Institution
Institute of Cosmology and Gravitation, University of Portsmouth
About: Institute of Cosmology and Gravitation, University of Portsmouth is a based out in . It is known for research contribution in the topics: Galaxy & Redshift. The organization has 297 authors who have published 1207 publications receiving 76919 citations.
Topics: Galaxy, Redshift, Dark energy, Dark matter, Cosmic microwave background
Papers published on a yearly basis
Papers
More filters
••
Ohio State University1, Autonomous University of Barcelona2, University College London3, University of Manchester4, Institut de Ciències de l'Espai5, Stanford University6, Brookhaven National Laboratory7, Rhodes University8, Fermilab9, University of Cambridge10, Institut d'Astrophysique de Paris11, University of Illinois at Urbana–Champaign12, National Center for Supercomputing Applications13, Institute of Cosmology and Gravitation, University of Portsmouth14, Texas A&M University15, Ludwig Maximilian University of Munich16, California Institute of Technology17, University of Pennsylvania18, University of Michigan19, University of Chicago20, Max Planck Society21, Australian Astronomical Observatory22, University of São Paulo23, Catalan Institution for Research and Advanced Studies24, Argonne National Laboratory25
TL;DR: In this paper, a new measurement method is proposed to minimize the wastage of data for any class of stars or galaxies detectable in an imaging survey, which can be used to estimate the number of stars and galaxies in the sky.
Abstract: Accurate statistical measurement with large imaging surveys has traditionally required throwing away a sizable fraction of the data. This is because most measurements have have relied on selecting nearly complete samples, where variations in the composition of the galaxy population with seeing, depth, or other survey characteristics are small. We introduce a new measurement method that aims to minimize this wastage, allowing precision measurement for any class of stars or galaxies detectable in an imaging survey. We have implemented our proposal in Balrog, a software package which embeds fake objects in real imaging in order to accurately characterize measurement biases. We also demonstrate this technique with an angular clustering measurement using Dark Energy Survey (DES) data. We first show that recovery of our injected galaxies depends on a wide variety of survey characteristics in the same way as the real data. We then construct a flux-limited sample of the faintest galaxies in DES, chosen specifically for their sensitivity to depth and seeing variations. Using the synthetic galaxies as randoms in the standard LandySzalay correlation function estimator suppresses the effects of variable survey selection by at least two orders of magnitude. Now our measured angular clustering is found to be inmore » excellent agreement with that of a matched sample drawn from much deeper, higherresolution space-based COSMOS imaging; over angular scales of 0.004° < θ < 0.2 ° , we find a best-fit scaling amplitude between the DES and COSMOS measurements of 1.00 ± 0.09. We expect this methodology to be broadly useful for extending the statistical reach of measurements in a wide variety of coming imaging surveys.« less
79 citations
••
TL;DR: In this article, it was shown that for a large class of generalized Randall-Sundrum type II models the characterization of the brane-gravity sector by the effective Einstein equation, Codazzi equation and the twice-contracted Gauss equation is equivalent to the bulk Einstein equation.
Abstract: We prove that for a large class of generalized Randall-Sundrum type II models the characterization of the brane-gravity sector by the effective Einstein equation, Codazzi equation and the twice-contracted Gauss equation is equivalent to the bulk Einstein equation. We give the complete set of equations in the generic case of non-${Z}_{2}$-symmetric bulk and arbitrary energy-momentum tensors both on the brane and in the bulk. Among these, the effective Einstein equation contains a varying cosmological ``constant'' and two new source terms. The first of these represents the deviation from ${Z}_{2}$ symmetry, while the second arises from the bulk energy-momentum tensor. We apply the formalism for the case of a perfect fluid on a Friedmann brane embedded in a generic bulk. The generalized Friedmann and Raychaudhuri equations are given in a form independent of both the embedding and the bulk matter. They contain two new functions obeying a first order differential system, both depending on the bulk matter and the embedding. Then we focus on Friedmann branes separating two nonidentical (inner or outer) regions of Reissner--Nordstr\"om--anti-de Sitter bulk space-times, generalizing previous non-${Z}_{2}$-symmetric treatments. Finally the analysis is repeated for the Vaidya--anti-de Sitter bulk space-time, allowing for both ingoing and outgoing radiation in each region.
79 citations
••
TL;DR: In this article, the authors investigated the properties of the 2-point galaxy correlation function at very large scales, including all geometric and local relativistic effects, including wide-angle effects, redshift space distortions, Doppler terms and Sachs-Wolfe type terms in the gravitational potentials.
Abstract: We investigate the properties of the 2-point galaxy correlation function at very large scales, including all geometric and local relativistic effects --- wide-angle effects, redshift space distortions, Doppler terms and Sachs-Wolfe type terms in the gravitational potentials. The general three-dimensional correlation function has a nonzero dipole and octupole, in addition to the even multipoles of the flat-sky limit. We study how corrections due to primordial non-Gaussianity and General Relativity affect the multipolar expansion, and we show that they are of similar magnitude (when f_(NL) is small), so that a relativistic approach is needed. Furthermore, we look at how large-scale corrections depend on the model for the growth rate in the context of modified gravity, and we discuss how a modified growth can affect the non-Gaussian signal in the multipoles.
78 citations
••
TL;DR: It is found that magnetic fields generated during inflation can indeed produce the required B mode, for a suitable range of energy scales of inflation, and vector and tensor modes from primordial magnetic fields can explain the signal.
Abstract: If the B-mode signal in the cosmic microwave background polarization seen by the BICEP2 experiment is confirmed, it has dramatic implications for models of inflation. The result is also in tension with Planck limits on standard inflationary models. It is, therefore, important to investigate whether this signal can arise from alternative sources. If so, this could lessen the pressure on inflationary models and the tension with Planck data. We investigate whether vector and tensor modes from primordial magnetic fields can explain the signal. We find that, in principle, magnetic fields generated during inflation can indeed produce the required B mode, for a suitable range of energy scales of inflation. In this case, the primordial gravitational wave amplitude is negligible, so that there is no tension with Planck and no problems posed for current inflationary models. However, the simplest magnetic model is in tension with Planck limits on non-Gaussianity in the trispectrum. It may be possible to fine tune the magnetogenesis model so that this non-Gaussianity is suppressed. Alternatively, a weaker magnetic field can pass the non-Gaussianity constraints and allow the primordial tensor mode to be reduced to r ≃ 0.09, thus removing the tension with Planck data and alleviating the problems with simple inflationary models.
78 citations
••
TL;DR: In this paper, the weak-field limit of general relativity has been interpreted in terms of the weak field limit of the Newtonian motion gauge, allowing the inclusion of radiation perturbations and the non-linear evolution of matter.
Abstract: We show how standard Newtonian N-body simulations can be interpreted in terms of the weak-field limit of general relativity by employing the recently developed Newtonian motion gauge. Our framework allows the inclusion of radiation perturbations and the non-linear evolution of matter. We show how to construct the weak-field metric by combining Newtonian simulations with results from Einstein-Boltzmann codes. We discuss observational effects on weak lensing and ray tracing, identifying important relativistic corrections.
78 citations
Authors
Showing all 297 results
Name | H-index | Papers | Citations |
---|---|---|---|
Robert C. Nichol | 187 | 851 | 162994 |
Daniel Thomas | 134 | 846 | 84224 |
Will J. Percival | 129 | 473 | 87752 |
Tommaso Treu | 126 | 715 | 49090 |
Claudia Maraston | 103 | 362 | 59178 |
Marco Cavaglia | 93 | 372 | 60157 |
Ashley J. Ross | 90 | 248 | 46395 |
David A. Wake | 89 | 214 | 46124 |
László Á. Gergely | 89 | 426 | 60674 |
L. K. Nuttall | 89 | 253 | 54834 |
Rita Tojeiro | 87 | 229 | 43140 |
Roy Maartens | 86 | 432 | 23747 |
David Keitel | 85 | 253 | 56849 |
Davide Pietrobon | 83 | 152 | 62010 |
Gong-Bo Zhao | 81 | 287 | 35540 |