The polarisation of the cone(IRN) Nebula in NGC 2264

Abstract

The first part of this thesis presents a general review of interstellar gas and dust, and how the study of nebulae has developed. The property of the linear polarisation of light from astronomical objects is a mechanism which has enabled astronomers to extend their knowledge and understanding considerably. Polarisation studies of nebulae have given information on nebular structures, grain size and composition, and the geometrical structures involved. The methods of producing polarisation are discussed, and various models proposed which explain the various observed features. The second part of the thesis deals specifically with the Cone (IRN), which is a small "fan" shaped nebula, found within NGC 2264, very near to Allen’s Infrared object (GL989). Chapter four presents a review of the current knowledge of NGC 2264, and research conducted by other astronomers on the cone (IRN). It explains why it is of particular interest and relevant to this thesis, and also includes some interpretations as to the mechanisms contributing to the observed polarisation. This then leads into the polarisation data, including a brief outline of the construction of the polarimeter. The polarisation maps are presented in the V,R,I filters, and the wavelength dependence of the polarisation is calculated. Chapter six discusses the data, and the possible mechanisms involved. From the results, it is clear that the Cone (IRN) is not a simple reflection nebula. The wavelength dependence of polarisation is mathematically treated and compared to known values, following Serkowski's empirical relationship. Possible configurations of the nebulosity are discussed and interpretations suggested.