The Epoch of Reionization in the R_h=ct Universe

Abstract

The measured properties of the epoch of reionization (EoR) show that reionization probably began around z ~ 12-15 and ended by z=6. In addition, a careful analysis of the fluctuations in the cosmic microwave background indicate a scattering optical depth tau ~ 0.066+/-0.012 through the EoR. In the context of LCDM, galaxies at intermediate redshifts and dwarf galaxies at higher redshifts now appear to be the principal sources of UV ionizing radiation, but only for an inferred (ionizing) escape fraction f_ion ~ 0.2, which is in tension with other observations that suggest a value as small as ~ 0.05. In this paper, we examine how reionization might have progressed in the alternative Friedmann-Robertson Walker cosmology known as the R_h=ct Universe, and determine the value of f_ion required with this different rate of expansion. We find that R_h=ct accounts quite well for the currently known properties of the EoR, as long as its fractional baryon density falls within the reasonable range 0.026 < Omega_b < 0.037. This model can also fit the EoR data with f_ion ~ 0.05, but only if the Lyman continuum photon production is highly efficient and Omega_b ~ 0.037. These results are still preliminary, however, given their reliance on a particular form of the star-formation rate density, which is still uncertain at very high redshifts. It will also be helpful to reconsider the EoR in R_h=ct when complete structure formation models become available.

24 Pages, 10 Figures. Accepted for publication in MNRAS

References in corpus (11)

• Cosmic Star Formation History
• Cosmic Reionization and Early Star-Forming Galaxies: A Joint Analysis of New Constraints from Planck and Hubble Space Telescope
• Observational constraints on Cosmic Reionization
• Radiative transfer simulations of cosmic reionization I: methodology and initial results
• Hubble Frontier Fields First Complete Cluster Data: Faint Galaxies at $z\sim 5-10$ for UV Luminosity Functions and Cosmic Reionization
• A Flat Photoionization Rate at 2<z<4.2: Evidence for a Stellar-Dominated UV Background and Against a Decline of Cosmic Star Formation Beyond z~3
• The Efficiency of Stellar Reionization: Effects of Rotation, Metallicity, and Initial Mass Function
• High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS
• High redshift AGNs and HI reionisation: limits from the unresolved X-ray background
• A Comparison of Cosmological Models Using Time Delay Lenses
• Ultra-faint high-redshift galaxies in the Frontier Fields

Cited by in corpus (15)

• The Linear Growth of Structure in the R_h=ct Universe
• Power law cosmology model comparison with CMB scale information
• $R_h=ct$ and the eternal coasting cosmological model
• Testing the Distance-Duality Relation in the $R_h=ct$ Universe
• Supermassive Black Holes in the Early Universe
• Primordial Nucleosynthesis in the Rh = ct cosmology: Pouring cold water on the Simmering Universe
• Cosmological Tests With Strong Gravitational Lenses using Gaussian Processes
• Thermodynamics of the R_h=ct Universe: A Simplification of Cosmic Entropy
• Constancy of the Cluster Gas Mass Fraction in the R_h=ct Universe
• A comparison of the R_h=ct and LCDM cosmologies based on the observed halo mass function
• Unseen Progenitors of Luminous High-z Quasars in the R_h=ct Universe
• Reassessing Dust's Role in Forming the CMB
• Tantalizing New Physics from the Cosmic Purview
• A comparison of cosmological models with high-redshift quasars
• Comparison of $\Lambda$CDM and $R_h=ct$ with updated galaxy cluster $f_{gas}$ measurements using Bayesian inference