Abstract
An explanation has been proposed for the observed excess of cosmic light at infrared wavelengths. It invokes stars that are cast into the dark-matter haloes of their parent galaxies during powerful galaxy collisions. See Letter p.514 During the past two decades, space telescopes have detected variations in the near-infrared background radiation that cannot be explained by emissions from known galaxies. Suggested sources for this excess radiation have included contributions from the earliest galaxies during the epoch of reionization, and faint, dwarf galaxies at intermediate redshifts. These sources would leave characteristic imprints on the spatial variation of the near-infrared background, but previous measurements have not sampled at sufficiently large spatial scales to distinguish these signatures. Asantha Cooray et al. now report measurements from the Spitzer telescope that sample at angular scales of as much as one degree, and find that the previously suggested sources do not explain the data. Rather, they suggest that the fluctuations arise from intrahalo stars that were stripped from their host galaxies during galactic collisions and have migrated to distant orbits in the galaxies' dark-matter haloes.
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