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Molecular Outflows in Massive Star Forming Regions

Cunningham, Nichol (2015) Molecular Outflows in Massive Star Forming Regions. PhD thesis, University of Leeds.

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Abstract

This thesis presents millimetre continuum and molecular line observations exploring the properties of molecular outflows towards massive star forming regions. Massive stars produce some of the most energetic phenomena in the Galaxy, yet we still do not have a comprehensive understanding of how they actually form. Outflows are known to play a key role in this formation process and their properties, particularly how they change depending on the mass, luminosity and evolution of the driving source can shed light on how massive stars actually form. This thesis presents observations at both high (SMA 3 arcsecond) and low (JCMT 15 arcsecond) spatial resolution of the known jet/outflow tracers, SiO and 12CO, towards a sample massive star forming region drawn from the RMS survey. Furthermore, the presence of infall signatures is explored through observations of HCO+ and H13CO+, and the hot core nature of the regions is probed using tracers such as CH3CN, HC3N and CH3OH. SiO is detected towards approximately 50% of the massive young stellar objects and HII regions in the JCMT sample. The detection of SiO appears to be linked to the age of the RMS source, with the likely younger sources showing a stronger dependence with SiO. The presence of SiO also appears to be linked to the CO velocity, with SiO more efficiently tracing sources with higher velocity dispersions. In the MOPRA observations towards a sample of 33 RMS sources, CH3CN is detected towards 66% of the sources, with the redder likely younger sources having the largest rotational temperatures. This thesis presents the first interferometric SiO (5-4) and 12CO (2-1) observations, taken with the SMA, towards the massive star forming region G203.3166/NGC 2264-C. In this intermediate/massive star forming cluster, SiO is again tracing the youngest sources. Both the SiO and 12CO emission trace two bipolar, high velocity outflows towards the mm brightest, IR-dark, likely youngest sources in this region. In contrast the IR-bright RMS source, AFGL 989-IRS1, in NGC 2264-C displays no associated molecular outflow emission. Furthermore, the high resolution follow-up SMA observations towards G192.6005/S255IR and the first interferometric 12CO and SiO observations towards G194.9349 show a high velocity outflow traced by 12CO in each region. In both regions the outflow appears to be driven by the IR-bright RMS source. However, no high velocity SiO counterpart is observed in either region. Thus, the lack of associated SiO emission may be a sign of age in these regions.

Item Type: Thesis (PhD)
Keywords: Massive star formation; Molecular outflows; SiO; Chemistry; Massive young stellar objects.
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.675014
Depositing User: Nichol Cunningham
Date Deposited: 30 Nov 2015 11:33
Last Modified: 26 Apr 2016 15:43
URI: http://etheses.whiterose.ac.uk/id/eprint/11180

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