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Hierarchical fragmentation and differential star formation in the Galactic `Snake': infrared dark cloud G11.11-0.12

Wang, Ke, Zhang, Qizhou, Testi, Leonardo, van der Tak, Floris, Wu, Yuefang, Zhang, Huawei, Pillai, Thushara, Wyrowski, Friedrich, Carey, Sean, Ragan, Sarah and Henning, Thomas 2014. Hierarchical fragmentation and differential star formation in the Galactic `Snake': infrared dark cloud G11.11-0.12. Monthly Notices of the Royal Astronomical Society 439 (4) , pp. 3275-3293. 10.1093/mnras/stu127

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Abstract

We present Submillimeter Array (SMA) λ = 0.88 and 1.3 mm broad-band observations, and Very Large Array (VLA) observations in NH3 (J, K) = (1,1) up to (5,5), H2O and CH3OH maser lines towards the two most massive molecular clumps in infrared dark cloud (IRDC) G11.11-0.12. Sensitive high-resolution images reveal hierarchical fragmentation in dense molecular gas from the ˜1 pc clump scale down to ˜0.01 pc condensation scale. At each scale, the mass of the fragments is orders of magnitude larger than the Jeans mass. This is common to all four IRDC clumps we studied, suggesting that turbulence plays an important role in the early stages of clustered star formation. Masers, shock heated NH3 gas, and outflows indicate intense ongoing star formation in some cores while no such signatures are found in others. Furthermore, chemical differentiation may reflect the difference in evolutionary stages among these star formation seeds. We find NH3 ortho/para ratios of 1.1 ± 0.4, 2.0 ± 0.4, and 3.0 ± 0.7 associated with three outflows, and the ratio tends to increase along the outflows downstream. Our combined SMA and VLA observations of several IRDC clumps present the most in-depth view so far of the early stages prior to the hot core phase, revealing snapshots of physical and chemical properties at various stages along an apparent evolutionary sequence.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Publisher: Oxford University Press (OUP): Policy P - Oxford Open Option A
ISSN: 0035-8711
Date of First Compliant Deposit: 27 November 2017
Date of Acceptance: 16 January 2014
Last Modified: 22 Feb 2019 11:41
URI: http://orca-mwe.cf.ac.uk/id/eprint/106507

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