Publications (81)
AGN host galaxies at redshift z~0.7: peculiar or not?
Asmus Boehm, Lutz Wisotzki, Eric F. Bell +21
We perform a quantitative morphological comparison between the hosts of Active Galactic Nuclei (AGN) and quiescent galaxies at intermediate redshifts (z~0.7). The imaging data are…
Multipole expansion for HI intensity mapping experiments: simulations and modelling
Steven Cunnington, Alkistis Pourtsidou, Paula S. Soares +2
We present a framework and an open-source python toolkit to analyse the 2-point statistics of 3D fluctuations in the context of HI intensity maps using the multipole expansion form…
The e-MERLIN Galaxy Evolution Survey (e-MERGE): Overview and Survey Description
T. W. B. Muxlow, A. P. Thomson, J. F. Radcliffe +37
We present an overview and description of the eMERLIN Galaxy Evolution survey (eMERGE) Data Release 1 (DR1), a large program of high-resolution 1.5 GHz radio observations of the GO…
Learning from the machine: interpreting machine learning algorithms for point- and extended- source classification
Xan Morice-Atkinson, Ben Hoyle, David Bacon
We investigate star-galaxy classification for astronomical surveys in the context of four methods enabling the interpretation of black-box machine learning systems. The first is ou…
Raytracing simulations of coupled dark energy models
Francesco Pace, Marco Baldi, Lauro Moscardini +2
Dark matter and dark energy are usually assumed to couple only gravitationally. An extension to this picture is to model dark energy as a scalar field coupled directly to cold dark…
The STAGES view of red spirals and dusty red galaxies: Mass-dependent quenching of star-formation in cluster infall
Christian Wolf, Alfonso Aragon-Salamanca, Michael Balogh +22
We investigate the properties of optically passive spirals and dusty red galaxies in the A901/2 cluster complex at redshift ~0.17 using restframe near-UV-optical SEDs, 24 micron IR…
Impact of local structure on the cosmic radio dipole
Matthias Rubart, David Bacon, Dominik J. Schwarz
We investigate the contribution that a local over- or under-density can have on linear cosmic dipole estimations. We focus here on radio surveys, such as the NRAO VLA Sky Survey (N…
Shapelets: II. A Method for Weak Lensing Measurements
Alexandre Refregier, David Bacon
Weak gravitational lensing provides a unique method to directly measure the distribution of mass in the universe. Because the distortions induced by lensing in the shape of backgro…
Cosmic Shear with Keck: Systematic Effects
Richard Massey, David Bacon, Alexandre Refregier +1
Cosmic shear probes the distribution of dark matter via gravitational lensing of distant, background galaxies. We describe our cosmic shear survey consisting of deep blank fields o…
Dark Energy Survey Year 1 Results: Cosmological Constraints from Cluster Abundances and Weak Lensing
DES Collaboration, Tim Abbott, Michel Aguena +129
We perform a joint analysis of the counts and weak lensing signal of redMaPPer clusters selected from the Dark Energy Survey (DES) Year 1 dataset. Our analysis uses the same shear…
Core or cusps: The central dark matter profile of a redshift one strong lensing cluster with a bright central image
Thomas E. Collett, Elizabeth Buckley-Geer, Huan Lin +58
We report on SPT-CLJ2011-5228, a giant system of arcs created by a cluster at . The arc system is notable for the presence of a bright central image. The source is a Lyman…
Protecting Quantum Information Encoded in Decoherence Free States Against Exchange Errors
Daniel A. Lidar, David Bacon, Julia Kempe +1
The exchange interaction between identical qubits in a quantum information processor gives rise to unitary two-qubit errors. It is shown here that decoherence free subspaces (DFSs)…
Observing the earliest moments of supernovae using strong gravitational lenses
Max Foxley-Marrable, Thomas E. Collett, Chris Frohmaier +4
We determine the viability of exploiting lensing time delays to observe strongly gravitationally lensed supernovae (gLSNe) from first light. Assuming a plausible discovery strategy…
Shapelets "multiple multipole" shear measurement methods
Richard Massey, Alexandre Refregier, David Bacon
The measurement of weak gravitational lensing is currently limited to a precision of ~10% by instabilities in galaxy shape measurement techniques and uncertainties in their calibra…
Anti-lensing: the bright side of voids
Krzysztof Bolejko, Chris Clarkson, Roy Maartens +3
More than half of the volume of our Universe is occupied by cosmic voids. The lensing magnification effect from those under-dense regions is generally thought to give a small dimmi…
Weak Lensing from Space III: Cosmological Parameters
Alexandre Refregier, Richard Massey, Jason Rhodes +6
Weak gravitational lensing provides a unique method to directly map the dark matter in the universe and measure cosmological parameters. Current weak lensing surveys are limited by…
Numerical Simulations of Weak Lensing Measurements
David Bacon, Alexandre Refregier, Douglas Clowe +1
(Abridged) Weak gravitational lensing induces distortions on the images of background galaxies, and thus provides a direct measure of mass fluctuations in the universe. Since the d…
The feasibility of weak lensing and 21cm intensity mapping cross-correlation measurements
Anut Sangka, David Bacon
One of the most promising probes to complement current standard cosmological surveys is the HI intensity map, i.e. the distribution of temperature fluctuations in neutral hydrogen.…
Cosmology with Superluminous Supernovae
Dario Scovacricchi, Robert C. Nichol, David Bacon +2
We predict cosmological constraints for forthcoming surveys using Superluminous Supernovae (SLSNe) as standardisable candles. Due to their high peak luminosity, these events can be…
Reconstructing the velocity field beyond the local universe
Russell Johnston, David Bacon, Luis F. A. Teodoro +3
We present a maximum probability approach to reconstructing spatial maps of the peculiar velocity field at redshifts , where the velocities have been measured from distan…
Joint Cosmic Shear Measurements with the Keck and William Herschel Telescopes
David Bacon, Richard Massey, Alexandre Refregier +1
The recent measurements of weak lensing by large-scale structure present significant new opportunities for studies of the matter distribution in the universe. Here, we present a ne…
Weak Lensing Simulations for the SKA
Prina Patel, Ian Harrison, Sphesihle Makhathini +6
Weak gravitational lensing measurements are traditionally made at optical wavelengths where many highly resolved galaxy images are readily available. However, the Square Kilometre…
Relativistic corrections and non-Gaussianity in radio continuum surveys
Roy Maartens, Gong-Bo Zhao, David Bacon +2
Forthcoming radio continuum surveys will cover large volumes of the observable Universe and will reach to high redshifts, making them potentially powerful probes of dark energy, mo…
The effect of quasar redshift errors on Lyman- forest correlation functions
Samantha Youles, Julian E. Bautista, Andreu Font-Ribera +30
Using synthetic Lyman- forests from the Dark Energy Spectroscopic Instrument (DESI) survey, we present a study of the impact of errors in the estimation of quasar redshift on t…
Detection of Cosmic Shear with the William Herschel Telescope
David Bacon, Alexandre Refregier, Richard Ellis
Gravitational lensing by large-scale structure induces weak coherent alignments in the shapes of background galaxies. Here we present evidence for the detection of this `cosmic she…
Less than 10 percent of star formation in z=0.6 massive galaxies is triggered by major interactions
Aday R. Robaina, Eric F. Bell, Rosalind E. Skelton +26
Both observations and simulations show that major tidal interactions or mergers between gas-rich galaxies can lead to intense bursts of starformation. Yet, the average enhancement…
Prospects for clustering and lensing measurements with forthcoming intensity mapping and optical surveys
Alkistis Pourtsidou, David Bacon, Robert Crittenden +1
We explore the potential of using intensity mapping surveys (MeerKAT, SKA) and optical galaxy surveys (DES, LSST) to detect HI clustering and weak gravitational lensing of 21cm emi…
Light bending by the cosmological constant
Lingyi Hu, Alan Heavens, David Bacon
We revisit the question of whether the cosmological constant affects the cosmological gravitational bending of light, by numerical integration of the geodesic equations for a…
Measuring redshift-space distortions with future SKA surveys
Alvise Raccanelli, Philip Bull, Stefano Camera +8
The peculiar motion of galaxies can be a particularly sensitive probe of gravitational collapse. As such, it can be used to measure the dynamics of dark matter and dark energy as w…
Testing General Relativity with the Doppler magnification effect
Sambatra Andrianomena, Camille Bonvin, David Bacon +4
The apparent sizes and brightnesses of galaxies are correlated in a dipolar pattern around matter overdensities in redshift space, appearing larger on their near side and smaller o…
Testing the speed of gravitational waves over cosmological distances with strong gravitational lensing
Thomas E. Collett, David Bacon
Probing the relative speeds of gravitational waves and light acts as an important test of General Relativity and alternative theories of gravity. Measuring the arrival time of grav…
Delensing Gravitational Wave Standard Sirens with Shear and Flexion Maps
Charles Shapiro, David Bacon, Martin Hendry +1
Supermassive black hole binary systems (SMBHB) are standard sirens -- the gravitational wave analogue of standard candles -- and if discovered by gravitational wave detectors, they…
Impact of Relativistic Effects on the Primordial Non-Gaussianity Signature in the Large-Scale Clustering of Quasars
Mike Shengbo Wang, Florian Beutler, David Bacon
Relativistic effects in clustering observations have been shown to introduce scale-dependent corrections to the galaxy over-density field on large scales, which may hamper the dete…
Unbiased contaminant removal for 3D galaxy power spectrum measurements
Benedict Bahr-Kalus, Will J Percival, David Bacon +1
We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contamin…
Simulation tests of galaxy cluster constraints on chameleon gravity
Harry Wilcox, Robert C. Nichol, Gong-bo Zhao +3
We use two new hydrodynamical simulations of CDM and gravity to test the methodology used by Wilcox et al. 2015 (W15) in constraining the effects of a fifth force on the…
Testing foundations of modern cosmology with SKA all-sky surveys
Dominik J. Schwarz, David Bacon, Song Chen +7
Continuum and HI surveys with the Square Kilometre Array (SKA) will allow us to probe some of the most fundamental assumptions of modern cosmology, including the Cosmological Princ…
Weak Lensing from Space II: Dark Matter Mapping
Richard Massey, Jason Rhodes, Alexandre Refregier +8
We study the accuracy with which weak lensing measurements could be made from a future space-based survey, predicting the subsequent precisions of 3-dimensional dark matter maps, p…
HI Intensity Mapping for Clustering-Based Redshift Estimation
Steven Cunnington, Ian Harrison, Alkistis Pourtsidou +1
Precision cosmology requires accurate galaxy redshifts, but next generation optical surveys will observe unprecedented numbers of resolved galaxies, placing strain on the amount of…
Cosmology with SKA Radio Continuum Surveys
Matt J. Jarvis, David Bacon, Chris Blake +5
Radio continuum surveys have, in the past, been of restricted use in cosmology. Most studies have concentrated on cross-correlations with the cosmic microwave background to detect…
MeerKLASS: MeerKAT Large Area Synoptic Survey
Mario G. Santos, Michelle Cluver, Matt Hilton +35
We discuss the ground-breaking science that will be possible with a wide area survey, using the MeerKAT telescope, known as MeerKLASS (MeerKAT Large Area Synoptic Survey). The curr…
Euclid & SKA Synergies
Thomas D. Kitching, David Bacon, Michael L. Brown +7
Over the past few years two of the largest and highest fidelity experiments conceived have been approved for construction: Euclid is an ESA M-Class mission that will map three-quar…
The Dark Energy Survey Supernova Program results: Type Ia Supernova brightness correlates with host galaxy dust
Cole Meldorf, Antonella Palmese, Dillon Brout +68
Cosmological analyses with type Ia supernovae (SNe Ia) often assume a single empirical relation between color and luminosity () and do not account for varying host-galaxy dust…
HI constraints from the cross-correlation of eBOSS galaxies and Green Bank Telescope intensity maps
Laura Wolz, Alkistis Pourtsidou, Kiyoshi W. Masui +18
We present the joint analysis of Neutral Hydrogen (HI) Intensity Mapping observations with three galaxy samples: the Luminous Red Galaxy (LRG) and Emission Line Galaxy (ELG) sample…
OzDES Reverberation Mapping Program: Lag recovery reliability for 6-year CIV analysis
Andrew Penton, Umang Malik, Tamara Davis +66
We present the statistical methods that have been developed to analyse the OzDES reverberation mapping sample. To perform this statistical analysis we have created a suite of custo…
Dipolar modulation in the size of galaxies: The effect of Doppler magnification
Camille Bonvin, Sambatra Andrianomena, David Bacon +4
Objects falling into an overdensity appear larger on its near side and smaller on its far side than other objects at the same redshift. This produces a dipolar pattern of magnifica…
A precise extragalactic test of General Relativity
Thomas E. Collett, Lindsay J. Oldham, Russell J. Smith +7
Einstein's theory of gravity, General Relativity, has been precisely tested on Solar System scales, but the long-range nature of gravity is still poorly constrained. The nearby str…
Dark matter maps reveal cosmic scaffolding
Richard Massey, Jason Rhodes, Richard Ellis +17
Ordinary baryonic particles (such as protons and neutrons) account for only one-sixth of the total matter in the Universe. The remainder is a mysterious "dark matter" component, wh…
Shapelets: A New Method to Measure Galaxy Shapes
Alexandre Refregier, Tzu-Ching Chang, David Bacon
We present a new approach to measure the shapes of galaxies, a fundamental task in observational astronomy. This approach is based on the decomposition of a galaxy image into a ser…
STAGES: the Space Telescope A901/2 Galaxy Evolution Survey
M. E. Gray, Christian Wolf, Marco Barden +26
We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution ac…
The effects of velocities and lensing on moments of the Hubble diagram
Edward Macaulay, Tamara M. Davis, Dario Scovacricchi +3
We consider the dispersion on the supernova distance-redshift relation due to peculiar velocities and gravitational lensing, and the sensitivity of these effects to the amplitude o…
Model-independent constraints on dark energy and modified gravity with the SKA
Gong-Bo Zhao, David Bacon, Roy Maartens +2
Employing a nonparametric approach of the principal component analysis (PCA), we forecast the future constraint on the equation of state of dark energy, and on the effective…
The dark matter environment of the Abell 901/902 supercluster: a weak lensing analysis of the HST STAGES survey
Catherine Heymans, Meghan E. Gray, Chien Y. Peng +21
We present a high resolution dark matter reconstruction of the z=0.165 Abell 901/902 supercluster from a weak lensing analysis of the HST STAGES survey. We detect the four main str…
Brightest Cluster Galaxy ellipticity as proxy for halo shape: Orientation bias, assembly bias, and potential selection effects in SZ-selected clusters
Radhakrishnan Srinivasan, Tae-hyeon Shin, Anja von der Linden +93
The orientation of triaxial galaxy clusters with respect to the line-of-sight is expected to be one of the prime sources of scatter and potential bias in optical observables (e.g.,…
Impact of Foregrounds on HI Intensity Mapping Cross-Correlations with Optical Surveys
Steven Cunnington, Laura Wolz, Alkistis Pourtsidou +1
The future of precision cosmology could benefit from cross-correlations between intensity maps of unresolved neutral hydrogen (HI) and more conventional optical galaxy surveys. A m…
Obtaining non-linear galaxy bias constraints from galaxy-lensing phase differences
Marc Manera, David Bacon
We demonstrate the utility and constraining power of a new statistic for investigating galaxy bias: the galaxy-lensing phase difference. The statistic consists in taking the differ…
A new consistency test for CDM cosmology using galaxy surveys
Jinglan Zheng, Gong-Bo Zhao, Yuting Wang +6
We propose a new consistency test for the CDM cosmology using baryonic acoustic oscillations (BAO) and redshift space distortion (RSD) measurements from galaxy redshift surveys…
The Shear TEsting Programme 1: Weak lensing analysis of simulated ground-based observations
Catherine Heymans, Ludovic Van Waerbeke, David Bacon +22
The Shear TEsting Programme, STEP, is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wid…
Optically-passive spirals: The missing link in gradual star formation suppression upon cluster infall
Christian Wolf, Alfonso Aragón-Salamanca, Michael Balogh +22
Galaxies migrate from the blue cloud to the red sequence when their star formation is quenched. Here, we report on galaxies quenched by environmental effects and not by mergers or…
Cosmological constraints on early dark energy from the full shape analysis of eBOSS DR16
Rafaela Gsponer, Ruiyang Zhao, Jamie Donald-McCann +5
We evaluate the effectiveness of Early Dark Energy (EDE) in addressing the Hubble tension using data from the completed eBOSS survey, focusing on luminous red galaxies (LRGs), quas…
Probing the Cosmic Dark Ages with the Lunar Crater Radio Telescope
Ashish Goel, Saptarshi Bandyopadhyay, Joseph Lazio +17
The Cosmic Dark Ages represent the period in the early evolution of the Universe, starting immediately after the decoupling of CMB photons from matter, and ending with the formatio…
Cross-correlation cosmography with HI intensity mapping
Alkistis Pourtsidou, David Bacon, Robert Crittenden
The cross-correlation of a foreground density field with two different background convergence fields can be used to measure cosmographic distance ratios and constrain dark energy p…
Cosmology and Fundamental Physics with the Euclid Satellite
Luca Amendola, Stephen Appleby, Anastasios Avgoustidis +69
Euclid is a European Space Agency medium class mission selected for launch in 2020 within the Cosmic Vision 2015 2025 program. The main goal of Euclid is to understand the origin o…
The Gravitational Lensing Imprints of DES Y3 Superstructures on the CMB: A Matched Filtering Approach
Umut Demirbozan, Seshadri Nadathur, Ismael Ferrero +63
Low density cosmic voids gravitationally lens the cosmic microwave background (CMB), leaving a negative imprint on the CMB convergence . This effect provides insight into th…
Flexion measurement in simulations of Hubble Space Telescope data
Barnaby Rowe, David Bacon, Richard Massey +5
We present a simulation analysis of weak gravitational lensing flexion and shear measurement using shapelet decomposition, and identify differences between flexion and shear measur…
Full-sky weak lensing: a nonlinear post-Friedmann treatment
Hedda A. Gressel, Camille Bonvin, Marco Bruni +1
We present a full-sky derivation of weak lensing observables in the Post-Friedmann (PF) formalism. Weak lensing has the characteristic of mixing small scales and large scales since…
The Impact of Microlensing on the Standardisation of Strongly Lensed Type Ia Supernovae
Max Foxley-Marrable, Thomas E. Collett, Georgios Vernardos +2
We investigate the effect of microlensing on the standardisation of strongly lensed Type Ia supernovae (GLSNe Ia). We present predictions for the amount of scatter induced by micro…
A multitracer analysis for the eBOSS galaxy sample based on the effective field theory of large-scale structure
Ruiyang Zhao, Xiaoyong Mu, Rafaela Gsponer +8
We perform a multitracer full-shape analysis in Fourier space based on the effective field theory of large-scale structure (EFTofLSS) using the complete Sloan Digital Sky Survey IV…
Testing Emergent Gravity on Galaxy Cluster Scales
Andrius Tamosiunas, David Bacon, Kazuya Koyama +1
Verlinde's theory of Emergent Gravity (EG) describes gravity as an emergent phenomenon rather than a fundamental force. Applying this reasoning in de Sitter space leads to gravity…
The XMM Cluster Survey: Testing chameleon gravity using the profiles of clusters
Harry Wilcox, David Bacon, Robert C. Nichol +17
The chameleon gravity model postulates the existence of a scalar field that couples with matter to mediate a fifth force. If it exists, this fifth force would influence the hot X-r…
Search for strongly lensed counterpart images of binary black hole mergers in the first two LIGO observing runs
Connor McIsaac, David Keitel, Thomas Collett +4
Strong gravitational lensing can produce multiple images of the same gravitational-wave signal, each arriving at different times and with different magnification. Previous work has…
Cosmology from LOFAR Two-metre Sky Survey Data Release 2: Cross-correlations with luminous red galaxies from eBOSS
Jinglan Zheng, Prabhakar Tiwari, Gong-Bo Zhao +7
We cross-correlated galaxies from the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) second data release (DR2) radio source with the extended Baryon Oscillation Spectrosc…
Testing Gravity Using Galaxy Clusters: New Constraints on Beyond Horndeski Theories
Jeremy Sakstein, Harry Wilcox, David Bacon +2
The Beyond Horndeski class of alternative gravity theories allow for Self-accelerating de-Sitter cosmologies with no need for a cosmological constant. This makes them viable altern…
Detection of Weak Gravitational Lensing by Large-scale Structure
David Bacon, Alexandre Refregier, Richard Ellis
We report a detection of the coherent distortion of faint galaxies arising from gravitational lensing by foreground structures. This ``cosmic shear'' is potentially the most direct…
Probing galaxy evolution in massive clusters using ACT and DES: splashback as a cosmic clock
Susmita Adhikari, Tae-hyeon Shin, Bhuvnesh Jain +113
We measure the projected number density profiles of galaxies and the splashback feature in clusters selected by the Sunyaev--Zeldovich (SZ) effect from the Advanced Atacama Cosmolo…
Complementarity of Weak Lensing and Peculiar Velocity Measurements in Testing General Relativity
Yong-Seon Song, Gong-Bo Zhao, David Bacon +3
We explore the complementarity of weak lensing and galaxy peculiar velocity measurements to better constrain modifications to General Relativity. We find no evidence for deviations…
Cosmology and fundamental physics with the Euclid satellite
Luca Amendola, Stephen Appleby, David Bacon +60
Euclid is a European Space Agency medium class mission selected for launch in 2019 within the Cosmic Vision 2015-2025 programme. The main goal of Euclid is to understand the origin…
Synergy between the Large Synoptic Survey Telescope and the Square Kilometre Array
David Bacon, Sarah Bridle, Filipe B. Abdalla +18
We provide an overview of the science benefits of combining information from the Square Kilometre Array (SKA) and the Large Synoptic Survey Telescope (LSST). We first summarise the…
Cosmology with the Laser Interferometer Space Antenna
Pierre Auclair, David Bacon, Tessa Baker +177
The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate of the universe, and to understand stochastic gravita…
HI and cosmological constraints from intensity mapping, optical, and CMB surveys
Alkistis Pourtsidou, David Bacon, Robert Crittenden
We forecast constraints on neutral hydrogen (HI) and cosmological parameters using near-term intensity mapping surveys with instruments such as BINGO, MeerKAT, and the SKA, and Sta…
Galaxy power spectrum and biasing results from the LOFAR Two-metre Sky Survey (first data release)
Prabhakar Tiwari, Ruiyang Zhao, Jinglan Zheng +3
The LOFAR Two-metre Sky Survey (LoTSS) is an ongoing survey aiming to observe the entire Northern sky, providing an excellent opportunity to study the distribution and evolution of…
Testing chameleon gravity with the Coma cluster
Ayumu Terukina, Lucas Lombriser, Kazuhiro Yamamoto +3
We propose a novel method to test the gravitational interactions in the outskirts of galaxy clusters. When gravity is modified, this is typically accompanied by the introduction of…