315 results found
de, Bernardis P, Ade PAR, et al., 2001, Images of the early universe from the BOOMERanG experiment, Melville, 20th texas symposium on relativistic astrophysics, Austin, Texas, 10 - 15 2000, Publisher: American Institute of Physics, Pages: 157-171
, 2001, ERRATUM, The Astrophysical Journal, Vol: 558, Pages: L145-L145, ISSN: 0004-637X
Balbi A, Ade P, Bock J, et al., 2000, Constraints on Cosmological Parameters from MAXIMA-1, The Astrophysical Journal, Vol: 545, Pages: L1-L4, ISSN: 0004-637X
Bond JR, Jaffe AH, Knox L, 2000, Radical Compression of Cosmic Microwave Background Data, The Astrophysical Journal, Vol: 533, Pages: 19-37, ISSN: 0004-637X
Bond JR, Jaffe AH, Knox L, 2000, Radical compression of cosmic microwave background data, Astrophysical Journal, Vol: 533, Pages: 19-37, ISSN: 0004-637X
Powerful constraints on theories can already be inferred from existing CMB anisotropy data. But performing an exact analysis of available data is a complicated task and may become prohibitively so for upcoming experiments with ≳ 10 4 pixels. We present a method for approximating the likelihood that takes power spectrum constraints, e.g., "band-powers," as inputs. We identify a bias which results if one approximates the probability distribution of the band-power errors as Gaussian - as is the usual practice. This bias can be eliminated by using specific approximations to the non-Gaussian form for the distribution specified by three parameters (the maximum likelihood or mode, curvature or variance, and a third quantity). We advocate the calculation of this third quantity by experimenters, to be presented along with the maximum-likelihood band-power and variance. We use this non-Gaussian form to estimate the power spectrum of the CMB in 11 bands from multipole moment ℓ = 2 (the quadrupole) to ℓ = 3000 from all published band-power data. We investigate the robustness of our power spectrum estimate to changes in these approximations as well as to selective editing of the data.
Buchalter A, Kamionkowski M, Jaffe AH, 2000, The Angular Three‐Point Correlation Function in the Quasi‐linear Regime, The Astrophysical Journal, Vol: 530, Pages: 36-52, ISSN: 0004-637X
Buchalter A, Kamionkowski M, Jaffe AH, 2000, The angular three-point correlation function in the quasi-linear regime, Astrophysical Journal, Vol: 530, Pages: 36-52, ISSN: 0004-637X
We calculate the normalized angular three-point correlation function (3PCF), q, as well as the normalized angular skewness, s 3 , assuming the small-angle approximation, for a biased mass distribution in flat and open cold dark matter (CDM) models with Gaussian initial conditions. The leading-order perturbative results incorporate the explicit dependence on the cosmological parameters, the shape of the CDM transfer function, the linear evolution of the power spectrum, the form of the assumed redshift distribution function, and linear and nonlinear biasing, which may be evolving. Results are presented for different redshift distributions, including that appropriate for the APM Galaxy Survey, as well as for a survey with a mean redshift of z̄ ≃ 1 (such as the VLA FIRST Survey). Qualitatively, many of the results found for s 3 and q are similar to those obtained in a related treatment of the spatial skewness and 3PCF, such as a leading-order correction to the standard result for s 3 in the case of nonlinear bias (as defined for unsmoothed density fields), and the sensitivity of the configuration dependence of q to both cosmological and biasing models. We show that since angular correlation functions (CFs) are sensitive to clustering over a range of redshifts, the various evolutionary dependences included in our predictions imply that measurements of q in a deep survey might better discriminate between models with different histories, such as evolving versus nonevolving bias, that can have similar spatial CFs at low redshift. Our calculations employ a derived equation, valid for open, closed, and flat models, to obtain the angular bispectrum from the spatial bispectrum in the small-angle approximation.
De Bernardis P, Ade PAR, Bock JJ, et al., 2000, A flat Universe from high-resolution maps of the cosmic microwave background radiation, Nature, Vol: 404, Pages: 955-959, ISSN: 0028-0836
The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole I(peak) = (197 ± 6), with an amplitude ΔT 200 = (69 ± 8) μK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.
Ferreira PG, Jaffe AH, 2000, Simultaneous estimation of noise and signal in cosmic microwave background experiments, Monthly Notices of the Royal Astronomical Society, Vol: 312, Pages: 89-102, ISSN: 0035-8711
To correctly analyse data sets from current microwave detection technology, one is forced to estimate the sky signal and experimental noise simultaneously. Given a time-ordered data set we propose a formalism and method for estimating the signal and associated errors without prior knowledge of the noise power spectrum. We derive the method using a Bayesian formalism and relate it to the standard methods; in particular we show how this leads to a change in the estimate of the noise covariance matrix of the sky signal. We study the convergence and accuracy of the method on two mock observational strategies and discuss its application to a currently-favoured calibration procedure.
Hanany S, Ade P, Balbi A, et al., 2000, MAXIMA-1: A measurement of the cosmic microwave background anisotropy on angular scales of 10′-5°, Astrophysical Journal, Vol: 545, ISSN: 0004-637X
We present a map and an angular power spectrum of the anisotropy of the cosmic microwave background (CMB) from the first flight of the Millimeter-wave Anisotropy Experiment Imaging Array (MAXIMA). MAXIMA is a balloon-borne experiment with an array of 16 bolometric photometers operated at 100 mK. MAXIMA observed a 124 deg 2 region of the sky with 10′ resolution at frequencies of 150, 240, and 410 GHz. The data were calibrated using in-flight measurements of the CMB dipole anisotropy. A map of the CMB anisotropy was produced from three 150 and one 240 GHz photometer without need for foreground subtractions. Analysis of this CMB map yields a power spectrum for the CMB anisotropy over the range 36 ≤ l ≤ 785. The spectrum shows a peak with an amplitude of 78 ± 6 μK at l ≃ 220 and an amplitude varying between ∼40 and ∼50 μK for 400 ≲ l ≲ 785.
Hanany S, Ade P, Balbi A, et al., 2000, MAXIMA-1: A Measurement of the Cosmic Microwave Background Anisotropy on Angular Scales of 10[arcmin]–5°, The Astrophysical Journal, Vol: 545, Pages: L5-L9, ISSN: 0004-637X
Jaffe AH, 2000, Polarization pursuers’ guide, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 61, ISSN: 1550-7998
We calculate the detectability of the polarization of the cosmic microwave background (CMB) as a function of the sky coverage, angular resolution, and instrumental sensitivity for a hypothetical experiment. We consider the gradient component of the polarization from density perturbations (scalar modes) and the curl component from gravitational waves (tensor modes). We show that the amplitude (and thus the detectability) of the polarization from density perturbations is roughly the same in any model as long as the model fits the big-bang-nucleosynthesis (BBN) baryon density and degree-scale anisotropy measurements. The degree-scale polarization is smaller (and accordingly more difficult to detect) if the baryon density is higher. We show that the sensitivity to the polarization from density perturbations and gravitational waves is improved (by a factor of 30) in a fixed-time experiment with a deeper survey of a smaller region of sky. © 2000 The American Physical Society.
Juszkiewicz R, 2000, Evidence for a Low-Density Universe from the Relative Velocities of Galaxies, Science, Vol: 287, Pages: 109-112, ISSN: 0036-8075
Mauskopf PD, Ade PAR, de Bernardis P, et al., 2000, Measurement of a Peak in the Cosmic Microwave Background Power Spectrum from the North American Test Flight of Boomerang, The Astrophysical Journal, Vol: 536, Pages: L59-L62, ISSN: 0004-637X
Mauskopf PD, Ade PRA, De Bernardis P, et al., 2000, Measurement of a peak in the cosmic microwave background power spectrum from the North American test flight of boomerang, Astrophysical Journal, Vol: 536, ISSN: 0004-637X
We describe a measurement of the angular power spectrum of anisotropies in the cosmic microwave background (CMB) at scales of 0°.3 to 5° from the North American test flight of the Boomerang experiment. Boomerang is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotropies on a long-duration balloon flight. During a 6 hr test flight of a prototype system in 1997, we mapped more than 200 deg 2 at high Galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26′ and 16′.5 FWHM, respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of 1° with an amplitude 70 μΚ CMB .
Melchiorri A, Ade PAR, De Bernardis P, et al., 2000, A measurement of Ω from the North American test flight of boomerang, Astrophysical Journal, Vol: 536, ISSN: 0004-637X
We use the angular power spectrum of the cosmic microwave background, measured during the North American test flight of the Boomerang experiment, to constrain the geometry of the universe. Within the class of cold dark matter models, we find that the overall fractional energy density of the universe Ω is constrained to be 0.85 ≤ Ω ≤ 1.25 at the 68% confidence level. Combined with the COBE measurement, the data on degree scales from the Microwave Anisotropy Telescope in Chile, and the high-redshift supernovae data, we obtain new constraints on the fractional matter density and the cosmological constant.
Melchiorri A, Ade PAR, de Bernardis P, et al., 2000, A Measurement of Ω from the North American Test Flight of Boomerang, The Astrophysical Journal, Vol: 536, Pages: L63-L66, ISSN: 0004-637X
Bond JR, Crittenden RG, Jaffe AH, et al., 1999, Computing challenges of the cosmic microwave background, Computing in Science and Engineering, Vol: 1, Pages: 21-34, ISSN: 1521-9615
Bond JR, Jaffe AH, 1999, Constraining large-scale structure theories with the cosmic background radiation, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 357, Pages: 57-75, ISSN: 1364-503X
The case is strong that cosmic microwave background (CMB) and large-scale structure (LSS) observations can be combined to determine the theory of structure formation and the cosmological parameters that define it. We review: the relevant (10+) parameters associated with the inflation model of fluctuation generation and the matter content of the universe; the relation between LSS and primary and secondary CMB anisotropy probes as a function of wavenumber; how COBE constraints on energy injection rule out explosions as a dominant source of LSS; and how current anisotropy band-powers in multipole-space, at levels ca. (10 -5 ) 2 , strongly support the gravitational instability theory and suggest the universe could not have reionized too early. We use Bayesian analysis methods to determine what current CMB and CMB+LSS data imply for inflation-based Gaussian fluctuations in tilted ΛCDM, ΛhCDM and oCDM model sequences with cosmological age 11-15 Gyr, consisting of mixtures of baryons, cold 'c' (and possibly hot 'h') dark matter, vacuum energy 'Λ', and curvature energy 'o' in open cosmologies. For example, we find the slope of the initial spectrum is within about 5% of the (preferred) scale-invariant form when just the CMB data are used, and for ΛCDM when LSS data are combined with CMB; with both, a non-zero value of Ω Λ is strongly preferred (ca. 2/3 for a 13 Gyr sequence, similar to the value from SNIa). The oCDM sequence prefers Ω tot < 1, but is overall much less likely than the flat Ω Λ ≠ 0 sequence with CMB + LSS. We also review the rosy forecasts of angular power spectra and parameter estimates from future balloon and satellite experiments when foreground and systematic effects are ignored to show where cosmic parameter determination can go with CMB information alone.
Ferreira PG, Juszkiewicz R, Feldman HA, et al., 1999, Streaming Velocities as a Dynamical Estimator of Ω, The Astrophysical Journal, Vol: 515, Pages: L1-L4, ISSN: 0004-637X
Ferreira PG, Juszkiewicz R, Feldman HA, et al., 1999, Streaming velocities as a dynamical estimator of Ω, Astrophysical Journal, Vol: 515, ISSN: 0004-637X
It is well known that estimating the mean pairwise velocity of galaxies v 12 from the redshift space galaxy correlation function is difficult because this method is highly sensitive to the assumed model of the pairwise velocity dispersion. Here we propose an alternative method to estimate v 12 directly from peculiar velocity samples, which contain redshift-independent distances as well as galaxy redshifts. In contrast to other dynamical measures which determine β = Ω 0.6 σ 8 , this method can provide an estimate of Ω 0.6 σ 2 8 for a range of σ 8 , where Ω is the cosmological density parameter, while σ 8 is the standard normalization for the power spectrum of density fluctuations. We demonstrate how to measure this quantity from realistic catalogs.
Tenorio L, Jaffe AH, Hanany S, et al., 1999, Applications of wavelets to the analysis of cosmic microwave background maps, Monthly Notices of the Royal Astronomical Society, Vol: 310, Pages: 823-834, ISSN: 0035-8711
We consider wavelets as a tool to perform a variety of tasks in the context of analysing cosmic microwave background (CMB) maps. Using spherical Haar wavelets, we define a position and angular-scale-dependent measure of power that can be used to assess the existence of spatial structure. We apply planar Daubechies wavelets for the identification and removal of point sources from small sections of sky maps. Our technique can successfully identify virtually all point sources that are above 3σ and more than 80 per cent of those above 1σ. We discuss the trade-offs between the levels of correct and false detections. We denoise and compress a 100 000-pixel CMB map by a factor of ∼10 in 5 s, achieving a noise reduction of about 35 per cent. In contrast to Wiener filtering, the compression process is model-independent and very fast. We discuss the usefulness of wavelets for power spectrum and cosmological-parameter estimation. We conclude that at present wavelet functions are most suitable for identifying localized sources.
Bond JR, Jaffe AH, Knox L, 1998, Estimating the power spectrum of the cosmic microwave background, Physical Review D, Vol: 57, Pages: 2117-2137, ISSN: 0556-2821
Hanany S, Jaffe AH, Scannapieco E, 1998, The effect of the detector response time on bolometric cosmic microwave background anisotropy experiments, Monthly Notices of the Royal Astronomical Society, Vol: 299, Pages: 653-660, ISSN: 0035-8711
We analyse the effects of the detector response time on bolometric measurements of the anisotropy of the cosmic microwave background (CMB). We quantify the effect in terms of a single dimensionless parameter L defined as the ratio between the time the beam sweeps its own size and the bolometer response time. As L decreases below ∼2.5, the point-source response of the experiment becomes elongated. We introduce a window function matrix based on the timestream data to assess the effects of the elongated beam. We find that the values of the window function matrix elements decrease slowly as a function of L. Our analysis and results apply to other cases of beam asymmetry. For the High Frequency Instrument on board the Planck Surveyor satellite we show that, for a broad range of L, the ability of the experiment to extract the cosmological parameters is not degraded. Our analysis enhances the flexibility in tuning the design parameters of CMB anisotropy experiments.
Jaffe AH, Kamionkowski M, 1998, Calculation of the Ostriker-Vishniac effect in cold dark matter models, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 58, Pages: 10-4300110, ISSN: 1550-7998
We present a new derivation of the cosmic microwave background anisotropy spectrum from the Ostriker-Vishniac effect for an open, flat, or closed universe, and calculate the anisotropy expected in cold dark matter (CDM) models. We provide simple semi-analytic fitting formulas for the Vishniac power spectrum that can be used to evaluate the expected anisotropy in CDM models for any arbitrary ionization history. In a flat universe, CDM models normalized to cluster abundances produce rms temperature anisotropies of 0.8–2.4 μK on arcminute angular scales for a constant ionization fraction of unity, whereas an ionization fraction of 0.2 yields rms anisotropies of 0.3–0.8 μK. In an open and/or high-baryon-density universe, the level of anisotropy is somewhat higher. The signal in some of these models may be detectable with planned interferometry experiments. The damping of the acoustic peaks in the primary-anisotropy spectrum at degree angular scales depends primarily on the optical depth and only secondarily on the epoch of reionization. On the other hand, the amplitude of Ostriker-Vishniac anisotropies depends sensitively on the epoch of reionization. Therefore, when combined with the estimate of the reionization optical depth provided by maps of degree-scale anisotropies, the Ostriker-Vishniac effect can provide a unique probe of the epoch of reionization. © 1998 The American Physical Society.
Kamionkowski M, Jaffe AH, 1998, New troubles for inflation?, Nature, Vol: 395, Pages: 639-641, ISSN: 0028-0836
To extract reliable cosmic parameters from cosmic microwave background datasets, it is essential to show that the data are not contaminated by residual non-cosmological signals. We describe general statistical approaches to this problem, with an emphasis on the case in which there are two datasets that can be checked for consistency. A first visual step is the Wiener filter mapping from one set of data onto the pixel basis of another. For more quantitative analyses, we develop and apply both Bayesian and frequentist techniques. We define the “contamination parameter” and advocate the calculation of its probability distribution as a means of examining the consistency of two datasets. The closely related “probability enhancement factor” is shown to be a useful statistic for comparison; it is significantly better than a number of (Formula presented) quantities we consider. Our methods can be used internally (between different subsets of a dataset) or externally (between different experiments), for observing regions that completely overlap, partially overlap or overlap not at all, and for observing strategies that differ greatly. We apply the methods to check the consistency (internal and external) of the MSAM92, MSAM94 and Saskatoon Ring datasets. From comparing the two MSAM datasets, we find that (given a particular model of the contaminant) the most probable level of contamination is 12%, with no contamination only 1.05 times less probable, 50% contamination about 8 times less probable and 100% contamination strongly ruled out at over (Formula presented) times less probable. From comparing the 1992 MSAM flight with the Saskatoon data, we find the most probable level of contamination to be 50%, with no contamination only 1.6 times less probable and 100% contamination 13 times less probable. Our methods can also be used to calibrate one experiment off of another. To achieve the best agreement between the Saskatoon and MSAM92 data, we find that t
, 1998, 100 and 50 years ago, Nature, Vol: 395, Pages: 640-640, ISSN: 0028-0836
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