Rosseland and Planck mean opacities for primordial matter

We present newly calculated low-temperature opacities for gas with a primordial chemical composition. In contrast to earlier calculations, which took a pure metal-free hydrogen/helium mixture, we take into account the small fractions of deuterium and lithium as resulting from standard big bang nucleosynthesis. Our opacity tables cover the density range −16 < logρ[g cm−3] < −2 and the temperature range of 1.8 < logT[K] < 4.6, while previous tables have usually been restricted to T > 103 K. We find that, while the presence of deuterium does not significantly alter the opacity values, the presence of lithium gives rise to major modifications of the opacities, at some points increasing it by approximately two orders of magnitude relative to pure hydrogen/helium opacities.