Catalog of Galaxies and Clusters of Galaxies

The Catalog of Galaxies and Clusters of Galaxies (aka Zwicky Catalog, and abbreviated CGCG or sometimes ZC) is a list (in eight volumes, I to VIII) published by Fritz Zwicky beginning in 1961, that totals more than 29000 galaxies and 9000 galaxy clusters identified in the Palomar Observatory Sky Survey (POSS) plates. (The designators used for the catalog's galaxies were atypical: they began with the volume number, e.g., "II Zw example II Zw 96" for the 96th galaxy in volume II: these are now often reversed, i.e., "Zw II 96", or "CGCG" is used with coordinates.) Since publication, the catalog has been updated with corrections and it remains in use for research, such as selecting samples for study. The Updated Zwicky Catalog (UZC) is a 1990s update, using newer observations to correct data and add precision.

The Catalogue of Selected Compact Galaxies and of Post-eruptive Galaxies (CGPG) is Zwicky's 1971 list of compact galaxies (smaller than typically-observed galaxies), and post-eruptive galaxies (Zwicky's term for galaxies with atypical spectral energy distributions and/or morphology, which perhaps included what is now known to be characteristics of active galactic nuclei, AGNs, but I can't tell). Zwicky selected many of these from his CGCG, cross-referencing them with the CGCG designators, which are often used to refer to this catalog's entries.