Probing the rest-frame of the Universe with the near-IR cosmic infrared background

Abstract

ABSTRACT While the cosmic microwave background (CMB) dipole is largely assumed to be entirely kinematic, there is evidence that part of it is primordial. Such a possibility arises in models implying a tilt, interpreted as a dark flow, across the observable Universe. The kinematic nature of the entire CMB dipole can be probed using the dipole of cosmic backgrounds from galaxies after the last scattering. The near-infrared (near-IR) cosmic infrared background (CIB) spectral energy distribution leads to an amplified dipole compared with the CMB. The CIB dipole is affected by galaxy clustering, decreasing with fainter, more distant galaxies, and by Solar System emissions and Galactic dust, which dominate the net CIB cosmological dipole in the optical/near-IR. We propose a technique that enables an accurate measurement of the kinematic near-IR CIB dipole. The CIB, effectively the integrated galaxy light (IGL), would be reconstructed from resolved galaxies in forthcoming space-borne wide surveys covering four bands, 0.9–2.5 μm. The galaxies will be subselected from the identified magnitude range where the dipole component from galaxy clustering is below the expected kinematic dipole. Using this technique, the dipole can be measured in each of the bands at the statistical signal-to-noise ratio S/N ≳50–100 with the forthcoming Euclid and Roman surveys, isolating the CMB dipole’s kinematic nature.