Publications (125)508.82 Total impact

Article: The masses of satellites in GAMA galaxy groups from 100 square degrees of KiDS weak lensing data
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ABSTRACT: We use the first 100 sq. deg. of overlap between the KiloDegree Survey (KiDS) and the Galaxy And Mass Assembly (GAMA) survey to determine the galaxy halo mass of ~10,000 spectroscopicallyconfirmed satellite galaxies in massive ($M > 10^{13}h^{1}{\rm M}_\odot$) galaxy groups. Separating the sample as a function of projected distance to the group centre, we jointly model the satellites and their host groups with NavarroFrenkWhite (NFW) density profiles, fully accounting for the data covariance. The probed satellite galaxies in these groups have total masses $\log M_{\rm sub} /(h^{1}{\rm M}_\odot) \approx 11.7  12.2$ consistent across groupcentric distance within the errorbars. Given their typical stellar masses, $\log M_{\rm \star,sat}/(h^{2}{\rm M}_\odot) \sim 10.5$, such total masses imply stellar mass fractions of $M_{\rm \star,sat} /M_{\rm sub} \approx 0.04 h^{1}$ . The average subhalo hosting these satellite galaxies has a mass $M_{\rm sub} \sim 0.015M_{\rm host}$ independent of host halo mass, in broad agreement with the expectations of structure formation in a $\Lambda$CDM universe. 
Article: Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data
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ABSTRACT: The KiloDegree Survey (KiDS) is an optical widefield survey designed to map the matter distribution in the Universe using weak gravitational lensing. In this paper, we use these data to measure the density profiles and masses of a sample of $\sim \mathrm{1400}$ spectroscopically identified galaxy groups and clusters from the Galaxy And Mass Assembly (GAMA) survey. We detect a highly significant signal (signaltonoiseratio $\sim$ 120), allowing us to study the properties of dark matter haloes over one and a half order of magnitude in mass, from $M \sim 10^{13}10^{14.5} h^{1}\mathrm{M_{\odot}}$. We interpret the results for various subsamples of groups using a halo model framework which accounts for the miscentring of the Brightest Cluster Galaxy (used as the tracer of the group centre) with respect to the centre of the group's dark matter halo. We find that the density profiles of the haloes are well described by an NFW profile with concentrations that agree with predictions from numerical simulations. In addition, we constrain scaling relations between the mass and a number of observable group properties. We find that the mass scales with the total rband luminosity as a powerlaw with slope $1.16 \pm 0.13$ (1sigma) and with the group velocity dispersion as a powerlaw with slope $1.89 \pm 0.27$ (1sigma). Finally, we demonstrate the potential of weak lensing studies of groups to discriminate between models of baryonic feedback at group scales by comparing our results with the predictions from the CosmoOverWhelmingly Large Simulations (CosmoOWLS) project, ruling out models without AGN feedback.  [Show abstract] [Hide abstract]
ABSTRACT: The KiloDegree Survey (KiDS) is a multiband imaging survey designed for cosmological studies from weak lensing and photometric redshifts. It uses the ESO VLT Survey Telescope with its widefield camera OmegaCAM. KiDS images are taken in four filters similar to the SDSS ugri bands. The bestseeing time is reserved for deep rband observations that reach a median 5sigma limiting AB magnitude of 24.9 with a median seeing that is better than 0.7arcsec. Initial KiDS observations have concentrated on the GAMA regions near the celestial equator, where extensive, highly complete redshift catalogues are available. A total of 101 survey tiles, one square degree each, form the basis of the first set of lensing analyses, which focus on measurements of halo properties of GAMA galaxies. 9 galaxies per square arcminute enter the lensing analysis, for an effective inverse shear variance of 69 per square arcminute. Accounting for the shape measurement weight, the median redshift of the sources is 0.53. KiDS data processing follows two parallel tracks, one optimized for galaxy shape measurement (for weak lensing), and one for accurate matchedaperture photometry in four bands (for photometric redshifts). This technical paper describes how the lensing and photometric redshift catalogues have been produced (including an extensive description of the Gaussian Aperture and Photometry pipeline), summarizes the data quality, and presents extensive tests for systematic errors that might affect the lensing analyses. We also provide first demonstrations of the suitability of the data for cosmological measurements, and explain how the shear catalogues were blinded to prevent confirmation bias in the scientific analyses. The KiDS shear and photometric redshift catalogues, presented in this paper, are released to the community through http://kids.strw.leidenuniv.nl .  [Show abstract] [Hide abstract]
ABSTRACT: The KiloDegree Survey (KiDS) is an optical widefield imaging survey carried out with the VLT Survey Telescope and the OmegaCAM camera. KiDS will image 1500 square degrees in four filters (ugri), and together with its nearinfrared counterpart VIKING will produce deep photometry in nine bands. Designed for weak lensing shape and photometric redshift measurements, the core science driver of the survey is mapping the largescale matter distribution in the Universe back to a redshift of ~0.5. Secondary science cases are manifold, covering topics such as galaxy evolution, Milky Way structure, and the detection of highredshift clusters and quasars. KiDS is an ESO Public Survey and dedicated to serving the astronomical community with highquality data products derived from the survey data, as well as with calibration data. Public data releases will be made on a yearly basis, the first two of which are presented here. For a total of 148 survey tiles (~160 sq.deg.) astrometrically and photometrically calibrated, coadded ugri images have been released, accompanied by weight maps, masks, source lists, and a multiband source catalog. A dedicated pipeline and data management system based on the AstroWISE software system, combined with newly developed masking and source classification software, is used for the data production of the data products described here. The achieved data quality and early science projects based on the data products in the first two data releases are reviewed in order to validate the survey data. Early scientific results include the detection of nine highz QSOs, fifteen candidate strong gravitational lenses, highquality photometric redshifts and galaxy structural parameters for hundreds of thousands of galaxies. (Abridged)Astronomy and Astrophysics 07/2015; · 4.48 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present an optimised 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 physicallymotivated free parameters into the halomodel formalism and fit these to data from highresolution Nbody simulations. For a variety of $\Lambda$CDM and $w$CDM models the halomodel power is accurate to $\simeq 5$ per cent for $k\leq 10h\,\mathrm{Mpc}^{1}$ and $z\leq 2$. We compare our results with recent revisions of the popular HALOFIT model and show that our predictions are more accurate. 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 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 weak lensing surveys, and these halo parameters could be considered nuisance parameters to marginalise over in future analyses to mitigate uncertainty regarding the details of feedback, the limits we find on these parameters provide a prior. Finally we investigate how lensing observables predicted by our model compare to those from simulations and from HALOFIT for a range of $k$cuts 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: 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 $f\sigma_8(z = 0.18) = 0.29 \pm 0.10$.  Astronomy and Astrophysics 04/2015; 576:A130. DOI:10.1051/00046361/201323053 · 4.48 Impact Factor
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ABSTRACT: We measure the crosscorrelation of cosmic microwave background lensing convergence maps derived from Atacama Cosmology Telescope data with galaxy lensing convergence maps as measured by the CanadaFranceHawaii Telescope Stripe 82 Survey. The CMBgalaxy lensing cross power spectrum is measured for the first time with a significance of 3.2{\sigma}, which corresponds to a 16% constraint on the amplitude of density fluctuations at redshifts ~ 0.9. With upcoming improved lensing data, this novel type of measurement will become a powerful cosmological probe, providing a precise measurement of the mass distribution at intermediate redshifts and serving as a calibrator for systematic biases in weak lensing measurements.Physical Review D 03/2015; 91:062001. DOI:10.1103/PhysRevD.91.062001 · 4.86 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We study the correlations of the shear signal between triplets of sources in the CanadaFranceHawaii Lensing Survey (CFHTLenS) to probe cosmological parameters via the matter bispectrum. In contrast to previous studies, we adopted a nonGaussian model of the data likelihood which is supported by our simulations of the survey. We find that for stateoftheart surveys, similar to CFHTLenS, a Gaussian likelihood analysis is a reasonable approximation, albeit small differences in the parameter constraints are already visible. For future surveys we expect that a Gaussian model becomes inaccurate. Our algorithm for a refined nonGaussian analysis and data compression is then of great utility especially because it is not much more elaborate if simulated data are available. Applying this algorithm to the thirdorder correlations of shear alone in a blind analysis, we find a good agreement with the standard cosmological model: $\Sigma_8$=$\sigma_8$ $(\Omega_{\rm m}/0.27)^{0.64}$=$0.79^{+0.08}_{0.11}$ for a flat $\Lambda\rm CDM$ cosmology with $h=0.7\pm0.04$ ($68\%$ credible interval). Nevertheless our models provide only moderately good fits as indicated by $\chi^2/{\rm dof}=2.9$, including a $20\%$ r.m.s. uncertainty in the predicted signal amplitude. The models cannot explain a signal drop on scales around 15 arcmin, which may be caused by systematics. It is unclear whether the discrepancy can be fully explained by residual PSF systematics of which we find evidence at least on scales of a few arcmin. Therefore we need a better understanding of higherorder correlations of cosmic shear and their systematics to confidently apply them as cosmological probes.Monthly Notices of the Royal Astronomical Society 02/2015; 449(2). DOI:10.1093/mnras/stv339 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present new constraints on the relationship between galaxies and their host dark matter halos, measured from the location of the peak of the stellartohalo mass ratio (SHMR), up to the most massive galaxy clusters at redshift $z\sim0.8$ and over a volume of nearly 0.1~Gpc$^3$. We use a unique combination of deep observations in the CFHTLenS/VIPERS field from the nearUV to the nearIR, supplemented by $\sim60\,000$ secure spectroscopic redshifts, analysing galaxy clustering, galaxygalaxy lensing and the stellar mass function. We interpret our measurements within the halo occupation distribution (HOD) framework, separating the contributions from central and satellite galaxies. We find that the SHMR for the central galaxies peaks at $M_{\rm h, peak} = 1.9^{+0.2}_{0.1}\times10^{12} M_{\odot}$ with an amplitude of $0.025$, which decreases to $\sim0.001$ for massive halos ($M_{\rm h} > 10^{14} M_{\odot}$). Compared to central galaxies only, the total SHMR (including satellites) is boosted by a factor 10 in the highmass regime (clustersize halos), a result consistent with cluster analyses from the literature based on fully independent methods. After properly accounting for differences in modelling, we have compared our results with a large number of results from the literature up to $z=1$: we find good general agreement, independently of the method used, within the typical stellarmass systematic errors at low to intermediate mass (${M}_{\star} < 10^{11} M_{\odot}$) and the statistical errors above. We have also compared our SHMR results to semianalytic simulations and found that the SHMR is tilted compared to our measurements in such a way that they over (under) predict star formation efficiency in central (satellite) galaxies.  [Show abstract] [Hide abstract]
ABSTRACT: Ultradeep observations of ECDFS with Chandra and XMMNewton enable a search for extended Xray emission down to an unprecedented flux of $2\times10^{16}$ ergs s$^{1}$ cm$^{2}$. We present the search for the extended emission on spatial scales of 32$^{\prime\prime}$ in both Chandra and XMM data, covering 0.3 square degrees and model the extended emission on scales of arcminutes. We present a catalog of 46 spectroscopically identified groups, reaching a redshift of 1.6. We show that the statistical properties of ECDFS, such as logNlogS and Xray luminosity function are broadly consistent with LCDM, with the exception that dn/dz/d$\Omega$ test reveals that a redshift range of $0.2<z<0.5$ in ECDFS is sparsely populated. The lack of nearby structure, however, makes studies of highredshift groups particularly easier both in Xrays and lensing, due to a lower level of clustered foreground. We present one and two point statistics of the galaxy groups as well as weaklensing analysis to show that the detected lowluminosity systems are indeed lowmass systems. We verify the applicability of the scaling relations between the Xray luminosity and the total mass of the group, derived for the COSMOS survey to lower masses and higher redshifts probed by ECDFS by means of stacked weak lensing and clustering analysis, constraining any possible departures to be within 30\% in mass. Abridged.  [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 normalisation, characterised by $\phi^{*}$ in a Schechter function fit, increases by an order of magnitude from voids to knots. The turnover magnitude, characterised 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.Monthly Notices of the Royal Astronomical Society 12/2014; 448(4). DOI:10.1093/mnras/stv237 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present weak lensing and Xray analysis of 12 low mass clusters from the CFHTLenS and XMMCFHTLS surveys. We combine these systems with highmass systems from CCCP and lowmass systems from COSMOS to obtain a sample of 70 systems, which we divide into subsamples of 15 merging and 55 relaxed systems. We measure LT, ML and MT scaling relations and find in all cases that the powerlaw slopes of the full, merging and relaxed subsamples are consistent. For the MT we find slopes consistent with the selfsimilar model, whereas LT results in steeper and ML in flatter relations. We find a marginal trend for larger scatter and lower normalisation in the ML and MT relations for the merging subsample, which we attribute to triaxiality and substructure. We explore the effects of Xray crosscalibration and find that Chandra calibration leads to flatter LT and MT relations. We also utilise the three surveys making up the sample as overlapping mass bins. For COSMOS and CFHTLS we find slopes consistent with the relation fitted to the full sample, whereas the high mass CCCP sample favours flatter slopes. We also find that intermediate mass systems have a higher mass for their luminosity. Unfortunately our sample does not enable direct measurement of a break at low masses, but we find a trend for enhanced intrinsic scatter in mass at low masses.Monthly Notices of the Royal Astronomical Society 10/2014; 451(2). DOI:10.1093/mnras/stv923 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present the cluster massrichness scaling relation calibrated by a weak lensing analysis of >18,000 galaxy cluster candidates in the CanadaFranceHawaii Telescope Lensing Survey (CFHTLenS). Detected using the 3DMatchedFilter clusterfinder of Milkeraitis et al., these cluster candidates span a wide range of masses, from the small group scale up to $\sim10^{15} M_{\odot}$, and redshifts 0.2 $\lesssim z\lesssim$ 0.9. The total significance of the shear measurement amounts to 54$\sigma$. We compare cluster masses determined using weak lensing shear and magnification, finding the measurements in individual richness bins to yield 1$\sigma$ compatibility, but with magnification estimates biased low. This first direct mass comparison yields important insights for improving the systematics handling of future lensing magnification work. In addition, we confirm analyses that suggest cluster miscentring has an important effect on the observed 3DMatchedFilter halo profiles, and we quantify this by fitting for projected cluster centroid offsets, which are typically $\sim$ 0.4 arcmin. We bin the cluster candidates as a function of redshift, finding similar cluster masses and richness across the full range up to $z \sim$ 0.9. We measure the 3DMF massrichness scaling relation $M_{200 } = M_0 (N_{200} / 20)^\beta$. We find a normalization $M_0 \sim (2.7^{+0.5}_{0.4}) \times 10^{13} M_{\odot}$, and a logarithmic slope of $\beta \sim 1.4 \pm 0.1$, both of which are in 1$\sigma$ agreement with results from the magnification analysis. We find no evidence for a redshiftdependence of the normalization. The CFHTLenS 3DMatchedFilter cluster catalogue is now available at cfhtlens.org.Monthly Notices of the Royal Astronomical Society 09/2014; 447(2). DOI:10.1093/mnras/stu2545 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: (Abridged) The effect of baryonic feedback on the dark matter mass distribution is generally considered to be a nuisance to weak gravitational lensing. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arcminutes. Recent progress on the numerical modelling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current weak lensing surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform our analysis, we construct an analytic fitting formula that describes the effect of the baryons on the mass power spectrum. This fitting formula is based on three scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for $z<1.5$, where it models the simulations to an accuracy that is better than $2\%$ for scales $k<10 h\mbox{Mpc}^{1}$ and better than $5\%$ for $10 < k < 100 h\mbox{Mpc}^{1}$. Equipped with this precise tool, this paper presents the first constraint on baryonic feedback models using gravitational lensing data, from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). In this analysis, we show that the effect of neutrino mass on the mass power spectrum is degenerate with the baryonic feedback at small angular scales and cannot be ignored. Assuming a cosmology precision fixed by WMAP9, we find that a universe with no baryon feedback and massless neutrinos is rejected by the CFHTLenS lensing data with 96\% confidence. Our study shows that ongoing weak gravitational lensing surveys (KiDS, HSC and DES) will offer a unique opportunity to probe the physics of baryons at galactic scales, in addition to the expected constraints on the total neutrino mass.Monthly Notices of the Royal Astronomical Society 07/2014; 450(2). DOI:10.1093/mnras/stv646 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Higherorder, nonGaussian aspects of the largescale structure carry valuable information on structure formation and cosmology, which is complementary to secondorder statistics. In this work we measure second and thirdorder weaklensing aperturemass moments from CFHTLenS and combine those with CMB anisotropy probes. The third moment is measured with a significance of $2\sigma$. The combined constraint on $\Sigma_8 = \sigma_8 (\Omega_{\rm m}/0.27)^\alpha$ is improved by 10%, in comparison to the secondorder only, and the allowed ranges for $\Omega_{\rm m}$ and $\sigma_8$ are substantially reduced. Including general triangles of the lensing bispectrum yields tighter constraints compared to probing mainly equilateral triangles. Second and thirdorder CFHTLenS lensing measurements improve Planck CMB constraints on $\Omega_{\rm m}$ and $\sigma_8$ by 26% for flat $\Lambda$CDM. For a model with free curvature, the joint CFHTLenSPlanck result is $\Omega_{\rm m} = 0.28 \pm 0.02$ (68% confidence), which is an improvement of 43% compared to Planck alone. We test how our results are potentially subject to three astrophysical sources of contamination: sourcelens clustering, the intrinsic alignment of galaxy shapes, and baryonic effects. We explore future limitations of the cosmological use of thirdorder weak lensing, such as the nonlinear model and the Gaussianity of the likelihood function.Monthly Notices of the Royal Astronomical Society 04/2014; 441(3). DOI:10.1093/mnras/stu754 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: This paper presents the first application of 3D cosmic shear to a widefield weak lensing survey. 3D cosmic shear is a technique that analyses weak lensing in three dimensions using a spherical harmonic approach, and does not bin data in the redshift direction. This is applied to CFHTLenS, a 154 square degree imaging survey with a median redshift of 0.7 and an effective number density of 11 galaxies per square arcminute usable for weak lensing. To account for survey masks we apply a 3D pseudoCl approach on weak lensing data, and to avoid uncertainties in the highly nonlinear regime, we separately analyse radial wavenumbers k<=1.5h/Mpc and k<=5.0h/Mpc, and angular wavenumbers l~4005000. We show how one can recover 2D and tomographic power spectra from the full 3D cosmic shear power spectra and present a measurement of the 2D cosmic shear power spectrum, and measurements of a set of 2bin and 6bin cosmic shear tomographic power spectra; in doing so we find that using the 3D power in the calculation of such 2D and tomographic power spectra from data naturally accounts for a minimum scale in the matter power spectrum. We use 3D cosmic shear to constrain cosmologies with parameters OmegaM, OmegaB, sigma8, h, ns, w0, wa. For a nonevolving dark energy equation of state, and assuming a flat cosmology, lensing combined with WMAP7 results in h=0.78+/0.12, OmegaM=0.252+/0.079, sigma8=0.88+/0.23 and w=1.16+/0.38 using only scales k<=1.5h/Mpc. We also present results of lensing combined with first year Planck results, where we find no tension with the results from this analysis, but we also find no significant improvement over the Planck results alone. We find evidence of a suppression of power compared to LCDM on small scales 1.5<k<=5.0h/Mpc in the lensing data, which is consistent with predictions of the effect of baryonic feedback on the matter power spectrum. [abridged]Monthly Notices of the Royal Astronomical Society 01/2014; 442(2). DOI:10.1093/mnras/stu934 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We outline the prospects for performing pioneering radio weak gravitational lensing analyses using observations from a potential forthcoming JVLA Sky Survey program. A largescale survey with the JVLA can offer interesting and unique opportunities for performing weak lensing studies in the radio band, a field which has until now been the preserve of optical telescopes. In particular, the JVLA has the capacity for large, deep radio surveys with relatively high angular resolution, which are the key characteristics required for a successful weak lensing study. We highlight the potential advantages and unique aspects of performing weak lensing in the radio band. In particular, the inclusion of continuum polarisation information can greatly reduce noise in weak lensing reconstructions and can also remove the effects of intrinsic galaxy alignments, the key astrophysical systematic effect that limits weak lensing at all wavelengths. We identify a VLASS "deep fields" program (total area ~1020 square degs), to be conducted at Lband and with highresolution (Aarray configuration), as the optimal survey strategy from the point of view of weak lensing science. Such a survey will build on the unique strengths of the JVLA and will remain unsurpassed in terms of its combination of resolution and sensitivity until the advent of the Square Kilometre Array. We identify the best fields on the JVLAaccessible sky from the point of view of overlapping with existing deep optical and near infrared data which will provide crucial redshift information and facilitate a host of additional compelling multiwavelength science.  [Show abstract] [Hide abstract]
ABSTRACT: Galaxygalaxy weak lensing is a direct probe of the mean matter distribution around galaxies. The depth and sky coverage of the CFHT Legacy Survey yield statistically significant galaxy halo mass measurements over a much wider range of stellar masses ($10^{8.75}$ to $10^{11.3} M_{\odot}$) and redshifts ($0.2 < z < 0.8$) than previous weak lensing studies. The stellartohalo mass ratio (SHMR) reaches a maximum of $3.4\pm0.2$ percent as a function of halo mass at $\sim 10^{12.25} M_{\odot}$ (at redshift $z =0.5$). We find, for the first time from weak lensing alone, evidence for significant evolution in the SHMR: the peak ratio falls as a function of cosmic time from $3.8 \pm 0.3$ percent at $z \sim 0.7$ to $3.0 \pm 0.2$ percent at $z \sim 0.3$, and shifts to lower stellar mass haloes. These evolutionary trends are dominated by red galaxies, and are consistent with a model in which the stellar mass above which star formation is quenched "downsizes" with cosmic time. In contrast, the SHMR of blue, starforming galaxies is well fit by a power law that does not evolve with time. This suggests that blue galaxies form stars at a rate that is balanced with their dark matter accretion in such a way that they evolve along the SHMR. This can be used to constrain the mean star formation rate of the galaxy population over cosmic time.Monthly Notices of the Royal Astronomical Society 10/2013; 447(1). DOI:10.1093/mnras/stu2367 · 5.23 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third in a series of image analysis challenges, with a goal of testing and facilitating the development of methods for analyzing astronomical images that will be used to measure weak gravitational lensing. This measurement requires extremely precise estimation of very small galaxy shape distortions, in the presence of far larger intrinsic galaxy shapes and distortions due to the blurring kernel caused by the atmosphere, telescope optics, and instrumental effects. The GREAT3 challenge is posed to the astronomy, machine learning, and statistics communities, and includes tests of three specific effects that are of immediate relevance to upcoming weak lensing surveys, two of which have never been tested in a community challenge before. These effects include realistically complex galaxy models based on highresolution imaging from space; spatially varying blurring kernel; and combination of multiple different exposures. To facilitate entry by people new to the field, and for use as a diagnostic tool, the simulation software for the challenge is publicly available, though the exact parameters used for the challenge are blinded. Sample scripts to analyze the challenge data using existing methods will also be provided. See http://great3challenge.info and http://great3.projects.phys.ucl.ac.uk/leaderboard/ for more information.The Astrophysical Journal Supplement Series 08/2013; 212(1). DOI:10.1088/00670049/212/1/5 · 14.14 Impact Factor
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4k  Citations  
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Institutions

2000–2015

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


2014

Scottish Universities Physics Alliance
Glasgow, Scotland, United Kingdom


2012

The Ohio State University
 Department of Physics
Columbus, Ohio, United States


2009

University of Nottingham
 School of Physics and Astronomy
Nottigham, England, United Kingdom


2006–2009

University of British Columbia  Vancouver
 Department of Physics and Astronomy
Vancouver, British Columbia, Canada


2008

Pierre and Marie Curie University  Paris 6
 Institut d'astrophysique de Paris
Paris, IledeFrance, France


2007–2008

Institut d'astrophysique de Paris
Lutetia Parisorum, ÎledeFrance, France


2004–2008

Max Planck Institute for Astronomy
Heidelburg, BadenWürttemberg, Germany


2002–2005

University of Oxford
 Department of Physics
Oxford, England, United Kingdom
