Work

Accurate cosmological emulator for the probability distribution function of gravitational lensing of point sources

Year: 2026

Type: article

Abstract: Aims. We developed an accurate and computationally efficient emulator to model the gravitational lensing magnification probability distribution function (PDF), enabling robust cosmological inference of point sources such as supernovae and gravitational-wave observations. Methods. We constructed a pipeline utilizing cosmological N -body simulations, creating past light cones to compute convergence and shear maps. Principal component analysis (PCA) was employed for dimensionality reduction, followed by an extreme gradient boosting (XGBoost) machine learning model to interpolate magnification PDFs across a broad cosmological parameter space (Ω m , σ 8 , w , h ) and redshift range (0.2 ≤ z ≤ 6). We identified the optimal number of PCA components to balance accuracy and stability. Results. Our emulator, publicly released as ace_lensing , accurately reproduces lensing PDFs with a median Kullback–Leibler divergence of 0.007. Validation on the test set confirms that the model reliably reproduces the detailed shapes and statistical properties of the PDFs across the explored parameter range, showing no significant degradation for specific parameter combinations or redshifts. Future work focuses on incorporating baryonic physics through hydrodynamical simulations and expanding the training set to further enhance model accuracy and generalizability.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202558463

Authors: Tunç Turker, Valerio Marra, Tiago Castro, Miguel Quartin, Stefano Borgani