Abstract
Titolo: Optimizing the extraction of cosmological information from Large Scale Structure analysis in view of the next large spectroscopic surveys. Abstract:This proposal aims to develop innovative methods to fully leverage spectroscopic galaxy redshift surveys, with a strong focus on addressing systematic errors that could significantly bias cosmological measurements. For the first time at the BAO scale, we will explore the combined constraining power of lower- and higher-order correlation functions, which contain complementary information on BAO features and structure formation not fully captured by current analyses. To this end, we propose an end-to-end clustering analysis that includes modeling key observational systematics specific to targeted galaxy surveys, developing mitigation strategies, performing a joint measurement of the two-point and three-point correlation functions up to ~120 Mpc/h, and estimating cosmological parameters.
Results achieved
: "The main goal of this project are the following: - develop an end-to-end pipeline to encode realistic observational effects into simulated data, to be able to quickly forecast the performance of future instruments like the ESA mission Euclid; - quantify the impact of wrong redshift measurements (e.g. for the Euclid mission) on clustering measurements, developing mitigation strategies to compensate for potential biases; - build a comprehensive framework for the analysis of the 3PCF to be applied on real and simulated data: for this purpose, it will be needed to: - develop accurate models for the isotropic and anisotropic 3PCF - generate a ML-based emulator in order to generate the previous models efficiently and robustly; - include these models in a full MCMC analysis to provided constraints on galaxy biases and cosmological parameters. - perform measurements of the 3PCF on real (e.g. SDSS BOSS) and simulated (e.g. Euclid-like) data, including the estimate of the associated covariance matrix; - obtain the first cosmological constraints from the combination of 2PCF+3PCF, both on real and simulated data, and compare the results with standard approaches available in the literature. If successful, this project will deliver the first cosmological constraints from the full-shape analysis of the 3PCF up to the BAO scale, and deliver innovative models that will be used for current and future surveys to expand current analysis to higher-order correlation functions and maximise the scientific exploitation of future spectroscopic surveys." ACHIEVED RESULTS This project aimed to maximize the extraction of cosmological information from large-scale structure (LSS) galaxy clustering by developing a new and comprehensive framework based on the full-shape analysis of two-point and three-point correlation functions (2PCF and 3PCF). The project is structured around two main pillars. The first component (Work Package 1) focused on developing a framework to quantify the impact of spectroscopic survey systematics on cosmological measurements and to design strategies for their mitigation. The second component (Work Package 2), based on the results of WP1, aimed to develop a statistical framework for a Bayesian analysis of both lower- and higher-order correlation functions. This enabled, for the first time, the derivation of cosmological constraints from the joint analysis of the two-point and three-point correlation functions. Achieving this required the development of emulators to speed up the evaluation of 3PCF models, a Bayesian framework to combine models and observations consistently, and the application of the methodology to both simulated and real datasets. Finally, we established a new Work Package 3, dedicated to exploring alternative approaches to constraining cosmology. These approaches yield complementary information that can be integrated into the primary framework in the future to further improve the precision of cosmological parameter estimates. By jointly exploiting lower- and higher-order statistics, the project accesses information on the expansion history of the Universe and the growth of cosmic structures that is not fully captured by standard two-point analyses. The framework has been tested and validated on state-of-the-art simulated datasets and applied to existing spectroscopic survey data for which a combined 2PCF and 3PCF cosmological analysis has not yet been fully explored. The achievements of this project are contained in 23 papers (identifiable by the code ”2022NY2ZRS” in the Acknowledgments section), either accepted or submitted to peer-reviewed journals, plus an additional 6 papers in preparation. The main achievements of the project, divided into the various parts, are the following: 1. Forward-modeling of observational systematics [WP1]. A forward-modeling code was developed to imprint survey geometry and observational systematic effects into mock galaxy catalogs, providing fast and robust forecasts for spectroscopic surveys. The framework was applied to the spectroscopic survey of the ESA Euclid mission, generating full-sky mock catalogues with realistic imprinting of survey configurations (such as exposure time and noise sources), significantly contributing to the preparation of its clustering analyses. 2. Spectroscopic redshift pipeline and performance characterization [WP1]. The project contributed to the development of the Euclid spectroscopic reduction pipeline and to the characterization of redshift measurement accuracy, precision, and potential sources of error. Validation tests and pixel-level simulations were performed to quantify the impact of redshift uncertainties on cosmological analyses. These tests confirmed the pipeline delivers highly accurate redshift measurements with a level of precision matching the expected requirements. 3. Impact and mitigation of redshift interlopers [WP1]. The impact of catastrophic redshift errors and interlopers on two-point and three-point correlation function measurements was assessed for Euclid-like surveys. Mitigation strategies were developed and validated, allowing to recover most of the cosmological information; in particular, the impact of interlopers on the growth rate of structure is successfully mitigated to a 1%–3% systematic error, smaller than the expected statistical error for the Euclid DR1 analysis. 4. Modelization and emulation of higher-order clustering [WP2]. Algorithms for measuring the galaxy three-point correlation function were designed, implemented, and validated within the Euclid Science Ground Segment. Both exact and accelerated estimators were developed to enable higher-order clustering measurements on survey-scale datasets. Theoretical modelling of the anisotropic halo three-point correlation function was also advanced, and new emulators were developed to allow fast cosmological inference from three-point statistics. This allowed to speed up the computation of 3PCF models from several hours to just a few seconds, opening for the first time the possibility of such analyses. Methods for denoising clustering covariance matrices were also introduced. 5. Joint two-point and three-point cosmological analyses [WP2]. The developed framework allowed us to perform the first ever full-shape joint analyses of the two-point and three-point correlation functions, delivering forecasts on the expected performance with Euclid (based on Euclid Flagship simulations) and providing measurements on real data from the SDSS BOSS survey. We find that the joint 2PCF+3PCF analysis breaks the degeneracy between parameters yielding significant improvements over the the analysis of lower-order clustering functions alone, with gains in accuracy between 10% and 30%, depending on the considered cosmological parameter. 6. Higher-order statistics for beyond-standard cosmology [WP2]. The imprint of massive neutrinos on the three-point correlation function was investigated for the first time. The results show that configuration-dependent 3PCF measurements can break the degeneracy between neutrino mass and σ8, enabling competitive constraints on neutrino masses. 7. Complementary cosmological probes beyond the standard approaches [WP3]. Independent and synergistic approaches were developed beyond galaxy clustering, including cosmic chronometers based on age-dating of stellar populations and clusters, and gravitational-wave standard sirens. These methods provide independent measurements of the expansion history of the Universe and strengthen the connection between large-scale structure analyses and future multi-messenger cosmology. With this PRIN2022 project, we successfully established an innovative framework to characterise, imprint, and mitigate observational systematic effects in current and next-generation galaxy spectroscopic surveys. These activities have represented an important step and a scientific legacy for the Euclid mission, as they have directly contributed to the mission’s Science Ground Segment, being integrated to inform the selection function and the construction of random catalogues. The various tools implemented and validated in simulations are enabling the realistic imprinting of survey geometry and observational biases onto mock catalogues, while also proposing strategies to minimise their impact and optimise the mission’s scientific return. The work done on the analysis of the joint 2PCF+3PCF represents a significant step forward with respect to standard Fourier-space analyses, since it demonstrates the feasibility of such analyses in configuration space, where it is much easier to account for the survey geometry and selection function. This work supports the inclusion of higher-order correlation functions in configuration space as a standard technique to enhance cosmological constraints in future surveys.Project details
Unibo Team Leader: Michele Ennio Maria Moresco
Unibo involved Department/s:
Dipartimento di Fisica e Astronomia "Augusto Righi"
Coordinator:
ALMA MATER STUDIORUM - Università di Bologna(Italy)
Total Eu Contribution: Euro (EUR) 224.301,00
Total Unibo Contribution: Euro (EUR) 112.203,00
Project Duration in months: 24
Start Date:
28/09/2023
End Date:
28/02/2026
