Researchers are now able to map the largest structures in the Universe with unprecedented detail, thanks to a new approach applied to the extensive Quaia quasar catalogue. Adam Andrews from INAF/OAS Bologna, Arthur Loureiro of Stockholm University, and Jens Jasche from the Oskar Klein Centre for Cosmoparticle Physics, alongside colleagues including Stuart McAlpine, Guilhem Lavaux and Florent Leclercq, have used a sophisticated algorithm called BORG to reconstruct the distribution of matter across cosmic time. This work represents the largest ever field-level reconstruction of the observable Universe, spanning a comoving volume of (10h⁻¹ Gpc)³, and is significant because it allows scientists to test cosmological models and our understanding of the Universe’s evolution with greater precision, validated by a ~4σ detection in cross-correlation with Planck CMB lensing data.
This breakthrough was enabled by applying the field-level inference algorithm BORG to the recently released Quaia quasar catalogue, a dataset notable for its broad redshift range and all-sky coverage.
The research presents detailed reconstructions of both the initial conditions and the present-day matter distribution of the Universe, offering unprecedented insights into cosmic evolution. This work employs a physics-based forward model of large-scale structure, utilising Lagrangian perturbation theory to account for complex effects such as light-cone effects, redshift-space distortions, quasar bias, and survey selection effects.
By directly modelling the observed quasar field, researchers circumvent limitations of traditional data compression techniques, extracting a more complete signal from the data. Analyses were performed on both the Quaia Clean (G The resulting reconstructions not only deliver high-fidelity data products, including posterior maps of initial conditions, present-day dark matter, and velocity fields, but also validate their findings through rigorous internal and external consistency checks.
Notably, a cross-correlation with Planck CMB lensing data revealed a significant signal at approximately 4σ significance, bolstering confidence in the reconstruction’s accuracy. This study establishes a powerful framework for exploiting quasar surveys in field-level cosmology, paving the way for future investigations into the Universe’s large-scale structure and its underlying physics.
Reconstructing cosmic structure with BORG and the Quaia quasar catalogue reveals large-scale filamentary patterns
The Quaia quasar catalogue underpinned this work, enabling detailed three-dimensional reconstructions of matter across cosmic time. We implemented the field-level inference algorithm BORG to analyse the Quaia catalogues, reconstructing both initial conditions and the present-day matter distribution of the Universe.
This involved a physics-based forward model of large-scale structure, utilising Lagrangian perturbation theory to account for complex cosmological effects. Specifically, the model incorporated light-cone effects, redshift-space distortions, quasar bias, and survey selection effects to ensure a physically motivated inference of the three-dimensional density field.
Analyses were performed on two samples: the G Validation was conducted through internal and external consistency checks, notably cross-correlating the inferred density fields with Planck CMB lensing data, yielding a detection at ~4σ significance. This research delivers high-fidelity data products, including posterior maps of initial conditions, dark matter distributions, and velocity fields, while establishing a robust framework for utilising quasar surveys in field-level cosmology.
Largest volume reconstruction details data characteristics and methodology used
Reconstructions span a comoving volume of (10h⁻¹ Gpc)³ with a maximum spatial resolution of 39.1 h⁻¹ Mpc, representing the largest field-level reconstruction of the observable Universe to date. Analyses were performed on both the Quaia Clean sample, comprising 755,850 sources with a median redshift of zmed = 1.45, and the Quaia Deep sample, containing 1,295,502 sources with zmed = 1.48.
These catalogues cover a sky area of 29,154.54 deg², corresponding to approximately 0.71 of the entire sky, and extend across a redshift range of 0.084 Within each bin, all quasars share the same bias parameters, sampled sequentially using a slice sampler. This approach maintains a consistent reconstruction across the full radial range while ensuring sufficient statistical power in each subcatalogue.
Redshifts were transformed into the CMB rest frame to remove the imprint of the Sun’s peculiar velocity, which is −360.5226, 76.3969, −45.3542km s⁻¹ in ICRS coordinates. Validation of the reconstructions involved cross-correlation with Planck CMB lensing, yielding a detection at a significance level of ~4σ.
Conservative sky cuts were imposed to ensure robustness against foreground contamination, utilising Gaussian process fits incorporating systematic map templates for Gaia DR3 stellar density, unWISE source distribution, and variations around the Magellanic Clouds. The work delivers high-fidelity data products, including posterior maps of initial conditions, present-day dark matter, and velocity fields, establishing a framework for exploiting quasar surveys in field-level cosmology.
Mapping primordial density fluctuations with quasar-based large-scale structure reconstruction offers a novel probe of the early universe
Researchers have created the largest field-level reconstruction of the observable Universe to date, spanning a comoving volume of (10h⁻¹ Gpc)³ with a maximum spatial resolution of 39.1 h⁻¹ Mpc. This achievement was enabled by applying the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm to data from the recently released Quaia quasar catalogue, which offers broad redshift range and all-sky coverage.
The reconstruction details both the initial conditions and the present-day matter distribution of the Universe, utilising a physics-based forward model incorporating effects like redshift-space distortions and survey selection. This work presents high-fidelity data products, including posterior maps of initial conditions, present-day dark matter, and velocity fields, and establishes a framework for utilising quasar surveys in field-level cosmology.
Validation through cross-correlation with Planck CMB lensing data revealed a signal at approximately 4σ significance, confirming the reliability of the reconstruction. The authors acknowledge that the inherent noise within the quasar sample dominates over potential uncertainties arising from photometric redshift errors, ensuring these errors are subdominant in the analysis. Future research could focus on refining the forward model and exploring higher resolutions to further constrain cosmological parameters and investigate the evolution of large-scale structure.
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👉 More information
🗞 Reconstructing the largest scales of the Universe with field-level inference applied to the Quaia Quasar Catalogue
🧠 ArXiv: https://arxiv.org/abs/2602.02363