English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The ionizing background of cosmic hydrogen is an important probe of thesources and absorbers of ionizing radiation in the post-reionization universe.Previous studies show that the ionization rate should be very sensitive tochanges in the source population: as the emissivity rises, absorbers shrink insize, increasing the ionizing mean free path and, hence, the ionizingbackground. By contrast, observations of the ionizing background find a veryflat evolution from z~2-5, before falling precipitously at z~6. We resolve thispuzzling discrepancy by pointing out that, at z~2-5, optically thick absorbersare associated with the same collapsed halos that host ionizing sources. Thus,an increasing abundance of galaxies is compensated for by a correspondingincrease in the absorber population, which moderates the instability in theionizing background. However, by z~5-6, gas outside of halos dominates theabsorption, the coupling between sources and absorbers is lost, and theionizing background evolves rapidly. Our halo based model reproducesobservations of the ionizing background, its flatness and sudden decline, aswell as the redshift evolution of the ionizing mean free path. Our worksuggests that, through much of their history, both star formation andphotoelectric opacity in the universe track halo growth.

The Flatness and Sudden Evolution of the Intergalactic Ionizing Background