ORCID Profile
0000-0002-1168-8299
Current Organisation
The University of Edinburgh
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Publisher: Oxford University Press (OUP)
Date: 11-03-2001
Publisher: Oxford University Press (OUP)
Date: 16-02-2011
Publisher: EDP Sciences
Date: 31-10-2012
Publisher: EDP Sciences
Date: 12-09-2006
Publisher: Oxford University Press (OUP)
Date: 17-08-2022
Abstract: We introduce preconditioned Monte Carlo (PMC), a novel Monte Carlo method for Bayesian inference that facilitates efficient s ling of probability distributions with non-trivial geometry. PMC utilizes a Normalizing Flow (NF) in order to decorrelate the parameters of the distribution and then proceeds by s ling from the preconditioned target distribution using an adaptive Sequential Monte Carlo (SMC) scheme. The results produced by PMC include s les from the posterior distribution and an estimate of the model evidence that can be used for parameter inference and model comparison, respectively. The aforementioned framework has been thoroughly tested in a variety of challenging target distributions achieving state-of-the-art s ling performance. In the cases of primordial feature analysis and gravitational wave inference, PMC is approximately 50 and 25 times faster, respectively, than nested s ling (NS). We found that in higher dimensional applications, the acceleration is even greater. Finally, PMC is directly parallelisable, manifesting linear scaling up to thousands of CPUs.
Publisher: Oxford University Press (OUP)
Date: 20-07-2016
Publisher: Oxford University Press (OUP)
Date: 06-04-2022
Abstract: We construct the halo mass function (HMF) from the GAMA (Galaxy And Mass Assembly) galaxy group catalogue over the mass range of 1012.7–1015.5 M⊙, and find good agreement with the expectation from Lambda cold dark matter. In comparison to previous studies, this result extends the mass range over which the HMF has now been measured over by an order of magnitude. We combine the GAMA data release (DR) 4 HMF with similar data from the Sloan Digital Sky Survey (SDSS) DR12 and REFLEX II (ROSAT-ESO Flux Limited X-ray Galaxy Cluster Survey) surveys, and fit a four-parameter Murray–Robotham–Power function, valid at $\\tilde{z} \\approx 0.1$, yielding a density normalization of log10 (ϕ* Mpc$^{3})= -3.96^{+0.55}_{-0.82}$, a high mass turnover of log10 (M* M$_{\\odot }^{-1})=14.13^{+0.43}_{-0.40}$, a low-mass power-law slope of $\\alpha =-1.68^{+0.21}_{-0.24}$, and a high-mass softening parameter of $\\beta =0.63^{+0.25}_{-0.11}$. If we fold in the constraint on ΩM from the Planck 2018 cosmology, we are able to reduce these uncertainties further, but this relies on the assumption that the power-law trend can be extrapolated from 1012.7 M⊙ to zero mass. Throughout, we highlight the effort needed to improve on our HMF measurement: improved halo mass estimates that do not rely on calibration to simulations reduced halo mass uncertainties needed to mitigate the strong Eddington bias that arises from the steepness of the HMF low-mass slope and deeper wider area spectroscopic surveys. To our halo mass limit of 1012.7 M⊙, we are directly resolving (‘seeing’) 41 ± 5 per cent of the total mass density, i.e. ΩM,& .7 = 0.128 ± 0.016, opening the door for the direct construction of three-dimensional dark matter mass maps at Mpc resolution.
Publisher: Oxford University Press (OUP)
Date: 22-10-2013
Publisher: Oxford University Press (OUP)
Date: 17-11-2017
Publisher: Oxford University Press (OUP)
Date: 10-03-2011
Publisher: The Open Journal
Date: 09-11-2022
DOI: 10.21105/JOSS.04634
Publisher: Oxford University Press (OUP)
Date: 18-11-2011
Publisher: EDP Sciences
Date: 26-03-2007
Publisher: Oxford University Press (OUP)
Date: 03-2011
Publisher: Oxford University Press (OUP)
Date: 21-03-2009
Publisher: Cambridge University Press (CUP)
Date: 12-2007
DOI: 10.1017/S1743921308024010
Abstract: Division VIII gathers astronomers engaged in the study of the visible and invisible matter in the Universe at large, from Local Group galaxies via distant galaxies and galaxy clusters to the large-scale structure of the Universe and the cosmic background radiation.
Publisher: Oxford University Press (OUP)
Date: 04-2004
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
Publisher: Cambridge University Press (CUP)
Date: 06-2014
DOI: 10.1017/S1743921316009753
Abstract: Our view of the low-redshift Cosmic Web has been revolutionized by galaxy redshift surveys such as 6dFGS, SDSS and 2MRS. However, the trade-off between depth and angular coverage limits a systematic three-dimensional account of the entire sky beyond the Local Volume ( z 0.05). In order to reliably map the Universe to cosmologically significant depths over the full celestial sphere, one must draw on multiwavelength datasets and state-of-the-art photometric redshift techniques. We have undertaken a dedicated program of cross-matching the largest photometric all-sky surveys – 2MASS, WISE and SuperCOSMOS – to obtain accurate redshift estimates of millions of galaxies. The first outcome of these efforts – the 2MASS Photometric Redshift catalog (2MPZ, Bilicki et al . 2014a) – has been publicly released and includes almost 1 million galaxies with a mean redshift of z =0.08. Here we summarize how this catalog was constructed and how using the WISE mid-infrared s le together with SuperCOSMOS optical data allows us to push to redshift shells of z ∼ 0.2 –0.3 on unprecedented angular scales. Our catalogs, with ∼ 20 million sources in total, provide access to cosmological volumes crucial for studies of local galaxy flows (clustering dipole, bulk flow) and cross-correlations with the cosmic microwave background such as the integrated Sachs-Wolfe effect or lensing studies.
Publisher: Oxford University Press (OUP)
Date: 19-08-2020
Abstract: Protoclusters, which will yield galaxy clusters at lower redshift, can provide valuable information on the formation of galaxy clusters. However, identifying progenitors of galaxy clusters in observations is not an easy task, especially at high redshift. Different priors have been used to estimate the overdense regions that are thought to mark the locations of protoclusters. In this paper, we use mimicked Ly α-emitting galaxies at z = 5.7 to identify protoclusters in the MultiDark galaxies, which are populated by applying three different semi-analytic models to the $1\\, h^{-1}\\, {\\rm Gpc}$ MultiDark Planck2 simulation. To compare with observational results, we extend the criterion 1 (a Ly α luminosity limited s le) to criterion 2 (a match to the observed mean galaxy number density). To further statistically study the finding efficiency of this method, we enlarge the identified protocluster s le (criterion 3) to about 3500 at z = 5.7 and study their final mass distribution. The number of overdense regions and their selection probability depends on the semi-analytic models and strongly on the three selection criteria (partly by design). The protoclusters identified with criterion 1 are associated with a typical final cluster mass of $2.82\\pm 0.92 \\times 10^{15} \\, \\rm {M_{\\odot }}$, which is in agreement with the prediction (within ±1σ) of an observed massive protocluster at z = 5.7. Identifying more protoclusters allows us to investigate the efficiency of this method, which is more suitable for identifying the most massive clusters: completeness ($\\mathbb {C}$) drops rapidly with decreasing halo mass. We further find that it is hard to have a high purity ($\\mathbb {P}$) and completeness simultaneously.
Publisher: Oxford University Press (OUP)
Date: 06-09-2022
Abstract: The relation between the integrated thermal Sunyaev–Zeldovich (tSZ) y-decrement versus halo mass (Y–M) can potentially constrain galaxy formation models, if theoretical and observational systematics can be properly assessed. We investigate the Y–M relation in the simba and IllustrisTNG-100 cosmological hydrodynamic simulations, quantifying the effects of feedback, line-of-sight projection, and beam convolution. We find that simba’s active galactic nucleus (AGN) jet feedback generates strong deviations from self-similar expectations for the Y–M relation, especially at $M_{\\rm 500}\\lesssim10^{13}M_\\odot$. In simba, this is driven by suppressed in-halo y contributions owing to lowered halo baryon fractions. IllustrisTNG results more closely resemble simba without jets. Projections of line-of-sight structures weaken these model differences slightly, but they remain significant – particularly at group and lower halo masses. In contrast, beam smearing at Planck resolution makes the models indistinguishable, and both models appear to agree well with Planck data down to the lowest masses probed. We show that the arcminute resolution expected from forthcoming facilities would retain the differences between model predictions, and thereby provide strong constraints on AGN feedback.
Publisher: Oxford University Press (OUP)
Date: 07-2008
Publisher: Oxford University Press (OUP)
Date: 20-05-2020
Abstract: Using the catalogues of galaxy clusters from The Three Hundred project, modelled with both hydrodynamic simulations (gadget-x and gadget-music), and semi-analytical models (SAMs), we study the scatter and self-similarity of the profiles and distributions of the baryonic components of the clusters: the stellar and gas mass, metallicity, the stellar age, gas temperature, and the (specific) star formation rate. Through comparisons with observational results, we find that the shape and the scatter of the gas density profiles matches well the observed trends including the reduced scatter at large radii which is a signature of self-similarity suggested in previous studies. One of our simulated sets, gadget-x, reproduces well the shape of the observed temperature profile, while gadget-music has a higher and flatter profile in the cluster centre and a lower and steeper profile at large radii. The gas metallicity profiles from both simulation sets, despite following the observed trend, have a relatively lower normalization. The cumulative stellar density profiles from SAMs are in better agreement with the observed result than both hydrodynamic simulations which show relatively higher profiles. The scatter in these physical profiles, especially in the cluster centre region, shows a dependence on the cluster dynamical state and on the cool-core/non-cool-core dichotomy. The stellar age, metallicity, and (s)SFR show very large scatter, which are then presented in 2D maps. We also do not find any clear radial dependence of these properties. However, the brightest central galaxies have distinguishable features compared to the properties of the satellite galaxies.
Publisher: Oxford University Press (OUP)
Date: 02-03-2022
Abstract: In Galaxy And Mass Assembly Data Release 4 (GAMA DR4), we make available our full spectroscopic redshift s le. This includes 248 682 galaxy spectra, and, in combination with earlier surveys, results in 330 542 redshifts across five sky regions covering ∼250 deg2. The redshift density, is the highest available over such a sustained area, has exceptionally high completeness (95 per cent to rKiDS = 19.65 mag), and is well-suited for the study of galaxy mergers, galaxy groups, and the low redshift (z & 0.25) galaxy population. DR4 includes 32 value-added tables or Data Management Units (DMUs) that provide a number of measured and derived data products including GALEX, ESO KiDS, ESO VIKING, WISE, and HerschelSpace Observatory imaging. Within this release, we provide visual morphologies for 15 330 galaxies to z & 0.08, photometric redshift estimates for all 18 million objects to rKiDS ∼ 25 mag, and stellar velocity dispersions for 111 830 galaxies. We conclude by deriving the total galaxy stellar mass function (GSMF) and its sub- ision by morphological class (elliptical, compact-bulge and disc, diffuse-bulge and disc, and disc only). This extends our previous measurement of the total GSMF down to 106.75 M$_{\\odot } \\, h_{70}^{-2}$ and we find a total stellar mass density of ρ* = (2.97 ± 0.04) × 108 M$_{\\odot } \\, h_{70}$ Mpc−3 or $\\Omega _*=(2.17 \\pm 0.03) \\times 10^{-3} \\, h_{70}^{-1}$. We conclude that at z & 0.1, the Universe has converted 4.9 ± 0.1 per cent of the baryonic mass implied by big bang Nucleosynthesis into stars that are gravitationally bound within the galaxy population.
Publisher: Oxford University Press (OUP)
Date: 07-1995
Publisher: Oxford University Press (OUP)
Date: 1994
Publisher: Oxford University Press (OUP)
Date: 02-2010
Publisher: Oxford University Press (OUP)
Date: 13-10-2015
Publisher: American Astronomical Society
Date: 13-07-2016
Publisher: Oxford University Press (OUP)
Date: 21-10-2023
Publisher: Oxford University Press (OUP)
Date: 05-10-2021
Abstract: We introduce zeus, a well-tested Python implementation of the Ensemble Slice S ling (ESS) method for Bayesian parameter inference. ESS is a novel Markov chain Monte Carlo (MCMC) algorithm specifically designed to tackle the computational challenges posed by modern astronomical and cosmological analyses. In particular, the method requires only minimal hand-tuning of 1−2 hyperparameters that are often trivial to set its performance is insensitive to linear correlations and it can scale up to 1000s of CPUs without any extra effort. Furthermore, its locally adaptive nature allows to s le efficiently even when strong non-linear correlations are present. Lastly, the method achieves a high performance even in strongly multimodal distributions in high dimensions. Compared to emcee, a popular MCMC s ler, zeus performs 9 and 29 times better in a cosmological and an exoplanet application, respectively.
Publisher: American Astronomical Society
Date: 04-02-2016
Publisher: Elsevier BV
Date: 07-2004
Publisher: Oxford University Press (OUP)
Date: 26-07-2011
Publisher: American Physical Society (APS)
Date: 27-01-2016
Publisher: IOP Publishing
Date: 07-2006
Publisher: Oxford University Press (OUP)
Date: 13-03-2015
DOI: 10.1093/MNRAS/STV237
Publisher: Oxford University Press (OUP)
Date: 03-08-2012
Publisher: Oxford University Press (OUP)
Date: 12-12-2011
Publisher: American Physical Society (APS)
Date: 17-08-2018
Publisher: Oxford University Press (OUP)
Date: 02-2012
Publisher: Oxford University Press (OUP)
Date: 04-07-2011
Publisher: American Astronomical Society
Date: 13-12-2013
Publisher: Oxford University Press (OUP)
Date: 14-06-2017
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/0004-6361/201834878
Abstract: We present a tomographic cosmic shear analysis of the Kilo-Degree Survey (KiDS) combined with the VISTA Kilo-Degree Infrared Galaxy Survey. This is the first time that a full optical to near-infrared data set has been used for a wide-field cosmological weak lensing experiment. This unprecedented data, spanning 450 deg 2 , allows us to significantly improve the estimation of photometric redshifts, such that we are able to include robustly higher-redshift sources for the lensing measurement, and – most importantly – to solidify our knowledge of the redshift distributions of the sources. Based on a flat ΛCDM model we find S 8 ≡ σ 8 Ω m /0.3 = 0.737 +0.040 −0.036 in a blind analysis from cosmic shear alone. The tension between KiDS cosmic shear and the Planck-Legacy CMB measurements remains in this systematically more robust analysis, with S 8 differing by 2.3 σ . This result is insensitive to changes in the priors on nuisance parameters for intrinsic alignment, baryon feedback, and neutrino mass. KiDS shear measurements are calibrated with a new, more realistic set of image simulations and no significant B-modes are detected in the survey, indicating that systematic errors are under control. When calibrating our redshift distributions by assuming the 30-band COSMOS-2015 photometric redshifts are correct (following the Dark Energy Survey and the Hyper Suprime-Cam Survey), we find the tension with Planck is alleviated. The robust determination of source redshift distributions remains one of the most challenging aspects for future cosmic shear surveys.
Publisher: American Astronomical Society
Date: 31-01-2014
Publisher: American Astronomical Society
Date: 17-02-2017
Publisher: EDP Sciences
Date: 07-2010
Publisher: Oxford University Press (OUP)
Date: 10-2009
Publisher: Oxford University Press (OUP)
Date: 03-12-2015
Publisher: Cambridge University Press (CUP)
Date: 2010
DOI: 10.1071/AS09053
Abstract: A heuristic greedy algorithm is developed for efficiently tiling spatially dense redshift surveys. In its first application to the Galaxy and MassAssembly (GAMA) redshift survey we find it rapidly improves the spatial uniformity of our data, and naturally corrects for any spatial bias introduced by the 2dF multi-object spectrograph. We make conservative predictions for the final state of the GAMA redshift survey after our final allocation of time, and can be confident that even if worse than typical weather affects our observations, all of our main survey requirements will be met.
Publisher: Cambridge University Press (CUP)
Date: 06-2008
DOI: 10.1017/S1743921308027981
Abstract: The GAMA survey aims to deliver 250,000 optical spectra (3–7 Å resolution) over 250 sq. degrees to spectroscopic limits of r AB 19.8 and K AB 17.0 mag. Complementary imaging will be provided by GALEX, VST, UKIRT, VISTA, HERSCHEL and ASKAP to comparable flux levels leading to a definitive multi-wavelength galaxy database. The data will be used to study all aspects of cosmic structures on 1kpc to 1Mpc scales spanning all environments and out to a redshift limit of z ≈ 0.4. Key science drivers include the measurement of: the halo mass function via group velocity dispersions the stellar, HI, and baryonic mass functions galaxy component mass-size relations the recent merger and star-formation rates by mass, types and environment. Detailed modeling of the spectra, broad SEDs, and spatial distributions should provide in idual star formation histories, ages, bulge-disc decompositions and stellar bulge, stellar disc, dust disc, neutral HI gas and total dynamical masses for a significant subset of the s le (~ 100k) spanning both the giant and dwarf galaxy populations. The survey commenced March 2008 with 50k spectra obtained in 21 clear nights using the Anglo Australian Observatory's new multi-fibre-fed bench-mounted dual-beam spectroscopic system (AAΩ).
Publisher: Oxford University Press (OUP)
Date: 12-2010
Publisher: Oxford University Press (OUP)
Date: 22-10-2012
Publisher: Oxford University Press (OUP)
Date: 19-11-2014
Publisher: Oxford University Press (OUP)
Date: 07-02-2013
DOI: 10.1093/MNRAS/STT030
Publisher: Elsevier BV
Date: 09-2008
Publisher: EDP Sciences
Date: 07-2010
Publisher: Oxford University Press (OUP)
Date: 02-11-2016
Publisher: Oxford University Press (OUP)
Date: 02-03-2011
Publisher: Oxford University Press (OUP)
Date: 26-10-2018
Publisher: Oxford University Press (OUP)
Date: 07-05-2012
Publisher: American Physical Society (APS)
Date: 07-2002
Publisher: Oxford University Press (OUP)
Date: 19-11-2014
Publisher: Springer-Verlag
Date: 2001
DOI: 10.1007/10854354_63
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for John Peacock.