Probing the Physics and Geometry of Active Galactic Nuclei

Super Massive Black Holes (SMBH) inhabit the centre of every major galaxy, some of which power Active Galactic Nuclei (AGN) via mass accretion. In this thesis I explore two of the main approaches taken to study AGN, firstly the use of a wide sample, and secondly detailed observations of a single object. Multi-wavelength emission from AGN can be broken down into physical components which dominate in different wavebands, namely the dusty torus (IR), the accretion disc (optical/UV), the soft X-ray excess (UV/soft X-ray) and hot corona (hard X-rays). I first outline our new sample of around 700 SDSS Optical/UV/X-ray selected AGN, the SOUX sample, where the SDSS emission lines give single epoch black hole mass estimates while the UV/X-rays determine the continuum. I bin and stack the sample in mass and luminosity to look for trends as a function of these two important parameters. I perform detailed continuum fitting on the SOUX sample including the disc, soft X-ray excess and hot corona, and demonstrate clear issues in all current accretion flow models. Simple discs cannot match the UV extent of the most massive AGN irrespective of black hole spin as the high spin fits used in previous studies did not include the strong gravitational redshift which results from general relativistic ray tracing from the inner disc to the observer. I conclude that either there is a systematic over-prediction in black hole masses, or, more likely, the accretion flow in AGN does not take the form of a standard disc but may be fully Comptonised or take the form of something altogether different. I then switch gear to use the variable accretion flow emission to constrain the physical size scale of the dusty torus and Paschen Broad Line Region (BLR) from near-IR reverberation mapping. For Mrk 509, I develop a technique of photometric re-scaling and am able to place loose constraints on the size scales of these regions despite the challenging dataset. This technique is repeated with the much more robust data-set on Mrk 817, observed as part of the wider STORM2 collaboration. Both of these show that the Paschen BLR is co-spatial with the Balmer BLR, which is important as the Paschen BLR is now resolvable with GRAVITY data in a few objects, so can be used to test single epoch mass estimates. I then summarise the presented work and discuss potential avenues of investigation to take this further

Rimonabant improves cardiometabolic risk factors in overweight/obese patients irrespective of treatment with statins: Pooled data from the RIO program

peer reviewe

Lunar Mining: Designing a Robust Robotic Mining System

The annual NASA Robotic Mining Challenge: Lunabotics tasks teams with building robots capable of traversing and mining simulated Lunar terrain. The competition goal is to utilize automation and sensing alongside mechanical systems to harvest icy regolith (gravel) from beneath the satellite’s surface. This year, Utah Student Robotics sought to improve upon the design from last year. The 2019-2020 rover is based on proven NASA concepts, such as the RASSOR 2.0 digging drum, and the Rocker-Bogie mobility platform

The Three Hundred project: The gas disruption of infalling objects in cluster environments

We analyse the gas content evolution of infalling haloes in cluster environments from The Three Hundred project, a collection of 324 numerically modelled galaxy clusters. The haloes in our sample were selected within 5R200 of the main cluster halo at $z$ = 0 and have total halo mass M200 ≥ 1011h-1MO. We track their main progenitors and study their gas evolution since their crossing into the infall region, which we define as 1-4R200. Studying the radial trends of our populations using both the full phase-space information and a line-of-sight projection, we confirm the Arthur et al. (2019) result and identify a characteristic radius around 1.7R200 in 3D and at R200 in projection at which infalling haloes lose nearly all of the gas prior their infall. Splitting the trends by subhalo status,we show that subhaloes residing in group-mass and low-mass host haloes in the infall region follow similar radial gas-loss trends as their hosts, whereas subhaloes of cluster-mass host haloes are stripped of their gas much further out. Our results show that infalling objects suffer significant gaseous disruption that correlates with time-since-infall, cluster-centric distance, and host mass, and that the gaseous disruption they experience is a combination of subhalo pre-processing and object gas depletion at a radius that behaves like an accretion shock

Riparian buffers can help mitigate biodiversity declines in oil palm agriculture

Agricultural expansion drives biodiversity decline in forested tropical regions. Consequently, it is important to understand the conservation value of remnant forest in production landscapes. In a tropical landscape dominated by oil palm we characterized faunal communities across eight taxa occurring within riparian forest buffers, which are legally protected alongside rivers, and compared them to nearby recovering logged forest. Buffer width was the main predictor of species richness and abundance, with widths of 40-100 m on each side of the river supporting broadly equivalent levels of biodiversity to logged forest. However, width responses varied markedly among taxa, and buffers often lacked forest-dependent species. Much wider buffers than are currently mandated are needed to safeguard most species. The largest biodiversity gains are achieved by increasing relatively narrow buffers. To provide optimal conservation outcomes in tropical production landscapes we encourage policymakers to prescribe width requirements for key taxa and different landscape contexts.Newton-Ungku Omar Fund (grants 216433953, 537134717) – delivered by the British Council and funded by the UK Department for Business, Energy and Industrial Strategy and the Malaysian Industry-Government Group for High Technology – as well as the UK Natural Environment Research Council (NE/K016407/1, NE/K016261/1; https://lombok.nerc-hmtf.info/). MJS was supported by a Research Leadership Award from the Leverhulme Trust

Cost Effectiveness and Cost Containment in the Era of Interferon-Free Therapies to Treat Hepatitis C Virus Genotype 1

Abstract Background. Interferon-free regimens to treat hepatitis C virus (HCV) genotype 1 are effective but costly. At this time, payers in the United States use strategies to control costs including (1) limiting treatment to those with advanced disease and (2) negotiating price discounts in exchange for exclusivity. Methods. We used Monte Carlo simulation to investigate budgetary impact and cost effectiveness of these treatment policies and to identify strategies that balance access with cost control. Outcomes included nondiscounted 5-year payer cost per 10000 HCV-infected patients and incremental cost-effectiveness ratios. Results. We found that the budgetary impact of HCV treatment is high, with 5-year undiscounted costs of $1.0 billion to 2.3 billion per 10000 HCV-infected patients depending on regimen choices. Among noncirrhotic patients, using the least costly interferon-free regimen leads to the lowest payer costs with negligible difference in clinical outcomes, even when the lower cost regimen is less convenient and/or effective. Among cirrhotic patients, more effective but costly regimens remain cost effective. Controlling costs by restricting treatment to those with fibrosis stage 2 or greater disease was cost ineffective for any patient type compared with treating all patients. Conclusions. Treatment strategies using interferon-free therapies to treat all HCV-infected persons are cost effective, but short-term cost is high. Among noncirrhotic patients, using the least costly interferon-free regimen, even if it is not single tablet or once daily, is the cost-control strategy that results in best outcomes. Restricting treatment to patients with more advanced disease often results in worse outcomes than treating all patients, and it is not preferred

The Three Hundred project: a large catalogue of theoretically modelled galaxy clusters for cosmological and astrophysical applications

We introduce the The Three Hundred project, an endeavour to model 324 large galaxy clusters with full-physics hydrodynamical re-simulations. Here we present the dataset and study the differences to observations for fundamental galaxy cluster properties and scaling relations. We find that the modelled galaxy clusters are generally in reasonable agreement with observations with respect to baryonic fractions and gas scaling relations at redshift z = 0. However, there are still some (model-dependent) differences, such as central galaxies being too massive, and galaxy colours (g − r) being bluer (about 0.2 dex lower at the peak position) than in observations. The agreement in gas scaling relations down to 1013 h−1M⊙ between the simulations indicates that particulars of the sub-grid modelling of the baryonic physics only has a weak influence on these relations. We also include – where appropriate – a comparison to three semi-analytical galaxy formation models as applied to the same underlying dark matter only simulation. All simulations and derived data products are publicly available

TheThreeHundred Project: ram pressure and gas content of haloes and subhaloes in the phase-space plane

We use THETHREEHUNDRED project, a suite of 324 resimulated massive galaxy clusters embedded in a broad range of environments, to investigate (i) how the gas content of the surrounding haloes correlates with the phase-space position at z z = 0 and (ii) the role that ram pressure plays in this correlation. By stacking all 324 normalized phase-space planes containing 169 287 haloes and subhaloes, we show that the halo gas content is tightly correlated with the phase-space position. At ∼1.5--2R 200 ∼1.5--2R200 of the cluster dark matter halo, we find an extremely steep decline in the halo gas content of infalling haloes and subhaloes irrespective of cluster mass, possibly indicating the presence of an accretion shock. We also find that subhaloes are particularly gas-poor, even in the cluster outskirts, which could indicate active regions of ongoing pre-processing. By modelling the instantaneous ram pressure experienced by each halo and subhalo at z z = 0, we show that the ram pressure intensity is also well correlated with the phase-space position, which is again irrespective of cluster mass. In fact, we show that regions in the phase-space plane with high differential velocity between a halo or subhalo and its local gas environment are almost mutually exclusive with high halo gas content regions. This suggests a causal link between the gas content of objects and the instantaneous ram pressure they experience, where the dominant factor is the differential velocity