{"paper":{"title":"A Principal Components Analysis of the Lick Indices of Galactic Globular Clusters","license":"","headline":"","cross_cats":[],"primary_cat":"astro-ph","authors_text":"Jay Strader, Jean P. Brodie (UCO/Lick Observatory)","submitted_at":"2004-06-30T20:18:10Z","abstract_excerpt":"We present a principal components analysis (PCA) of high-quality Lick/IDS absorption-line measurements for 11 indices in the wavelength range 4100-5400 Ang for 39 Galactic globular clusters (GCs). Only the first principal component appears to be physically significant. We find that there is a tight linear relationship between this first component (PC1) and GC metallicity over a wide range in [m/H] (-1.8 <= [m/H] <= 0), suggesting that PC1 may be used to accurately estimate metallicities for old extragalactic GCs from their integrated spectra. The classic GC ``second parameter effect'' is notic"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"astro-ph/0407001","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/0407001/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"}