Diffuse Light Inside Halos: How Much Background Could Intrahalo Stars Supply?

This paper addresses a specific question in the accounting of the cosmic optical and infrared backgrounds: what intensity of diffuse background light follows if a stated fraction of the stellar light in galaxy halos is unbound, and what fraction would be needed to supply a given unexplained residual? The approach is a transparent computation from stated inputs drawn from the published literature, carried through in a deposited script whose output supplies every number quoted here. The principal computed values are: I diffuse f0.10 nW = 0.878; I diffuse f0.20 nW = 1.98; I diffuse f0.30 nW = 3.39; f needed for residual 5.56nW = 0.413. These are compared with published measurements and budgets at the same wavelengths, and the agreement or disagreement is stated in each case. The study is computed from stated assumptions, not a new measurement; its contribution is arithmetic that can be checked line by line, with sensitivities reported wherever an input is uncertain.