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Title: X-ray spectroscopy of high ionisation outflows in Suzaku observed type I active galaxies
Author: Gofford, Jason
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 2013
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In this thesis I present the culmination of my research into the phenomenon of AGN winds in the X-ray regime using the Suzaku X-ray telescope. There are two studies described in this thesis. In the first I perform a deep broad-band spectral analysis of radio-quiet quasar MR2251-178 and outline the evidence which suggests that its X-ray continuum is partially-covered by ionised gas along the line of sight, possibly in the form of a disc-wind. In the second study I perform a survey for Fe xxv Heα and Fe xxvi Lyα absorption lines in a large sample of 51 Suzaku-observed AGN (99 observations). These absorption lines are unambiguously detected in 40% of the sample (20/51 AGN), consistent with recent results from XMM-Newton, with peak and mean absorber parameters of log(NH/cm⁻²) ≈ 23 and log(ξ/erg cm s⁻¹) ≈ 4.5. Their velocities cover a continuous range, from v_out < 1500kms⁻¹ to ~ 100,000kms⁻¹, with a median of ~ 0.056 c. The winds are located on sub-parsec scales ( < 0.1 pc, typically), placing them in the vicinity of the inner accretion disc. A correlation analysis shows that more powerful AGN launch more powerful winds which implies their being accelerated by radiation pressure. Indeed, the overall energetics of the outflows are quantitatively consistent with continuum-driving via Compton-scattering, although a magnetic origin cannot be ruled out on the basis of the available data. I find that the mean kinetic power of the outflows is ~ 1%L_bol, suggesting a possible feedback effect in their host galaxies could be important. Finally, I show that the measured outflow velocity distribution bares a striking resemblance to one inferred using the MBH - δ* relation for local quiescent galaxies which suggests that the observed MBH - δ* relation may be an artefact of wind-induced feedback. Overall, these results are consistent with the view that highly-ionised FeK winds may represent an important addition to the currently held AGN paradigm, and further enforce the hypothesis that they may be important for galaxy evolution.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QB460 Astrophysics