Abstract
ABSTRACTThe imprints of large-scale structures on the Cosmic Microwave Background (CMB) can be studied via the CMB lensing and Integrated Sachs–Wolfe (ISW) signals. In particular, the stacked ISW signal around supervoids has been claimed in several works to be anomalously high. In this study, we find cluster and void superstructures using four tomographic redshift bins with 0 < z < 0.8 from the DESI Legacy Survey and measure the stacked CMB lensing and ISW signals around them. To compare our measurements with ΛCDM model predictions, we construct a mock catalogue with matched galaxy number density and bias and apply the same photo-z uncertainty as the data. The consistency between the mock and the data is verified via the stacked galaxy density profiles around the superstructures and their quantity. The corresponding lensing convergence and ISW maps are then constructed and compared. The stacked lensing signal agrees with data well except at the highest redshift bin in density peaks, where the mock prediction is significantly higher, by approximately a factor of 1.3. The stacked ISW signal is generally consistent with the mock prediction. We do not obtain a significant signal from voids, AISW = −0.10 ± 0.69, and the signal from clusters, AISW = 1.52 ± 0.72, is at best weakly detected. However, these results are strongly inconsistent with previous claims of ISW signals at many times the level of the ΛCDM prediction. We discuss the comparison of our results with past work in this area and investigate possible explanations for this discrepancy.
Highlights
The geodesics of photons in the Cosmic Microwave Background (CMB) are perturbed by their passage through intervening largescale structures of the universe, generating effects from both spatial and temporal variations in the gravitational potential field, Φ(x, t)
We separate our analysis into two steps: (1) we finalise our selection for superstructures based on the galaxy number density maps and their cross-correlations with the CMB lensing convergence map
Due to the slightly more extended Rv distribution in the real data compared to the mock, especially in the highest redshift bin, we check whether or not including a weight, based on the ratio of the two Rv distributions, can reduce the difference between the data and mock
Summary
The geodesics of photons in the Cosmic Microwave Background (CMB) are perturbed by their passage through intervening largescale structures of the universe, generating effects from both spatial and temporal variations in the gravitational potential field, Φ(x, t). C2 0 rLSr where r is the comoving distance and rLS is the comoving distance to the last scattering surface This quantity effectively measures the total projected matter density between CMB and today weighted by a distance-dependent kernel for a given angular direction n. The temporal perturbation alters the temperature fluctuations of the CMB, leading to the Integrated Sachs-Wolfe (ISW) effect (Sachs & Wolfe 1967): ΔT (n ) =− ∫ tLS Φ(n , t) dt, (2). The. ISW effect is intriguing because Φ ≠ 0 in linear theory only in the era of late-time dark energy domination. The gravitational potential is related to the matter density fluctuation δ via the Poisson equation:
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