Searching for axion-like particle decay in the near-infrared background: an updated analysis

TL;DR

This paper investigates whether decay of axion-like particles could explain the unexplained excess in the near-infrared background anisotropies, but finds tensions with existing astrophysical constraints.

Contribution

It provides an updated analysis of the near-IR background power spectrum including ALP decay contributions and compares it with observational data.

Findings

ALP decay models can partially account for the IR excess

Preferred ALP parameters are in tension with star cooling constraints

The analysis refines the limits on ALP properties from IR background data

Abstract

The extragalactic background light is comprised of the cumulative radiation from all galaxies across the history of the universe. The angular power spectrum of the anisotropies of such a background at near-infrared (IR) frequencies lacks of a complete understanding and shows a robust excess which cannot be easily explained with known sources. Dark matter in the form of axion-like particles (ALPs) with a mass around the electronvolt will decay into two photons with wavelengths in the near-IR band, possibly contributing to the background intensity. We compute the near-IR background angular power spectrum including emissions from galaxies, as well as the contributions from the intra-halo light and ALP decay, and compare it to measurements from the Hubble Space Telescope and Spitzer. We find that the preferred values for the ALP mass and ALP-photon coupling to explain the excess are in tension with star cooling data and observations of dwarf spheroidal galaxies.