Halo light cones with optimised orientations and interpolations in cosmological simulations

A critical step in creating realistic mock catalogs that support large-scale photometric and spectroscopic sky surveys is the production of cosmological simulations that accurately model the survey observables, while taking into account the redshift-dependent galaxy formation and evolution processes. In this work, we developed an efficient framework named Halo Optimised Lightcone Constructor ( HOLCon ) for the post facto construction of dark matter halo light cones from simulations. We used these light cones to generate a mock galaxy catalogue. The framework includes a module to optimise the light cone’s orientation within the simulation box, minimising repeated structures when the survey volume exceeds a single box, which is a common challenge in modern surveys. A linear interpolation scheme tracks the evolution of halo properties across snapshots. Applied to the publicly available Uchuu simulation, we constructed a light cone of 50 deg 2 and extending up to z = 10, providing representative coverage of deep fields of Stage IV surveys. We validated the light cone for cosmological applications by comparing the dark matter halo clustering in the light cone with those from the original simulation snapshots. Subsequently, we made the galaxy-halo connection on the light cone with a redshift-extended version of the SciPIC algorithm, producing a comprehensive set of descriptive galaxy attributes. HOLCon leverages Dask , a scalable parallel computing Pythonic framework for the fast construction of dark matter halo light cones, enabling the rapid creation of multiple statistical realisations essential for robust cosmological inference. The generated galaxy mock allows us to make predictions for the clustering of H α emitters, making it a useful resource in cosmology studies.