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Lonely cores: molecular line observations of isolated star formation

Quinn, Ciara 2013. Lonely cores: molecular line observations of isolated star formation. PhD Thesis, Cardiff University.
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Abstract

In this thesis, I present molecular line & continuum data of a sample of small, southern, isolated cores. I present a multi-wavelength view of the cores, by utilising optical images, 2MASS extinction maps, CO integrated intensity maps and 1.2mm continuum images of each of the cores. Spitzer data are used to identify young stellar objects local to each core, which may influence the evolution of the core. Column densities and masses are calculated for each core. The column densities calculated from the CO and 1.2mm continuum tracers are shown to be in excellent agreement with each other, and with the peak extinction, as seen on the 2MASS extinction maps. A comparison of column density derived from 1.2mm continuum and C18O observations suggest that a fraction of the gas has frozen out onto the dust grains in the densest parts of the core. The masses derived from 13CO, C18O and 1.2mm continuum observations are compared with the virial mass calculated from the observed linewidths. The cores are found to be within 3� of virial equilibrium in all cases, which suggests that all cores may be gravitationally bound. I find that the observed linewidths of the isolated cores are consistent with models of star formation by turbulent dissipation. The C18O linewidth is observed to be narrower than the 13CO linewidth, which is narrower than the 12CO linewidth in all cases. This suggests that as the density of the tracer increases, the linewidth decreases. Therefore, turbulent support against collapse is removed from the inside out, resulting in stars forming in the densest parts of the cores. I also present a proposed evolutionary diagram, based on the observed 12CO and ratio of 12CO/C18O linewidths. I hypothesise that a young core will have large 12CO and C18O linewidths. In an older core, the turbulence will have had time to dissipate in the core centre, and so the C18O linewidth will be narrower. For the oldest cores, the dissipation of turbulence will have occurred in the outer parts of the core and so the 12CO/C18O ratio will be small, indicating a more evolved core.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Star formation; Molecular clouds; CO; Lonely Cores; Mopra; Spitzer; 2MASS
Funders: STFC
Date of First Compliant Deposit: 30 March 2016
Last Modified: 19 Mar 2016 23:36
URI: http://orca.cardiff.ac.uk/id/eprint/57749

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