{"state_type":"pith_open_graph_state","state_version":"1.0","pith_number":"pith:2000:NB6BUKGFFLNI3JJZSHUBHHBLCL","merge_version":"pith-open-graph-merge-v1","event_count":2,"valid_event_count":2,"invalid_event_count":0,"equivocation_count":0,"current":{"canonical_record":{"metadata":{"abstract_canon_sha256":"1449d7d0e9c11d13335266f963d053c8842b1198e7352a5c9cf142e72b52f554","cross_cats_sorted":[],"license":"","primary_cat":"astro-ph","submitted_at":"2000-02-15T07:47:42Z","title_canon_sha256":"2140043f5e9b0f62a41d8d1dd255c31b0e8867294de0e93c9af1a93a30fff709"},"schema_version":"1.0","source":{"id":"astro-ph/0002297","kind":"arxiv","version":1}},"source_aliases":[{"alias_kind":"arxiv","alias_value":"astro-ph/0002297","created_at":"2026-05-18T04:21:42Z"},{"alias_kind":"arxiv_version","alias_value":"astro-ph/0002297v1","created_at":"2026-05-18T04:21:42Z"},{"alias_kind":"doi","alias_value":"10.48550/arxiv.astro-ph/0002297","created_at":"2026-05-18T04:21:42Z"},{"alias_kind":"pith_short_12","alias_value":"NB6BUKGFFLNI","created_at":"2026-05-18T12:25:50Z"},{"alias_kind":"pith_short_16","alias_value":"NB6BUKGFFLNI3JJZ","created_at":"2026-05-18T12:25:50Z"},{"alias_kind":"pith_short_8","alias_value":"NB6BUKGF","created_at":"2026-05-18T12:25:50Z"}],"graph_snapshots":[{"event_id":"sha256:7e2f44da1648abdfb9e582618031d40b17061a1abed3e6a94f16fb48c0458928","target":"graph","created_at":"2026-05-18T04:21:42Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"graph_snapshot":{"author_claims":{"count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","strong_count":0},"builder_version":"pith-number-builder-2026-05-17-v1","claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"paper":{"abstract_excerpt":"Since radio sources with Ultra Steep Spectra (USS; alpha <~ -1.30; S ~ nu^alpha) are efficient tracers of high redshift radio galaxies (HzRGs), we have defined three samples of such USS sources using the recently completed WENSS, TEXAS, MRC, NVSS and PMN radio-surveys. Our combined sample contains 669 sources with S_1400 > 10 mJy and covers virtually the entire sky outside the Galactic plane (|b|>15). For our 2 largest samples, covering declination > -35, we selected only sources with angular sizes Theta < 1'. For 410 sources, we present radio-maps with 0.3\" to ~5\" resolution from VLA and ATCA","authors_text":"Carlos De Breuck (Leiden & IGPP/LLNL), Huub Rottgering & George Miley (Leiden), Wil van Breugel (IGPP/LLNL)","cross_cats":[],"headline":"","license":"","primary_cat":"astro-ph","submitted_at":"2000-02-15T07:47:42Z","title":"A Sample of 669 Ultra Steep Spectrum Radio Sources to Find High Redshift Radio Galaxies"},"references":{"count":0,"internal_anchors":0,"resolved_work":0,"sample":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0002297","kind":"arxiv","version":1},"verdict":{"created_at":null,"id":null,"model_set":{},"one_line_summary":"","pipeline_version":null,"pith_extraction_headline":"","strongest_claim":"","weakest_assumption":""}},"verdict_id":null}}],"author_attestations":[],"timestamp_anchors":[],"storage_attestations":[],"citation_signatures":[],"replication_records":[],"corrections":[],"mirror_hints":[],"record_created":{"event_id":"sha256:16e4664abca1113f7026e280ba10388fc942e6b7d354c5a163c75f3867c702fa","target":"record","created_at":"2026-05-18T04:21:42Z","signer":{"key_id":"pith-v1-2026-05","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","signer_id":"pith.science","signer_type":"pith_registry"},"payload":{"attestation_state":"computed","canonical_record":{"metadata":{"abstract_canon_sha256":"1449d7d0e9c11d13335266f963d053c8842b1198e7352a5c9cf142e72b52f554","cross_cats_sorted":[],"license":"","primary_cat":"astro-ph","submitted_at":"2000-02-15T07:47:42Z","title_canon_sha256":"2140043f5e9b0f62a41d8d1dd255c31b0e8867294de0e93c9af1a93a30fff709"},"schema_version":"1.0","source":{"id":"astro-ph/0002297","kind":"arxiv","version":1}},"canonical_sha256":"687c1a28c52ada8da53991e8139c2b12e7e97a0dbe3d33b9c707055333e27bca","receipt":{"algorithm":"ed25519","builder_version":"pith-number-builder-2026-05-17-v1","canonical_sha256":"687c1a28c52ada8da53991e8139c2b12e7e97a0dbe3d33b9c707055333e27bca","first_computed_at":"2026-05-18T04:21:42.754364Z","key_id":"pith-v1-2026-05","kind":"pith_receipt","last_reissued_at":"2026-05-18T04:21:42.754364Z","public_key_fingerprint":"8d4b5ee74e4693bcd1df2446408b0d54","receipt_version":"0.3","signature_b64":"LU6WrEcah/3kJbmCVpIbT7OzxvEEfyk+ZItOa9OpueGLDQtQ2q429Fk5ofg+OdBp7GIr6vGzg1y2TzxdFzoYDQ==","signature_status":"signed_v1","signed_at":"2026-05-18T04:21:42.755213Z","signed_message":"canonical_sha256_bytes"},"source_id":"astro-ph/0002297","source_kind":"arxiv","source_version":1}}},"equivocations":[],"invalid_events":[],"applied_event_ids":["sha256:16e4664abca1113f7026e280ba10388fc942e6b7d354c5a163c75f3867c702fa","sha256:7e2f44da1648abdfb9e582618031d40b17061a1abed3e6a94f16fb48c0458928"],"state_sha256":"afbe6cf0d615b2b543b0fc34461d1b813f607a5bb623f0cf8fb6df0c9e9e027a"}