{"paper":{"title":"Formaldehyde Silhouettes Against the Cosmic Microwave Background: A Mass-Limited, Distance-Independent, Extinction-Free Tracer of Star Formation Across the Epoch of Galaxy Evolution","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.CO","authors_text":"Benjamin Zeiger, Jeremy Darling","submitted_at":"2012-03-31T22:52:13Z","abstract_excerpt":"We examine the absorption of cosmic microwave background (CMB) photons by formaldehyde (H2CO) over cosmic time. The K-doublet rotational transitions of H2CO become \"refrigerated\" - their excitation temperatures are driven below the CMB temperature - via collisional pumping by molecular hydrogen (H2). \"Anti-inverted\" H2CO line ratios thus provide an accurate measurement of the H2 density in molecular clouds. Using a radiative transfer model, we demonstrate that H2CO centimeter wavelength line excitation and detectability are nearly independent of redshift or gas kinetic temperature. Since the H"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1204.0145","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":""},"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"}