{"paper":{"title":"Revisiting the angular size-redshift cosmological test with milliarcsecond radio structures in active galactic nuclei","license":"http://creativecommons.org/licenses/by/4.0/","headline":"VLBI data on compact AGN radio sources shows the angular size-redshift relation is physically real and can constrain Ω_m when scatter is low.","cross_cats":[],"primary_cat":"astro-ph.CO","authors_text":"Alexander B. Pushkarev, Alexander V. Plavin, Andr\\'as Kov\\'acs, Kenneth I. Kellermann, Leonid I. Gurvits, Mina Ghodsi Yengejeh, S\\'andor Frey, Tatiana A. Koryukova","submitted_at":"2026-04-14T16:26:57Z","abstract_excerpt":"VLBI measurements of the sizes of compact extragalactic radio sources, jetted active galactic nuclei, provide data for probing the angular size--redshift relation, offering a complementary test to other distance--redshift methods.\n  We analyse a significantly expanded dataset to reassess the angular size--redshift relation and its potential for constraining cosmological model parameters, focusing on the matter density parameter $\\Omega_{\\mathrm{m}}$ in a flat $\\Lambda$ Cold Dark Matter Universe. This is the first major update of the compact-source angular size test in the past quarter of a cen"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The randomization test showed that the posterior distributions from randomized data do not overlap with those from real observations, confirming that the measured angular size--redshift relation is physically meaningful. Simulated mock catalogues indicate that the method is able to constrain Ω_m if the data scatter is below ∼20%.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"That the astrophysical model parameter describing the redshift dependence of source angular size can be jointly fitted with Ω_m in a way that yields meaningful cosmological constraints despite the noted degeneracy.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"A tenfold larger sample of AGN radio source sizes confirms a real angular size-redshift relation but indicates that scatter must drop below 20% or samples reach thousands to 100,000 to constrain Ω_m effectively.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"VLBI data on compact AGN radio sources shows the angular size-redshift relation is physically real and can constrain Ω_m when scatter is low.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"6f9806a04e5a9591185384e44fa916f8b1e0a27d016df95fb7cb420c65fb4c77"},"source":{"id":"2604.12936","kind":"arxiv","version":1},"verdict":{"id":"aa487727-7cad-409b-b59a-ec38cc4c61fa","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-10T14:21:52.908708Z","strongest_claim":"The randomization test showed that the posterior distributions from randomized data do not overlap with those from real observations, confirming that the measured angular size--redshift relation is physically meaningful. Simulated mock catalogues indicate that the method is able to constrain Ω_m if the data scatter is below ∼20%.","one_line_summary":"A tenfold larger sample of AGN radio source sizes confirms a real angular size-redshift relation but indicates that scatter must drop below 20% or samples reach thousands to 100,000 to constrain Ω_m effectively.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"That the astrophysical model parameter describing the redshift dependence of source angular size can be jointly fitted with Ω_m in a way that yields meaningful cosmological constraints despite the noted degeneracy.","pith_extraction_headline":"VLBI data on compact AGN radio sources shows the angular size-redshift relation is physically real and can constrain Ω_m when scatter is low."},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2604.12936/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"references":{"count":79,"sample":[{"doi":"","year":2012,"title":"An, T. & Baan, W. A. 2012, ApJ, 760, 77","work_id":"5f538cc6-7897-4ec9-853f-1ed137f45016","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2025,"title":"A., & Wang, A","work_id":"ee55de3d-8975-48b2-8f5d-a2cd25528d44","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1968,"title":"Bash, F. N. 1968, ApJS, 16, 373","work_id":"e3ddbedf-f0bb-405f-8781-dd615f5a958e","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2002,"title":"J., Gordon, D., Peck, A","work_id":"90714ef3-8990-45cc-b85b-6edba5a84607","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":1978,"title":"Blandford, R. D. & Rees, M. J. 1978, Phys. 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