Euclid: Validation of the MontePython forecasting tools
Abstract
Context. The Euclid mission of the European Space Agency will perform a survey of weak lensing cosmic shear and galaxy clustering in order to constrain cosmological models and fundamental physics.
Aims: We expand and adjust the mock Euclid likelihoods of the MontePython software in order to match the exact recipes used in previous Euclid Fisher matrix forecasts for several probes: weak lensing cosmic shear, photometric galaxy clustering, the crosscorrelation between the latter observables, and spectroscopic galaxy clustering. We also establish which precision settings are required when running the EinsteinBoltzmann solvers CLASS and CAMB in the context of Euclid.
Methods: For the minimal cosmological model, extended to include dynamical dark energy, we perform Fisher matrix forecasts based directly on a numerical evaluation of second derivatives of the likelihood with respect to model parameters. We compare our results with those of previously validated Fisher codes using an independent method based on first derivatives of the Euclid observables.
Results: We show that such MontePython forecasts agree very well with previous Fisher forecasts published by the Euclid Collab oration, and also, with new forecasts produced by the CosmicFish code, now interfaced directly with the two EinsteinBoltzmann solvers CAMB and CLASS. Moreover, to establish the validity of the Gaussian approximation, we show that the Fisher matrix marginal error contours coincide with the credible regions obtained when running Monte Carlo Markov chains with MontePython while using the exact same mock likelihoods.
Conclusions: The new Euclid forecast pipelines presented here are ready for use with additional cosmological parameters, in order to explore extended cosmological models.
This paper is published on behalf of the Euclid Consortium.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 February 2024
 DOI:
 10.1051/00046361/202346772
 arXiv:
 arXiv:2303.09451
 Bibcode:
 2024A&A...682A..90C
 Keywords:

 cosmology: theory;
 surveys;
 cosmology: observations;
 largescale structure of Universe;
 cosmological parameters;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 45 pages, 24 figures