Establish the redshift evolution of the Hα luminosity-function faint-end slope

Determine whether the faint-end slope α_Hα of the Hα luminosity function evolves with redshift from approximately z = 2 to the Epoch of Reionization at z > 6, by constraining the luminosity function substantially above and below its characteristic luminosity.

Background

The JELS data improve the faint-end coverage of the Hα luminosity function, while the FRESCO data help constrain its bright end and the characteristic luminosity L_Hα⋆. Nevertheless, degeneracy between L_Hα⋆ and α_Hα remains important, and the inferred evolution of α_Hα is compatible both with no evolution and with evolution resembling the steepening of the UV luminosity-function faint-end slope.

The authors therefore identify the redshift evolution of α_Hα as unresolved and emphasize the need for observations that extend both substantially above and below L_Hα⋆.