Thermalization of large energy release in the early Universe

Abstract

Spectral distortions of the cosmic microwave background (CMB) provide a unique tool for learning about the early phases of cosmic history, reaching deep into the primordial Universe. At redshifts $z<10^6$, thermalization processes become inefficient and existing limits from COBE/FIRAS imply that no more than $\Delta \rho /\rho <6\times 10^{-5}$ (95% c.l.) of energy could have been injected into the CMB. However, at higher redshifts, when thermalization is efficient, the constraint weakens and $\Delta \rho /\rho \simeq 0.01-0.1$ could in principle have occurred. Existing computations for the evolution of distortions commonly assume $\Delta \rho /\rho \ll 1$ and thus become inaccurate in this case. Similarly, relativistic temperature corrections become relevant for large energy release, but have previously not been modeled as carefully. Here we study the evolution of distortions and the thermalization process after single large energy release at $z>10^5$. We show that for large distortions the thermalization efficiency is significantly reduced and that the distortion visibility is sizeable to much earlier times. This tightens spectral distortions constraints on low-mass primordial black holes with masses $M_{\mathrm{PBH}}<6\times 10^{11}$ g. Similarly, distortion limits on the amplitude of the small-scale curvature power spectrum at wavenumbers $k>10^4{\mathrm{Mpc}}^{-1}$ and short-lived decaying particles with lifetimes $t_X<10^7$ s are tightened, however, these still require a more detailed time-dependent treatment. We also briefly discuss the constraints from measurements of the effective number of relativistic degrees of freedom and light element abundances and how these complement spectral distortion limits.

22 pages, 19 figures, accepted MNRAS version

References in corpus (13)

• Primordial Black Holes as Dark Matter
• Primordial Nucleosynthesis in the Precision Cosmology Era
• Relic neutrino decoupling with flavour oscillations revisited
• Big Bang Nucleosynthesis as a Probe of New Physics
• Testing scenarios of primordial black holes being the seeds of supermassive black holes by ultracompact minihalos and CMB $\mu$-distortions
• Silk damping at a redshift of a billion: a new limit on small-scale adiabatic perturbations
• Constraining The Early-Universe Baryon Density And Expansion Rate
• The synergy between CMB spectral distortions and anisotropies
• Non-universal BBN bounds on electromagnetically decaying particles
• Creation of the CMB spectrum: precise analytic solutions for the blackbody photosphere
• Improved calculations of electron-ion Bremsstrahlung Gaunt factors for astrophysical applications
• The double Compton emissivity in a mildly relativistic thermal plasma within the soft photon limit
• Evolution of low-frequency features in the CMB spectrum due to stimulated Compton scattering and Doppler-broadening

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