2026/07/22 by Dongkok Kim, Donghui Jeong, Yi-Kuan Chiang +1
#astro-ph.CO
The physical origin of cosmic acceleration remains one of the central questions in modern cosmology. The integrated Sachs-Wolfe (ISW) and Rees-Sciama (RS) effects, which arise from the evolution of gravitational potentials, provide a dynamical test of cosmic acceleration. We measure the cross correlation between the Planck temperature map of the cosmic microwave background (CMB) and a foreground-free map of the 100 μm cosmic infrared background (CIB) from Y.-K. Chiang (2023), using the k-nearest neighbor cumulative distribution function (kNN-CDF). As the CIB map is reconstructed from ∼600 million Wide-field Infrared Survey Explorer galaxies extending to z≈2.5, the measurement is equivalent to a galaxy-CMB cross correlation. We find evidence for a positive cross correlation, rejecting the null hypothesis of no correlation at p=0.02~(2.3σ) using the χ2 test. We further quantify its amplitude with AkNN, defined relative to an assumed cosmological model, and obtain AkNN=0.95±0.20~(4.8σ) with respect to ΛCDM mock data including the ISW and RS effects. The kNN-CDF analysis improves the detection significance by ∼20% over the two-point correlation function. We also explore evolving dark energy by constructing two tomographic maps from the full CIB map; the results are consistent with ΛCDM. Finer tomographic reconstruction of the CIB, for example from multiband data of SPHEREx, would further tighten constraints on evolving dark energy.