Relative Role of Stars and Quasars in Cosmic Reionization

TL;DR

This paper reevaluates the role of quasars in cosmic reionization, showing they may significantly contribute at high redshifts when secondary ionizations are considered, impacting future 21 cm experiments.

Contribution

It demonstrates that quasars can dominate hydrogen reionization at z>8 in certain models, challenging the traditional view that they are unimportant.

Findings

Quasars contribute substantially to reionization at z>8.

Their contribution remains below star-forming galaxies by z=6.

Models must include quasar effects for accurate 21 cm experiment design.

Abstract

We revisit the classical view that quasar contribution to the reionization of hydrogen is unimportant. When secondary ionization are taken into account, in many plausible scenarios for the formation and growth of supermassive black holes quasars contribute substantially or even dominantly at z>8, although their contribution generally falls below that of star-forming galaxies by z=6. Theoretical models that guide the design of the first generation of redshifted 21 cm experiments must, therefore, substantially account for the quasar contribution in order to be even qualitatively accurate.