Euclid preparation. CXII. Baryon acoustic oscillations extraction techniques: comparison and optimisation
Abstract
We present the first end-to-end validation of the Euclid baryon acoustic oscillation (BAO) analysis pipeline, encompassing density-field reconstruction, two-point correlation function measurement, and cosmological parameter inference. Using eight Euclid-like mock catalogues extracted from each of the four snapshots of the and , in four redshift snapshots (0.9 łeq z łeq 1.8). The pipeline introduces several methodological advances: an emulator-based model evaluator ( ) combined with a Hamiltonian Monte Carlo sampler ( ), achieving a speed-up of more than 500 times relative to standard Monte Carlo Markov chains, and a semi-analytical covariance estimator ( ) that enables robust error estimates with only eight mock realisations and remains stable under variations in the fiducial cosmology. Together, these components ensure computational efficiency while significantly reducing the risk of underestimating the parameter uncertainties. simulation, which is designed to replicate the statistical properties of the first Euclid data release (DR1), we assessed the performance of the two standard BAO reconstruction methods based on the Zeldovich approximation, RecSym RecIso Bora.jl NUTS BeXiCov+WinCov Ω_ m , H_0r_ s $ by a factor of sim3, which is equivalent to tripling the effective survey volume. When we combined the four redshift bins, the improvement remained substantial, with BAO-only constraints reaching sim10% precision on Ω_ m and sim3% on H_0 r_ s . The results from and are consistent within the uncertainties, but we recommend during testing because its sensitivity to covariance variations is lower. These findings establish the accuracy, robustness, and scalability of the Euclid BAO pipeline for DR1 and provide a solid foundation for future cosmological analyses. RecSym RecIso RecSym