Publications (131)549.36 Total impact
 [Show abstract] [Hide abstract]
ABSTRACT: Mass calibration uncertainty is the largest systematic effect for using clusters of galaxies to constrain cosmological parameters. We present weak lensing mass measurements from the CanadaFranceHawaii Telescope Stripe 82 Survey for galaxy clusters selected through their high signaltonoise thermal SunyaevZeldovich (tSZ) signal measured with the Atacama Cosmology Telescope (ACT). The average weak lensing mass is $\left(4.8\pm0.8\right)\,\times10^{14}\,\mathrm{M}_\odot$, consistent with the tSZ mass estimate of $\left(4.70\pm1.0\right)\,\times10^{14}\,\mathrm{M}_\odot$ which assumes a universal pressure profile for the cluster gas. Our results are consistent with previous weaklensing measurements of tSZdetected clusters from the Planck satellite. When comparing our results, we estimate the Eddington bias correction for the sample intersection of Planck and weaklensing clusters which was previously neglected.  [Show abstract] [Hide abstract]
ABSTRACT: Future cosmological measurements should enable the sum of neutrino masses to be determined indirectly through their effects on the expansion rate of the Universe and the clustering of matter. We consider prospects for the gravitationally lensed Cosmic Microwave Background anisotropies and Baryon Acoustic Oscillations in the galaxy distribution, examining how the projected uncertainty of $\approx15$ meV on the neutrino mass sum (a 4$\sigma$ detection of the minimal mass) might be reached over the next decade. The current 1$\sigma$ uncertainty of $\approx 103$ meV (Planck2015+BAO15) will be improved by upcoming 'Stage3' CMB experiments (S3+BAO15: 44 meV), then upcoming BAO measurements (S3+DESI: 22 meV), and planned nextgeneration 'Stage 4' CMB experiments (S4+DESI: 1519 meV, depending on angular range). An improved optical depth measurement is important: the projected neutrino mass uncertainty increases to $26$ meV if S4 is limited to $\ell>20$ and combined with current largescale polarization data. Looking beyond $\Lambda$CDM, including curvature uncertainty increases the forecast mass error by $\approx$ 50% for S4+DESI, and more than doubles the error with a twoparameter dark energy equation of state. Complementary lowredshift probes including galaxy lensing will play a role in distinguishing between massive neutrinos and a departure from a $w=1$, flat geometry.  [Show abstract] [Hide abstract]
ABSTRACT: The Bmode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the suborbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement groundbased cosmic microwave background (CMB) programs. BFORE will survey ~1/4 of the sky with 1.7  3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB Bmode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact offaxis telescope coupled to >10,000 superconducting detectors. 
Article: Contamination of earlytype galaxy alignments to galaxy lensingCMB lensing crosscorrelation
[Show abstract] [Hide abstract]
ABSTRACT: Galaxy shapes are subject to distortions due to the tidal field of the Universe. The crosscorrelation of galaxy lensing with the lensing of the Cosmic Microwave Background (CMB) cannot easily be separated from the crosscorrelation of galaxy intrinsic shapes with CMB lensing. Previous work suggested that the intrinsic alignment contamination can be $15\%$ of this crossspectrum for the CFHT Stripe 82 (CS82) and Atacama Cosmology Telescope surveys. Here we reexamine these estimates using uptodate observational constraints of intrinsic alignments at a redshift more similar to that of CS82 galaxies. We find a $\approx$ $10\%$ contamination of the crossspectrum from red galaxies, with $\approx$ $3\%$ uncertainty due to uncertainties in the redshift distribution of source galaxies and the modelling of the spectral energy distribution. Blue galaxies are consistent with being unaligned, but could contaminate the crossspectrum by an additional $9.5\%$ within current $95\%$ confidence levels. While our fiducial estimate of alignment contamination is similar to previous work, our work suggests that the relevance of alignments for CMB lensinggalaxy lensing crosscorrelation remains largely unconstrained. Little information is currently available about alignments at $z>1.2$. We consider the upper limiting case where all $z>1.2$ galaxies are aligned with the same strength as low redshift luminous red galaxies, finding as much as $\approx$ $60\%$ contamination.Monthly Notices of the Royal Astronomical Society 07/2015; 453(1). DOI:10.1093/mnras/stv1655 · 5.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the gravitational lensing of the Cosmic Microwave Background (CMB) temperature and polarization fields obtained by crosscorrelating the reconstructed convergence signal from the first season of ACTPol data at 146 GHz with Cosmic Infrared Background (CIB) fluctuations measured using the Planck satellite. Using an overlap area of 206 square degrees, we detect gravitational lensing of the CMB polarization by largescale structure at a statistical significance of 4.5 sigma. Combining both CMB temperature and polarization data gives a lensing detection at 9.1 sigma significance. A Bmode polarization lensing signal is present with a significance of 3.2 sigma. We also present the first measurement of CMB lensingCIB correlation at small scales corresponding to l > 2000. Null tests and systematic checks show that our results are not significantly biased by astrophysical or instrumental systematic effects, including Galactic dust. Fitting our measurements to the bestfit lensingCIB cross power spectrum measured in Planck data, scaled by an amplitude A, gives A=1.02 +0.12/0.18 (stat.) +/0.06(syst.), consistent with the Planck results.The Astrophysical Journal 07/2015; 808(1). DOI:10.1088/0004637X/808/1/7 · 5.99 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: This paper presents the Planck 2015 likelihoods, statistical descriptions of the 2point correlation functions of CMB temperature and polarization. They use the hybrid approach employed previously: pixelbased at low multipoles, $\ell$, and a Gaussian approximation to the distribution of crosspower spectra at higher $\ell$. The main improvements are the use of more and better processed data and of Planck polarization data, and more detailed foreground and instrumental models. More than doubling the data allows further checks and enhanced immunity to systematics. Progress in foreground modelling enables a larger sky fraction, contributing to enhanced precision. Improvements in processing and instrumental models further reduce uncertainties. Extensive tests establish robustness and accuracy, from temperature, from polarization, and from their combination, and show that the {\Lambda}CDM model continues to offer a very good fit. We further validate the likelihood against specific extensions to this baseline, such as the effective number of neutrino species. For this first detailed analysis of Planck polarization, we concentrate at high $\ell$ on E modes. At low $\ell$ we use temperature at all Planck frequencies along with a subset of polarization. These data take advantage of Planck's wide frequency range to improve the separation of CMB and foregrounds. Within the baseline cosmology this requires a reionization optical depth $\tau=0.078\pm0.019$, significantly lower than without highfrequency data for explicit dust monitoring. At high $\ell$ we detect residual errors in E, typically at the {\mu}K$^2$ level; we thus recommend temperature alone as the high$\ell$ baseline. Nevertheless, Planck high$\ell$ polarization spectra are already good enough to allow a separate highaccuracy determination of the {\Lambda}CDM parameters, consistent with those established from temperature alone.  [Show abstract] [Hide abstract]
ABSTRACT: The quest for a $B$mode imprint from primordial gravity waves on the polarization of the cosmic microwave background (CMB) requires the characterization of foreground polarization from Galactic dust. We present a statistical study of the filamentary structure of the $353\,$GHz Planck Stokes maps at high Galactic latitude, relevant to the study of dust emission as a polarized foreground to the CMB. We filter the intensity and polarization maps to isolate filaments in the range of angular scales where the power asymmetry between $E$modes and $B$modes is observed. Using the Smoothed Hessian Major Axis Filament Finder, we identify 259 filaments at high Galactic latitude, with lengths larger or equal to $2$\deg\ (corresponding to $3.5\,$pc in length for a typical distance of $100\,$pc). These filaments show a preferred orientation parallel to the magnetic field projected onto the plane of the sky, derived from their polarization angles. We present mean maps of the filaments in Stokes $I$, $Q$, $U$, $E$, and $B$, computed by stacking individual images rotated to align the orientations of the filaments. Combining the stacked images and the histogram of relative orientations, we estimate the mean polarization fraction of the filaments to be $11\,$%. Furthermore, we show that the correlation between the filaments and the magnetic field orientations may account for the $E$ and $B$ asymmetry and the $C_{\ell}^{TE}/C_{\ell}^{EE}$ ratio, reported in the power spectra analysis of the Planck $353\,$GHz polarization maps. Future models of the dust foreground for CMB polarization studies will need to take into account the observed correlation between the dust polarization and the structure of interstellar matter.  [Show abstract] [Hide abstract]
ABSTRACT: This paper was published online on 13 April 2015 with an error in an author’s name. The seventh author’s name should read as “Jerod Caligiuri.” The author’s name has been corrected as of 17 April 2015. The author’s name is correct in the printed version of the journal.Physical Review Letters 05/2015; 114(18). DOI:10.1103/PhysRevLett.114.189901 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present a statistical detection of the gravitational lensing of the cosmic microwave background by $10^{13}$ solar mass dark matter halos. Lensing convergence maps from the Atacama Cosmology Telescope Polarimeter (ACTPol) are stacked at the positions of around 12,000 opticallyselected CMASS galaxies from the SDSSIII/BOSS survey. The mean lensing signal is consistent with simulated dark matter halo profiles, and is favored over a null signal at 3.2 sigma significance. This result demonstrates the potential of microwave background lensing to probe the dark matter distribution in galaxy group and galaxy cluster halos.Physical Review Letters 04/2015; 114(15):151302. DOI:10.1103/PhysRevLett.114.151302 · 7.51 Impact Factor  [Show abstract] [Hide abstract]
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 
Article: The Atacama Cosmology Telescope: measuring radio galaxy bias through crosscorrelation with lensing
[Show abstract] [Hide abstract]
ABSTRACT: We correlate the positions of radio galaxies in the FIRST survey with the CMB lensing convergence estimated from the Atacama Cosmology Telescope over 470 square degrees to determine the bias of these galaxies. We remove optically crossmatched sources below redshift $z=0.2$ to preferentially select Active Galactic Nuclei (AGN). We measure the angular crosspower spectrum $C_l^{\kappa g}$ at $4.4\sigma$ significance in the multipole range $100<l<3000$, corresponding to physical scales between $\approx$ 260 Mpc at an effective redshift $z_{\rm eff}= 1.5$. Modelling the AGN population with a redshiftdependent bias, the crossspectrum is well fit by the Planck bestfit $\Lambda$CDM cosmological model. Fixing the cosmology we fit for the overall bias model normalization, finding $b(z_{\rm eff}) = 3.5 \pm 0.8$ for the full galaxy sample, and $b(z_{\rm eff})=4.0\pm1.1 (3.0\pm1.1)$ for sources brighter (fainter) than 2.5 mJy. This measurement characterizes the typical halo mass of radioloud AGN: we find $\log(M_{\rm halo} / M_\odot) = 13.6^{+0.3}_{0.4}$.Monthly Notices of the Royal Astronomical Society 02/2015; 451(1). DOI:10.1093/mnras/stv991 · 5.11 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present results based on fullmission Planck observations of temperature and polarization anisotropies of the CMB. These data are consistent with the sixparameter inflationary LCDM cosmology. From the Planck temperature and lensing data, for this cosmology we find a Hubble constant, H0= (67.8 +/ 0.9) km/s/Mpc, a matter density parameter Omega_m = 0.308 +/ 0.012 and a scalar spectral index with n_s = 0.968 +/ 0.006. (We quote 68% errors on measured parameters and 95% limits on other parameters.) Combined with Planck temperature and lensing data, Planck LFI polarization measurements lead to a reionization optical depth of tau = 0.066 +/ 0.016. Combining Planck with other astrophysical data we find N_ eff = 3.15 +/ 0.23 for the effective number of relativistic degrees of freedom and the sum of neutrino masses is constrained to < 0.23 eV. Spatial curvature is found to be Omega_K < 0.005. For LCDM we find a limit on the tensortoscalar ratio of r <0.11 consistent with the Bmode constraints from an analysis of BICEP2, Keck Array, and Planck (BKP) data. Adding the BKP data leads to a tighter constraint of r < 0.09. We find no evidence for isocurvature perturbations or cosmic defects. The equation of state of dark energy is constrained to w = 1.006 +/ 0.045. Standard big bang nucleosynthesis predictions for the Planck LCDM cosmology are in excellent agreement with observations. We investigate annihilating dark matter and deviations from standard recombination, finding no evidence for new physics. The Planck results for base LCDM are in agreement with BAO data and with the JLA SNe sample. However the amplitude of the fluctuations is found to be higher than inferred from rich cluster counts and weak gravitational lensing. Apart from these tensions, the base LCDM cosmology provides an excellent description of the Planck CMB observations and many other astrophysical data sets.  [Show abstract] [Hide abstract]
ABSTRACT: We present the most significant measurement of the cosmic microwave background (CMB) lensing potential to date (at a level of 40 sigma), using temperature and polarization data from the Planck 2015 fullmission release. Using a polarizationonly estimator we detect lensing at a significance of 5 sigma. We crosscheck the accuracy of our measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements. Public products based on this measurement include an estimate of the lensing potential over approximately 70% of the sky, an estimate of the lensing potential power spectrum in bandpowers for the multipole range 40<L<400 and an associated likelihood for cosmological parameter constraints. We find good agreement between our measurement of the lensing potential power spectrum and that found in the bestfitting LCDM model based on the Planck temperature and polarization power spectra. Using the lensing likelihood alone we obtain a percentlevel measurement of the parameter combination Sigma_8 Omega_m^{0.25} = 0.591+0.021. We combine our determination of the lensing potential with the Emode polarization also measured by Planck to generate an estimate of the lensing Bmode. We show that this lensing Bmode estimate is correlated with the Bmodes observed directly by Planck at the expected level and with a statistical significance of 10 sigma, confirming Planck's sensitivity to this known sky signal. We also correlate our lensing potential estimate with the largescale temperature anisotropies, detecting a crosscorrelation at the 3 sigma level, as expected due to dark energy in the concordance LCDM model. 

 [Show abstract] [Hide abstract]
ABSTRACT: We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400 deg$^2$ patch of sky centered on RA 0h, Dec. $57.5\deg$. The combined maps reach a depth of 57 nK deg in Stokes $Q$ and $U$ in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2 $\mu$K deg in $Q$ and $U$ at 143 GHz). We detect 150$\times$353 crosscorrelation in $B$modes at high significance. We fit the single and crossfrequency power spectra at frequencies above 150 GHz to a lensed$\Lambda$CDM model that includes dust and a possible contribution from inflationary gravitational waves (as parameterized by the tensortoscalar ratio $r$). We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the $r$ constraint. Finally we present an alternative analysis which is similar to a mapbased cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for $r$, and yields an upper limit $r_{0.05}<0.12$ at 95% confidence. Marginalizing over dust and $r$, lensing $B$modes are detected at $7.0\,\sigma$ significance.Physical Review Letters 02/2015; 114(10). DOI:10.1103/PhysRevLett.114.101301 · 7.51 Impact Factor 
Article: The Atacama Cosmology Telescope: A Measurement of the Thermal SunyaevZel'dovich OnePoint PDF
[Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the onepoint probability distribution function (PDF) of the thermal SunyaevZel'dovich (tSZ) decrement in the pixel temperature histogram of filtered 148 GHz sky maps from the Atacama Cosmology Telescope (ACT). The PDF includes the signal from all galaxy clusters in the map, including objects below the signaltonoise threshold for individual detection, making it a particularly sensitive probe of the amplitude of matter density perturbations, $\sigma_8$. We use a combination of analytic halo model calculations and numerical simulations to compute the theoretical tSZ PDF and its covariance matrix, accounting for all noise sources and including relativistic corrections. From the measured ACT 148 GHz PDF alone, we find $\sigma_8 = 0.793 \pm 0.018$, with additional systematic errors of $\pm 0.017$ due to uncertainty in intracluster medium gas physics and $\pm 0.006$ due to uncertainty in infrared point source contamination. Using effectively the same data set, the statistical error here is a factor of two lower than that found in ACT's previous $\sigma_8$ determination based solely on the skewness of the tSZ signal. In future temperature maps with higher sensitivity, the tSZ PDF will break the degeneracy between intracluster medium gas physics and cosmological parameters.  [Show abstract] [Hide abstract]
ABSTRACT: 43 pages, 25 figures, 12 tables ; Received: 25 March 2013 / Accepted: 28 January 2014 

Publication Stats
15k  Citations  
549.36  Total Impact Points  
Top Journals
Institutions

2004–2015

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


2009–2013

University of Toronto
 Canadian Institute for Theoretical Astrophysics
Toronto, Ontario, Canada


2012

The University of Tokyo
 Institute for the Physics and Mathematics of the Universe (IPMU)
Edo, Tōkyō, Japan 
Johns Hopkins University
 Department of Physics and Astronomy
Baltimore, Maryland, United States


2006–2011

Princeton University
 • Department of Astrophysical Sciences
 • Department of Physics
Princeton, NJ, United States
