{"paper":{"title":"Hamilton's Object Revisited: A challenging source redshift of a strong lensing configuration","license":"http://creativecommons.org/licenses/by-nc-nd/4.0/","headline":"Re-analysis of spectra confirms Hamilton's object has redshift 0.82 rather than 3.2","cross_cats":["astro-ph.CO"],"primary_cat":"astro-ph.GA","authors_text":"Emilio E. Falco, Jenny Wagner, Richard E. Griffiths","submitted_at":"2026-04-21T18:00:01Z","abstract_excerpt":"Low-resolution spectrographs used to have difficulties to determine redshifts of galaxies at $z\\approx1$ and $z\\approx3$. Spectral emission and absorption lines of magnesium and iron redshifted to $z\\approx1$ fall close to hydrogen, silicon, and oxygen lines at $z\\approx3$. Here, we demonstrate that, even with modern, integrated field unit spectrographs, this task remains challenging. Hamilton's object, a blue star-forming galaxy, gravitationally lensed into three multiple images by the galaxy cluster SDSS J223010.47-081017.8 is such a case. Using the Blue Keck Cosmic Web Imager, its redshift "},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The re-evaluation confirms the previous result based on 6 absorption features, z=0.820 ± 0.001 and 4 emission features, z=0.821 ± 0.002. The alternative z=3.199± 0.003, based on 6 absorption and 2 emission lines is a worse fit, also compared to other spectra.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"That the chosen line identifications at z=0.82 are the correct physical assignment and that the PypeIt pipeline plus custom Python fitting routines introduce no systematic wavelength or flux errors that would alter the relative goodness-of-fit between the two redshift solutions.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Re-analysis of KCWI spectra with PypeIt confirms Hamilton's object redshift at z=0.820, showing the MOIRCS z=3.2 fit is worse and the earlier data inconclusive due to slit coverage and calibration issues.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Re-analysis of spectra confirms Hamilton's object has redshift 0.82 rather than 3.2","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"81b625203c703c1590f4e465e6cf4f0e18be29efdf8b32eb1ce45736491bc81f"},"source":{"id":"2604.19867","kind":"arxiv","version":1},"verdict":{"id":"db0aa6d4-8692-4ac2-8382-aba62d3b98c0","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-10T01:50:37.275662Z","strongest_claim":"The re-evaluation confirms the previous result based on 6 absorption features, z=0.820 ± 0.001 and 4 emission features, z=0.821 ± 0.002. The alternative z=3.199± 0.003, based on 6 absorption and 2 emission lines is a worse fit, also compared to other spectra.","one_line_summary":"Re-analysis of KCWI spectra with PypeIt confirms Hamilton's object redshift at z=0.820, showing the MOIRCS z=3.2 fit is worse and the earlier data inconclusive due to slit coverage and calibration issues.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"That the chosen line identifications at z=0.82 are the correct physical assignment and that the PypeIt pipeline plus custom Python fitting routines introduce no systematic wavelength or flux errors that would alter the relative goodness-of-fit between the two redshift solutions.","pith_extraction_headline":"Re-analysis of spectra confirms Hamilton's object has redshift 0.82 rather than 3.2"},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2604.19867/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"ai_meta_artifact","ran_at":"2026-05-21T15:42:29.235025Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"doi_compliance","ran_at":"2026-05-20T02:34:27.545494Z","status":"completed","version":"1.0.0","findings_count":0}],"snapshot_sha256":"077049a3e2fd589e13568ee03887f91c19161cb4cb3e1a3758a5405c75528de9"},"references":{"count":40,"sample":[{"doi":"","year":2011,"title":"Bayliss, M. B., Hennawi, J. F., Gladders, M. D., et al. 2011, ApJS, 193, 8","work_id":"1b72dd4d-468b-4e40-8d40-3c7f5c17c8cf","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2017,"title":"B., Grillo, C., Rosati, P., et al","work_id":"d3c62ee2-211d-4040-87e8-6f309ceaa4b0","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2025,"title":"2025, MNRAS, 537, 2662","work_id":"6ec82412-da27-4eee-b5cc-056b78e143d9","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2018,"title":"2018, A&A, 617, A62","work_id":"4c8f6400-09be-4175-9b6b-4fd12c8c912c","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2021,"title":"E., Rudisel, M., Wagner, J., et al","work_id":"920577b7-78e0-4641-b0d1-0415119dd686","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":40,"snapshot_sha256":"12f17d4baa600d4ddc59fba236daef873510b82878af30704afb63efbfa55e76","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}