Baryon Conversion Efficiency by Cosmic-Web Environment: Where Stars Formed from the Available Gas

The efficiency with which baryons became stars varies systematically across the cosmic web, and the variation can be computed from two distribution tables: where the mass is, and where the stars are. This paper combines stated shares — mass shares of 0.13, 0.24, 0.42 and 0.21 for voids, walls, filaments and nodes, and stellar-mass shares of 0.06, 0.22, 0.48 and 0.24 for the same components — with a global stellar share of 0.07 of all baryons. The stellar fraction of the baryons resident in each environment follows: 0.03231 in voids, 0.06417 in walls, 0.08 in filaments, and 0.08 in nodes. Nodes and filaments convert their baryons to stars at equal efficiency in this accounting, about 2.48 times the void efficiency, while filaments exceed the global mean by a factor of only 1.14. The complement is equally informative: a fraction 0.92 of filament baryons never became stars and remains in the diffuse phases the census measures. Environment modulates star formation efficiency by factors of a few, not orders of magnitude — because the stellar distribution tracks the mass distribution closely, and the web's main effect is to decide where the mass is.