pop-cosmos : Redshifts and physical properties of KiDS-1000 galaxies
Abstract Principled Bayesian inference of galaxy properties has not previously been performed for wide-area weak lensing surveys with millions of sources. We address this gap by applying the pop-cosmos generative model to perform spectral energy distribution (SED) fitting for 4 million KiDS-1000 galaxies. Calibrated on deep COSMOS2020 photometric data, pop-cosmos specifies a physically-motivated prior over the galaxy population up to z ≃ 6 in stellar population synthesis (SPS) parameter space. Using the Speculator SPS emulator with GPU-accelerated MCMC sampling, we perform full posterior inference at 8.2 GPU seconds per galaxy, obtaining joint constraints on galaxy redshifts and physical properties. We validate photometric redshifts against ~185, 000 KiDS galaxies cross-matched to DESI DR1 spectroscopic samples, achieving low bias (2 × 10−3), scatter (σMAD = 0.03), and outlier fraction (3.2%) for the Bright Galaxy Survey, with comparable performance (bias 3 × 10−2, σMAD = 0.05, 1.0% outliers) for luminous red galaxies (LRGs). Within the LRG sample, we identify massive, dusty, star-forming contaminants at z ≃ 0.4 satisfying standard colour selections for quenched populations. We infer trends in stellar mass, star formation, metallicity, and dust across five tomographic redshift bins consistent with established scaling relations. Using specific star formation rate constraints, we identify ~7% of KiDS-1000 galaxies as quenched, versus 37% implied by conservative colour cuts. This enables the construction of weak lensing samples defined by physical properties while mitigating intrinsic alignment systematics and preserving statistical power. Our analysis validates pop-cosmos out-of-sample, establishing it as a scalable approach for galaxy evolution and cosmological analyses with photometric surveys.
Authors
- Hiranya V. Peiris (ORCID: https://orcid.org/0000-0002-2519-584X)
- Madalina N. Tudorache (ORCID: https://orcid.org/0000-0002-7288-6627)
- Angus H. Wright (ORCID: https://orcid.org/0000-0001-7363-7932)
- Stephen Thorp (ORCID: https://orcid.org/0009-0005-6323-0457)
- Sinan Deger (ORCID: https://orcid.org/0000-0003-1943-723X)
- Joel Leja (ORCID: https://orcid.org/0000-0001-6755-1315)
- Anik Halder (ORCID: https://orcid.org/0000-0002-0352-9351)
- D. Mortlock (ORCID: https://orcid.org/0000-0002-0041-3783)
- Gurjeet Jagwani (ORCID: https://orcid.org/0009-0004-7935-2785)
- Benedict Van den Bussche
- Boris Leistedt
Institutions
- Pennsylvania State University (US)
- Stockholm University (SE)
- University of Cambridge (GB)
- Bridge University (SS)
- Jesus University (KR)
- Institute of Astronomy (RU)
- AlbaNova (SE)
- Astronomical Institute of the Slovak Academy of Sciences (SK)
- Imperial College London (GB)
- Ruhr University Bochum (DE)
Publication Details
- Journal
- Monthly Notices of the Royal Astronomical Society
- Published
- 2026-08-20
- DOI
- https://doi.org/10.1093/mnras/stag1590
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Gordon and Betty Moore Foundation
- University of California
- California Institute of Technology
- Dell EMC
- Government of the United Kingdom
- UK Research and Innovation
- Göran Gustafssons Stiftelser
- European Commission
- University of Bristol
- Deutsche Forschungsgemeinschaft
- Chinese Academy of Sciences
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek
- Università degli Studi di Padova
- Knut och Alice Wallenbergs Stiftelse
- Ministerio de Ciencia e Innovación
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives
- Office of Science
- Jet Propulsion Laboratory
- Engineering and Physical Sciences Research Council
- Science and Technology Facilities Council
- Division of Astronomical Sciences
- High Energy Physics
- Lawrence Berkeley National Laboratory