{"paper":{"title":"Photometric classification of quasars from DES and photo-$z$ estimation with Machine Learning","license":"http://creativecommons.org/licenses/by/4.0/","headline":"","cross_cats":["astro-ph.CO"],"primary_cat":"astro-ph.IM","authors_text":"Camila Cardoso, Elcio Abdalla, Filipe B. Abdalla, Gabriel S. Costa, Pablo Motta","submitted_at":"2026-05-18T11:04:05Z","abstract_excerpt":"This paper presents a comprehensive study of quasar photometric classification and redshift estimation using machine learning techniques. We cross-matched photometric data from the Dark Energy Survey Data Release 2 (DES DR2) with spectroscopic classifications from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16), yielding an initial sample of 168,738 point-like objects. Using a K-Nearest Neighbors (KNN) algorithm with PSF magnitudes in the $g$, $r$, $i$, and $z$ bands, we achieved high-precision quasar/galaxy classification against stellar contaminants, reaching a recall of 0.77 at 0.9"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"2605.18218","kind":"arxiv","version":1},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"integrity":{"clean":true,"summary":{"advisory":0,"critical":0,"by_detector":{},"informational":0},"endpoint":"/pith/2605.18218/integrity.json","findings":[],"available":true,"detectors_run":[{"name":"claim_evidence","ran_at":"2026-05-19T23:41:58.960440Z","status":"completed","version":"1.0.0","findings_count":0},{"name":"ai_meta_artifact","ran_at":"2026-05-19T23:33:35.304293Z","status":"skipped","version":"1.0.0","findings_count":0}],"snapshot_sha256":"f52ba1a1bf20fd3ddcce2b79472fd7b9356d202a8153a5ca7fa26704855bb5f1"},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","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"}