Separation of foregrounds from cosmic microwave background observations with the MAP satellite

We apply the iterative expectation-maximization algorithm (EM) to estimate the power spectrum of the cosmic microwave background (CMB) from multifrequency microwave maps. In addition, we are also able to provide a reconstruction of the CMB map. By assuming that the combined emission of the foregrounds plus the instrumental noise is Gaussian distributed in Fourier space, we have simplified the EM procedure, finding an analytical expression for the maximization step. By using the simplified expression, the CPU time can be greatly reduced. We test the stability of our power spectrum estimator with realistic simulations of Planck data, including point sources and allowing for spatial variation of the frequency dependence of the Galactic emissions. Without prior information about any of the components, our new estimator can recover the CMB power spectrum up to scales l≈ 1500 with less than 10 per cent error. This result is significantly improved if the brightest point sources are removed before applying our estimator. In this way, the CMB power spectrum can be recovered up to l≈ 1700 with 10 per cent error and up to l≈ 2100 with 50 per cent error. This result is very close to the one that would be obtained in the ideal case of only CMB plus white noise, for which all our assumptions are satisfied. Moreover, the EM algorithm also provides a straightforward mechanism for reconstructing the CMB map. The recovered cosmological signal shows a high degree of correlation (r= 0.98) with the input map and low residuals.

Residual foreground contamination in cosmic microwave background (CMB) maps, such as the residual contamination from thermal Sunyaev-Zeldovich (SZ) effect in the direction of galaxy clusters, can bias the cross-correlation measurements between CMB and large-scale structure optical surveys. It is thus essential to quantify those residuals and, if possible, to null out SZ cluster residuals in CMB maps. We quantify for the first time the amount of SZ cluster contamination in the released Planck 2015 CMB maps through (i) the stacking of CMB maps in the direction of the clusters, and (ii) the computation of cross-correlation power spectra between CMB maps and the SDSS-IV large-scale structure data. Our cross-power spectrum analysis yields a $30\sigma$ detection at the cluster scale ($\ell=1500-2500$) and a $39\sigma$ detection on larger scales ($\ell=500-1500$) due to clustering of SZ clusters, giving an overall $54\sigma$ detection of SZ cluster residuals in the Planck CMB maps. The Planck 2015 NILC CMB map is shown to have $44\pm4\%$ of thermal SZ foreground emission left in it. Using the 'Constrained ILC' component separation technique, we construct an alternative Planck CMB map, the 2D-ILC map, which is shown to have negligible SZ contamination, at the cost of being slightly more contaminated by Galactic foregrounds and noise. We also discuss the impact of the SZ residuals in CMB maps on the measurement of the ISW effect, which is shown to be negligible based on our analysis.

Clusters of galaxies can distort the cosmological signal in the cosmic microwave background (CMB) temperature fluctuations maps through the Sunyaev-Zel'dovich (SZ) effect. The analysis of this effect, which depends on the properties of the cluster population and its spatial distribution, could therefore be used to constrain the cluster mass function and its evolution. We present the global SZ effect expected for a cluster population extending to z = 0.2, z = 0.5, and z = 0.8, for random and nonrandom spatial distributions. The local population (up to z = 0.2) was built according to current results and in agreement with the XBACs data for the high-mass fraction of the cluster mass distribution. The resulting signal from the global SZ effect is well under the noise level of the Wilkinson Microwave Anisotropy Probe (WMAP) data for both distributions. The extension of the population to higher redshifts was done keeping the same mass distribution (without evolution). For the Poissonian distribution only at multipoles l ≥ 300 in the z = 0.8 case, the effects are over the noise level of the WMAP data. However, for the more realistic, nonrandom distribution case that signal would be detectable in the WMAP maps for multipoles higher than l = 100 at z = 0.5 and for nearly all multipoles at z = 0.8, in clear conflict with the data. The analysis of high-quality CMB data, as those expected from the Planck mission, will allow us to determine the contribution from the cluster population and to determine the evolution of clusters even at low redshift.

We use here a family of scaling transformations, that scale key rates in the evolution equations, to analytically understand constraints on light relics from cosmic microwave background (CMB) maps, given cosmological models of varying degrees of complexity. We describe the causes of physical effects that are fundamentally important to the constraining power of the data, with a focus on the two that are most novel. We use as a reference model a cosmological model that admits a scaling transformation that increases light relic energy density while avoiding all of these causes. Constraints on light relics in a given model can then be understood as due to the differences between the given model and the reference model, as long as the additional light relics only interact gravitationally with the Standard Model components. This understanding supports the development of cosmological models that can evade light relics constraints from CMB maps.

The intergalactic neutral hydrogen, which is responsible for the Ly alpha forest of quasar absorption lines, is a tracer of much larger amounts of ionized hydrogen. The ionized component has yet to be detected directly, but is expected to scatter cosmic microwave background (CMB) photons via the Sunyaev-Zel'dovich effect. We use hydrodynamic simulations of a Lambda cold dark matter (CDM) universe to create mock quasar spectra and CMB sky maps from the same volume of space. We find that the high-redshift Ly alpha forest gas causes temperature fluctuations of the order of 1 mu K rms in the CMB on arcmin scales. The kinetic and thermal Sunyaev-Zel'dovich effects have a similar magnitude at redshift 3, with the thermal effect becoming relatively weaker as expected at higher redshift. The CMB signal associated with lines of sight having H I column densities > 10(18) cm(-2) is only marginally stronger than that for lower column density sightlines. There is a much more significant dependence of rms temperature fluctuation on mean Ly alpha absorbed flux, however, suggesting that the CMB signal effectively arises in lower density material. We investigate the extent to which it is possible to cross-correlate information from the Ly alpha forest and the microwave background to detect the Sunyaev-Zel'dovich effect at redshifts 2-4. In so doing, we are able to set direct limits on the density of diffuse ionized intergalactic baryons. We carry out a preliminary comparison at a mean redshift z = 3 of 3488 quasar spectra from Sloan Digital Sky Survey (SDSS) Data Release 3 and the WMAP first year data. Assuming that the baryons are clustered as in a Lambda CDM cosmology, and have the same mean temperature, the cross-correlation yields a weak limit on the cosmic density of ionized baryons Omega(b,I). As a fraction of the critical density, we find Omega(b,I) < 0.8 at 95 per cent confidence. With data from upcoming CMB telescopes, we anticipate that a direct detection of the high-redshift ionized intergalactic medium will soon be possible, providing an important consistency check on cosmological models.

As cosmic microwave background (CMB) photons traverse the universe, anisotropies can be induced via Thomson scattering (proportional to the electron density; optical depth) and inverse Compton scattering (proportional to the electron pressure; thermal Sunyaev–Zel’dovich effect). Measurements of anisotropy in optical depth τ and Compton y parameters are imprinted by the galaxies and galaxy clusters and are thus sensitive to the thermodynamic properties of the circumgalactic medium and intergalactic medium. We use an analytic halo model to predict the power spectrum of the optical depth (τ τ), the cross-correlation between the optical depth and the Compton y parameter (τ y), and the cross-correlation between the optical depth and galaxy clustering (τ g), and compare this model to cosmological simulations. We constrain the optical depths of halos at z ≲ 3 using a technique originally devised to constrain patchy reionization at a higher redshift range. The forecasted signal-to-noise ratio is 2.6, 8.5, and 13, respectively, for a CMB-S4-like experiment and a Vera C. Rubin Observatory–like optical survey. We show that a joint analysis of these probes can constrain the amplitude of the density profiles of halos to 6.5% and the pressure profiles to 13%. These constraints translate to astrophysical parameters, such as the gas mass fraction, f g, which can be constrained to 5.3% uncertainty at z ∼ 0. The cross-correlations presented here are complementary to other CMB and galaxy cross-correlations since they do not require spectroscopic galaxy redshifts and are another example of how such correlations are a powerful probe of the astrophysics of galaxy evolution.

It is now well known that mode-coupling effects associated with certain secondary effects generate higher order correlations in cosmic microwave background (CMB) temperature anisotropies, beyond the two-point function. In order to extract such a non-Gaussian signal at the three-point level, we suggest a two-point statistic in the form of an angular power spectrum involving correlations between squared temperature and temperature anisotropies. This power spectrum contains compressed information from the bispectrum and can be easily measured in data with the same techniques that have been considered for the measurement of the usual temperature-temperature anisotropy power spectrum. We study the proposed power spectrum resulting from the non-Gaussian signal generated by correlations involved with gravitational lensing angular deflections in CMB and the Sunyaev-Zel’dovich (SZ) effect due to large scale pressure fluctuations. Using the Planck frequency cleaned CMB and SZ maps, the CMB2-SZ power spectrum provides a direct estimate of the cross-power between lensing angular deflections and the SZ effect. Through an optimal filter applied to the squared CMB map, the proposed statistic allows one to obtain all information from the lensing-SZ bispectrum. The observational measurement of the lensing-SZ cross-correlation is useful to understand the relation between large scale structure pressure and dark matter fluctuations.

We present new constraints on the relativistic neutrino effective number ${N}_{\mathrm{eff}}$ and on the cosmic microwave background power spectrum lensing amplitude ${A}_{\mathrm{L}}$ from the recent Planck 2013 data release. Including observations of the cosmic microwave background large angular scale polarization from the Wilkinson microwave anisotropy probe (WMAP) satellite, we obtain the bounds ${N}_{\mathrm{eff}}=3.71\ifmmode\pm\else\textpm\fi{}0.40$ and ${A}_{\mathrm{L}}=1.25\ifmmode\pm\else\textpm\fi{}0.13$ at 68% C.L. We discuss the agreement of these results with the previous constraints obtained from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT). Considering the constraints on the cosmological parameters, we found a very good agreement with the previous $\mathrm{WMAP}+\mathrm{SPT}$ analysis but a tension with the $\mathrm{WMAP}+\mathrm{ACT}$ results, with the only exception of the lensing amplitude.

We perform a blind multicomponent analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) 1-yr foreground-cleaned maps using Spectral Matching Independent Component Analysis (smica). We provide a new estimate of the cosmic microwave background (CMB) power spectrum as well as the amplitude of the CMB anisotropies across frequency channels. We show that the CMB anisotropies are compatible with temperature fluctuations as expected from the standard paradigm. The analysis also allows us to identify and separate a weak residual Galactic emission, present significantly in the Q band outside of the Kp21 mask limits, and mainly concentrated at low Galactic latitudes. We produce a map of this residual component by Wiener filtering using estimated parameters. The level of contamination of CMB data by this component is compatible with the WMAP-team estimation of foreground residual contamination. In addition, the multicomponent analysis allows us to estimate jointly the power spectrum of unresolved point-source emission.

The Rayleigh scattering of cosmic microwave background (CMB) photons off the neutral hydrogen produced during recombination effectively creates an additional scattering surface after recombination that encodes new cosmological information, including the expansion and ionization history of the universe. A first detection of Rayleigh scattering is a tantalizing target for next-generation CMB experiments. We have developed a Rayleigh scattering forecasting pipeline that includes instrumental effects, atmospheric noise, and astrophysical foregrounds (e.g., Galactic dust, cosmic infrared background, or CIB, and the thermal Sunyaev-Zel'dovich effect). We forecast the Rayleigh scattering detection significance for several upcoming ground-based experiments, including $\mathrm{SPT}\text{\ensuremath{-}}3\mathrm{G}+$, Simons Observatory, CCAT-prime, and CMB-S4, and examine the limitations from atmospheric and astrophysical foregrounds as well as potential mitigation strategies. When combined with Planck data, we estimate that the ground-based experiments will detect Rayleigh scattering with a significance between 1.6 and 3.7, primarily limited by atmospheric noise and the CIB.

The cosmic microwave background (CMB), carrying the inhomogeneous information of the very early universe, is of great significance for understanding the origin and evolution of our universe. However, observational CMB maps contain serious foreground contaminations from several sources, such as Galactic synchrotron and thermal dust emissions. Here, we build a deep convolutional neural network (CNN) to recover the tiny CMB signal from various huge foreground contaminations. Focusing on CMB temperature fluctuations, we find that the CNN model can successfully recover the CMB temperature maps with high accuracy, and that the deviation of the recovered power spectrum C ℓ is smaller than the cosmic variance at ℓ > 10. We then apply this method to the current Planck observations, and find that the recovered CMB is quite consistent with that disclosed by the Planck Collaboration, which indicates that the CNN method can provide a promising approach to the component separation of CMB observations. Furthermore, we test the CNN method with simulated CMB polarization maps based on the CMB-S4 experiment. The result shows that both the EE and BB power spectra can be recovered with high accuracy. Therefore, this method will be helpful for the detection of primordial gravitational waves in current and future CMB experiments. The CNN is designed to analyze two-dimensional images, thus this method is not only able to process full-sky maps, but also partial-sky maps. Therefore, it can also be used for other similar experiments, such as radio surveys like the Square Kilometer Array.

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 clearly 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 {\Lambda}CDM 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.

H olding his 3-month-old son, Joshua, in his arms, cosmologist David N. Spergel will proudly watch the launch next week of a NASA satellite that he helped father. The satellite will record the remnant glow from the infant universe in greater detail than ever before. Even before the Microwave Anisotropy Probe satellite gets off the ground, however, Spergel and his colleagues have hatched a plan to examine that early light in a dramatically different way. The satellite will continue the practice of treating the cosmic microwave background (CMB)-the glow left over from the Big Bang-as a snapshot of the early universe. Taking a new perspective, Spergel and his colleagues propose to use that radiation as a flashlight to illuminate the evolution of structure in the universe over its 13-billion-year history. That evolution began with the condensation of gas clouds into fledgling galaxies and continued with production of the first stars and the assembly of galaxies into mammoth clusters. To realize this ambitious idea, Spergel and several other astronomers intend to examine the subtle markings acquired by the CMB as it traversed billions of lightyears to reach Earth. Like a weary traveler who has picked up dust from each country he's visited, the microwave background has been marked by all the cosmic architecture that it has encountered. As it streams across the universe, the CMB lighting up the past between here and there, says Spergel, who is based at Princeton University. The photons in the CMB have been traveling freely through space ever since the universe was about 300,000 years old. And a lot of things happened to them along the way, Spergel notes You have lots of imprints on the microwave background from the emergence of structure. Those imprints show up on a much finer scale than that of the primordial features painted onto the CMB by the Big Bang itself. Those relatively large hot and cold spots in the CMB, which the spaceborne Microwave Anisotropy Probe will detect, represent the seeds from which galaxies and galaxy clusters ultimately arose. Galaxies and galaxy clusters buffet the CMB photons coursing through them. These interactions generate hot and cold spots that differ by only a millionth of a degree or so from the average temperature of the microwave background, a chilly 2.76 kelvins. That's one-tenth as small as the temperature fluctuations imprinted on the CMB by the tumultuous conditions in the nascent universe. The tinier, post-Big Bang variations also occur on spatial scales only one-third the size of the primordial hot and cold spots that the Microwave Anisotropy Probe can discern. The sensitive detectors required to study these tiny variations, which theo-

The Sunyaev‐Zel’dovich (SZ) effect is a direct probe of thermal energy content of the Universe, induced in the cosmic microwave background (CMB) sky through scattering of CMB photons off hot electrons in the intracluster medium (ICM). We report a 9σ detection of the SZ signal in the CMB maps of Wilkinson Microwave Anisotropy Probe (WMAP) three-year data, through study of a sample of 193 massive galaxy clusters with observed X-ray temperatures greater than 3 keV. For the first time, we make a model-independent measurement of the pressure profile in the outskirts of the ICM, and show that it closely follows the profiles obtained by X-ray observations and numerical simulations. We find that our measurements of the SZ effect would account for only half of the thermal energy of the cluster, if all the cluster baryons were in the hot ICM phase. Our measurements indicate that a significant fraction, 35 ± 8 per cent, of baryonic mass is missing from the hot ICM, and thus must have cooled to form galaxies, intracluster stars, or an unknown cold phase of the ICM. There does not seem to be enough mass in the form of stars or cold gas in the cluster galaxies or intracluster space, signalling the need for a yet-unknown baryonic component (at 3σ level), or otherwise new astrophysical processes in the ICM.

Accurate measurements of the angular power spectrum of cosmic microwave background (CMB) radiation have lead to a marked improvement in the estimates of different cosmological parameters. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. We present the estimation of the CMB angular power spectrum from the multifrequency observations of the Wilkinson Microwave Anisotropy Probe (WMAP) using a novel model-independent method. The primary results of WMAP are the observations of the CMB in 10 independent difference assemblies (DAs) that have uncorrelated noise. Our method utilizes the maximum information available within the WMAP data by linearly combining all the DA maps in order to remove foreground contamination and by estimating the power spectrum from cross-power spectra of clean maps with independent noise. We compute 24 cross-power spectra that are the basis of the final power spectrum. The binned average power matches the WMAP team's published power spectrum closely. A small systematic difference at large multipoles is accounted for by the correction for the expected residual power from unresolved point sources. The correction is small and significantly tempered. Previous estimates have depended on foreground templates built using extraneous observational input. This is the first demonstration that the CMB angular spectrum can be reliably estimated with precision from a self-contained analysis of the WMAP data.