10612050
First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission
The WMAP mission has mapped the full sky to determine the geometry, content, and evolution of the universe. Full sky maps are made in five microwave frequency bands to separate the temperature anisotropy of the cosmic microwave background (CMB) from foreground emission, including diffuse Galactic emission and Galactic and extragalactic point sources. We define masks that excise regions of high foreground emission, so CMB analyses can be carried out with minimal foreground contamination. We also present maps and spectra of the individual emission components, leading to an improved understanding of Galactic astrophysical processes. The effectiveness of template fits to remove foreground emission from the WMAP data is also examined. These efforts result in a CMB map with minimal contamination and a demonstration that the WMAP CMB power spectrum is insensitive to residual foreground emission. We use a Maximum Entropy Method to construct a model of the Galactic emission components. The observed total Galactic emission matches the model to <1% and the individual model components are accurate to a few percent. We find that the Milky Way resembles other normal spiral galaxies between 408 MHz and 23 GHz, with a synchrotron spectral index that is flattest (βs ∼ −2.5) near star-forming regions, especially in the plane, and steepest (βs ∼ −3) in the halo. This is consistent with a picture of relativistic cosmic ray electron generation in star-forming regions and diffusion and convection within the plane. The significant synchrotron index steepening out of the plane suggests a diffusion process in which the halo electrons are WMAP is the result of a partnership between Princeton University and NASA’s Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team. Code 685, Goddard Space Flight Center, Greenbelt, MD 20771 Science Systems and Applications, Inc. (SSAI), 10210 Greenbelt Road, Suite 600 Lanham, Maryland 20706 Dept. of Physics, Jadwin Hall, Princeton, NJ 08544 Dept of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 UCLA Astronomy, PO Box 951562, Los Angeles, CA 90095-1562 Dept. of Physics and Astronomy, University of British Columbia, Vancouver, BC Canada V6T 1Z1 National Research Council (NRC) Fellow Depts. of Astrophysics and Physics, EFI and CfCP, University of Chicago, Chicago, IL 60637 Dept. of Physics, Brown University, Providence, RI 02912
15136222
DESIGN, IMPLEMENTATION AND TESTING OF THE MAP RADIOMETERS
The Microwave Anisotropy Probe (MAP) satellite, launched June 30, 2001, will produce full sky maps of the cosmic microwave background radiation in 5 frequency bands spanning 20 106 GHz. MAP contains 20 differential radiometers built with High Electron Mobility Transistor (HEMT) amplifiers with passively cooled input stages. The design and test techniques used to evaluate and minimize systematic errors and the pre-launch performance of the radiometers for all five bands are presented. Subject headings: cosmology: cosmic microwave background—instrumentation: detectors—space vehicles: instruments
17131606
Calibration of the Far Infrared Absolute Spectrophotometer ( FIRAS ) on the Cosmic Background Explorer ( COBE 1 )
The FIRAS instrument on the COBE satellite was designed to accurately measure the spectrum of the cosmic microwave background radiation (CMBR) in the frequency range 1 to 95 cm ?1 with an angular resolution of 7. We describe the calibration of this instrument, including the method of obtaining calibration data, reduction of data, the instrument model, tting the model to the calibration data, and application of the resulting model solution to sky observations. The instrument model ts well for calibration data which resemble sky conditions. The method of propagating detector noise through the calibration process to yield a covariance matrix of the calibrated sky data is described. The nal uncertainties are variable both in frequency and position, but for a typical calibrated sky 2:6 square pixel and 0.7 cm ?1 spectral element the random detector noise limit is of order of a few times 1 The National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC) is responsible for the design, development, and operation of the Cosmic Background Explorer (COBE). Scientiic guidance is provided by the COBE Science Working Group. GSFC is also responsible for the development of the analysis software and for the production of the mission data sets. { 2 { 10 ?7 erg cm ?2 s ?1 sr ?1 cm for 2 to 20 cm ?1 , and the diierence between the sky and the best t cosmic blackbody can be measured with a gain uncertainty of less than 3%.
118946449
An Absolute Measurement of the Cosmic Microwave Background Radiation Temperature at 10.7 GHz
A balloon-borne experiment has measured the absolute temperature of the cosmic microwave background radiation (CMBR) at 10.7 GHz to be TCMBR = 2.730 ± 0.014 K. The error is the quadratic sum of several systematic errors, with a statistical error of less than 0.1 mK. The instrument is made up of a cooled corrugated horn antenna coupled to a total power radiometer. A cryogenic mechanical waveguide switch alternately connects the radiometer to the horn and to an internal reference load. The small measured temperature difference (20 mK) between the sky signal and the reference load in conjunction with the use of a cold front end keeps systematic instrumental corrections small. Atmospheric and window emission are minimized by flying the instrument at 24 km altitude. A large outer ground screen and smaller inner screen shield the instrument from stray radiation from the ground and the balloon. In-flight tests constrain the magnitude of ground radiation contamination, and low-level interference is monitored through observations in several narrow-frequency bands.
15659295
The amplitude and spectral index of the large angular scale anisotropy in the cosmic microwave background radiation
In many cosmological models, the large angular scale anisotropy in the cosmic microwave background is parameterized by a spectral index, $n$, and a quadrupolar amplitude, $Q$. For a Peebles-Harrison-Zel'dovich spectrum, $n=1$. Using data from the Far Infra-Red Survey (FIRS) and a new statistical measure, a contour plot of the likelihood for cosmological models for which $-1 2.2$, as it is for $Q 44$.
17581520
SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP *) OBSERVATIONS: COSMOLOGICAL INTERPRETATION
The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H0) measurement, we determine the parameters of the simplest six-parameter ΛCDM model. The power-law index of the primordial power spectrum is ns = 0.968 ± 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison–Zel’dovich–Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, � mν < 0.58 eV (95% CL), and the effective number of neutrino species, Neff = 4.34 +0.86 −0.88 (68% CL), which benefit from better determinations of the third peak and H0. The limit on a constant dark energy equation of state parameter from WMAP+BAO+H0, without high-redshift Type Ia supernovae, is w =− 1.10 ± 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Yp = 0.326 ± 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature–E-mode polarization cross power spectrum at 21σ , compared with 13σ from the five-year data. With the seven-year temperature–B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to Δα =− 1. 1 ± 1. 4(statistical) ± 1. 5(systematic) (68% CL). We report significant detections of the Sunyaev–Zel’dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5–0.7 times the predictions from “universal profile” of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.
54619228
Joint reconstruction of galaxy clusters from gravitational lensing and thermal gas - I. Outline of a non-parametric method
We present a method to estimate the lensing potential from massive galaxy clusters for given observational X-ray data. The concepts developed and applied in this work can easily be combined with other techniques to infer the lensing potential, e.g. weak gravitational lensing or galaxy kinematics, to obtain an overall best fit model for the lensing potential. After elaborating on the physical details and assumptions the method is based on, we explain how the numerical algorithm itself is implemented with a Richardson-Lucy algorithm as a central part. Our reconstruction method is tested on simulated galaxy clusters with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium. We describe in detail how these simulated observational data sets are created and how they need to be fed into our algorithm. We test the robustness of the algorithm against small parameter changes and estimate the quality of the reconstructed lensing potentials. As it turns out we achieve a very high degree of accuracy in reconstructing the lensing potential. The statistical errors remain below 2.0% whereas the systematical error does not exceed 1.0%.
58908723
Reconstructing the projected gravitational potential of galaxy clusters from galaxy kinematics
We have developed a method for reconstructing the two-dimensional, projected gravitational potential of galaxy clusters from observed line-of-sight velocity dispersions of cluster galaxies. It is the second in an intended series of papers aiming at a unique reconstruction method for cluster potentials that combine lensing, X-ray, Sunyaev-Zel’dovich and kinematic data. The observed galaxy velocity dispersions are deprojected using the Richardson-Lucy algorithm. The obtained radial velocity dispersions are then related to the gravitational potential by using the tested assumption of a polytropic relation between the e ective galaxy pressure and the density. Once the gravitational potential is obtained in three dimensions, projection along the line of sight yields the two-dimensional potential. For simplicity we adopt spherical symmetry and a known profile for the anisotropy parameter of the galaxy velocity dispersions. We tested the method with a numerically simulated galaxy cluster and the galaxies identified therein and performed the reconstruction for three di erent lines of sight. We extracted a projected velocity-dispersion profile from the simulated cluster and passed it through our algorithm, showing that the deviation between the true and the reconstructed gravitational potential is< 10% within 1:5h 1 Mpc from the cluster centre.