{"record_type":"pith_number_record","schema_url":"https://pith.science/schemas/pith-number/v1.json","pith_number":"pith:2004:2ZV3NAWBLRR7KKHOVVEQ73TG2Y","short_pith_number":"pith:2ZV3NAWB","schema_version":"1.0","canonical_sha256":"d66bb682c15c63f528eead490fee66d600be55ab980b6f08cc793d95e040b7fc","source":{"kind":"arxiv","id":"astro-ph/0408578","version":1},"attestation_state":"computed","paper":{"title":"Spectral Classification of Quasars in the Sloan Digital Sky Survey: Eigenspectra; Redshift and Luminosity Effects","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"A. J. Connolly, A. M. Hopkins, A. S. Szalay, C. W. Yip, D. E. Vanden Berk, D. P. Schneider, G. T. Richards, J. A. Frieman, J. Brinkmann, J. Trump, M. Subbarao, P. B. Hall, Z. Ma","submitted_at":"2004-08-31T12:52:24Z","abstract_excerpt":"We study 16,707 quasar spectra from the SDSS using the Karhunen-Lo\\`eve (KL) transform (or Principal Component Analysis, PCA). The quasar eigenspectra of the full catalog reveal the following: 1st order - the mean spectrum; 2nd order - a host-galaxy component; 3rd order - the UV-optical continuum slope; 4th order - the correlations of Balmer emission lines. We find that the spectral classification of quasars is redshift and luminosity dependent, as such there does not exist a compact set (< 10 modes) of eigenspectra (covering 900 to 8000 angstrom) which can describe most variations (> 95%) of "},"verification_status":{"content_addressed":true,"pith_receipt":true,"author_attested":false,"weak_author_claims":0,"strong_author_claims":0,"externally_anchored":false,"storage_verified":false,"citation_signatures":0,"replication_records":0,"graph_snapshot":true,"references_resolved":false,"formal_links_present":false},"canonical_record":{"source":{"id":"astro-ph/0408578","kind":"arxiv","version":1},"metadata":{"license":"","primary_cat":"astro-ph","submitted_at":"2004-08-31T12:52:24Z","cross_cats_sorted":[],"title_canon_sha256":"9fc555f2ff0d5bebea20428de3e1cb9e46592f2f2cac90b596dc2b6b029ab2a1","abstract_canon_sha256":"03e5ff00ae6559a74c17580a80a5111101bff086c46a7f13a7907216638a3e43"},"schema_version":"1.0"},"receipt":{"kind":"pith_receipt","key_id":"pith-v1-2026-05","algorithm":"ed25519","signed_at":"2026-07-04T15:48:11.849224Z","signature_b64":"Uptf2ERe+SG1OWLkNbcmd3w5NlbKhqpZyjD8SJgRZH8E7JLTVbMYAZ9e1acv7CasAItAxdOaUREgojVa8gX+BA==","signed_message":"canonical_sha256_bytes","builder_version":"pith-number-builder-2026-05-17-v1","receipt_version":"0.3","canonical_sha256":"d66bb682c15c63f528eead490fee66d600be55ab980b6f08cc793d95e040b7fc","last_reissued_at":"2026-07-04T15:48:11.848827Z","signature_status":"signed_v1","first_computed_at":"2026-07-04T15:48:11.848827Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54"},"graph_snapshot":{"paper":{"title":"Spectral Classification of Quasars in the Sloan Digital Sky Survey: Eigenspectra; Redshift and Luminosity Effects","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"A. J. Connolly, A. M. Hopkins, A. S. Szalay, C. W. Yip, D. E. Vanden Berk, D. P. Schneider, G. T. Richards, J. A. Frieman, J. Brinkmann, J. Trump, M. Subbarao, P. B. Hall, Z. Ma","submitted_at":"2004-08-31T12:52:24Z","abstract_excerpt":"We study 16,707 quasar spectra from the SDSS using the Karhunen-Lo\\`eve (KL) transform (or Principal Component Analysis, PCA). The quasar eigenspectra of the full catalog reveal the following: 1st order - the mean spectrum; 2nd order - a host-galaxy component; 3rd order - the UV-optical continuum slope; 4th order - the correlations of Balmer emission lines. We find that the spectral classification of quasars is redshift and luminosity dependent, as such there does not exist a compact set (< 10 modes) of eigenspectra (covering 900 to 8000 angstrom) which can describe most variations (> 95%) of "},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0408578","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/astro-ph/0408578/integrity.json","findings":[],"available":true,"detectors_run":[],"snapshot_sha256":"c28c3603d3b5d939e8dc4c7e95fa8dfce3d595e45f758748cecf8e644a296938"},"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"},"aliases":[{"alias_kind":"arxiv","alias_value":"astro-ph/0408578","created_at":"2026-07-04T15:48:11.848889+00:00"},{"alias_kind":"arxiv_version","alias_value":"astro-ph/0408578v1","created_at":"2026-07-04T15:48:11.848889+00:00"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.astro-ph/0408578","created_at":"2026-07-04T15:48:11.848889+00:00"},{"alias_kind":"pith_short_12","alias_value":"2ZV3NAWBLRR7","created_at":"2026-07-04T15:48:11.848889+00:00"},{"alias_kind":"pith_short_16","alias_value":"2ZV3NAWBLRR7KKHO","created_at":"2026-07-04T15:48:11.848889+00:00"},{"alias_kind":"pith_short_8","alias_value":"2ZV3NAWB","created_at":"2026-07-04T15:48:11.848889+00:00"}],"events":[],"event_summary":{},"paper_claims":[],"inbound_citations":{"count":0,"internal_anchor_count":0,"sample":[]},"formal_canon":{"evidence_count":0,"sample":[],"anchors":[]},"links":{"html":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y","json":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y.json","graph_json":"https://pith.science/api/pith-number/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/graph.json","events_json":"https://pith.science/api/pith-number/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/events.json","paper":"https://pith.science/paper/2ZV3NAWB"},"agent_actions":{"view_html":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y","download_json":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y.json","view_paper":"https://pith.science/paper/2ZV3NAWB","resolve_alias":"https://pith.science/api/pith-number/resolve?arxiv=astro-ph/0408578&json=true","fetch_graph":"https://pith.science/api/pith-number/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/graph.json","fetch_events":"https://pith.science/api/pith-number/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/events.json","actions":{"anchor_timestamp":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/action/timestamp_anchor","attest_storage":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/action/storage_attestation","attest_author":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/action/author_attestation","sign_citation":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/action/citation_signature","submit_replication":"https://pith.science/pith/2ZV3NAWBLRR7KKHOVVEQ73TG2Y/action/replication_record"}},"created_at":"2026-07-04T15:48:11.848889+00:00","updated_at":"2026-07-04T15:48:11.848889+00:00"}