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Register a new userConstraints in Cosmological Parameter Space from the Sunyaev-Zeldovich Effect and Thermal Bremsstrahlung
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We discuss how the space of possible cosmological parameters is constrained by the angular diameter distance function, D_A(z), as measured using the SZ/X-ray method which combines Sunyaev-Zeldovich (SZ) effect and X-ray brightness data for clusters of galaxies. New X-ray satellites, and ground-based interferometers dedicated to SZ observations, should soon lead to D_A(z) measurements limited by systematic rather than random error. We analyze the systematic and random error budgets to make a realistic estimate of the accuracy achievable in the determination of (Omega_m,Lambda,h), the density parameters of matter and cosmological constant, and the dimensionless Hubble constant, using D_A(z) derived from the SZ/X-ray method, and the position of the first ``Doppler peak in the cosmic microwave background fluctuations. We briefly study the effect of systematic errors. We find that Omega_m, Lambda, and w are affected, but h is not by systematic errors which grow with redshift. With as few as 70 clusters, each providing a measurement of D_A(z) with a 7% random and 5% systematic error, Omega_m can be constrained to +/-0.2, Lambda to +/-0.2, and h to +/-0.11 (all at 3 sigma). We also estimate constraints for the alternative three-parameter set (Omega_m,w,h), where w is the equation of state parameter. The measurement of D_A(z) provides constraints complementary to those from the number density of clusters in redshift space. A sample of 70 clusters (D_A measured with the same accuracy as before) combined with cluster evolution results (or a known matter density), can constrain w within +/-0.45 (at 3 sigma). Studies of X-ray and SZ properties of clusters of galaxies promise an independent and powerful test for cosmological parameters.
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We propose a new analysis of small scale CMB data by introducing the cosmological dependency of the foreground signals, focusing first on the thermal Sunyaev-Zeldovich (tSZ) power spectrum, derived from the halo model. We analyse the latest observations by the South Pole Telescope (SPT) of the high-$ell$ power (cross) spectra at 90, 150 and 220 GHz, as the sum of CMB and tSZ signals, both depending on cosmological parameters, and remaining contaminants. In order to perform faster analyses, we propose a new tSZ modelling based on machine learning algorithms (namely Random Forest). We show that the additional information contained in the tSZ power spectrum tightens constraints on cosmological and tSZ scaling relation parameters. We combine for the first time the Planck tSZ data with SPT high-$ell$ to derive even stronger constraints. Finally, we show how the amplitude of the remaining kSZ power spectrum varies depending on the assumptions made on both tSZ and cosmological parameters.
We review recent results of Sunyaev-Zeldovich effect (SZE) observations toward galaxy clusters. Using cm-wave receivers mounted on the OVRO and BIMA mm-wave arrays we have obtained high signal to noise images of the effect for more than 20 clusters. We present current estimates of the Hubble constant and cosmological parameters and discuss the potential of conducting statistical studies with large SZE cluster samples.
Sensitive surveys of the Cosmic Microwave Background will detect thousands of galaxy clusters via the Sunyaev-Zeldovich (SZ) effect. Two SZ observables, the central or maximum and integrated Comptonization parameters y_max and Y, relate in a simple way to the total cluster mass, which allow the construction of mass functions (MFs) that can be used to estimate cosmological parameters such as Omega_M, sigma_8, and the dark energy parameter w. However, clusters form from the mergers of smaller structures, events that can disrupt the equilibrium of intracluster gas upon which SZ-M relations rely. From a set of N-body/hydrodynamical simulations of binary cluster mergers, we calculate the evolution of Y and y_max over the course of merger events and find that both parameters are transiently boosted, primarily during the first core passage. We then use a semi-analytic technique developed by Randall et al. (2002) to estimate the effect of merger boosts on the distribution functions YF and yF of Y and y_max, respectively, via cluster merger histories determined from extended Press-Schechter (PS) merger trees. We find that boosts do not induce an overall systematic effect on YFs, and the values of Omega_M, sigma_8, and w were returned to within 2% of values expected from the nonboosted YFs. The boosted yFs are significantly biased, however, causing Omega_M to be underestimated by 15-45%, sigma_8 to be overestimated by 10-25%, and w to be pushed to more negative values by 25-45%. We confirm that the integrated SZ effect, Y, is far more robust to mergers than y_max, as previously reported by Motl et al. (2005) and similarly found for the X-ray equivalent Y_X, and we conclude that Y is the superior choice for constraining cosmological parameters.
Thermal Sunyaev-Zeldovich effect is one of the recent probes of cosmology and large scale structures. We update constraints on cosmological parameters from galaxy clusters observed by the Planck satellite in a first attempt to combine cluster number counts and power spectrum of hot gas, using the new value of the optical depth, and sampling at the same time on cosmological and scaling-relation parameters. We find that in the $Lambda$CDM model, the addition of tSZ power spectrum provides only small improvements with respect to number counts only, leading to the $68%$ c.l. constraints $Omega_m = 0.32 pm 0.02$, $sigma_8 = 0.77pm0.03 $ and $sigma_8 (Omega_m/0.3)^{1/3}= 0.78pm0.03$ and lowering the discrepancy with CMB primary anisotropies results (updated with the new value of $tau$) to $simeq 1.6, sigma$ on $sigma_8$. We analyse extensions to standard model, considering the effect of massive neutrinos and varying the equation of state parameter for dark energy. In the first case, we find that the addition of tSZ power spectrum helps in strongly improving cosmological constraints with respect to number counts only results, leading to the $95%$ upper limit $sum m_{ u}< 1.53 , text{eV}$. For the varying dark energy EoS scenario, we find again no important improvements when adding tSZ power spectrum, but still the combination of tSZ probes is able in providing constraints, producing $w = -1.0pm 0.2$. In all cosmological scenari the mass bias to reconcile CMB and tSZ probes remains low: $(1-b)lesssim 0.66$ as compared to estimates from weak lensing and Xray mass estimate comparisons or numerical simulations.
We estimate the amount of the {it missing baryons} detected by the Planck measurements of the cosmic microwave background in the direction of Central Galaxies (CGs) identified in the Sloan galaxy survey. The peculiar motion of the gas inside and around the CGs unveils values of the Thomson optical depth $tau_{rm T}$ in the range $0.2$--$2times 10^{-4}$, indicating that the regions probed around CGs contain roughly half of the total amount of baryons in the Universe at the epoch where the CGs are found. If baryons follow dark matter, the measured $tau_{rm T}$s are compatible with the detection all the baryons existing inside and around the CGs.
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