Whewell, MR;
(2017)
A study of X-ray narrow emission lines from ionised gas in Active Galactic Nuclei.
Doctoral thesis , UCL (University College London).
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Abstract
This thesis presents a study of X-ray narrow emission lines from ionised gas within Active Galactic Nuclei (AGN) and is based on the analysis of high- resolution X-ray spectra from XMM-Newton’s Reflection Grating Spectrome- ter. I have investigated the location, ionisation level and chemical abundances of the gas producing X-ray narrow emission lines in NGC 5548 and NGC 1365. Using observations during an unusual time when the nuclear emission of NGC 5548 is obscured by cool absorbing material, I show that the emission lines are consistent with being absorbed by further ionised gas within the AGN system. This is supported by the location I derive for the emission line gas, within those of the known warm absorbers in this system. With NGC 1365 spectra I demonstrate that these emission lines can be used to derive metal abundances within AGN systems; this can be especially important in obscured objects where usual methods of deriving abundances from UV spectra are unavailable due to the large degree of absorption. Finally, leading on from the results on individual objects, I explore outflow-inflow velocities of emission lines in a large sample of AGN, testing whether these velocities are distributed differently for different categories of AGN. With current observations it is not possible to detect population velocity differences in the X-ray narrow emission lines of the magnitude previously seen in optical studies. Through this study, I significantly increase the number of O VII f line detections using a uniform method across a sample of AGN. These three studies show the variety of insights into AGN environments enabled by the study of X-ray narrow emission lines. The thesis closes with a forward look to what could be achieved in this area with the next generation of X-ray observatories.
| Type: | Thesis (Doctoral) |
|---|---|
| Title: | A study of X-ray narrow emission lines from ionised gas in Active Galactic Nuclei |
| Event: | UCL |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| UCL classification: | UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1555784 |
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