46 research outputs found
Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Angular Power Spectra
We present the temperature and polarization angular power spectra of the
cosmic microwave background (CMB) derived from the first 5 years of WMAP data.
The 5-year temperature (TT) spectrum is cosmic variance limited up to multipole
l=530, and individual l-modes have S/N>1 for l<920. The best fitting
six-parameter LambdaCDM model has a reduced chi^2 for l=33-1000 of
chi^2/nu=1.06, with a probability to exceed of 9.3%. There is now significantly
improved data near the third peak which leads to improved cosmological
constraints. The temperature-polarization correlation (TE) is seen with high
significance. After accounting for foreground emission, the low-l reionization
feature in the EE power spectrum is preferred by \Delta\chi^2=19.6 for optical
depth tau=0.089 by the EE data alone, and is now largely cosmic variance
limited for l=2-6. There is no evidence for cosmic signal in the BB, TB, or EB
spectra after accounting for foreground emission. We find that, when averaged
over l=2-6, l(l+1)C^{BB}_l/2\pi < 0.15 uK^2 (95% CL).Comment: 29 pages, 13 figures, accepted by ApJ
Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Are There Cosmic Microwave Background Anomalies?
(Abridged) A simple six-parameter LCDM model provides a successful fit to
WMAP data, both when the data are analyzed alone and in combination with other
cosmological data. Even so, it is appropriate to search for any hints of
deviations from the now standard model of cosmology, which includes inflation,
dark energy, dark matter, baryons, and neutrinos. The cosmological community
has subjected the WMAP data to extensive and varied analyses. While there is
widespread agreement as to the overall success of the six-parameter LCDM model,
various "anomalies" have been reported relative to that model. In this paper we
examine potential anomalies and present analyses and assessments of their
significance. In most cases we find that claimed anomalies depend on posterior
selection of some aspect or subset of the data. Compared with sky simulations
based on the best fit model, one can select for low probability features of the
WMAP data. Low probability features are expected, but it is not usually
straightforward to determine whether any particular low probability feature is
the result of the a posteriori selection or of non-standard cosmology. We
examine in detail the properties of the power spectrum with respect to the LCDM
model. We examine several potential or previously claimed anomalies in the sky
maps and power spectra, including cold spots, low quadrupole power,
quadropole-octupole alignment, hemispherical or dipole power asymmetry, and
quadrupole power asymmetry. We conclude that there is no compelling evidence
for deviations from the LCDM model, which is generally an acceptable
statistical fit to WMAP and other cosmological data.Comment: 19 pages, 17 figures, also available with higher-res figures on
http://lambda.gsfc.nasa.gov; accepted by ApJS; (v2) text as accepte
Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Power Spectra and WMAP-Derived Parameters
(Abridged) We present the angular power spectra derived from the 7-year maps
and discuss the cosmological conclusions that can be inferred from WMAP data
alone. The third acoustic peak in the TT spectrum is now well measured by WMAP.
In the context of a flat LambdaCDM model, this improvement allows us to place
tighter constraints on the matter density from WMAP data alone, and on the
epoch of matter-radiation equality, The temperature-polarization (TE) spectrum
is detected in the 7-year data with a significance of 20 sigma, compared to 13
sigma with the 5-year data. The low-l EE spectrum, a measure of the optical
depth due to reionization, is detected at 5.5 sigma significance when averaged
over l = 2-7. The BB spectrum, an important probe of gravitational waves from
inflation, remains consistent with zero. The upper limit on tensor modes from
polarization data alone is a factor of 2 lower with the 7-year data than it was
using the 5-year data (Komatsu et al. 2010). We test the parameter recovery
process for bias and find that the scalar spectral index, ns, is biased high,
but only by 0.09 sigma, while the remaining parameters are biased by < 0.15
sigma. The improvement in the third peak measurement leads to tighter lower
limits from WMAP on the number of relativistic degrees of freedom (e.g.,
neutrinos) in the early universe: Neff > 2.7 (95% CL). Also, using WMAP data
alone, the primordial helium mass fraction is found to be YHe = 0.28+0.14-0.15,
and with data from higher-resolution CMB experiments included, we now establish
the existence of pre-stellar helium at > 3 sigma (Komatsu et al. 2010).Comment: 22 pages, 14 figures, version accepted to Astrophysical Journal
Supplement Series, added high-l EE detection, consolidated parameter recovery
simulation
Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
We present new full-sky temperature and polarization maps in five frequency
bands from 23 to 94 GHz, based on data from the first five years of the WMAP
sky survey. The five-year maps incorporate several improvements in data
processing made possible by the additional years of data and by a more complete
analysis of the instrument calibration and in-flight beam response. We present
several new tests for systematic errors in the polarization data and conclude
that Ka band data (33 GHz) is suitable for use in cosmological analysis, after
foreground cleaning. This significantly reduces the overall polarization
uncertainty. With the 5 year WMAP data, we detect no convincing deviations from
the minimal 6-parameter LCDM model: a flat universe dominated by a cosmological
constant, with adiabatic and nearly scale-invariant Gaussian fluctuations.
Using WMAP data combined with measurements of Type Ia supernovae and Baryon
Acoustic Oscillations, we find (68% CL uncertainties): Omega_bh^2 = 0.02267 \pm
0.00059, Omega_ch^2 = 0.1131 \pm 0.0034, Omega_Lambda = 0.726 \pm 0.015, n_s =
0.960 \pm 0.013, tau = 0.084 \pm 0.016, and Delta_R^2 = (2.445 \pm 0.096) x
10^-9. From these we derive: sigma_8 = 0.812 \pm 0.026, H_0 = 70.5 \pm 1.3
km/s/Mpc, z_{reion} = 10.9 \pm 1.4, and t_0 = 13.72 \pm 0.12 Gyr. The new limit
on the tensor-to-scalar ratio is r < 0.22 (95% CL). We obtain tight,
simultaneous limits on the (constant) dark energy equation of state and spatial
curvature: -0.14 < 1+w < 0.12 and -0.0179 < Omega_k < 0.0081 (both 95% CL). The
number of relativistic degrees of freedom (e.g. neutrinos) is found to be
N_{eff} = 4.4 \pm 1.5, consistent with the standard value of 3.04. Models with
N_{eff} = 0 are disfavored at >99.5% confidence.Comment: 46 pages, 13 figures, and 7 tables. Version accepted for publication,
ApJS, Feb-2009. Includes 5-year dipole results and additional references.
Also available at
http://lambda.gsfc.nasa.gov/product/map/dr3/map_bibliography.cf
The Wilkinson Microwave Anisotropy Probe (WMAP) Source Catalog
We present the list of point sources found in the WMAP 5-year maps. The
technique used in the first-year and three-year analysis now finds 390 point
sources, and the five-year source catalog is complete for regions of the sky
away from the galactic plane to a 2 Jy limit, with SNR > 4.7 in all bands in
the least covered parts of the sky. The noise at high frequencies is still
mainly radiometer noise, but at low frequencies the CMB anisotropy is the
largest uncertainty. A separate search of CMB-free V-W maps finds 99 sources of
which all but one can be identified with known radio sources. The sources seen
by WMAP are not strongly polarized. Many of the WMAP sources show significant
variability from year to year, with more than a 2:1 range between the minimum
and maximum fluxes.Comment: 31 pages Latex with 4 embedded figures. Version accepted by the ApJ
Supplement
Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Sky Maps, Systematic Errors, and Basic Results
(Abridged) New full sky temperature and polarization maps based on seven
years of data from WMAP are presented. The new results are consistent with
previous results, but have improved due to reduced noise from the additional
integration time, improved knowledge of the instrument performance, and
improved data analysis procedures. The improvements are described in detail.
The seven year data set is well fit by a minimal six-parameter flat Lambda-CDM
model. The parameters for this model, using the WMAP data in conjunction with
baryon acoustic oscillation data from the Sloan Digital Sky Survey and priors
on H_0 from Hubble Space Telescope observations, are: Omega_bh^2 = 0.02260
+-0.00053, Omega_ch^2 = 0.1123 +-0.0035, Omega_Lambda = 0.728 +0.015 -0.016,
n_s = 0.963 +-0.012, tau = 0.087 +-0.014 and sigma_8 = 0.809 +-0.024 (68 % CL
uncertainties). The temperature power spectrum signal-to-noise ratio per
multipole is greater that unity for multipoles < 919, allowing a robust
measurement of the third acoustic peak. This measurement results in improved
constraints on the matter density, Omega_mh^2 = 0.1334 +0.0056 -0.0055, and the
epoch of matter- radiation equality, z_eq = 3196 +134 -133, using WMAP data
alone. The new WMAP data, when combined with smaller angular scale microwave
background anisotropy data, results in a 3 sigma detection of the abundance of
primordial Helium, Y_He = 0.326 +-0.075.The power-law index of the primordial
power spectrum is now determined to be n_s = 0.963 +-0.012, excluding the
Harrison-Zel'dovich-Peebles spectrum by >3 sigma. These new WMAP measurements
provide important tests of Big Bang cosmology.Comment: 42 pages, 9 figures, Submitted to Astrophysical Journal Supplement
Serie
Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
We present cosmological parameter constraints based on the final nine-year
WMAP data, in conjunction with additional cosmological data sets. The WMAP data
alone, and in combination, continue to be remarkably well fit by a
six-parameter LCDM model. When WMAP data are combined with measurements of the
high-l CMB anisotropy, the BAO scale, and the Hubble constant, the densities,
Omegabh2, Omegach2, and Omega_L, are each determined to a precision of ~1.5%.
The amplitude of the primordial spectrum is measured to within 3%, and there is
now evidence for a tilt in the primordial spectrum at the 5sigma level,
confirming the first detection of tilt based on the five-year WMAP data. At the
end of the WMAP mission, the nine-year data decrease the allowable volume of
the six-dimensional LCDM parameter space by a factor of 68,000 relative to
pre-WMAP measurements. We investigate a number of data combinations and show
that their LCDM parameter fits are consistent. New limits on deviations from
the six-parameter model are presented, for example: the fractional contribution
of tensor modes is limited to r<0.13 (95% CL); the spatial curvature parameter
is limited to -0.0027 (+0.0039/-0.0038); the summed mass of neutrinos is <0.44
eV (95% CL); and the number of relativistic species is found to be 3.84+/-0.40
when the full data are analyzed. The joint constraint on Neff and the
primordial helium abundance agrees with the prediction of standard Big Bang
nucleosynthesis. We compare recent PLANCK measurements of the
Sunyaev-Zel'dovich effect with our seven-year measurements, and show their
mutual agreement. Our analysis of the polarization pattern around temperature
extrema is updated. This confirms a fundamental prediction of the standard
cosmological model and provides a striking illustration of acoustic
oscillations and adiabatic initial conditions in the early universe.Comment: 32 pages, 12 figures, v3: Version accepted to Astrophysical Journal
Supplement Series. Includes improvements in response to referee and
community; corrected 3 entries in Table 10, (w0 & wa model). See the Legacy
Archive for Microwave Background Data Analysis (LAMBDA):
http://lambda.gsfc.nasa.gov/product/map/current/ for further detai
Five-Year Wilkinson Microwave Anisotropy Probe Observations: Source Catalog
We present the list of point sources found in the Wilkinson Microwave Anisotropy Probe (WMAP) five-year maps. The technique used in the first-year and three-year analyses now finds 390 point sources, and the five-year source catalog is complete for regions of the sky away from the Galactic plane to a 2 Jy limit, with SNR > 4.7 in all bands in the least covered parts of the sky. The noise at high frequencies is still mainly radiometer noise, but at low frequencies the cosmic microwave background (CMB) anisotropy is the largest uncertainty. A separate search of CMB-free V-W maps finds 99 sources of which all but one can be identified with known radio sources. The sources seen by WMAP are not strongly polarized. Many of the WMAP sources show significant variability from year to year, with more than a 2: 1 range between the minimum and maximum fluxes.NASA NNG05GE76G, NNX07AL75G S01, LTSA03-000-0090, ATPNNG04GK55G, ADP03-0000-092Astronom
Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Bayesian Estimation of CMB Polarization Maps
We describe a sampling method to estimate the polarized CMB signal from
observed maps of the sky. We use a Metropolis-within-Gibbs algorithm to
estimate the polarized CMB map, containing Q and U Stokes parameters at each
pixel, and its covariance matrix. These can be used as inputs for cosmological
analyses. The polarized sky signal is parameterized as the sum of three
components: CMB, synchrotron emission, and thermal dust emission. The polarized
Galactic components are modeled with spatially varying power law spectral
indices for the synchrotron, and a fixed power law for the dust, and their
component maps are estimated as by-products. We apply the method to simulated
low resolution maps with pixels of side 7.2 degrees, using diagonal and full
noise realizations drawn from the WMAP noise matrices. The CMB maps are
recovered with goodness of fit consistent with errors. Computing the likelihood
of the E-mode power in the maps as a function of optical depth to reionization,
tau, for fixed temperature anisotropy power, we recover tau=0.091+-0.019 for a
simulation with input tau=0.1, and mean tau=0.098 averaged over 10 simulations.
A `null' simulation with no polarized CMB signal has maximum likelihood
consistent with tau=0. The method is applied to the five-year WMAP data, using
the K, Ka, Q and V channels. We find tau=0.090+-0.019, compared to
tau=0.086+-0.016 from the template-cleaned maps used in the primary WMAP
analysis. The synchrotron spectral index, beta, averaged over high
signal-to-noise pixels with standard deviation sigma(beta)<0.25, but excluding
~6% of the sky masked in the Galactic plane, is -3.03+-0.04. This estimate does
not vary significantly with Galactic latitude, although includes an informative
prior.Comment: 11 pages, 9 figures, matches version accepted by Ap
Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Galactic Foreground Emission
We present updated estimates of Galactic foreground emission using seven years of WMAP data. Using the power
spectrum of differences between multi-frequency template-cleaned maps, we find no evidence for foreground
contamination outside of the updated (KQ85y7) foreground mask.We place a 15μK upper bound on rms foreground
contamination in the cleaned maps used for cosmological analysis. Further, the cleaning process requires only three
power-law foregrounds outside of the mask. We find no evidence for polarized foregrounds beyond those from soft
(steep-spectrum) synchrotron and thermal dust emission; in particular we find no indication in the polarization data
of an extra “haze” of hard synchrotron emission from energetic electrons near the Galactic center. We provide an
updated map of the cosmic microwave background (CMB) using the internal linear combination method, updated
foreground masks, and updates to point source catalogs using two different techniques. With additional years of
data, we now detect 471 point sources using a five-band technique and 417 sources using a three-band CMB-free
technique. In total there are 62 newly detected point sources, a 12% increase over the five-year release. Also new
are tests of theMarkov chain Monte Carlo foreground fitting procedure against systematics in the time-stream data,
and tests against the observed beam asymmetry. Within a few degrees of the Galactic plane, the behavior in total
intensity of low-frequency foregrounds is complicated and not completely understood. WMAP data show a rapidly
steepening spectrum from 20 to 40 GHz, which may be due to emission from spinning dust grains, steepening
synchrotron, or other effects. Comparisons are made to a 1 deg 408 MHz map (Haslam et al.) and the 11 deg
ARCADE 2 data (Singal et al.).We find that spinning dust or steepening synchrotron models fit the combination of
WMAP and 408 MHz data equally well. ARCADE data appear inconsistent with the steepening synchrotron model
and consistent with the spinning dust model, though some discrepancies remain regarding the relative strength
of spinning dust emission. More high-resolution data in the 10–40 GHz range would shed much light on these
issues