Reionization - A probe for the stellar population and the physics of the early universe

TL;DR

This paper investigates how different models of stellar populations, primordial magnetic fields, and dark matter properties influence the reionization history of the universe, providing new constraints on these early universe components.

Contribution

It offers novel limits on primordial magnetic fields and dark matter characteristics based on reionization modeling, extending understanding of early universe physics.

Findings

Stellar populations with a Scalo IMF cannot solely reionize the universe without high efficiencies.

Primordial magnetic fields are constrained to be below 0.7-5 nG based on their impact on reionization.

Upper limits on dark matter annihilation cross section and lower limits on dark matter lifetime are established.

Abstract

We calculate the reionization history for different models of the stellar population and explore the effects of primordial magnetic fields, dark matter decay and dark matter annihilation on reionization. We find that stellar populations based on a Scalo-type initial mass function for Population II stars can be ruled out as sole sources for reionization, unless star formation efficiencies of more than 10% or very high photon escape fractions from the parental halo are adopted. When considering primordial magnetic fields, we find that the additional heat injection from ambipolar diffusion and decaying MHD turbulence has significant impact on the thermal evolution and the ionization history of the post-recombination universe and on structure formation. The magnetic Jeans mass changes the typical mass scale of the star forming halos, and depending on the adopted stellar model we derive upper limits to the magnetic field strength between 0.7 and $5 $nG (comoving). For dark matter annihilation, we find an upper limit to the thermally averaged mass-weighted cross section of $10^{-33} \mathrm{cm}^3\mathrm{/s/eV}$. For dark matter decay, our calculations yield a lower limit to the lifetime of dark matter particles of $3\times10^{23}$ s. These limits are in agreement with constraints from recombination and the X-ray background and provide an independent confirmation at a much later epoch.