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Title: The influence of radiative feedback on star formation observed by the James Clerk Maxwell Telescope Gould Belt Survey of nearby star-forming regions
Author: Rumble, Damian Jack
ISNI:       0000 0004 5992 2667
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2016
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The aim of this thesis is to investigate evidence of heating and radiative feedback in local Gould Belt star-forming regions. I discuss what impact, if any, radiative feedback is having on the star formation. I primarily use Submillimeter Common-User Bolometer Array 2 (SCUBA-2) observations from the James Clerk Maxwell Telescope (JCMT) Gould Belt legacy Survey (GBS) of nearby star-forming regions. I analyse this data in conjunction with catalogues of candidate young stellar objects (YSOcs) from mid-infrared surveys with Spitzer IRAC and MIPS surveys. I use the ratio of SCUBA-2 fluxes to calculate dust temperature, given a constant value of dust opacity spectral index, following the method of Reid & Wilson (2005). I employ a two-component beam (2CB) cross convolution to map the temperature of the Serpens MWC 297 region, achieving a resolution of 19.9′′. I employ a convolution kernel to map the temperature of the majority of the JCMT GBS, including the Aquila W40 complex, achieving a resolution of 14.8′′. I use the fellwalker clump finding algorithm to produce a global catalogue of 619 SCUBA-2 850 μm clumps across 26 distinct sub-regions of the JCMT GBS, calculating real temperatures where available. I was the PI of a proposal to observe 12CO 3-2 line emission, with the aim of decontaminating the SCUBA-2 850 μm band. I find 12CO 3-2 line contamination has a significant impact, increasing the dust temperatures calculated per pixel, on average, by 3 K where contamination is less than 10%, and by 16 K where contamination is greater than 10% (in the Aquila W40 complex). I find evidence for 12 outflows in this region, associated with active star formation. I also use archival VLA data to decontaminate both SCUBA-2 bands of free-free emission associated with massive star formation. Where compact free-free sources are sufficiently bright and optically thick, for example the B1.5Ve star MWC 297, their contribution can lead to prominent bright sources at the submillimeter wavelengths detected by SCUBA-2 and lower temperatures around Herbig stars. I present published studies of the Serpens MWC 297 region and the Aquila W40 complex. In both cases I find evidence that the presence of young OB stars is raising the temperatures of nearby clumps. Examining clumps across the JCMT GBS, I find that those clumps isolated from OB stars have a mean temperature of 15±2 K, a value that is consistent with gas temperatures (Friesen et al., 2009) and Bonnor-Ebert sphere models (Kirk et al., 2006). I find no evidence of heating from embedded low-to-medium mass YSOs. Clumps that lie within 3 pc of OB stars have a mean temperature of 21±4 K and O type stars heat clumps over the greatest range. By remodelling the heated clumps with a temperature of 15 K, I calculate that up to 10% of clumps in the JCMT GBS are no longer Jeans unstable, indicating that radiative feedback from OB stars is potentially suppressing fragmentation and allowing for the formation of more massive stars.
Supervisor: Hatchell, Jennifer Sponsor: Science and Technology Facilities Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Observational Astrophysics