Quasar Outflows: Their Scale, Behavior and Influence in the Host Galaxy

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Virginia Tech

Quasar outflows are a major candidate for Active Galactic Nuclei (AGN) feedback, and their capacity to influence the evolution of their host galaxy depends on the mass-flow rate (M) and kinetic luminosity (E) of the outflowing material. Both quantities require measurement of the distance (R) to the outflow from the central source as well as physical conditions of the outflow, which can be determined using spectral observations of the quasar. This thesis presents spectral analyses leading to measurements of R, M and E for three different quasar outflows.

Analysis of LBQS J1206+1052 revealed multiple diagnostic spectral features that could each be used to independently determine R. These diagnostics yielded measurements that were in close agreement, resulting in a robust outflow distance of 840 pc from the central source. This measurement is much larger than predicted from radiative acceleration models (~0.01-0.1 pc), suggesting that outflows appear much farther from the central source than is generally assumed.

The outflow in SDSS J0831+0354 was found to carry a kinetic luminosity of 1045.7 erg/s, which corresponds to 5.2 per cent of the Eddington luminosity of the quasar. This outflow is one of the most energetic outflows to date and satisfies the criteria required to produce AGN feedback effects.

A variability study of NGC 5548 revealed an obscuring cloud of gas that shielded the outflow components, dramatically lowering their ionization state. This resulted in the appearance of absorption from the rare element Phosphorus, as well as from sparsely-populated energy levels of CIII and SiIII. These spectral features allowed for an accurate determination of R and for constraints on the ionization phase to be obtained. The latter constraints were used to develop a self-consistent model that explained the variability of all six outflow components during five observing epochs spanning 16 years.

Observational Astrophysics, Quasar Outflows, AGN Feedback