The "Cold Spot" in the CMB sky could be due to the presence of an anomalous huge spherical underdense region - a "Void" - of a few hundreds Mpc/h radius. Such a structure would have an impact on the CMB two-point (power spectrum) and three-point (bispectrum) correlation functions not only at low-l, but also at high-l through Lensing, which is a unique signature of a Void. Modeling such an underdensity with an LTB metric, we show that for the power spectrum the effect should be visible already in the WMAP data only if the Void radius is at least L \gtrsim 1 Gpc/h, while it will be visible by the Planck satellite if L \gtrsim 500 Mpc/h. We also speculate that this could be linked to the high-l detection of an hemispherical power asymmetry in the sky. Moreover, there should be non-zero correlations in the non-diagonal two-point function. For the bispectrum, the effect becomes important for squeezed triangles with two very high l's: this signal can be detected by Planck if the Void radius is at least L \gtrsim 300 Mpc/h, while higher resolution experiments should be able to probe the entire parameter space. We have also estimated the contamination of the primordial non-Gaussianity f_NL due to this signal, which turns out to be negligible.
The Universe is not perfectly homogeneous, the large scale structure forms overdense regions and voids. In this paper, we consider the possibility that we occupy a special position in our Universe, close to the center of a local underdense region that we model as an LTB void embedded in a homogeneous and isotropic Universe. The CMB sky measured by an off-center observer in this void is not statistically isotropic. In addition to the non-stochastic CMB anisotropies due to the geometry of the model, we also observe a lensing-like distortion of the CMB anisotropies. In this article, we propose a …
Towards precision cosmology with Void x CMB correlations (II): Impact of mock catalogs on the Void x CMB lensing signal
Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉戈纳大学）；MTA–CSFK Lendület “Momentum” Large-Scale Structure (LSS) Research Group（匈牙利科学院-塞格德大学“动量”大尺度结构研究组）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与创新网络地球与天文学研究中心）；CPPM, Aix-Marseille Université, CNRS/IN2P3（地中海粒子与核物理中心，艾克斯-马赛大学，法国国家科学研究中心/法国国家核与粒子物理研究所）；Princeton University（普林斯顿大学）；California Institute of Technology（加州理工学院）
研究通过分析模拟目录对Void x CMB引力透镜信号的影响，探讨了未来宇宙学约束的潜力，发现该信号对模拟目录的依赖性较低，预计罗马任务结合现有和未来CMB观测将显著提高信号噪声比。
我们利用VIMOS光谱仪对宇宙微波背景冷点进行了红移测量。冷斑的一个可能原因是在中等或低红移处由一个非常大的空隙（线性尺寸为数百Mpc）所压印的综合萨克斯-沃尔夫效应。如果<1 emission-line galaxies drawn from an I-band flux limited sample of galaxies in the direction of the cold spot shows no evidence of a gap on scales of Delta-z>在0.35<z<1处存在这样一个空洞，那么红移分布超过700 z 0.05。在较小尺度（Δ z ~0.01）上的红移分布中存在波谷，表明较小尺度的空洞可以连接朝向冷点分离几度的区域。将这种分布与从VVDS调查的宽间隔点中提取的类似大小的子样本所产生的分布进行比较，并不表明朝向冷点的红移分布是异常的，或者这些小间隙可以唯一地归因于真实的空洞。
Several authors have previously shown that Gpc-scale void based on the spherically symmetric LTB model can provide a good fit to certain cosmological data, including the SNIa data, but it is only consistent with the observed CMB dipole if we are located very close to the center, in violation of the Copernican principle. In this work we investigate the more general quasispherical Szekeres model, which does not include spherical symmetry, in order to determine whether this option may be less constricting. We find that the observer is still constrained to a small region, but it is not as geometri…
We report a $5.3σ$ detection of the gravitational lensing effect of cosmic voids from the Baryon Oscillation Spectroscopic (BOSS) Data Release 12 seen in the $Planck$ 2018 cosmic microwave background (CMB) lensing convergence map. To make this detection, we introduce new optimal techniques for void stacking and filtering of the CMB maps, such as binning voids by a combination of their observed galaxy density and size to separate those with distinctive lensing signatures. We calibrate theoretical expectations for the void-lensing signal using mock catalogs generated in a suite of 108 full-sky l…
Towards precision cosmology with Voids x CMB correlations (I): Roman-Agora mock catalogs and pipeline validation
Instituto de Astrofísica de Canarias（加那利天体物理学研究所）；Universidad de La Laguna（拉古纳大学）；MTA–CSFK Lendület “Momentum” Large-Scale Structure (LSS) Research Group（马塔-匈牙利科学院技术研究中心“动量”大尺度结构研究组）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与创新地球与天文学研究中心）；CPPM, Aix-Marseille Université, CNRS/IN2P3（马赛物理中心，艾克斯-马赛大学，法国国家科学研究中心/法国国家核与粒子物理研究所）；Princeton University（普林斯顿大学）
Statistical Isotropy of the Cosmic Microwave Background (CMB) radiation has been studied and debated extensively in recent years. Under this assumption, the hot spots and cold spots of the CMB are expected to be uniformly distributed over a 2-sphere. We use the orientation matrix, first proposed by Watson (1965) and Scheidegger (1965) and associated shape and strength parameters (Woodcock, 1977) to analyse whether the hot and cold spots of the observed CMB temperature anisotropy field are uniformly placed. We demonstrate the usefulness of our estimators by using simulated toy models containing…
The CMB lensing signal from cosmic voids and superclusters probes the growth of structure in the low-redshift cosmic web. In this analysis, we cross-correlated the Planck CMB lensing map with voids detected in the Dark Energy Survey Year 3 (Y3) data set ($\sim$5,000 deg$^{2}$), expanding on previous measurements that used Y1 catalogues ($\sim$1,300 deg$^{2}$). Given the increased statistical power compared to Y1 data, we report a $6.6σ$ detection of negative CMB convergence ($κ$) imprints using approximately 3,600 voids detected from a redMaGiC luminous red galaxy sample. However, the measured…
We develop an estimator to extract the mean radial velocity profile of cosmic voids via the kinematic Sunyaev-Zeldovich effect of pairs of galaxies surrounding them. The estimator is tested with simulated pure kSZ map and void catalogue data from the same simulation. The results show that the recovered signal could be attenuated by low angular resolution of the map or large aperture photometry filter radius size, but the mean radial velocity profile can be fully recovered with our estimator. By applying the estimator to the Planck 2D-ILC CMB map, with galaxy and void catalogues from BOSS DR12,…
Evidence for a sign change of the ISW effect in the very recent universe? hot voids and cold overdensities at $z<0.03$
Institute of Theoretical Astrophysics, University of Oslo（奥斯陆大学理论天体物理研究所）；Instituto de Astronomía Teórica y Experimental, CONICET-UNC（CONICET-科尔多瓦大学理论与实验天文学研究所）；Observatorio Astronómico de Córdoba, UNC（科尔多瓦天文台，科尔多瓦大学）
Galaxy angular-power spectrum and autocorrelation functions (ACFs) provide information about the distribution of matter by using galaxy counts as a proxy. In this study, we are going to estimate autocorrelation angular power spectrum and angular autocorrelation function for EMU-ASKAP 5 sigma sources and then compare them with results from NVSS. We will also use SUMSS data to compare ACF results using Landy-Szalay estimator. EMU-ASKAP will provide excellent opportunity to observe universe with high sensitivity and is likely going to observe millions of high redshift sources which will help in s…
We apply our tetrad-based approach for constructing spherically-symmetric solutions in general relativity to modelling a void, and compare it with the standard Lemaître-Tolman-Bondi (LTB) formalism. In particular, we construct models for the void observed in the direction of Draco in the WISE-2MASS galaxy survey, and a corresponding cosmic microwave background (CMB) temperature decrement in the Planck data in the same direction. We find that the present-day density and velocity profiles of the void are not well constrained by the existing data, so that void models produced from the two approac…
We derive an observational constraint on a spherical inhomogeneity of the void centered at our position from the angular power spectrum of the cosmic microwave background(CMB) and local measurements of the Hubble parameter. The late time behaviour of the void is assumed to be well described by the so-called $Λ$-Lemaître-Tolman-Bondi~($Λ$LTB) solution. Then, we restrict the models to the asymptotically homogeneous models each of which is approximated by a flat Friedmann-Lemaître-Robertson-Walker model. The late time $Λ$LTB models are parametrized by four parameters including the value of the co…
Measurement of the acoustic peaks of the cosmic microwave background (CMB) temperature anisotropies has been instrumental in deciding the geometry and content of the universe. Acoustic peak positions vary in different parts of the sky due to statistical fluctuation. We present the statistics of the peak positions of small patches from ESA Planck data. We found that the peak positions have significantly high variance compared to the 100 CMB simulations with best-fit LambdaCDM model with lensing and Doppler boosting effects included. Examining individual patches, we found the one containing the …
Heavy particles with masses much bigger than the inflationary Hubble scale $H_*$, can get non-adiabatically pair produced during inflation through their couplings to the inflaton. If such couplings give rise to time-dependent masses for the heavy particles, then following their production, the heavy particles modify the curvature perturbation around their locations in a time-dependent and scale non-invariant manner. This results into a non-trivial spatial profile of the curvature perturbation that is preserved on superhorizon scales and eventually generates localized hot or cold spots on the C…
The CMB Cold Spot as predicted by foregrounds around nearby galaxies
Instituto de Astronomía Teórica y Experimental (IATE), CONICET-UNC（理论与实验天体物理研究所 (IATE)，CONICET-UNC）；Observatorio Astronómico de Córdoba (OAC), UNC（科尔多瓦天文台 (OAC)，科尔多瓦大学）；Comisión Nacional de Actividades Espaciales (CONAE)（国家航天活动委员会 (CONAE)）；Institute of Theoretical Astrophysics, University of Oslo（奥斯陆大学理论天体物理研究所）
Cosmic voids gravitationally lens the cosmic microwave background (CMB) radiation, resulting in a distinct imprint on degree scales. We use the simulated CMB lensing convergence map from the MICE N-body simulation to calibrate our detection strategy for a given void definition and galaxy tracer density. We then identify cosmic voids in DES Year 1 data and stack the Planck 2015 lensing convergence map on their locations, probing the consistency of simulated and observed void lensing signals. When fixing the shape of the stacked convergence profile to that calibrated from simulations, we find im…
The standard cosmological paradigm narrates a reassuring story of a universe currently dominated by an enigmatic dark energy component. Disquietingly, its universal explaining power has recently been challenged by, above all, the $\sim4σ$ tension in the values of the Hubble constant. Another, less studied anomaly is the repeated observation of integrated Sachs-Wolfe imprints $\sim5\times$ stronger than expected in the $Λ$CDM model from R>100 $Mpc/h$ super-structures. Here we show that the inhomogeneous AvERA model of emerging curvature is capable of telling a plausible albeit radically differe…
