Axion decay and anisotropy of near-IR extragalactic background light
  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.
