We present a novel framework for jointly modelling the weak lensing source galaxy redshift distribution and the intrinsic alignment of galaxies via a shared luminosity function.
Considering this framework within the context of an LSST Year 1 and Year 10 cosmic shear analysis, we first demonstrate the substantial impact of the luminosity function on both source galaxy redshift distributions and the intrinsic alignment contamination.
We elucidate how the individual parameters of a Schechter luminosity function model impact the redshift distribution of a magnitude-limited sample, and we demonstrate the effect of marginalising over the luminosity function as incorporated in a state-of-the-art cosmic shear analysis.
Finally, we forecast the capability of the framework to provide cosmological parameter constraints.
We find that this joint modelling framework can produce cosmological constraints comparable to those expected in typical analyses, while avoiding the potential biases due to incorrectly fixing lumionsity function parameters.
We also discuss the potential of this method in providing a natural way to model generic selection functions in redshift distribution estimation, as well as its possibilities for extension to a 3x2pt analysis, particularly with respect to incorporating galaxy bias in this luminosity-function-based framework.