Time filter

Source Type

Broadway, CO, United States

Reichardt C.L.,University of California at Berkeley | Shaw L.,Yale University | Zahn O.,University of California at Berkeley | Aird K.A.,University of Chicago | And 53 more authors.
Astrophysical Journal | Year: 2012

We present the first three-frequency South Pole Telescope (SPT) cosmic microwave background (CMB) power spectra. The band powers presented here cover angular scales 2000 < ℓ < 9400 in frequency bands centered at 95, 150, and 220 GHz. At these frequencies and angular scales, a combination of the primary CMB anisotropy, thermal and kinetic Sunyaev-Zel'dovich (SZ) effects, radio galaxies, and cosmic infrared background (CIB) contributes to the signal. We combine Planck/HFI and SPT data at 220 GHz to constrain the amplitude and shape of the CIB power spectrum and find strong evidence for nonlinear clustering. We explore the SZ results using a variety of cosmological models for the CMB and CIB anisotropies and find them to be robust with one exception: allowing for spatial correlations between the thermal SZ effect and CIB significantly degrades the SZ constraints. Neglecting this potential correlation, we find the thermal SZ power at 150 GHz and ℓ = 3000 to be 3.65 ± 0.69 μK2, and set an upper limit on the kinetic SZ power to be less than 2.8 μK2 at 95% confidence. When a correlation between the thermal SZ and CIB is allowed, we constrain a linear combination of thermal and kinetic SZ power: D tSZ 3000 + 0.5D 3000 kSZ = 4.60 ± 0.63 μK2, consistent with earlier measurements. We use the measured thermal SZ power and an analytic, thermal SZ model calibrated with simulations to determine σ8 = 0.807 ± 0.016. Modeling uncertainties involving the astrophysics of the intracluster medium rather than the statistical uncertainty in the measured band powers are the dominant source of uncertainty on σ8. We also place an upper limit on the kinetic SZ power produced by patchy reionization; a companion paper uses these limits to constrain the reionization history of the universe. © 2012 The American Astronomical Society. All rights reserved. Source

Hou Z.,University of California at Davis | Reichardt C.L.,University of California at Berkeley | Story K.T.,University of Chicago | Follin B.,University of California at Davis | And 59 more authors.
Astrophysical Journal | Year: 2014

We explore extensions to the ΛCDM cosmology using measurements of the cosmic microwave background (CMB) from the recent SPT-SZ survey, along with data from WMAP7 and measurements of H 0 and baryon acoustic oscillation (BAO). We check for consistency within ΛCDM between these data sets, and find some tension. The CMB alone gives weak support to physics beyond ΛCDM, due to a slight trend relative to ΛCDM of decreasing power toward smaller angular scales. While it may be due to statistical fluctuation, this trend could also be explained by several extensions. We consider running of the primordial spectral index (dns /dln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Yp and the effective number of neutrino species N eff) and one that modifies the large-scale power due to the integrated Sachs-Wolfe effect (the sum of neutrino masses ∑m ν). These extensions have similar observational consequences and are partially degenerate when considered simultaneously. Of the six one-parameter extensions considered, we find CMB to have the largest preference for dns /dln k with -0.046 < dns /dln k < -0.003 at 95% confidence, which strengthens to a 2.7σ indication of dns /dln k < 0 from CMB+BAO+H 0. Detectable dns /dln k ≠ 0 is difficult to explain in the context of single-field, slow-roll inflation models. We find N eff = 3.62 ± 0.48 for the CMB, which tightens to N eff = 3.71 ± 0.35 from CMB+BAO+H 0. Larger values of N eff relieve the mild tension between CMB, BAO, and H 0. When the Sunyaev-Zel'dovich selected galaxy cluster abundances () data are also included, we obtain N eff = 3.29 ± 0.31. Allowing for ∑m ν gives a 3.0σ detection of ∑m ν > 0 from CMB+BAO+H 0 +. The median value is (0.32 ± 0.11) eV, a factor of six above the lower bound set by neutrino oscillation observations. All data sets except H 0 show some preference for massive neutrinos; data combinations including H 0 favor nonzero masses only if BAO data are also included. We also constrain the two-parameter extensions N eff + ∑m ν and N eff + Yp to explore constraints on additional light species and big bang nucleosynthesis, respectively. © 2014. The American Astronomical Society. All rights reserved.. Source

Menanteau F.,Rutgers University | Hughes J.P.,Rutgers University | Sifon C.,University of Santiago de Chile | Hilton M.,University of Nottingham | And 24 more authors.
Astrophysical Journal | Year: 2012

We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CLJ0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CLJ0102-4915 as the most significant SZ decrement in a sky survey area of 755deg2. Our Very Large Telescope (VLT)/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, σgal = 1321 106kms-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T X = 14.5 0.1keV and 0.5-2.0keV band luminosity of L X = (2.19 ± 0.11) × 1045 h -2 70ergs-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y X, and integrated SZ distortion, we estimate a cluster mass of M 200a = (2.16 ± 0.32) × 1015 h -1 70 M ⊙. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CLJ0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6 0.7keV at the merging low-entropy, high-metallicity, cool core to a high of 22 6keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CLJ0102-4915 is possibly a high-redshift analog of the famous Bullet cluster. Such a massive cluster at this redshift is rare, although consistent with the standard ΛCDM cosmology in the lower part of its allowed mass range. Massive, high-redshift mergers like ACT-CLJ0102-4915 are unlikely to be reproduced in the current generation of numerical N-body cosmological simulations. © 2012 The American Astronomical Society. All rights reserved. Source

Sherwin B.D.,Princeton University | Dunkley J.,Princeton University | Dunkley J.,University of Oxford | Das S.,Princeton University | And 44 more authors.
Physical Review Letters | Year: 2011

For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w=-1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density ΩΛ confirms other measurements from supernovae, galaxy clusters, and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool. © 2011 American Physical Society. Source

Story K.T.,University of Chicago | Reichardt C.L.,University of California at Berkeley | Hou Z.,University of California at Davis | Keisler R.,University of Chicago | And 54 more authors.
Astrophysical Journal | Year: 2013

We present a measurement of the cosmic microwave background (CMB) temperature power spectrum using data from the recently completed South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. This measurement is made from observations of 2540 deg2 of sky with arcminute resolution at 150 GHz, and improves upon previous measurements using the SPT by tripling the sky area. We report CMB temperature anisotropy power over the multipole range 650 < ℓ < 3000. We fit the SPT bandpowers, combined with the 7 yr Wilkinson Microwave Anisotropy Probe (WMAP7) data, with a six-parameter ΛCDM cosmological model and find that the two datasets are consistent and well fit by the model. Adding SPT measurements significantly improves ΛCDM parameter constraints; in particular, the constraint on θ s tightens by a factor of 2.7. The impact of gravitational lensing is detected at 8.1σ, the most significant detection to date. This sensitivity of the SPT+WMAP7 data to lensing by large-scale structure at low redshifts allows us to constrain the mean curvature of the observable universe with CMB data alone to be . Using the SPT+WMAP7 data, we measure the spectral index of scalar fluctuations to be ns = 0.9623 ± 0.0097 in the ΛCDM model, a 3.9σ preference for a scale-dependent spectrum with ns < 1. The SPT measurement of the CMB damping tail helps break the degeneracy that exists between the tensor-to-scalar ratio r and ns in large-scale CMB measurements, leading to an upper limit of r < 0.18 (95% C.L.) in the ΛCDM+r model. Adding low-redshift measurements of the Hubble constant (H 0) and the baryon acoustic oscillation (BAO) feature to the SPT+WMAP7 data leads to further improvements. The combination of SPT+WMAP7+H 0+BAO constrains ns = 0.9538 ± 0.0081 in the ΛCDM model, a 5.7σ detection of ns < 1, and places an upper limit of r < 0.11 (95% C.L.) in the ΛCDM+r model. These new constraints on ns and r have significant implications for our understanding of inflation, which we discuss in the context of selected single-field inflation models. © 2013. The American Astronomical Society. All rights reserved.. Source

Discover hidden collaborations