 KB)
https://arxiv.org/abs/2412.01593
Astrobiology, Astrochemistry,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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