2025ApJ...994...30F

We present new anisotropy measurements in the near-infrared for angular multipoles 300 < ℓ < 10⁵ using imaging data at 1.1 and 1.8 μm from the fourth flight of the Cosmic Infrared Background Experiment (CIBER). Using improved analysis methods and higher-quality fourth-flight data, we detect surface brightness fluctuations on scales ℓ < 2000 with CIBER auto power spectra at ∼14σ and 18σ for 1.1 and 1.8 μm, respectively, and with cross power spectra at ∼10σ. The CIBER measurements pass internal consistency tests and represent a 5-10× improvement in power spectrum sensitivity on several-arcminute scales relative to that of existing studies. Through cross correlations with tracers of diffuse galactic light (DGL), we determine that scattered DGL contributes <10% to the observed fluctuation power at high confidence. On scales ℓ < 2000 ($\theta \gt 5\,^{\prime} \,$), the CIBER auto and cross power spectra exceed predictions for integrated galactic light (IGL) and integrated stellar light (ISL) by over an order of magnitude, and are inconsistent with our baseline IGL+ISL+DGL model at high significance. We cross-correlate two of the CIBER fields with 3.6 and 4.5 μm mosaics from the Spitzer Deep Wide-field Survey and find similar evidence for departures from Poisson noise in Spitzer-internal power spectra and CIBER × Spitzer cross power spectra. A multiband analysis indicates that the wavelength dependence of low-ℓ auto power fluctuations is bluer than the Poisson noise from IGL and ISL; however, the cross correlation coefficient r_ℓ of nearly all band combinations decreases with decreasing ℓ, disfavoring astrophysical explanations that invoke a single correlated sky component.