Galaxies don't sit still — gravity pulls them toward one another, and how fast a pair closes that gap carries a signature of the dark matter, dark energy, and gravity that shaped it. PAIRS reads that signature where it's hardest to model: on small scales, inside voids, walls, filaments and nodes.
Cosmologist leading the project, with expertise in theoretical modelling, cosmological inference, and the physics of large-scale structure.
Doctor in Astronomy and Physics, National University of Córdoba. Handles large cosmological simulations and the study of the cosmic web in observations and simulations.
Doctoral researcher with a master's in Physics from the University of Copenhagen. Connects theory and simulations, extending analytical templates toward more realistic scenarios.
Marie Skłodowska-Curie Fellow in the Astrophysics Research Group at the University of Surrey, working on dwarf galaxies, dark matter substructure, and the galaxy–environment connection.
Peculiar motions — the streaming of galaxies toward denser regions — encode information that static positions alone can't give up. PAIRS turns the relative motion of galaxy pairs into an independent test of the cosmological model.
Visualisation idea by Dr. Antonela Taverna, implementation by Dr. Oliver Newton.
Five steps carry the project from a revised equation of motion to numbers that survey teams can use.
Revisit the theoretical equation describing how pairs of galaxies fall toward each other, allowing for non-conservative effects.
Use large, state-of-the-art cosmological simulations — TNG, Quijote, and Bolshoi — to track the motions of dark matter, haloes, and galaxies under controlled conditions.
Segment those simulations into environments — voids, walls, filaments, nodes — using advanced topology-based algorithms.
Build and test enhanced galaxy-bias models by fitting analytical predictions to simulation measurements, across environments and scales.
Translate the new velocity-based statistics into cosmological parameter constraints, and forecast their reach for current and future galaxy surveys.
From theoretical foundations and data preparation, through measurement and model-building, to cosmological constraints the field can use.
Theory revision and the preparation of simulation data.
Cosmic-web segmentation and small-scale bias-model building.
Cosmological parameter estimation and forecasts for surveys.
PAIRS builds on Mariana Jaber's ongoing work on pairwise velocities, beyond-ΛCDM models, the galaxy–environment connection, and galaxy redshift surveys.
Modelling the mean pairwise peculiar velocity of galaxies down to sub-megaparsec scales, and applying it to data to extract cosmological information inaccessible to standard clustering or lensing analyses.
Parameterizations and numerical tools spanning dynamical dark energy, modified gravity, and alternative dark matter, tested against survey data and simulations.
How a galaxy's size, stellar mass, star-formation rate, and metallicity vary with its place in the cosmic web — from voids to filaments and clusters.
An Alcock–Paczyński test on the eBOSS Luminous Red Galaxy sample, comparing clustering along and across the line of sight to constrain the geometry of the Universe.
The project will deliver new theoretical templates, curated simulation catalogues, improved small-scale bias models, and public cosmological constraints and forecasts.
This project is funded by the National Science Center of Poland under the SONATA-19 call, project number 2023/51/D/ST9/02919.
We acknowledge the Polish high-performance computing infrastructure PLGrid for awarding this project access to the TRYTON supercomputer via grants PLG/2024/017481, PLG/2025/019011, and PLG/2026/019226.