Perturbed Recombination from Dark Matter Annihilation

Abstract

We show that dark matter annihilation around the time of recombination can lead to growing ionization fraction perturbations, that track the linear collapse of matter over-densities. This amplifies small scale cosmological perturbations to the free electron density by a significant amount compared to the usual acoustic oscillations. Electron density perturbations distort the CMB, inducing secondary non-gaussianity. We calculate the CMB bispectrum from recombination, that is marginally observable by Planck. Even though electron perturbations can be markedly boosted compared with the Standard Model prediction, the dark matter effect in the CMB bispectrum turns out to be small and will be difficult to disentangle from the standard model in the foreseeable future.

20 pages, 8 figures. v2: added references, improved discussion of second order source, corrected treatment of molecular weight in matter temperature evolution; results unchanged

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Cited by in corpus (13)

• Potential of radio telescopes as high-frequency gravitational wave detectors
• Constraints on dark matter annihilation from CMB observations before Planck
• Constraining dark matter late-time energy injection: decays and p-wave annihilations
• A new light on 21 cm intensity fluctuations from the dark ages
• Snowmass2021 Cosmic Frontier White Paper:Primordial Black Hole Dark Matter
• An Ultimate Target for Dark Matter Searches
• Aspects of Dark Matter Annihilation in Cosmology
• Perturbed recombination from inhomogeneous photon injection and application to accreting primordial black holes
• The Effects of Dark Matter Annihilation on Cosmic Reionization
• The impact of non-Planckian effects on cosmological radio backgrounds
• Stability of small-scale baryon perturbations during cosmological recombination
• CMB temperature trispectrum from accreting primordial black holes
• Does the Reionization Model Influence the Constraints on Dark Matter Decay or Annihilation?