The metallicity of diffuse intrahalo light

We make predictions for the metallicity of diffuse stellar components in systems ranging from small spiral galaxies to rich galaxy clusters. We extend the formalism of Purcell, Bullock & Zentner, in which diffuse stellar mass is produced via galaxy disruption, and we convolve this result with the observed mass-metallicity relation for galaxies in order to analyse the chemical abundance of intrahalo light (IHL) in host haloes with virial mass 10(10.5) <= M-host <= 10(15) M-circle dot. We predict a steep rise of roughly 2 dex in IHL metallicity from the scales of small to large spiral galaxies. In terms of the total dynamical mass M-host of the host systems under consideration, we predict diffuse light metallicities ranging from Z(IHL) less than or similar to -2.5 for M-host similar to 10(11) M-circle dot to Z(IHL) similar to -1.0 for M-host similar to 10(12) M-circle dot. In larger systems, we predict a more shallow rise in this trend with Z(IHL) similar to -0.4 for M-host similar to 10(13) M-circle dot, increasing to Z(IHL) similar to 0.1 for M-host similar to 10(15) M-circle dot. This behaviour is coincident with a narrowing of the intrahalo metallicity distribution as host mass increases. The observable distinction in surface brightness between old, metal-poor IHL stars and more metal rich, dynamically younger tidal streams is of crucial importance when estimating the chemical abundance of an intrahalo population with multiple origins.