Active galactic nuclei at high angular resolution: an interferometric study into the dusty hearts of AGN

Abstract

Infra-Red (IR) interferometry of local Active Galactic Nuclei (AGN) has revealed a warm (∼300K-400K) polar dust structure that cannot be trivially explained by the putative dust torus of the unified model. The polar dust led to the development of the disk+wind scenario which comprises of a hot (∼1000K) compact equatorial dust disk and a polar dust wind.

The goal of this work is to use IR interferometry to test if the polar dust wind is ubiquitous in AGN and how it is created. Ultimately, I will attempt to determine if the disk+wind model is a good description of AGN.

Here I present MIDI observations of ESO 323-G77, a Seyfert galaxy hosting a Type 1 AGN, and prove that it hosts a polar dust structure consistent with a dusty wind suggesting the wind is ubiquitous. I proceed to study ESO 323-G77 in the near-IR with GRAVITY and find structure on the scale of the hot dust disk from the disk+wind model. Further investigating the link between the MIDI observed structure and Eddington ratio reveals that the winds are likely to be driven by radiation pressure. Finally I analyse ALMA observations of NGC 3783, a well studied galaxy that hosts a Seyfert Type 1 AGN, and constrain a CO(3-2) molecular gas disk that agrees with the material reservoir disk of the disk+wind model.

The observations studied in this thesis preferentially support the radiation pressure driven polar wind and disk model over the classic dusty torus model. The confirmation of the new model sets the stage for future high resolution studies into AGN physics and AGN driven galactic feedback mechanisms.

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Identifiers

ORCID for James Leftley: orcid.org/0000-0001-6009-1803

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