e use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely stellar colour, specific star formation rate, Sérsic index, and effective... Show moree use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely stellar colour, specific star formation rate, Sérsic index, and effective radius) for a volume-limited sample of GAMA galaxies in a narrow stellar mass range [M* ∼ (2–5) × 1010 M⊙]. This mass range is particularly interesting, inasmuch as it is where bimodalities in galaxy properties are most pronounced, and near to the break in both the galaxy stellar mass function and the stellar-to-halo mass relation (SHMR). In this narrow mass range, we find that both size and Sérsic index are better predictors of halo mass than either colour or SSFR, with the data showing a slight preference for Sérsic index. In other words, we find that mean halo mass is more tightly correlated with galaxy structure than either past star formation history or current star formation rate. Our results lead to an approximate lower bound on the dispersion in halo masses among log M* ≈ 10.5 galaxies: We find that the dispersion is ≳0.3 dex. This would imply either that offsets from the mean SHMR are closely coupled to size/structure or that the dispersion in the SHMR is larger than what past results have suggested. Our results thus provide new empirical constraints on the relationship between stellar and halo mass assembly at this particularly interesting mass range. Show less
Brouwer, M.M.; Demchenko, V.; Harnois-Déraps, J.; Bilicki, M.A.; Heymans, C.; Hoekstra, H.; ... ; Uitert, E. van 2018
Of all the mass in our Universe, 80% is thought to consist of a hypothetical and invisible substance called dark matter (DM). So far, all observations of DM are based on its gravitational... Show moreOf all the mass in our Universe, 80% is thought to consist of a hypothetical and invisible substance called dark matter (DM). So far, all observations of DM are based on its gravitational interaction, either through the dynamics of normal (baryonic) matter or through the deflection of light. The latter approach, called ‘gravitational lensing’, is a unique way to probe the distribution of DM without making any assumptions on its dynamical state, and on scales larger than the extent of baryons. Using weak gravitational lensing with the Kilo-Degree Survey (KiDS), we first study the relation between galaxies and their dark matter halos on the scale of individual galaxies and galaxy groups. We then attempt to measure the effect of the local and large scale (cosmic web) density distribution on galaxies and halos, and we measure the interplay between galactic and DM structures at the scale of the cosmic web. Finally, we perform the first test of Verlinde’s theory of Emergent Gravity, all with the ultimate goal of gleaning some insight into the possible nature of the elusive ‘missing mass’. Show less
