Publications (296)1281.03 Total impact
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ABSTRACT: In this work we reformulate the forward modelling of the redshiftspace power spectrum multipole moments for a masked density field, as encountered in galaxy redshift surveys. Exploiting the symmetries of the redshiftspace correlation function, we provide a `maskedfield' generalisation of the Hankel transform relation between the multipole moments in real and Fourier space. Using this result, we detail how a likelihood analysis requiring computation for a broad range of desired $P(k)$ models may be executed $10^310^4$ times faster than with other common approaches, together with significant gains in spectral resolution. We present a concrete application to the complex angular geometry of the VIPERS PDR1 release and discuss the validity of this technique for wideangle surveys.  [Show abstract] [Hide abstract]
ABSTRACT: The Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. Observations will be simultaneous with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of Xray sources. eBOSS will use four different tracers to measure the distanceredshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. Using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z=0.72, we project that eBOSS will yield measurements of $d_A(z)$ to an accuracy of 1.2% and measurements of H(z) to 2.1% when combined with the z>0.6 sample of BOSS galaxies. With ~195,000 new emission line galaxy redshifts, we expect BAO measurements of $d_A(z)$ to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z= 0.87. A sample of more than 500,000 spectroscopicallyconfirmed quasars will provide the first BAO distance measurements over the redshift range 0.9<z<2.2, with expected precision of 2.8% and 4.2% on $d_A(z)$ and H(z), respectively. Finally, with 60,000 new quasars and reobservation of 60,000 quasars known from BOSS, we will obtain new Lymanalpha forest measurements at redshifts z>2.1; these new data will enhance the precision of $d_A(z)$ and H(z) by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide new tests of General Relativity on cosmological scales through redshiftspace distortion measurements, new tests for nonGaussianity in the primordial density field, and new constraints on the summed mass of all neutrino species. Here, we provide an overview of the cosmological goals, spectroscopic target sample, demonstration of spectral quality from early data, and projected cosmological constraints from eBOSS.  [Show abstract] [Hide abstract]
ABSTRACT: We present the Galaxy And Mass Assembly (GAMA) Panchromatic Data Release (PDR) constituting over 230 deg2 of imaging with photometry in 21 bands extending from the farUV to the farIR. These data complement our spectroscopic campaign of over 300k galaxies, and are compiled from observations with a variety of facilities including: GALaxy Evolution eXplorer, Sloan Digital Sky Survey, Visible and Infrared Telescope for Astronomy (VISTA), Widefield Infrared Survey Explorer, and Herschel, with the GAMA regions currently being surveyed by VLT Survey Telescope (VST) and scheduled for observations by Australian Square Kilometer Array Pathfinder (ASKAP). These data are processed to a common astrometric solution, from which photometry is derived for ∼221 373 galaxies with r < 19.8 mag. Online tools are provided to access and download data cutouts, or the full mosaics of the GAMA regions in each band. We focus, in particular, on the reduction and analysis of the VISTA VIsta Kilodegree INfrared Galaxy data, and compare to earlier data sets (i.e. 2MASS and UKIDSS) before combining the data and examining its integrity. Having derived the 21band photometric catalogue, we proceed to fit the data using the energy balance code magphys. These measurements are then used to obtain the first fully empirical measurement of the 0.1–500 μm energy output of the Universe. Exploring the cosmic spectral energy distribution across three timeintervals (0.3–1.1, 1.1–1.8, and 1.8–2.4 Gyr), we find that the Universe is currently generating (1.5 ± 0.3) × 1035 h70 W Mpc−3, down from (2.5 ± 0.2) × 1035 h70 W Mpc−3 2.3 Gyr ago. More importantly, we identify significant and smooth evolution in the integrated photon escape fraction at all wavelengths, with the UV escape fraction increasing from 27(18) per cent at z = 0.18 in NUV(FUV) to 34(23) per cent at z = 0.06. The GAMA PDR can be found at: http://gamapsi.icrar.org/.  [Show abstract] [Hide abstract]
ABSTRACT: The Galaxy And Mass Assembly (GAMA) survey is one of the largest contemporary spectroscopic surveys of low redshift galaxies. Covering an area of ∼286 deg2 (split among five survey regions) down to a limiting magnitude of r < 19.8 mag, we have collected spectra and reliable redshifts for 238 000 objects using the AAOmega spectrograph on the AngloAustralian Telescope. In addition, we have assembled imaging data from a number of independent surveys in order to generate photometry spanning the wavelength range 1 nm–1 m. Here, we report on the recently completed spectroscopic survey and present a series of diagnostics to assess its final state and the quality of the redshift data. We also describe a number of survey aspects and procedures, or updates thereof, including changes to the input catalogue, redshifting and reredshifting, and the derivation of ultraviolet, optical and nearinfrared photometry. Finally, we present the second public release of GAMA data. In this release, we provide input catalogue and targeting information, spectra, redshifts, ultraviolet, optical and nearinfrared photometry, singlecomponent Sérsic fits, stellar masses, Hαderived star formation rates, environment information, and group properties for all galaxies with r < 19.0 mag in two of our survey regions, and for all galaxies with r < 19.4 mag in a third region (72 225 objects in total). The data base serving these data is available at http://www.gamasurvey.org/.  [Show abstract] [Hide abstract]
ABSTRACT: We present an optimized variant of the halo model, designed to produce accurate matter power spectra well into the nonlinear regime for a wide range of cosmological models. To do this, we introduce physically motivated free parameters into the halomodel formalism and fit these to data from highresolution Nbody simulations. For a variety of Λ cold dark matter (ΛCDM) and wCDM models, the halomodel power is accurate to ≃ 5 per cent for k ≤ 10h Mpc−1 and z ≤ 2. An advantage of our new halo model is that it can be adapted to account for the effects of baryonic feedback on the power spectrum. We demonstrate this by fitting the halo model to power spectra from the OWLS (OverWhelmingly Large Simulations) hydrodynamical simulation suite via parameters that govern halo internal structure. We are able to fit all feedback models investigated at the 5 per cent level using only two free parameters, and we place limits on the range of these halo parameters for feedback models investigated by the OWLS simulations. Accurate predictions to high k are vital for weaklensing surveys, and these halo parameters could be considered nuisance parameters to marginalize over in future analyses to mitigate uncertainty regarding the details of feedback. Finally, we investigate how lensing observables predicted by our model compare to those from simulations and from halofit for a range of kcuts and feedback models and quantify the angular scales at which these effects become important. Code to calculate power spectra from the model presented in this paper can be found at https://github.com/alexandermead/hmcode.  [Show abstract] [Hide abstract]
ABSTRACT: Aims. Using the VIMOS Public Extragalactic Redshift Survey (VIPERS) we aim to jointly estimate the key parameters that describe the galaxy density field and its spatial correlations in redshift space. Methods. We use the Bayesian formalism to jointly reconstruct the redshiftspace galaxy density field, power spectrum, galaxy bias and galaxy luminosity function given the observations and survey selection function. The highdimensional posterior distribution is explored using the Wiener filter within a Gibbs sampler. We validate the analysis using simulated catalogues and apply it to VIPERS data taking into consideration the inhomogeneous selection function. Results. We present joint constraints on the anisotropic power spectrum as well as the bias and number density of red and blue galaxy classes in luminosity and redshift bins as well as the measurement covariances of these quantities. We find that the inferred galaxy bias and number density parameters are strongly correlated although these are only weakly correlated with the galaxy power spectrum. The power spectrum and redshiftspace distortion parameters are in agreement with previous VIPERS results with the value of the growth rate $f\sigma_8 = 0.38$ with 18% uncertainty at redshift 0.7.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate how galaxies in VIPERS (the VIMOS Public Extragalactic Redshift Survey) inhabit the cosmological density field by examining the correlations across the observable parameter space of galaxy properties and clustering strength. The highdimensional analysis is made manageable by the use of groupfinding and regression tools. We find that the major trends in galaxy properties can be explained by a single parameter related to stellar mass. After subtracting this trend, residual correlations remain between galaxy properties and the local environment pointing to complex formation dependencies. As a specific application of this work we build subsamples of galaxies with specific clustering properties for use in cosmological tests.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the higherorder correlation properties of the VIMOS Public Extragalactic Redshift Survey (VIPERS) to test the hierarchical scaling hypothesis at z~1 and the dependence on galaxy luminosity, stellar mass, and redshift. We also aim to assess deviations from the linearity of galaxy bias independently from a previously performed analysis of our survey (Di Porto et al. 2014). We have measured the count probability distribution function in cells of radii 3 < R < 10 Mpc/h, deriving $\sigma_{8g}$, the volumeaveraged two,three,and fourpoint correlation functions and the normalized skewness $S_{3g}$ and kurtosis $S_{4g}$ for volumelimited subsamples covering the ranges $19.5 \le M_B(z=1.1)5log(h) \le 21.0$, $9.0 < log(M*/M_{\odot} h^{2}) \le 11.0$, $0.5 \le z < 1.1$. We have thus performed the first measurement of highorder correlations at z~1 in a spectroscopic redshift survey. Our main results are the following. 1) The hierarchical scaling holds throughout the whole range of scale and z. 2) We do not find a significant dependence of $S_{3g}$ on luminosity (below z=0.9 $S_{3g}$ decreases with luminosity but only at 1{\sigma}level). 3) We do not detect a significant dependence of $S_{3g}$ and $S_{4g}$ on scale, except beyond z~0.9, where the dependence can be explained as a consequence of sample variance. 4) We do not detect an evolution of $S_{3g}$ and $S_{4g}$ with z. 5) The linear bias factor $b=\sigma_{8g}/\sigma_{8m}$ increases with z, in agreement with previous results. 6) We quantify deviations from the linear bias by means of the Taylor expansion parameter $b_2$. Our results are compatible with a null nonlinear bias term, but taking into account other available data we argue that there is evidence for a small nonlinear bias term.  [Show abstract] [Hide abstract]
ABSTRACT: We present the first cosmological measurement derived from a galaxy density field subject to a `clipping' transformation. By enforcing an upper bound on the galaxy number density field in the Galaxy and Mass Assembly survey (GAMA), contributions from the nonlinear processes of virialisation and galaxy bias are greatly reduced. This leads to a galaxy power spectrum which is easier to model, without calibration from numerical simulations. We develop a theoretical model for the power spectrum of a clipped field in redshift space, which is exact for the case of anisotropic Gaussian fields. Clipping is found to extend the applicability of the conventional Kaiser prescription by more than a factor of three in wavenumber, or a factor of thirty in terms of the number of Fourier modes. By modelling the galaxy power spectrum on scales k < 0.3 h/Mpc and density fluctuations $\delta_g < 4$ we measure the normalised growth rate $f\sigma_8(z = 0.18) = 0.29 \pm 0.10$.  [Show abstract] [Hide abstract]
ABSTRACT: We compare three methods to measure the countincell probability density function of galaxies in a spectroscopic redshift survey. From this comparison we found that when the sampling is low (the average number of object per cell is around unity) it is necessary to use a parametric method to model the galaxy distribution. We used a set of mock catalogues of VIPERS, in order to verify if we were able to reconstruct the cellcount probability distribution once the observational strategy is applied. We find that in the simulated catalogues, the probability distribution of galaxies is better represented by a Gamma expansion than a Skewed LogNormal. Finally, we correct the cellcount probability distribution function from the angular selection effect of the VIMOS instrument and study the redshift and absolute magnitude dependency of the underlying galaxy density function in VIPERS from redshift $0.5$ to $1.1$. We found very weak evolution of the probability density distribution function and that it is well approximated, independently from the chosen tracers, by a Gamma distribution. 
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ABSTRACT: Ongoing and nearfuture imagingbased dark energy experiments are critically dependent upon photometric redshifts (a.k.a. photoz’s): i.e., estimates of the redshifts of objects based only on flux information obtained through broad filters. Higherquality, lowerscatter photoz’s will result in smaller random errors on cosmological parameters; while systematic errors in photometric redshift estimates, if not constrained, may dominate all other uncertainties from these experiments. The desired optimization and calibration is dependent upon spectroscopic measurements for secure redshift information; this is the key application of galaxy spectroscopy for imagingbased dark energy experiments.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the use of the crosscorrelation between galaxies and galaxy groups to measure redshiftspace distortions (RSD) and thus probe the growth rate of cosmological structure. This is compared to the classical approach based on using galaxy autocorrelation. We make use of realistic simulated galaxy catalogues that have been constructed by populating simulated dark matter haloes with galaxies through halo occupation prescriptions. We adapt the classical RSD dispersion model to the case of the groupgalaxy crosscorrelation function and estimate the RSD parameter {\beta} by fitting both the full anisotropic correlation function {\xi}(rp, {\pi}) and its multipole moments. In addition, we define a modified version of the latter statistics by truncating the multipole moments to exclude strongly nonlinear distortions at small transverse scales. We fit these three observable quantities in our set of simulated galaxy catalogues and estimate statistical and systematic errors on {\beta} for the case of galaxygalaxy, group group, and groupgalaxy correlation functions. When ignoring offdiagonal elements of the covariance matrix in the fitting, the truncated multipole moments of the groupgalaxy crosscorrelation function provide the most accurate estimate, with systematic errors below 3% when fitting transverse scales larger than 10 Mpc/h. When including the full covariance matrix, however, the three observables perform more similarly and are more stable with respect to the included scales. Group autocorrelation provides marginally smaller systematic errors, followed by groupgalaxy crosscorrelation and galaxy autocorrelation. Although statistical errors are generally larger for groups, the use of groupgalaxy crosscorrelation can potentially allow the reduction of systematics while using simple linear or dispersion models.  [Show abstract] [Hide abstract]
ABSTRACT: We develop and test an algorithm to rescale a simulated darkmatter particle distribution or halo catalogue from a standard gravity model to that of a modified gravity model. This method is based on that of Angulo & White but with some additional ingredients to account for (i) scaledependent growth of linear density perturbations and (ii) screening mechanisms that are generic features of viable modified gravity models. We attempt to keep the method as general as possible, so that it may plausibly be applied to a wide range of modified theories, although tests against simulations are restricted to a subclass of f (R) models at this stage. We show that rescaling allows the power spectrum of matter to be reproduced at the ∼3 per cent level in both real and redshift space up to k = 0.1h Mpc−1 if we change the box size and alter the particle displacement field; this limit can be extended to k = 1h Mpc−1 if we additionally alter halo internal structure. We simultaneously develop an algorithm that can be applied directly to a halo catalogue, in which case the halo mass function and clustering can be reproduced at the ∼5 per cent level. Finally, we investigate the clustering of halo particle distributions, generated from rescaled halo catalogues, and find that a similar accuracy can be reached.  [Show abstract] [Hide abstract]
ABSTRACT: We investigate the dependence of the galaxy luminosity function on geometric environment within the Galaxy And Mass Assembly (GAMA) survey. The tidal tensor prescription, based on the Hessian of the pseudogravitational potential, is used to classify the cosmic web and define the geometric environments: for a given smoothing scale, we classify every position of the surveyed region, 0.04 < z < 0.26, as either a void, a sheet, a filament or a knot. We consider how to choose appropriate thresholds in the eigenvalues of the Hessian in order to partition the galaxies approximately evenly between environments. We find a significant variation in the luminosity function of galaxies between different geometric environments; the normalization, characterized by ϕ* in a Schechter function fit, increases by an order of magnitude from voids to knots. The turnover magnitude, characterized by M*, brightens by approximately 0.5 mag from voids to knots. However, we show that the observed modulation can be entirely attributed to the indirect localdensity dependence. We therefore find no evidence of a direct influence of the cosmic web on the galaxy luminosity function.  [Show abstract] [Hide abstract]
ABSTRACT: We use 80 922 galaxies in the Galaxy And Mass Assembly (GAMA) survey to measure the galaxy luminosity function (LF) in different environments over the redshift range 0.04 < z < 0.26. The depth and size of GAMA allows us to define samples split by colour and redshift to measure the dependence of the LF on environment, redshift and colour. We find that the LF varies smoothly with overdensity, consistent with previous results, with little environmental dependent evolution over the last 3 Gyr. The modified GALFORM model predictions agree remarkably well with our LFs split by environment, particularly in the most overdense environments. The LFs predicted by the model for both blue and red galaxies are consistent with GAMA for the environments and luminosities at which such galaxies dominate. Discrepancies between the model and the data seen in the faint end of the LF suggest too many faint red galaxies are predicted, which is likely to be due to the overquenching of satellite galaxies. The excess of bright blue galaxies predicted in underdense regions could be due to the implementation of AGN feedback not being sufficiently effective in the lower mass haloes. 
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ABSTRACT: We report results obtained during the characterization of a commercial frontilluminated progressive scan interline transfer CCD camera. We demonstrate that the unmodified camera operates successfully in temperature and pressure conditions (40C, 4mBar) representative of a high altitude balloon mission. We further demonstrate that the centroid of a wellsampled star can be determined to better than 2% of a pixel, even though the CCD is equipped with a microlens array. This device has been selected for use in a closedloop starguiding and tiptilt correction system in the BITSTABLE balloon mission.  [Show abstract] [Hide abstract]
ABSTRACT: We discuss the extension to redshift space of a rescaling algorithm, designed to alter the effective cosmology of a preexisting simulated particle distribution or catalogue of dark matter haloes. The rescaling approach was initially developed by Angulo & White and was adapted and applied to halo catalogues in real space in our previous work. This algorithm requires no information other than the initial and target cosmological parameters, and it contains no tuned parameters. It is shown here that the rescaling method also works well in redshift space, and that the rescaled simulations can reproduce the growth rate of cosmological density fluctuations appropriate for the target cosmology. Even when rescaling a grossly nonstandard model with Λ = 0 and zero baryons, the redshiftspace power spectrum of standard Λ cold dark matter can be reproduced to about 5 per cent error for k < 0.2 h Mpc−1. The ratio of quadrupoletomonopole power spectra remains correct to the same tolerance up to k = 1 h Mpc−1, provided that the input halo catalogue contains measured internal velocity dispersions.  [Show abstract] [Hide abstract]
ABSTRACT: Our view of the lowredshift Cosmic Web has been revolutionized by galaxy redshift surveys such as 6dFGS, SDSS and 2MRS. However, the tradeoff between depth and angular coverage limits a systematic threedimensional 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 stateoftheart photometric redshift techniques. We have undertaken a dedicated program of crossmatching the largest photometric allsky 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 midinfrared sample together with SuperCOSMOS optical data allows us to push to redshift shells of z~0.20.3 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 crosscorrelations with the cosmic microwave background such as the integrated SachsWolfe effect or lensing studies.
Publication Stats
30k  Citations  
1,281.03  Total Impact Points  
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Institutions

19852015

The University of Edinburgh
 Institute for Astronomy (IfA)
Edinburgh, Scotland, United Kingdom


19862014

The Royal Observatory, Edinburgh
Edinburgh, Scotland, United Kingdom


19912012

Durham University
 Department of Physics
Durham, England, United Kingdom


2011

University of California, Berkeley
Berkeley, California, United States


2010

Universität Siegen
Siegen, North RhineWestphalia, Germany


20092010

University of St Andrews
 School of Physics and Astronomy
Saint Andrews, Scotland, United Kingdom


2007

Space Telescope Science Institute
Baltimore, Maryland, United States


2002

Massachusetts Institute of Technology
 Laboratory for Nuclear Science
Cambridge, Massachusetts, United States


1997

The University of Western Ontario
 Department of Physics and Astronomy
London, Ontario, Canada
