Multiwavelength observations of radio-loud active galaxies

• Main Author: Bliss, Amelia
• Published: University of Bristol 2013
• Subjects: 523.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633096

This research thesis uses multiwavelength observations to investigate a sample of the 3CRR catalogue, as well as a separate radio-loud source, PKS J231O-437, with the general aim of modelling the energy released as synchrotron radiation. The minimum energy magnetic fields are calculated for six of the 3CRR objects, and any correlations between these and source power are discussed in the conclusions. Chapter One introduces active galaxies and jets, explaining what is meant by 'radio-loud', and the classifications used to categorise them, as well as a summary of the characteristics of their host galaxies. It then goes on to cover Unified theories, and how BL Lac objects (one of which, PKS J2310-437, is investigated as a case study) fit into this scheme. The introduction finishes with a section on emission mechanisms, synchrotron radiation, Doppler boosting and minimum energy calculations. Chapter Two is a case study, looking at the BL Lac object, PKS J231O-437. This is a radio and X-ray loud active galaxy which appears to have little optical emission, either nuclear or from jets. ESO NTT and Spitzer data are used to investigate any nuclear or jet flux emitted in five optical and [our infrared bands, with the aim of better categorising this unusual source. Chapters Three and Four are the main body of this research thesis. Using data from Spitzer's lRAC instrument, as well as X-ray and radio data, the underlying electron spectrum of the observed jets is modelled with the aim of discovering the electron spectral break. This is expected to lie in the mid-infrared region; the wavelength range observed by IRAC. This break is then used to calculate the minimum energies and magnetic fields of the jets. Chapter Three covers the observations, data reduction and results, and Chapter Four consists of the data analysis, modelling and discussion of results. Chapter Five concludes the work, summarising the work on the 3CRR sources and PKS J231 0-437, then bringing them together. The chapter finishes with a section on how further investigations could be carried out. The Appendices contain the initial ELLIPSE parameters used for the 3CRR galactic modelling; all of the 3CRR Spitzer images post-galactic subtraction; and three-colour images of the eight sources in which jets were detected, plus one of 3C 231, a starburst galaxy.