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Title: Rubies in the dust : tracing high mass star formation throughout the Milky Way
Author: Gallaway, Mark John
ISNI:       0000 0004 2738 2758
Awarding Body: University of Hertfordshire
Current Institution: University of Hertfordshire
Date of Award: 2012
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Over the last decade a number of potential tracers of massive star (M > 8M ) formation have been put forward. In this thesis I attempt to understand how these tracers relate to one another and attempt to identify the most suitable tracer for future surveys for massive star formation sites. In this thesis we examine a number of these tracers; the Methanol Maser Multi- Beam Survey (MMB), the Red MSX Survey (RMS), the Boston University Five Colleges Radio Astronomical Observatory (BU-FCRAO) Galactic Ring Survey (GRS), the BOLOCAM Galactic Plane Survey (BGPS) and the Perretto & Fuller (P&F) Infrared Dark Cloud (IRDC) Catalogue, in addition to the Cyganowski Extended Green Objects Catalogue. This work employs a bespoke non-circular aperture photometry technique, K=1 Nearest Neighbour Analysis and Minimum Spanning Trees (MSTs) in multi-dimensional parameter space with oversampling, edge weighing, mean edge fracturing and convex hull tting. Additional, new 13CO observations were made of the young infrared cluster BDS[2003] 107 (Bica 107) and its environs. We see that despite not being contained within the GLIMPSE Point Source Archive the bulk of masers have an infrared bright counterpart. Photometry of the counterparts shows that they occupy the same colour spaces as that previously determined in Ellingsen (2006); [3.6]-[4.5]>1 and [8.0]<1. We show that the bulk of RMS MYSOs do not exhibit masing and that a signi cant fraction of MYSOs are not found within the RMS . Additionally, we see that the EGO RMS association rate is higher than expected. The BGPS, GRS and P&F IRDC exhibit clustering and elongating, with a common characteristic clustering scale of the order of 6 8 pc. We see that the BGPS is more strongly associated with massive star formation than the GRS. Additionally, we see that although in general all three hull types occupy similar co-located spatial positions they also appear as isolated hulls. The analysis of Bica 107 shows that it is part of a larger star forming region containing Bica 108 and the ultra compact HII region, G5.89. The maser associated with Bica 107 appears to lie on the edge of the cluster's expanding CO shell. The observation that the IRAC colour-magnitude occupied by the masers from the Ellingsen sample is consistent with the MMB, sample suggest that these objects have broadly consistent colours during their masing phase. This can be attributed to the dust and gas envelope being radiatively dominant. The cross matching results indicate that the majority of MYSOs do not exhibit masing. The RMS appears to be missing MYSOs due to missing sources in the MSX catalogue and a photospheric bluing due to MSX large beam width, moving candidates outside the RMS colour cut. The RMS EGO relationship appears to be inconsistent with observed MYSO evolution and may be indicative of multiple EGO generation mechanism as suggested by De Buizer and Vacca (2010). The BPGS and GRS objects and IRDCs do not appear to form a star formation sequence and their existence is not necessarily an indicator of on-going star formation; rather they are an indication of the potential for star formation. All three species types showing signs of clustering and elongation. The shared characteristic scale is suggestive that there may be a processes acting below the scale of the GMC but above that of a single star forming region. The maser associated with Bica 107 appears to be either an example of triggered star formation or late onset star formation within the region and is not an example of continuing star formation within Bica 107. We conclude that a GLIMPSE based colour-selected survey, with follow-up observation to reduce contamination, would be the most appropriate method for identifying MYSOs, given the reliability of the tracers examined in this thesis.
Supervisor: Not available Sponsor: STFC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: mass star formation ; methanol masers ; spanning trees