Axion decay and anisotropy of near-IR extragalactic background light

TL;DR

This paper investigates how decaying axions could contribute to the near-infrared extragalactic background light, using observational data to constrain axion properties and suggesting a potential dark matter signature.

Contribution

It introduces a novel analysis linking axion decay to IR background anisotropy, providing constraints on axion mass and abundance from recent observations.

Findings

Axions with ~4 eV mass can explain IR background power spectra.

Estimated axion abundance is comparable to baryon density.

Data favors a mass distribution model over standard QCD predictions.

Abstract

The extragalactic background light (EBL) is comprised of the cumulative radiation from all galaxies and active galactic nuclei over the cosmic history. In addition to point sources, EBL also contains information from diffuse sources of radiation. The angular power spectra of the near-infrared intensities could contain additional signals and a complete understanding of the nature of the IR background is still lacking in the literature. Here we explore the constraints that can be placed on particle decays, especially candidate dark matter models involving axions that trace dark matter halos of galaxies. Axions with a mass around a few eV will decay via two photons with wavelengths in the near-IR band, and will leave a signature in the IR background intensity power spectrum. Using recent power spectra measurements from the Hubble Space Telescope (HST) and Cosmic Infrared Background Experiment (CIBER), we find that the 0.6 to 1.6 micron power spectra can be explained by axions with masses around 4 eV. The total axion abundance Omega_a~0.05, and it is comparable to the baryon density of the Universe. The suggested mean axion mass and abundance are not ruled out by existing cosmological observations. Interestingly, the axion model with a mass distribution is preferred by the data, which cannot be explained by the standard quantum chromodynamics (QCD) theory and needs further discussion.