Paper detail

Looking at the relation between haloes and galaxies under the lens

We use an empirical approach to model the stellar mass of galaxies according to their host dark-matter haloes and subhaloes ('HASH'), where each galaxy resides in a subhalo taken from a large N-body cosmological simulation. This approach allows us to study the mass relation between subhaloes and galaxies (MR) using: the weak lensing signal (WL), the two point auto-correlation function (CF), and the stellar mass function of galaxies (SMF). Our method is based on modeling the lensing signal directly from the cosmological simulation, and should thus be more accurate than other methods based on analytic halo models. We find that the WL does not provide a strong constraint on the MR, allowing for more than a factor of 10 freedom in the subhalo mass of central galaxies, for a given stellar mass. The freedom for satellite galaxies is much larger, providing a very poor constraint on the fraction of satellite galaxies (0.05-0.8). These results are not significantly modified when using both the SMF and WL as constraints. We show that for the most massive galaxies, observational constraints based on the CF with 0.1 dex errors, are equivalent to 0.05 dex error in the WL. For intermediate and low mass galaxies the WL and CF constrain the MR in a different way. Although the WL is currently not adding much information at these masses, it has the potential of being important using future, more accurate measurements. The models found here do not match simultaneously the observed CF and WL signals, and show a limited ability to match the WL & SMF. We suspect that this is partially due to the cosmological model assumed here and we therefore adopt a mock WL signal through most of this work. In comparison to previous models in the literature, the method presented here is probably more general, as it reveals a larger range of solutions for a given set of observational constraints [abridged].