Publications (30)
Comparison of Polarized Radiative Transfer Codes used by the EHT Collaboration
Ben S. Prather, Cora Prather, Jason Dexter +271
Interpretation of resolved polarized images of black holes by the Event Horizon Telescope (EHT) requires predictions of the polarized emission observable by an Earth-based instrume…
The Formation of Submillimetre-Bright Galaxies from Gas Infall over a Billion Years
Desika Narayanan, Matthew Turk, Robert Feldmann +7
Submillimetre-luminous galaxies at high-redshift are the most luminous, heavily star-forming galaxies in the Universe, and are characterised by prodigious emission in the far-infra…
Dynamics and geometry of the inner sub-parsec-scale jet in 3C 279 observed with the Event Horizon Telescope
Hendrik Mueller, Sebastiano D. von Fellenberg, Ai-Ling Zeng +275
The 2021 Event Horizon Telescope observations resolve the innermost jet region of the blazar 3C279 with unprecedented detail. The reconstructed images consistently reveal a compact…
Concerning the Feasibility of Example-driven Modelling Techniques
Simon R. Thorne, David Ball, Z. Lawson
We report on a series of experiments concerning the feasibility of example driven modelling. The main aim was to establish experimentally within an academic environment: the relati…
Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole
Dimitrios Psaltis, Lia Medeiros, Pierre Christian +185
The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new…
The Mechanism of Electron Injection and Acceleration in Trans-Relativistic Reconnection
David Ball, Lorenzo Sironi, Feryal Ãzel
Electron acceleration during magnetic reconnection is thought to play a key role in time-variable high-energy emission from astrophysical systems. By means of particle-in-cell simu…
The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows
David Ball, Feryal Ãzel, Dimitrios Psaltis +2
Non-ideal MHD effects may play a significant role in determining the dynamics, thermal properties, and observational signatures of radiatively inefficient accretion flows onto blac…
Categorisation of Spreadsheet Use within Organisations, Incorporating Risk: A Progress Report
Mukul Madahar, Pat Cleary, David Ball
There has been a significant amount of research into spreadsheets over the last two decades. Errors in spreadsheets are well documented. Once used mainly for simple functions such…
Constraints on black-hole charges with the 2017 EHT observations of M87*
Prashant Kocherlakota, Luciano Rezzolla, Heino Falcke +234
Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M8…
Considering Functional Spreadsheet Operator Usage Suggests the Value of Example Driven Modelling for Decision Support Systems
Simon Thorne, David Ball
Most spreadsheet surveys both for reporting use and error focus on the practical application of the spreadsheet in a particular industry. Typically these studies will illustrate th…
A Plasmoid Model for the Sgr A* Flares Observed with GRAVITY and Chandra
David Ball, Feryal Ãzel, Pierre Christian +2
The Galactic Center black hole Sgr A* shows significant variability and flares in the submillimeter, infrared, and X-ray wavelengths. Owing to its exquisite resolution in the IR ba…
Event Horizon Telescope observations of the jet launching and collimation in Centaurus A
Michael Janssen, Heino Falcke, Matthias Kadler +236
Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimeter wavelengths have the power to reveal the launching and initial collimation region of e…
CAPE: Capability Achievement via Policy Execution
David Ball
Modern AI systems lack a way to express and enforce requirements. Pre-training produces intelligence, and post-training optimizes preferences, but neither guarantees that models re…
Locating the missing large-scale emission in the jet of M87* with short EHT baselines
Boris Georgiev, Paul Tiede, Sebastiano D. von Fellenberg +280
In Very-Long Baseline Interferometric arrays, nearly co-located stations probe the largest scales and typically cannot resolve the observed source. In the absence of large-scale st…
The Polarized Image of a Synchrotron Emitting Ring of Gas Orbiting a Black Hole
Ramesh Narayan, Daniel C. M. Palumbo, Michael D. Johnson +237
Synchrotron radiation from hot gas near a black hole results in a polarized image. The image polarization is determined by effects including the orientation of the magnetic field i…
Exploring Human Factors in Spreadsheet Development
Simon Thorne, David Ball
In this paper we consider human factors and their impact on spreadsheet development in strategic decision-making. This paper brings forward research from many disciplines both dire…
Empirical evidence for a global atmospheric temperature control system: physical structure
Mark Leggett, David Ball
There is evidence that a natural control system influences global atmospheric surface temperature (Leggett and Ball, 2020). The present paper sets up and tests a hypothesis concern…
Particle Acceleration and the Origin of X-ray Flares in GRMHD simulations of Sgr A*
David Ball, Feryal Ozel, Dimitrios Psaltis +1
Significant X-ray variability and flaring has been observed from Sgr A* but is poorly understood from a theoretical standpoint. We perform GRMHD simulations that take into account…
Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations
Saurabh, Hendrik Müller, Sebastiano D. von Fellenberg +282
We investigate the presence and spatial characteristics of the jet base emission in M87* at 230 GHz, enabled by the enhanced uv coverage in the 2021 Event Horizon Telescope (EHT) o…
A search for pulsars around Sgr A* in the first Event Horizon Telescope dataset
Pablo Torne, Kuo Liu, Ralph P. Eatough +282
The Event Horizon Telescope (EHT) observed in 2017 the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz (=1.3 mm). T…
Full-polarization millimeter wavelength variability of Sagittarius A* during the 2018 EHT campaign
Ezequiel Albentosa-Ruiz, Jasmin E. Washington, Nicola Marchili +272
Sagittarius A* (Srg A*), the supermassive black hole at the center of the Milky Way, provides a unique laboratory to study accretion dynamics and plasma processes near the event ho…
Ring Asymmetry and Spin in M87*
Vadim Bernshteyn, Nicholas S. Conroy, Michi Bauböck +263
Event Horizon Telescope (EHT) images of the supermassive black hole M87* depict an asymmetric ring of emission. General relativistic magnetohydrodynamic (GRMHD) models of M87* and…
Origin of the ring ellipticity in the black hole images of M87*
Rohan Dahale, Ilje Cho, Kotaro Moriyama +273
We investigate the origin of the elliptical ring structure observed in the images of the supermassive black hole M87*, aiming to disentangle contributions from gravitational, astro…
A Novel Approach to Formulae Production and Overconfidence Measurement to Reduce Risk in Spreadsheet Modelling
Simon Thorne, David Ball, Zoe Lawson
Research on formulae production in spreadsheets has established the practice as high risk yet unrecognised as such by industry. There are numerous software applications that are de…
Towards a Spreadsheet Engineering
V. R. Vemula, David Ball, Simon Thorne
In this paper, we report some on-going focused research, but are further keen to set it in the context of a proposed bigger picture, as follows. There is a certain depressing patte…
Electron and Proton Acceleration in Trans-Relativistic Magnetic Reconnection: Dependence on Plasma Beta and Magnetization
David Ball, Lorenzo Sironi, Feryal Ãzel
Non-thermal electron acceleration via magnetic reconnection is thought to play an important role in powering the variable X-ray emission from radiatively inefficient accretion flow…
Broadband multiwavelength properties of the archetypal blazar 3C 279 during the 2017 Event Horizon Telescope campaign
G. Principe, J. C. Algaba, E. Aviano +529
The archetypal blazar 3C 279 hosts a prominent relativistic jet and exhibits strong broadband variability across the electromagnetic spectrum. In April 2017, the Event Horizon Tele…
A multi-frequency study of sub-parsec jets with the Event Horizon Telescope
Jan Röder, Maciek Wielgus, Andrei P. Lobanov +287
The 2017 observing campaign of the Event Horizon Telescope (EHT) delivered the first very long baseline interferometry (VLBI) images at the observing frequency of 230 GHz, leading…
The putative center in NGC 1052
Anne-Kathrin Baczko, Matthias Kadler, Eduardo Ros +284
Many active galaxies harbor powerful relativistic jets, however, the detailed mechanisms of their formation and acceleration remain poorly understood. To investigate the area of je…
First Very Long Baseline Interferometry Detections at 870μm
Alexander W. Raymond, Sheperd S. Doeleman, Keiichi Asada +276
The first very long baseline interferometry (VLBI) detections at 870m wavelength (345GHz frequency) are reported, achieving the highest diffraction-limited angular resoluti…