Improved Dark Energy Detection through the Polarization-assisted WMAP-NVSS ISW Correlation

Integrated Sachs-Wolfe (ISW) effect can be estimated by cross-correlating Cosmic Microwave Background (CMB) sky with tracers of the local matter distribution. At late cosmic time, the dark energy induced decay of gravitation potential generates a cross-correlation signal on large angular scales. The dominant noise are the intrinsic CMB anisotropies from the inflationary epoch. In this Letter we use CMB polarization to reduce this intrinsic noise. We cross-correlate the microwave sky observed by Wilkinson Microwave Anisotropy Probe (WMAP) with the radio source catalog compiled by NRAO VLA Sky Survey (NVSS) to study the efficiency of the noise suppression . We find that the error bars are reduced about 5-12 %, improving the statistical power.Comment: 10 pages, 2 figure

Generating Cosmological Gaussian Random Fields

We present a generic algorithm for generating Gaussian random initial conditions for cosmological simulations on periodic rectangular lattices. We show that imposing periodic boundary conditions on the real-space correlator and choosing initial conditions by convolving a white noise random field results in a significantly smaller error than the traditional procedure of using the power spectrum. This convolution picture produces exact correlation functions out to separations of L/2, where L is the box size, which is the maximum theoretically allowed. This method also produces tophat sphere fluctuations which are exact at radii $R \le L/4$. It is equivalent to windowing the power spectrum with the simulation volume before discretizing, thus bypassing sparse sampling problems. The mean density perturbation in the volume is no longer constrained to be zero, allowing one to assemble a large simulation using a series of smaller ones. This is especially important for simulations of Lyman-$\alpha$ systems where small boxes with steep power spectra are routinely used. We also present an extension of this procedure which generates exact initial conditions for hierarchical grids at negligible cost.Comment: 12 pages incl 3 figures, accepted in ApJ Letter

The Cosmic Microwave Background & Inflation, Then & Now

Boomerang, Maxima, DASI, CBI and VSA significantly increase the case for accelerated expansion in the early universe (the inflationary paradigm) and at the current epoch (dark energy dominance), especially when combined with data on high redshift supernovae (SN1) and large scale structure (LSS). There are ``7 pillars of Inflation'' that can be shown with the CMB probe, and at least 5, and possibly 6, of these have already been demonstrated in the CMB data: (1) a large scale gravitational potential; (2) acoustic peaks/dips; (3) damping due to shear viscosity; (4) a Gaussian (maximally random) distribution; (5) secondary anisotropies; (6) polarization. A 7th pillar, anisotropies induced by gravity wave quantum noise, could be too small. A minimal inflation parameter set, \omega_b,\omega_{cdm}, \Omega_{tot}, \Omega_Q,w_Q,n_s,\tau_C, \sigma_8}, is used to illustrate the power of the current data. We find the CMB+LSS+SN1 data give \Omega_{tot} =1.00^{+.07}_{-.03}, consistent with (non-baroque) inflation theory. Restricting to \Omega_{tot}=1, we find a nearly scale invariant spectrum, n_s =0.97^{+.08}_{-.05}. The CDM density, \Omega_{cdm}{\rm h}^2 =.12^{+.01}_{-.01}, and baryon density, \Omega_b {\rm h}^2 = >.022^{+.003}_{-.002}, are in the expected range. (The Big Bang nucleosynthesis estimate is 0.019\pm 0.002.) Substantial dark (unclustered) energy is inferred, \Omega_Q \approx 0.68 \pm 0.05, and CMB+LSS \Omega_Q values are compatible with the independent SN1 estimates. The dark energy equation of state, crudely parameterized by a quintessence-field pressure-to-density ratio w_Q, is not well determined by CMB+LSS (w_Q < -0.4 at 95% CL), but when combined with SN1 the resulting w_Q < -0.7 limit is quite consistent with the w_Q=-1 cosmological constant case.Comment: 20 pages, 8 figures, in Theoretical Physics, MRST 2002: A Tribute to George Libbrandt (AIP), eds. V. Elias, R. Epp, R. Myer

A Causal Source which Mimics Inflation

How unique are the inflationary predictions for the cosmic microwave anisotropy pattern? In this paper, it is asked whether an arbitrary causal source for perturbations in the standard hot big bang could effectively mimic the predictions of the simplest inflationary models. A surprisingly simple example of a `scaling' causal source is found to closely reproduce the inflationary predictions. This letter extends the work of a previous paper (ref. 6) to a full computation of the anisotropy pattern, including the Sachs Wolfe integral. I speculate on the possible physics behind such a source.Comment: 4 pages, RevTex, 3 figure

Recovery of the Shape of the Mass Power Spectrum from the Lyman-alpha Forest

We propose a method for recovering the shape of the mass power spectrum on large scales from the transmission fluctuations of the Lyman-alpha forest, which takes into account directly redshift-space distortions. The procedure, in discretized form, involves the inversion of a triangular matrix which projects the mass power spectrum in 3-D real-space to the transmission power spectrum in 1-D redshift-space. We illustrate the method by performing a linear calculation relating the two. A method that does not take into account redshift-space anisotropy tends to underestimate the steepness of the mass power spectrum, in the case of linear distortions. The issue of the effective bias-factor for the linear distortion kernel is discussed.Comment: 18 pages, 4 figures; minor revision

The Sunyaev Zel'dovich effect: simulation and observation

The Sunyaev Zel'dovich effect (SZ effect) is a complete probe of ionized baryons, the majority of which are likely hiding in the intergalactic medium. We ran a $512^3$ $\Lambda$CDM simulation using a moving mesh hydro code to compute the statistics of the thermal and kinetic SZ effect such as the power spectra and measures of non-Gaussianity. The thermal SZ power spectrum has a very broad peak at multipole $l\sim 2000-10^4$ with temperature fluctuations $\Delta T \sim 15\mu$K. The power spectrum is consistent with available observations and suggests a high $\sigma_8\simeq 1.0$ and a possible role of non-gravitational heating. The non-Gaussianity is significant and increases the cosmic variance of the power spectrum by a factor of $\sim 5$ for $l<6000$. We explore optimal driftscan survey strategies for the AMIBA CMB interferometer and their dependence on cosmology. For SZ power spectrum estimation, we find that the optimal sky coverage for a 1000 hours of integration time is several hundred square degrees. One achieves an accuracy better than 40% in the SZ measurement of power spectrum and an accuracy better than 20% in the cross correlation with Sloan galaxies for $2000<l<5000$. For cluster searches, the optimal scan rate is around 280 hours per square degree with a cluster detection rate 1 every 7 hours, allowing for a false positive rate of 20% and better than 30% accuracy in the cluster SZ distribution function measurement.Comment: 34 pages, 20 figures. Submitted to ApJ. Simulation maps have been replaced by high resolution images. For higher resolution color images, please download from http://www.cita.utoronto.ca/~zhangpj/research/SZ/ We corrected a bug in our analysis. the SZ power spectrum decreases 50% and y parameter decrease 25

Statistical Power, the Bispectrum and the Search for Non-Gaussianity in the CMB Anisotropy

We use simulated maps of the cosmic microwave background anisotropy to quantify the ability of different statistical tests to discriminate between Gaussian and non-Gaussian models. Despite the central limit theorem on large angular scales, both the genus and extrema correlation are able to discriminate between Gaussian models and a semi-analytic texture model selected as a physically motivated non-Gaussian model. When run on the COBE 4-year CMB maps, both tests prefer the Gaussian model. Although the bispectrum has comparable statistical power when computed on the full sky, once a Galactic cut is imposed on the data the bispectrum loses the ability to discriminate between models. Off-diagonal elements of the bispectrum are comparable to the diagonal elements for the non-Gaussian texture model and must be included to obtain maximum statistical power.Comment: Accepted for publication in ApJ; 20 pages, 6 figures, uses AASTeX v5.

Conservation Laws and Cosmological Perturbations in Curved Universes

When working in synchronous gauges, pseudo-tensor conservation laws are often used to set the initial conditions for cosmological scalar perturbations, when those are generated by topological defects which suddenly appear in an up to then perfectly homogeneous and isotropic universe. However those conservation laws are restricted to spatially flat (K=0) Friedmann-Lema\^\i tre spacetimes. In this paper, we first show that in fact they implement a matching condition between the pre- and post- transition eras and, in doing so, we are able to generalize them and set the initial conditions for all $K$. Finally, in the long wavelength limit, we encode them into a vector conservation law having a well-defined geometrical meaning.Comment: 15 pages, no figure, to appear in Phys. Rev.

The Sunyaev-Zeldovich effect in CMB-calibrated theories applied to the Cosmic Background Imager anisotropy power at l > 2000

We discuss the nature of the possible high-l excess in the Cosmic Microwave Background (CMB) anisotropy power spectrum observed by the Cosmic Background Imager (CBI). We probe the angular structure of the excess in the CBI deep fields and investigate whether it could be due to the scattering of CMB photons by hot electrons within clusters, the Sunyaev-Zeldovich (SZ) effect. We estimate the density fluctuation parameters for amplitude, sigma_8, and shape, Gamma, from CMB primary anisotropy data and other cosmological data. We use the results of two separate hydrodynamical codes for Lambda-CDM cosmologies, consistent with the allowed sigma_8 and Gamma values, to quantify the expected contribution from the SZ effect to the bandpowers of the CBI experiment and pass simulated SZ effect maps through our CBI analysis pipeline. The result is very sensitive to the value of sigma_8, and is roughly consistent with the observed power if sigma_8 ~ 1. We conclude that the CBI anomaly could be a result of the SZ effect for the class of Lambda-CDM concordance models if sigma_8 is in the upper range of values allowed by current CMB and Large Scale Structure (LSS) data.Comment: Accepted by The Astrophysical Journal; 17 pages including 12 color figures. v2 matches accepted version. Additional information at http://www.astro.caltech.edu/~tjp/CBI