New Population Synthesis Models of the Cosmic UV Background

2011/03/27 by Francesco Haardt, Piero Madau, Haardt, Francesco +1
Earth and Planetary Sciences · #Atmospheric Ozone and Climate #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences

paper · pdf · doi:10.48550/arxiv.1103.5226

openalex publication_date 2011/03/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We present improved synthesis models of the evolving spectrum of the UV/X-ray diffuse background, updating and extending our previous results. A "minimal cosmic reionization model" is presented in which the galaxy UV emissivity traces recent determinations of the cosmic history of star formation, the luminosity-weighted escape fraction of hydrogen-ionizing radiation increases rapidly with redshift, from 1% at z=3 to 50% at z=8.5, the clumping factor of the intergalactic medium is C=3, and Population III stars make a negligible contribution to the metagalactic flux. The model provides a good fit to the hydrogen-ionization rates inferred from flux decrement measurements, and yields an optical depth to Thomson scattering, tau_e=0.085, that is in agreement with WMAP results.

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