Diffuse Light in Milky-Way like Haloes

We investigate the diffuse light (DL) content of dark matter haloes in the mass range $11.5\leq \log M_{halo}\leq13$, a range that includes also the dark matter halo of the Milky-Way, taking advantage of a state-of-the-art semi-analytic model run on the merger trees extracted from a set of high-resolution cosmological simulations. The fraction of DL in such relatively small haloes is found to progressively decrease from the high to the low mass end, in good agreement with analytic (\citealt{purcell2007}) and numerical results from simulations (\citealt{proctor2023,ahvazi2023}), in good agreement also with the fraction of the DL observed in the Milky-Way (\citealt{deason2019}) and M31 (\citealt{harmsen2017}). Haloes with different masses have a different efficiency in producing DL: $\log M_{halo} \simeq 13$ is found to be the characteristic halo mass where the production of DL is the most efficient, while the overall efficiency decreases at both larger (\citealt{contini2024}) and smaller scales (this work). The DL content in this range of halo mass is the result of stellar stripping due to tidal interaction between satellites and its host (95\%) and mergers between satellites and the central galaxy (5\%), with pre-processed material, sub-channel of mergers and stripping and so already included in the 100\%, that contributes no more than 8\% on average. The halo concentration is the main driver of the DL formation: more concentrated haloes have higher DL fractions that come from stripping of more massive satellites in the high halo mass end, while dwarfs contribute mostly in the low halo mass end.