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Kinematics and physical properties of a highly filamentary Infrared Dark Cloud

Henshaw, Jonathan David (2014) Kinematics and physical properties of a highly filamentary Infrared Dark Cloud. PhD thesis, University of Leeds.

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This thesis contains a detailed study of the kinematics and physical properties of a potential site of massive star formation; the IRDC G035.39-00.33. The gas kinematics are first of all investigated using high-spectral resolution and high-sensitivity data from the IRAM 30 m telescope. The primary focus of this work is the J = 1 → 0 transition of both N2H+ and C18O, as well as N2H+ (3 − 2). Dense gas is found to be extended over ∼ 3 pc scales within G035.39-00.33. The C18 O observations confirm the presence of at least three morphologically distinct filamentary components. It is speculated that the merging of filaments may be responsible for the formation of localised density enhancements at their interface; the potential sites for massive star and star-cluster formation. The kinematic properties of the dense gas are then probed at high-angular resolution, using observations of N2H+ (1−0) from the Plateau de Bure Interferometer. It is revealed that the dense gas of G035.39-00.33 is organised into a complex network of mildly supersonic filaments separated in velocity by < 1 km s−1 . Whilst global velocity gradients throughout each filament are small, there is evidence for dynamic processes on local scales. This suggests that the kinematics are influenced by the dense (and in some cases, starless) cores. The physical properties of the embedded core population are derived in the final study of this thesis. A total of 14 continuum peaks are identified, representative of the pre- and protostellar core population covering two main clumps within G035.39-00.33. The derived core masses are found to be between 2.4-12.3 solar masses, with sizes and densities between 0.03-0.07 pc and 1.6×10^5-7.3×10^5 cm^-3, respectively. Some of the cores exhibit irregular boundaries, which may imply the presence of unresolved sub-structure. Although the dynamical state of each core is dependent on both its geometry and density profile (which are both sources of uncertainty) it is found that many of the identified cores are unstable to collapse. Cores which are well represented by monolithic, centrally condensed structures, exhibiting low virial parameters and many Jeans masses, are good candidates for the progenitors of intermediate-to-high-mass stars. Within the selected area of G035.39-00.33, two of the identified cores meet this criteria.

Item Type: Thesis (PhD)
Keywords: Massive star formation, molecular clouds, infrared dark clouds, kinematics, dynamics, filament
Academic Units: The University of Leeds > Faculty of Maths and Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds)
Identification Number/EthosID: uk.bl.ethos.631390
Depositing User: Mr Jonathan D. Henshaw
Date Deposited: 19 Nov 2014 15:34
Last Modified: 25 Nov 2015 13:47
URI: http://etheses.whiterose.ac.uk/id/eprint/7075

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