UNIVERSITY OF SOUTHAMPTON Active Galactic Nuclei at High Angular Resolution: An Interferometric Study into the Dusty Hearts of AGN by James Henry Leftley A thesis submitted in partial fulfilment for the degree of Doctor of Philosophy in the Faculty of Engineering and Physical Sciences Department of Physics and Astronomy June 2020 UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF ENGINEERING AND PHYSICAL SCIENCES DEPARTMENT OF PHYSICS AND ASTRONOMY Doctor of Philosophy by James Henry Leftley 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. Contents Nomenclature xvii Declaration of Authorship xix Acknowledgements xx 1 Introduction1 1.1 Seyfert Galaxies..................................1 1.2 The Central Engine................................3 1.2.1 Eddington Limit.............................5 1.2.2 The accretion disk............................5 1.3 Polarised Broad Lines in NGC 1068.......................5 1.4 The Dusty Torus..................................6 1.5 The Spectral Energy Distribution of a Seyfert Nucleus..............6 1.6 The Clumpy Torus................................9 1.7 Dusty Tori and Interferometry..........................9 1.7.1 The polar dust.............................. 10 1.7.2 The hot dust............................... 11 1.7.3 The molecular gas............................ 12 1.8 Motivation and Outline of this Work....................... 13 2 Interferometry: An Overview 15 2.1 The Two Telescope Case............................. 15 2.1.1 Young’s double slit experiment with a monochromatic point source.. 16 2.1.2 A step towards realism: the extended polychromatic source....... 20 2.1.3 Real world measurements........................ 22 2.1.4 Visibilities of simple models....................... 23 2.1.5 The uv plane............................... 25 2.2 The Three Plus Telescope Case.......................... 26 2.2.1 Closure phase............................... 27 3 Observations and Data Reduction 29 3.1 MIDI....................................... 29 3.1.1 Observations............................... 30 3.1.2 Reduction................................. 32 3.1.2.1 Data sorting.......................... 32 3.1.2.2 Calibration........................... 34 3.1.2.3 Quality Control........................ 35 v vi CONTENTS 3.1.2.4 Visibility determination.................... 36 3.1.2.5 No-Track Mode........................ 36 3.2 AMBER...................................... 39 3.2.1 Observations............................... 39 3.2.2 Reduction................................. 39 3.2.2.1 The AO problem with AMBER................ 40 3.3 GRAVITY..................................... 42 3.3.1 Observations............................... 42 3.3.2 AO correction for faint objects...................... 44 3.3.3 Reduction................................. 44 3.3.3.1 Visibility determination.................... 45 3.3.4 Closure phase determination....................... 48 3.4 VISIR....................................... 49 3.5 ISAAC and NACO................................ 49 3.6 ALMA....................................... 50 4 The Mid-IR Interferometric Study of ESO 323-G77 53 4.1 Introduction.................................... 53 4.1.1 ESO 323-G77............................... 53 4.1.2 MIDI modelling............................. 54 4.2 Observations................................... 54 4.2.1 Interferometric observations....................... 55 4.2.2 Interferometric data reduction...................... 57 4.2.3 VISIR data................................ 58 4.2.4 Finding the system axis.......................... 59 4.3 Results....................................... 60 4.3.1 Morphology and variability from single-dish observations....... 60 4.3.2 Interferometric observations....................... 61 4.3.2.1 Dust morphology from interferometric observations..... 61 4.4 Modelling..................................... 62 4.4.1 Geometric model............................. 62 4.4.1.1 MCMC Bayesian modelling.................. 64 4.4.2 Influence of the uv plane......................... 66 4.4.3 Geometric modelling results....................... 67 4.4.4 CAT3D-WIND radiative transfer modelling............... 70 4.5 Discussion..................................... 74 4.5.1 Comparison of the results........................ 74 4.5.2 An evolution of the dust distribution with Eddington ratio?....... 76 4.6 Chapter Summary................................. 77 5 The Near-IR Interferometric Study of ESO 323-G77 79 5.1 Observations and Reduction........................... 79 5.2 Observational Results and Discussion...................... 81 5.3 Modelling..................................... 83 5.4 Modelling Results and Discussion........................ 86 6 New Evidence for Radiative Pressure Driving 91 CONTENTS vii 6.1 Introduction.................................... 91 6.1.1 Radiation pressure............................ 91 6.2 Eddington Ratio.................................. 92 6.3 Observations and Reduction........................... 93 6.3.1 MIDI................................... 93 6.3.1.1 Non-detections......................... 94 6.3.2 VISIR................................... 94 6.3.3 SEDs................................... 98 6.3.3.1 Spitzer............................. 98 6.4 Modelling..................................... 98 6.4.1 SED modelling.............................. 99 6.5 Results....................................... 100 6.5.1 General results.............................. 100 6.5.2 Results for individual objects....................... 100 6.5.3 SED visibility fractions.......................... 102 6.5.4 Results on the correlation between extended flux fraction and Eddington ratio.................................... 102 6.6 Discussion..................................... 105 6.6.1 The evolution of dust distribution with Eddington ratio......... 105 6.6.2 MATISSE candidates........................... 109 6.7 Chapter Summary................................. 110 7 The cold gas in NGC 3783 111 7.1 Observations and Reduction........................... 113 7.2 Results....................................... 114 7.2.1 A molecular inflow?........................... 118 7.2.2 The HCN emission............................ 120 7.3 Chapter Conclusions and Summary........................ 120 8 Conclusions 123 8.1 The Polar Dust of ESO 323-G77 and its Implications.............. 123 8.2 The Sublimation Radius of ESO 323-G77.................... 124 8.3 Does the Distribution of Dust Depend on Radiation Pressure?.......... 125 8.4 The Missing Dust................................. 126 8.5 The Molecular Disk of NGC 3783........................ 127 8.6 The General Structure of AGN Dust....................... 127 A Figures 129 B Tables 143 List of Figures 1.1 An example of a Type 1 and Type 2 AGN spectrum. This figure was adapted from https://pages.astronomy.ua.edu/keel/agn/ courtesy of Bill Keel (Keel, 1983).2 1.2 A cross section diagram of the layout of the unified model of AGN. The corona is depicted in grey around the accretion disk, all other components are as la- belled. Sizes are not to scale............................7 1.3 An example SED of an unobscured (Type 1) AGN in black and the components that comprise the SED as labelled. The black line is the sum of the coloured component lines. Figure from Hickox and Alexander(2018)...........8 1.4 A cross section diagram of the layout of the dusty wind model of AGN. The corona is depicted in grey around the accretion disk, all other components are as labelled. Sizes are not to scale........................... 12 2.1 A graphical representation of Young’s double slit/pinhole experiment...... 16 2.2 A diagram illustrating a simplified layout of the optical light path of a two tele- scope interferometer. In grey is a movable mirror that can adjust the length of d2 The two paths are fed into the instrument.................... 17 2.3 A representation of a Michelson-Morley interferometer, the arrows depict the light path...................................... 18 2.4 A representation of a Michelson