Cosmological constraints on exotic injection of electromagnetic energy

Abstract

We compute cosmic microwave background (CMB) anisotropy constraints on exotic forms of energy injection in electromagnetic (e.m.) channels over a large range of timescales. These constraints are very powerful around or just after recombination, although CMB keeps some sensitivity e.g. to decaying species with lifetimes as long as $10^{25}$s. We review here complementary with CMB spectral distortions and primordial nucleosynthesis bounds, which dominate at earlier timescales. For the first time, we describe the effects of the e.m. energy injection on the CMB power spectra as a function of the injection epoch, using the lifetime of a decaying particle as proxy. We identify a suitable on-the-spot approximation. Our results are of interest not only for early universe relics constituting (a fraction of) the dark matter, but also for other exotic injection of e.m. radiation. For illustration, we apply our formalism to: i) Primordial black holes of mass $\in [10^{13.5},10^{16.8}]$ g, showing that the constraints are comparable to the ones obtained from gamma-ray background studies and even dominate below $\sim 10^{14}$g. ii) To a peculiar mass-mixing range in the sterile neutrino parameter space, complementary to other astrophysical and laboratory probes. iii) Finally, we provide a first estimate of the room for improvement left for forthcoming 21 cm experiments, comparing it with the reach of proposed CMB spectral distortion (PiXiE) and CMB angular power spectrum (CORE) missions. We show that the best and most realistic opportunity to look for this signal (or to improve over current constraints) in the 21 cm probe is to focus on the Cosmic Dawn epoch, $15\lesssim z\lesssim 30$, where the qualitatively unambiguous signature of a spectrum in emission can be expected for models that evade all current constraints.

33p, 10 fig. Comments welcome. V3 : updated to match published version

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Cited by in corpus (20)

• The Dawn of FIMP Dark Matter: A Review of Models and Constraints
• CMB bounds on disk-accreting massive Primordial Black Holes
• Primordial black holes from inflaton and spectator field perturbations in a matter-dominated era
• BBN constraints on the annihilation of MeV-scale dark matter
• The synergy between CMB spectral distortions and anisotropies
• Cosmological beam dump: constraints on dark scalars mixed with the Higgs boson
• CMB anisotropy and BBN constraints on pre-recombination decay of dark matter to visible particles
• Tripling down on the $W$ boson mass
• New CMB spectral distortion constraints on decaying dark matter with full evolution of electromagnetic cascades before recombination
• The DAMPE excess and gamma-ray constraints
• Cosmological Bounds on sub-GeV Dark Vector Bosons from Electromagnetic Energy Injection
• Global 21-cm brightness temperature in viscous dark energy models
• Perturbed recombination from inhomogeneous photon injection and application to accreting primordial black holes
• Wobbly Dark Matter Signals at Cherenkov Telescopes from Long Lived Mediator Decays
• CMB constraints on ultra-light primordial black holes with extended mass distributions
• LHC Lifetime Frontier and Visible Decay Searches in Composite Asymmetric Dark Matter Models
• Dark Matter Energy Deposition and Production from the Table-Top to the Cosmos
• Producing and constraining self-interacting hidden sector dark matter
• Cosmological constraints on the decay of heavy relics into neutrinos
• Sensitivities on non-spinning and spinning primordial black hole dark matter with global 21 cm troughs