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Sample records for background power spectrum

  1. Fast cosmic microwave background power spectrum estimation of temperature and polarization with Gabor transforms

    NASA Astrophysics Data System (ADS)

    Hansen, Frode K.; Górski, Krzysztof M.

    2003-08-01

    We extend the analysis of Gabor transforms on a cosmic microwave background temperature map to polarization. We study the temperature and polarization power spectra on the cut sky, the so-called pseudo-power spectra. The transformation kernels relating the full-sky polarization power spectra and the polarization pseudo-power spectra are found to be similar to the kernel for the temperature power spectrum. This fact is used to construct a fast power spectrum estimation algorithm using the pseudo-power spectrum of temperature and polarization as data vectors in a maximum-likelihood approach. Using the pseudo-power spectra as input to the likelihood analysis solves the problem of having to invert huge matrices, which makes the standard likelihood approach infeasible.

  2. Angular power spectrum of the FASTICA cosmic microwave background component from Background Emission Anisotropy Scanning Telescope data

    NASA Astrophysics Data System (ADS)

    Donzelli, S.; Maino, D.; Bersanelli, M.; Childers, J.; Figueiredo, N.; Lubin, P. M.; Meinhold, P. R.; O'Dwyer, I. J.; Seiffert, M. D.; Villela, T.; Wandelt, B. D.; Wuensche, C. A.

    2006-06-01

    We present the angular power spectrum of the cosmic microwave background (CMB) component extracted with FASTICA from the Background Emission Anisotropy Scanning Telescope (BEAST) data. BEAST is a 2.2-m off-axis telescope with a focal plane comprising eight elements at Q (38-45 GHz) and Ka (26-36 GHz) bands. It operates from the UC (University of California) White Mountain Research Station at an altitude of 3800 m. The BEAST CMB angular power spectrum has already been calculated by O'Dwyer et al. using only the Q-band data. With two input channels, FASTICA returns two possible independent components. We found that one of these two has an unphysical spectral behaviour, while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte Carlo (MC) simulations, we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum and with the Wilkinson Microwave Anisotropy Probe (WMAP) data.

  3. What can be learned from the lensed cosmic microwave background B-mode polarization power spectrum?

    SciTech Connect

    Smith, Sarah; Challinor, Anthony; Rocha, Graca

    2006-01-15

    The effect of weak gravitational lensing on the cosmic microwave background (CMB) temperature anisotropies and polarization will provide access to cosmological information that cannot be obtained from the primary anisotropies alone. We compare the information content of the lensed B-mode polarization power spectrum, properly accounting for the non-Gaussian correlations between the power on different scales, with that of the unlensed CMB fields and the lensing potential. The latter represent the products of an (idealized) optimal analysis that exploits the lens-induced non-Gaussianity to reconstruct the fields. Compressing the non-Gaussian lensed CMB into power spectra is wasteful and leaves a tight degeneracy between the equation of state of dark energy and neutrino mass that is much stronger than in the more optimal analysis. Despite this, a power-spectrum analysis will be a useful first step in analyzing future B-mode polarization data. For this reason, we also consider how to extract accurate parameter constraints from the lensed B-mode power spectrum. We show with simulations that for cosmic-variance-limited measurements of the lensed B-mode power, including the non-Gaussian correlations in existing likelihood approximations gives biased parameter results. We develop a more refined likelihood approximation that performs significantly better. This new approximation should also be of more general interest in the wider context of parameter estimation from Gaussian CMB data.

  4. PROBING THE INFLATON: SMALL-SCALE POWER SPECTRUM CONSTRAINTS FROM MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND ENERGY SPECTRUM

    SciTech Connect

    Chluba, Jens; Erickcek, Adrienne L.; Ben-Dayan, Ido

    2012-10-20

    In the early universe, energy stored in small-scale density perturbations is quickly dissipated by Silk damping, a process that inevitably generates {mu}- and y-type spectral distortions of the cosmic microwave background (CMB). These spectral distortions depend on the shape and amplitude of the primordial power spectrum at wavenumbers k {approx}< 10{sup 4} Mpc{sup -1}. Here, we study constraints on the primordial power spectrum derived from COBE/FIRAS and forecasted for PIXIE. We show that measurements of {mu} and y impose strong bounds on the integrated small-scale power, and we demonstrate how to compute these constraints using k-space window functions that account for the effects of thermalization and dissipation physics. We show that COBE/FIRAS places a robust upper limit on the amplitude of the small-scale power spectrum. This limit is about three orders of magnitude stronger than the one derived from primordial black holes in the same scale range. Furthermore, this limit could be improved by another three orders of magnitude with PIXIE, potentially opening up a new window to early universe physics. To illustrate the power of these constraints, we consider several generic models for the small-scale power spectrum predicted by different inflation scenarios, including running-mass inflation models and inflation scenarios with episodes of particle production. PIXIE could place very tight constraints on these scenarios, potentially even ruling out running-mass inflation models if no distortion is detected. We also show that inflation models with sub-Planckian field excursion that generate detectable tensor perturbations should simultaneously produce a large CMB spectral distortion, a link that could potentially be established with PIXIE.

  5. Angular power spectrum of the microwave background anisotropy seen by the COBE differential microwave radiometer

    NASA Technical Reports Server (NTRS)

    Wright, E. L.; Smoot, G. F.; Bennett, C. L.; Lubin, P. M.

    1994-01-01

    The angular power spectrum estimator developed by Peebles (1973) and Hauser & Peebles (1973) has been modified and applied to the 2 yr maps produced by the Cosmic Background Explorer Satellite Differential Microwave Radiometer (COBE DMR)). The power spectrum of the real sky has been compared to the power spectra of a large number of simulated random skies produced with noise equal to the observed noise and primordial density fluctuation power spectra of power-law form, with P(k) proportional to k(exp n). Within the limited range of spatial scales covered by the COBE DMR, corresponding to spherical harmonic indices 3 less than or = l is less than or approximately = 30, the best-fitting value of the spectral index is n = 1.25(sup +0.39 sub -0.44) with the Harrisson-Zel'dovich value n = 1 approximately 0.5 sigma below the best fit. For 3 less than or = l less than or approximately = 19, the best fit is n = 1.46(sup +0.39 sub -0.44). Comparing the COBE DMR delta-T/T at small l to the delta-T/T at l approximately = 50 from degree scale anisotropy experiments gives a smaller range of acceptable spectral indices which includes n = 1.

  6. Bayesian Analysis of the Power Spectrum of the Cosmic Microwave Background

    NASA Technical Reports Server (NTRS)

    Jewell, Jeffrey B.; Eriksen, H. K.; O'Dwyer, I. J.; Wandelt, B. D.

    2005-01-01

    There is a wealth of cosmological information encoded in the spatial power spectrum of temperature anisotropies of the cosmic microwave background. The sky, when viewed in the microwave, is very uniform, with a nearly perfect blackbody spectrum at 2.7 degrees. Very small amplitude brightness fluctuations (to one part in a million!!) trace small density perturbations in the early universe (roughly 300,000 years after the Big Bang), which later grow through gravitational instability to the large-scale structure seen in redshift surveys... In this talk, I will discuss a Bayesian formulation of this problem; discuss a Gibbs sampling approach to numerically sampling from the Bayesian posterior, and the application of this approach to the first-year data from the Wilkinson Microwave Anisotropy Probe. I will also comment on recent algorithmic developments for this approach to be tractable for the even more massive data set to be returned from the Planck satellite.

  7. The Cosmic Microwave Background Anisotropy Power Spectrum from the BEAST Experiment

    NASA Astrophysics Data System (ADS)

    O'Dwyer, Ian J.; Bersanelli, Marco; Childers, Jeffrey; Figueiredo, Newton; Halevi, Doron; Huey, Greg; Lubin, Philip M.; Maino, Davide; Mandolesi, Nazzareno; Marvil, Joshua; Meinhold, Peter R.; Mejía, Jorge; Natoli, Paolo; O'Neill, Hugh; Pina, Agenor; Seiffert, Michael D.; Stebor, Nathan C.; Tello, Camilo; Villela, Thyrso; Wandelt, Benjamin D.; Williams, Brian; Wuensche, Carlos Alexandre

    2005-05-01

    The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2 m off-axis telescope with an eight-element mixed Q-band (38-45 GHz) and Ka-band (26-36 GHz) focal plane, designed for balloon-borne and ground-based studies of the cosmic microwave background (CMB). Here we present the CMB angular power spectrum calculated from 682 hr of data observed with the BEAST instrument. We use a binned pseudo-Cl estimator (the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumbers l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produce a good constraint on Ωk≡1-Ωtot=-0.074+/-0.070, consistent with a flat universe. A joint parameter estimation analysis with a number of previous CMB experiments produces results consistent with previous determinations.

  8. Effect of background trends removal on noise power spectrum measurements in digital x-ray imaging

    NASA Astrophysics Data System (ADS)

    Zhou, Zhongxing; Gao, Feng; Zhao, Huijuan; Zhang, Lixin

    2011-03-01

    Noise characterization through estimation of the noise power spectrum (NPS) is a central component of the evaluation of digital X-ray systems. Extensive works have been conducted to achieve accurate and precise measurement of NPS. One approach to improve the accuracy of the NPS measurement is to reduce the statistical variance of the NPS results. However, this method is based on the assumption that the noise in a radiographic image is arising from stochastic (random) processes. In the practical data, the artifactuals always superimpose on the stochastic noise as low-frequency background trends and prevent us from achieving accurate NPS. In this study, NPS measurement was implemented and compared before and after background trends removal, the results showed that background detrending reduced the variance of the low-frequency spectral components, hence improving the accuracy of NPS measurement. Our results also showed that involving more samples for ensemble averaging had little effect in reducing the variance of the low-frequency spectral components. All results implied that it is necessary and feasible to get better NPS estimate by appropriate background detredning.

  9. Second Season QUIET Observations: Measurements of the Cosmic Microwave Background Polarization Power Spectrum at 95 GHz

    NASA Astrophysics Data System (ADS)

    QUIET Collaboration; Araujo, D.; Bischoff, C.; Brizius, A.; Buder, I.; Chinone, Y.; Cleary, K.; Dumoulin, R. N.; Kusaka, A.; Monsalve, R.; Næss, S. K.; Newburgh, L. B.; Reeves, R.; Wehus, I. K.; Zwart, J. T. L.; Bronfman, L.; Bustos, R.; Church, S. E.; Dickinson, C.; Eriksen, H. K.; Gaier, T.; Gundersen, J. O.; Hasegawa, M.; Hazumi, M.; Huffenberger, K. M.; Ishidoshiro, K.; Jones, M. E.; Kangaslahti, P.; Kapner, D. J.; Kubik, D.; Lawrence, C. R.; Limon, M.; McMahon, J. J.; Miller, A. D.; Nagai, M.; Nguyen, H.; Nixon, G.; Pearson, T. J.; Piccirillo, L.; Radford, S. J. E.; Readhead, A. C. S.; Richards, J. L.; Samtleben, D.; Seiffert, M.; Shepherd, M. C.; Smith, K. M.; Staggs, S. T.; Tajima, O.; Thompson, K. L.; Vanderlinde, K.; Williamson, R.

    2012-12-01

    The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 μK\\sqrt{s}. Four low-foreground fields were observed, covering a total of ~1000 deg2 with an effective angular resolution of 12farcm8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C l (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with ΛCDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1+0.9 - 0.8 (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2+0.9 - 0.8 (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

  10. SECOND SEASON QUIET OBSERVATIONS: MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRUM AT 95 GHz

    SciTech Connect

    Araujo, D.; Dumoulin, R. N.; Newburgh, L. B.; Zwart, J. T. L.; Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A.; Chinone, Y.; Cleary, K.; Reeves, R.; Naess, S. K.; Eriksen, H. K.; Wehus, I. K.; Bronfman, L.; Church, S. E.; Dickinson, C.; Gaier, T.; Collaboration: QUIET Collaboration; and others

    2012-12-01

    The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 {mu}K{radical}s. Four low-foreground fields were observed, covering a total of {approx}1000 deg{sup 2} with an effective angular resolution of 12.'8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C {sub l} (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with {Lambda}CDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1{sup +0.9} {sub -0.8} (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2{sup +0.9} {sub -0.8} (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

  11. A measurement by BOOMERANG of multiple peaks in the angular power spectrum of the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Netterfield, C. B.; Ade, P. A. R.; Bock, J. J.; Bond, J. R.; Borrill, J.; Boscaleri, A.; Coble, K.; Contaldi, C. R.; Crill, B. P.; Bernardis, P. de; Farese, P.; Ganga, K.; Giacometti, M.; Hivon, E.; Hristov, V. V.; Iacoangeli, A.; Jaffe, A. H.; Jones, W. C.; Lange, A. E.; Martinis, L.; Masi, S.; Mason, P.; Mauskopf, P.; Melchiorri, A.; Montroy, T.

    2001-01-01

    This paper presents a measurement of the angular power spectrum of the Cosmic Microwave Background from l = 75 to l = 1025 (10' to 5 degrees) from a combined analysis of four 150 GHz channels in the BOOMERANG experiment. The spectrum contains multiple peaks and minima, as predicted by standard adiabatic-inflationary models in which the primordial plasma undergoes acoustic oscillations.

  12. Anatomical background noise power spectrum in differential phase contrast breast images

    NASA Astrophysics Data System (ADS)

    Garrett, John; Ge, Yongshuai; Li, Ke; Chen, Guang-Hong

    2015-03-01

    In x-ray breast imaging, the anatomical noise background of the breast has a significant impact on the detection of lesions and other features of interest. This anatomical noise is typically characterized by a parameter, β, which describes a power law dependence of anatomical noise on spatial frequency (the shape of the anatomical noise power spectrum). Large values of β have been shown to reduce human detection performance, and in conventional mammography typical values of β are around 3.2. Recently, x-ray differential phase contrast (DPC) and the associated dark field imaging methods have received considerable attention as possible supplements to absorption imaging for breast cancer diagnosis. However, the impact of these additional contrast mechanisms on lesion detection is not yet well understood. In order to better understand the utility of these new methods, we measured the β indices for absorption, DPC, and dark field images in 15 cadaver breast specimens using a benchtop DPC imaging system. We found that the measured β value for absorption was consistent with the literature for mammographic acquisitions (β = 3.61±0.49), but that both DPC and dark field images had much lower values of β (β = 2.54±0.75 for DPC and β = 1.44±0.49 for dark field). In addition, visual inspection showed greatly reduced anatomical background in both DPC and dark field images. These promising results suggest that DPC and dark field imaging may help provide improved lesion detection in breast imaging, particularly for those patients with dense breasts, in whom anatomical noise is a major limiting factor in identifying malignancies.

  13. Power spectrum constraints from spectral distortions in the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Hu, Wayne; Scott, Douglas; Silk, Joseph

    1994-01-01

    Using recent experimental limits on chemical potential distortions from Cosmic Background Explorer (COBE) Far Infrared Astronomy Satellite (FIRAS), and the large lever-arm spanning the damping of sub-Jeans scale fluctuations to the COBE DMR fluctuations, we set a constraint on the slope of the primordial power spectrum n. It is possible to analytically calculate the contribution over the full range of scales and redshifts, correctly taking into account fluctuation growth and damping as well as thermalization processes. Assuming conservatively that mu is less than 1.76 x 10(exp -4), we find that the 95% upper limit on n is only weakly dependent on other cosmological parameters, e.g., n is less than 1.60 (h=0.5) and n is less than 1.63 (h=1.0) for Omega(sub 0) = 1, with marginally weaker constraints for Omega(sub 0) is less than 1 in a flat model with a cosmological constant.

  14. DIRECT MEASUREMENT OF THE ANGULAR POWER SPECTRUM OF COSMIC MICROWAVE BACKGROUND TEMPERATURE ANISOTROPIES IN THE WMAP DATA

    SciTech Connect

    Chiang, Lung-Yih; Chen, Fei-Fan

    2012-05-20

    The angular power spectrum of the cosmic microwave background temperature anisotropies is one of the most important characteristics in cosmology that can shed light on the properties of the universe such as its geometry and total density. Using flat sky approximation and Fourier analysis, we estimate the angular power spectrum from an ensemble of the least foreground-contaminated square patches from the Wilkinson Microwave Anisotropy Probe W and V frequency band map. This method circumvents the issue of foreground cleaning and that of breaking orthogonality in spherical harmonic analysis because we are able to mask out the bright Galactic plane region, thereby rendering a direct measurement of the angular power spectrum. We test and confirm the Gaussian statistical characteristic of the selected patches, from which the first and second acoustic peaks of the power spectrum are reproduced, and the third peak is clearly visible, albeit with some noise residual at the tail.

  15. Probing reionization with the cross-power spectrum of 21 cm and near-infrared radiation backgrounds

    SciTech Connect

    Mao, Xiao-Chun

    2014-08-01

    The cross-correlation between the 21 cm emission from the high-redshift intergalactic medium and the near-infrared (NIR) background light from high-redshift galaxies promises to be a powerful probe of cosmic reionization. In this paper, we investigate the cross-power spectrum during the epoch of reionization. We employ an improved halo approach to derive the distribution of the density field and consider two stellar populations in the star formation model: metal-free stars and metal-poor stars. The reionization history is further generated to be consistent with the electron-scattering optical depth from cosmic microwave background measurements. Then, the intensity of the NIR background is estimated by collecting emission from stars in first-light galaxies. On large scales, we find that the 21 cm and NIR radiation backgrounds are positively correlated during the very early stages of reionization. However, these two radiation backgrounds quickly become anti-correlated as reionization proceeds. The maximum absolute value of the cross-power spectrum is |Δ{sub 21,NIR}{sup 2}|∼10{sup −4} mK nW m{sup –2} sr{sup –1}, reached at ℓ ∼ 1000 when the mean fraction of ionized hydrogen is x-bar{sub i}∼0.9. We find that Square Kilometer Array can measure the 21 cm-NIR cross-power spectrum in conjunction with mild extensions to the existing CIBER survey, provided that the integration time independently adds up to 1000 and 1 hr for 21 cm and NIR observations, and that the sky coverage fraction of the CIBER survey is extended from 4 × 10{sup –4} to 0.1. Measuring the cross-correlation signal as a function of redshift provides valuable information on reionization and helps confirm the origin of the 'missing' NIR background.

  16. EVOLUTION OF THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM ACROSS WILKINSON MICROWAVE ANISOTROPY PROBE DATA RELEASES: A NONPARAMETRIC ANALYSIS

    SciTech Connect

    Aghamousa, Amir; Arjunwadkar, Mihir; Souradeep, Tarun E-mail: mihir@ncra.tifr.res.in

    2012-02-01

    Using a nonparametric function estimation methodology, we present a comparative analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) 1-, 3-, 5-, and 7-year data releases for the cosmic microwave background (CMB) angular power spectrum with respect to the following key questions. (1) How well is the power spectrum determined by the data alone? (2) How well is the {Lambda}CDM model supported by a model-independent, data-driven analysis? (3) What are the realistic uncertainties on peak/dip locations and heights? Our results show that the height of the power spectrum is well determined by data alone for multipole l approximately less than 546 (1-year), 667 (3-year), 804 (5-year), and 842 (7-year data). We show that parametric fits based on the {Lambda}CDM model are remarkably close to our nonparametric fits in l-regions where data are sufficiently precise. In contrast, the power spectrum for an H{Lambda}CDM model is progressively pushed away from our nonparametric fit as data quality improves with successive data realizations, suggesting incompatibility of this particular cosmological model with respect to the WMAP data sets. We present uncertainties on peak/dip locations and heights at the 95% (2{sigma}) level of confidence and show how these uncertainties translate into hyperbolic 'bands' on the acoustic scale (l{sub A} ) and peak shift ({phi}{sub m}) parameters. Based on the confidence set for the 7-year data, we argue that the low-l upturn in the CMB power spectrum cannot be ruled out at any confidence level in excess of about 10% ( Almost-Equal-To 0.12{sigma}). Additional outcomes of this work are a numerical formulation for minimization of a noise-weighted risk function subject to monotonicity constraints, a prescription for obtaining nonparametric fits that are closer to cosmological expectations on smoothness, and a method for sampling cosmologically meaningful power spectrum variations from the confidence set of a nonparametric fit.

  17. THE ATACAMA COSMOLOGY TELESCOPE: A MEASUREMENT OF THE 600 < l < 8000 COSMIC MICROWAVE BACKGROUND POWER SPECTRUM AT 148 GHz

    SciTech Connect

    Fowler, J. W.; Appel, J. W.; Das, S.; Dunkley, J.; Essinger-Hileman, T.; Fisher, R. P.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Barrientos, L. F.; Duenner, R.; Amiri, M.; Battistelli, E. S.; Burger, B.; Bond, J. R.; Brown, B.; Chervenak, J.; Doriese, W. B.

    2010-10-20

    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.'4 angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg{sup 2} of the southern sky, in a 4.{sup 0}2 wide strip centered on declination 53{sup 0} south. The CMB at arcminute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 < l < 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 < l < 1150. The power beyond the Silk damping tail of the CMB (l {approx} 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to {sigma}{sub 8} = 0.8. We constrain the model's amplitude A{sub SZ} < 1.63 (95% CL). If interpreted as a measurement of {sigma}{sub 8}, this implies {sigma}{sup SZ}{sub 8} < 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a six-parameter {Lambda}CDM model plus point sources and the SZ effect is consistent with these results.

  18. A Measurement of the Damping Tail of the Cosmic Microwave Background Power Spectrum with the South Pole Telescope

    NASA Astrophysics Data System (ADS)

    Keisler, R.; Reichardt, C. L.; Aird, K. A.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Dudley, J.; George, E. M.; Halverson, N. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hou, Z.; Hrubes, J. D.; Joy, M.; Knox, L.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Millea, M.; Mohr, J. J.; Montroy, T. E.; Natoli, T.; Padin, S.; Plagge, T.; Pryke, C.; Ruhl, J. E.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Spieler, H. G.; Staniszewski, Z.; Stark, A. A.; Story, K.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.; Zahn, O.

    2011-12-01

    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) using data from the South Pole Telescope (SPT). The data consist of 790 deg2 of sky observed at 150 GHz during 2008 and 2009. Here we present the power spectrum over the multipole range 650 < l < 3000, where it is dominated by primary CMB anisotropy. We combine this power spectrum with the power spectra from the seven-year Wilkinson Microwave Anisotropy Probe (WMAP) data release to constrain cosmological models. We find that the SPT and WMAP data are consistent with each other and, when combined, are well fit by a spatially flat, ΛCDM cosmological model. The SPT+WMAP constraint on the spectral index of scalar fluctuations is ns = 0.9663 ± 0.0112. We detect, at ~5σ significance, the effect of gravitational lensing on the CMB power spectrum, and find its amplitude to be consistent with the ΛCDM cosmological model. We explore a number of extensions beyond the ΛCDM model. Each extension is tested independently, although there are degeneracies between some of the extension parameters. We constrain the tensor-to-scalar ratio to be r < 0.21 (95% CL) and constrain the running of the scalar spectral index to be dns /dln k = -0.024 ± 0.013. We strongly detect the effects of primordial helium and neutrinos on the CMB; a model without helium is rejected at 7.7σ, while a model without neutrinos is rejected at 7.5σ. The primordial helium abundance is measured to be Yp = 0.296 ± 0.030, and the effective number of relativistic species is measured to be N eff = 3.85 ± 0.62. The constraints on these models are strengthened when the CMB data are combined with measurements of the Hubble constant and the baryon acoustic oscillation feature. Notable improvements include ns = 0.9668 ± 0.0093, r < 0.17 (95% CL), and N eff = 3.86 ± 0.42. The SPT+WMAP data show a mild preference for low power in the CMB damping tail, and while this preference may be accommodated by models that have a

  19. SMALL ANGULAR SCALE MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND TEMPERATURE POWER SPECTRUM FROM QUaD

    SciTech Connect

    Friedman, R. B.; Culverhouse, T.; Ade, P.; Bowden, M.; Gear, W. K.; Gupta, S.; Orlando, A.; Bock, J.; Leitch, E.; Brown, M. L.; Cahill, G.; Murphy, J. A.; Castro, P. G.; Memari, Y.; Church, S.; Hinderks, J.; Ganga, K.; Melhuish, S. J.

    2009-08-01

    We present measurements of the cosmic microwave background (CMB) radiation temperature anisotropy in the multipole range 2000 < l < 3000 from the QUaD telescope's second and third observing seasons. After masking the brightest point sources our results are consistent with the primary {lambda}CDM expectation alone. We estimate the contribution of residual (un-masked) radio point sources using a model calibrated to our own bright source observations, and a full simulation of the source finding and masking procedure. Including this contribution slightly improves the {chi}{sup 2}. We also fit a standard Sunyaev-Zel'dovich (SZ) template to the bandpowers and see no strong evidence of an SZ contribution, which is as expected for {sigma}{sub 8} {approx} 0.8.

  20. A CONSTRAINT ON THE INTEGRATED MASS POWER SPECTRUM OUT TO z = 1100 FROM LENSING OF THE COSMIC MICROWAVE BACKGROUND

    SciTech Connect

    Smidt, Joseph; Cooray, Asantha; Amblard, Alexandre; Joudaki, Shahab; Serra, Paolo; Munshi, Dipak; Santos, Mario G.

    2011-02-10

    The temperature fluctuations and polarization of the cosmic microwave background (CMB) are now a well-known probe of the universe at an infant age of 400,000 years. During the transit to us from the surface of last scattering, the CMB photons are expected to undergo modifications induced by the intervening large-scale structure. Among the expected secondary effects is the weak gravitational lensing of the CMB by the foreground dark matter distribution. We derive a quadratic estimator that uses the non-Gaussianities generated by the lensing effect at the four-point function level to extract the power spectrum of lensing potential fluctuations integrated out to z {approx} 1100 with peak contributions from potential fluctuations at z of 2-3. Using Wilkinson Microwave Anisotropy Probe seven-year temperature maps, we report the first direct constraints of this lensing potential power spectrum and find that it has an amplitude of A{sub L} = 0.96 {+-} 0.60, 1.06 {+-} 0.69, and 0.97 {+-} 0.47 using the W, V, and W + V bands, respectively.

  1. Measurement of the cosmic microwave background polarization lensing power spectrum with the POLARBEAR experiment.

    PubMed

    Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Linder, E; Leitch, E M; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Schanning, I; Schenck, D E; Sherwin, B; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tomaru, T; Wilson, B; Yadav, A; Zahn, O

    2014-07-11

    Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ∼30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat+sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves. PMID:25062161

  2. Measurement of the Cosmic Microwave Background Polarization Lensing Power Spectrum with the POLARBEAR Experiment

    NASA Astrophysics Data System (ADS)

    Ade, P. A. R.; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Linder, E.; Leitch, E. M.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Paar, H.; Peloton, J.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Schanning, I.; Schenck, D. E.; Sherwin, B.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.; Polarbear Collaboration

    2014-07-01

    Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ˜30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat +sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves.

  3. A measurement of the cosmic microwave background B-mode polarization power spectrum at sub-degree scales with POLARBEAR

    SciTech Connect

    Ade, P. A. R.; Akiba, Y.; Hasegawa, M.; Anthony, A. E.; Halverson, N. W.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Elleflot, T.; Feng, C.; Borrill, J.; Errard, J.; Chapman, S.; Chinone, Y.; Flanigan, D.; Dobbs, M.; Gilbert, A.; Fabbian, G.; Collaboration: Polarbear Collaboration; and others

    2014-10-20

    We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < ℓ < 2100 and is based on observations of an effective sky area of 25 deg{sup 2} with 3.'5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A{sub BB} to the measured band powers, A{sub BB}=1.12±0.61(stat){sub −0.12}{sup +0.04}(sys)±0.07(multi), where A{sub BB} = 1 is the fiducial WMAP-9 ΛCDM value. In this expression, 'stat' refers to the statistical uncertainty, 'sys' to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and 'multi' to the calibration uncertainties that have a multiplicative effect on the measured amplitude A{sub BB}.

  4. A Measurement of the Cosmic Microwave Background B-mode Polarization Power Spectrum at Sub-degree Scales with POLARBEAR

    NASA Astrophysics Data System (ADS)

    The Polarbear Collaboration: P. A. R. Ade; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A. H.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Linder, E.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Orlando, A.; Paar, H.; Peloton, J.; Poletti, D.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Schanning, I.; Schenck, D. E.; Sherwin, B. D.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.

    2014-10-01

    We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < l < 2100 and is based on observations of an effective sky area of 25 \\deg ^2 with 3.'5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter ABB to the measured band powers, ABB = 1.12 +/- 0.61 (stat) +0.04-0.12(sys) +/- 0.07 (multi), where ABB = 1 is the fiducial WMAP-9 ΛCDM value. In this expression, "stat" refers to the statistical uncertainty, "sys" to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and "multi" to the calibration uncertainties that have a multiplicative effect on the measured amplitude ABB .

  5. The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectrum at 148 AND 218 GHz from the 2008 Southern Survey

    NASA Technical Reports Server (NTRS)

    Das, Sudeep; Marriage, Tobias A.; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L. Felipe; Battistelli, Elia A.; Bond, J. Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Devlin, Mark J.; Dicker, Simon R.; Doriese, W. Bertrand; Dunkley, Joanna; Duenner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P.; Fowler, Joseph W.; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hernandez-Monteagudo, Carlos; Wollack, Ed

    2010-01-01

    We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results dearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ACDM cosmological model. At l > 3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8(sigma) level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

  6. Multiple Peaks in the Angular Power Spectrum of the CosmicMicrowave Background: Significance and Consequences for Cosmology

    SciTech Connect

    de Bernardis, P.; Ade, P.A.R.; Bock, J.J.; Bond, J.R.; Borrill,J.; Boscaleri, A.; Coble, K.; Contaldi, C.R.; Crill, B.P.; De Troia, G.; Farese, P.; Ganga, K.; Giacometti, M.; Hivon, E.; Hristov, V.V.; Iacoangeli, A.; Jaffe, A.H.; Jones, W.C.; Lange, A.E.; Martinis, L.; Masi, S.; Mason, P.; Mauskopf, P.D.; Melchiorri, A.; Montroy, T.; Netterfield, C.B.; Pascale, E.; Piacentini, F.; Pogosyan, D.; Polenta,G.; Pongetti, F.; Prunet, S.; Romeo, G.; Ruhl, J.E.; Scaramuzzi, F.

    2001-05-17

    Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at {ell} {approx} 210, 540, 840 and {ell} {approx} 420, 750, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: {Omega}{sub tot} = 1.02{sub -0.05}{sup +0.06} vs. 1.04 {+-} 0.05, {Omega}{sub b}h{sup 2} = 0.022{sub -0.003}{sup +0.004} vs. 0.019{sub -0.004}{sup +0.005}, and n{sub s} = 0.96{sub -0.09}{sup +0.10} vs. 0.90 {+-} 0.08. The deviation in primordial spectral index n{sub s} is a consequence of the strong correlation with the optical depth.

  7. Constraints on Cosmology from the Cosmic Microwave Background Power Spectrum of the 2500 deg2 SPT-SZ Survey

    NASA Astrophysics Data System (ADS)

    Hou, Z.; Reichardt, C. L.; Story, K. T.; Follin, B.; Keisler, R.; Aird, K. A.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H.-M.; Crawford, T. M.; Crites, A. T.; de Haan, T.; de Putter, R.; Dobbs, M. A.; Dodelson, S.; Dudley, J.; George, E. M.; Halverson, N. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hrubes, J. D.; Joy, M.; Knox, L.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Millea, M.; Mohr, J. J.; Montroy, T. E.; Padin, S.; Plagge, T.; Pryke, C.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Spieler, H. G.; Staniszewski, Z.; Stark, A. A.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.; Zahn, O.

    2014-02-01

    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 (SPT_{CL}) 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 +SPT_{CL}. 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

  8. The Atacama Cosmology Telescope: A Measurement of the 600 less than l less than 8000 Cosmic Microwave Background Power Spectrum at 148 GHz

    NASA Technical Reports Server (NTRS)

    Fowler, J. W.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Bassistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Doriese, W. B.; Dunkley, J.; Duenner, R.; Essinger-Hileman, T.; Fisher, R. P.; Hajian, A.; Halpern, M.; Hasselfield, M.; Moseley, H.; Wollack, Ed

    2010-01-01

    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.4' angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg(sup 2) of the southern sky, in a 4 deg. 2-wide strip centered on declination 53 deg. South. The CMB at arc minute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy dusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 less than l less than 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 less than l less than 1150. The power beyond the Silk damping tail of the CMB (l approximately 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to sigma 8 = 0.8. We constrain the model's amplitude A(sub sz) less than 1.63 (95% CL). If interpreted as a measurement of as, this implies sigma (sup SZ) (sub 8) less than 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a 6-parameter ACDM model plus point sources and the SZ effect is consistent with these results.

  9. Can the cosmic x ray and gamma ray background be due to reflection of a steep power law spectrum and Compton scattering by relativistic electrons?

    NASA Technical Reports Server (NTRS)

    Zycki, Piotr T.; Zdziarski, Andrzej A.; Svensson, Roland

    1991-01-01

    We reconsider the recent model for the origin in the cosmic X-ray and gamma-ray background by Rogers and Field. The background in the model is due to an unresolved population of AGNs. An individual AGN spectrum contains three components: a power law with the energy index of alpha = 1.1, an enhanced reflection component, and a component from Compton scattering by relativistic electrons with a low energy cutoff at some minimum Lorentz factor, gamma(sub min) much greater than 1. The MeV bump seen in the gamma-ray background is then explained by inverse Compton emission by the electrons. We show that the model does not reproduce the shape of the observed X-ray and gamma-ray background below 10 MeV and that it overproduces the background at larger energies. Furthermore, we find the assumptions made for the Compton component to be physically inconsistent. Relaxing the inconsistent assumptions leads to model spectra even more different from that of the observed cosmic background. Thus, we can reject the hypothesis that the high-energy cosmic background is due to the described model.

  10. Primordial power spectrum from Planck

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2014-11-01

    Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near l ~ 750-850 represents the most prominent feature in the data. Feature near l ~ 1800-2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ~ 2.5%. In this context low-l and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

  11. Primordial power spectrum from Planck

    SciTech Connect

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun E-mail: arman@apctp.org

    2014-11-01

    Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near ℓ ∼ 750–850 represents the most prominent feature in the data. Feature near ℓ ∼ 1800–2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ∼ 2.5%. In this context low-ℓ and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

  12. Spectrum of the microwave background radiation

    SciTech Connect

    Richards, P.L.

    1982-04-01

    A review is given of the present status of measurements of the spectrum of the microwave background. Factors which limit experimental accuracy are discussed with particular reference to high frequency measurements. A selection of the available measurements yields a data set which is reasonably consistent with the blackbody spectrum for a temperature of 2.9 K. A simple statistical analysis suggests either that there are errors in the data set, or that deviations from a blackbody spectrum exist. The difficulties inherent in property averaging the results from different observers are described. Prospects for improved measurements will be summarized.

  13. Spectrum of the microwave background radiation

    NASA Technical Reports Server (NTRS)

    Richards, P. L.

    1982-01-01

    A review is given of the present status of measurements of the spectrum of the microwave background. Factors that limit experimental accuracy are discussed with particular reference to high-frequency measurements. A selection of the available measurements yields a data set that is reasonably consistent with the black-body spectrum for a temperature of 2.9 K. A simple statistical analysis suggests either that there are errors in the data set, or that deviations from a black-body spectrum exist. The difficulties inherent in properly averaging the results from different observers are described. Prospects for improved measurements are summarized.

  14. Power Spectrum Estimation. I. Basics

    NASA Astrophysics Data System (ADS)

    Hamilton, A. J. S.

    This chapter and its companion form an extended version of notes provided to participants in the Valencia September 2004 summer school on Data Analysis in Cosmology. The lectures offer a pedagogical introduction to the problem of estimating the power spectrum from galaxy surveys. The intention is to focus on concepts rather than on technical detail, but enough mathematics is provided to point the student in the right direction. This first lecture presents background material. It collects some essential definitions, discusses traditional methods for measuring power, notably the Feldman-Kaiser-Peacock [2] method, and introduces Bayesian analysis, Fisher matrices, and maximum likelihood. For pedagogy and brevity, several derivations are set as exercises for the reader. At the summer school, multiple choice questions, included herein, were used to convey some didactic ideas, and provoked a little lively debate.

  15. Constraints on the power spectrum of the primordial density field from large-scale data - Microwave background and predictions of inflation

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.

    1992-01-01

    It is shown here that, by using galaxy catalog correlation data as input, measurements of microwave background radiation (MBR) anisotropies should soon be able to test two of the inflationary scenario's most basic predictions: (1) that the primordial density fluctuations produced were scale-invariant and (2) that the universe is flat. They should also be able to detect anisotropies of large-scale structure formed by gravitational evolution of density fluctuations present at the last scattering epoch. Computations of MBR anisotropies corresponding to the minimum of the large-scale variance of the MBR anisotropy are presented which favor an open universe with P(k) significantly different from the Harrison-Zeldovich spectrum predicted by most inflationary models.

  16. Reduced shear power spectrum

    SciTech Connect

    Dodelson, Scott; Shapiro, Charles; White, Martin J.; /UC, Berkeley, Astron. Dept. /UC, Berkeley

    2005-08-01

    Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.

  17. Constraints on cosmology from the cosmic microwave background power spectrum of the 2500 deg{sup 2} SPT-SZ survey

    SciTech Connect

    Hou, Z.; Follin, B.; Reichardt, C. L.; George, E. M.; Story, K. T.; Keisler, R.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Dodelson, S.; Aird, K. A.; Cho, H.-M.; De Haan, T.; Dobbs, M. A.; Dudley, J.; De Putter, R.; Halverson, N. W.; and others

    2014-02-20

    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 {sub 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 (dn{sub s} /dln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Y{sub p} and the effective number of neutrino species N {sub eff}) and one that modifies the large-scale power due to the integrated Sachs-Wolfe effect (the sum of neutrino masses ∑m {sub 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 dn{sub s} /dln k with –0.046 < dn{sub s} /dln k < –0.003 at 95% confidence, which strengthens to a 2.7σ indication of dn{sub s} /dln k < 0 from CMB+BAO+H {sub 0}. Detectable dn{sub s} /dln k ≠ 0 is difficult to explain in the context of single-field, slow-roll inflation models. We find N {sub eff} = 3.62 ± 0.48 for the CMB, which tightens to N {sub eff} = 3.71 ± 0.35 from CMB+BAO+H {sub 0}. Larger values of N {sub eff} relieve the mild tension between CMB, BAO, and H {sub 0}. When the Sunyaev-Zel'dovich selected galaxy cluster abundances (SPT{sub CL}) data are also included, we obtain N {sub eff} = 3.29 ± 0.31. Allowing for ∑m {sub ν} gives a 3.0σ detection of ∑m {sub ν} > 0 from CMB+BAO+H {sub 0} +SPT{sub CL}. The median value is (0.32 ± 0.11) eV, a factor of six above the lower bound set by neutrino oscillation

  18. Distortions of the cosmic microwave background spectrum by dust

    NASA Technical Reports Server (NTRS)

    Rowan-Robinson, M.; Negroponte, J.; Silk, J.

    1979-01-01

    The effects of dust in the early universe on the spectrum of the cosmic microwave background are considered, taking into account the effects of a pregalactic generation of stars. It is shown that observed distortions of the background spectrum from that of a black body at 3 K could be due to emission by silicate dust grains at a metal abundance of 0.00001 by mass and with a substantial energy input, which represent the remnants of population III stars. Attempts to fit the microwave background spectrum to the model of Rees (1978) in which the entire cosmic background is accounted for by grain emission are shown to require an implausible value for the metal abundance at early epochs, and not to agree with the millimeter and submillimeter spectrum observed by Woody and Richards (1979).

  19. Modelling the TSZ power spectrum

    SciTech Connect

    Bhattacharya, Suman; Shaw, Laurie D; Nagai, Daisuke

    2010-01-01

    The structure formation in university is a hierarchical process. As universe evolves, tiny density fluctuations that existed in the early universe grows under gravitational instability to form massive large scale structures. The galaxy clusters are the massive viralized objects that forms by accreting smaller clumps of mass until they collapse under their self-gravity. As such galaxy clusters are the youngest objects in the universe which makes their abundance as a function of mass and redshift, very sensitive to dark energy. Galaxy clusters can be detected by measuring the richness in optical waveband, by measuring the X-ray flux, and in the microwave sky using Sunyaev-Zel'dovich (SZ) effect. The Sunyaev-Zel'dovich (SZ) effect has long been recognized as a powerful tool for detecting clusters and probing the physics of the intra-cluster medium. Ongoing and future experiments like Atacama Cosmology Telescope, the South Pole Telescope and Planck survey are currently surveying the microwave sky to develop large catalogs of galaxy clusters that are uniformly selected by the SZ flux. However one major systematic uncertainties that cluster abundance is prone to is the connection between the cluster mass and the SZ flux. As shown by several simulation studies, the scatter and bias in the SZ flux-mass relation can be a potential source of systematic error to using clusters as a cosmology probe. In this study they take a semi-analytic approach for modeling the intra-cluster medium in order to predict the tSZ power spectrum. The advantage of this approach is, being analytic, one can vary the parameters describing gas physics and cosmology simultaneously. The model can be calibrated against X-ray observations of massive, low-z clusters, and using the SZ power spectrum which is sourced by high-z lower mass galaxy groups. This approach allows us to include the uncertainty in gas physics, as dictated by the current observational uncertainties, while measuring the cosmological

  20. Pregalactic dust and distortions of the cosmic-background spectrum

    NASA Astrophysics Data System (ADS)

    Aiello, S.; Melchiorri, F.; Cecchini, S.; Mandolesi, N.

    1980-04-01

    The paper focuses on a comparison between the cosmic-background spectrum and the emission by a dust cloud of silicate grains. The similarity between the emission from a cloud of silicate grains and the observed cosmic-background spectrum is clearly shown schematically. However, for a quantitative comparison a more detailed computation is required. An expression is written for the observed cosmic-background spectrum in terms of the deceleration parameter, the grain extinction cross section, the number density of grains at the present epoch, and the rate of grain production in the pregalactic epoch /f(z)/. A complete analysis of the problem requires the computation of the optical depth for different values of f(z), for different grain materials, and for various distributions of grain radii. All these computations are reported by Aiello et al. (1979). The paper presents only preliminary results.

  1. The EPIC-MOS Particle-Induced Background Spectrum

    NASA Technical Reports Server (NTRS)

    Kuntz, K. D.; Snowden, S. L.

    2006-01-01

    We have developed a method for constructing a spectrum of the particle-induced instrumental background of the XMM-Newton EPIC MOS detectors that can be used for observations of the diffuse background and extended sources that fill a significant fraction of the instrument field of view. The strength and spectrum of the particle-induced background, that is, the background due to the interaction of particles with the detector and the detector surroundings, is temporally variable as well as spatially variable over individual chips. Our method uses a combination of the filter-wheel-closed data and a database of unexposed-region data to construct a spectrum of the "quiescent" background. We show that, using this method of background subtraction, the differences between independent observations of the same region of "blank sky" are consistent with the statistical uncertainties except when there is clear evidence of solar wind charge exchange emission. We use the blank sky observations to show that contamination by SWCX emission is a strong function of the solar wind proton flux, and that observations through the flanks of the magnetosheath appear to be contaminated only at much higher solar wind fluxes. We have also developed a spectral model of the residual soft proton flares, which allows their effects to be removed to a substantial degree during spectral fitting.

  2. Near-millimeter spectrum of the microwave background

    NASA Technical Reports Server (NTRS)

    Woody, D. P.; Richards, P. L.

    1981-01-01

    A description is given of a method for the measurement of the cosmic microwave background (CMB) spectrum. A helium-cooled, balloon-borne spectrophotometer was used to measure the emission spectrum of the night sky over the frequency range 1.7-40/cm. The apparatus was calibrated using a blackbody source at a variety of temperatures both before and after the flight. It is shown that the spectrum of the CMB peaks at 6/cm and is approximately that of a blackbody out to several times that frequency. The measured flux is also found to be equivalent to that from a blackbody in the temperature range from 2.88 to 3.09 K. The data set resulting from the combination of these measurements with previous observations of the CMB covers three decades in frequency, and is compared with various CMB models.

  3. A preliminary measurement of the cosmic microwave background spectrum by the Cosmic Background Explorer (COBE) satellite

    NASA Technical Reports Server (NTRS)

    Mather, J. C.; Cheng, E. S.; Shafer, R. A.; Bennett, C. L.; Boggess, N. W.; Dwek, E.; Hauser, M. G.; Kelsall, T.; Moseley, S. H., Jr.; Silverberg, R. F.

    1990-01-01

    A preliminary spectrum is presented of the background radiation between 1 and 20/cm from regions near the north Galactic pole, as observed by the FIRAS instrument on the COBE satellite. The spectral resolution is 1/cm. The spectrum is well fitted by a blackbody with a temperature of 2.735 + or - 0.06 K, and the deviation from a blackbody is less than 1 percent of the peak intensity over the range 1-20/cm. These new data show no evidence for the submillimeter excess previously reported by Matsumoto et al. (1988) in the cosmic microwave background. Further analysis and additional data are expected to improve the sensitivity to deviations from a blackbody spectrum by an order of magnitude.

  4. Near-millimeter spectrum of the microwave background

    SciTech Connect

    Woody, D.P.; Richards, P.L.

    1981-08-15

    A complete description is given of a measurement of the spectrum of the cosmic microwave background (CMB). A fully calibrated, liquid helium cooled, ballon borne spectrophotometer was used to measure the emission spectrum of the night sky over the frequency range from 1.7 to 40 cm/sup -1/. Great care was taken with the instrumental design to avoid radiation from the Earth or the apparatus. The apparatus was calibrated using a blackbody source with a variety of temperatures before and after the flight. The atmospheric emission was subtracted by fitting the data to the spectrum computed from an atmospheric model. The resulting spectral measurements have a flux accuracy of better than 10% of the peak flux of a 3 K blackbody and extend over the frequency range from 2.5 to 24 cm/sup -1/. They show that the spectrum of the CMB peaks at 6 cm/sup -1/ and is approximately that of a blackbody out to several times that frequency. Some deviations from blackbody shape are observed. The measured flux is equivalent to that from a blackbody in the temperature range from 2.88 to 3.09 K. These measurements are combined with previous observations of the CMB to produce a set of data covering three decades in frequency. This data set is compared with various models of the CMB.

  5. Feature selection using Haar wavelet power spectrum

    PubMed Central

    Subramani, Prabakaran; Sahu, Rajendra; Verma, Shekhar

    2006-01-01

    Background Feature selection is an approach to overcome the 'curse of dimensionality' in complex researches like disease classification using microarrays. Statistical methods are utilized more in this domain. Most of them do not fit for a wide range of datasets. The transform oriented signal processing domains are not probed much when other fields like image and video processing utilize them well. Wavelets, one of such techniques, have the potential to be utilized in feature selection method. The aim of this paper is to assess the capability of Haar wavelet power spectrum in the problem of clustering and gene selection based on expression data in the context of disease classification and to propose a method based on Haar wavelet power spectrum. Results Haar wavelet power spectra of genes were analysed and it was observed to be different in different diagnostic categories. This difference in trend and magnitude of the spectrum may be utilized in gene selection. Most of the genes selected by earlier complex methods were selected by the very simple present method. Each earlier works proved only few genes are quite enough to approach the classification problem [1]. Hence the present method may be tried in conjunction with other classification methods. The technique was applied without removing the noise in data to validate the robustness of the method against the noise or outliers in the data. No special softwares or complex implementation is needed. The qualities of the genes selected by the present method were analysed through their gene expression data. Most of them were observed to be related to solve the classification issue since they were dominant in the diagnostic category of the dataset for which they were selected as features. Conclusion In the present paper, the problem of feature selection of microarray gene expression data was considered. We analyzed the wavelet power spectrum of genes and proposed a clustering and feature selection method useful for

  6. Precise measurements of primordial power spectrum with 21 cm fluctuations

    SciTech Connect

    Kohri, Kazunori; Oyama, Yoshihiko; Sekiguchi, Toyokazu; Takahashi, Tomo E-mail: oyamayo@post.kek.jp E-mail: tomot@cc.saga-u.ac.jp

    2013-10-01

    We discuss the issue of how precisely we can measure the primordial power spectrum by using future observations of 21 cm fluctuations and cosmic microwave background (CMB). For this purpose, we investigate projected constraints on the quantities characterizing primordial power spectrum: the spectral index n{sub s}, its running α{sub s} and even its higher order running β{sub s}. We show that future 21 cm observations in combinations with CMB would accurately measure above mentioned observables of primordial power spectrum. We also discuss its implications to some explicit inflationary models.

  7. Ultraviolet spectrum of the sky background at different galactic latitudes

    NASA Astrophysics Data System (ADS)

    Zvereva, A. M.; Severnyi, A. B.; Granitskii, L. V.; Hua, C. T.; Cruvellier, P.; Courtes, G.

    1982-12-01

    The intensity distributions of the sky background radiation in the 1100-1850 A range were measured in deep space (70,000-200,000 km from the earth) by the Prognoz-6 photoelectric spectrometer. Spectral distributions of UV background Ilambda, after subtraction of the stellar component, vary with galactic latitude in the range bII equals minus 58 to plus 27 deg. Ilambda decreases with increasing wavelength at high latitudes; the spectrum then becomes flat at intermediate latitudes, and there is a rapid decrease of Ilambda with lambda near and inside the Milky Way. The intensity I(lambda equals 1600) in the higher latitude range (the absolute value of bII higher than 30 deg) shows good correlation with soft X-ray brightness and neutral hydrogen (21-cm) density N(H I). However, there is appreciable UV emission near the galactic poles where N(H I) is approximately zero

  8. Reconstruction of the primordial power spectrum from CMB data

    SciTech Connect

    Guo, Zong-Kuan; Zhang, Yuan-Zhong; Schwarz, Dominik J. E-mail: dschwarz@physik.uni-bielefeld.de

    2011-08-01

    Measuring the deviation from scale invariance of the primordial power spectrum is a critical test of inflation. In this paper we reconstruct the shape of the primordial power spectrum of curvature perturbations from the cosmic microwave background data, including the 7-year Wilkinson Microwave Anisotropy Probe data and the Atacama Cosmology Telescope 148 GHz data, by using a binning method of a cubic spline interpolation in log-log space. We find that the power-law spectrum is preferred by the data and that the Harrison-Zel'dovich spectrum is disfavored at 95% confidence level. These conclusions hold with and without allowing for tensor modes, however the simpler model without tensors is preferred by the data. We do not find evidence for a feature in the primordial power spectrum — in full agreement with generic predictions from cosmological inflation.

  9. Hierarchical cosmic shear power spectrum inference

    NASA Astrophysics Data System (ADS)

    Alsing, Justin; Heavens, Alan; Jaffe, Andrew H.; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till

    2016-02-01

    We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models a posteriori without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear E-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes.

  10. Log-transforming the matter power spectrum

    NASA Astrophysics Data System (ADS)

    Greiner, M.; Enßlin, T. A.

    2015-02-01

    We investigate whether non-linear effects on the large-scale power spectrum of dark matter, namely the increase in small-scale power and the smearing of baryon acoustic oscillations, can be decreased by a log-transformation or emulated by an exponential transformation of the linear spectrum. To that end we present a formalism to convert the power spectrum of a log-normal field to the power spectrum of the logarithmic Gaussian field and vice versa. All ingredients of our derivation can already be found in various publications in cosmology and other fields. We follow a more pedagogical approach providing a detailed derivation, application examples, and a discussion of implementation subtleties in one text. We use the formalism to show that the non-linear increase in small-scale power in the matter power spectrum is significantly smaller for the log-transformed spectrum which fits the linear spectrum (with less than 20% error) for redshifts down to 1 and k ≤ 1.0 h Mpc. For lower redshifts the fit to the linear spectrum is not as good, but the reduction of non-linear effects is still significant. Similarly, we show that applying the linear growth factor to the logarithmic density leads to an automatic increase in small-scale power for low redshifts fitting to third-order perturbation spectra and Cosmic Emulator spectra with an error of less than 20%. Smearing of baryon acoustic oscillations is at least three times weaker, but still present.

  11. The microlocal spectrum condition, initial value formulations, and background independence

    NASA Astrophysics Data System (ADS)

    Stottmeister, Alexander; Thiemann, Thomas

    2016-02-01

    We analyze implications of the microlocal spectrum/Hadamard condition for states in a (linear) quantum field theory on a globally hyperbolic spacetime M in the context of a (distributional) initial value formulation. More specifically, we work in 3+1-split M ≅ ℝ × Σ and give a bound, independent of the spacetime metric, on the wave front sets of the initial data for a quasi-free Hadamard state in a quantum field theory defined by a normally hyperbolic differential operator P acting in a vector bundle E → π M . This aims at a possible way to apply the concept of Hadamard states within approaches to quantum field theory/gravity relying on a Hamiltonian formulation, potentially without a (classical) background metric g.

  12. Another look at distortions of the Cosmic Microwave Background spectrum

    NASA Astrophysics Data System (ADS)

    De Zotti, G.; Negrello, M.; Castex, G.; Lapi, A.; Bonato, M.

    2016-03-01

    We review aspects of Cosmic Microwave Background (CMB) spectral distortions which do not appear to have been fully explored in the literature. In particular, implications of recent evidences of heating of the intergalactic medium (IGM) by feedback from active galactic nuclei are investigated. Taking also into account the IGM heating associated to structure formation, we argue that values of the y parameter of several × 10-6, i.e. a factor of a few below the COBE/FIRAS upper limit, are to be expected. The Compton scattering by the re-ionized plasma also re-processes primordial distortions, adding a y-type contribution. Hence no pure Bose-Einstein-like distortions are to be expected. An assessment of Galactic and extragalactic foregrounds, taking into account the latest results from the Planck satellite as well as the contributions from the strong CII and CO lines from star-forming galaxies, demonstrates that a foreground subtraction accurate enough to fully exploit the PIXIE sensitivity will be extremely challenging. Motivated by this fact we also discuss methods to detect spectral distortions not requiring absolute measurements and show that accurate determinations of the frequency spectrum of the CMB dipole amplitude may substantially improve over COBE/FIRAS limits on distortion parameters. Such improvements may be at reach of next generation CMB anisotropy experiments. The estimated amplitude of the Cosmic Infrared Background (CIB) dipole might be detectable by careful analyses of Planck maps at the highest frequencies. Thus Planck might provide interesting constraints on the CIB intensity, currently known with a simeq 30% uncertainty.

  13. Towards optimal cluster power spectrum analysis

    NASA Astrophysics Data System (ADS)

    Smith, Robert E.; Marian, Laura

    2016-04-01

    The power spectrum of galaxy clusters is an important probe of the cosmological model. In this paper, we develop a formalism to compute the optimal weights for the estimation of the matter power spectrum from cluster power spectrum measurements. We find a closed-form analytic expression for the optimal weights, which takes into account: the cluster mass, finite survey volume effects, survey masking, and a flux limit. The optimal weights are w(M,χ ) ∝ b(M,χ )/[1+bar{n}_h(χ ) overline{b^2}(χ )overline{P}(k)], where b(M, χ) is the bias of clusters of mass M at radial position χ(z), bar{n}_h(χ ) and overline{b^2}(χ ) are the expected space density and bias squared of all clusters, and overline{P}(k) is the matter power spectrum at wavenumber k. This result is analogous to that of Percival et al. We compare our optimal weighting scheme with mass weighting and also with the original power spectrum scheme of Feldman et al. We show that our optimal weighting scheme outperforms these approaches for both volume- and flux-limited cluster surveys. Finally, we present a new expression for the Fisher information matrix for cluster power spectrum analysis. Our expression shows that for an optimally weighted cluster survey the cosmological information content is boosted, relative to the standard approach of Tegmark.

  14. Probing the primordial power spectrum with cluster number counts

    SciTech Connect

    Chantavat, Teeraparb; Gordon, Christopher; Silk, Joseph

    2009-04-15

    We investigate how well galaxy cluster number counts can constrain the primordial power spectrum. Measurements of the primary anisotropies in the cosmic microwave background may be limited, by the presence of foregrounds from secondary sources, to probing the primordial power spectrum at wave numbers less than about 0.30h Mpc{sup -1}. We break up the primordial power spectrum into a number of nodes and interpolate linearly between each node. This allows us to show that cluster number counts could then extend the constraints on the form of the primordial power spectrum up to wave numbers of about 0.45h Mpc{sup -1}. We estimate combinations of constraints from PLANCK and SPT primary cosmic microwave background and their respective Sunyaev-Zeldovich surveys. We find that their constraining ability is limited by uncertainties in the mass-scaling relations. We also estimate the constraint from clusters detected from a SNAP-like gravitational lensing survey. As there is an unambiguous and simple relationship between the filtered shear of the lensing survey and the cluster mass, it may be possible to obtain much tighter constraints on the primordial power spectrum in this case.

  15. Primordial power spectrum features and fNL constraints

    NASA Astrophysics Data System (ADS)

    Gariazzo, Stefano; Lopez-Honorez, Laura; Mena, Olga

    2015-09-01

    The simplest models of inflation predict small non-Gaussianities and a featureless power spectrum. However, there exist a large number of well-motivated theoretical scenarios in which large non-Gaussianties could be generated. In general, in these scenarios the primordial power spectrum will deviate from its standard power law shape. We study, in a model-independent manner, the constraints from future large-scale structure surveys on the local non-Gaussianity parameter fNL when the standard power law assumption for the primordial power spectrum is relaxed. If the analyses are restricted to the large-scale-dependent bias induced in the linear matter power spectrum by non-Gaussianites, the errors on the fNL parameter could be increased by 60% when exploiting data from the future DESI survey, if dealing with only one possible dark matter tracer. In the same context, a nontrivial bias |δ fNL|˜2.5 could be induced if future data are fitted to the wrong primordial power spectrum. Combining all the possible DESI objects slightly ameliorates the problem, as the forecasted errors on fNL would be degraded by 40% when relaxing the assumptions concerning the primordial power spectrum shape. Also, the shift on the non-Gaussianity parameter is reduced in this case, |δ fNL|˜1.6 . The addition of cosmic microwave background priors ensures robust future fNL bounds, as the forecasted errors obtained including these measurements are almost independent on the primordial power spectrum features, and |δ fNL|˜0.2 , close to the standard single-field slow-roll paradigm prediction.

  16. A measurement of the low frequency spectrum of the cosmic microwave background radiation

    SciTech Connect

    Levin, S.M.

    1987-04-01

    As part of a larger effort to measure the spectrum of the Cosmic Background Radiation (CBR) at low frequencies, the intensity of the CBR has been measured at a frequency of 1.410 GHz. The measurement was made by comparing the power received from the sky with the power received from a specially designed cooled calibration target with known properties. Sources of radiation other than the CBR were then identified and subtracted to calculate the antenna temperature of the CBR at 1.410 GHz. The instrument used to measure the CBR was a total-power microwave radiometer with a 25 MHz bandwidth centered at 1.410 GHz. The radiometer had a noise temperature of 80 K, and sufficient data were taken that radiometer noise did not contribute significantly to the total measurement error. The sources of error were predominantly systematic in nature, and the largest error was due to uncertainty in the reflection characteristics of the cold-load calibrator. Identification and subtraction of signals from the Galaxy (0.7 K) and the Earth's atmosphere (0.8 K) were also significant parts of the data reduction and error analysis. The brightness temperature of the Cosmic Background Radiation at 1.410 GHz is 222. +- 0.55 Kelvin. The spectrum of the CBR, as determined by this measurement and other published results, is consistent with a blackbody spectrum of temperature 2.741 +- 0.016. Constraints on the amount by which the CBR spectrum deviates from Planck spectrum are used to place limits on energy releases early in the history of the universe. 55 refs., 25 figs., 8 tabs.

  17. The Spectrum of the Cosmic X-ray Background Observed by RTXE/PCA

    NASA Technical Reports Server (NTRS)

    Revnivtsev, M.; Gilfanov, M.; Sunyaev, R.; Jahoda, K.; Markwardt, C.

    2004-01-01

    We have analyzed a large set of Rossi X-ray Timing Explorer/Proportional Counter Array (RXTE/PCA) scanning and slewing observations performed between April 1996 and March 1999. We obtained the 3-20 keV spectrum of the cosmic X-ray background (CXB) by subtracting Earth-occulted observations from observations of the X-ray sky at high galactic latitude and far away from sources. The sky coverage is approximately 22.6 x 10(exp 3) square degrees. The PCA spectrum of CXB in 3-20 keV energy band is adequately approximated by a single power law with photon index GAMMA approximately 1.4 and normalization at 1 keV approximately 9.5 phot/s/square centimeter/keV/sr. Instrumental background uncertainty precludes accurate RXTE/PCA measurements of the spectrum of cosmic X-ray background at energies above 15 keV and therefore we cannot detect the high energy cutoff observed by the High Energy Astronomical Observatory (HEAO)-1 A2 experiment. Deep observations of the 6 high latitude points used to model the PCA background provide a coarse measure of the spatial variation of the CXB. The CXB variations are consistent with a fixed spectral shape and variable normalization characterized by a fractional rms amplitude of approximately 7% on angular scales of approximately 1 square deg.

  18. Background neutron spectrum at 2420 m above sea level

    NASA Astrophysics Data System (ADS)

    Vega-Carrillo, Hector Rene; Manzanares-Acuña, Eduardo

    2004-05-01

    The ambient neutron spectrum was measured in-doors at ground level in Zacatecas Mexico at 2420 m above sea level. A Bonner sphere spectrometer with a 6LiI(Eu) scintillator was used to obtain the neutron spectrum. With the spectrum the ambient dose equivalent was calculated using the ICRP 74 neutron fluence-to-dose conversion factors. The neutron fluence rate was 65±3 cm -2 h -1, producing 13.7±0.6 nSv h -1 due to ambient dose equivalent.

  19. LIKELIHOOD OF THE POWER SPECTRUM IN COSMOLOGICAL PARAMETER ESTIMATION

    SciTech Connect

    Sun, Lei; Wang, Qiao; Zhan, Hu

    2013-11-01

    The likelihood function is a crucial element of parameter estimation. In analyses of galaxy overdensities and weak lensing shear, one often approximates the likelihood of the power spectrum with a Gaussian distribution. The posterior probability derived from such a likelihood deviates considerably from the exact posterior on the largest scales probed by any survey, where the central limit theorem does not apply. We show that various forms of Gaussian likelihoods can have a significant impact on the estimation of the primordial non-Gaussianity parameter f{sub NL} from the galaxy angular power spectrum. The Gaussian plus log-normal likelihood, which has been applied successfully in analyses of the cosmic microwave background, outperforms the Gaussian likelihoods. Nevertheless, even if the exact likelihood of the power spectrum is used, the estimated parameters may be still biased. As such, the likelihoods and estimators need to be thoroughly examined for potential systematic errors.

  20. Deconstructing the Spectrum of the Soft X-ray Background

    NASA Technical Reports Server (NTRS)

    Kuntz, K. D.; Snowden, S. L.

    2000-01-01

    The soft X-ray background in the 0.1-1.0 keV band is known to be produced by at least three sources; the Local Hot Bubble (LHB), the extragalactic power law (EPL), and a seemingly galactic component that lies outside the bulk of the absorption that is due to the ISM of the galactic disk. This last component, which we call the Trans-Absorption Emission (TAE), has been modeled by a number of groups who have derived disparate measures of its temperature. The differences have arisen from differing assumptions about the structure of the emitting gas and unrecognized methodological difficulties. In particular, spectral fitting methods do not uniquely separate the TAE from the foreground emission that is due the LHB. This "degeneracy" can be resolved using the angular variation of the absorption of the TAE. We show that the TAE cannot be characterized by a single thermal component; no single-component model can be consistent with both the spectral energy distribution of the TAE emission and the angular variation due to absorption by the galactic disk. We use the angular anticorrelation of the ROSAT All-Sky Survey with the galactic absorption to separate local from distant emission components, and to fit the spectral energy distribution of the resulting distant emission. We find that the emission is best described by a two-thermal-component model with logT(sub S) = 6.06(sup +0.14, sub -0.12) and log T(sub H) = 6.42(sup +0.14, sub -0.12). This two-thermal-component TAE fits the ROSAT spectral energy distribution significantly better than single-component models, and is consistent with both angular variation and spectral constraints.

  1. computePk: Power spectrum computation

    NASA Astrophysics Data System (ADS)

    L'Huillier, Benjamin

    2014-03-01

    ComputePk computes the power spectrum in cosmological simulations. It is MPI parallel and has been tested up to a 4096^3 mesh. It uses the FFTW library. It can read Gadget-3 and GOTPM outputs, and computes the dark matter component. The user may choose between NGP, CIC, and TSC for the mass assignment scheme.

  2. Generalized slow roll approximation for large power spectrum features

    SciTech Connect

    Dvorkin, Cora; Hu, Wayne

    2010-01-15

    We develop a variant of the generalized slow roll approach for calculating the curvature power spectrum that is well suited for order unity deviations in power caused by sharp features in the inflaton potential. As an example, we show that predictions for a step function potential, which has been proposed to explain order unity glitches in the cosmic microwave background temperature power spectrum at multipoles l=20-40, are accurate at the percent level. Our analysis shows that to good approximation there is a single source function that is responsible for observable features and that this function is simply related to the local slope and curvature of the inflaton potential. These properties should make the generalized slow roll approximation useful for inflation-model-independent studies of features, both large and small, in the observable power spectra.

  3. Enhancing the cosmic shear power spectrum

    NASA Astrophysics Data System (ADS)

    Simpson, Fergus; Harnois-Déraps, Joachim; Heymans, Catherine; Jimenez, Raul; Joachimi, Benjamin; Verde, Licia

    2016-02-01

    Applying a transformation to a non-Gaussian field can enhance the information content of the resulting power spectrum, by reducing the correlations between Fourier modes. In the context of weak gravitational lensing, it has been shown that this gain in information content is significantly compromised by the presence of shape noise. We apply clipping to mock convergence fields, a technique which is known to be robust in the presence of noise and has been successfully applied to galaxy number density fields. When analysed in isolation the resulting convergence power spectrum returns degraded constraints on cosmological parameters. However, substantial gains can be achieved by performing a combined analysis of the power spectra derived from both the original and transformed fields. Even in the presence of realistic levels of shape noise, we demonstrate that this approach is capable of reducing the area of likelihood contours within the Ωm - σ8 plane by more than a factor of 3.

  4. Gabor transforms on the sphere with applications to CMB power spectrum estimation

    NASA Astrophysics Data System (ADS)

    Hansen, Frode K.; Górski, Krzysztof M.; Hivon, Eric

    2002-11-01

    The Fourier transform of a data set apodized with a window function is known as the Gabor transform. In this paper we extend the Gabor transform formalism to the sphere with the intention of applying it to cosmic microwave background (CMB) data analysis. The Gabor coefficients on the sphere known as the pseudo power spectrum is studied for windows of different size. By assuming that the pseudo power spectrum coefficients are Gaussian distributed, we formulate a likelihood ansatz using these as input parameters to estimate the full-sky power spectrum from a patch on the sky. As this likelihood can be calculated quickly without having to invert huge matrices, this allows for fast power spectrum estimation. By using the pseudo power spectrum from several patches on the sky together, the full-sky power spectrum can be estimated from full-sky or nearly full-sky observations.

  5. COPSS: The CO Power Spectrum Survey

    NASA Astrophysics Data System (ADS)

    Keating, Garrett K.; Bower, Geoffrey C.; Marrone, Daniel P.; Heiles, Carl E.; SZA, CARMA, COPSS

    2016-01-01

    Molecular gas is a vital component of galactic evolution and star formation, but its abundance in normal star-forming galaxies in the early Universe is poorly understood. Direct detection methods have been able to probe only the most luminous of galaxies at z˜3, missing the vast population of Milky Way progenitors and "building block" galaxies that are expected to bear the bulk of the molecular gas of the early Universe. Using the technique of "intensity mapping", where measurements of different 3D Fourier modes are used to construct a power spectrum, these smaller galaxies can be detectable as an integrated ensemble.We present results from the CO Power Spectrum Survey (COPSS), an intensity mapping experiment performed with the Sunyaev-Zel'dovich Array (SZA). The SZA, a 3.5m × 8-element subset of the Combined Array for Research in Millimeter-wave Astronomy, is capable of observing CO (J=1→0) at z=2.3-3.3. We present final results from of the first phase of this project, utilizing an archival dataset (covering 44 fields in 1400 hours observing time). With these data, we constrain the CO power spectrum to PCO < 2.6×104 μK2 (Mpc/h)3 at z˜3, excluding the model of Lidz et al. (2011) and putting significant constraints on one of two models from Pullen et al. (2013) at this redshift. With this limit, we are able to constrain the cosmic molecular gas density to ρH2(z˜3) < 2.8×108 M⊙ Mpc-3. We also present current results from the second phase of this project, a 5000-hour observing campaign with the SZA, which increases our sensitivity by more than an order of magnitude.

  6. FLUKA: Predictive power for cosmogenic backgrounds

    SciTech Connect

    Empl, A. Hungerford, E. V.; Ferrari, A.; Smirnov, G. I.

    2015-08-17

    The next generation of experiments searching for rare physics events with increased sensitivity will require precise predictions of cosmogenic backgrounds. Recent high quality deep underground measurements for cosmogenic neutrons in large liquid scintillator targets were used to study the FLUKA simulation package for this purpose. The results and conclusions drawn from a detailed benchmark comparison with data from the Borexino experiment were reported recently. In general, good agreement between data and simulation results were found with some identified discrepancies. Improved physics models already implemented in the current version of the FLUKA code, which will be publicly available with the upcoming code release, address the more important identified issues. A careful evaluation of the improved predictions is ongoing. However, the agreement between preliminary FLUKA simulation results and the Borexino experimental data are excellent. The preliminary findings will be discussed.

  7. FLUKA: Predictive power for cosmogenic backgrounds

    NASA Astrophysics Data System (ADS)

    Empl, A.; Ferrari, A.; Hungerford, E. V.; Smirnov, G. I.

    2015-08-01

    The next generation of experiments searching for rare physics events with increased sensitivity will require precise predictions of cosmogenic backgrounds. Recent high quality deep underground measurements for cosmogenic neutrons in large liquid scintillator targets were used to study the FLUKA simulation package for this purpose. The results and conclusions drawn from a detailed benchmark comparison with data from the Borexino experiment were reported recently. In general, good agreement between data and simulation results were found with some identified discrepancies. Improved physics models already implemented in the current version of the FLUKA code, which will be publicly available with the upcoming code release, address the more important identified issues. A careful evaluation of the improved predictions is ongoing. However, the agreement between preliminary FLUKA simulation results and the Borexino experimental data are excellent. The preliminary findings will be discussed.

  8. Cosmic string power spectrum, bispectrum, and trispectrum

    SciTech Connect

    Regan, D. M.; Shellard, E. P. S.

    2010-09-15

    We use analytic calculations of the post-recombination gravitational effects of cosmic strings to estimate the resulting CMB power spectrum, bispectrum and trispectrum. We place a particular emphasis on multipole regimes relevant for forthcoming CMB experiments, notably the Planck satellite. These calculations use a flat-sky approximation, generalizing previous work by integrating string contributions from last scattering to the present day, finding the dominant contributions to the correlators for multipoles l>50. We find a well-behaved shape for the string bispectrum (without divergences) which is easily distinguishable from the inflationary bispectra which possess significant acoustic peaks. We estimate that the nonlinearity parameter characterizing the bispectrum is approximately 0 > or approx. f{sub NL} > or approx. -40 (given present string constraints from the CMB power spectrum). We also apply these unequal time correlator methods to calculate the trispectrum for parrallelogram configurations, again valid over a large range of angular scales relevant for WMAP and Planck, as well as on very small angular scales. We find that, unlike the bispectrum which is suppressed by symmetry considerations, the trispectrum for cosmic strings is large. Our current estimate for the trispectrum parameter is {tau}{sub NL{approx}}10{sup 5}, which may provide one of the strongest constraints on the string model in future analysis.

  9. Cosmological parameter estimation with free-form primordial power spectrum

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2013-06-01

    Constraints on the main cosmological parameters using cosmic microwave background (CMB) or large scale structure data are usually based on the power-law assumption of the primordial power spectrum (PPS). However, in the absence of a preferred model for the early Universe, this raises a concern that current cosmological parameter estimates are strongly prejudiced by the assumed power-law form of PPS. In this paper, for the first time, we perform cosmological parameter estimation allowing the free form of the primordial spectrum. This is in fact the most general approach to estimate cosmological parameters without assuming any particular form for the primordial spectrum. We use a direct reconstruction of the PPS for any point in the cosmological parameter space using the recently modified Richardson-Lucy algorithm; however, other alternative reconstruction methods could be used for this purpose as well. We use WMAP 9 year data in our analysis considering the CMB lensing effect, and we report, for the first time, that the flat spatial universe with no cosmological constant is ruled out by more than a 4σ confidence limit without assuming any particular form of the primordial spectrum. This would be probably the most robust indication for dark energy using CMB data alone. Our results on the estimated cosmological parameters show that higher values of the baryonic and matter density and a lower value of the Hubble parameter (in comparison to the estimated values by assuming power-law PPS) is preferred by the data. However, the estimated cosmological parameters by assuming a free form of the PPS have an overlap at 1σ confidence level with the estimated values assuming the power-law form of PPS.

  10. Primordial power spectrum of tensor perturbations in Finsler spacetime

    NASA Astrophysics Data System (ADS)

    Li, Xin; Wang, Sai

    2016-02-01

    We first investigate the gravitational wave in the flat Finsler spacetime. In the Finslerian universe, we derive the perturbed gravitational field equation with tensor perturbations. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. Then we obtain the modified primordial power spectrum of the tensor perturbations. The parity violation feature requires that the anisotropic effect contributes to the TT, TE, EE, BB angular correlation coefficients with l'=l+1 and TB, EB with l'=l. The numerical results show that the anisotropic contributions to the angular correlation coefficients depend on m, and TE and ET angular correlation coefficients are different.

  11. Power spectrum analysis for defect screening in integrated circuit devices

    DOEpatents

    Tangyunyong, Paiboon; Cole Jr., Edward I.; Stein, David J.

    2011-12-01

    A device sample is screened for defects using its power spectrum in response to a dynamic stimulus. The device sample receives a time-varying electrical signal. The power spectrum of the device sample is measured at one of the pins of the device sample. A defect in the device sample can be identified based on results of comparing the power spectrum with one or more power spectra of the device that have a known defect status.

  12. Halo Substructure and the Power Spectrum

    NASA Astrophysics Data System (ADS)

    Zentner, Andrew R.; Bullock, James S.

    2003-11-01

    We present a semianalytic model to investigate the merger history, destruction rate, and survival probability of substructure in hierarchically formed dark matter halos and use it to study the substructure content of halos as a function of input primordial power spectrum. For a standard cold dark matter ``concordance'' cosmology (ΛCDM n=1, σ8=0.95) we successfully reproduce the subhalo velocity function and radial distribution profile seen in N-body simulations and determine that the rate of merging and disruption peaks ~10-12 Gyr in the past for Milky Way-like halos, while surviving substructures are typically accreted within the last ~0-8 Gyr. We explore power spectra with normalizations and spectral ``tilts'' spanning the ranges σ8~=1-0.65 and n~=1-0.8, and include a ``running-index'' model with dn/dlnk=-0.03 similar to the best-fit model discussed in the first-year Wilkinson Microwave Anisotropy Probe (WMAP) report. We investigate spectra with truncated small-scale power, including a broken-scale inflation model and three warm dark matter cases with mW=0.75-3.0 keV. We find that the mass fraction in substructure is relatively insensitive to the tilt and overall normalization of the primordial power spectrum. All of the CDM-type models yield projected substructure mass fractions that are consistent with, but on the low side, of published estimates from strong lens systems: f9=0.4%-1.5% (64th percentile) for subhalos smaller than 109 Msolar within projected cylinders of radius r<10 kpc. Truncated models produce significantly smaller fractions, f9=0.02%-0.2% for mW~=1 keV, and are disfavored by lensing estimates. This suggests that lensing and similar probes can provide a robust test of the CDM paradigm and a powerful constraint on broken-scale inflation/warm particle masses, including masses larger than the ~1 keV upper limits of previous studies. We compare our predicted subhalo velocity functions with the dwarf satellite population of the Milky Way. Assuming

  13. On minimally parametric primordial power spectrum reconstruction and the evidence for a red tilt

    SciTech Connect

    Verde, Licia; Peiris, Hiranya E-mail: lverde@astro.princeton.edu

    2008-07-15

    The latest cosmological data seem to indicate a significant deviation from scale invariance of the primordial power spectrum when parameterized either by a power law or by a spectral index with non-zero 'running'. This deviation, by itself, serves as a powerful tool for discriminating among theories for the origin of cosmological structures such as inflationary models. Here, we use a minimally parametric smoothing spline technique to reconstruct the shape of the primordial power spectrum. This technique is well suited to searching for smooth features in the primordial power spectrum such as deviations from scale invariance or a running spectral index, although it would recover sharp features of high statistical significance. We use the WMAP three-year results in combination with data from a suite of higher resolution cosmic microwave background experiments (including the latest ACBAR 2008 release), as well as large-scale structure data from SDSS and 2dFGRS. We employ cross-validation to assess, using the data themselves, the optimal amount of smoothness in the primordial power spectrum consistent with the data. This minimally parametric reconstruction supports the evidence for a power law primordial power spectrum with a red tilt, but not for deviations from a power law power spectrum. Smooth variations in the primordial power spectrum are not significantly degenerate with the other cosmological parameters.

  14. Power spectrum of the fluctuation of Chebyshev's prime counting function

    NASA Astrophysics Data System (ADS)

    Lan, Boon Leong; Yong, Shaohen

    2006-02-01

    The one-sided power spectrum of the fluctuation of Chebyshev's weighted prime counting function is numerically estimated based on samples of the fluctuating function of different sizes. The power spectrum is also estimated analytically for large frequency based on Riemann hypothesis and the exact formula for the fluctuating function in terms of all the non-trivial Riemann zeroes. Our analytical estimate is consistent with our numerical estimate of a 1/f2 power spectrum.

  15. Review of Cosmic Background Radiation Spectrum Measurements:Limits on Distortions, Energy Release, and Cosmological Processes

    SciTech Connect

    Smoot, G.F.

    1986-01-01

    This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 {+-} 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.

  16. Review of cosmic background radiation spectrum measurements: limits on distortions, energy release, and cosmological processes

    SciTech Connect

    Smoot, G.F.

    1986-01-01

    This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 +- 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.

  17. Just enough inflation: power spectrum modifications at large scales

    SciTech Connect

    Cicoli, Michele; Downes, Sean; Dutta, Bhaskar; Pedro, Francisco G.; Westphal, Alexander E-mail: ssdownes@phys.ntu.edu.tw E-mail: francisco.pedro@desy.de

    2014-12-01

    We show that models of 'just enough' inflation, where the slow-roll evolution lasted only 50- 60 e-foldings, feature modifications of the CMB power spectrum at large angular scales. We perform a systematic analytic analysis in the limit of a sudden transition between any possible non-slow-roll background evolution and the final stage of slow-roll inflation. We find a high degree of universality since most common backgrounds like fast-roll evolution, matter or radiation-dominance give rise to a power loss at large angular scales and a peak together with an oscillatory behaviour at scales around the value of the Hubble parameter at the beginning of slow-roll inflation. Depending on the value of the equation of state parameter, different pre-inflationary epochs lead instead to an enhancement of power at low ℓ, and so seem disfavoured by recent observational hints for a lack of CMB power at ℓ∼< 40. We also comment on the importance of initial conditions and the possibility to have multiple pre-inflationary stages.

  18. THE ATACAMA COSMOLOGY TELESCOPE: A MEASUREMENT OF THE PRIMORDIAL POWER SPECTRUM

    SciTech Connect

    Hlozek, Renee; Dunkley, Joanna; Addison, Graeme; Appel, John William; Das, Sudeep; Essinger-Hileman, Thomas; Fowler, Joseph W.; Hajian, Amir; Hincks, Adam D.; Bond, J. Richard; Carvalho, C. Sofia; Devlin, Mark J.; Klein, Jeff; Duenner, Rolando; Gallardo, Patricio; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hughes, John P.; Irwin, Kent D.; and others

    2012-04-10

    We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT) in combination with measurements from the Wilkinson Microwave Anisotropy Probe and a prior on the Hubble constant. The angular resolution of ACT provides sensitivity to scales beyond l = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k {approx_equal} 0.2 Mpc{sup -1}. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from cosmic microwave background measurements (which probe the power spectrum in the linear regime) with existing probes of galaxy clustering, cluster abundances, and weak-lensing constraints on the primordial power. This highlights the range of scales probed by current measurements of the matter power spectrum.

  19. Low-Frequency Measurments of the Cosmic Background RadiationSpectrum

    SciTech Connect

    Smoot, G.F.; De Amici, G.; Friedman, S.D.; Witebsky, C.; Sironi,G.; Bonelli, G.; Mandolesi, N.; Cortiglioni, S.; Morigi, G.; Partridge,R.B.; Danese, L.; De Zotti, G.

    1984-11-01

    The long-wavelength spectrum of the cosmic background radiation has been measured at five wavelengths (0.33, 0.9, 3.0, 6.3, and 12.0 cm). These measurements represent a continuation of the work reported by Smoot et al. (1983). The combine results have a weighted average of 2.73 {+-} 0.05 K and are consistent with past measurements. They limit the possible Compton distortion of the Cosmic Background Radiation spectrum to less than 8%.

  20. Geometric biases in power-spectrum measurements

    NASA Astrophysics Data System (ADS)

    Samushia, L.; Branchini, E.; Percival, W. J.

    2015-10-01

    The observed distribution of galaxies has local transverse isotropy around the line of sight (LOS) with respect to the observer. The difference in the statistical clustering signal along and across the LOS encodes important information about the geometry of the Universe, its expansion rate and the rate of growth of structure within it. Because the LOS varies across a survey, the standard fast Fourier transform (FFT) based methods of measuring the anisotropic power spectrum (APS) cannot be used for surveys with wide observational footprint, other than to measure the monopole moment. We derive a simple analytic formula to quantify the bias for higher order Legendre moments, and we demonstrate that it is scale independent for a simple survey model, and depends only on the observed area. We derive a similar numerical correction formula for recently proposed alternative estimators of the APS that are based on summing over galaxies rather than using an FFT, and can therefore incorporate a varying LOS. We demonstrate that their bias depends on scale but not on the observed area. For a quadrupole the bias is always less than 1 per cent for k > 0.01 h Mpc^{-1} at z > 0.32. For a hexadecapole the bias is below 5 per cent for k > 0.05 h Mpc^{-1} at z > 0.32.

  1. Estimating the angular power spectrum of z > 2 BOSS QSOs using the MASTER method

    NASA Astrophysics Data System (ADS)

    Maldonado, Felipe; Huffenberger, Kevin; Rotti, Aditya

    2016-01-01

    We implement the MASTER method for angular power spectrum estimation and apply it to z > 2 quasars selected by the SDSS-III BOSS survey. Quasars are filtered for completeness and bad spectra, and include ~100,000 QSOs in the CORE sample and ~75,000 in the non-uniform BONUS sample. We estimate the angular power spectrum in redshift shells to constrain the matter power spectrum and quasar properties. In the future, we will jointly analyze overlapping Cosmic Microwave Background lensing maps from the Atacama Cosmology Telescope to place further constraints.

  2. Angular power spectrum of the FastICA CMB component from BEAST data

    NASA Astrophysics Data System (ADS)

    Donzelli, Simona

    We present the angular power spectrum of the CMB component extracted with FASTICA from the data of the Background Emission Anisotropy Scanning Telescope (BEAST), operating in Q two input channels FASTICA returns two possible independent components. We found that one of them has an unphysical spectral behaviour, due to the poor S/N ratio, while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte-Carlo (MC) simulations we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum

  3. Wind speed power spectrum analysis for Bushland, Texas

    SciTech Connect

    Eggleston, E.D.

    1996-12-31

    Numerous papers and publications on wind turbulence have referenced the wind speed spectrum presented by Isaac Van der Hoven in his article entitled Power Spectrum of Horizontal Wind Speed Spectrum in the Frequency Range from 0.0007 to 900 Cycles per Hour. Van der Hoven used data measured at different heights between 91 and 125 meters above the ground, and represented the high frequency end of the spectrum with data from the peak hour of hurricane Connie. These facts suggest we should question the use of his power spectrum in the wind industry. During the USDA - Agricultural Research Service`s investigation of wind/diesel system power storage, using the appropriate wind speed power spectrum became a significant issue. We developed a power spectrum from 13 years of hourly average data, 1 year of 5 minute average data, and 2 particularly gusty day`s 1 second average data all collected at a height of 10 meters. While the general shape is similar to the Van der Hoven spectrum, few of his peaks were found in the Bushland spectrum. While higher average wind speeds tend to suggest higher amplitudes in the high frequency end of the spectrum, this is not always true. Also, the high frequency end of the spectrum is not accurately described by simple wind statistics such as standard deviation and turbulence intensity. 2 refs., 5 figs., 1 tab.

  4. Estimating the Crustal Power Spectrum From Vector Magsat Data: Crustal Power Spectrum

    NASA Technical Reports Server (NTRS)

    Lowe, David A. J.; Parker, Robert L.; Purucker, Michael E.; Constable, Catherine G.

    2000-01-01

    The Earth's magnetic field can be subdivided into core and crustal components and we seek to characterize the crustal part through its spatial power spectrum (R(sub l)). We process vector Magsat data to isolate the crustal field and then invert power spectral densities of flight-local components along-track for R(sub l) following O'Brien et al. [1999]. Our model (LPPC) is accurate up to approximately degree 45 (lambda=900 km) - this is the resolution limit of our data and suggests that global crustal anomaly maps constructed from vector Magsat data should not contain features with wavelengths less than 900 km. We find continental power spectra to be greater than oceanic ones and attribute this to the relative thicknesses of continental and oceanic crust.

  5. EEG Power Spectrum Analysis in Children with ADHD

    PubMed Central

    Kamida, Akira; Shimabayashi, Kenta; Oguri, Masayoshi; Takamori, Toshihiro; Ueda, Naoyuki; Koyanagi, Yuki; Sannomiya, Naoko; Nagira, Haruki; Ikunishi, Saeko; Hattori, Yuiko; Sato, Kengo; Fukuda, Chisako; Hirooka, Yasuaki; Maegaki, Yoshihiro

    2016-01-01

    Background Attention deficit disorder/hyperactivity disorder (ADHD) is a pathological condition that is not fully understood. In this study, we investigated electroencephalographic (EEG) power differences between children with ADHD and healthy control children. Methods EEGs were recorded as part of routine medical care received by 80 children with ADHD aged 4–15 years at the Department of Pediatric Neurology in Tottori University Hospital. Additionally, we recorded in 59 control children aged 4–15 years after obtaining informed consent. Specifically, awake EEG signals were recorded from each child using the international 10–20 system, and we used ten 3-s epochs on the EEG power spectrum to calculate the powers of individual EEG frequency bands. Results The powers of different EEG bands were significantly higher in the frontal brain region of those in the ADHD group compared with the control group. In addition, the power of the beta band in the ADHD group was significantly higher in all brain regions, except for the occipital region, compared with control children. With regard to developmental changes, the power of the alpha band in the occipital region showed an age-dependent decrease in both groups, with slightly lower power in the ADHD group. Additionally, the intergroup difference decreased in children aged 11 years or older. As with the alpha band in the occipital region, the beta band in the frontal region showed an age-dependent decrease in both groups. Unlike the alpha band, the power of the beta band was higher in the ADHD group than in the control group for children of all ages. Conclusion The observed intergroup differences in EEG power may provide insight into the brain function of children with ADHD. PMID:27493489

  6. Effects of Background Noise on Cortical Encoding of Speech in Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Russo, Nicole; Zecker, Steven; Trommer, Barbara; Chen, Julia; Kraus, Nina

    2009-01-01

    This study provides new evidence of deficient auditory cortical processing of speech in noise in autism spectrum disorders (ASD). Speech-evoked responses (approximately 100-300 ms) in quiet and background noise were evaluated in typically-developing (TD) children and children with ASD. ASD responses showed delayed timing (both conditions) and…

  7. Power spectrum and non-Gaussianities in anisotropic inflation

    SciTech Connect

    Dey, Anindya; Kovetz, Ely D.; Paban, Sonia E-mail: elykovetz@gmail.com

    2014-06-01

    We study the planar regime of curvature perturbations for single field inflationary models in an axially symmetric Bianchi I background. In a theory with standard scalar field action, the power spectrum for such modes has a pole as the planarity parameter goes to zero. We show that constraints from back reaction lead to a strong lower bound on the planarity parameter for high-momentum planar modes and use this bound to calculate the signal-to-noise ratio of the anisotropic power spectrum in the CMB, which in turn places an upper bound on the Hubble scale during inflation allowed in our model. We find that non-Gaussianities for these planar modes are enhanced for the flattened triangle and the squeezed triangle configurations, but show that the estimated values of the f{sub NL} parameters remain well below the experimental bounds from the CMB for generic planar modes (other, more promising signatures are also discussed). For a standard action, f{sub NL} from the squeezed configuration turns out to be larger compared to that from the flattened triangle configuration in the planar regime. However, in a theory with higher derivative operators, non-Gaussianities from the flattened triangle can become larger than the squeezed configuration in a certain limit of the planarity parameter.

  8. Terahertz spectrum analyzer based on frequency and power measurement.

    PubMed

    Yee, Dae-Su; Jang, Yudong; Kim, Youngchan; Seo, Dae-Cheol

    2010-08-01

    We demonstrate a terahertz (THz) spectrum analyzer based on frequency and power measurement. A power spectrum of a continuous THz wave is measured through optical heterodyne detection using an electromagnetic THz frequency comb and a bolometer and power measurement using a bolometer with a calibrated responsivity. The THz spectrum analyzer has a frequency precision of 1x10(-11), a frequency resolution of 1Hz, a frequency band up to 1.7THz, and an optical noise equivalent power of approximately 1 pW/Hz(1/2). PMID:20680048

  9. Background radiation measurements at high power research reactors

    NASA Astrophysics Data System (ADS)

    Ashenfelter, J.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; Cherwinka, J. J.; Chu, R.; Classen, T.; Davee, D.; Dean, D.; Deichert, G.; Dolinski, M. J.; Dolph, J.; Dwyer, D. A.; Fan, S.; Gaison, J. K.; Galindo-Uribarri, A.; Gilje, K.; Glenn, A.; Green, M.; Han, K.; Hans, S.; Heeger, K. M.; Heffron, B.; Jaffe, D. E.; Kettell, S.; Langford, T. J.; Littlejohn, B. R.; Martinez, D.; McKeown, R. D.; Morrell, S.; Mueller, P. E.; Mumm, H. P.; Napolitano, J.; Norcini, D.; Pushin, D.; Romero, E.; Rosero, R.; Saldana, L.; Seilhan, B. S.; Sharma, R.; Stemen, N. T.; Surukuchi, P. T.; Thompson, S. J.; Varner, R. L.; Wang, W.; Watson, S. M.; White, B.; White, C.; Wilhelmi, J.; Williams, C.; Wise, T.; Yao, H.; Yeh, M.; Yen, Y.-R.; Zhang, C.; Zhang, X.

    2016-01-01

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. The general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.

  10. Background radiation measurements at high power research reactors

    SciTech Connect

    Ashenfelter, J.; Yeh, M.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; Cherwinka, J. J.; Chu, R.; Classen, T.; Davee, D.; Dean, D.; Deichert, G.; Dolinski, M. J.; Dolph, J.; Dwyer, D. A.; Fan, S.; Gaison, J. K.; Galindo-Uribarri, A.; Gilje, K.; Glenn, A.; Green, M.; Han, K.; Hans, S.; Heeger, K. M.; Heffron, B.; Jaffe, D. E.; Kettell, S.; Langford, T. J.; Littlejohn, B. R.; Martinez, D.; McKeown, R. D.; Morrell, S.; Mueller, P. E.; Mumm, H. P.; Napolitano, J.; Norcini, D.; Pushin, D.; Romero, E.; Rosero, R.; Saldana, L.; Seilhan, B. S.; Sharma, R.; Stemen, N. T.; Surukuchi, P. T.; Thompson, S. J.; Varner, R. L.; Wang, W.; Watson, S. M.; White, B.; White, C.; Wilhelmi, J.; Williams, C.; Wise, T.; Yao, H.; Yen, Y. -R.; Zhang, C.; Zhang, X.

    2015-10-23

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. Furthermore, the general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.

  11. Power spectrum, correlation function, and tests for luminosity bias in the CfA redshift survey

    NASA Technical Reports Server (NTRS)

    Park, Changbom; Vogeley, Michael S.; Geller, Margaret J.; Huchra, John P.

    1994-01-01

    We describe and apply a method for directly computing the power spectrum for the galaxy distribution in the extension of the Center for Astrophysics Redshift Survey. Tests show that our technique accurately reproduces the true power spectrum for k greater than 0.03 h Mpc(exp -1). The dense sampling and large spatial coverage of this survey allow accurate measurement of the redshift-space power spectrum on scales from 5 to approximately 200 h(exp -1) Mpc. The power spectrum has slope n approximately equal -2.1 on small scales (lambda less than or equal 25 h(exp -1) Mpc) and n approximately -1.1 on scales 30 less than lambda less than 120 h(exp -1) Mpc. On larger scales the power spectrum flattens somewhat, but we do not detect a turnover. Comparison with N-body simulations of cosmological models shows that an unbiased, open universe CDM model (OMEGA h = 0.2) and a nonzero cosmological constant (CDM) model (OMEGA h = 0.24, lambda(sub zero) = 0.6, b = 1.3) match the CfA power spectrum over the wavelength range we explore. The standard biased CDM model (OMEGA h = 0.5, b = 1.5) fails (99% significance level) because it has insufficient power on scales lambda greater than 30 h(exp -1) Mpc. Biased CDM with a normalization that matches the Cosmic Microwave Background (CMB) anisotropy (OMEGA h = 0.5, b = 1.4, sigma(sub 8) (mass) = 1) has too much power on small scales to match the observed galaxy power spectrum. This model with b = 1 matches both Cosmic Background Explorer Satellite (COBE) and the small-scale power spect rum but has insufficient power on scales lambda approximately 100 h(exp -1) Mpc. We derive a formula for the effect of small-scale peculiar velocities on the power spectrum and combine this formula with the linear-regime amplification described by Kaiser to compute an estimate of the real-space power spectrum. Two tests reveal luminosity bias in the galaxy distribution: First, the amplitude of the pwer spectrum is approximately 40% larger for the brightest

  12. MEASUREMENT OF COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRA FROM TWO YEARS OF BICEP DATA

    SciTech Connect

    Chiang, H. C.; Barkats, D.; Bock, J. J.; Hristov, V. V.; Jones, W. C.; Kovac, J. M.; Lange, A. E.; Mason, P. V.; Matsumura, T.; Ade, P. A. R.; Battle, J. O.; Dowell, C. D.; Nguyen, H. T.; Bierman, E. M.; Keating, B. G.; Duband, L.; Hivon, E. F.; Holzapfel, W. L.; Kuo, C. L.; Leitch, E. M.

    2010-03-10

    Background Imaging of Cosmic Extragalactic Polarization (BICEP) is a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background (CMB) at degree angular scales. During three seasons of observing at the South Pole (2006 through 2008), BICEP mapped {approx}2% of the sky chosen to be uniquely clean of polarized foreground emission. Here, we present initial results derived from a subset of the data acquired during the first two years. We present maps of temperature, Stokes Q and U, E and B modes, and associated angular power spectra. We demonstrate that the polarization data are self-consistent by performing a series of jackknife tests. We study potential systematic errors in detail and show that they are sub-dominant to the statistical errors. We measure the E-mode angular power spectrum with high precision at 21 <= l <= 335, detecting for the first time the peak expected at l {approx} 140. The measured E-mode spectrum is consistent with expectations from a LAMBDACDM model, and the B-mode spectrum is consistent with zero. The tensor-to-scalar ratio derived from the B-mode spectrum is r = 0.02{sup +0.31}{sub -0.26}, or r < 0.72 at 95% confidence, the first meaningful constraint on the inflationary gravitational wave background to come directly from CMB B-mode polarization.

  13. The REFLEX II galaxy cluster survey: power spectrum analysis

    NASA Astrophysics Data System (ADS)

    Balaguera-Antolínez, A.; Sánchez, Ariel G.; Böhringer, H.; Collins, C.; Guzzo, L.; Phleps, S.

    2011-05-01

    We present the power spectrum of galaxy clusters measured from the new ROSAT-ESO Flux-Limited X-Ray (REFLEX II) galaxy cluster catalogue. This new sample extends the flux limit of the original REFLEX catalogue to 1.8 × 10-12 erg s-1 cm-2, yielding a total of 911 clusters with ≥94 per cent completeness in redshift follow-up. The analysis of the data is improved by creating a set of 100 REFLEX II-catalogue-like mock galaxy cluster catalogues built from a suite of large-volume Λ cold dark matter (ΛCDM) N-body simulations (L-BASICC II). The measured power spectrum is in agreement with the predictions from a ΛCDM cosmological model. The measurements show the expected increase in the amplitude of the power spectrum with increasing X-ray luminosity. On large scales, we show that the shape of the measured power spectrum is compatible with a scale-independent bias and provide a model for the amplitude that allows us to connect our measurements with a cosmological model. By implementing a luminosity-dependent power-spectrum estimator, we observe that the power spectrum measured from the REFLEX II sample is weakly affected by flux-selection effects. The shape of the measured power spectrum is compatible with a featureless power spectrum on scales k > 0.01 h Mpc-1 and hence no statistically significant signal of baryonic acoustic oscillations can be detected. We show that the measured REFLEX II power spectrum displays signatures of non-linear evolution.

  14. Reference MWA EoR Power Spectrum analysis

    NASA Astrophysics Data System (ADS)

    Hazelton, Bryna; Pober, Jonathan; Beardsley, Adam; Morales, Miguel F.; Sullivan, Ian S.; MWA Collaboration

    2015-01-01

    Observations of the Epoch of Reionization using redshifted 21cm HI emission promise to provide sensitive new cosmological constraints in the next few years. The current generation of HI EoR telescopes are targeting a statistical detection of the EoR in the power spectrum of the 21cm emission. The principal challenge lies in extracting the faint cosmological signal in the face of bright foregrounds and instrumental systematics that threaten to overwhelm it.We present the UW EoR power spectrum code, the reference code for the MWA and the first power spectrum analysis to analytically propagate the error bars through the full data analysis pipeline. We demonstrate the sensitivity of the power spectrum as a diagnostic tool for identifying subtle systematics and show power spectra of the first season of MWA observations.

  15. The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology

    NASA Astrophysics Data System (ADS)

    Jacobs, Daniel C.; Hazelton, B. J.; Trott, C. M.; Dillon, Joshua S.; Pindor, B.; Sullivan, I. S.; Pober, J. C.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; Corey, B. E.; de Oliveira-Costa, A.; Emrich, D.; Ewall-Wice, A.; Feng, L.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hewitt, J. N.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kaplan, D. L.; Kasper, J. C.; Kim, HS; Kratzenberg, E.; Lenc, E.; Line, J.; Loeb, A.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Neben, A. R.; Thyagarajan, N.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Paul, S.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Udaya Shankar, N.; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Tegmark, M.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-07-01

    We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple independent data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction, and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds.

  16. Is natural background or radiation from nuclear power plants leukemogenic

    SciTech Connect

    Cronkite, E.P.

    1989-01-01

    The objective in this review is to provide some facts about normal hemopoietic cell proliferation relevant to leukemogenesis, physical, chemical, and biological facts about radiation effects with the hope that each person will be able to decide for themselves whether background radiation or emissions from nuclear power plants and facilities significantly add to the spontaneous leukemia incidence. 23 refs., 1 tab.

  17. The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation

    NASA Technical Reports Server (NTRS)

    Ressell, M. Ted; Turner, Michael S.

    1989-01-01

    The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

  18. Cosmic microwave background dipole spectrum measured by the COBE FIRAS instrument

    NASA Technical Reports Server (NTRS)

    Fixsen, D. J.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Isaacman, R. B.; Mather, J. C.; Meyer, S. S.; Noerdlinger, P. D.; Shafer, R. A.; Weiss, R.

    1994-01-01

    The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) has determined the dipole spectrum of the cosmic microwave background radiation (CMBR) from 2 to 20/cm. For each frequency the signal is decomposed by fitting to a monopole, a dipole, and a Galactic template for approximately 60% of the sky. The overall dipole spectrum fits the derivative of a Planck function with an amplitude of 3.343 +/- 0.016 mK (95% confidence level), a temperature of 2.714 +/- 0.022 K (95% confidence level), and an rms deviation of 6 x 10(exp -9) ergs/sq cm/s/sr cm limited by a detector and cosmic-ray noise. The monopole temperature is consistent with that determined by direct measurement in the accompanying article by Mather et al.

  19. Monte-Carlo Simulations of the Suzaku-XRS Residual Background Spectrum

    NASA Technical Reports Server (NTRS)

    Perinati, E.; Kilbourne, Caroline Anne; Colasanti, L.; Lotti, S.; Macculi, C.; Piro, L.; Mineo, T.; Mitsuda, K.; Bonardi, A.; Santangelo, A.

    2012-01-01

    Cryogenic micro-calorimeters are suitable to detect small amounts of energy deposited by electromagnetic and nuclear interactions, which makes them attractive in a variety of applications on ground and in space. The only X-ray microcalorimeter that operated in orbit to date is the X-Ray Spectrometer on-board of the Japanese Suzaku satellite. We discuss the analysis of the components of its residual background spectrum with the support of Monte-Carlo simulations.

  20. Low Frequency Measurement of the Spectrum of the Cosmic Background Radiation

    DOE R&D Accomplishments Database

    Smoot, G. F.; De Amici, G.; Friedman, S. D.; Witebsky, C.; Mandolesi, N.; Partridge, R. B.; Sironi, G.; Danese, L.; De Zotti, G.

    1983-06-01

    We have made measurements of the cosmic background radiation spectrum at 5 wavelengths (0.33, 0.9, 3, 6.3, and 12 cm) using radiometers with wavelength-scaled corrugated horn antennas having very low sidelobes. A single large-mouth (0.7 m diameter) liquid-helium-cooled absolute reference load was used for all five radiometers. The results of the observations are consistent with previous measurements and represent a significant improvement in accuracy.

  1. Spectrum management considerations of adaptive power control in satellite networks

    NASA Technical Reports Server (NTRS)

    Sawitz, P.; Sullivan, T.

    1983-01-01

    Adaptive power control concepts for the compensation of rain attenuation are considered for uplinks and downlinks. The performance of example power-controlled and fixed-EIRP uplinks is compared in terms of C/Ns and C/Is. Provisional conclusions are drawn with regard to the efficacy of uplink and downlink power control orbit/spectrum utilization efficiency.

  2. Background radiation measurements at high power research reactors

    DOE PAGESBeta

    Ashenfelter, J.; Yeh, M.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; et al

    2015-10-23

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the backgroundmore » fields encountered. Furthermore, the general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.« less

  3. MEASURING THE JET POWER OF FLAT-SPECTRUM RADIO QUASARS

    SciTech Connect

    Shabala, S. S.; Santoso, J. S.; Godfrey, L. E. H.

    2012-09-10

    We use frequency-dependent position shifts of flat-spectrum radio cores to estimate the kinetic power of active galactic nucleus (AGN) jets. We find a correlation between the derived jet powers and AGN narrow-line luminosity, consistent with the well-known relation for radio galaxies and steep spectrum quasars. This technique can be applied to intrinsically weak jets even at high redshift.

  4. Spline-based Study of the Extragalactic Background Light Spectrum using Gamma-Ray Observations

    NASA Astrophysics Data System (ADS)

    Bose, Anoushka; Rathmann-Bloch, Julia; Biteau, Jonathan; Williams, David A.

    2016-01-01

    The extragalactic background light (EBL) is made of all the light emitted by stars and galaxies throughout cosmic history. Expanding on the work of Biteau & Williams 2015, we develop a novel natural cubic spline model of the local EBL spectrum and constrain its parameters using the gamma-ray spectra of 38 blazars measured in the high-energy (HE, 0.1 to 100 GeV) and very-high-energy (VHE, 0.1 to 20 TeV) bands. Starting from this best-fit model, we then study the so-called "delta gamma" (ΔΓ) observable, defined as the difference between the VHE and HE photon indices. This second study is focused on a subset of nine BL Lac objects. The application of a scaling factor to the cosmic optical background (0.1 - 10 nm) significantly impacts the predicted ΔΓ as a function of redshift, whereas a similar modification of the cosmic infrared background (10 - 1000 nm) has no impact. We conclude that the simple delta gamma approach can only constrain part of the EBL spectrum, while a detailed study of the spectra, such as presented in the first part of this research, is needed to constrain the cosmic infrared background.

  5. On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Lidz, Adam; Taylor, Jessie

    2016-07-01

    Line intensity mapping experiments seek to trace large-scale structures by measuring the spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. An important systematic concern for these surveys is line confusion from foreground or background galaxies emitting in other lines that happen to lie at the same observed frequency as the “target” emission line of interest. We develop an approach to separate this “interloper” emission at the power spectrum level. If one adopts the redshift of the target emission line in mapping from observed frequency and angle on the sky to co-moving units, the interloper emission is mapped to the wrong co-moving coordinates. Because the mapping is different in the line of sight and transverse directions, the interloper contribution to the power spectrum becomes anisotropic, especially if the interloper and target emission are at widely separated redshifts. This distortion is analogous to the Alcock–Paczynski test, but here the warping arises from assuming the wrong redshift rather than an incorrect cosmological model. We apply this to the case of a hypothetical [C ii] emission survey at z˜ 7 and find that the distinctive interloper anisotropy can, in principle, be used to separate strong foreground CO emission fluctuations. In our models, however, a significantly more sensitive instrument than currently planned is required, although there are large uncertainties in forecasting the high-redshift [C ii] emission signal. With upcoming surveys, it may nevertheless be useful to apply this approach after first masking pixels suspected of containing strong interloper contamination.

  6. On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Lidz, Adam; Taylor, Jessie

    2016-07-01

    Line intensity mapping experiments seek to trace large-scale structures by measuring the spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. An important systematic concern for these surveys is line confusion from foreground or background galaxies emitting in other lines that happen to lie at the same observed frequency as the “target” emission line of interest. We develop an approach to separate this “interloper” emission at the power spectrum level. If one adopts the redshift of the target emission line in mapping from observed frequency and angle on the sky to co-moving units, the interloper emission is mapped to the wrong co-moving coordinates. Because the mapping is different in the line of sight and transverse directions, the interloper contribution to the power spectrum becomes anisotropic, especially if the interloper and target emission are at widely separated redshifts. This distortion is analogous to the Alcock–Paczynski test, but here the warping arises from assuming the wrong redshift rather than an incorrect cosmological model. We apply this to the case of a hypothetical [C ii] emission survey at z∼ 7 and find that the distinctive interloper anisotropy can, in principle, be used to separate strong foreground CO emission fluctuations. In our models, however, a significantly more sensitive instrument than currently planned is required, although there are large uncertainties in forecasting the high-redshift [C ii] emission signal. With upcoming surveys, it may nevertheless be useful to apply this approach after first masking pixels suspected of containing strong interloper contamination.

  7. Primordial black holes under the double inflationary power spectrum

    NASA Astrophysics Data System (ADS)

    Kim, Hee Il

    2000-09-01

    Recently, it has been shown that the primordial black holes (PBHs) produced by near critical collapse in the expanding universe have a scaling mass relation similar to that of black holes produced in asymptotically flat spacetime. Distinct from PBHs formed with a mass about the size of the horizon mass (type I), the PBHs with the scaling relation (type II) can be created with a range of masses at a given formation time. In general, only the case in which the PBH formation is concentrated at one epoch has been considered. However, it is expected that PBH formation is possible over a broad range of epochs if the density fluctuation has a rather large amplitude and smooth scale dependence. In this paper, we study the PBH formation for both types assuming the power spectrum of double inflationary models in which the small scale fluctuations could have large amplitudes independent of the CMBR anisotropy. The mass spectrum of type II PBHs is newly constructed without limiting the PBH formation period. The double inflationary power spectrum is assumed to be of double simple power law which are smoothly connected. Under the assumed power spectrum, the accumulation of small PBHs formed at later times is important and the mass range is significantly broadened for both types. The PBH mass spectra are far smoother than the observed MACHO spectrum due to our assumption of a smooth spectrum. In order to fit the observation, a more spiky spectrum is required.

  8. The matter power spectrum of dark energy models and the Harrison-Zel'dovich prescription

    SciTech Connect

    Duran, Ivan; Pavón, Diego; Atrio-Barandela, Fernando E-mail: atrio@usal.es

    2012-04-01

    According to the Harrison-Zel'dovich prescription, the amplitude of matter density perturbations at horizon crossing is the same at all scales. Based on this prescription, we show how to construct the matter power spectrum of generic dark energy models from the power spectrum of a ΛCDM model without the need of solving in full the dynamical equations describing the evolution of all energy density perturbations. Our approach allows to make model predictions of observables that can be expressed in terms of the matter power spectrum alone, such as the amplitude of matter fluctuations, peculiar velocities, cosmic microwave background temperature anisotropies on large angular scales or the weak lensing convergence spectrum. Then, models that have been tested only at the background level using the rate of the expansion of the Universe can now be tested using data on gravitational clustering and on large scale structure. This method can save a lot of effort in checking the validity of dark energy models. As an example of the accurateness of the approximation used, we compute the power spectrum of different dark energy models with constant equation of state parameter (w{sub DE} = −0.1, -0.5 and -0.8, ruled out by observations but easy to compare to numerical solutions) using our methodology and discuss the constraints imposed by the low multipoles of the cosmic microwave background.

  9. CMB anisotropy power spectrum using linear combinations of WMAP maps

    SciTech Connect

    Saha, Rajib; Prunet, Simon; Jain, Pankaj; Souradeep, Tarun

    2008-07-15

    In recent years the goal of estimating different cosmological parameters precisely has set new challenges in the effort to accurately measure the angular power spectrum of the CMB. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. Recently, a novel, model-independent method for the estimation of the CMB angular power spectrum solely from multifrequency observations has been proposed and implemented on the first year WMAP data by Saha et al. 2006. All previous estimates of the power spectrum of the CMB are based upon foreground templates using data sets from different experiments. However, our methodology demonstrates that the CMB angular spectrum can be reliably estimated with precision from a self-contained analysis of the WMAP data. In this work we provide a detailed description of this method. We also study and identify the biases present in our power spectrum estimate. We apply our methodology to extract the power spectrum from the WMAP data.

  10. The wedge bias in reionization 21-cm power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Jensen, Hannes; Majumdar, Suman; Mellema, Garrelt; Lidz, Adam; Iliev, Ilian T.; Dixon, Keri L.

    2016-02-01

    A proposed method for dealing with foreground emission in upcoming 21-cm observations from the epoch of reionization is to limit observations to an uncontaminated window in Fourier space. Foreground emission can be avoided in this way, since it is limited to a wedge-shaped region in k∥, k⊥ space. However, the power spectrum is anisotropic owing to redshift-space distortions from peculiar velocities. Consequently, the 21-cm power spectrum measured in the foreground avoidance window - which samples only a limited range of angles close to the line-of-sight direction - differs from the full redshift-space spherically averaged power spectrum which requires an average over all angles. In this paper, we calculate the magnitude of this `wedge bias' for the first time. We find that the bias amplifies the difference between the real-space and redshift-space power spectra. The bias is strongest at high redshifts, where measurements using foreground avoidance will overestimate the redshift-space power spectrum by around 100 per cent, possibly obscuring the distinctive rise and fall signature that is anticipated for the spherically averaged 21-cm power spectrum. In the later stages of reionization, the bias becomes negative, and smaller in magnitude (≲20 per cent).

  11. IMPACT OF CLUSTER PHYSICS ON THE SUNYAEV-ZEL'DOVICH POWER SPECTRUM

    SciTech Connect

    Shaw, Laurie D.; Nagai, Daisuke; Bhattacharya, Suman; Lau, Erwin T.

    2010-12-20

    We use an analytic model to investigate the theoretical uncertainty on the thermal Sunyaev-Zel'dovich (SZ) power spectrum due to astrophysical uncertainties in the thermal structure of the intracluster medium. Our model accounts for star formation and energy feedback (from supernovae and active galactic nuclei) as well as radially dependent non-thermal pressure support due to random gas motions, the latter calibrated by recent hydrodynamical simulations. We compare the model against X-ray observations of low-redshift clusters, finding excellent agreement with observed pressure profiles. Varying the levels of feedback and non-thermal pressure support can significantly change both the amplitude and shape of the thermal SZ power spectrum. Increasing the feedback suppresses power at small angular scales, shifting the peak of the power spectrum to lower l. On the other hand, increasing the non-thermal pressure support has the opposite effect, significantly reducing power at large angular scales. In general, including non-thermal pressure at the level measured in simulations has a large effect on the power spectrum, reducing the amplitude by 50% at angular scales of a few arcminutes compared to a model without a non-thermal component. Our results demonstrate that measurements of the shape of the power spectrum can reveal useful information on important physical processes in groups and clusters, especially at high redshift where there exists little observational data. Comparing with the recent South Pole Telescope measurements of the small-scale cosmic microwave background power spectrum, we find our model reduces the tension between the values of {sigma}{sub 8} measured from the SZ power spectrum and from cluster abundances.

  12. Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings

    SciTech Connect

    Yamauchi, Daisuke; Yoo, Chul-Moon; Sasaki, Misao; Takahashi, Keitaro; Sendouda, Yuuiti

    2010-09-15

    We present a new analytical method to calculate the small angle cosmic microwave background (CMB) temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability P. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of P has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the case of conventional cosmic strings is in very good agreement with the numerical result obtained by Fraisse et al.. Then we estimate the upper bound on the dimensionless tension of the string for various values of P by assuming that the fraction of the CMB power spectrum due to cosmic (super-)strings is less than ten percent at various angular scales up to l=2000. We find that the amplitude of the spectrum increases as the intercommuting probability. As a consequence, strings with smaller intercommuting probabilities are found to be more tightly constrained.

  13. Measurement of the cosmic microwave background spectrum by the COBE FIRAS instrument

    NASA Technical Reports Server (NTRS)

    Mather, J. C.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Fixsen, D. J.; Hewagama, T.; Isaacman, R. B.; Jensen, K. A.; Meyer, S. S.; Noerdlinger, P. D.

    1994-01-01

    The cosmic microwave background radiation (CMBR) has a blackbody spectrum within 3.4 x 10(exp -8) ergs/sq cm/s/sr cm over the frequency range from 2 to 20/cm (5-0.5 mm). These measurements, derived from the Far-Infrared Absolute Spectrophotomer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite, imply stringent limits on energy release in the early universe after t approximately 1 year and redshift z approximately 3 x 10(exp 6). The deviations are less than 0.30% of the peak brightness, with an rms value of 0.01%, and the dimensionless cosmological distortion parameters are limited to the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) (95% confidence level). The temperature of the CMBR is 2.726 +/- 0.010 K (95% confidence level systematic).

  14. The power spectrum of galaxies in the nearby universe

    NASA Technical Reports Server (NTRS)

    Da Costa, L. Nicolaci; Vogeley, Michael S.; Geller, Margaret J.; Huchra, John P.; Park, Changbom

    1994-01-01

    We compute the power spectrum of galaxy density fluctuations in a recently completed Southern Sky Redshift Survey of optically selected galaxies (SSRS2). The amplitude and shape of the SSRS2 power spectrum are consistent with results of the Center for Astrophysics redshift survey of the northern hemisphere (CfA2), including the abrupt change of slope on a scale of 30-50/h Mpc; these results are reproducible for independent volumes of space, and variations are consistent with the errors estimated from mock surveys. Taken together, the SSRS2 and the CfA2 form a complete sample of 14,383 galaxies which covers one-third of the sky. The power spectrum of this larger sample continues to rise on scales up to approximately 200/h Mpc, with weak evidence for flattening on the largest scales. The SSRS2 + CfA2 power spectrum and the power spectrum constraints implied by COBE are well matched by an Omega(h) is approximately 0.2, Omega + lambda(sub 0) = 1 cold dark matter model with minimal biasing of optically selected galaxies.

  15. On the information content of the matter power spectrum

    NASA Astrophysics Data System (ADS)

    Carron, J.; Wolk, M.; Szapudi, I.

    2015-10-01

    We discuss an analytical approximation for the matter power spectrum covariance matrix and its inverse on translinear scales, k ˜ 0.1h - 0.8 h Mpc-1 at z = 0. We proceed to give an analytical expression for the Fisher information matrix of the non-linear density-field spectrum, and derive implications for its cosmological information content. We find that the spectrum information is characterized by a pair of upper bounds, `plateaux', caused by the trispectrum, and a `knee' in the presence of white noise. The effective number of Fourier modes, normally growing as a power law, is bounded from above by these plateaux, explaining naturally earlier findings from N-body simulations. These plateaux limit best possible measurements of the non-linear power at the per cent level in an h-3 Gpc3 volume; the extraction of model parameters from the spectrum is limited explicitly by their degeneracy to the non-linear amplitude. The value of the first, supersurvey (SS) plateau depends on the characteristic survey volume and the large-scale power; the second, intra-survey plateau is set by the small-scale power. While both have simple interpretations within the hierarchical Ansatz, the SS plateau can be predicted and generalized to still smaller scales within Takada and Hu's spectrum response formalism. Finally, the noise knee is naturally set by the density of tracers.

  16. Visibility moments and power spectrum of turbulence velocity

    NASA Astrophysics Data System (ADS)

    Dutta, Prasun

    2016-02-01

    Here we introduce moments of visibility function and discuss how those can be used to estimate the power spectrum of the turbulent velocity of external spiral galaxies. We perform numerical simulation to confirm the credibility of this method and found that for galaxies with lower inclination angles it works fine. The estimator outlined here is unbiased and has the potential to recover the turbulent velocity spectrum completely from radio interferometric observations.

  17. Prediction of background in low-energy spectrum of Phoswich detector.

    PubMed

    Arun, B; Manohari, M; Mathiyarasu, R; Rajagopal, V; Jose, M T

    2014-12-01

    In vivo monitoring of actinides in occupational workers is done using Phoswich detector by measuring the low-energy X ray and gamma rays. Quantification of actinides like plutonium and americium in the lungs is extremely difficult due to higher background in the low-energy regions, which is from ambient background as well as from the subject. In the latter case, it is mainly due to the Compton scattering of body potassium, which varies person-to-person. Hence, an accurate prediction of subject-specific background counts in the lower-energy regions is an essential element in the in vivo measurement of plutonium and americium. Empirical equations are established for the prediction of background count rate in (239)Pu and (241)Am lower-energy regions, called 'target regions', as a function of count rate in the monitoring region (97-130 keV)/(40)K region in the high-energy spectrum, weight-to-height ratio of the subject (scattering parameter) and the gender. PMID:24300341

  18. The millimeter and submillimeter wavelength diffuse backgrounds: Measurements of the spectrum and anisotropy

    NASA Astrophysics Data System (ADS)

    Alsop, David Charles

    The results of two experiments to study the diffuse background at millimeter and submillimeter wavelengths are reported. The first experiment was a rocket-borne photometer designed to measure the spectrum of the background. The background was observed in six bands centered at 7, 13, 20, 30, 40, and 50 cm-1. After the flight, a systematic error was detected in the flight data. A model for the error was developed and an attempt at correction was made, but indications that the correction was not complete were found. The second experiment was a search for anisotropy in the Cosmic Microwave Background at one degree angular scales. The search employed a multiband, bolometric receiver mounted on a balloon-borne telescope. The search achieved the highest statistical sensitivity at this angular scale, which is of crucial importance for constraining theories of structure formation in the universe. Signals in excess of random were detected but concern over possible systematic error sources prevents the interpretation of the signals as uniquely cosmological in origin.

  19. The small scale power asymmetry in the cosmic microwave background

    SciTech Connect

    Flender, Samuel; Hotchkiss, Shaun E-mail: shaun.hotchkiss@helsinki.fi

    2013-09-01

    We investigate the hemispherical power asymmetry in the cosmic microwave background on small angular scales. We find an anomalously high asymmetry in the multipole range l = 601−2048, with a naive statistical significance of 6.5σ. However, we show that this extreme anomaly is simply a coincidence of three other effects, relativistic power modulation, edge effects from the mask applied, and inter-scale correlations. After correcting for all of these effects, the significance level drops to ∼ 1σ, i.e., there is no anomalous intrinsic asymmetry in the small angular scales. Using this null result, we derive a constraint on a potential dipolar modulation amplitude, A(k) < 0.0045 on the ∼ 10 Mpc-scale, at 95% C.L. This new constraint must be satisfied by any theoretical model attempting to explain the hemispherical asymmetry at large angular scales.

  20. THE COYOTE UNIVERSE. II. COSMOLOGICAL MODELS AND PRECISION EMULATION OF THE NONLINEAR MATTER POWER SPECTRUM

    SciTech Connect

    Heitmann, Katrin; Higdon, David; Williams, Brian J.; Lawrence, Earl; White, Martin; Habib, Salman; Wagner, Christian

    2009-11-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the 1% level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state, 'wCDM', cosmologies. In this paper, we demonstrate that a limited set of only 37 cosmological models-the 'Coyote Universe' suite-can be used to predict the nonlinear matter power spectrum to 1% over a prior parameter range set by current cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  1. The Coyote Universe. II. Cosmological Models and Precision Emulation of the Nonlinear Matter Power Spectrum

    NASA Astrophysics Data System (ADS)

    Heitmann, Katrin; Higdon, David; White, Martin; Habib, Salman; Williams, Brian J.; Lawrence, Earl; Wagner, Christian

    2009-11-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the 1% level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state, "wCDM", cosmologies. In this paper, we demonstrate that a limited set of only 37 cosmological models—the "Coyote Universe" suite—can be used to predict the nonlinear matter power spectrum to 1% over a prior parameter range set by current cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  2. The Coyote Universe II: Cosmological Models and Precision Emulation of the Nonlinear Matter Power Spectrum

    SciTech Connect

    Heitmann, Katrin; Habib, Salman; Higdon, David; Williams, Brian J; White, Martin; Wagner, Christian

    2008-01-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the one percent level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state 'wCDM' cosmologies. In this paper we demonstrate that a limited set of only 37 cosmological models -- the 'Coyote Universe' suite -- can be used to predict the nonlinear matter power spectrum at the required accuracy over a prior parameter range set by cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  3. Universal power law for the spectrum of breaking Riemann waves

    NASA Astrophysics Data System (ADS)

    Pelinovsky, Dmitry; Pelinovsky, Efim; Kartashova, Elena; Talipova, Tatiana

    2014-05-01

    The universal power law for the spectrum of one-dimensional breaking Riemann waves is justified for the simple wave equation with arbitrary nonlinearity. This equation describe the long surface and internal wave in the coastal zone. The spectrum of spatial amplitudes at the breaking time has an power asymptotic decay with exponent - 4/3. This spectrum is formed by the singularity of the form like x1/3 in the wave shape at the breaking time. In addition, we demonstrate numerically that the universal power law is observed for long time in the range of small wave numbers if small dissipation or dispersion is accounted in the viscous Burgers or Korteweg-de Vries equations.

  4. Noise power spectrum measurements under nonuniform gains and their compensations

    NASA Astrophysics Data System (ADS)

    Kim, Dong Sik; Kim, Eun; Shin, Choul Woo

    2016-03-01

    The fixed pattern noise, which is due to the nonuniform amplifier gains and scintillator sensitivities, should be alleviated in radiography imaging and should have less influence on measuring the noise power spectrum (NPS) of the radiography detector. In order to reduce the influence, background trend removing methods, which are based on low-pass filtering, polynomial fitting, and subtracting the average image of the uniform exposure images, are traditionally employed in the literature. In terms of removing the fixed pattern noise, the subtraction method shows a good performance. However, the number of images to be averaged is practically finite and thus the noise contained in the average image contaminates the image difference and inflates the NPS curve. In this paper, an image formation model considering the nonuniform gain is constructed and two measuring methods, which are based on the subtraction and gain correction, respectively, are considered. In order to accurately measure a normalized NPS (NNPS) in the measuring methods, the number of images to be averaged is considered for NNPS compensations. For several flat-panel radiography detectors, the NNPS measurements are conducted and compared with conventional approaches, which have no compensation stages. Through experiments it is shown that the compensation can provide accurate NNPS measurements less influenced by the fixed pattern noise.

  5. Methods for Bayesian Power Spectrum Inference with Galaxy Surveys

    NASA Astrophysics Data System (ADS)

    Jasche, Jens; Wandelt, Benjamin D.

    2013-12-01

    We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves upon previous Bayesian methods by performing a joint inference of the three-dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases, and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate subsamples. This method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal-to-noise regimes by using a deterministic reversible jump algorithm. This approach reduces the correlation length of the sampler by several orders of magnitude, turning the otherwise numerically unfeasible problem of joint parameter exploration into a numerically manageable task. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity-dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. This method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20% effect across large ranges in k space. In addition, this method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters

  6. Methods for Bayesian power spectrum inference with galaxy surveys

    SciTech Connect

    Jasche, Jens; Wandelt, Benjamin D.

    2013-12-10

    We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves upon previous Bayesian methods by performing a joint inference of the three-dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases, and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate subsamples. This method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal-to-noise regimes by using a deterministic reversible jump algorithm. This approach reduces the correlation length of the sampler by several orders of magnitude, turning the otherwise numerically unfeasible problem of joint parameter exploration into a numerically manageable task. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity-dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. This method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20% effect across large ranges in k space. In addition, this method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters

  7. Statistical analysis of the cosmic microwave background: Power spectra and foregrounds

    NASA Astrophysics Data System (ADS)

    O'Dwyer, Ian J.

    2005-11-01

    In this thesis I examine some of the challenges associated with analyzing Cosmic Microwave Background (CMB) data and present a novel approach to solving the problem of power spectrum estimation, which is called MAGIC (MAGIC Allows Global Inference of Covariance). In light of the computational difficulty of a brute force approach to power spectrum estimation, I review several approaches which have been applied to the problem and show an example application of such an approximate method to experimental CMB data from the Background Emission Anisotropy Scanning Telescope (BEAST). I then introduce MAGIC, a new approach to power spectrum estimation; based on a Bayesian statistical analysis of the data utilizing Gibbs Sampling. I demonstrate application of this method to the all-sky Wilkinson Microwave Anistropy Probe WMAP data. The results are in broad agreement with those obtained originally by the WMAP team. Since MAGIC generates a full description of each C l it is possible to examine several issues raised by the best-fit WMAP power spectrum, for example the perceived lack of power at low ℓ. It is found that the distribution of C ℓ's at low l are significantly non-Gaussian and, based on the exact analysis presented here, the "low quadrupole issue" can be attributed to a statistical fluctuation. Finally, I examine the effect of Galactic foreground contamination on CMB experiments and describe the principle foregrounds. I show that it is possible to include the foreground components in a self-consistent fashion within the statistical framework of MAGIC and give explicit examples of how this might be achieved. Foreground contamination will become an increasingly important issue in CMB data analysis and the ability of this new algorithm to produce an exact power spectrum in a computationally feasible time, coupled with the foreground component separation and removal is an exciting development in CMB data analysis. When considered with current algorithmic developments

  8. Effect of curvaton decay on the primordial power spectrum

    NASA Astrophysics Data System (ADS)

    Firouzjahi, Hassan; Green, Anne M.; Malik, Karim A.; Zarei, Moslem

    2013-05-01

    We study the effect of curvaton decay on the primordial power spectrum. Using analytical approximations and also numerical calculations, we find that the power spectrum is enhanced during the radiation dominated era after the curvaton decay. The amplitude of the Bardeen potential is controlled by the fraction of the energy density in the curvaton at the time of curvaton decay. We show that the enhancement in the amplitude of the primordial curvature perturbation is, however, not large enough to lead to primordial black hole overproduction on scales which reenter the horizon after the time of curvaton decay.

  9. Reexamination of the Power Spectrum in De Sitter Inflation

    NASA Astrophysics Data System (ADS)

    Agulló, Iván; Navarro-Salas, José; Olmo, Gonzalo J.; Parker, Leonard

    2008-10-01

    We find that the amplitude of quantum fluctuations of the invariant de Sitter vacuum coincides exactly with that of the vacuum of a comoving observer for a massless scalar (inflaton) field. We propose redefining the actual physical power spectrum as the difference between the amplitudes of the above vacua. An inertial particle detector continues to observe the Gibbons-Hawking temperature. However, although the resulting power spectrum is still scale-free, its amplitude can be drastically reduced since now, instead of the Hubble’s scale at the inflationary period, it is determined by the square of the mass of the inflaton fluctuation field.

  10. Kolmogorov spectrum of renewable wind and solar power fluctuations

    NASA Astrophysics Data System (ADS)

    Tabar, M. Reza Rahimi; Anvari, M.; Lohmann, G.; Heinemann, D.; Wächter, M.; Milan, P.; Lorenz, E.; Peinke, Joachim

    2014-10-01

    With increasing the contribution of renewable energies in power production, the task of reducing dynamic instability in power grids must also be addressed from the generation side, because the power delivered from such sources is spatiotemporally stochastic in nature. Here we characterize the stochastic properties of the wind and solar energy sources by studying their spectrum and multifractal exponents. The computed power spectrum from high frequency time series of solar irradiance and wind power reveals a power-law behaviour with an exponent ˜ 5/3 (Kolmogorov exponent) for the frequency domain 0.001 Hz < f < 0.05 Hz, which means that the power grid is being fed by turbulent-like sources. Our results bring important evidence on the stochastic and turbulent-like behaviour of renewable power production from wind and solar energies, which can cause instability in power grids. Our statistical analysis also provides important information that must be used as a guideline for an optimal design of power grids that operate under intermittent renewable sources of power.

  11. Red, Straight, no bends: primordial power spectrum reconstruction from CMB and large-scale structure

    NASA Astrophysics Data System (ADS)

    Ravenni, Andrea; Verde, Licia; Cuesta, Antonio J.

    2016-08-01

    We present a minimally parametric, model independent reconstruction of the shape of the primordial power spectrum. Our smoothing spline technique is well-suited to search for smooth features such as deviations from scale invariance, and deviations from a power law such as running of the spectral index or small-scale power suppression. We use a comprehensive set of the state-of the art cosmological data: Planck observations of the temperature and polarisation anisotropies of the cosmic microwave background, WiggleZ and Sloan Digital Sky Survey Data Release 7 galaxy power spectra and the Canada-France-Hawaii Lensing Survey correlation function. This reconstruction strongly supports the evidence for a power law primordial power spectrum with a red tilt and disfavours deviations from a power law power spectrum including small-scale power suppression such as that induced by significantly massive neutrinos. This offers a powerful confirmation of the inflationary paradigm, justifying the adoption of the inflationary prior in cosmological analyses.

  12. Primordial power spectrum: a complete analysis with the WMAP nine-year data

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2013-07-01

    We have improved further the error sensitive Richardson-Lucy deconvolution algorithm making it applicable directly on the un-binned measured angular power spectrum of Cosmic Microwave Background observations to reconstruct the form of the primordial power spectrum. This improvement makes the application of the method significantly more straight forward by removing some intermediate stages of analysis allowing a reconstruction of the primordial spectrum with higher efficiency and precision and with lower computational expenses. Applying the modified algorithm we fit the WMAP 9 year data using the optimized reconstructed form of the primordial spectrum with more than 300 improvement in χ2eff with respect to the best fit power-law. This is clearly beyond the reach of other alternative approaches and reflects the efficiency of the proposed method in the reconstruction process and allow us to look for any possible feature in the primordial spectrum projected in the CMB data. Though the proposed method allow us to look at various possibilities for the form of the primordial spectrum, all having good fit to the data, proper error-analysis is needed to test for consistency of theoretical models since, along with possible physical artefacts, most of the features in the reconstructed spectrum might be arising from fitting noises in the CMB data. Reconstructed error-band for the form of the primordial spectrum using many realizations of the data, all bootstrapped and based on WMAP 9 year data, shows proper consistency of power-law form of the primordial spectrum with the WMAP 9 data at all wave numbers. Including WMAP polarization data in to the analysis have not improved much our results due to its low quality but we expect Planck data will allow us to make a full analysis on CMB observations on both temperature and polarization separately and in combination.

  13. Primordial power spectrum: a complete analysis with the WMAP nine-year data

    SciTech Connect

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun E-mail: arman@apctp.org

    2013-07-01

    We have improved further the error sensitive Richardson-Lucy deconvolution algorithm making it applicable directly on the un-binned measured angular power spectrum of Cosmic Microwave Background observations to reconstruct the form of the primordial power spectrum. This improvement makes the application of the method significantly more straight forward by removing some intermediate stages of analysis allowing a reconstruction of the primordial spectrum with higher efficiency and precision and with lower computational expenses. Applying the modified algorithm we fit the WMAP 9 year data using the optimized reconstructed form of the primordial spectrum with more than 300 improvement in χ{sup 2}{sub eff} with respect to the best fit power-law. This is clearly beyond the reach of other alternative approaches and reflects the efficiency of the proposed method in the reconstruction process and allow us to look for any possible feature in the primordial spectrum projected in the CMB data. Though the proposed method allow us to look at various possibilities for the form of the primordial spectrum, all having good fit to the data, proper error-analysis is needed to test for consistency of theoretical models since, along with possible physical artefacts, most of the features in the reconstructed spectrum might be arising from fitting noises in the CMB data. Reconstructed error-band for the form of the primordial spectrum using many realizations of the data, all bootstrapped and based on WMAP 9 year data, shows proper consistency of power-law form of the primordial spectrum with the WMAP 9 data at all wave numbers. Including WMAP polarization data in to the analysis have not improved much our results due to its low quality but we expect Planck data will allow us to make a full analysis on CMB observations on both temperature and polarization separately and in combination.

  14. Reconstruction of the primordial power spectrum using temperature and polarisation data from multiple experiments

    SciTech Connect

    Nicholson, Gavin; Contaldi, Carlo R. E-mail: c.contaldi@imperial.ac.uk

    2009-07-01

    We develop a method to reconstruct the primordial power spectrum, P(k), using both temperature and polarisation data from the joint analysis of a number of Cosmic Microwave Background (CMB) observations. The method is an extension of the Richardson-Lucy algorithm, first applied in this context by Shafieloo and Souradeep [1]. We show how the inclusion of polarisation measurements can decrease the uncertainty in the reconstructed power spectrum. In particular, the polarisation data can constrain oscillations in the spectrum more effectively than total intensity only measurements. We apply the estimator to a compilation of current CMB results. The reconstructed spectrum is consistent with the best-fit power spectrum although we find evidence for a 'dip' in the power on scales k ≈ 0.002 Mpc{sup −1}. This feature appears to be associated with the WMAP power in the region 18 ≤ l ≤ 26 which is consistently below best-fit models. We also forecast the reconstruction for a simulated, Planck-like [2] survey including sample variance limited polarisation data.

  15. Reconstruction of the primordial power spectrum using temperature and polarisation data from multiple experiments

    NASA Astrophysics Data System (ADS)

    Nicholson, Gavin; Contaldi, Carlo R.

    2009-07-01

    We develop a method to reconstruct the primordial power spectrum, P(k), using both temperature and polarisation data from the joint analysis of a number of Cosmic Microwave Background (CMB) observations. The method is an extension of the Richardson-Lucy algorithm, first applied in this context by Shafieloo & Souradeep [1]. We show how the inclusion of polarisation measurements can decrease the uncertainty in the reconstructed power spectrum. In particular, the polarisation data can constrain oscillations in the spectrum more effectively than total intensity only measurements. We apply the estimator to a compilation of current CMB results. The reconstructed spectrum is consistent with the best-fit power spectrum although we find evidence for a `dip' in the power on scales k approx 0.002 Mpc-1. This feature appears to be associated with the WMAP power in the region 18 <= ell <= 26 which is consistently below best-fit models. We also forecast the reconstruction for a simulated, Planck-like [2] survey including sample variance limited polarisation data.

  16. A robust power spectrum split cancellation-based spectrum sensing method for cognitive radio systems

    NASA Astrophysics Data System (ADS)

    Qi, Pei-Han; Li, Zan; Si, Jiang-Bo; Gao, Rui

    2014-12-01

    Spectrum sensing is an essential component to realize the cognitive radio, and the requirement for real-time spectrum sensing in the case of lacking prior information, fading channel, and noise uncertainty, indeed poses a major challenge to the classical spectrum sensing algorithms. Based on the stochastic properties of scalar transformation of power spectral density (PSD), a novel spectrum sensing algorithm, referred to as the power spectral density split cancellation method (PSC), is proposed in this paper. The PSC makes use of a scalar value as a test statistic, which is the ratio of each subband power to the full band power. Besides, by exploiting the asymptotic normality and independence of Fourier transform, the distribution of the ratio and the mathematical expressions for the probabilities of false alarm and detection in different channel models are derived. Further, the exact closed-form expression of decision threshold is calculated in accordance with Neyman—Pearson criterion. Analytical and simulation results show that the PSC is invulnerable to noise uncertainty, and can achive excellent detection performance without prior knowledge in additive white Gaussian noise and flat slow fading channels. In addition, the PSC benefits from a low computational cost, which can be completed in microseconds.

  17. The X-ray variability of NGC 6814 - Power spectrum

    NASA Technical Reports Server (NTRS)

    Done, C.; Madejski, G. M.; Mushotzky, R. F.; Turner, T. J.; Koyama, K.; Kunieda, H.

    1992-01-01

    The existence of the periodic component seen in NGC 6814 with Exosat at 12,000 +/- 100 s is confirmed by a power spectrum and folded light curve analysis of unevenly sampled Ginga data. A comparison of the power spectra produced from simulated light curves with that observed enables the intrinsic shape of the power spectrum of the source to be determined despite the distortions introduced by the window function. The best estimate for the period is 12,132 +/- 3 s, where the error is that derived from simulations. An upper limit to the rate of change of period of about 10 exp -9 is inferred if the light curves are truly phase-coherent, but as this is not required by the data, the conservative upper limit is not greater than 5 x 10 exp -7. The large amount of power in the periodic component and its stability both suggest occultation of the source as its origin.

  18. The Spectrum of 1ES0229 + 200 and the Cosmic Infrared Background

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Scully, S. T.

    2008-01-01

    Aims. We reexamine the implications of the recent HESS observations of the blazar 1ES0229+200 for constraining the extragalactic mid-infrared background radiation. Methods. We examine the effect of gamma-ray absorption by the extragalactic infrared radiation on predicted intrinsic spectra for this blazar and compare our results with the observational data. Results. We find agreement with our previous results on the shape of the infrared spectral energy distribution, contrary to the recent assertion of the HESS group. Our analysis indicates that 1ES0229+200 has a very hard intrinsic spectrum with a spectral index between 1.1 +/- 0.3 and 1.5 0.3 in the energy range between 0.5 TeV and 15 TeV. Conclusions. Under the assumptions that (1) the models of Stecker et al. as derived from numerous detailed infrared observations are reasonable, and (2) spectral indexes in the range 1 < Gamma < 1.5 are obtainable from relativistic shock acceleration under the astrophysical conditions extant in blazar flares, the fits to the observations of 1ES0229+200 using our previous infrared spectral energy distributions are consistent with both the infrared and -ray observations. Our analysis presents evidence indicating that the energy spectrum of relativistic particles in 1ES0229+200 is produced by relativistic shock acceleration, producing an intrinsic gamma-ray spectrum with index 1 < Gamma < 1.5 and with no evidence of a peak in the spectral energy distribution up to energies approximately 15 TeV.

  19. Do clusters of galaxies affect the spectrum of the microwave background?

    NASA Technical Reports Server (NTRS)

    Markevitch, M.; Blumenthal, G. R.; Forman, W.; Jones, C.; Suniaev, R. A.

    1991-01-01

    The distortion, averaged over the sky, due to the Compton scattering of background photons with electrons in the hot gas in clusters of galaxies is calculated. Using an existing sample of X-ray clusters, various values of the density parameter Omega, and plausible models for cluster evolution, Monte Carlo realizations of the microwave sky are generated. The spatial structure of these simulations shows a network of discrete sources whose properties can be a strong function of both evolution and Omega. The amount of spectral distortion in the models is greatest for models characterized by self-similar cluster evolution in an open universe and is within an order of magnitude of the current upper limits. Thus, improved observational sensitivity must inevitably detect some deviation from a blackbody spectrum.

  20. A high resolution spectrum of the diffuse soft X-ray background

    NASA Astrophysics Data System (ADS)

    Crowder, S. Gwynne

    Galactic contributions to the diffuse X-ray background were believed to largely come from thermal emission of hot gas and models of the Galactic neighborhood within ˜ 100 pc reflected this belief. However, recent observations led to the realization that emission from charge exchange within the Solar System might produce comparable intensities to that of thermal emission. A high resolution spectrum of the diffuse X-ray background from 0.1 to 1 keV was obtained for a ˜ 1 sr region of the sky centered at l = 90°, b = +60° in May 2008 using a 36 pixel array of microcalorimeters flown on a sounding rocket. With an energy resolution of 11 eV FWHM below 1 keV, the spectrum can be used to separate charge exchange contributions originating within the heliosphere from thermal emission of hot gas in the interstellar medium. The X-ray sensitivity below 1 keV was reduced about a factor of four by contamination that occurred early in the flight, limiting the significance of the results. The observed ratio of helium-like O VII forbidden plus intercombination to resonance lines is 1.2 +/- 1.2 at 90% confidence. This indicates that at least 67% of the emission is thermal. On the other hand, the observed ratio of C VI Lygamma to Lyalpha is 0.3+0.3-0.2 , requiring at least a 33% contribution from charge exchange. In addition to these astrophysical results, I present experimental improvements from the addition of a gold coating to the detector array substrate which greatly reduces extraneous signals and from the use of silicon support meshes which improves blocking filter robustness. I also detail a new optimal filtering analysis technique that preserves spectral resolution and live time in the presence of pulse overlap.

  1. Joint resonant CMB power spectrum and bispectrum estimation

    NASA Astrophysics Data System (ADS)

    Meerburg, P. Daniel; Münchmeyer, Moritz; Wandelt, Benjamin

    2016-02-01

    We develop the tools necessary to assess the statistical significance of resonant features in the CMB correlation functions, combining power spectrum and bispectrum measurements. This significance is typically addressed by running a large number of simulations to derive the probability density function (PDF) of the feature-amplitude in the Gaussian case. Although these simulations are tractable for the power spectrum, for the bispectrum they require significant computational resources. We show that, by assuming that the PDF is given by a multivariate Gaussian where the covariance is determined by the Fisher matrix of the sine and cosine terms, we can efficiently produce spectra that are statistically close to those derived from full simulations. By drawing a large number of spectra from this PDF, both for the power spectrum and the bispectrum, we can quickly determine the statistical significance of candidate signatures in the CMB, considering both single frequency and multifrequency estimators. We show that for resonance models, cosmology and foreground parameters have little influence on the estimated amplitude, which allows us to simplify the analysis considerably. A more precise likelihood treatment can then be applied to candidate signatures only. We also discuss a modal expansion approach for the power spectrum, aimed at quickly scanning through large families of oscillating models.

  2. Cosmic Emulation: Fast Predictions for the Galaxy Power Spectrum

    NASA Astrophysics Data System (ADS)

    Kwan, Juliana; Heitmann, Katrin; Habib, Salman; Padmanabhan, Nikhil; Lawrence, Earl; Finkel, Hal; Frontiere, Nicholas; Pope, Adrian

    2015-09-01

    The halo occupation distribution (HOD) approach has proven to be an effective method for modeling galaxy clustering and bias. In this approach, galaxies of a given type are probabilistically assigned to individual halos in N-body simulations. In this paper, we present a fast emulator for predicting the fully nonlinear galaxy-galaxy auto and galaxy-dark matter cross power spectrum and correlation function over a range of freely specifiable HOD modeling parameters. The emulator is constructed using results from 100 HOD models run on a large ΛCDM N-body simulation, with Gaussian Process interpolation applied to a PCA-based representation of the galaxy power spectrum. The total error is currently ˜1% in the auto correlations and ˜2% in the cross correlations from z = 1 to z = 0, over the considered parameter range. We use the emulator to investigate the accuracy of various analytic prescriptions for the galaxy power spectrum, parametric dependencies in the HOD model, and the behavior of galaxy bias as a function of HOD parameters. Additionally, we obtain fully nonlinear predictions for tangential shear correlations induced by galaxy-galaxy lensing from our galaxy-dark matter cross power spectrum emulator. All emulation products are publicly available at http://www.hep.anl.gov/cosmology/CosmicEmu/emu.html.

  3. Galactic antiproton spectrum at high energies: Background expectation versus exotic contributions

    SciTech Connect

    Bringmann, Torsten; Salati, Pierre

    2007-04-15

    A new generation of upcoming space-based experiments will soon start to probe the spectrum of cosmic-ray antiparticles with an unprecedented accuracy and, in particular, will open up a window to energies much higher than those accessible so far. It is thus timely to carefully investigate the expected antiparticle fluxes at high energies. Here, we perform such an analysis for the case of antiprotons. We consider both standard sources as the collision of other cosmic rays with interstellar matter, as well as exotic contributions from dark matter annihilations in the galactic halo. Up to energies well above 100 GeV, we find that the background flux in antiprotons is almost uniquely determined by the existing low-energy data on various cosmic-ray species; for even higher energies, however, the uncertainties in the parameters of the underlying propagation model eventually become significant. We also show that if the dark matter is composed of particles with masses at the TeV scale, which is naturally expected in extra-dimensional models as well as in certain parameter regions of supersymmetric models, the annihilation flux can become comparable to--or even dominate--the antiproton background at the high energies considered here.

  4. The very low frequency power spectrum of Centaurus X-3

    NASA Technical Reports Server (NTRS)

    Gruber, D. E.

    1988-01-01

    The long-term variability of Cen X-3 on time scales ranging from days to years has been examined by combining data obtained by the HEAO 1 A-4 instrument with data from Vela 5B. A simple interpretation of the data is made in terms of the standard alpha-disk model of accretion disk structure and dynamics. Assuming that the low-frequency variance represents the inherent variability of the mass transfer from the companion, the decline in power at higher frequencies results from the leveling of radial structure in the accretion disk through viscous mixing. The shape of the observed power spectrum is shown to be in excellent agreement with a calculation based on a simplified form of this model. The observed low-frequency power spectrum of Cen X-3 is consistent with a disk in which viscous mixing occurs about as rapidly as possible and on the largest scale possible.

  5. Primordial scalar power spectrum from the Euclidean big bounce

    NASA Astrophysics Data System (ADS)

    Schander, Susanne; Barrau, Aurélien; Bolliet, Boris; Linsefors, Linda; Mielczarek, Jakub; Grain, Julien

    2016-01-01

    In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of a Euclidean phase accompanying the nonsingular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power leading to results incompatible with the data.

  6. Multiredshift Limits on the 21 cm Power Spectrum from PAPER

    NASA Astrophysics Data System (ADS)

    Jacobs, Daniel C.; Pober, Jonathan C.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki S.; Bowman, Judd; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Dexter, Matthew R.; Gugliucci, Nicole E.; Klima, Pat; Liu, Adrian; MacMahon, David H. E.; Manley, Jason R.; Moore, David F.; Stefan, Irina I.; Walbrugh, William P.

    2015-03-01

    The epoch of the reionization (EoR) power spectrum is expected to evolve strongly with redshift, and it is this variation with cosmic history that will allow us to begin to place constraints on the physics of reionization. The primary obstacle to the measurement of the EoR power spectrum is bright foreground emission. We present an analysis of observations from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) telescope, which place new limits on the H i power spectrum over the redshift range of 7.5\\lt z\\lt 10.5, extending previously published single-redshift results to cover the full range accessible to the instrument. To suppress foregrounds, we use filtering techniques that take advantage of the large instrumental bandwidth to isolate and suppress foreground leakage into the interesting regions of k-space. Our 500 hr integration is the longest such yet recorded and demonstrates this method to a dynamic range of 104. Power spectra at different points across the redshift range reveal the variable efficacy of the foreground isolation. Noise-limited measurements of Δ2 at k = 0.2 hr Mpc-1 and z = 7.55 reach as low as (48 mK)2 (1σ). We demonstrate that the size of the error bars in our power spectrum measurement as generated by a bootstrap method is consistent with the fluctuations due to thermal noise. Relative to this thermal noise, most spectra exhibit an excess of power at a few sigma. The likely sources of this excess include residual foreground leakage, particularly at the highest redshift, unflagged radio frequency interference, and calibration errors. We conclude by discussing data reduction improvements that promise to remove much of this excess.

  7. Thermal power spectrum in the CFT driven cosmology

    SciTech Connect

    Barvinsky, A.O.

    2013-10-01

    We present an overview of the recently suggested cosmological model driven by conformal field theory (CFT) with the initial conditions in the form of the microcanonical density matrix. In particular, we discuss the origin of inflationary stage in this model and a novel feature — the thermal nature of the primordial power spectrum of the CMB anisotropy. The relevant effect of ''temperature of the relic temperature anisotropy'' can be responsible for a thermal contribution to the red tilt of this spectrum, additional to its conventional vacuum component. The amplification of this effect due to recently established a-theorem in CFT is briefly discussed.

  8. On syntheses of the X-ray background with power-law sources

    NASA Technical Reports Server (NTRS)

    De Zotti, G.; Boldt, E. A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.; Cavaliere, A.; Danese, L.; Franceschini, A.

    1982-01-01

    The conditions under which the combined emission from power-law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low-luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit steeper spectra at higher energies.

  9. On syntheses of the X-ray background with power-law sources

    NASA Technical Reports Server (NTRS)

    Dezotti, G.; Boldt, E. A.; Cavaliere, A.; Danese, L.; Franceschini, A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.

    1981-01-01

    The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

  10. On syntheses of the X-ray background with power-law sources

    NASA Astrophysics Data System (ADS)

    De Zotti, G.; Boldt, E. A.; Cavaliere, A.; Danese, L.; Franceschini, A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.

    1981-08-01

    The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

  11. Decomposition of Heart Rate Variability Spectrum into a Power-Law Function and a Residual Spectrum

    PubMed Central

    Kuo, Jane; Kuo, Cheng-Deng

    2016-01-01

    The power spectral density (PSD) of heart rate variability (HRV) contains a power-law relationship that can be obtained by plotting the logarithm of PSD against the logarithm of frequency. The PSD of HRV can be decomposed mathematically into a power-law function and a residual HRV (rHRV) spectrum. Almost all rHRV measures are significantly smaller than their corresponding HRV measures except the normalized high-frequency power (nrHFP). The power-law function can be characterized by the slope and Y-intercept of linear regression. Almost all HRV measures except the normalized low-frequency power have significant correlations with the Y-intercept, while almost all rHRV measures except the total power [residual total power (rTP)] do not. Though some rHRV measures still correlate significantly with the age of the subjects, the rTP, high-frequency power (rHFP), nrHFP, and low-/high-frequency power ratio (rLHR) do not. In conclusion, the clinical significances of rHRV measures might be different from those of traditional HRV measures. The Y-intercept might be a better HRV measure for clinical use because it is independent of almost all rHRV measures. The rTP, rHFP, nrHFP, and rLHR might be more suitable for the study of age-independent autonomic nervous modulation of the subjects. PMID:27314001

  12. The Atacama Cosmology Telescope: Temperature and Gravitational Lensing Power Spectrum Measurements from Three Seasons of Data

    NASA Technical Reports Server (NTRS)

    Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battisetti, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon; Dunkley, Joanna; Dunner, Rolando; Fowler, Joseph W.; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent D; Kosowsky, Arthur; Wollack, Ed

    2014-01-01

    We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ?CDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6s detection significance.

  13. The Atacama Cosmology Telescope: temperature and gravitational lensing power spectrum measurements from three seasons of data

    NASA Astrophysics Data System (ADS)

    Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battistelli, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon; Dunkley, Joanna; Dünner, Rolando; Fowler, Joseph W.; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renée; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent D.; Kosowsky, Arthur; Lupton, Robert H.; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Reese, Erik D.; Schmitt, Benjamin L.; Sehgal, Neelima; Sherwin, Blake D.; Sievers, Jonathan L.; Spergel, David N.; Staggs, Suzanne T.; Swetz, Daniel S.; Switzer, Eric R.; Thornton, Robert; Trac, Hy; Wollack, Ed

    2014-04-01

    We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ΛCDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6σ detection significance.

  14. Automated FMV image quality assessment based on power spectrum statistics

    NASA Astrophysics Data System (ADS)

    Kalukin, Andrew

    2015-05-01

    Factors that degrade image quality in video and other sensor collections, such as noise, blurring, and poor resolution, also affect the spatial power spectrum of imagery. Prior research in human vision and image science from the last few decades has shown that the image power spectrum can be useful for assessing the quality of static images. The research in this article explores the possibility of using the image power spectrum to automatically evaluate full-motion video (FMV) imagery frame by frame. This procedure makes it possible to identify anomalous images and scene changes, and to keep track of gradual changes in quality as collection progresses. This article will describe a method to apply power spectral image quality metrics for images subjected to simulated blurring, blocking, and noise. As a preliminary test on videos from multiple sources, image quality measurements for image frames from 185 videos are compared to analyst ratings based on ground sampling distance. The goal of the research is to develop an automated system for tracking image quality during real-time collection, and to assign ratings to video clips for long-term storage, calibrated to standards such as the National Imagery Interpretability Rating System (NIIRS).

  15. Rejuvenating the Matter Power Spectrum. III. The Cosmology Sensitivity of Gaussianized Power Spectra

    NASA Astrophysics Data System (ADS)

    Neyrinck, Mark C.

    2011-12-01

    It was recently shown that applying a Gaussianizing transform, such as a logarithm, to the nonlinear matter density field extends the range of useful applicability of the power spectrum by a factor of a few smaller. Such a transform dramatically reduces nonlinearities in both the covariance and the shape of the power spectrum. Here, analyzing Coyote Universe real-space dark-matter density fields, we investigate the consequences of these transforms for cosmological parameter estimation. The power spectrum of the log-density provides the tightest cosmological parameter error bars (marginalized or not), giving a factor of 2-3 improvement over the conventional power spectrum in all five parameters tested. For the tilt, ns , the improvement reaches a factor of five. Similar constraints are achieved if the log-density power spectrum and conventional power spectrum are analyzed together. Rank-order Gaussianization seems just as useful as a log transform to constrain ns , but not other parameters. Dividing the overdensity by its dispersion in few-Mpc cells, while it diagonalizes the covariance matrix, does not seem to help with parameter constraints. We also provide a code that emulates these power spectra over a range of concordance cosmological models.

  16. REJUVENATING THE MATTER POWER SPECTRUM. III. THE COSMOLOGY SENSITIVITY OF GAUSSIANIZED POWER SPECTRA

    SciTech Connect

    Neyrinck, Mark C.

    2011-12-01

    It was recently shown that applying a Gaussianizing transform, such as a logarithm, to the nonlinear matter density field extends the range of useful applicability of the power spectrum by a factor of a few smaller. Such a transform dramatically reduces nonlinearities in both the covariance and the shape of the power spectrum. Here, analyzing Coyote Universe real-space dark-matter density fields, we investigate the consequences of these transforms for cosmological parameter estimation. The power spectrum of the log-density provides the tightest cosmological parameter error bars (marginalized or not), giving a factor of 2-3 improvement over the conventional power spectrum in all five parameters tested. For the tilt, n{sub s} , the improvement reaches a factor of five. Similar constraints are achieved if the log-density power spectrum and conventional power spectrum are analyzed together. Rank-order Gaussianization seems just as useful as a log transform to constrain n{sub s} , but not other parameters. Dividing the overdensity by its dispersion in few-Mpc cells, while it diagonalizes the covariance matrix, does not seem to help with parameter constraints. We also provide a code that emulates these power spectra over a range of concordance cosmological models.

  17. COSMIC MICROWAVE BACKGROUND POLARIZATION AND TEMPERATURE POWER SPECTRA ESTIMATION USING LINEAR COMBINATION OF WMAP 5 YEAR MAPS

    SciTech Connect

    Samal, Pramoda Kumar; Jain, Pankaj; Saha, Rajib; Prunet, Simon; Souradeep, Tarun

    2010-05-01

    We estimate cosmic microwave background (CMB) polarization and temperature power spectra using Wilkinson Microwave Anisotropy Probe (WMAP) 5 year foreground contaminated maps. The power spectrum is estimated by using a model-independent method, which does not utilize directly the diffuse foreground templates nor the detector noise model. The method essentially consists of two steps: (1) removal of diffuse foregrounds contamination by making linear combination of individual maps in harmonic space and (2) cross-correlation of foreground cleaned maps to minimize detector noise bias. For the temperature power spectrum we also estimate and subtract residual unresolved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our TT, TE, and EE power spectra are in good agreement with the published results of the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We find that the bias is small in almost all cases. A negative bias at low l in TT power spectrum has been pointed out in an earlier publication. We find that the bias-corrected quadrupole power (l(l + 1)C{sub l} /2{pi}) is 532 {mu}K{sup 2}, approximately 2.5 times the estimate (213.4 {mu}K{sup 2}) made by the WMAP team.

  18. Electron density power spectrum in the local interstellar medium

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.; Rickett, B. J.; Spangler, S. R.

    1995-01-01

    Interstellar scintillation (ISS), fluctuations in the amplitude and phase of radio waves caused by scattering in the interstellar medium, is important as a diagnostic of interstellar plasma turbulence. ISS is also of interest because it is noise for other radio astronomical observations. The unifying concern is the power spectrum of the interstellar electron density. Here we use ISS observations through the nearby (less than or approximately =1 kpc) (ISM) to estimate the spectrum. From measurements of angular broadening of pulsars and extragalactic sources, decorrelation bandwidth of pulsars, refractive steering of features in pulsar dynamic spectra, dispersion measured fluctuations of pulsars, and refractive scintillation index measurements, we construct a composite structure function that is approximately power law over 2 x 10(exp 6) m less than scale less than 10(exp 13) m. The data are consistent with the structure function having a logarithmic slope versus baseline less than 2; thus there is a meaningful connection between scales in the radiowave fluctuation field and the scales in the electron density field causing the scattering. The data give an upper limit to the inner scale, l(sub o) less than or approximately 10(exp 8) m and are consistent with much smaller values. We construct a composite electron density spectrum that is approximately power law over at least the approximately = 5 decade wavenumber range 10(exp -13)/m less than wavenumber less than 10(exp -8)/m and that may extend to higher wavenumbers. The average spectral index of electron density over this wavenumber range is approximately = 3.7, very close to the value expected for a Kolmogorov process. The outer scale size, L(sub o), must be greater than or approximately = 10(exp 13) m (determined from dispersion measure fluctuations). When the ISS data are combined with measurements of differential Faraday rotation angle, and gradients in the average electron density, constraints can be put on the

  19. 21 cm Power Spectrum Upper Limits from PAPER-64

    NASA Astrophysics Data System (ADS)

    Shiraz Ali, Zaki; Parsons, Aaron; Pober, Jonathan; Team PAPER

    2016-01-01

    We present power spectrum results from the 64 antenna deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER-64). We find an upper limit of Δ2≤(22.4 mK)2 over the range 0.15power spectrum constraints to date. In addition, we use these results to place lower limits on the spin temperature at a redshift of 8.4. We find that the spin temperature is at least 10K for a neutral fraction between 15% and 80%. This further suggests that there was heating in the early universe through various sources such as x-ray binaries.

  20. Normalized Noise Power Spectrum of Full Field Digital Mammography System

    SciTech Connect

    Isa, Norriza Mohd; Wan Hassan, Wan Muhamad Saridan

    2010-01-05

    A method to measure noise power spectrum of a full field digital mammography system is presented. The effect of X-ray radiation dose, size and configuration of region of interest on normalized noise power spectrum (NNPS) was investigated. Flat field images were acquired using RQA-M2 beam quality technique (Mo/Mo anode-filter, 28 kV, 2 mm Al) with different clinical radiation doses. The images were cropped at about 4 cm from the edge of the breast wall and then divided into different size of non-overlapping or overlapping segments. NNPS was determined through detrending, 2-D fast Fourier transformation and normalization. Our measurement shows that high radiation dose gave lower NNPS at a specific beam quality.

  1. Nonisotropy in the CMB power spectrum in single field inflation

    SciTech Connect

    Donoghue, John F.; Dutta, Koushik; Ross, Andreas

    2009-07-15

    Contaldi et al.[C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys. 07 (2003) 002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of l. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low l.

  2. Measurement of primordial non-Gaussianity using the WMAP 5-year temperature skewness power spectrum

    SciTech Connect

    Smidt, Joseph; Amblard, Alexandre; Serra, Paolo; Cooray, Asantha

    2009-12-15

    We constrain the primordial non-Gaussianity parameter of the local model f{sub NL} using the skewness power spectrum associated with the two-to-one cumulant correlator of cosmic microwave background temperature anisotropies. This bispectrum-related power spectrum was constructed after weighting the temperature map with the appropriate window functions to form an estimator that probes the multipolar dependence of the underlying bispectrum associated with the primordial non-Gaussianity. We also estimate a separate skewness power spectrum sensitive more strongly to unresolved point sources. When compared to previous attempts at measuring the primordial non-Gaussianity with WMAP data, our estimators have the main advantage that we do not collapse information to a single number. When model fitting the two-to-one skewness power spectrum, we make use of bispectra generated by the primordial non-Gaussianity, radio point sources, and lensing-secondary correlation. We analyze Q, V, and W-band WMAP 5-year data using the KQ75 mask out to l{sub max}=600. Using V and W-band data and marginalizing over model parameters related to point sources and lensing-secondary bispectrum, our overall and preferred constraint on f{sub NL} is 11.0{+-}23.7 at the 68% confidence level (-36.4

  3. Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach

    NASA Astrophysics Data System (ADS)

    Perico, E. L. D.; Bernardini, A. E.

    2011-06-01

    Modifications on the predictions about the matter power spectrum based on the hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid to some dominant cosmological scenario are investigated. Reporting about the systematic way of accounting for all the cosmological perturbations, through the Boltzmann equation we obtain the analytical results for density fluctuation, δ, and fluid velocity divergence, θ, of the DFG. Small contributions to the matter power spectrum are analytically obtained for the radiation-dominated background, through an ultra-relativistic approximation, and for the matter-dominated and Λ-dominated eras, through a non-relativistic approximation. The results can be numerically reproduced and compared with those of considering non-relativistic and ultra-relativistic neutrinos into the computation of the matter power spectrum. Lessons concerning the formation of large scale structures of a DFG are depicted, and consequent deviations from standard ΛCDM predictions for the matter power spectrum (with and without neutrinos) are quantified.

  4. REVISING THE HALOFIT MODEL FOR THE NONLINEAR MATTER POWER SPECTRUM

    SciTech Connect

    Takahashi, Ryuichi; Sato, Masanori; Nishimichi, Takahiro; Taruya, Atsushi; Oguri, Masamune

    2012-12-20

    Based on a suite of state-of-the-art high-resolution N-body simulations, we revisit the so-called halofit model as an accurate fitting formula for the nonlinear matter power spectrum. While the halofit model has frequently been used as a standard cosmological tool to predict the nonlinear matter power spectrum in a universe dominated by cold dark matter, its precision has been limited by the low resolution of N-body simulations used to determine the fitting parameters, suggesting the necessity of an improved fitting formula at small scales for future cosmological studies. We run high-resolution N-body simulations for 16 cosmological models around the Wilkinson Microwave Anisotropy Probe best-fit cosmological parameters (one-, three-, five-, and seven-year results), including dark energy models with a constant equation of state. The simulation results are used to re-calibrate the fitting parameters of the halofit model so as to reproduce small-scale power spectra of the N-body simulations, while keeping the precision at large scales. The revised fitting formula provides an accurate prediction of the nonlinear matter power spectrum in a wide range of wavenumbers (k {<=} 30 h Mpc{sup -1}) at redshifts 0 {<=} z {<=} 10, with 5% precision for k {<=} 1 h Mpc{sup -1} at 0 {<=} z {<=} 10 and 10% for 1 {<=} k {<=} 10 h Mpc{sup -1} at 0 {<=} z {<=} 3. We discuss the impact of the improved halofit model on weak-lensing power spectra and correlation functions, and show that the improved model better reproduces ray-tracing simulation results.

  5. Gamma-ray Background Spectrum and Annihilation Rate in the Baryon-symmetric Big-bang Cosmology

    NASA Technical Reports Server (NTRS)

    Puget, J. L.

    1973-01-01

    An attempt was made to acquire experimental information on the problem of baryon symmetry on a large cosmological scale by observing the annihilation products. Data cover absorption cross sections and background radiation due to other sources for the two main products of annihilation, gamma rays and neutrinos. Test results show that the best direct experimental test for the presence of large scale antimatter lies in the gamma ray background spectrum between 1 and 70 MeV.

  6. CHIPS: The Cosmological H i Power Spectrum Estimator

    NASA Astrophysics Data System (ADS)

    Trott, C. M.; Pindor, B.; Procopio, P.; Wayth, R. B.; Mitchell, D. A.; McKinley, B.; Tingay, S. J.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; de Oliveira-Costa, A.; Dillon, Joshua S.; Ewall-Wice, A.; Feng, L.; Greenhill, L. J.; Hazelton, B. J.; Hewitt, J. N.; Hurley-Walker, N.; Johnston-Hollitt, M.; Jacobs, Daniel C.; Kaplan, D. L.; Kim, H. S.; Lenc, E.; Line, J.; Loeb, A.; Lonsdale, C. J.; Morales, M. F.; Morgan, E.; Neben, A. R.; Thyagarajan, Nithyanandan; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Paul, S.; Pober, J. C.; Prabu, T.; Riding, J.; Udaya Shankar, N.; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Sullivan, I. S.; Tegmark, M.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-02-01

    Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization (EoR) and estimation of its basic physical parameters are principal scientific aims of many current low-frequency radio telescopes. Here we describe the Cosmological H i Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array, to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximizing the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation (“foreground suppression”). We describe the motivation for the algorithm, implementation, application to real and simulated data, and early outputs. Upon application to a set of 3 hr of data, we set a 2σ upper limit on the EoR dimensionless power at k=0.05 {{h}} Mpc-1 of {{{Δ }}}k2\\lt 7.6× {10}4 mK2 in the redshift range z = [6.2-6.6], consistent with previous estimates.

  7. Influence of DBT reconstruction algorithm on power law spectrum coefficient

    NASA Astrophysics Data System (ADS)

    Vancamberg, Laurence; Carton, Ann-Katherine; Abderrahmane, Ilyes H.; Palma, Giovanni; Milioni de Carvalho, Pablo; Iordache, Rǎzvan; Muller, Serge

    2015-03-01

    In breast X-ray images, texture has been characterized by a noise power spectrum (NPS) that has an inverse power-law shape described by its slope β in the log-log domain. It has been suggested that the magnitude of the power-law spectrum coefficient β is related to mass lesion detection performance. We assessed β in reconstructed digital breast tomosynthesis (DBT) images to evaluate its sensitivity to different typical reconstruction algorithms including simple back projection (SBP), filtered back projection (FBP) and a simultaneous iterative reconstruction algorithm (SIRT 30 iterations). Results were further compared to the β coefficient estimated from 2D central DBT projections. The calculations were performed on 31 unilateral clinical DBT data sets and simulated DBT images from 31 anthropomorphic software breast phantoms. Our results show that β highly depends on the reconstruction algorithm; the highest β values were found for SBP, followed by reconstruction with FBP, while the lowest β values were found for SIRT. In contrast to previous studies, we found that β is not always lower in reconstructed DBT slices, compared to 2D projections and this depends on the reconstruction algorithm. All β values estimated in DBT slices reconstructed with SBP were larger than β values from 2D central projections. Our study also shows that the reconstruction algorithm affects the symmetry of the breast texture NPS; the NPS of clinical cases reconstructed with SBP exhibit the highest symmetry, while the NPS of cases reconstructed with SIRT exhibit the highest asymmetry.

  8. Imprint of inhomogeneous and anisotropic primordial power spectrum on CMB polarization

    NASA Astrophysics Data System (ADS)

    Kothari, Rahul; Ghosh, Shamik; Rath, Pranati K.; Kashyap, Gopal; Jain, Pankaj

    2016-08-01

    We consider an inhomogeneous model and independently an anisotropic model of primordial power spectrum in order to describe the observed hemispherical anisotropy in cosmic microwave background radiation (CMBR). This anisotropy can be parametrized in terms of the dipole modulation model of the temperature field. Both the models lead to correlations between spherical harmonic coefficients corresponding to multipoles, l and l ± 1. We obtain the model parameters by making a fit to TT correlations in CMBR data. Using these parameters we predict the signature of our models for correlations among different multipoles for the case of the TE and EE modes. These predictions can be used to test whether the observed hemispherical anisotropy can be correctly described in terms of a primordial power spectrum. Furthermore these may also allow us to distinguish between an inhomogeneous and an anisotropic model.

  9. Imprint of Inhomogeneous and Anisotropic Primordial Power Spectrum on CMB Polarization

    NASA Astrophysics Data System (ADS)

    Kothari, Rahul; Ghosh, Shamik; Rath, Pranati K.; Kashyap, Gopal; Jain, Pankaj

    2016-05-01

    We consider an inhomogeneous model and independently an anisotropic model of primordial power spectrum in order to describe the observed hemispherical anisotropy in Cosmic Microwave Background Radiation. This anisotropy can be parametrized in terms of the dipole modulation model of the temperature field. Both the models lead to correlations between spherical harmonic coefficients corresponding to multipoles, l and l ± 1. We obtain the model parameters by making a fit to TT correlations in CMBR data. Using these parameters we predict the signature of our models for correlations among different multipoles for the case of the TE and EE modes. These predictions can be used to test whether the observed hemispherical anisotropy can be correctly described in terms of a primordial power spectrum. Furthermore these may also allow us to distinguish between an inhomogeneous and an anisotropic model.

  10. Distributed Energy Resources, Power Quality and Reliability - Background

    SciTech Connect

    Schienbein, Lawrence A.; DeSteese, John G.

    2002-01-31

    Power quality [PQ] and power reliability [PR] gained importance in the industrialized world as the pace of installation of sensitive appliances and other electrical loads by utility customers accelerated, beginning in the mid 1980s. Utility-grid-connected customers rapidly discovered that this equipment was increasingly sensitive to various abnormalities in the electricity supply.

  11. IONOSPHERIC POWER-SPECTRUM TOMOGRAPHY IN RADIO INTERFEROMETRY

    SciTech Connect

    Koopmans, L. V. E.

    2010-08-01

    A tomographic method is described to quantify the three-dimensional power spectrum of the ionospheric electron-density fluctuations based on radio-interferometric observations by a two-dimensional planar array. The method is valid for the first-order Born approximation and might be applicable in correcting observed visibilities for phase variations due to the imprint of the full three-dimensional ionosphere. It is shown that the ionospheric electron-density distribution is not the primary structure to model in interferometry, but rather its autocorrelation function or equivalently its power spectrum. An exact mathematical expression is derived that provides the three-dimensional power spectrum of the ionospheric electron-density fluctuations directly from a rescaled scattered intensity field and an incident intensity field convolved with a complex unit phasor that depends on the w-term and is defined on the full sky pupil plane. In the limit of a small field of view, the method reduces to the single phase-screen approximation. Tomographic self-calibration can become important in high-dynamic range observations at low radio frequencies with wide-field antenna interferometers because a three-dimensional ionosphere causes a spatially varying convolution of the sky, whereas a single phase screen results in a spatially invariant convolution. A thick ionosphere can therefore not be approximated by a single phase screen without introducing errors in the calibration process. By applying a Radon projection and the Fourier projection-slice theorem, it is shown that the phase-screen approach in three dimensions is identical to the tomographic method. Finally, we suggest that residual speckle can cause a diffuse intensity halo around sources due to uncorrectable ionospheric phase fluctuations in the short integrations, which could pose a fundamental limit on the dynamic range in long-integration images.

  12. Matter power spectrum and the challenge of percent accuracy

    NASA Astrophysics Data System (ADS)

    Schneider, Aurel; Teyssier, Romain; Potter, Doug; Stadel, Joachim; Onions, Julian; Reed, Darren S.; Smith, Robert E.; Springel, Volker; Pearce, Frazer R.; Scoccimarro, Roman

    2016-04-01

    Future galaxy surveys require one percent precision in the theoretical knowledge of the power spectrum over a large range including very nonlinear scales. While this level of accuracy is easily obtained in the linear regime with perturbation theory, it represents a serious challenge for small scales where numerical simulations are required. In this paper we quantify the precision of present-day N-body methods, identifying main potential error sources from the set-up of initial conditions to the measurement of the final power spectrum. We directly compare three widely used N-body codes, Ramses, Pkdgrav3, and Gadget3 which represent three main discretisation techniques: the particle-mesh method, the tree method, and a hybrid combination of the two. For standard run parameters, the codes agree to within one percent at k<=1 h Mpc‑1 and to within three percent at k<=10 h Mpc‑1. We also consider the bispectrum and show that the reduced bispectra agree at the sub-percent level for k<= 2 h Mpc‑1. In a second step, we quantify potential errors due to initial conditions, box size, and resolution using an extended suite of simulations performed with our fastest code Pkdgrav3. We demonstrate that the simulation box size should not be smaller than L=0.5 h‑1Gpc to avoid systematic finite-volume effects (while much larger boxes are required to beat down the statistical sample variance). Furthermore, a maximum particle mass of Mp=109 h‑1Msolar is required to conservatively obtain one percent precision of the matter power spectrum. As a consequence, numerical simulations covering large survey volumes of upcoming missions such as DES, LSST, and Euclid will need more than a trillion particles to reproduce clustering properties at the targeted accuracy.

  13. Constraints on massive neutrinos from the CFHTLS angular power spectrum

    SciTech Connect

    Xia, Jun-Qing; Granett, Benjamin R.; Guzzo, Luigi; Viel, Matteo; Bird, Simeon; Haehnelt, Martin G.; Coupon, Jean; McCracken, Henry Joy; Mellier, Yannick E-mail: ben.granett@brera.inaf.it E-mail: spb@ias.edu E-mail: haehnelt@ast.cam.ac.uk E-mail: hjmcc@iap.fr

    2012-06-01

    We use the galaxy angular power spectrum at z ∼ 0.5–1.2 from the Canada-France-Hawaii-Telescope Legacy Survey Wide fields (CFHTLS-Wide) to constrain separately the total neutrino mass Σm{sub ν} and the effective number of neutrino species N{sub eff}. This survey has recently benefited from an accurate calibration of the redshift distribution, allowing new measurements of the (non-linear) matter power spectrum in a unique range of scales and redshifts sensitive to neutrino free streaming. Our analysis makes use of a recent model for the effect of neutrinos on the weakly non-linear matter power spectrum derived from accurate N-body simulations. We show that CFHTLS, combined with WMAP7 and a prior on the Hubble constant provides an upper limit of Σm{sub ν} < 0.29 eV and N{sub eff} = 4.17{sup +1.62}{sub −1.26} (2 σ confidence levels). If we omit smaller scales which may be affected by non-linearities, these constraints become Σm{sub ν} < 0.41 eV and N{sub eff} = 3.98{sup +2.02}{sub −1.20} (2 σ confidence levels). Finally we show that the addition of other large scale structures probes can further improve these constraints, demonstrating that high redshift large volumes surveys such as CFHTLS are complementary to other cosmological probes of the neutrino mass.

  14. HMcode: Halo-model matter power spectrum computation

    NASA Astrophysics Data System (ADS)

    Mead, Alexander

    2015-08-01

    HMcode computes the halo-model matter power spectrum. It is written in Fortran90 and has been designed to quickly (~0.5s for 200 k-values across 16 redshifts on a single core) produce matter spectra for a wide range of cosmological models. In testing it was shown to match spectra produced by the 'Coyote Emulator' to an accuracy of 5 per cent for k less than 10h Mpc^-1. However, it can also produce spectra well outside of the parameter space of the emulator.

  15. Ultrasonic Inspection With Angular-Power-Spectrum Scanning

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R.

    1994-01-01

    Principal advantage of angular-power-spectrum scanning (APSS) is that, unlike x-radiography and prior ultrasonic techniques, it reveals subtle distributions of microstructural features; e.g., variations in densities of micropores or regions in which fibers and matrices are poorly bonded to each other. Potential applications include development and characterization of composite-material components of large structures, such as buildings and bridges; determination of quality and detection of damage in fiberglass hulls, surfboards, ladders, and scaffolds; and development of porous prosthetic skins and complicated "smart" materials. Superposed diffraction patterns give clues to internal structural features of ceramic composites.

  16. Spectrum of power laws for curved hand movements

    PubMed Central

    Huh, Dongsung; Sejnowski, Terrence J.

    2015-01-01

    In a planar free-hand drawing of an ellipse, the speed of movement is proportional to the −1/3 power of the local curvature, which is widely thought to hold for general curved shapes. We investigated this phenomenon for general curved hand movements by analyzing an optimal control model that maximizes a smoothness cost and exhibits the −1/3 power for ellipses. For the analysis, we introduced a new representation for curved movements based on a moving reference frame and a dimensionless angle coordinate that revealed scale-invariant features of curved movements. The analysis confirmed the power law for drawing ellipses but also predicted a spectrum of power laws with exponents ranging between 0 and −2/3 for simple movements that can be characterized by a single angular frequency. Moreover, it predicted mixtures of power laws for more complex, multifrequency movements that were confirmed with human drawing experiments. The speed profiles of arbitrary doodling movements that exhibit broadband curvature profiles were accurately predicted as well. These findings have implications for motor planning and predict that movements only depend on one radian of angle coordinate in the past and only need to be planned one radian ahead. PMID:26150514

  17. Peaks in the CMBR Power Spectrum II: Physical Interpretation for any Cosmological Scenario

    NASA Astrophysics Data System (ADS)

    López-Corredoira, Martín

    2013-06-01

    In a previous paper (part I), the mathematical properties of the cosmic microwave background radiation (CMBR) power spectrum which presents oscillations were discussed. Here, we discuss the physical interpretation: a power spectrum with oscillations is a rather normal characteristic expected from any fluid with clouds of overdensities that emit/absorb radiation or interact gravitationally with the photons, and with a finite range of sizes and distances for those clouds. The standard cosmological interpretation of "acoustic" peaks is just a particular case; peaks in the power spectrum might be generated in scenarios within some alternative cosmological model that have nothing to do with oscillations due to gravitational compression in a fluid. We also calculate the angular correlation function of the anisotropies from the Wilkinson Microwave Anisotropy Probe (WMAP)-7 yr and ACT data, in an attempt to derive the minimum number of parameters a polynomial function should have to fit it: a set of polynomial functions with a total of ≈ 6 free parameters, apart from the amplitude, is enough to reproduce the first two peaks. However, the standard model with six tunable free parameters also reproduces higher-order peaks, giving the standard model a higher confidence. At present, while no simple function with six free parameters is found to give a fit as good as the one given by the standard cosmological model, we may consider the predictive power of the standard model beyond an instrumentalist approach (such as the Ptolemaic astronomy model of the orbits of the planets).

  18. Effective field theory during inflation. II. Stochastic dynamics and power spectrum suppression

    NASA Astrophysics Data System (ADS)

    Boyanovsky, D.

    2016-02-01

    We obtain the nonequilibrium effective action of an inflatonlike scalar field—the system—by tracing over sub-Hubble degrees of freedom of "environmental" light scalar fields. The effective action is stochastic leading to effective Langevin equations of motion for the fluctuations of the inflatonlike field, with self-energy corrections and stochastic noise correlators that obey a de Sitter space-time analog of a fluctuation dissipation relation. We solve the Langevin equation implementing a dynamical renormalization group resummation of the leading secular terms and obtain the corrections to the power spectrum of super-Hubble fluctuations of the inflaton field, P (k ;η )=P0(k )e-γ (k ;η ) where P0(k ) is the nearly scale invariant power spectrum in absence of coupling. γ (k ;η )>0 describes the suppression of the power spectrum; it features Sudakov-type double logarithms and entails violations of scale invariance. We also obtain the effective action for the case of a heavy scalar field of mass M ≫H ; this case yields a local "Fermi" limit with a very weak self-interaction of the inflatonlike field and dissipative terms that are suppressed by powers of H /M . We conjecture on the possibility that the large scale anomalies in the cosmic microwave background may originate in dissipative processes from inflaton coupling to sub-Hubble degrees of freedom.

  19. Nonisotropy in the CMB power spectrum in single field inflation

    NASA Astrophysics Data System (ADS)

    Donoghue, John F.; Dutta, Koushik; Ross, Andreas

    2009-07-01

    Contaldi et al. [C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys.1475-7516 07 (2003) 00210.1088/1475-7516/2003/07/002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of ℓ. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low ℓ.

  20. Power Spectrum Density of Stochastic Oscillating Accretion Disk

    NASA Astrophysics Data System (ADS)

    Long, G. B.; Ou, J. W.; Zheng, Y. G.

    2016-06-01

    In this paper, we employ a stochastic oscillating accretion disk model for the power spectral index and variability of BL Lac object S5 0716+714. In the model, we assume that there is a relativistic oscillation of thin accretion disks and it interacts with an external thermal bath through a friction force and a random force. We simulate the light curve and the power spectrum density (PSD) at (i) over-damped, (ii) critically damped and (iii) under-damped cases, respectively. Our results show that the simulated PSD curves depend on the intrinsic property of the accretion disk, and it could be produced in a wide interval ranging from 0.94 to 2.05 by changing the friction coefficient in a stochastic oscillating accretion disk model. We argue that accretion disk stochastic oscillating could be a possible interpretation for observed PSD variability.

  1. Unbiased contaminant removal for 3D galaxy power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Kalus, B.; Percival, W. J.; Bacon, D. J.; Samushia, L.

    2016-08-01

    We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum, (iii) debiasing the resulting estimates. For (i), we show that removing the best-fit contaminant (mode subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large N_mode^2 matrices (Nmode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants is less severe than that commonly ignored due to the survey window.

  2. Power spectrum for inflation models with quantum and thermal noises

    SciTech Connect

    Ramos, Rudnei O.; Silva, L.A. da E-mail: las.leandro@gmail.com

    2013-03-01

    We determine the power spectrum for inflation models covering all regimes from cold (isentropic) to warm (nonisentropic) inflation. We work in the context of the stochastic inflation approach, which can nicely describe both types of inflationary regimes concomitantly. A throughout analysis is carried out to determine the allowed parameter space for simple single field polynomial chaotic inflation models that is consistent with the most recent cosmological data from the nine-year Wilkinson Microwave Anisotropy Probe (WMAP) and in conjunction with other observational cosmological sources. We present the results for both the amplitude of the power spectrum, the spectral index and for the tensor to scalar curvature perturbation amplitude ratio. We briefly discuss cases when running is present. Despite single field polynomial-type inflaton potential models be strongly disfavored, or even be already ruled out in their simplest versions in the case of cold inflation, this is not the case for nonisentropic inflation models in general (warm inflation in particular), though higher order polynomial potentials (higher than quartic order) tend to become less favorable also in this case, presenting a much smaller region of parameter space compatible with the recent observational cosmological data.

  3. Joint Bayesian Component Separation and CMB Power Spectrum Estimation

    NASA Technical Reports Server (NTRS)

    Eriksen, H. K.; Jewell, J. B.; Dickinson, C.; Banday, A. J.; Gorski, K. M.; Lawrence, C. R.

    2008-01-01

    We describe and implement an exact, flexible, and computationally efficient algorithm for joint component separation and CMB power spectrum estimation, building on a Gibbs sampling framework. Two essential new features are (1) conditional sampling of foreground spectral parameters and (2) joint sampling of all amplitude-type degrees of freedom (e.g., CMB, foreground pixel amplitudes, and global template amplitudes) given spectral parameters. Given a parametric model of the foreground signals, we estimate efficiently and accurately the exact joint foreground- CMB posterior distribution and, therefore, all marginal distributions such as the CMB power spectrum or foreground spectral index posteriors. The main limitation of the current implementation is the requirement of identical beam responses at all frequencies, which restricts the analysis to the lowest resolution of a given experiment. We outline a future generalization to multiresolution observations. To verify the method, we analyze simple models and compare the results to analytical predictions. We then analyze a realistic simulation with properties similar to the 3 yr WMAP data, downgraded to a common resolution of 3 deg FWHM. The results from the actual 3 yr WMAP temperature analysis are presented in a companion Letter.

  4. State regulation and power plant productivity: background and recommendations

    SciTech Connect

    Not Available

    1980-09-01

    This report was prepared by representatives of several state regulatory agencies. It is a guide to some of the activities currently under way in state agencies to promote increased availability of electrical generating power plants. Standard measures of plant performance are defined and the nature of data bases that report such measures is discussed. It includes reviews of current state, federal, and industry programs to enhance power plant productivity and provides detailed outlines of programs in effect in California, Illinois, Michigan, New York, North Carolina, Ohio, and Texas. A number of actions are presented that could be adopted by state regulatory agencies, depending on local conditions. They include: develop a commission position or policy statement to encourage productivity improvements by utilities; coordinate state efforts with ongoing industry and government programs to improve the acquisition of power plant performance data and the maintenance of quality information systems; acquire the capability to perform independent analyses of power plant productivity; direct the establishment of productivity improvement programs, including explicit performance objectives for both existing and planned power plants, and a performance program; establish a program of incentives to motivate productivity improvement activities; and participate in ongoing efforts at all levels and initiate new actions to promote productivity improvements.

  5. Power spectrum sensitivity of raster-scanned CMB experiments in the presence of 1/f noise

    SciTech Connect

    Crawford, Tom

    2007-09-15

    We investigate the effects of 1/f noise on the ability of a particular class of cosmic microwave background experiments to measure the angular power spectrum of temperature anisotropy. We concentrate on experiments that operate primarily in raster-scan mode and develop formalism that allows us to calculate analytically the effect of 1/f noise on power-spectrum sensitivity for this class of experiments and determine the benefits of raster-scanning at different angles relative to the sky field versus scanning at only a single angle (cross-linking versus not cross-linking). We find that the sensitivity of such experiments in the presence of 1/f noise is not significantly degraded at moderate spatial scales (l{approx}100) for reasonable values of scan speed and 1/f knee. We further find that the difference between cross-linked and non-cross-linked experiments is small in all cases and that the non-cross-linked experiments are preferred from a raw sensitivity standpoint in the noise-dominated regime - i.e., in experiments in which the instrument noise is greater than the sample variance of the target power spectrum at the scales of interest. This analysis does not take into account systematic effects.

  6. Violation of statistical isotropy and homogeneity in the 21-cm power spectrum

    NASA Astrophysics Data System (ADS)

    Shiraishi, Maresuke; Muñoz, Julian B.; Kamionkowski, Marc; Raccanelli, Alvise

    2016-05-01

    Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic microwave background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asymmetry, consistent with these observations. Observations of clustering of quasars show, however, agreement with statistical isotropy at much smaller angular scales. Here, we propose to use off-diagonal components of the angular power spectrum of the 21-cm fluctuations during the dark ages to test this power asymmetry. We forecast results for the planned SKA radio array, a future radio array, and the cosmic-variance-limited case as a theoretical proof of principle. Our results show that the 21-cm line power spectrum will enable access to information at very small scales and at different redshift slices, thus improving upon the current CMB constraints by ˜2 orders of magnitude for a dipolar asymmetry and by ˜1 - 3 orders of magnitude for a quadrupolar asymmetry case.

  7. Updating constraints on inflationary features in the primordial power spectrum with the Planck data

    NASA Astrophysics Data System (ADS)

    Benetti, Micol

    2013-10-01

    We present new constraints on possible features in the primordial inflationary density perturbation power spectrum in light of the recent cosmic microwave background anisotropy measurements from the Planck satellite. We found that the Planck data hints for the presence of features in two different ranges of angular scales, corresponding to multipoles 10<ℓ<60 and 150<ℓ<300, with a decrease in the best-fit χ2 value with respect to the featureless “vanilla” ΛCDM model of Δχ2≃9 in both cases.

  8. Increased photovoltaic power output via diffractive spectrum separation.

    PubMed

    Kim, Ganghun; Dominguez-Caballero, Jose A; Lee, Howard; Friedman, Daniel J; Menon, Rajesh

    2013-03-22

    In this Letter, we report the preliminary demonstration of a new paradigm for photovoltaic power generation that utilizes a broadband diffractive-optical element (BDOE) to efficiently separate sunlight into laterally spaced spectral bands. These bands are then absorbed by single-junction photovoltaic cells, whose band gaps correspond to the incident spectral bands. We designed such BDOEs by utilizing a modified version of the direct-binary-search algorithm. Gray scale lithography was used to fabricate these multilevel optics. They were experimentally characterized with an overall optical efficiency of 70% over a wavelength range of 350-1100 nm, which was in excellent agreement with simulation predictions. Finally, two prototype devices were assembled: one with a pair of copper indium gallium selenide based photovoltaic devices, and another with GaAs and c-Si photovoltaic devices. These devices demonstrated an increase in output peak electrical power of ∼ 42% and ∼ 22%, respectively, under white-light illumination. Because of the optical versatility and manufacturability of the proposed BDOEs, the reported spectrum-splitting approach provides a new approach toward low-cost solar power. PMID:25166805

  9. AlphaSpectrum ASPECT analysis code for background correction & peak integration

    Energy Science and Technology Software Center (ESTSC)

    2005-04-13

    The ASPECT code provides a means for rapid analysis of energy-resolved spectra obtained by multi-channel pulse-height analysis (MCA) during (or after) counting of alpha-emissions from a filter air sample (or other suitably prepared sample) utilizing a solid-state detector, or other detector having sufficient energy resolution indiviual radioisotope peaks indentified in a spectrum are fitted using a peak shape algorithm by non-linear least-square fitting procedures that minimize Chi-square differences between the data and a fitted peakmore » function. The code accomplishes the identification of all significant peaks present in the spectrum with automatic recalibration to the 7.68 Po-214 alpha peak from the Radon-222 decay chain, the subtraction of all radon progeny interference overlaps with lower energy peaks in the energy range of Pu-238, Am-241, Pu-239, and U-234/Th-232, and the integration of the counts in any peak identified for these transuranic radionuclides. The output is therefore in the form of isotope specific net transuranic CPM, DPM or concentration, available in near real-time during air sampling. In this "copyright" version, the assumption is made that the alpha spectra to be analyzed have been stored by unique name in sequential form: "FileName(i)", where "FileName" can be any name and i is the index number of the file saved (e.g., i = 1,2, ..., n). this format is one automatically generated by the alpha Environmental Continuous Air Monitor (ECAM), developed by Los Alamos National Laboratory, and manufactured by Canberra Industries, a Laboratory Industrial Partner for this technology. It is assumed in this version of the code that the alpha spectrum data are stored in a 256 channel spectrum, although a larger num ber of channels could be easily accommodated by small code changes. The ECAM data output format is RADNET compliant (an inidustry standard developed at Los Alamos), and include, in addition to a 256-channel alpha spectrum, data on the

  10. AlphaSpectrum ASPECT analysis code for background correction & peak integration

    SciTech Connect

    Rodgers, John C.

    2005-04-13

    The ASPECT code provides a means for rapid analysis of energy-resolved spectra obtained by multi-channel pulse-height analysis (MCA) during (or after) counting of alpha-emissions from a filter air sample (or other suitably prepared sample) utilizing a solid-state detector, or other detector having sufficient energy resolution indiviual radioisotope peaks indentified in a spectrum are fitted using a peak shape algorithm by non-linear least-square fitting procedures that minimize Chi-square differences between the data and a fitted peak function. The code accomplishes the identification of all significant peaks present in the spectrum with automatic recalibration to the 7.68 Po-214 alpha peak from the Radon-222 decay chain, the subtraction of all radon progeny interference overlaps with lower energy peaks in the energy range of Pu-238, Am-241, Pu-239, and U-234/Th-232, and the integration of the counts in any peak identified for these transuranic radionuclides. The output is therefore in the form of isotope specific net transuranic CPM, DPM or concentration, available in near real-time during air sampling. In this "copyright" version, the assumption is made that the alpha spectra to be analyzed have been stored by unique name in sequential form: "FileName(i)", where "FileName" can be any name and i is the index number of the file saved (e.g., i = 1,2, ..., n). this format is one automatically generated by the alpha Environmental Continuous Air Monitor (ECAM), developed by Los Alamos National Laboratory, and manufactured by Canberra Industries, a Laboratory Industrial Partner for this technology. It is assumed in this version of the code that the alpha spectrum data are stored in a 256 channel spectrum, although a larger num ber of channels could be easily accommodated by small code changes. The ECAM data output format is RADNET compliant (an inidustry standard developed at Los Alamos), and include, in addition to a 256-channel alpha spectrum, data on the count time

  11. Contribution of domain wall networks to the CMB power spectrum

    NASA Astrophysics Data System (ADS)

    Lazanu, A.; Martins, C. J. A. P.; Shellard, E. P. S.

    2015-07-01

    We use three domain wall simulations from the radiation era to the late-time dark energy domination era based on the PRS algorithm to calculate the energy-momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.

  12. Power Spectrum Density of Long-Term MAXI Data

    NASA Astrophysics Data System (ADS)

    Sugimoto, Juri; Mihara, Tatehiro; Sugizaki, Mutsumi; Serino, Motoko; Kitamoto, Shunji; Sato, Ryousuke; Ueda, Yoshihiro; Ueno, Shiro

    Monitor of All-sky X-ray Image (MAXI) on the International Space Station has been observing the X-ray sky since 2009 August 15. It has accumulated the X-ray data for about four years, so far. X-ray objects are usually variable and their variability can be studied by the power spectrum density (PSD) of the X-ray light curves. We applied our method to calculate PSDs of several kinds of objects observed with MAXI. We obtained significant PSDs from 16 Seyfert galaxies. For blackhole binary Cygnus X-1 there was a difference in the shape of PSD between the hard state and the soft state. For high mass X-ray binaries, Cen X-3, SMC X-1, and LMC X-4, there were several peaks in the PSD corresponding to the orbital period and the superorbital period.

  13. Fermi-bounce cosmology and scale-invariant power spectrum

    NASA Astrophysics Data System (ADS)

    Alexander, Stephon; Bambi, Cosimo; Marcianò, Antonino; Modesto, Leonardo

    2014-12-01

    We develop a nonsingular bouncing cosmology using a nontrivial coupling of general relativity to fermionic fields. The usual big bang singularity is avoided thanks to a negative energy density contribution from the fermions. Our theory is ghost free since the fermionic operator that generates the bounce is equivalent to torsion, which has no kinetic terms. The physical system consists of standard general relativity plus a topological sector for gravity and fermionic matter described by Dirac fields with a nonminimal coupling. We show that a scale-invariant power spectrum generated in the contracting phase can be recovered by suitable choices of fermion number density and bare mass, thus providing a possible alternative to the inflationary scenario.

  14. Neutrino mass limits: Robust information from the power spectrum of galaxy surveys

    NASA Astrophysics Data System (ADS)

    Cuesta, Antonio J.; Niro, Viviana; Verde, Licia

    2016-09-01

    We present cosmological upper limits on the sum of active neutrino masses using large-scale power spectrum data from the WiggleZ Dark Energy Survey and from the Sloan Digital Sky Survey - Data Release 7 (SDSS-DR7) sample of Luminous Red Galaxies (LRG). Combining measurements on the Cosmic Microwave Background temperature and polarisation anisotropies by the Planck satellite together with WiggleZ power spectrum results in a neutrino mass bound of 0.37 eV at 95% C.L., while replacing WiggleZ by the SDSS-DR7 LRG power spectrum, the 95% C.L. bound on the sum of neutrino masses is 0.38 eV. Adding Baryon Acoustic Oscillation (BAO) distance scale measurements, the neutrino mass upper limits greatly improve, since BAO data break degeneracies in parameter space. Within a ΛCDM model, we find an upper limit of 0.13 eV (0.14 eV) at 95% C.L., when using SDSS-DR7 LRG (WiggleZ) together with BAO and Planck. The addition of BAO data makes the neutrino mass upper limit robust, showing only a weak dependence on the power spectrum used. We also quantify the dependence of neutrino mass limit reported here on the CMB lensing information. The tighter upper limit (0.13 eV) obtained with SDSS-DR7 LRG is very close to that recently obtained using Lyman-alpha clustering data, yet uses a completely different probe and redshift range, further supporting the robustness of the constraint. This constraint puts under some pressure the inverted mass hierarchy and favours the normal hierarchy.

  15. Planck 2013 results. XXI. Power spectrum and high-order statistics of the Planck all-sky Compton parameter map

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Carvalho, P.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Comis, B.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Da Silva, A.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Flores-Cacho, I.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lacasa, F.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Marcos-Caballero, A.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Melchiorri, A.; Melin, J.-B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-11-01

    We have constructed the first all-sky map of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 100 to 857 GHz frequency channel maps from the Planck survey. This map shows an obvious galaxy cluster tSZ signal that is well matched with blindly detected clusters in the Planck SZ catalogue. To characterize the signal in the tSZ map we have computed its angular power spectrum. At large angular scales (ℓ < 60), the major foreground contaminant is the diffuse thermal dust emission. At small angular scales (ℓ > 500) the clustered cosmic infrared background and residual point sources are the major contaminants. These foregrounds are carefully modelled and subtracted. We thus measure the tSZ power spectrum over angular scales 0.17° ≲ θ ≲ 3.0° that were previously unexplored. The measured tSZ power spectrum is consistent with that expected from the Planck catalogue of SZ sources, with clear evidence of additional signal from unresolved clusters and, potentially, diffuse warm baryons. Marginalized band-powers of the Planck tSZ power spectrum and the best-fit model are given. The non-Gaussianity of the Compton parameter map is further characterized by computing its 1D probability distribution function and its bispectrum. The measured tSZ power spectrum and high order statistics are used to place constraints on σ8.

  16. The Distortion of the Cosmic Microwave Background Spectrum Due to Intergalactic Dust

    NASA Astrophysics Data System (ADS)

    Imara, Nia; Loeb, Abraham

    2016-07-01

    Infrared emission from intergalactic dust might compromise the ability of future experiments to detect subtle spectral distortions in the Cosmic Microwave Background (CMB) from the early universe. We provide the first estimate of foreground contamination of the CMB signal due to diffuse dust emission in the intergalactic medium. We use models of the extragalactic background light to calculate the intensity of intergalactic dust emission and find that emission by intergalactic dust at z ≲ 0.5 exceeds the sensitivity of the planned Primordial Inflation Explorer to CMB spectral distortions by 1–3 orders of magnitude. In the frequency range ν = 150–2400 GHz, we place an upper limit of 0.06% on the contribution to the far-infrared background from intergalactic dust emission.

  17. Unscreening Modified Gravity in the Matter Power Spectrum.

    PubMed

    Lombriser, Lucas; Simpson, Fergus; Mead, Alexander

    2015-06-26

    Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k<0.3h/Mpc can yield constraints on chameleon models that are more stringent than what is inferred from Solar System tests or distance indicators in unscreened dwarf galaxies. Finally, we verify that our method is also applicable to the Vainshtein mechanism. PMID:26197114

  18. The Knotted Sky II: does BICEP2 require a nontrivial primordial power spectrum?

    SciTech Connect

    Abazajian, Kevork N.; Aslanyan, Grigor; Easther, Richard; Price, Layne C. E-mail: g.aslanyan@auckland.ac.nz E-mail: lpri691@aucklanduni.ac.nz

    2014-08-01

    An inflationary gravitational wave background consistent with BICEP2 is difficult to reconcile with a simple power-law spectrum of primordial scalar perturbations. Tensor modes contribute to the temperature anisotropies at multipoles with l∼< 100, and this effect — together with a prior on the form of the scalar perturbations — was the source of previous bounds on the tensor-to-scalar ratio. We compute Bayesian evidence for combined fits to BICEP2 and Planck for three nontrivial primordial spectra: a) a running spectral index, b) a cutoff at fixed wavenumber, and c) a spectrum described by a linear spline with a single internal knot. We find no evidence for a cutoff, weak evidence for a running index, and significant evidence for a ''broken'' spectrum. Taken at face-value, the BICEP2 results require two new inflationary parameters in order to describe both the broken scale invariance in the perturbation spectrum and the observed tensor-to-scalar ratio. Alternatively, this tension may be resolved by additional data and more detailed analyses.

  19. The thermal Sunyaev-Zel'dovich effect power spectrum in light of Planck

    NASA Astrophysics Data System (ADS)

    McCarthy, I. G.; Le Brun, A. M. C.; Schaye, J.; Holder, G. P.

    2014-06-01

    The amplitude of the thermal Sunyaev-Zel'dovich effect (tSZ) power spectrum is extremely sensitive to the abundance of the most massive dark matter haloes (galaxy clusters) and therefore to fundamental cosmological parameters that control their growth, such as σ8 and Ωm. Here we explore the sensitivity of the tSZ power spectrum to important non-gravitational (`subgrid') physics by employing the cosmo-OWLS suite of large-volume cosmological hydrodynamical simulations, run in both the Planck and 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) best-fitting cosmologies. On intermediate and small angular scales (ℓ ≳ 1000, or θ≲10 arcmin), accessible with the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT), the predicted tSZ power spectrum is highly model dependent, with gas ejection due to active galactic nuclei (AGN) feedback having a particularly large effect. However, at large scales, observable with the Planck telescope, the effects of subgrid physics are minor. Comparing the simulated tSZ power spectra with observations, we find a significant amplitude offset on all measured angular scales (including large scales), if the Planck best-fitting cosmology is assumed by the simulations. This is shown to be a generic result for all current models of the tSZ power spectrum. By contrast, if the WMAP7 cosmology is adopted, there is full consistency with the Planck tSZ power spectrum measurements on large scales and agreement at the 2σ level with the SPT and ACT measurements at intermediate scales for our fiducial AGN model, which Le Brun et al. have shown reproduces the `resolved' properties of the Local Group and cluster population remarkably well. These findings strongly suggest that there are significantly fewer massive galaxy clusters than expected for the Planck best-fitting cosmology, which is consistent with recent measurements of the tSZ number counts. Our findings therefore pose a significant challenge to the cosmological

  20. Spectrum of the cosmic background radiation: early and recent measurements from the White Mountain Research Station

    SciTech Connect

    Smoot, G.F.

    1985-09-01

    The White Mountain Research Station has provided a support facility at a high, dry, radio-quiet site for measurements that have established the blackbody character of the cosmic microwave background radiation. This finding has confirmed the interpretation of the radiation as a relic of the primeval fireball and helped to establish the hot Big Bang theory as the standard cosmological model.

  1. Analysis of noise power spectrum of gamma rays camera

    NASA Astrophysics Data System (ADS)

    Xie, Hongwei; Zhang, Faqiang; Zhang, Jianhua; Chen, Jinchuan; Chen, Dingyang; Li, Linbo

    2014-01-01

    Gamma rays camera is widely used in many studies, including the image diagnostics of the radiation sources, flash photography, and nondestructive assessment (NDA), etc. As a major component of the high sensitivity gamma rays camera, the MCP image intensifier is characterized in the intensified image, tunable shutter time and gain. The gamma rays camera is consisting with rays-fluorescence convertor, the optical imaging system, the MCP image intensifier, CCD and other devices. The performance of the gamma rays camera is mainly dependent on such parameters as the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE), etc. All of the parameters are somewhat limited by the noise characteristics of the system. Compared with the standard derivative noise distribution, the NPS, which can reflect the evolution characteristics of the noise of the imaging system with the change of the spatial frequency, could convey more information on the noise distribution in the system. In this paper, theoretical analysis is presented on the major sources of the noise in the gamma rays camera. Based on the analysis, the noise power spectra of the gamma rays camera were calibrated under various radiation dosages respectively with the visible light and gamma rays radiation sources (0.2MeV and 1.25MeV in energy, respectively). As indicated by the experimental results, the noise is majorly induced by the fluctuations of the gain of the MCP image intensifier. And the remarkable noise peak occurs nearby the spatial frequency of about 0.633 Hz/mm. And almost the same phenomena were found with both the 0.2MeV and 1.25MeV radiation energy. Besides, the noise power spectra are in circular symmetrical distribution, whose intensities are rapidly decreased with the increasing spatial frequencies.

  2. Increasing the quantitative credibility of open-path FT-IR spectroscopic data with focus on several properties of the background spectrum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The choice of the type of background spectrum affects the credibility of open-path Fourier transform infrared (OP/FT-IR) spectroscopic data, and consequently the quality of data analysis. We systematically investigated several properties of the background spectrum. The results show that a short-pa...

  3. Tissue type characterization using photoacoustic power spectrum, a feasibility study

    NASA Astrophysics Data System (ADS)

    Tavakoli, Behnoosh; Goldstein, Seth D.; Kang, Jin U.; Choti, Michaal; Boctor, Emad M.

    2015-03-01

    The development of technologies capable of non-invasive characterization of tissue has the potential to significantly improve diagnostic and therapeutic medical interventions. In this study we investigated the feasibility of a noninvasive photoacoustic (PA) approach for characterizing biological tissues. The measurement was performed in the transmission mode with a wideband hydrophone while a tunable Q-switched Nd:YAG pulsed laser was used for illumination. The power spectrum of photoacoustic signal induced by a pulsed laser light from tissue was analyzed and features were extracted to study their correlation with tissue biomechanical properties. For a controlled study, tissue mimicking gelatin phantoms with different densities and equivalent optical absorptions were used as targets. The correlation between gelatin concentration of such phantoms and their mechanical properties were validated independently with a dynamic mechanical analyzer capable of calculating complex loss and storage moduli between two compression plates. It was shown that PA spectrums were shifted towards higher frequencies by increasing gelatin concentration. In order to quantify this effect, signal energy in two intervals of low and high frequency ranges were calculated. Gelatin concentration was correlated with PA energy in high frequency range with R2=0.94. Subsequently, PA signals generated from freshly resected human thyroid specimens were measured and analyzed in a similar fashion. We found that in aggregate, malignant thyroid tissue contains approximately 1.6 times lower energy in the high frequency range in comparison to normal thyroid tissue (p<0.01). This ratio increased with increasing illumination wavelength from 700 nm to 900nm. In summary, this study demonstrated the feasibility of using photoacoustic technique for characterizing tissue on the basis of viscoelastic properties of the tissue.

  4. Angular power spectrum of sterile neutrino decay lines: the role of eROSITA

    NASA Astrophysics Data System (ADS)

    Zandanel, Fabio; Weniger, Christoph; Ando, Shin’ichiro

    2016-05-01

    We study the potential of the angular auto and cross-correlation power spectrum of the cosmic X-ray background in identifying sterile neutrino dark matter taking as reference the performances of the soon-to-be-launched eROSITA satellite. The main astrophysical background sources in this case are active galactic nuclei, galaxies powered by X-ray binaries, and clusters of galaxies. We show that while sterile neutrino decays are always subdominant in the autocorrelation power spectra, they can be efficiently enhanced when cross-correlating with tracers of the dark matter distribution. We estimate that the four-years eROSITA all-sky survey will potentially provide very stringent constraints on the sterile neutrino decay lifetime by cross-correlating the cosmic X-ray background with the 2MASS galaxy catalogue. This will allow to firmly test the recently claimed 3.56-keV X-ray line found towards several clusters and galaxies and its decaying dark matter interpretation. We finally stress that the main limitation of this approach is due to the shot noise of the galaxy catalogues used as tracers for the dark matter distribution, a limitation that we need to overcome to fully exploit the potential of the eROSITA satellite in this context.

  5. Infrared divergence of pure Einstein gravity contributions to the cosmological density power spectrum.

    PubMed

    Noh, Hyerim; Jeong, Donghui; Hwang, Jai-Chan

    2009-07-10

    We probe the pure Einstein gravity contributions to the second-order density power spectrum. On the small scale, we discover that Einstein's gravity contribution is negligibly small. This guarantees that Newton's gravity is currently sufficient to handle the baryon acoustic oscillation scale. On the large scale, however, we discover that Einstein's gavity contribution to the second-order power spectrum dominates the linear-order power spectrum. Thus, the pure Einstein gravity contribution appearing in the third-order perturbation leads to an infrared divergence in the power spectrum. PMID:19659195

  6. Monte Carlo simulations to estimate the background spectrum in a shielded NaI(Tl) gamma-spectrometric system.

    PubMed

    Sengupta Mitra, Mausumi; Sarkar, P K

    2005-10-01

    The paper describes a Monte Carlo simulation technique to estimate the background gamma-radiation for a low-level counting setup with NaI(Tl) detector inside an iron shield box. With monoenergetic gamma-sources ranging from 300 to 2000 keV at intervals of 100 keV we have got a matrix of transmitted flux data calculated using a general purpose Monte Carlo code. The intrinsic efficiency of the detector is also calculated. This matrix of data is folded with the measured spectrum outside the setup to estimate the observed spectrum in the NaI(Tl) detector. We have studied various combinations of splitting and Russian roulette to arrive at an optimal combination based on the figure of merit of the Monte Carlo results. The observed discrepancy between the measured and calculated spectra is mainly due to porosity of the iron shield box. PMID:15998590

  7. Semi-blind Bayesian inference of CMB map and power spectrum

    NASA Astrophysics Data System (ADS)

    Vansyngel, Flavien; Wandelt, Benjamin D.; Cardoso, Jean-François; Benabed, Karim

    2016-04-01

    We present a new blind formulation of the cosmic microwave background (CMB) inference problem. The approach relies on a phenomenological model of the multifrequency microwave sky without the need for physical models of the individual components. For all-sky and high resolution data, it unifies parts of the analysis that had previously been treated separately such as component separation and power spectrum inference. We describe an efficient sampling scheme that fully explores the component separation uncertainties on the inferred CMB products such as maps and/or power spectra. External information about individual components can be incorporated as a prior giving a flexible way to progressively and continuously introduce physical component separation from a maximally blind approach. We connect our Bayesian formalism to existing approaches such as Commander, spectral mismatch independent component analysis (SMICA), and internal linear combination (ILC), and discuss possible future extensions.

  8. Estimating the power spectrum covariance matrix with fewer mock samples

    NASA Astrophysics Data System (ADS)

    Pearson, David W.; Samushia, Lado

    2016-03-01

    The covariance matrices of power-spectrum (P(k)) measurements from galaxy surveys are difficult to compute theoretically. The current best practice is to estimate covariance matrices by computing a sample covariance of a large number of mock catalogues. The next generation of galaxy surveys will require thousands of large volume mocks to determine the covariance matrices to desired accuracy. The errors in the inverse covariance matrix are larger and scale with the number of P(k) bins, making the problem even more acute. We develop a method of estimating covariance matrices using a theoretically justified, few-parameter model, calibrated with mock catalogues. Using a set of 600 BOSS DR11 mock catalogues, we show that a seven parameter model is sufficient to fit the covariance matrix of BOSS DR11 P(k) measurements. The covariance computed with this method is better than the sample covariance at any number of mocks and only ˜100 mocks are required for it to fully converge and the inverse covariance matrix converges at the same rate. This method should work equally well for the next generation of galaxy surveys, although a demand for higher accuracy may require adding extra parameters to the fitting function.

  9. Parameterizing the power spectrum: Beyond the truncated Taylor expansion

    SciTech Connect

    Abazajian, Kevork; Kadota, Kenji; Stewart, Ewan D.; /KAIST, Taejon /Canadian Inst. Theor. Astrophys.

    2005-07-01

    The power spectrum is traditionally parameterized by a truncated Taylor series: ln P(k) = ln P{sub *} + (n{sub *} - 1) ln(k/k{sub *}) + 1/2 n'{sub *} ln{sup 2} (k/k{sub *}). It is reasonable to truncate the Taylor series if |n'{sub *} ln(k/k{sub *})| << |n{sub *} - 1|, but it is not if |n'{sub *} ln(k/k{sub *})| {approx}> |n{sub *} - 1|. We argue that there is no good theoretical reason to prefer |n'{sub *}| << |n{sub *} - 1|, and show that current observations are consistent with |n*{sub *} ln(k/k{sub *})| {approx} |n{sub *} - 1| even for |ln(k/k{sub *})| {approx} 1. Thus, there are regions of parameter space, which are both theoretically and observationally relevant, for which the traditional truncated Taylor series parameterization is inconsistent, and hence it can lead to incorrect parameter estimations. Motivated by this, we propose a simple extension of the traditional parameterization, which uses no extra parameters, but that, unlike the traditional approach, covers well motivated inflationary spectra with |n'{sub *}| {approx} |n{sub *} - 1|. Our parameterization therefore covers not only standard-slow-roll inflation models but also a much wider class of inflation models. We use this parameterization to perform a likelihood analysis for the cosmological parameters.

  10. Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field

    NASA Technical Reports Server (NTRS)

    Voorhies, C.

    1998-01-01

    The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.

  11. Roundoff noise analysis for digital signal power processors using Welch's power spectrum estimation

    NASA Technical Reports Server (NTRS)

    Chi, Chong-Yung; Long, David; Li, Fuk-Kwok

    1987-01-01

    The noise due to finite-word-length effects is analyzed for digital-signal power processors using Welch's power-spectrum estimation technique to measure the power of Gaussian random signals over a frequency band of interest. The input of the digital signal processor contains a finite-length time interval in which the true Gaussian signal is contaminated by Gaussian noise. The roundoff noise-to-signal ratio in the measurement of the signal power is derived, and computer simulations which validate the analytical results are presented. These results can be used in tradeoff studies of hardware design, such as the number of bits required at each processing stage. The results presented in this paper are currently being used in the design of a digital Doppler processor (Chi et al., 1986) for a radar scatterometer.

  12. The Atacama Cosmology Telescope: A Measurement of the Primordial Power Spectrum

    NASA Technical Reports Server (NTRS)

    Hlozek, Renee; Dunkley, Joanna; Addison, Graeme; Appel, John William; Bond, J. Richard; Carvalho, C. Sofia; Das, Sudeep; Devlin, Mark J.; Duenner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.; Gallardo, Patricio; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hughes, John P.; Irwin, Kent D.; Klein, Jeff; Kosowsky, Arthur; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Wollack, Ed

    2011-01-01

    We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT). The angular resolution of ACT provides sensitivity to scales beyond l = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k approx. = 0.2 Mp/c. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from CMB measurements (which probe the power spectrum in thc linear regime) with existing probes of galaxy clustering, cluster abundances and weak lensing constraints on the primordial power. This highlights the range of scales probed by current measurement.s of the matter power spectrum.

  13. [Restoration filtering based on projection power spectrum for single-photon emission computed tomography].

    PubMed

    Kubo, N

    1995-04-01

    To improve the quality of single-photon emission computed tomographic (SPECT) images, a restoration filter has been developed. This filter was designed according to practical "least squares filter" theory. It is necessary to know the object power spectrum and the noise power spectrum. The power spectrum is estimated from the power spectrum of a projection, when the high-frequency power spectrum of a projection is adequately approximated as a polynomial exponential expression. A study of the restoration with the filter based on a projection power spectrum was conducted, and compared with that of the "Butterworth" filtering method (cut-off frequency of 0.15 cycles/pixel), and "Wiener" filtering (signal-to-noise power spectrum ratio was a constant). Normalized mean-squared errors (NMSE) of the phantom, two line sources located in a 99mTc filled cylinder, were used. NMSE of the "Butterworth" filter, "Wiener" filter, and filtering based on a power spectrum were 0.77, 0.83, and 0.76 respectively. Clinically, brain SPECT images utilizing this new restoration filter improved the contrast. Thus, this filter may be useful in diagnosis of SPECT images. PMID:7776546

  14. Power spectrum scale invariance identifies prefrontal dysregulation in paranoid schizophrenia.

    PubMed

    Radulescu, Anca R; Rubin, Denis; Strey, Helmut H; Mujica-Parodi, Lilianne R

    2012-07-01

    Theory and experimental evidence suggest that complex living systems function close to the boundary of chaos, with erroneous organization to an improper dynamical range (too stiff or chaotic) underlying system-wide dysregulation and disease. We hypothesized that erroneous organization might therefore also characterize paranoid schizophrenia, via optimization abnormalities in the prefrontal-limbic circuit regulating emotion. To test this, we acquired fMRI scans from 35 subjects (N = 9 patients with paranoid schizophrenia and N = 26 healthy controls), while they viewed affect-valent stimuli. To quantify dynamic regulation, we analyzed the power spectrum scale invariance (PSSI) of fMRI time-courses and computed the geometry of time-delay (Poincaré) maps, a measure of variability. Patients and controls showed distinct PSSI in two clusters (k(1) : Z = 4.3215, P = 0.00002 and k(2) : Z = 3.9441, P = 0.00008), localized to the orbitofrontal/medial prefrontal cortex (Brodmann Area 10), represented by β close to white noise in patients (β ≈ 0) and in the pink noise range in controls (β ≈ -1). Interpreting the meaning of PSSI differences, the Poincaré maps indicated less variability in patients than controls (Z = -1.9437, P = 0.05 for k(1) ; Z = -2.5099, P = 0.01 for k(2) ). That the dynamics identified Brodmann Area 10 is consistent with previous schizophrenia research, which implicates this area in deficits of working memory, executive functioning, emotional regulation and underlying biological abnormalities in synaptic (glutamatergic) transmission. Our results additionally cohere with a large body of work finding pink noise to be the normal range of central function at the synaptic, cellular, and small network levels, and suggest that patients show less supple responsivity of this region. PMID:21567663

  15. The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum

    NASA Technical Reports Server (NTRS)

    Dunkley, J.; Hlozek, R.; Sievers, J.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Bertrand Doriese, W.; Dunner, R.; Essinger-Hileman, T.; Fisher, R. P.; Fowler, J. W.; Hajian, A.; Moseley, H.; Wollack, E.

    2011-01-01

    We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10,000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be Beta(sub 3000) is identical to 6.8 +/- 2.9 mu K (exp 2), where Beta (sub l) is identical to l(l + 1) C(sub l)/2pi. The IR Poisson power at 148 GHz is Bewta(sub 3000) 7.8 +/- 0.7 muK(exp 2) (C(sub l) = 5.5 +/- 0.5 nK(exp 2)), and a clustered IR component is required with Beta (sub 3000) = 4.6 +/- 0.9 muK(exp 2), assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 mu K(exp 2), is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index alpha = 3.69 +/- 0.14 for flux scaling as S(nu) varies as nu(sup alpha). We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological

  16. THE ATACAMA COSMOLOGY TELESCOPE: COSMOLOGICAL PARAMETERS FROM THE 2008 POWER SPECTRUM

    SciTech Connect

    Dunkley, J.; Hlozek, R.; Sievers, J.; Bond, J. R.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Barrientos, L. F.; Duenner, R.; Amiri, M.; Battistelli, E. S.; Burger, B.; Appel, J. W.; Das, S.; Essinger-Hileman, T.; Brown, B.; Chervenak, J.; Doriese, W. Bertrand

    2011-09-20

    We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg{sup 2} with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10, 000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be B{sub 3000} = 6.8 {+-} 2.9 {mu}K{sup 2}, where B{sub l}{identical_to}l(l + 1)C{sub l}/2{pi}. The IR Poisson power at 148 GHz is B{sub 3000} = 7.8 {+-} 0.7 {mu}K{sup 2} (C{sub l} = 5.5 {+-} 0.5 nK{sup 2}), and a clustered IR component is required with B{sub 3000} = 4.6 {+-} 0.9 {mu}K{sup 2}, assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 {mu}K{sup 2}, is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index {alpha} = 3.69 {+-} 0.14 for flux scaling as S({nu}){proportional_to}{nu}{sup {alpha}}. We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The {Lambda}CDM cosmological model is a good fit to the data ({chi}{sup 2}/dof = 29/46), and {Lambda}CDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n{sub s} = 1 excluded at 99.7% confidence level (CL) (3{sigma}). A model with no CMB lensing is disfavored at 2.8{sigma}. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on

  17. Tension between the power spectrum of density perturbations measured on large and small scales

    NASA Astrophysics Data System (ADS)

    Battye, Richard A.; Charnock, Tom; Moss, Adam

    2015-05-01

    There is a tension between measurements of the amplitude of the power spectrum of density perturbations inferred using the cosmic microwave background (CMB) and directly measured by large-scale structure (LSS) on smaller scales. We show that this tension exists, and is robust, for a range of LSS indicators including clusters, lensing and redshift space distortions and using CMB data from either Planck or WMAP +SPT /ACT . One obvious way to try to reconcile this is the inclusion of a massive neutrino which could be either active or sterile. Using Planck and a combination of all the LSS data we find that (i) for an active neutrino ∑mν=(0.357 ±0.099 ) eV and (ii) for a sterile neutrino msterileeff=(0.67 ±0.18 ) eV and Δ Neff=0.32 ±0.20 . This is, however, at the expense of a degraded fit to Planck temperature data, and we quantify the residual tension at 2.5 σ and 1.6 σ for massive and sterile neutrinos, respectively. We also consider alternative explanations including a lower redshift for reionization that would be in conflict with polarization measurements made by WMAP and ad hoc modifications to the primordial power spectrum.

  18. Anisotropic power spectrum and bispectrum in the f(Φ)F² mechanism

    DOE PAGESBeta

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    2013-01-04

    A suitable coupling of the inflaton φ to a vector kinetic term F² gives frozen and scale invariant vector perturbations. We compute the cosmological perturbations ζ that result from such coupling by taking into account the classical vector field that unavoidably gets generated at large scales during inflation. This generically results in a too-anisotropic power spectrum of ζ. Specifically, the anisotropy exceeds the 1% level (10% level) if inflation lasts ~5 e-folds (~50 e-folds) more than the minimal amount required to produce the cosmic microwave background modes. This conclusion applies, among others, to the application of this mechanism for magnetogenesis,more » for anisotropic inflation, and for the generation of anisotropic perturbations at the end of inflation through a waterfall field coupled to the vector (in this case, the unavoidable contribution that we obtain is effective all throughout inflation, and it is independent of the waterfall field). For a tuned duration of inflation, a 1% (10%) anisotropy in the power spectrum corresponds to an anisotropic bispectrum which is enhanced like the local one in the squeezed limit, and with an effective local fNL~3(~30). More in general, a significant anisotropy of the perturbations may be a natural outcome of all models that sustain higher than 0 spin fields during inflation.« less

  19. Anisotropic power spectrum and bispectrum in the f(Φ)F² mechanism

    SciTech Connect

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    2013-01-04

    A suitable coupling of the inflaton φ to a vector kinetic term F² gives frozen and scale invariant vector perturbations. We compute the cosmological perturbations ζ that result from such coupling by taking into account the classical vector field that unavoidably gets generated at large scales during inflation. This generically results in a too-anisotropic power spectrum of ζ. Specifically, the anisotropy exceeds the 1% level (10% level) if inflation lasts ~5 e-folds (~50 e-folds) more than the minimal amount required to produce the cosmic microwave background modes. This conclusion applies, among others, to the application of this mechanism for magnetogenesis, for anisotropic inflation, and for the generation of anisotropic perturbations at the end of inflation through a waterfall field coupled to the vector (in this case, the unavoidable contribution that we obtain is effective all throughout inflation, and it is independent of the waterfall field). For a tuned duration of inflation, a 1% (10%) anisotropy in the power spectrum corresponds to an anisotropic bispectrum which is enhanced like the local one in the squeezed limit, and with an effective local fNL~3(~30). More in general, a significant anisotropy of the perturbations may be a natural outcome of all models that sustain higher than 0 spin fields during inflation.

  20. Anisotropic power spectrum and bispectrum in the f(ϕ)F2 mechanism

    NASA Astrophysics Data System (ADS)

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    2013-01-01

    A suitable coupling of the inflaton φ to a vector kinetic term F2 gives frozen and scale invariant vector perturbations. We compute the cosmological perturbations ζ that result from such coupling by taking into account the classical vector field that unavoidably gets generated at large scales during inflation. This generically results in a too-anisotropic power spectrum of ζ. Specifically, the anisotropy exceeds the 1% level (10% level) if inflation lasts ˜5 e-folds (˜50 e-folds) more than the minimal amount required to produce the cosmic microwave background modes. This conclusion applies, among others, to the application of this mechanism for magnetogenesis, for anisotropic inflation, and for the generation of anisotropic perturbations at the end of inflation through a waterfall field coupled to the vector (in this case, the unavoidable contribution that we obtain is effective all throughout inflation, and it is independent of the waterfall field). For a tuned duration of inflation, a 1% (10%) anisotropy in the power spectrum corresponds to an anisotropic bispectrum which is enhanced like the local one in the squeezed limit, and with an effective local fNL˜3(˜30). More in general, a significant anisotropy of the perturbations may be a natural outcome of all models that sustain higher than 0 spin fields during inflation.

  1. Application of power spectrum, cepstrum, higher order spectrum and neural network analyses for induction motor fault diagnosis

    NASA Astrophysics Data System (ADS)

    Liang, B.; Iwnicki, S. D.; Zhao, Y.

    2013-08-01

    The power spectrum is defined as the square of the magnitude of the Fourier transform (FT) of a signal. The advantage of FT analysis is that it allows the decomposition of a signal into individual periodic frequency components and establishes the relative intensity of each component. It is the most commonly used signal processing technique today. If the same principle is applied for the detection of periodicity components in a Fourier spectrum, the process is called the cepstrum analysis. Cepstrum analysis is a very useful tool for detection families of harmonics with uniform spacing or the families of sidebands commonly found in gearbox, bearing and engine vibration fault spectra. Higher order spectra (HOS) (also known as polyspectra) consist of higher order moment of spectra which are able to detect non-linear interactions between frequency components. For HOS, the most commonly used is the bispectrum. The bispectrum is the third-order frequency domain measure, which contains information that standard power spectral analysis techniques cannot provide. It is well known that neural networks can represent complex non-linear relationships, and therefore they are extremely useful for fault identification and classification. This paper presents an application of power spectrum, cepstrum, bispectrum and neural network for fault pattern extraction of induction motors. The potential for using the power spectrum, cepstrum, bispectrum and neural network as a means for differentiating between healthy and faulty induction motor operation is examined. A series of experiments is done and the advantages and disadvantages between them are discussed. It has been found that a combination of power spectrum, cepstrum and bispectrum plus neural network analyses could be a very useful tool for condition monitoring and fault diagnosis of induction motors.

  2. The Knotted Sky I: Planck constraints on the primordial power spectrum

    SciTech Connect

    Aslanyan, Grigor; Price, Layne C.; Easther, Richard; Abazajian, Kevork N. E-mail: lpri691@aucklanduni.ac.nz E-mail: r.easther@auckland.ac.nz

    2014-08-01

    Using the temperature data from Planck we search for departures from a power-law primordial power spectrum, employing Bayesian model-selection and posterior probabilities. We parametrize the spectrum with n knots located at arbitrary values of logk, with both linear and cubic splines. This formulation recovers both slow modulations and sharp transitions in the primordial spectrum. The power spectrum is well-fit by a featureless, power-law at wavenumbers k>10{sup -3} Mpc{sup -1}. A modulated primordial spectrum yields a better fit relative to ΛCDM at large scales, but there is no strong evidence for a departure from a power-law spectrum. Moreover, using simulated maps we show that a local feature at k ∼ 10{sup -3} Mpc{sup -1} can mimic the suppression of large-scale power. With multi-knot spectra we see only small changes in the posterior distributions for the other free parameters in the standard ΛCDM universe. Lastly, we investigate whether the hemispherical power asymmetry is explained by independent features in the primordial power spectrum in each ecliptic hemisphere, but find no significant differences between them.

  3. Power spectrum analysis of polarized emission from the Canadian galactic plane survey

    SciTech Connect

    Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.

    2014-05-20

    Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg{sup 2}. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from ℓ ≈ 60 to ℓ ≈ 10{sup 4} and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.

  4. Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.

    2014-05-01

    Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg2. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from l ≈ 60 to l ≈ 104 and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.

  5. THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM

    SciTech Connect

    Gong Yan; Cooray, Asantha

    2013-07-20

    The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by the Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD), and photon escape fraction from galaxies out to z = 6. Our results are basically consistent with the existing determinations of the quantities. We find a larger photon escape fraction at high redshifts, especially at z = 3, compared to the result from recent Ly{alpha} measurements. Our SFRD result is consistent with the data from both gamma-ray burst and ultraviolet (UV) observations in the 1{sigma} level. However, the average SFRD we obtain at z {approx}> 3 matches the gamma-ray data better than the UV data. Thus our SFRD result at z {approx}> 6 favors the fact that star formation alone is sufficiently high enough to reionize the universe.

  6. Reconstruction of the primordial fluctuation spectrum from the five-year WMAP data by the cosmic inversion method with band-power decorrelation analysis

    SciTech Connect

    Nagata, Ryo; Yokoyama, Jun'ichi

    2008-12-15

    The primordial curvature fluctuation spectrum is reconstructed by the cosmic inversion method using the five-year Wilkinson Microwave Anisotropy Probe data of the cosmic microwave background temperature anisotropy. We apply the covariance matrix analysis and decompose the reconstructed spectrum into statistically independent band-powers. The statistically significant deviation from a simple power-law spectrum suggested by the analysis of the first-year data is not found in the five-year data except possibly at one point near the border of the wave number domain where accurate reconstruction is possible.

  7. First Year Wilkinson Microwave Anisotropy Probe(WMAP)Observations: The Angular Power Spectrum

    NASA Technical Reports Server (NTRS)

    Hinshaw, G.; Spergel, D. N.; Verde, L.; Hill, R. S.; Meyer, S. S.; Barnes, C.; Bennett, C. L.; Halpern, M.; Jarosik, N.; Kogut, A.

    2003-01-01

    We present the angular power spectrum derived from the first-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We study a variety of power spectrum estimation methods and data combinations and demonstrate that the results are robust. The data are modestly contaminated by diffuse Galactic foreground emission, but we show that a simple Galactic template model is sufficient to remove the signal. Point sources produce a modest contamination in the low frequency data. After masking approximately 700 known bright sources from the maps, we estimate residual sources contribute approximately 3500 mu sq Kappa at 41 GHz, and approximately 130 mu sq Kappa at 94 GHz, to the power spectrum [iota(iota + 1)C(sub iota)/2pi] at iota = 1000. Systematic errors are negligible compared to the (modest) level of foreground emission. Our best estimate of the power spectrum is derived from 28 cross-power spectra of statistically independent channels. The final spectrum is essentially independent of the noise properties of an individual radiometer. The resulting spectrum provides a definitive measurement of the CMB power spectrum, with uncertainties limited by cosmic variance, up to iota approximately 350. The spectrum clearly exhibits a first acoustic peak at iota = 220 and a second acoustic peak at iota approximately 540, and it provides strong support for adiabatic initial conditions. Researchers have analyzed the CT(sup Epsilon) power spectrum, and present evidence for a relatively high optical depth, and an early period of cosmic reionization. Among other things, this implies that the temperature power spectrum has been suppressed by approximately 30% on degree angular scales, due to secondary scattering.

  8. Unveiling acoustic physics of the CMB using nonparametric estimation of the temperature angular power spectrum for Planck

    SciTech Connect

    Aghamousa, Amir; Shafieloo, Arman; Arjunwadkar, Mihir; Souradeep, Tarun E-mail: shafieloo@kasi.re.kr E-mail: tarun@iucaa.ernet.in

    2015-02-01

    Estimation of the angular power spectrum is one of the important steps in Cosmic Microwave Background (CMB) data analysis. Here, we present a nonparametric estimate of the temperature angular power spectrum for the Planck 2013 CMB data. The method implemented in this work is model-independent, and allows the data, rather than the model, to dictate the fit. Since one of the main targets of our analysis is to test the consistency of the ΛCDM model with Planck 2013 data, we use the nuisance parameters associated with the best-fit ΛCDM angular power spectrum to remove foreground contributions from the data at multipoles ℓ ≥50. We thus obtain a combined angular power spectrum data set together with the full covariance matrix, appropriately weighted over frequency channels. Our subsequent nonparametric analysis resolves six peaks (and five dips) up to ℓ ∼1850 in the temperature angular power spectrum. We present uncertainties in the peak/dip locations and heights at the 95% confidence level. We further show how these reflect the harmonicity of acoustic peaks, and can be used for acoustic scale estimation. Based on this nonparametric formalism, we found the best-fit ΛCDM model to be at 36% confidence distance from the center of the nonparametric confidence set—this is considerably larger than the confidence distance (9%) derived earlier from a similar analysis of the WMAP 7-year data. Another interesting result of our analysis is that at low multipoles, the Planck data do not suggest any upturn, contrary to the expectation based on the integrated Sachs-Wolfe contribution in the best-fit ΛCDM cosmology.

  9. Elimination of threshold-induced distortion in the power spectrum of narrow-band laser speckle

    NASA Astrophysics Data System (ADS)

    Ducharme, Alfred D.; Boreman, Glenn D.; Yang, Sidney S.

    1995-10-01

    The distortion in the power spectrum of narrow-band laser speckle that results from irradiance thresholding is quantified. A method for compensation of this distortion is presented. An optimal threshold level is presented that simplifies the compensation method.

  10. The BaR-SPOrt experiment: measuring the CMBP E-mode power spectrum from Dome C

    NASA Astrophysics Data System (ADS)

    Carretti, E.; Cortiglioni, S.; Bernardi, G.; Casarini, L.; Cecchini, S.; Macculi, C.; Ramponi, M.; Sbarra, C.; Ventura, G.; Monari, J.; Poloni, M.; Poppi, S.; Baralis, M.; Peverini, O. A.; Tascone, R.; Virone, G.; Zannoni, M.; Bonometto, S.; Colombo, L.; Gervasi, M.; Sironi, G.; Fabbri, R.; Natale, V.; Nesti, R.; Nicastro, L.; de Bernardis, P.; Masi, S.; de Petris, M.; Boscaleri, A.; Sazhin, M.; Vinyajkin, E.

    The BaR-SPOrt experiment is designed to measure the E-mode power spectrum of the Cosmic Microwave Background Polarization (CMBP) in the multipole range 50 < ℓ < 1000. In the current configuration at 32 GHz it can explore up to ℓ = 400. Recent low frequency observations of the target region show that the synchrotron emission should not contamine the CMBP already at 32 GHz. A 6-month observation of a 6° × 6° sky area during the polar night, in ideal environmental conditions, will allow the Italian-French collaboration to both measure the E mode power spectrum with appropriate sensitivity and perform important tests of the anomalous dust emission. The BaR-SPOrt 32 GHz instrument, now under test and ready for operations by Spring 2005, is proposed for 1 2 years Winter operations at Dome C.

  11. Reconstruction of the primordial power spectrum of curvature perturbations using multiple data sets

    NASA Astrophysics Data System (ADS)

    Hunt, Paul; Sarkar, Subir

    2014-01-01

    Detailed knowledge of the primordial power spectrum of curvature perturbations is essential both in order to elucidate the physical mechanism (`inflation') which generated it, and for estimating the cosmological parameters from observations of the cosmic microwave background and large-scale structure. Hence it ought to be extracted from such data in a model-independent manner, however this is difficult because relevant cosmological observables are given by a convolution of the primordial perturbations with some smoothing kernel which depends on both the assumed world model and the matter content of the universe. Moreover the deconvolution problem is ill-conditioned so a regularisation scheme must be employed to control error propagation. We demonstrate that `Tikhonov regularisation' can robustly reconstruct the primordial spectrum from multiple cosmological data sets, a significant advantage being that both its uncertainty and resolution are then quantified. Using Monte Carlo simulations we investigate several regularisation parameter selection methods and find that generalised cross-validation and Mallow's Cp method give optimal results. We apply our inversion procedure to data from the Wilkinson Microwave Anisotropy Probe, other ground-based small angular scale CMB experiments, and the Sloan Digital Sky Survey. The reconstructed spectrum (assuming the standard ΛCDM cosmology) is not scale-free but has an infrared cutoff at klesssim5 × 10-4 Mpc-1 (due to the anomalously low CMB quadrupole) and several features with ~ 2σ significance at k/Mpc-1 ~ 0.0013-0.0025, 0.0362-0.0402 and 0.051-0.056, reflecting the `WMAP glitches'. To test whether these are indeed real will require more accurate data, such as from the Planck satellite and new ground-based experiments.

  12. Reconstruction of the primordial power spectrum of curvature perturbations using multiple data sets

    SciTech Connect

    Hunt, Paul; Sarkar, Subir E-mail: s.sarkar@physics.ox.ac.uk

    2014-01-01

    Detailed knowledge of the primordial power spectrum of curvature perturbations is essential both in order to elucidate the physical mechanism ('inflation') which generated it, and for estimating the cosmological parameters from observations of the cosmic microwave background and large-scale structure. Hence it ought to be extracted from such data in a model-independent manner, however this is difficult because relevant cosmological observables are given by a convolution of the primordial perturbations with some smoothing kernel which depends on both the assumed world model and the matter content of the universe. Moreover the deconvolution problem is ill-conditioned so a regularisation scheme must be employed to control error propagation. We demonstrate that 'Tikhonov regularisation' can robustly reconstruct the primordial spectrum from multiple cosmological data sets, a significant advantage being that both its uncertainty and resolution are then quantified. Using Monte Carlo simulations we investigate several regularisation parameter selection methods and find that generalised cross-validation and Mallow's C{sub p} method give optimal results. We apply our inversion procedure to data from the Wilkinson Microwave Anisotropy Probe, other ground-based small angular scale CMB experiments, and the Sloan Digital Sky Survey. The reconstructed spectrum (assuming the standard ΛCDM cosmology) is not scale-free but has an infrared cutoff at k∼<5 × 10{sup −4} Mpc{sup −1} (due to the anomalously low CMB quadrupole) and several features with ∼ 2σ significance at k/Mpc{sup −1} ∼ 0.0013–0.0025, 0.0362–0.0402 and 0.051–0.056, reflecting the 'WMAP glitches'. To test whether these are indeed real will require more accurate data, such as from the Planck satellite and new ground-based experiments.

  13. Fourier Power Spectrum Characteristics of Face Photographs: Attractiveness Perception Depends on Low-Level Image Properties

    PubMed Central

    Langner, Oliver; Wiese, Holger; Redies, Christoph

    2015-01-01

    We investigated whether low-level processed image properties that are shared by natural scenes and artworks – but not veridical face photographs – affect the perception of facial attractiveness and age. Specifically, we considered the slope of the radially averaged Fourier power spectrum in a log-log plot. This slope is a measure of the distribution of special frequency power in an image. Images of natural scenes and artworks possess – compared to face images – a relatively shallow slope (i.e., increased high spatial frequency power). Since aesthetic perception might be based on the efficient processing of images with natural scene statistics, we assumed that the perception of facial attractiveness might also be affected by these properties. We calculated Fourier slope and other beauty-associated measurements in face images and correlated them with ratings of attractiveness and age of the depicted persons (Study 1). We found that Fourier slope – in contrast to the other tested image properties – did not predict attractiveness ratings when we controlled for age. In Study 2A, we overlaid face images with random-phase patterns with different statistics. Patterns with a slope similar to those in natural scenes and artworks resulted in lower attractiveness and higher age ratings. In Studies 2B and 2C, we directly manipulated the Fourier slope of face images and found that images with shallower slopes were rated as more attractive. Additionally, attractiveness of unaltered faces was affected by the Fourier slope of a random-phase background (Study 3). Faces in front of backgrounds with statistics similar to natural scenes and faces were rated as more attractive. We conclude that facial attractiveness ratings are affected by specific image properties. An explanation might be the efficient coding hypothesis. PMID:25835539

  14. High frequency formulation for the acoustic power spectrum due to cascade-turbulence interaction.

    PubMed

    Cheong, Cheolung; Joseph, Phillip; Lee, Soogab

    2006-01-01

    This paper investigates the noise radiated by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. An analytic formulation for the spectrum of acoustic power of a two-dimensional flat-plate is derived. The main finding of this paper is that the acoustic power spectrum from the cascade of flat airfoils may be split into two distinct frequency regions of low frequency and high frequency, separated by a critical frequency. Below this frequency, cascade effects due to the interaction between neighboring airfoils are shown to be important. At frequencies above the critical frequency, cascade effects are shown to be relatively weak. In this frequency range, acoustic power is shown to be approximately proportional to the number of blades. Based on this finding at high frequencies, an approximate expression is derived for the power spectrum that is valid above the critical frequency and which is in excellent agreement with the exact expression for the broadband power spectrum. The formulation is used to perform a parametric study on the effects on the power spectrum of the blade number, stagger angle, gap-chord ratio, and Mach number. The theory is also shown to provide a close fit to the measured spectrum of rotor-stator interaction. PMID:16454269

  15. The power spectrum and bispectrum of SDSS DR11 BOSS galaxies - II. Cosmological interpretation

    NASA Astrophysics Data System (ADS)

    Gil-Marín, Héctor; Verde, Licia; Noreña, Jorge; Cuesta, Antonio J.; Samushia, Lado; Percival, Will J.; Wagner, Christian; Manera, Marc; Schneider, Donald P.

    2015-09-01

    We examine the cosmological implications of the measurements of the linear growth rate of cosmological structure obtained in a companion paper from the power spectrum and bispectrum monopoles of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 11, CMASS galaxies. This measurement was of f 0.43σ8, where σ8 is the amplitude of dark matter density fluctuations, and f is the linear growth rate, at the effective redshift of the survey, zeff = 0.57. In conjunction with cosmic microwave background (CMB) data, interesting constraints can be placed on models with non-standard neutrino properties and models where gravity deviates from General Relativity on cosmological scales. In particular, the sum of the masses of the three species of the neutrinos is constrained to mν < 0.49 eV (at 95 per cent confidence level) when the f 0.43σ8 measurement is combined with state-of-the-art CMB measurements. Allowing the effective number of neutrinos to vary as a free parameter does not significantly change these results. When we combine the measurement of f 0.43σ8 with the complementary measurement of fσ8 from the monopole and quadrupole of the two-point correlation function, we are able to obtain an independent measurements of f and σ8. We obtain f = 0.63 ± 0.16 and σ8 = 0.710 ± 0.086 (68 per cent confidence level). This is the first time when these parameters have been able to be measured independently using the redshift-space power spectrum and bispectrum measurements from galaxy clustering data only.

  16. Neutrino masses and cosmology with Lyman-alpha forest power spectrum

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, Nathalie; Yèche, Christophe; Baur, Julien; Magneville, Christophe; Rossi, Graziano; Lesgourgues, Julien; Borde, Arnaud; Burtin, Etienne; LeGoff, Jean-Marc; Rich, James; Viel, Matteo; Weinberg, David

    2015-11-01

    We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the ΛCDM model, using the one-dimensional Lyα-forest power spectrum measured by [1] from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III), complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by [2] by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Lyα data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index ns. Combining BOSS Lyα with Planck CMB constrains the sum of neutrino masses to ∑ mν < 0.12 eV (95% C.L.) including all identified systematic uncertainties, tighter than our previous limit (0.15 eV) and more robust. Adding Lyα data to CMB data reduces the uncertainties on the optical depth to reionization τ, through the correlation of τ with σ8. Similarly, correlations between cosmological parameters help in constraining the tensor-to-scalar ratio of primordial fluctuations r. The tension on ns can be accommodated by allowing for a running dns/d ln k. Allowing running as a free parameter in the fits does not change the limit on ∑ mν. We discuss possible interpretations of these results in the context of slow-roll inflation.

  17. Optimized Large-scale CMB Likelihood and Quadratic Maximum Likelihood Power Spectrum Estimation

    NASA Astrophysics Data System (ADS)

    Gjerløw, E.; Colombo, L. P. L.; Eriksen, H. K.; Górski, K. M.; Gruppuso, A.; Jewell, J. B.; Plaszczynski, S.; Wehus, I. K.

    2015-11-01

    We revisit the problem of exact cosmic microwave background (CMB) likelihood and power spectrum estimation with the goal of minimizing computational costs through linear compression. This idea was originally proposed for CMB purposes by Tegmark et al., and here we develop it into a fully functioning computational framework for large-scale polarization analysis, adopting WMAP as a working example. We compare five different linear bases (pixel space, harmonic space, noise covariance eigenvectors, signal-to-noise covariance eigenvectors, and signal-plus-noise covariance eigenvectors) in terms of compression efficiency, and find that the computationally most efficient basis is the signal-to-noise eigenvector basis, which is closely related to the Karhunen-Loeve and Principal Component transforms, in agreement with previous suggestions. For this basis, the information in 6836 unmasked WMAP sky map pixels can be compressed into a smaller set of 3102 modes, with a maximum error increase of any single multipole of 3.8% at ℓ ≤ 32 and a maximum shift in the mean values of a joint distribution of an amplitude-tilt model of 0.006σ. This compression reduces the computational cost of a single likelihood evaluation by a factor of 5, from 38 to 7.5 CPU seconds, and it also results in a more robust likelihood by implicitly regularizing nearly degenerate modes. Finally, we use the same compression framework to formulate a numerically stable and computationally efficient variation of the Quadratic Maximum Likelihood implementation, which requires less than 3 GB of memory and 2 CPU minutes per iteration for ℓ ≤ 32, rendering low-ℓ QML CMB power spectrum analysis fully tractable on a standard laptop.

  18. Power spectrum tomography of dark matter annihilation with local galaxy distribution

    SciTech Connect

    Ando, Shin'ichiro

    2014-10-01

    Cross-correlating the gamma-ray background with local galaxy catalogs potentially gives stringent constraints on dark matter annihilation. We provide updated theoretical estimates of sensitivities to the annihilation cross section from gamma-ray data with Fermi telescope and 2MASS galaxy catalogs, by elaborating the galaxy power spectrum and astrophysical backgrounds, and adopting the Markov-Chain Monte Carlo simulations. In particular, we show that taking tomographic approach by dividing the galaxy catalogs into more than one redshift slice will improve the sensitivity by a factor of a few to several. If dark matter halos contain lots of bright substructures, yielding a large annihilation boost (e.g., a factor of ∼100 for galaxy-size halos), then one may be able to probe the canonical annihilation cross section for thermal production mechanism up to masses of ∼700 GeV. Even with modest substructure boost (e.g., a factor of ∼10 for galaxy-size halos), on the other hand, the sensitivities could still reach a factor of three larger than the canonical cross section for dark matter masses of tens to a few hundreds of GeV.

  19. Spectrum sensing and resource allocation for multicarrier cognitive radio systems under interference and power constraints

    NASA Astrophysics Data System (ADS)

    Dikmese, Sener; Srinivasan, Sudharsan; Shaat, Musbah; Bader, Faouzi; Renfors, Markku

    2014-12-01

    Multicarrier waveforms have been commonly recognized as strong candidates for cognitive radio. In this paper, we study the dynamics of spectrum sensing and spectrum allocation functions in cognitive radio context using very practical signal models for the primary users (PUs), including the effects of power amplifier nonlinearities. We start by sensing the spectrum with energy detection-based wideband multichannel spectrum sensing algorithm and continue by investigating optimal resource allocation methods. Along the way, we examine the effects of spectral regrowth due to the inevitable power amplifier nonlinearities of the PU transmitters. The signal model includes frequency selective block-fading channel models for both secondary and primary transmissions. Filter bank-based wideband spectrum sensing techniques are applied for detecting spectral holes and filter bank-based multicarrier (FBMC) modulation is selected for transmission as an alternative multicarrier waveform to avoid the disadvantage of limited spectral containment of orthogonal frequency-division multiplexing (OFDM)-based multicarrier systems. The optimization technique used for the resource allocation approach considered in this study utilizes the information obtained through spectrum sensing and knowledge of spectrum leakage effects of the underlying waveforms, including a practical power amplifier model for the PU transmitter. This study utilizes a computationally efficient algorithm to maximize the SU link capacity with power and interference constraints. It is seen that the SU transmission capacity depends critically on the spectral containment of the PU waveform, and these effects are quantified in a case study using an 802.11-g WLAN scenario.

  20. Conservative constraints on dark matter from the Fermi-LAT isotropic diffuse gamma-ray background spectrum

    SciTech Connect

    Abazajian, Kevork N.; Agrawal, Prateek; Chacko, Zackaria; Kilic, Can E-mail: apr@umd.edu E-mail: kilic@physics.rutgers.edu

    2010-11-01

    We examine the constraints on final state radiation from Weakly Interacting Massive Particle (WIMP) dark matter candidates annihilating into various standard model final states, as imposed by the measurement of the isotropic diffuse gamma-ray background by the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope. The expected isotropic diffuse signal from dark matter annihilation has contributions from the local Milky Way (MW) as well as from extragalactic dark matter. The signal from the MW is very insensitive to the adopted dark matter profile of the halos, and dominates the signal from extragalactic halos, which is sensitive to the low mass cut-off of the halo mass function. We adopt a conservative model for both the low halo mass survival cut-off and the substructure boost factor of the Galactic and extragalactic components, and only consider the primary final state radiation. This provides robust constraints which reach the thermal production cross-section for low mass WIMPs annihilating into hadronic modes. We also reanalyze limits from HESS observations of the Galactic Ridge region using a conservative model for the dark matter halo profile. When combined with the HESS constraint, the isotropic diffuse spectrum rules out all interpretations of the PAMELA positron excess based on dark matter annihilation into two lepton final states. Annihilation into four leptons through new intermediate states, although constrained by the data, is not excluded.

  1. Contribution of strong discontinuities to the power spectrum of the solar wind.

    PubMed

    Borovsky, Joseph E

    2010-09-10

    Eight and a half years of magnetic field measurements (2(22) samples) from the ACE spacecraft in the solar wind at 1 A.U. are analyzed. Strong (large-rotation-angle) discontinuities in the solar wind are collected and measured. An artificial time series is created that preserves the timing and amplitudes of the discontinuities. The power spectral density of the discontinuity series is calculated and compared with the power spectral density of the solar-wind magnetic field. The strong discontinuities produce a power-law spectrum in the "inertial subrange" with a spectral index near the Kolmogorov -5/3 index. The discontinuity spectrum contains about half of the power of the full solar-wind magnetic field over this "inertial subrange." Warnings are issued about the significant contribution of discontinuities to the spectrum of the solar wind, complicating interpretation of spectral power and spectral indices. PMID:20867562

  2. Power Versus Spectrum 2-D Sensing in Energy Harvesting Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Zhang, Yanyan; Han, Weijia; Li, Di; Zhang, Ping; Cui, Shuguang

    2015-12-01

    Energy harvester based cognitive radio is a promising solution to address the shortage of both spectrum and energy. Since the spectrum access and power consumption patterns are interdependent, and the power value harvested from certain environmental sources are spatially correlated, the new power dimension could provide additional information to enhance the spectrum sensing accuracy. In this paper, the Markovian behavior of the primary users is considered, based on which we adopt a hidden input Markov model to specify the primary vs. secondary dynamics in the system. Accordingly, we propose a 2-D spectrum and power (harvested) sensing scheme to improve the primary user detection performance, which is also capable of estimating the primary transmit power level. Theoretical and simulated results demonstrate the effectiveness of the proposed scheme, in term of the performance gain achieved by considering the new power dimension. To the best of our knowledge, this is the first work to jointly consider the spectrum and power dimensions for the cognitive primary user detection problem.

  3. An automatic method to determine cutoff frequency based on image power spectrum

    SciTech Connect

    Beis, J.S.; Celler, A.; Barney, J.S.

    1995-12-01

    The authors present an algorithm for automatically choosing filter cutoff frequency (F{sub c}) using the power spectrum of the projections. The method is based on the assumption that the expectation of the image power spectrum is the sum of the expectation of the blurred object power spectrum (dominant at low frequencies) plus a constant value due to Poisson noise. By considering the discrete components of the noise-dominated high-frequency spectrum as a Gaussian distribution N({mu},{sigma}), the Student t-test determines F{sub c} as the highest frequency for which the image frequency components are unlikely to be drawn from N ({mu},{sigma}). The method is general and can be applied to any filter. In this work, the authors tested the approach using the Metz restoration filter on simulated, phantom, and patient data with good results. Quantitative performance of the technique was evaluated by plotting recovery coefficient (RC) versus NMSE of reconstructed images.

  4. CMB lensing power spectrum biases from galaxies and clusters using high-angular resolution temperature maps

    SciTech Connect

    Van Engelen, A.; Sehgal, N.; Bhattacharya, S.; Holder, G. P.; Zahn, O.; Nagai, D.

    2014-05-01

    The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to the Atacama Cosmology Telescope and the South Pole Telescope. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on σ{sub 8} and an uncertainty on the total neutrino mass of ∼50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M {sub vir} = 10{sup 14} M {sub ☉}. To achieve such percent level bias, we find that only modes up to a maximum multipole of l {sub max} ∼ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.

  5. Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study

    NASA Technical Reports Server (NTRS)

    Szabo, A.; Koval, A.; Merka, J.; Narock, T.

    2011-01-01

    The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the 2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

  6. Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study

    NASA Technical Reports Server (NTRS)

    Szabo, A.; Koval, A.; Merka, J.; Narock, T.

    2010-01-01

    The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions . The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

  7. Multi-redshift limits on the Epoch of Reionization 21cm power spectrum from PAPER

    NASA Astrophysics Data System (ADS)

    Jacobs, Danny; Pober, Jonathan; Parsons, Aaron; Paper Team

    2015-01-01

    The epoch of reionization hydrogen power spectrum is expected to vary strongly with redshift with cosmic history as star formation progressively ionizes the pervasive intergalactic hydrogen. We present an analysis of observations from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) telescope which place new limits on the HI power spectrum over the redshift range of 7.5power spectrum is bright foreground emission, which varies slowly with redshift. To suppress these foregrounds, we use filtering techniques adopted from digital signal processing to isolate foreground in power spectrum k-space. This 500 hour integration demonstrates a spectral rejection dynamic range of 10^4. The measured power spectrum uncertainty compares well with the expected thermal noise. Relative to this thermal noise, most spectra exhibit an excess of power at a few sigma. The possible sources of this modest excess include residual foreground leakage, particularly at the highest redshift, and unflagged RFI.

  8. Constraints on primordial non-Gaussianity from WMAP7 and luminous red galaxies power spectrum and forecast for future surveys

    SciTech Connect

    De Bernardis, Francesco; Serra, Paolo; Cooray, Asantha; Melchiorri, Alessandro

    2010-10-15

    We place new constraints on the primordial local non-Gaussianity parameter f{sub NL} using recent cosmic microwave background anisotropy and galaxy clustering data. We model the galaxy power spectrum according to the halo model, accounting for a scale-dependent bias correction proportional to f{sub NL}/k{sup 2}. We first constrain f{sub NL} in a full 13 parameters analysis that includes 5 parameters of the halo model and 7 cosmological parameters. Using the WMAP7 CMB data and the SDSS DR4 galaxy power spectrum, we find f{sub NL}=171{sub -139}{sup +140} at 68% C.L. and -69power spectrum data finding, for a {Lambda}CDM+f{sub NL} model, f{sub NL}=-93{+-}128 at 68% C.L. and -327

  9. Cosmology from the thermal Sunyaev-Zel'dovich power spectrum: Primordial non-Gaussianity and massive neutrinos

    NASA Astrophysics Data System (ADS)

    Hill, J. Colin; Pajer, Enrico

    2013-09-01

    We carry out a comprehensive analysis of the possible constraints on cosmological and astrophysical parameters achievable with measurements of the thermal Sunyaev-Zel’dovich (tSZ) power spectrum from upcoming full-sky cosmic microwave background observations, with a particular focus on one-parameter extensions to the ΛCDM standard model involving local primordial non-Gaussianity (described by fNL) and massive neutrinos (described by Mν). We include all of the relevant physical effects due to these additional parameters, including the change to the halo mass function and the scale-dependent halo bias induced by local primordial non-Gaussianity. We use the halo model to compute the tSZ power spectrum and provide a pedagogical derivation of the one- and two-halo terms in an Appendix. We model the pressure profile of the intracluster medium (ICM) using a parametrized fit that agrees well with existing observations, and include uncertainty in the ICM modeling by including the overall normalization and outer logarithmic slope of the profile as free parameters. We compute forecasts for Planck, Primordial Inflation Explorer (PIXIE), and a cosmic variance (CV)-limited experiment, using multifrequency subtraction to remove foregrounds and implementing two masking criteria based on the ROSAT and eROSITA cluster catalogs to reduce the significant CV errors at low multipoles. We find that Planck can detect the tSZ power spectrum with >30σ significance, regardless of the masking scenario. However, neither Planck or PIXIE is likely to provide competitive constraints on fNL from the tSZ power spectrum due to CV noise at low ℓ overwhelming the unique signature of the scale-dependent bias. A future CV-limited experiment could provide a 3σ detection of fNL≃37, which is the WMAP9 maximum-likelihood result. The outlook for neutrino masses is more optimistic: Planck can reach levels comparable to the current upper bounds ≲0.3eV with conservative assumptions about the ICM

  10. Angular Power Spectrum in Modular Invariant Inflation Model

    SciTech Connect

    Hayashi, Mitsuo J.; Okame, Y.; Takagi, K.; Watanabe, T.; Hirai, S.; Takami, T.

    2008-05-29

    A scalar potential of inflation is proposed and the angular power spectra of the adiabatic density perturbations are computed. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T = 1, we find that the potential behaves like the single-field potential of S, which slowly rolls down. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index n{sub s} = 0.951.The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the {lambda}CDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data.