{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/qzo-a-catalog-of-5-million-quasars-from-the","title":"QZO: A Catalog of 5 Million Quasars from the Zwicky Transient Facility","arxiv_id":"2502.13054","date":"2025-02-18","proceeding":null,"authors":["S. J. Nakoneczny","M. J. Graham","D. Stern","G. Helou","S. G. Djorgovski","E. C. Bellm","T. X. Chen","R. Dekany","A. Drake","A. A. Mahabal","T. A. Prince","R. Riddle","B. Rusholme","N. Sravan"],"abstract":"Machine learning methods are well established in the classification of quasars (QSOs). However, the advent of light curve observations adds a great amount of complexity to the problem. Our goal is to use the Zwicky Transient Facility (ZTF) to create a catalog of QSOs. We process the ZTF DR20 light curves with a transformer artificial neural network and combine different surveys with extreme gradient boosting. Based on ZTF g-band and WISE observations, we find 4,849,574 objects classified as QSOs with confidence higher than 90%. We robustly classify objects fainter than the $5\\sigma$ SNR limit at $g=20.8$ by requiring $g < n_\\mathrm{obs} / 80 + 20.375$. For 33% of QZO objects, with available WISE data, we publish redshifts with estimated error $\\Delta z/(1 + z) = 0.14$. We find that ZTF classification is superior to the Pan-STARRS static bands, and on par with WISE and Gaia measurements, but the light curves provide the most important features for QSO classification in the ZTF dataset. Using ZTF g-band data with at least 100 observational epochs per light curve, we obtain 97% F1 score for QSOs. We find that with 3 day median cadence, a survey time span of at least 900 days is required to achieve 90% QSO F1 score. However, one can obtain the same score with a survey time span of 1800 days and the median cadence prolonged to 12 days.","url_abs":"https://arxiv.org/abs/2502.13054v1","url_pdf":"https://arxiv.org/pdf/2502.13054v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"qzo-a-catalog-of-5-million-quasars-from-the","repo_url":"https://github.com/snakoneczny/ztf-agn","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}