University of Leicester
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Axisymmetry in the broad line regions of active galaxies

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posted on 2014-12-15, 10:40 authored by Christopher M. Rudge
The broad line region (BLR) in active galactic nuclei (AGN) is at a distance from the central power source that is not currently resolved by observations. Thus the exact structure and kinematics of the BLR are largely unknown and have to be inferred by indirect methods and a considerable degree of uncertainty remains. This thesis will study one such area of uncertainty: Is the BLR axially symmetric or spherically symmetric A model is developed for the distribution of the broad emission line widths and it is shown that the best fit parameters support an axisymmetric BLR. A similar model for the X-ray spectral index distribution also shows evidence for an orientation dependent ax. Solving for the inclination angle for a sample of 116 Mgii line widths from the RIXOS sample show that the orientations of the complete sample are not random as expected. Rather they are random at each luminosity up to some cut-off angle which itself increases with luminosity. This reflects an increase in opening angle of the torus in unified models of AGN - i.e. the angle beyond which broad lines are no longer observed and the object appears as a type 2 rather than a type 1 AGN. This change in opening angle can also be used to explain the observed anti-correlation between FWHMh and ax without the requirement of an orientation dependent spectral index. Finally, it is also shown how changes in the line width distribution with redshift, z, are sensitive to different values of H0 and q0 and that it is possible to use this to set limits on H0 and q0 with a relatively small observational sample at z = 2.5.


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Awarding institution

University of Leicester

Qualification level

  • Doctoral

Qualification name

  • PhD



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