Planck Surveyor Research Articles

Discrimination betweenΛCDM, quintessence, and modified gravity models using wide area surveys

In the past decade or so observations of supernovae, Large Scale Structures (LSS), and the Cosmic Microwave Background (CMB) have confirmed the presence of what is called dark energy - the cause of accelerating expansion of the Universe. They have also measured its density as well as the value of other cosmological parameters according to the concordance $\Lambda$CDM model with few percent uncertainties. Next generation of surveys should allow to constrain this model with better precisions, or distinguish between a LCDM and alternative models such as modified gravity and (interacting)-quintessence models. In this work we parametrize both homogeneous and anisotropic components of matter density in the context of interacting dark energy models with the goal of discriminating between f(R) modified gravity and its generalizations, and interacting dark energy models, for which we also propose a phenomenological description of energy-momentum conservation equations inspired by particle physics. It is based on the fact that the simplest interactions between particles/fields are elastic scattering and decay. The parametrization of growth rate proposed here is nonetheless general and can be used to constrain other interactions. As an example of applications, we present an order of magnitude estimation of the accuracy of the measurement of these parameters using Euclid and Planck surveys data, and leave a better estimation to a dedicated work.

On two low harmonics of CMB correlation maps

We have analyzed two powerful correlation harmonics (l = 3and l = 6) found in the correlation of the ILC WMAP signal with the submillimeter and infrared range data from the FSC IRAS and Planck catalogs. The mode phases of thesemultipoles were computed. In the spots we have found in the harmonics, the source counts were made from the NVSS, FIRST, FSC IRAS and Planck surveys. The correlation harmonic phases are close at different observational frequencies both for l = 3and l = 6.We do not exclude that a part of the weak signal in the ILCWMAP data, manifested in the strong correlation properties of the investigated multipoles may be due to extragalactic radiation sources.

HARMONIC IN-PAINTING OF COSMIC MICROWAVE BACKGROUND SKY BY CONSTRAINED GAUSSIAN REALIZATION

The presence of astrophysical emissions between the last scattering surface and our vantage point requires us to apply a foreground mask on CMB sky map, leading to large cut around the Galactic equator and numerous holes. Since many CMB analyses, including non-Gaussianity study may be performed on a whole sky map in a more straightforward and reliable manner, it is of utmost importance to develop an efficient method to in-paint the CMB sky map, while still preserving statistical properties. In this letter, we consider Monte-Carlo simulation of constrained Gaussian field and derive it for CMB anisotropy in harmonic space, where a feasible implementation is possible with good approximation. We applied our method to the simulated data, which confirms the masked area is in-painted in a way compliant with the expected statistical properties. Subsequently, we applied our method to the WMAP foreground-reduced maps and investigated the anomalous alignment between quadrupole and octupole components. From our investigation, we find the alignment in the foreground-reduced maps is even higher than the ILC map. In particular, we find the highest alignment in the V band map, which has less foreground contamination than other bands. Therefore, we find it hard to attribute the alignment to residual foregrounds. Our method will be complementary to other efforts on in-painting or reconstructing the masked CMB data, and of great use to Planck surveyor and future missions.

Planckearly results. IX.XMM-Newtonfollow-up for validation ofPlanckcluster candidates

We present the XMM-Newton follow-up for confirmation of Planck cluster candidates. Twenty-five candidates have been observed to date using snapshot (~10 ksec) exposures, ten as part of a pilot programme to sample a low range of signal-to-noise ratios (4<S/N<6), and a further 15 in a programme to observe a sample of S/N>5 candidates. The sensitivity and spatial resolution of XMM-Newton allows unambiguous discrimination between clusters and false candidates. The 4 false candidates have S/N <= 4.1. A total of 21 candidates are confirmed as extended X-ray sources. Seventeen are single clusters, the majority of which are found to have highly irregular and disturbed morphologies (about ~70%). The remaining four sources are multiple systems, including the unexpected discovery of a supercluster at z=0.45. For 20 sources we are able to derive a redshift estimate from the X-ray Fe K line (albeit of variable quality). The new clusters span the redshift range 0.09 <= z <= 0.54, with a median redshift of z~0.37. A first determination is made of their X-ray properties including the characteristic size, which is used to improve the estimate of the SZ Compton parameter, Y_SZ. The follow-up validation programme has helped to optimise the Planck candidate selection process. It has also provided a preview of the X-ray properties of these newly-discovered clusters, allowing comparison with their SZ properties, and to the X-ray and SZ properties of known clusters observed in the Planck survey. Our results suggest that Planck may have started to reveal a non-negligible population of massive dynamically perturbed objects that is under-represented in X-ray surveys. However, despite their particular properties, these new clusters appear to follow the Y_SZ-Y_X relation established for X-ray selected objects, where Y_X is the product of the gas mass and temperature.

Planckearly results. X. Statistical analysis of Sunyaev-Zeldovich scaling relations for X-ray galaxy clusters

All-sky data from the Planck survey and the Meta-Catalogue of X-ray detected Clusters of galaxies (MCXC) are combined to investigate the relationship between the thermal Sunyaev-Zeldovich (SZ) signal and X-ray luminosity. The sample comprises ~ 1600 X-ray clusters with redshifts up to ~ 1 and spans a wide range in X-ray luminosity. The SZ signal is extracted for each object individually, and the statistical significance of the measurement is maximised by averaging the SZ signal in bins of X-ray luminosity, total mass, or redshift. The SZ signal is detected at very high significance over more than two decades in X-ray luminosity (10^43 erg/s < L_500 E(z)^-7/3 < 2 X 10^45 erg/s). The relation between intrinsic SZ signal and X-ray luminosity is investigated and the measured SZ signal is compared to values predicted from X-ray data. Planck measurements and X-ray based predictions are found to be in excellent agreement over the whole explored luminosity range. No significant deviation from standard evolution of the scaling relations is detected. For the first time the intrinsic scatter in the scaling relation between SZ signal and X-ray luminosity is measured and found to be consistent with the one in the luminosity -- mass relation from X-ray studies. There is no evidence of any deficit in SZ signal strength in Planck data relative to expectations from the X-ray properties of clusters, underlining the robustness and consistency of our overall view of intra-cluster medium properties.

LACK OF ANGULAR CORRELATION AND ODD-PARITY PREFERENCE IN COSMIC MICROWAVE BACKGROUND DATA

We have investigated the angular correlation in the recent CMB data. In addition to the known large-angle correlation anomaly, we find the lack of correlation at small angles with high statistical significance. We have investigated various non-cosmological contamination and additionally WMAP team's simulated data. However, we have not found a definite cause. In the angular power spectrum of WMAP data, there exist anomalous odd-parity preference at low multipoles. Noting the equivalence between the power spectrum and the correlation, we have investigated the association between the lack of large-angle correlation and the odd-parity preference. From our investigation, we find that the odd-parity preference at low multipoles is, in fact, a phenomenological origin of the lack of large-angle correlation. Futher investigation is required to find out whether the origin of the anomaly is cosmological or due to unaccounted systematics. The data from Planck surveyor, which has systematics distinct from the WMAP, will greatly help us to resolve its origin.

Progress in Precision Measurements of the Cosmic Microwave Background

High precision measurements of the Cosmic Microwave Background (CMB) represent one of the most difficult challenges in observational cosmology, but promise to unveil the mysteries of the very early Universe and of the birth of structures. Three observables are available. The small polarized CMB signal is probably carrying a signature of the early inflationary dynamics of the Universe. It is, however, embedded in overwhelming noise, systematic effects, and polarized foreground. The imprint of the large scale structure in the universe is present in the small-scale anisotropy of the CMB and in its spectral signatures (secondary anisotropy), again mixed with foreground contaminants. Low-level non-Gaussian components of CMB anisotropy and polarization also provide a very promising way to constrain inflation and the physics of ultra-high energies, if foregrounds can be efficiently separated from the measured signal. If measured with high precision, as required by the science issues above, the spectra of CMB anisotropy and polarization also constrain efficiently neutrino properties, hence their interest in this conference. Here we summarize the current status of CMB measurements, dominated by the Planck survey, and delineate the forthcoming activities, needed to exploit the huge scientific potential of precision measurements of the CMB, including the detection of neutrino masses.

Constraining variations in the fine structure constant in the presence of early dark energy

We discuss present and future cosmological constraints on variations of the fine structure constant $\alpha$ induced by an early dark energy component having the simplest allowed (linear) coupling to electromagnetism. We find that current cosmological data show no variation of the fine structure constant at recombination respect to the present-day value, with $\alpha$ / $\alpha_0$ = 0.975 \pm 0.020 at 95 % c.l., constraining the energy density in early dark energy to $\Omega_e$ < 0.060 at 95 % c.l.. Moreover, we consider constraints on the parameter quantifying the strength of the coupling by the scalar field. We find that current cosmological constraints on the coupling are about 20 times weaker than those obtainable locally (which come from Equivalence Principle tests). However forthcoming or future missions, such as Planck Surveyor and CMBPol, can match and possibly even surpass the sensitivity of current local tests.

CROSS-CORRELATIONS OF THE Lyα FOREST WITH WEAK-LENSING CONVERGENCE. ANALYTICAL ESTIMATES OF SIGNAL-TO-NOISE RATIO AND IMPLICATIONS FOR NEUTRINO MASS AND DARK ENERGY

We expect a detectable correlation between two seemingly unrelated quantities: the four point function of the cosmic microwave background (CMB) and the amplitude of flux decrements in quasar (QSO) spectra. The amplitude of CMB convergence in a given direction measures the projected surface density of matter. Measurements of QSO flux decrements trace the small-scale distribution of gas along a given line-of-sight. While the cross-correlation between these two measurements is small for a single line-of-sight, upcoming large surveys should enable its detection. This paper presents analytical estimates for the signal to noise (S/N) for measurements of the cross-correlation between the flux decrement and the convergence and for measurements of the cross-correlation between the variance in flux decrement and the convergence. For the ongoing BOSS (SDSS III) and Planck surveys, we estimate an S/N of 30 and 9.6 for these two correlations. For the proposed BigBOSS and ACTPOL surveys, we estimate an S/N of 130 and 50 respectively. Since the cross-correlation between the variance in flux decrement and the convergence is proportional to the fourth power of $\sigma_8$, the amplitude of these cross-correlations can potentially be used to measure the amplitude of $\sigma_8$ at z~2 to 2.5% with BOSS and Planck and even better with future data sets. These measurements have the potential to test alternative theories for dark energy and to constrain the mass of the neutrino. The large potential signal estimated in our analytical calculations motivate tests with non-linear hydrodynamical simulations and analyses of upcoming data sets.

Probing hot gas in galaxy groups through the Sunyaev-Zeldovich effect

We investigate the potential of exploiting the Sunyaev-Zeldovich effect (SZE) to study the properties of hot gas in galaxy groups. It is shown that, with upcoming SZE surveys, one can stack SZE maps around galaxy groups of similar halo masses selected from large galaxy redshift surveys to study the hot gas in halos represented by galaxy groups. We use various models for the hot halo gas to study how the expected SZE signals are affected by gas fraction, equation of state, halo concentration, and cosmology. Comparing the model predictions with the sensitivities expected from the SPT, ACT and Planck surveys shows that a SPT-like survey can provide stringent constraints on the hot gas properties for halos with masses M ~> 10^{13} h^{-1}Msun. We also explore the idea of using the cross correlation between hot gas and galaxies of different luminosity to probe the hot gas in dark matter halos without identifying galaxy groups to represent dark halos. Our results show that, with a galaxy survey as large as the Sloan Digital Sky Survey and with the help of the conditional luminosity function (CLF) model, one can obtain stringent constraints on the hot gas properties in halos with masses down to 10^{13} h^{-1}Msun. Thus, the upcoming SZE surveys should provide a very promising avenue to probe the hot gas in relatively low-mass halos where the majority of L*-galaxies reside.

Digital complex correlator for a C-band polarimetry survey

The international Galactic Emission Mapping project aims to map and characterize the polarization field of the Milky Way. In Portugal it will cartograph the C-band sky polarized emission of the Northern Hemisphere and provide templates for map calibration and foreground control of microwave space probes like ESA Planck Surveyor mission. The receiver system is equipped with a novel receiver with a full digital back-end using an Altera Field Programmable Gate Array, having a very favorable cost/performance relation. This new digital backend comprises a base-band complex cross-correlator outputting the four Stokes parameters of the incoming polarized radiation. In this document we describe the design and implementation of the complex correlator using COTS components and a processing FPGA, detailing the method applied in the several algorithm stages and suitable for large sky area surveys.

Towards a complete treatment of the cosmological recombination problem

A new approach to the cosmological recombination problem is presented, which completes our previous analysis on the effects of two-photon processes during the epoch of cosmological hydrogen recombination, accounting for ns-1s and nd-1s Raman events and two-photon transitions from levels with n>=2. The recombination problem for hydrogen is described using an effective 400-shell multi-level approach, to which we subsequently add all important recombination corrections discussed in the literature thus far. We explicitly solve the radiative transfer equation of the Lyman-series photon field to obtain the required modifications to the rate equations of the resolved levels. In agreement with earlier computations we find that 2s-1s Raman scattering leads to a delay in recombination by DN_e/N_e~0.9% at z~920. Two-photon decay and Raman scattering from higher levels (n>3) result in a small additional modifications, and precise results can be obtained when including their effect for the first 3-5 shells. This work is a major step towards a new cosmological recombination code (CosmoRec) that supersedes the physical model included in Recfast, and which, owing to its short runtime, can be used in the analysis of future CMB data from the Planck Surveyor.

Anomalous parity asymmetry of WMAP 7-year power spectrum data at low multipoles: Is it cosmological or systematics?

We have investigated the odd-parity preference of the WMAP 7 year power spectrum. Comparison with simulation shows the odd-parity preference of WMAP data (2<= l <=22) is anomalous at 4-in-1000 level. We have investigated its origins, and ruled out some of non-cosmological origins such as asymmetric beams, noise and cut-sky effect. We also find primordial origin requires |Re[\Phi(\mathbf k)]|\ll|Im[\Phi(\mathbf k)]| for k\lesssim 22/\eta_0, where \eta_0 is the present conformal time. Multipoles associated with the odd-parity preference happen to coincide with some of other CMB anomalies. Therefore, there may exist a common origin, whether cosmological or not. Besides, we find it likely that low quadrupole power is the part of this odd-parity preference anomaly rather than an isolated one. The Planck surveyor, which possesses wide frequency coverage and systematics distinct from the WMAP, may allow us to resolve the mystery of the anomalous odd-parity preference.

Foreground removal from WMAP 5 yr temperature maps using an MLP neural network

One of the main obstacles for extracting the cosmic microwave background (CMB) signal from observations in the mm/sub-mm range is the foreground contamination by emission from Galactic component: mainly synchrotron, free-free, and thermal dust emission. The statistical nature of the intrinsic CMB signal makes it essential to minimize the systematic errors in the CMB temperature determinations. The feasibility of using simple neural networks to extract the CMB signal from detailed simulated data has already been demonstrated. Here, simple neural networks are applied to the WMAP 5yr temperature data without using any auxiliary data. A simple \emph{multilayer perceptron} neural network with two hidden layers provides temperature estimates over more than 75 per cent of the sky with random errors significantly below those previously extracted from these data. Also, the systematic errors, i.e.\ errors correlated with the Galactic foregrounds, are very small. With these results the neural network method is well prepared for dealing with the high - quality CMB data from the ESA Planck Surveyor satellite.

TENTATIVE DETECTION OF QUASAR FEEDBACK FROM WMAP AND SDSS CROSS-CORRELATION

ABSTRACT We perform a cross-correlation analysis of microwave data from the Wilkinson Microwave Anisotropy Probe and photometric quasars from the Sloan Digital Sky Survey, testing for the Sunyaev–Zeldovich (SZ) effect from quasars. A statistically significant (2.5σ) temperature decrement exists in the 41 GHz microwave band. A two-component fit to the cross-correlation spectrum incorporating both dust emission and SZ yields a best-fit y parameter of (7.0 ± 3.4) × 10−7. A similar cross-correlation analysis with the luminous red galaxy sample from Sloan gives a best-fit y parameter of (5.3 ± 2.5) × 10−7. We discuss the possible physical origin of these signals, which is likely a combination of SZ effects from quasars and galaxy clusters. Both the Planck Surveyor satellite and the current ground-based arcminute-resolution microwave experiments will detect this signal with a higher statistical significance.

ANOMALOUS PARITY ASYMMETRY OF THE WILKINSON MICROWAVE ANISOTROPY PROBE POWER SPECTRUM DATA AT LOW MULTIPOLES

We have investigated non-Gaussianity of our early Universe by comparing the parity asymmetry of the WMAP power spectrum with simulations. We find that odd-parity preference of the WMAP data (2<= l <=18) is anomalous at 4-in-1000 level. We find it likely that low quadrupole power is part of this parity asymmetry rather than an isolated anomaly. Futher investigation is required to find out whether the origin of this anomaly is cosmological or systematic effect. The data from Planck surveyor, which has systematics distinct from the WMAP, will help us to resolve the origin of the anomalous odd-parity preference.

Constraining the time variation of the coupling constants from cosmic microwave background: effect of ΛQCD

We investigate constraints on the time variation of the fine structure constant between the recombination epoch and the present epoch, Δα/α≡(αrec−αnow)/αnow, from cosmic microwave background (CMB) taking into account simultaneous variation of other physical constants, namely the electron mass me and the proton mass mp. In other words, we consider the variation of Yukawa coupling and the QCD scale ΛQCD in addition to the electromagnetic coupling. We clarify which parameters can be determined from CMB temperature anisotropy in terms of singular value decomposition. Assuming a relation among variations of coupling constants governed by a single scalar field (the dilaton), the 95 % confidence level (C.L.) constraint on Δα/α is found to be −8.28 × 10−3 < Δα/α < 1.81 × 10−3, which is tighter than the one obtained by considering only the change of α and me. We also obtain the constraint on the time variation of the proton-to-electron mass ratio μ≡mp/me to be −0.52 < Δμ/μ < 0.17 (95 % C.L.) under the same assumption. Finally, we also implement a forecast for constraints from the PLANCK survey.

The Herschel and Planck Space Telescopes

The European Space Agency launches in 2009 two flagship missions in the domain of submillimeter space astronomy. The Herschel Space Observatory is a common user facility featuring a 3.5 m aperture Cassegrain telescope passively cooled to 80 K. The Planck survey mission includes a 1.5 m unobscured aperture off-axis aplanatic telescope passively cooled to 40 K. Herschel will make pointed target observations of astrophysical objects and phenomena in the frequency range 448 GHz to 5.3 THz (or 672 to 55 mum wavelength). Planck, on the other hand, will map the entire sky by strip scanning at a spin rate of one revolution per minute covering a frequency bandwidth of 30-857 GHz (or wavelength from 10 to 0.35 mm). Its spin axis is pointed antisunward and can be oriented within a 10deg cone around that direction. The telescope line of sight is fixed at an angle of 85 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> to the spacecraft spin-axis. This paper describes briefly the specific telescopes developed for each mission; their design characteristics, the development process for each, their achieved performances (from on ground testing) and their expected performances in flight.

Signals from the epoch of cosmological recombination – Karl Schwarzschild Award Lecture 2008

AbstractThe physical ingredients to describe the epoch of cosmological recombination are amazingly simple and well‐understood. This fact allows us to take into account a very large variety of physical processes, still finding potentially measurable consequences for theenergy spectrumandtemperature anisotropiesof the Cosmic Microwave Background (CMB). In this contribution we provide a short historical overview in connection with the cosmological recombination epoch and its connection to the CMB. Also we highlight some of the detailed physics that were studied over the past few years in the context of the cosmological recombination ofhydrogenandhelium. The impact of these considerations is two‐fold:(i) The associated release of photons during this epoch leads to interesting andunique deviationsof the CosmicMicrowave Background (CMB) energy spectrumfrom a perfect blackbody, which, in particular at decimeter wavelength and the Wien part of the CMB spectrum, may become observable in the near future. Despite the fact that the abundance of helium is rather small, it still contributes a sizeable amount of photons to the full recombination spectrum, leading to additional distinct spectral features. Observing the spectral distortions from the epochs of hydrogen and helium recombination, in principle would provide an additional way to determine some of the key parameters of the Universe (e.g. the specific entropy, the CMB monopole temperature and the pre‐stellar abundance of helium). Also it permits us to confront our detailed understanding of the recombination process withdirect observational evidence. In this contribution we illustrate how the theoreticalspectral templateof the cosmological recombination spectrum may be utilized for this purpose. We also show that because hydrogen and helium recombine at very different epochs it is possible to address questions related to thethermal historyof our Universe. In particular the cosmological recombination radiation may allow us to distinguish between Comptony‐distortions that were created by energy releasebeforeorafterthe recombination of the Universe finished.(ii) With the advent of high precision CMB data, e.g. as will be available using the PLANCK Surveyor or CMBPOL, a very accurate theoretical understanding of theionization historyof the Universe becomes necessary for the interpretation of the CMB temperature and polarization anisotropies. Here we show that the uncertainty in the ionization history due to several processes, which until now were not taken in to account in the standard recombination code RECFAST, reaches the percent level. In particular He II → He I recombination occurs significantly faster because of the presence of a tiny fraction of neutral hydrogen atz∼ 2400. Also recently it was demonstrated that in the case of H I Lymanαphotons thetimedependenceof the emission process and theasymmetrybetween the emission and absorption profile cannot be ignored. However, it is indeed surprising howinertthe cosmological recombination history is even at percent‐level accuracy. Observing the cosmological recombination spectrum should in principle allow us to directly check this conclusion, which until now is purely theoretical. Also it may allow toreconstruct the ionization historyusing observational data (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Cosmological hydrogen recombination: influence of resonance and electron scattering

In this paper we consider the effects of resonance and electron scattering on the escape of Lyman alpha photons during cosmological hydrogen recombination. We pay particular attention to the influence of atomic recoil, Doppler boosting and Doppler broadening using a Fokker-Planck approximation of the redistribution function describing the scattering of photons on the Lyman alpha resonance of moving hydrogen atoms. We extend the computations of our recent paper on the influence of the 3d/3s-1s two-photon channels on the dynamics of hydrogen recombination, simultaneously including the full time-dependence of the problem, the thermodynamic corrections factor, leading to a frequency-dependent asymmetry between the emission and absorption profile, and the quantum-mechanical corrections related to the two-photon nature of the 3d/3s-1s emission and absorption process on the exact shape of the Lyman alpha emission profile. We show here that due to the redistribution of photons over frequency hydrogen recombination is sped up by DN_e/N_e~-0.6% at z~900. For the CMB temperature and polarization power spectra this results in |DC_l/C_l|~0.5%-1% at l >~ 1500, and therefore will be important for the analysis of future CMB data in the context of the PLANCK Surveyor, SPT and ACT. The main contribution to this correction is coming from the atomic recoil effect (DN_e/N_e~-1.2% at z~900), while Doppler boosting and Doppler broadening partially cancel this correction, again slowing hydrogen recombination down by DN_e/N_e~0.6% at z~900. The influence of electron scattering close to the maximum of the Thomson visibility function at z~1100 can be neglected. (abridged)