Dominant galaxy population driving cosmic reionisation

Determine whether the major contributors to cosmic reionisation were massive, bright galaxies or more numerous faint galaxies with ultraviolet magnitudes fainter than M_UV = -18.

Background

The paper frames the Epoch of Reionisation as a period whose timescale and physical drivers depend on the sources of hydrogen-ionising photons. Two competing possibilities are identified: massive, luminous galaxies, which produce substantial ionising output individually, and numerous faint galaxies, whose high number density could yield a larger integrated ultraviolet luminosity density.

The paper investigates ionising photon production efficiency and Lyman-continuum escape fractions in a z approximately 2 control sample, providing empirical context for studies of high-redshift galaxies. However, the relative contribution of bright and faint galaxy populations to reionisation remains unresolved in the stated passage.

References

It is yet unclear if the major contributors to reionisation were massive bright galaxies \citep{Sharma2018, Naidu2020} or more numerous faint ones (M$_{UV}>-18$) \citep{Ciardi2003,Bouwens2012, Robertson2010}.

— OutThere Survey: Addressing $\mathrm{ξ_{ion}}$ and $\mathrm{f_{esc}}$ with a population of average galaxies at z$\sim$2  (2608.19687 - Jaiswar et al., 20 Aug 2026) in Section 1, Introduction